Endo Roots Pre-reading

Training course info ENDO ROOTS evolve I elevate I enhance suggested reading

Training course info DAY 1 Diagnosis, treatment planning, endodontic access • Follow a systematic approach to arrive at a correct endodontic diagnosis • Understand how to assess the restorability of a tooth and the tools available to assess endodontic case difficulty • Have a clear understanding of the treatment options for endodontic problems and be able to plan for them appropriately • Gain confidence with rubber dam isolation (hands-on) • Have a deeper understanding of anatomical principles and practical methods of endodontic access and orifice location. Access cavity preparation on 3D printed teeth and delegates own extracted teeth (hands-on) DAY 2 Shaping and cleaning • Understand the challenges we face in shaping and cleaning root canal systems and have knowledge of the solutions available to us • Know why glide path creation is an important principle in biomechanical preparation • Be able to accurately determine working length and gain a greater insight into the use of electronic apex locators and the proper use of such devices (hands-on) • Easy to follow protocols, learning simple and straightforward methods of preparation using Hyflex EDM Rotary and Reciproc Blue Reciprocating instrumentation using 3D printed teeth and delegates’ own patient extracted teeth (hands-on) • Know in which situations single file protocols can be used • Understand the importance of irrigation and learn a safe and effective irrigation protocol DAY 3 Obturation and restoration of the endodontically treated tooth • Be familiar with the objectives of obturation and the challenges it presents • Modern and easy to learn obturation techniques. Bioceramic Sealers and Single Cone Technique (hands-on). Introduction to Continuous Wave of Condensation (hands-on) • Gain insight into the specific challenges of restoring endodontically treated teeth and know how to manage them. A simplified core build up technique (hands-on) • Understand when and how to apply the concept of deep marginal elevation using biomimetic principles • Be able to assess what clinical factors can affect the outcome of endodontic treatment and how predictable our treatment is ENDO ROOTS 3-DAY PROGRAMME [email protected] I evoendo.co.uk

The Dental Practicality Index – assessing the restorability of teeth A. Dawood1,2 and S. Patel*1,3 of, and feedback from dental colleagues with different levels of experience. The decision to retain a (restorable) tooth may well be straightforward, for example, a molar tooth in an intact arch diagnosed with an endodontic problem, with adequate sound coronal tooth structure and periodontal support. However, a tooth with a similar endodontic problem might be considered unrestorable if it had insufficient sound coronal tooth structure to provide an adequate ferrule for a crown. A holistic approach must be taken when considering whether to restore a problematic/ diseased tooth, or to advise the patient that restoration is not practical, and that the tooth may be better left alone or extracted. Not only must the restorative status (endodontic, periodontal and structural integrity) be assessed,1–3 but the patient’s medical and dental condition, as well as their expectations must all be carefully considered in the decision-making process.4,5 Taking these inter-related factors into account can sometimes make treatment planning challenging. Furthermore, treatment decisions and the treatment plan may well depend upon the skillset and experience of the clinician who is managing the patient.5 Appropriate case selection is more likely to result in a successful outcome.6 Guidelines on the treatability of teeth have been published, however, some of these are limited to the assessment of only one aspect Introduction We are living in exciting times in dentistry; advances in materials, techniques, and an extensive array of treatment options allow the dental team to provide effective, predictable, and long-lasting restorative treatments for their patients – even when a tooth is in a highly compromised state. Where a tooth appears to be unsalvageable, replacement with a denture, bridge or dental implant may well be indicated and worthwhile, but only after careful consideration of the long established and well-proven restorative options that are also readily available. Between them, the two authors of this paper are specialists in prosthodontics, periodontics and endodontics. The Dental Practicality Index (DPI) has been developed over the last 19 years in which they have worked together planning, treating and reviewing patients with a simple to complex range of restorative problems in secondary and tertiary care. The index has evolved through the teaching and mentoring The Dental Practicality Index (DPI) has been designed to describe on a clinical level, the ‘practicality’ of dental restorative treatment. Applicable to everyday clinical practice, the DPI also aims to assist the clinician in deciding when to seek advice and/or refer a patient for secondary or tertiary dental care. It is hoped that this tool will aid in the systematic assessment of dental restorative problems, enhance communication between collaborating practitioners and help to manage patient expectations before carrying out restorative treatment(s). (that is, the prosthodontic or periodontal status) of the tooth.7–9 Other guidelines, such as the American Association of Endodontist’s Case Difficulty Assessment guide is used by less than 10% of general dental practitioners in the USA due to being too comprehensive, and therefore time-consuming to complete.10,11 The aim of this paper is to describe a simple, clinician-friendly ‘dental practicality’ (tooth restorability) index, which takes into account each aspect of a tooth’s restorative state. Crucially, it also contextualises the status of the tooth within the dentition as a whole, taking into account the patient’s unique dental needs, expectations, and any relevant medical and dental history. The Dental Practicality Index This index describes the practicality of restorative treatment. Each of the restorative categories; structural integrity, periodontal state and endodontic state are assessed and weighted according to their current state and the complexity of potential treatment. These levels are inevitably somewhat arbitrary and therefore will vary between clinicians depending upon their own unique skillset, experience, and also the facilities that are available to them.12,13 Finally, the context of treatment is considered and scored in relation to local and general factors, including the state of or absence of 1 Dawood & Tanner Specialist Practice, 45 Wimpole Street, London, W1G 8SB; 2 Dept. of Oral and Maxillofacial Surgery, UCLH London, London, UK; 3 Endodontic Postgraduate Unit, King’s College London Dental Institute, London, UK; *Correspondence to: S. Patel Email: [email protected] Refereed Paper. Accepted 21 February 2017 DOI: 10.1038/sj.bdj.2017.447 A new index is described which provides a framework for assessing teeth and planning treatment. Each aspect of the restorative state is assessed along with the local and general context of the tooth/ dentition. Use of the index simplifies and supports planning decisions including tooth retention, suitability of abutment teeth, and the need for referral. In brief BRITISH DENTAL JOURNAL | VOLUME 222 NO. 10 | MAY 26 2017 755 VERIFIABLE CPD PAPER PRACTICE Of fi ci al j o u r n al o f t h e B riti s h D e n t al A s s o ci a ti o n.

nearby teeth, and/or health-related issues which may broadly influence treatment. In all categories a score of ‘0’ means that no intervention is required, ‘1’ means that simple treatment is needed, ‘2’ suggests that treatment is more complex, perhaps requiring treatment delivered by individuals with enhanced skills, training, and experience. A score of ‘6’ in any category means that treatment would not generally be considered to be practical. The overall DPI score is determined by adding together the scores of each of the categories (structural integrity, periodontal status, endodontic status, context). A DPI score >6 indicates that attempting to restore the tooth may not be advisable. A tooth that is stable and healthy in an intact dentition needs no or minimal intervention even if it is extensively restored, successfully treated for periodontal disease and/or has been root treated. The DPI only comes into use when an intervention is required or planned. For example, if there is active secondary caries, periodontal disease, or if there is a plan to use the tooth as a bridge abutment. The DPI may change with initial investigations and stabilisation. Before making a definitive assessment it will often be necessary to carry out initial investigations to establish a baseline condition; for example, it may be necessary to remove an existing restoration to assess the residual sound coronal tooth structure, carry out initial periodontal therapy to assess response, and access a root canal in order to confirm the ability to negotiate to the working length. Structural integrity Level 0 Intact and healthy unrestored coronal tooth structure, or a tooth restored with a welladapted restoration – no treatment required. Level 1 A tooth requiring a simple (in)direct restoration, which may be a replacement restoration, or the first cycle of operative treatment required. Teeth in this category will have adequate volume of sound coronal tooth structure to support the planned restoration. Level 2 Typically, a tooth with minimal sound tooth structure which may require a post-retained foundation, and/or have a sub-gingival margin(s). Such teeth may have been extensively restored in the past. This level would also include situations where the tooth to be restored has a significant role in the occlusion, or is contributing to occlusal problems (for example, extensive non-working side contacts). Level 6 Insufficient tooth structure to allow the tooth to be restored with a well-adapted restoration. An inadequate ferrule, deep subgingival margins and vertical root fractures are examples of factors, which may mean that it is impractical to treat a tooth. Periodontal treatment need Level 0 A periodontal condition; where gingivitis and/or calculus may be present would still score at this level. A BPE score of 0-1 would be unlikely to make restorative treatment impractical. Level 1 Where root surface debridement is necessary; it is envisaged that treatment is well within the scope of a hygienist, therapist, or general practitioner, and may require the use of a local anaesthetic. Typically, there would be probing depths <3.5 mm, poor hygiene and/or presence of calculus are all factors, which may indicate that the situation may be reversed with excellent home care and simple professional treatment. Level 2 Treatment may require non-surgical and/ or surgical intervention. This level would also include cases where restoration margins broadly impinge upon biological width necessitating crown-lengthening surgery. A stable, but limited periodontal support/ clinical attachment would also be included in level 2. This level would include teeth with short roots (unfavourable crown/root ratio), unfavourable root morphology, that is, short conical roots, grade 2–3 furcation involvement, and teeth with or requiring root resection. Level 6 Impractical to treat; typically where there is untreatable or refractory periodontal disease, advanced bone loss and mobility. Endodontic treatment need Level 0 No clinical or radiographic signs of pulpal (for example, deep caries) or periapical (for example, chronic periapical periodontitis) disease. This category would also include a tooth that has already been root treated under rubber dam, and has a well-compacted root filling which terminates within 2 mm of the radiographic apex. Level 1 A primary endodontic treatment is indicated where the clinician is confident he/she can locate the root canal(s), prepare, disinfect and obturate the entire root canal system to the anatomical working length. This level may also include secondary (retreatment) endodontic treatment, typically, poorly compacted and easily retrievable existing root fillings. Level 2 This level of complexity would typically include root canal systems that are challenging to prepare, disinfect and/or obturate. Examples of primary endodontic treatment falling into this category range would include roots with sclerosed canals, canal curvatures >30°, limited internal or external cervical root resorption, and dens in dente teeth. Other examples of complex primary endodontic cases included in this category include vital pulp therapy (eg, regenerative and apexification treatments). Secondary (re-root canal treatment) endodontic cases included in level 2 include fractured instrument removal, perforation repair, and negotiation of a negotiable canal aberration, for example, a ledge or blockage. Management of complex dental trauma, this may include pulp involvement and/or significant displacement of injured teeth. This category would also include surgical endodontics. Level 6 Typically, root canals that are not amenable to predictable disinfection and/or obturation. For example there may be an existing canal aberration or irretrievable fractured instrument where periapical microsurgery may not be possible due to limited access and/or the close proximity of adjacent vital anatomical structures (eg, the inferior dental nerve or maxillary sinus). The tooth may or may not be symptomatic, and/or have signs of chronic periapical periodontitis. The ‘context’ This category relates to the oral environment, the patient’s ability to maintain their dentition (local 756 BRITISH DENTAL JOURNAL | VOLUME 222 NO. 10 | MAY 26 2017 PRACTICE Of fi ci al j o u r n al o f t h e B riti s h D e n t al A s s o ci a ti o n. Of fi ci al j o u r n al o f t h e B riti s h D e n t al A s s o ci a ti o n.

context), and the practicality of restorative treatment in the context of ‘the bigger picture’. A holistic view of the patient, taking into account not only their overall restorative needs, but also the impact of treatment in the wider context of their social, dental, and medical history (general context) must be taken. Level 0 In this level the treatment plan is weighted towards tooth retention. Local context An isolated dental problem where the adjacent teeth are present and healthy. General context Where removal of a strategic tooth is inadvisable, for example, extraction and/or replacement may be excessively complicated, and/or result in an increased likelihood of complications, for example, a patient who has a history of IV bisphosphonate medication, radiotherapy etc. This level includes patients who are fully informed and motivated who wish to retain a tooth despite a guarded medium- to long-term prognosis. Level 1 Local context Limited fixed or removable prosthodontic treatment planned on the immediately adjacent tooth/teeth, which may be modified to include replacement of the tooth being assessed. A tooth being planned to be used as a bridge or denture abutment is weighted 1. General context Medical conditions where the consequences of failure of a complex treatment would be potentially detrimental, for example, endodontic and/or periodontal treatment level 2, where radiotherapy of the area of interest is imminent. Existing medical conditions, or planned treatment, which may have an impact of the outcome of restorative treatment being carried out, for example, severely immunocompromised patients. Level 2 Local context Extensive fixed or removable prosthodontic treatment planned on multiple teeth, including neighbouring teeth. General context A patient with problematic parafunctional habits and/or an extensively worn dentition. A patient with generalised active periodontal disease, or a high caries rate is also considered in this level. Patients who are very anxious and/or need to be sedated would be considered level 2. Significant medical conditions such as a patient who requires immunosuppressive drugs will score 2; not because of restorative concerns but because they may need careful management in a hospital or specialist environment for all but the most straightforward treatments. Table 1 The categories that the tooth should be assessed in; structural integrity, periodontal and endodontic treatment need as well as context are summarised in the grey shaded columns. Each row shows examples of different levels (0,1,2,6) of complexity for each category. An overall DPI score of >6 indicates that treatment may be impractical, this is reduced to 4 if the tooth to be treated is to be used as a bridge abutment Weighting Structure integrity Periodontal treatment need Endodontic treatment need Context 0 No treatment required Unrestored or existing well-adapted restoration Probing <3.5 mm (BPE 0-2) previously successfully treated periodontal disease Vital pulp previously successfully treated endodontic disease Local: Isolated dental problems where adjacent teeth are healthy General: Replacing of a strategic tooth may be excessively complex History of IV bisphosphonates, head & neck radiotherapy 1 Simple treatment required Simple (in)direct restoration Probing 3.5-5.5 mm (BPE 3) root surface debridement indicated Simple root canal system with endodontic disease (eg, radiographically easily identifiable root canal[s], easily retrievable root canal filling material) Local: Prosthodontic treatment planned of neighbouring teeth which may influence treatment plan for tooth being assessed Tooth to be used as a bridge abutment General: Radiotherapy of head and neck region planned Immunocrompromised patient 2 Complex treatment required Minimal residual sound tooth structure (eg subgingival margins, post-core restoration required etc) Probing >5.5 mm (BPE 4) compromised support (eg short root, crown lengthening required, grade 2 mobility). Grade 2-3 furcation involvement Complex root canal system with endodontic disease (eg, sclerosed root canal, acute curvatures. Complex re-root canal treatment (eg, fracture instrument removal, perforations) Difficulty in obtaining anaesthesia Local: Prosthodontic treatment planned of multiple, including adjacent teeth General: High caries rate Poor oral hygiene Parafunctional habits, extensive tooth surface loss Active periodontal disease 6 Impractical to treat Inadequate structure for ferrule Untreatable periodontal disease Untreatable root canal system Local: Retention of the tooth being assessed would constrain and/or compromise an otherwise simple and predicable treatment plan (for example extensive bridge work) General: Potentially life threatening medical conditions which should be managed in tertiary care BRITISH DENTAL JOURNAL | VOLUME 222 NO. 10 | MAY 26 2017 757 PRACTICE Offi ci al j o u r n al o f t h e B riti s h D e n t al A s s o ci a ti o n. Of fi ci al j o u r n al o f t h e B riti s h D e n t al A s s o ci a ti o n.

Level 6 Local context Not practical to retain as retention of the tooth, which may or may not be restorable, would severely constrain, complicate or compromise an otherwise straightforward and predictable restorative plan. For example, a single intact tooth remaining where extensive implantretained bridgework is planned. General context These are extreme and rare cases that should be managed in tertiary care. Patients with lifethreatening medical conditions, for example, a patient undergoing chemotherapy or severe congestive cardiac failure, where the objective of dental treatment is pain relief only. Determining practicality After a comprehensive assessment of the patient, the DPI score (Table 1) is derived by adding together the scores allocated in each of the four previously described categories. An overall DPI score of 1–2 implies that if there is a periodontal, endodontic, and/ or structural issue that may be simply and predictably treated. Where a level 2 score is recorded for any one of the restorative categories, advanced training and expertise in managing complex problems would be desirable; these cases may be referred for secondary or tertiary care. The decision on whether to restore, refer for an opinion, or extract a tooth can be challenging; this may be further complicated when the tooth is contextualised as part of the patient’s dentition (local context), and even further when taking into account the patient’s overall health/well-being (general context). The ‘context’ weighting increases if extraction, or referral to secondary or tertiary care may be indicated. The level a tooth has initially been assigned to may well need to be changed, if upon commencing treatment a complication and/or unplanned response to treatment has occurred. For example, in the endodontic category when the clinician cannot locate or negotiate the entire root canal, and/or when complete anaesthesia is difficult to achieve. While an extensively restored tooth may function well in an intact dentition, the consequences of failure may be of limited significance. Successful use of the tooth as a bridge abutment may be impractical when all the dental practicality aspects are considered together. When considering a tooth as a bridge abutment, in acknowledgement of the additional demands and potential complications upon the abutment teeth, it is weighted by at least 1 in the ‘context’ category).14,15 In addition, a DPI threshold of 4 is suggested, beyond which use of the tooth as bridge abutment is deemed to be inadvisable. As the DPI score increases, treatment is potentially more complex, less practical and therefore should be approached with a greater degree of circumspection. A DPI score ≥6 suggests that it is not practical to carry out definitive treatment to a tooth and other treatment modalities such as an implant might be considered. A DPI Score ≥6 does not necessarily mean that a tooth should not be restored, or that it should be immediately extracted, but it does accentuate a need for further careful reflection and/or possible referral to secondary or tertiary care for multi-disciplinary specialist consideration. Concluding remarks The DPI assists and expedites a  structured and formalised analysis of the many interplaying factors that should be considered in the decision-making process – including when to consider seeking advice and/or referral to secondary or tertiary care. The authors have found the DPI to be a useful and straightforward guide for treatment planning. Not only because the DPI score helps to express the practicality of treatment for a particular tooth, but also because it confirms that the various aspects of assessing restorability have been considered. The index encourages reflection upon the unique needs of the patient and assists in the delivery of holistic patient-centred care.16 Each patient and their dental need is unique; like any guideline, the DPI exists to assist rather than rigidly dictate how a dental problem is managed. Acknowledgements Dr Susan Tanner (Specialist Prosthodontist), Dr Almas Husain (Specialist Orthodontist) and Dr. Sophie Watkins (Consultant in Restorative Dentistry), London, UK. 1. Avila G, Galindo-Moreno P, Soehren S, Misch C E, Morelli T, Wang H. A novel decision-making process for tooth retention or extraction. J Periodontol 2009; 80: 476–491. 2. Whitworth J M, Walls A W, Wassell R W. Crowns and extracoronal restorations: endodontic considerations: the pulp, the root-treated tooth and the crown. Br Dent J 2002; 192: 323–327. 3. Esteves H, Correia A, Araújo F. Classification of Extensively Damaged Teeth to Evaluate Prognosis. J Can Dent Assoc 2011; 77: b105. 4. Marshall F J. Planning endodontic treatment. Dent Clin North Am 1979; 23: 495–518. 5. Messer H H. Clinical judgement and decision making in endodontics. Aust Endod J 1999; 25: 124–132. 6. Friedman S, Mor C. The success of endodontic therapy – healing and functionality. J Calif Dent Assoc 2004; 32: 493–503. 7. Kurer H G. The classification of single-rooted, pulpless teeth. Quintessence Int 1991; 22: 939–943. 8. McDonald A, Setchell D. Developing a tooth restorability index. Dent Update 2005; 32: 343–344. 9. Basic Periodontal Examination. Available at http://www. bsperio.org.uk/publications/downloads/39_143748_ bpe2011.pdf (accessed May 2017). 10. American Association of Endodontists. AAE Endodontic Case Difficulty Assessment Form and Guidelines. 2010. Available at https://www.aae.org/uploadedfiles/dental_professionals/endodontic_case_assessment/2006casedifficultyassessmentformb_edited2010.pdf (accessed May 2017). 11. Curry M. The utilization of case difficultly assessment when determining endodontic referral. Master’s Dissertation, Chapel Hill, University of North Carolina, 2009. 12. Pothukuchi K. Case assessment and treatment planning: what governs your decision to treat, refer or replace a tooth that potentially requires endodontic treatment? Aust Endod J 2006; 32: 79–84. 13. Yeng T, H H Messer, P Parashos. Treatment planning the endodontic case. Aust Dent J Endod Suppl 2007; 52: 1. 14. De Backer H, Van Maele G, De Moor N, Van de Berghe L, De Boever J. A 20-year retrospective survival study of fixed partial dentures. Int J Prosthodont 2006; 19: 143–153. 15. Pjetursson B E, Bragger U, Lang N P, Zwahlen M. Comparison of survival and complication rates of tooth supported fixed dental prostheses (FDPs) and implant supported FDPs and single crowns (SCs). Clin Oral Implant Res 2007; 18: 97–113. 16. General Dental Council. Standards for the dental team. GDC. Available at https://www.gdc-uk.org/api/files/Standards%20for%20the%20Dental%20Team.pdf (accessed May 2017). 758 BRITISH DENTAL JOURNAL | VOLUME 222 NO. 10 | MAY 26 2017 PRACTICE Of fi ci al j o u r n al o f t h e B riti s h D e n t al A s s o ci a ti o n.

endodontics Editor: MILTON SISKIN, D.D.S. College of Dentistry The University of Tennessee 847 Monroe Avenue Memphis, Tennessee 38163 Root canal anatomy of the human permanent teeth Frank J. Vertucci, D.iU.D.,* Gainesville, Fla. UNIVERSITY OF FLORIDA COLLEGE OF DENTISTRY Two thousand four hundred human permanent teeth were decalcified, injected with dye, and cleared in order to determine the number of root canals and their different types, the ramifications of the main root canals, the location of apical foramina and transverse anastomoses, and the frequency of apical deltas. (ORAL SURC. 58~589-599, 1984) T he main objective of endodontic therapy is the thorough mechanical and chemical cleansing of the entire pulp cavity and its complete obturation with an inert filling material. According to Seltzer and Bender,’ failures in treatment occur despite rigid adherence to this basic principle. Ingle2 lists the most frequent cause of endodontic failure as apical percolation and subsequent diffusion stasis into the canal. The main reasons for this failure are incomplete canal obturation, an untreated canal and inadvertent removal of a silver cone. A canal is often left untreated because the dentist fails to recognize its presence. The dentist must have a thorough knowledge of root canal morphology before he can successfully treat a tooth endodontically. In the literature, there is divergence of opinion as to the anatomy of the pulp cavities of the human permanent teeth.3-32 The incidence of two or more root canals in the mandibular first premolar, for example, has been reported to be as low as 2.7% and as high as 62.5%, whereas the incidence of two or more root canals in the mandibular second premolar has been reported to vary between 0% and 34.3%.3-1’ The incidence of two canals at the apex of the maxillary second premolar has been reported to be as low as 4% and as high as 50%.6-13 *Associate Professor and Chairman, Department of Endodontics. These discrepancies are, in part, the result of the marked variations in anatomy that are present and, in part, the result of the very real difficulties that are always encountered when root canal morphology is studied. Because of the many dissimilarities in selection of material and classification of canal configurations, the results of most reports cannot be compared directly with one another. Because the literature is inconclusive, I decided to conduct a detailed investigation of the anatomy of the root canals of extracted human teeth. A standardized technique that involved examination of transparent specimens was used. METHODS AND MATERIALS For this investigation, 2,400 permanent teeth were obtained from various oral surgery practices. All teeth were obtained from adults. The age, sex, and race of the patients and the reasons for extraction were not recorded. Immediately after extraction, the teeth were fixed in 10% formalin and decalcified in 5% hydrochloric acid. On completion of this process, the teeth were washed in tap water and placed in a 5% solution of potassium hydroxide for 24 hours. The teeth were washed in tap water for 2 hours, and hematoxylin dye was injected into the pulp cavities with the use of a 25-gauge needle on a Luer-Lok plastic disposable syringe. Hematoxylin was used because of its ability to stain fresh pulp tissue, even 589

590 Vertucci Oral Surg. November, I984 Table I. Morphology of the maxillary permanent teeth Tooth Central Lateral Canine First premolar Second premolar First molar Second molar No. of Canals with Position of lateral canals Root teeth lateral canals Cervical Middle Apical Furcation 100 24 I 6 93 100 26 I 8 91 100 30 0 IO 90 400 49.5 4.1 10.3 74.0 Il.0 200 59.5 4.0 16.2 78.2 1.6 MB 100 51 10.7 13.1 58.2 f DB 100 36 10.1 12.3 59.6 18 P 100 48 9.4 11.3 61.3 1 MB 100 50 IO.1 14.1 65.8 t DB 100 29 9.1 13.3 67.6 IO P 100 42 8.7 1 I.2 70. I 1 Note: Figures represent percentage of the total. Table II. Morphology of the mandibular permanent teeth Tooth Central Lateral Canine First premolar Second premolar First molar Second molar No. of Canals with Position of lateral canals Root teeth lateral canals Cervical Middle Apical Furcation 100 20 3 12 85 100 18 2 15 83 100 30 4 16 80 - 400 44.3 4.3 16.1 78.9 0.7 400 48.3 3.2 16.4 80.1 0.3 Mesial 100 45 10.4 12.2 54.4 t 23 Distal 100 30 8.7 IO.4 51.9 1 Mesial 100 49 10.1 13.1 65.8 t II Distal 100 34 9.1 11.6 68.3 i Note: Figures represent percentage of total. Table III. Classification and percentage of root canals of the maxillary teeth Teeth No. We I Type II Type III Total with Type IV The V Type VI Type VII of I 2-l I-2-1 one canal 2 l-2 2-I-2 l-2-1-2 teeth canal canals canals at apex canals canals canals canals Maxillary central Maxillary lateral Maxillary canine Maxillary first premolar* Maxillary second premolar Maxillary first molar MesiobuccalS Distobuccal Palatal Maxillary second molar Mesiobuccal Distobuccal Palatal 100 100 100 400 3 200 100 100 100 8 48 0 0 0 I8 22 100 0 100 0 100 0 26 62 75 II 100 100 100 45 100 100 37 0 0 82 I8 100 0 100 0 71 100 100 I7 0 88 12 0 0 0 0 0 100 0 0 0 0 0 0 100 0 0 0 0 *Results published previously in Vertucci, F.J., and Gegauff, A.: Root canal morphology of the maxillary first premolar, J. Am. Dent. Asmc. 99:194, 1919. tResults published previously in Vertucci, F.J., Seelig, A., and Gillis, R.: Root canal morphology of the human maxillary second premolar, ORAL SIJRG. 58: 456, 1974. $Results published previously in Vertucci, F.J.: The endodontic significance of the mesiobuccal root of themaxillary first molar, Navy Med. 63: 29, 1974.

Volume 58 Number 5 Root canal anatomy of human permanent teeth 591 Transverse anastomosis between canals Position of transverse anastomosis Position of apical foramen Cervical Middle Apical Central Lateral Apical Deltas 34.2 30.8 52 0 0 21 0 0 - - - 16.4 58 18.8 50 10 15 0 0 0 0 8 72 0 0 0 0 25.6 31.2 15 0 0 20 0 0 12 88 1 22 78 3 14 86 3 12.0 88.0 3.2 22.2 77.8 15.1 24 76 8 19 81 2 18 82 4 12 88 3 17 83 2 19 81 4 Note: Figures represent percentage of the total. Transverse anastomosis between canals Position of transverse anastomosis Position of apical foramen Cervical Middle Apical Central Lateral Apical Deltas - - - - 25 15 5 - - - - 20 80 6 - - - - 30 IO 8 32.1 20.6 52.9 26.5 15 85 5.1 30 0 66.1 33.3 16.1 83.9 3.4 63 12 75 13 22 78 10 55 10 72 18 20 80 14 31 10 71 13 19 81 6 16 11 74 15 21 79 7 Now Figures represent percentage of total. Total with Type VIII Total with two canals 3 three canals at apex canals at apex 0 0 0 0 0 0 0 0 0 69 5 5 24 1 I 18 0 0 0 0 0 0 0 0 12 0 0 0 0 0 0 0 0 in the smallest accessory canals, and because it can be removed from the external surface of the tooth, thereby allowing for a clearer specimen. The injected teeth were then dehydrated in successive solutions of 70%, 95%, and 100% alcohol for 5 hours each. The dehydration was necessary because the clearing agent is not miscible with water. Finally, the specimens were placed in clear liquid plastic casting resin* and were completely cleared within 24 hours. RESULTS The transparent specimens were examined under the dissecting microscope, and the number and type of root canals, the number and location of lateral canals and apical foramina, and the frequency of apical deltas were recorded. These data are summarized in Tables 1 and II. *Fibre-Glass Evercoat Co., Inc., Cincinnati, Ohio.

592 Vertucci Oral Surg. November, I984 Fig. 1. Maxillary anterior teeth. Top row, Maxillary canines. Middle row, Maxillary lateral incisors. Bottom row, Maxillary central incisors. Table IV. Classification and percentage of root canals of the mandibular teeth No. TYP I Type II Type III Total with Type IV Type V Type VI Type VII Of 1 2-1 I-2-I one canal 2 1-2 2-l-2 I-2-1-2 Teeth terlh canal canals canals at apex canals canals canals canals Mandibular central incisor* 100 70 5 22 97 3 0 0 0 Mandibular lateral incisor* 100 75 5 18 98 2 0 0 0 Mandibular canine* 100 78 14 2 94 6 0 0 0 Mandibular first premolar+ 400 70 0 4 74 1.5 24 0 0 Mandibular second premolar? 400 97.5 0 0 97.5 0 2.5 0 0 Mandibular first molar$ Mesial 100 12 28 0 40 43 8 10 0 Distal 100 70 15 0 85 5 8 2 0 Mandibular second molar Mesial 100 27 38 0 65 26 9 0 0 Distal 100 92 3 0 95 4 1 0 0 *Results published previously in Vertucci, F.J.: Root canal anatomy of the mandibular anterior teeth, J. Am. Dent. Assoc. 89:369, 1974. tResults published previously in Vertucci, F.J.: Root Canal Morphology of Mandibular Premolar Teeth, J. Am. Dent. Assoc. 97:47, 1978. $Re.sults published previously in Vertucci, F.J., and Williams, R.: Root canal anatomy of the mandibular first molar, J. N.J. Dent. Assoc. 4527-28, 1974

Volume 58 Number 5 Root canal anatomy of human permanent teeth 593 Fig. 2. A, Maxiilary first premolars, one canal at apex. Top row, Type II. Bottom row, Type I. B, Maxillary first premolars, two canals at apex. Top row, Type V. Bottom row, Type IV. C!, Maxillary first premolar, three canals at apex (Type VIII). Total with two canals at apex 3 2 6 25.5 2.5 Type VIII 3 canals 0 0 0 0.5 0 Total with three canals at apex 0 0 0 0.5 0 59 1 1 15 0 0 35 0 0 5 0 0 The root canal configurations present within the roots of human permanent teeth can be classified into eight types: Type I. A single canal extends from the pulp chamber to the apex. Type II. Two separate canals leave the pulp chamber and join short of the apex to form one canal. Type III. One canal leaves the pulp chamber, divides into two within the root, and then merges to exit as one canal. Type IV. Two separate and distinct canals extend from the pulp chamber to the apex. Type V. One canal leaves the pulp chamber and divides short of the apex into two separate and distinct canals with separate apical foramina.

594 Vertucci Oral Surg. November, 1984 Fig. 3. A, Maxillary second premolars, one canal at apex. Top row, Type I. Middle row, Type II. Bottom row, Type III. B, Maxillary second premolars, two canals at apex. Top row, Type IV. Middle row, Type V. Bottom row left, Type VI. Bottom row right, Type VII. C, Maxillary second premolar, three canals at apex (Type VIII). Fig. 4. Mesiobuccal root of maxillary first molars. Left, Type I. Middle, Type II. Right, Type IV. Type VI. Two separate canals leave the pulp chamber, merge in the body of the root, and redivide short of the apex to exit as two distinct canals. Type VII. One canal leaves the pulp chamber, divides and then rejoins within the body of the root, and tinally redivides into two distinct canals short of the apex. Type VIII. Three separate and distinct canals extend from the pulp chamber to the apex. The percentages of human permanent teeth with these canal configurations are presented in Tables III and IV. The anatomic variations present in each tooth are illustrated in Figs. 1 to IO. The most variable root canal anatomy was found in the maxillary second premolar. DlSCUSSlON During the past 100 years, there have been many excellent studies of pulp morphology. Upon comparing the findings of these studies with those of the

Volume 58 Number 5 Root canal anatomy of human permanent teeth 595 Fig. 5. Mesiobuccal root of maxillary second molars. Left, Type I. Middle, Type II. Right, Type IV. B I( : * B Fig. 6. Mandibular anterior teeth. Top row, Mandibular central incisors. A, Type I. B, Type II. C, Type III. D, Type IV. Middle row, Mandibular lateral incisors. A, Type I. B, Type II. C, Type III. D, Type IV. Bottom row, Mandibular canines. A, Type I. B, Type II. C, Type III. D, Type IV.

596 Vertucci Oral SW&. November, 1984 Fig. 7. A, Mandibular first premolars. Top row, Type I. Second row, Type III. Third row, Type IV. Bottom TOW, Type V. B, Mandibular first premolar, three canals at apex (Type VIII), Fig. 8. Mandibular second premolars. Top row, Type I. Bottom row, Type V.

Volume 58 Number 5 Root canal anatomy of human permanent teeth 597 Fig. 9. Mandibular first molars. Top row, Mesial root. A, Type I. B. Type II. C, Type IV. D, Type V. E, Type VI. F, Type VIII. Bottom row, Distal root. A, Type I. B, Type II. C, Type IV. D, Type V. E, Type VI. Fig. 10. Mandibular second molars. Top row, Mesial root. A, Type I. B, Type II. C. Type IV. D. Type V. Bottom row, Distal root. A, Type I. B, Type II. C, Type IV. D, Type V.

598 Vertucci Oral Surg. November. I984 Fig. 11. Root canal on direct periapical exposure (arrow) shows sudden narrowing; at this point canal divides into two parts as shown by radiographic view of buccolingual aspect and by transparent specimen. (D, Direct periapical exposure; B-L, buccolingual aspect; TS, transparent specimen.) present investigation, one finds that the results reported by Okumura,* who also used transparent specimens, and Pineda and Kuttler,l” who employed a radiographic evaluative technique, come closest to the findings reported here. It appears that the use of an intact root of a specimen rendered transparent by decalcification and radiographic examination enables the investigator to view more clearly all of the ramifications of the root canal system. The clearing technique has considerable value in the study of root canal anatomy, for it gives a three-dimensional view of the pulp cavity in relation to the exterior of the tooth.33 In addition, it is not necessary to enter the specimens with instruments; thus, the original form and relationship of the canals are maintained. The technique used in the present study differs from other clearing techniques mainly in the nature of the clearing process; a liquid casting resin was used rather than an agent such as xylene. Slowey34 states that the root canal anatomy of each tooth has certain commonly occurring characteristics as well as numerous atypical ones that can be road maps to successful endodontics. The expected root canal anatomy dictates the location of the initial entry of access, it dictates the size of the first files used, and it contributes to a rational approach to solving the problems that arise during therapy. Therefore, a thorough knowledge of the root canal anatomy from access to obturation is essential to give the highest possible chance for success. The first consideration the dentist must have in performing endodontic therapy involves the anatomy of the tooth itself. Prior to beginning the access preparation, he should study radiographs from several different angles. If, on the direct periapical exposure, he notices that a root canal shows a sudden narrowing or even disappears, it means that at this point the canal divides into two parts which either remain separate (Type V) or merge (Type II) before reaching the apex (Fig. 11). Having the information observed from the radiographs and knowing what combinations of internal anatomy are possible, the dentist should be able to determine what type of canal configuration is present. This information, gained prior to initiation of therapy, will greatly facilitate subsequent treatment. Failure to find and fill a canal has been demonstrated to be a causative factor in the failure of endodontic therapy. 35 It is of utmost importance that all canals be located and treated during the course of nonsurgical endodontic therapy. An examination of the floor of the pulp chamber offers clues to the type of canal configuration present. When there is only one canal, it is usually located rather easily in the center of the access preparation. If only one orifice is found, and it is not in the center of the tooth, it is probable that another canal is present and the operator should search for it on the opposite side. Radiographs from various angles, some with a file in place, may be helpful. The relationship of the two canal orifices to each other is also significant. The closer the orifices are to each other, the greater are the chances that the two canals join at some point within the body of the root. Teeth with canal bifurcations in the middle or apical third may present problems in treatment. Although one of the two canals, the one most continuous with the large main passage, is usually amenable to adequate enlarging and filling procedures, the preparation and filling of the other canal is often extremely difficult. The presence of an unfilled canal may explain some of the endodontic failures associated with teeth, even though radiographically and clinically the canal system seems to be obturated. When either pain or periapical breakdown is seen after apparently effective nonsurgical endodontic

Volume 58 Number 5 therapy, the possible presence of an additional canal should be considered before the tooth is condemned or surgery is scheduled. If an apical root resection and reverse filling procedure becomes necessary, a complication may result. Surgery may cause a single apical foramen to become two separate foramina. Results will be poor if a search for the second canal is not routinely made during the surgical procedure. An awareness that eight possible canal configurations occur and that complications from a surgical endodontic procedure can arise should increase the rate of successful endodontic therapy. SUMMARY AND CONCLUSIONS Two thousand four hundred human permanent teeth were decalcified, injected with dye, cleared, and studied. The following data were obtained: the number of root canals and their different types, the ramifications of the main root canals, the location of apical foramina and transverse anastomoses, and the frequency of apical deltas. The findings are summarized in four tables, which have been prepared as a practical aid for the dentist. An accurate knowledge of the morphology of the pulp cavity is essential before an endodontic procedure can be approached rationally. The frequency with which root canals unite should be considered during enlargement and filling procedures. The dentist also should be aware of the possible existence of bifurcated and double canals if root canal therapy should unexpectedly fail. A knowledge of these variations will assist the dentist in reaching conclusions when diagnosing and treating endodontic cases. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. Seltzer S, Bender IB: Cognitive dissonance in endodontics. ORAL SURG 20: 505, 1965. Ingle JI: Endodontics, ed. 2, Philadelphia, 1965, Lea & Febiger, p. 43. Amos ER: Incidence of bifurcated root canals in mandibular bicuspids. J Am Dent Assoc 50: 70, 1955. Green D: Double canals in single roots. ORAL SURG 35: 689, 1973. Zillich R, Dowson J: Root canal morphology of mandibular first and second premolars. ORAL SURG 36: 738, 1973. Hess W: Anatomy of the root canals of the teeth of the permanent dentition, Part I, New York, 1925, William Wood & Company, pp. 27-29. Barrett MT: The internal anatomy of the teeth with special reference to the pulp with its branches. Dent Cosmos 67: 581, 1925. Okumura T: Anatomy of the root canals, Tram Seventh Int Dent Congress 1: 170, 1926. Mueller AH: Anatomy of the root canals of the incisors, cuspids and bicuspids of the permanent teeth. J Am Dent Assoc 20: 1361, 1933. Root canal anatomy of human permanent teeth 599 10. Pineda F, Kuttler Y: Mesiodistal and buccolingual roentgenographic investigation of 7,275 root canals. ORAL SURG 33: 101, 1972. 1 I. Vertucci FJ: Root canal morphology of mandibular premolar. J Am Dent Assoc 97: 47, 1978. 12. Green D: Morphology of the endodontic system, New York, 1969, David Green, pp. 14-15. 13. Vertucci FJ, Seelig A, Gillis R: Root canal morphology of the human maxillary second premolar. ORAL SURG 58: 456, 1974. 14. Skillen WG: Morphology of root canals. J Am Dent Assoc 19: 719, 1932. 15. Mueller AH: Morphology of root canals. J Am Dent Assoc 23: 1698, 1936. 16. Green D: Morphology of the pulp cavity of the permanent teeth. ORAL SURG S: 743, 1955. 17. Rankine-Wilson RW, Henry P: The bifurcated root canal in lower anterior teeth. J Am Dent Assoc 70: 1162, 1965. 18. Vertucci FJ: Root canal anatomy of the mandibular anterior teeth, J Am Dent Assoc 89: 369, 1974. 19. Carns EJ, Skidmore AE: Configurations and deviations of root canals of maxillary first premolars. ORAL SURG 36: 880, 1973. 20. Vertucci FJ, Gegauff A: Root canal morphology of the maxillary first premolar. J Am Dent Assoc 99: 194, 1979. 21. Weine FS, Healey HJ, Gerstein H, Evanson L: Canal configuration in the mesiobuccal root of the maxillary first molar and its endodontic significance. ORAL SURG 28: 419, 1969. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. Darnelles P: Consideracoes anatomicas sobre a conformacao interna da raiz mesiovestibular do primeiro molar superior permanente. Rev Gaucha Odontol 7: 35, 1959. Vertucci FJ: The endodontic significance of the mesiobuccal root of the maxillary first molar. Navy Med 63: 29, 1974. Skidmore AE, Bjorndal AM: Root canal morphology of the human mandibular first molar. ORAL SURG 32: 778, 1971. Vertucci FJ, Williams R: Root canal anatomy of the mandibular first molar. J N J Dent Assoc 45: 27-28, 1974. Cooke HG, Cox FL: C-shaped canal configurations in mandibular molars. J Am Dent Assoc 99: 832, 1979. Seidberg BH, Altman M, Guttuso J, Suson M: Frequency of two mesiobuccal root canals in maxillary permanent first molars. J Am Dent Assoc 87: 852, 1973. Pomeranz HH, Fishelberg G: The secondary mesiobuccal canal of maxillary molars. J Am Dent Assoc 88: 119, 1974. Altman M, Guttuso J, Seidberg BH, Langeland K: Apical root canal anatomy of human maxillary central incisors. ORAL SURG 30: 694-699, 1970. Green D: A stereomicroscopic study of the root apices of 400 maxillary and mandibular anterior teeth. ORAL SURG 9: 1224-1232, 1956. Nosonowitz DM, Brenner MR: The major canals of the mesiobuccal root of the maxillary first and second molars. NY J Dent 43: 12, 1973. Harris WE: Unusual root canal anatomy in a maxillary molar. J Endod 6: 573, 1980. Barker BCW, Lockett BC, Parsons KC: The demonstrations of root canal anatomy. Aust Dent J 14: 37-41, 1969. Slowey RR: Root canal anatomy, road map to successful endodontics. Dent Clin North Am 23: 555, 1979. Stewart GG: Evaluation of endodontics results. Dent Clin North Am 11: 711, 1967. Reprinf requests fo: Dr. Frank J. Vertucci Department of Endodontics University og Florida College of Dentistry Gainesville, FL 32610

Root canal morphology and its relationship to endodontic procedures FRANK J. VERTUCCI The hard tissue repository of the human dental pulp takes on numerous configurations and shapes. A thorough knowledge of tooth morphology, careful interpretation of angled radiographs, proper access preparation and a detailed exploration of the interior of the tooth are essential prerequisites for a successful treatment outcome. Magnification and illumination are aids that must be utilized to achieve this goal. This article describes and illustrates tooth morphology and discusses its relationship to endodontic procedures. A thorough understanding of the complexity of the root canal system is essential for understanding the principles and problems of shaping and cleaning, for determining the apical limits and dimensions of canal preparations, and for performing successful microsurgical procedures. It is important to visualize and to have knowledge of internal anatomy relationships before undertaking endodontic therapy. Careful evaluation of two or more periapical radiographs is mandatory. These angled radiographs provide much needed information about root canal morphology. Martinez-Lozano et al. (1) examined the effect of x-ray tube inclination on accurately determining the root canal system present in premolar teeth. They found that by varying the horizontal angle 201 and 401 the number of root canals observed in maxillary first and second and mandibular first premolars coincided with the actual number of canals present. In the case of mandibular second premolars only the 401 horizontal angle identified the correct morphology. The critical importance of carefully evaluating each radiograph taken prior to and during endodontic therapy was stressed by Friedman et al. (2). In a case report of five canals in a mandibular first molar, these authors emphasized that it was the radiographic appearance which facilitated recognition of the complex canal morphology. They cautioned ‘that any attempt to develop techniques that require fewer radiographs runs the risk of missing information which may be significant for the success of therapy’. Radiographs, however, may not always determine the correct morphology particularly when only a buccolingual view is taken. Nattress et al. (3) radiographed 790 extracted mandibular incisors and premolars in order to assess the incidence of canal bifurcation in a root. Using the ‘fast break’ guideline (Fig. 1) that disappearance or narrowing of a canal infers that it divides resulted in failure to diagnose one-third of these divisions from a single radiographic view. The evaluation of the root canal system is most accurate when the dentist uses the information from multiple radiographic views together with a thorough clinical exploration of the interior and exterior of the tooth. The main objective of root canal therapy is thorough shaping and cleaning of all pulp spaces and its complete obturation with an inert filling material. The presence of an untreated canal may be a reason for failure. A canal may be left untreated because the dentist fails to recognize its presence. It is extremely important that clinicians use all the armamentaria at their disposal to locate and treat the entire root canal system. It is humbling to be aware of the complexity of the spaces we are expected to access, shape, clean and fill. We can take comfort in knowing that even under the most 3 Endodontic Topics 2005, 10, 3–29 All rights reserved Copyright r Blackwell Munksgaard ENDODONTIC TOPICS 2005 1601-1538

difficult circumstances our current methods of root canal therapy result in an exceptionally high rate of success. Diagnostic measures such as multiple pre-operative radiographs, examination of the pulp chamber floor with a sharp explorer, troughing of grooves with ultrasonic tips, staining the chamber floor with 1% methylene blue dye, performing the sodium hypochlorite ‘champagne bubble’ test and visualizing canal bleeding points are important aids in locating root canal orifices. Stropko (4) recommends the use of 17% aqueous EDTA, 95% ethanol and the Stropko irrigator, fitted with a 27 G notched endodontic irrigating needle to clean and dry the pulp chamber floor prior to visually inspecting the canal system. An important aid for locating root canals is the dental-operating microscope (DOM) which was introduced into endodontics to provide enhanced lighting and visibility (Fig. 2). It brings minute details into clear view. It enhances the dentists ability to selectively remove dentine with great precision thereby minimizing procedural errors. Several studies have shown that it significantly increases the dentists ability to locate and negotiate canals. Studying the mesiobuccal root of maxillary molars, Baldassari-Cruz et al. (5) demonstrated an increase in the number of second mesiobuccal canals (MB-2) located from 51% with the naked eye to 82% with the DOM. Coelho de Carvalho and Zuolo (6) concluded that the DOM made canal location easier by magnifying and illuminating the grooves in the pulpal floor and differentiating the color differences between the dentine of the floor and walls. The DOM enabled them to find 8% more canals in mandibular molars. Gorduysus et al. (7) determined that the DOM did not significantly improve their ability to locate canals but rather facilitated their ability to negotiate them. Schwarze et al. (8) identified 41.3% of MB-2 canals using magnifying loops and 93.7% of MB-2 canals with the DOM. Buhrley et al. (9) on the other hand, determined that dental loops and the DOM were equally effective in locating MB-2 canals of maxillary molars. When no magnification was used this canal was located in only 18.2% of the teeth. Kulild and Peters (10) utilizing the DOM located two canals in the mesiobuccal root of maxillary molars 95.2% of the time. Stropko (4) determined that a higher incidence of MB-2 canals were located ‘as he became more experienced, schedule sufficient time for treatment, routinely used the DOM and employed specific instruments adopted for microendodontics’. Working in this environment he clinically located MB-2 canals in 93% of maxillary first molars and 60% of second molars. All of these studies demonstrate that mangification and illumination are essential armamenteria for performing endodontic therapy. Components of the root canal system The entire space in the dentine of the tooth where the pulp is housed is called the pulp cavity (Fig. 3). Its Fig. 1. Schematic representation of a premolar periapical radiograph which reveals clues about root canal morphology. An abrupt disappearance of the large canal in the mandibular first premolar usually signifies a canal bifurcation. Fig. 2. The adaptation of the dental operating microscope has provided exceptional advances in locating and negotiating canal anatomy. Vertucci 4

outline corresponds to the external contour of the tooth (11). However, factors such as physiologic aging, pathology and occlusion shape its size by the production of secondary and tertiary dentine and cementum. The pulp cavity is divided into two portions: the pulp chamber which is located in the anatomic crown of the tooth and the pulp or root canal(s) which are found in the anatomic root. Other features include pulp horns, lateral, accessory and furcation canals, canal orifices, intercanal connections, apical deltas and apical foramina. A root canal begins as a funnel-shaped canal orifices generally present at or slightly apical to the cervical line and ends at the apical foremen which opens onto the root surface between 0 and 3 mm from the center of the root apex (12–17). Nearly all root canals are curved particularly in a facial-lingual direction (18). These curvatures may pose problems during shaping and cleaning procedures because they are not evident on a standard facial radiograph. Angled views are necessary to determine their presence, direction and severity. A curvature may be a gradual curve of the entire canal or a sharp curvature near the apex. Double ‘s-shaped’ canal curvatures can also occur. In most cases, the number of root canals corresponds with the number of roots but an oval-shaped root may have more than one canal. Accessory and lateral canals extend from the pulp to the periodontium. An accessory canal is any branch of the main pulp canal or chamber that communicates with the external surface of the root. A lateral canal is an accessory canal located in the coronal or middle third of the root, usually extending horizontally from the main root canal (19). They occur 73.5% of the time in the apical third, 11.4% of the time in the middle third and 6.3% of the time in the cervical third of the root (13). They are formed by the entrapment of periodontal vessels in Hertwig’s epithelial root sheath during calcification (20). They serve as avenues for the passage of irritants primarily from the pulp to the periodontium. Accessory canals may also occur in the bifurcation or trifurcation of multirooted teeth (13). Vertucci (21) called these furcation canals (Fig. 4). They form as a Fig. 3. Major anatomic components of the root canal system. Fig. 4. Maxillary first molar illustrating a furcation canal (arrow). Fig. 5. Accessory canals occur in three distinct patterns in mandibular first molars. (A) In 13%, a single furcation canal extends from the pulp chamber to the intraradicular region. (B) In 23%, a lateral canal extends from the coronal third of a major root canal to the furcation region; 80% extend from the distal root canal. (C) Ten percentage of the teeth exhibit both lateral and furcation canals. Root canal morphology 5

Table 1. Morphology of the maxillary permanent teethn Tooth Root No. of teeth Canals with lateral canals Position of lateral canals Transverse anastomosis between canals Position of transverse anatomosis Position of apical foramen Apical deltas Cervical Middle Apical Furcation Cervical Middle Apical Central Lateral Central – 100 24 1 6 93 – – – – – 12 88 1 Lateral – 100 26 1 8 91 – – – – – 22 78 3 Canine – 100 30 0 10 90 – – – – – 14 86 3 First premolar – 400 49.5 4.7 10.3 74 11 34.2 16.4 58 25.6 12 88 3.2 Second premolar – 200 59.5 4 16.2 78.2 1.6 30.8 18.8 50 31.2 22.2 77.8 15.1 First molar MB 100 51 10.7 13.1 58.2 " 52 10 75 15 24 76 8 DB 100 36 10.1 12.3 59.6 18 0 0 0 0 19 81 2 P 100 48 9.4 11.3 61.3 # 0 0 0 0 18 82 4 Second molar MB 100 50 10.1 14.1 65.8 " 21 8 72 20 12 88 3 DB 100 29 9.1 13.3 67.6 10 0 0 0 0 17 83 2 P 100 42 8.7 11.2 70.1 # 0 0 0 0 19 81 4 Note: Figures represent percentage of the total. nResults published previously in: Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1984: 58:589–599. Vertucci 6

result of the entrapment of periodontal vessels during the fusion of the diaphragm which becomes the floor of the pulp chamber (20). In mandibular molars they occur in three distinct paterns (Fig. 5). The incidence of furcation canals for each tooth can be found in Tables 1 and 2. Vertucci and Anthony (22) utilizing the scanning electron microscope found that the diameter of furcation openings in mandibular molars varied from 4 to 720 mm. Their numbers ranged from 0 to more than 20 per specimen. Foramina on both the pulp chamber floor and the furcation surface were found in 36% of maxillary first molars 12% of maxillary second molars, 32% of mandibular first molars, and 24% of mandibular second molars (Fig. 6A and B). Mandibular teeth have a higher incidence (56%) of foramina involving both the pulp chamber floor and furcation surface than do maxillary teeth (48%). No relationship was found between the incidence of accessory foramina and the occurrence of calcification of the pulp chamber or the distance from the chamber floor to the furcation. Radiographic evidence failed to demonstrate the presence of furcation and lateral canals in the coronal portion of these roots. Haznedaroglu et al. (23) determined the incidence of patent furcation canals in 200 permanent molars in a Turkish population. Using a stereomicroscope this group examined the pulp chamber floor which was stained with 0.5% basic fuschian dye. Patent furcal canals were detected in 24% of maxillary and mandibular first molars, 20% of mandibular second molars and 16% of maxillary second molars. These canals may be the cause of primary endodontic lesions in the furcation of multirooted teeth. Root canal anatomy Together with diagnosis and treatment planning, knowledge of the canal morphology and its frequent variations is a basic requirement for endodontic success. Stressing the significance of canal anatomy, Peters et al. (24) reported that variations in canal geometry before shaping and cleaning procedures had more influence on the changes that occur during preparation than the instrumentation techniques themselves. From the early work of Hess and Zurcher (25) to the most recent studies demonstrating anatomic complexities of the root canal system, it has long been established that a root with a tapering canal and a single foremen is the exception rather than the rule. Investigators have shown multiple foramina, additional canals, fins, deltas, intercanal connections, loops, ‘Cshaped’ canals and accessory canals. Consequently the practitioner must treat each tooth assuming that complex anatomy occurs often enough to be considered normal. The dentist must be familiar with the various pathways that root canals take to the apex. The pulp canal system is complex and canals may branch, divide and rejoin. Weine (26) categorized the root canal systems in any root into four basic types. Vertucci et al. (27) utilizing cleared teeth which had their pulp cavities stained with hematoxalin dye (Fig. 7), found a much more complex canal system and identified eight pulp space configurations (Fig. 8). The percentages of human permanent teeth with these canal configurations are presented in Tables 3 and 4. The anatomic variations present in these teeth are listed in Tables 1 and 2. The only tooth to demonstrate all eight configurations was the maxillary second premolar. Caliskan et al. (28) evaluated 1400 permanent teeth in a Turkish population and obtained morphology results similar to those reported by Vertucci. However, these authors found more than one canal in 22% of maxillary laterals, 55% of the mesiobuccal roots of maxillary second molars and 30% in the distobuccal root of mandibular second molars. They attributed the differences to the variations of populations in both studies. Kartal and Yanikoglu (29) studied 100 mandibular anterior teeth and found two new root canal types which had not been previously identified. The first new configuration consists of two separate canals which extend from the pulp chamber to midroot where the lingual canal divides into two; all three canals then join in the apical third and exit as one canal. In their second configuration, one canal leaves the pulp chamber, divides into two in the middle third of the root, rejoins to form one canal which again splits and exits as three separate canals with separate foramina. Gulabivala et al. (30) examined mandibular molars in a Burmese population and found seven additional canal configurations (Fig. 9). These include three canals joining into one or two canals; two canals separating into three canals; two canals joining, redividing into two and terminating as one canal; four canals joining into two; four canals extending from orifices to apex and five canals joining into four at the apex. Sert and Root canal morphology 7

Table 2. Morphology of the mandibular permanent teethn Tooth Root No. of teeth Canals with lateral canals Position of lateral canals Transverse anastomosis between canals Position of transverse anastomosis Position of apical foramen Apical deltas Cervical Middle Apical Furcation Cervical Middle Apical Central Lateral Central – 100 20 3 12 85 – – – – – 25 75 5 Lateral – 100 18 2 15 83 – – – – – 20 80 6 Canine – 100 30 4 16 80 – – – – – 30 70 8 First premolar – 400 44.3 4.3 16.1 78.9 0.7 32.1 20.6 52.9 26.5 15 85 5.7 Second premolar – 400 48.3 3.2 16.4 80.1 0.3 30 0 66.7 33.3 16.1 83.9 3.4 First molar Mesial 100 45 10.4 12.2 54.4 " 63 12 75 13 22 78 10 23 Distal 100 30 8.7 10.4 57.9 # 55 10 72 18 20 80 14 Second molar Mesial 100 49 10.1 13.1 65.8 " 31 10 77 13 19 81 6 11 Distal 100 34 9.1 11.6 68.3 # 16 11 74 15 21 79 7 Note: Figures represent percentage of the total. nResults published previously in: Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1984: 58:589–599. Vertucci 8

Bayirli (31) evaluated root canal configurations in 2800 teeth by gender in a Turkish population. Ninety-nine percent of their specimens were identical to the specimens in the Vertucci classification. The remaining 1% (36 teeth) represent 14 additional canal morphologies which occurred twice as often in mandibular teeth. These authors concluded that gender plays a role in determining canal morphology and that both gender and ethnic origin should be considered during the preoperative evaluation stage of root canal therapy. In addition to in vitro studies, a large number of case reports have been published over the past two decades which describe a variety of complex canal configurations. Some of these reports are listed in Tables 5–8. One report (81) was critical about studies reporting ‘freak’ cases that he felt were rare. However, there seems to be an increase in the reporting of complex anatomy both in vitro and in vivo. It is important that these reports be published because it draws attention to their existence so that similar anatomy may be recognized and treated. Specific types of canal morphology appear to occur in different racial groups. Trope et al. (82) found that black patients have a higher number of mandibular premolars with extra canals than white patients. Black patients had more than one canal in 32.8% of first premolars and 7.8% of second premolars. Multiple canals in white patients occur in 13.7% of first premolars and 2.8% of second premolars. Walker (83– 85) determined that Asians have different percentages of canal configurations than those reported in studies dominated by Caucasians and Africans. Wasti et al. (86) concluded that south Asian Pakistanis have root canal systems that are different than Caucasians. Manning (87) found that Asians have a higher frequency of single rooted and C-shaped mandibular second molars. Weine et al. (88) on the other hand concluded that the occurrence of two canals in the mesio-buccal root of maxillary first molars in Japanese patients was similar to the morphology described for other ethnic populations. The clinician is confronted daily with a highly complex and variable root canal system. All available armamentaria must be utilized to achieve a successful outcome. Prior to beginning treatment, the dentist cannot precisely determine the actual number of root canals present. Pulp chamber floor and wall anatomy provides a guide to determining what morphology is actually present. Krasner and Rankow (89) in a study of 500 pulp chambers, determined that the cemento-enamel junction was the most important anatomic landmark for determining the location of pulp chambers and root canal orifices. They demonstrated that specific and consistent pulp chamber floor and wall anatomy exists and proposed laws for assisting clinicians identify canal morphology. The relationships expressed in these laws are particularly helpful in locating calcified canal orifices. These laws are: 1. ‘Law of symmetry 1: Except for maxillary molars, the orifices of the canals are equidistant from a line drawn in a mesiodistal direction through the pulpchamber floor.’ 2. ‘Law of symmetry 2: Except for maxillary molars, the orifices of the canals lie on a line perpendicular to a line drawn in a mesiodistal direction across the center of the floor of the pulp chamber.’ Fig. 6. (A) Electron photomicrograph of furcation surface of mandibular second molar. Multiple accessory foramina on furcation surface (original magnification,
30). (B) Electron photomicrograph of the pulp chamber floor of a mandibular second molar. Multiple accessory foramina range from 20 to 140 mm. Distal canal (D), mesial canals (M) are identified for orientation (original magnification,
30). Root canal morphology 9

3. ‘Law of color change: The color of the pulp chamber floor is always darker than the walls.’ 4. ‘Law of orifices location 1: the orifices of the root canals are always located at the junction of the walls and the floor.’ 5. ‘Law of orifices location 2: The orifices of the root canals are located at the angles in the floor–wall junction.’ 6. ‘Law of orifices location 3: The orifices of the root canals are located at the terminus of the root developmental fusion lines.’ The above laws were found to occur in 95% of the teeth examined. Five percent of mandibular second and third molars did not conform to these laws because of the presence of C-shaped canal anatomy. The pulp cavity generally decreases in size as an individual ages. Dentine formation is not uniform throughout life and is more rapid on the roof and floor than on the walls of pulp chambers of posterior teeth. Such calcifications result in a flattened pulp chamber (Fig. 10). A root always contains a root canal even though one is not visible on a radiograph and is difficult to locate and negotiate. If there is only one canal, it will lie in the center of the root. When beginning an access preparation on a tooth with a calcified pulp cavity, it is Fig. 7. Cleared teeth demonstrating root canal variation. (A) Mandibular second molar with three mesial canals. (B) Mandibular premolars with Vertucci type V canal configuration. (C) Mandibular premolars with three canals and intercanal connections. (D) Maxillary second molar with two palatal canals. (E) Maxillary first molar with two canals separating into three in mesiobuccal root. MB-2 orifice close to palatal orifice. Vertucci 10

helpful to do so before placing the dental dam. This enables the dentist to evaluate root relationships and work more effectively in the long axis of the tooth. However, once the canal is located, the dental dam must be placed before proceeding further. When searching for a calcified canal, magnification and illumination are absolute prerequisites for evaluating color changes and working deep inside the tooth. It is also helpful to occasionally stop and take additional radiographic views. The straight facial radiograph provides information about the mesial-distal penetration while an angled radiograph provides information about the faciallingual penetration. These radiographs help determine the correctness of the penetration angle and its proximity to the elusive canal. The LN bur (Caulk/ Dentsply, Tulsa, OK, USA), the Mueller bur (Brasseler, Savannah, GA, USA) and thin ultrasonic tips are especially useful for locating calcified root canals. Locating canals and initial penetration under the microscope is aided by fine instrument like the Micro-Orifice Opener (Dentsply Maillefer, Ballaigues, Switzerland). An examination of the floor of the pulp chamber offers clues to the location of orifices and to the type of canal system present. When there is only one canal, it is usually located in the center of the access preparation. All such orifices particularly if oval in shape must be thoroughly explored with apically precurved small Ktype files to determine if more than one canal is present. If only one orifices is found that is not in the center of the preparation, it is probable that another is present and one should be searched for on the opposite side. The relationship of the two orifices to each other is also significant. The closer they are to each other the greater the chance that the two canals join at some point within the body of the root. The direction that a file takes upon introduction into an orifices is also important. If the initial file placed into the distal canal of a mandibular molar for example points to either the buccal or lingual, one should suspect a second canal. If two canals are present each will be smaller than a single canal. Whenever a root contains two canals which join, the palatal/lingual canal is generally the one with straight line access to the apex. This anatomy is best treated by preparing and obturating the palatal/lingual canal to the apex and the buccal canal to the point of juncture (90). If both canals are enlarged to the apex, an ‘hourglass’ preparation results. The point at which the two canals join would be more constricted than the preparation at the apex. Filling such a situation leaves voids in the apical third and invites failure particularly if bacteria remain in the canal. Rotary nickel titanium files must also be used with caution when this type of anatomy is present because instrument separation can occur as the file transverses the sharp curvature into the common part of the canal. When one canal separates into two, the division is buccal and lingual with the lingual canal generally splitting from the main canal at a sharp angle; sometimes at nearly a right angle (Fig. 11). Slowey (91) recommends ‘that it is helpful to visualize this canal configuration as a lower case letter ‘h’. The buccal canal would be the straight line portion of the letter ‘h’ whereas the lingual canal exists about midroot at a sharp angle from the straight buccal canal.’ This necessitates a modification in access toward the lingual in order to achieve unobstructed passage of instruments into the lingual canal (91). Maxillary molars generally have three roots and can have as many as three mesial canals, two distal canals and two palatal canals. The mesiobuccal root of the maxillary first molar has generated more research and clinical investigation than any root in the mouth. It generally has two canals but a third canal has been reported. When there are two, they are called mesiobuccal (MB-1) and second mesiobuccal (MB2). Go¨rduysus et al. (7) studied the location and pathway of the MB-2 canal in maxillary first and second molars using the DOM and found that the location of this canal varies greatly. It was consistently located mesial to or directly on a line between the MB-1 and the palatal orifices (Fig. 12), within 3.5 mm palatally Fig. 8. Diagrammatic representation of Vertucci’s canal configurations. Root canal morphology 11

Table 3. Classification and percentage of root canals of the maxillary teethn Teeth No. of teeth Type I, 1 canal Type II, 2-1 canals Type III, 1-2-1 canals Total with one canal at apex Type IV, 2 canals Type V, 1-2 canals Type VI, 1-2-1 canals Type VII, 1-2-1-2 canals Total with two canals at apex Type VIII, 3 canals Total with three canals at apex Maxillary central 100 100 0 0 100 0 0000 00 Maxillary lateral 100 100 0 0 100 0 0000 00 Maxillary canine 100 100 0 0 100 0 0000 00 Maxillary first premolar 400 8 18 0 26 62 7 0 0 69 5 5 Maxillary second premolar 200 48 22 5 75 11 6 5 2 24 1 1 Maxillary first molar Mesiobuccal 100 45 37 0 82 18 0 0 0 18 0 0 Distobuccal 100 100 0 0 100 0 0000 00 Palatal 100 100 0 0 100 0 0000 00 Maxillary second molar Mesiobuccal 100 71 17 0 88 12 0 0 0 12 0 0 Distobuccal 100 100 0 0 100 0 0000 00 Palatal 100 100 0 0 100 0 0000 00 nResults published previously in: Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1984: 58:589–599. Vertucci 12

Table 4. Classification and percentage of root canals of the mandibular teethn Teeth No. of teeth Type I, 1 canal Type II, 2-1 canals Type III, 1-2-1 canals Total with one canal at apex Type IV, 2 canals Type V, 1-2 canals Type VI, 1-2-1 canals Type VII, 1-2-1-2 canals Total with two canals at apex Type VIII, 3 canals Total with three canals at apex Mandibular central incisor 100 70 5 22 97 3000300 Mandibular lateral incisor 100 75 5 18 98 2000200 Mandibular canine 100 78 14 2 94 6000600 Mandibular first premolar 400 70 0 4 74 1.5 24 0 0 25.5 0.5 0.5 Mandibular second premolar 400 97.5 0 0 97.5 0 2.5 0 0 2.5 0 0 Mandibular first molar Mesial 100 12 28 0 40 43 8 10 0 59 1 1 Distal 100 70 15 0 85 5 8 2 0 15 0 0 Mandibular second molar Mesial 100 27 38 0 65 26 9 0 0 35 0 0 Distal 100 92 3 0 95 4100500 nResults published previously in: Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1984: 58:589–599. Root canal morphology 13

and 2 mm mesially from the MB-1 orifices. Not all MB2 orifices lead to a true canal. An ‘apparent’ MB-2 canal could not be traced far beyond the orifices in 16% of the teeth. Negotiation of the MB-2 canal is often difficult due to a ledge of dentine that covers its orifices, the mesiobuccal inclination of its orifices on the pulpal floor (Fig. 13A) and its pathway which often takes one or two abrupt curves in the coronal part of the root. Most of these obstructions can be eliminated by ‘troughing or countersinking’ with ultrasonic tips mesially and apically along the mesiobuccal-palatal groove (Fig. 13B). This procedure causes the canal to shift mesially necessitating moving the access wall further mesially. Troughing may have to extend 0.5–3 mm deep. Care must be taken to avoid furcal wall perforation of this root as a concavity Fig. 9. Diagrammatic representation of Gulabivala et al.’s supplemental canal configurations to those of Vertucci. Table 5. Case reports of apical canal configurations for maxillary anterior and premolar teeth Authors Tooth 1 canal 2 canals 4 canals Mangani and Ruddle (32) Central incisor – – X Todd (33) Central incisor – X – Genovese and Marsico (34) Central incisor – X – Sinai and Lustbader (35) Central incisor – X – Von der Vyver and Traub (36) Central incisor – X – Cabo-Valle and Gonzalez-Gonzalez (37) Central incisor – X – Mader and Konzelman (38) Central incisor – X – Pecora et al. (39) Lateral incisor – X – Thompson et al. (40) Lateral incisor Xn – – Fabra-Campos (41) Lateral incisor – X – Christie et al. (42) Lateral incisor – X – Walvekar and Behbehani (43) Lateral incisor – – X Collins (44) Lateral incisor – X – Soares and Leonardo (45) Maxillary first premolar – – X Soares and Leonardo (45) Maxillary second premolar – – X Ferreira et al. (46) Maxillary second premolar – – X Barkhordar and Sapone (47) Maxillary second premolar – – X Low (48) Maxillary second premolar – – X nTwo canals join into one. Vertucci 14

exists on its distal surface. Apical to the troughing level the canal may be straight or curve sharply to the distobuccal, buccal or palatal. Mandibular molars usually have two roots. However, occasionally three roots are present with two or three canals in the mesial and one, two, or three canals in the Table 6. Case reports of apical canal configurations for maxillary molar teeth Authors Tooth 1 canal 2 canals 4 canals Bond et al. (49) Mesiobuccal first molar – – Case report Beatty (50) Mesiobuccal first molar – X – Maggiore et al. (51) Mesiobuccal first molar – X – Cecic et al. (52) Mesiobuccal first molar – X – Baratto-Filho et al. (53) Mesiobuccal first molar – X – Wong (54) Mesiobuccal first molar – X – Martinez-Berna et al. (55) Distobuccal first molar 3 – Hu¨lsmann (56) Distobuccal first molar X – Bond et al. (49) Distobuccal first molar – X – Beatty (50) Distobuccal first molar X – – Maggiore et al. (51) Distobuccal first molar X – – Cecic et al. (52) Distobuccal first molar X – – Baratto-Filho et al. (53) Distobuccal first molar X – – Wong (54) Distobuccal first molar X – – Martinez-Berna et al. (55) Palatal first molar 3 – – Hu¨lsmann (56) Palatal first molar X – – Bond et al. (49) Palatal first molar Xn – – Beatty (50) Palatal first molar X – – Maggiore et al. (51) Palatal first molar – – X Cecic et al. (52) Palatal first molar – X – Baratto-Filho et al. (53) Palatal first molar – X – Wong (54) Palatal first molar – – X Thews et al. (57) Palatal first molar – 2 – Benenati (58) Mesiobuccal second molar X – – Fahid and Taintor (59) Mesiobuccal second molar X – – Benenati (58) Distobuccal second molar X – Fahid and Taintor (59) Distobuccal second molar – X – Benenati (58) Palatal second molar – X – nTwo canals join into one. Root canal morphology 15

distal root (Table 8). De Moor et al. (92) reported that mandibular first molars occasionally have an additional distolingual root (radix entomolaris, RE). The occurrence of these three-rooted mandibular first molars is less than 3% in African populations, 4.2% in Caucasians, less than 5% in Eurasian and Asian populations and higher than 5% in populations with Mongolian traits. The distal surface of the mesial root and mesial surface of the distal root have a root concavity which makes this wall very thin. Overzealous instrumentation of the concavity can lead to a strip perforation of the root. A middle mesial (MM) canal is sometimes present in the developmental groove between MB and ML canals (Fig. 14). The incidence of occurrence of a MM canal ranges from 1% (13) to 15% (93). It must always be looked for during access preparation. A bur is used to remove any protuberance from the mesial axial wall which would prevent direct access to the developmental groove between MB and ML orifices. With magnification, this developmental groove should be carefully explored with the sharp tip of an endodontic explorer. If a depression or orifices is located, the groove can be troughed with ultrasonic tips at the expense of its mesial aspect until a small file can negotiate this intermediate canal. The canals in the distal root are the distal (D) if there is one canal and the distobuccal (DB), distolingual (DL) and middle distal (MD) canal if there are more than one canal. The C-shaped canal configuration was first reported by Cooke and Cox (94). While most C-shaped canals occur in the mandibular second molar, they have also been reported in the mandibular first molar, the maxillary first and second molars and the mandibular first premolar. C-shaped mandibular molars are so named for the cross-sectional morphology of its root and root canal. Instead of having several discrete orifices, the pulp chamber of the C-shaped molar is a single ribbon-shaped orifices with a 1801 arc (or more), starting at the mesiolingual line angle and sweeping around either the buccal or lingual to end at the distal aspect of the pulp chamber. Below the orifices level, the root structure of a C-shaped molar can harbor a wide range of anatomic variations. ‘These can be classified into two basic groups: (1) those with a single, ribbonlike, C-shaped canal from orifices to apex and (2) those with three or more distinct canals below the usual Cshape orifices.’ Fortunately C-shaped molars with a single swath of canal are the exception rather that the rule. More common is the second type of C-shaped canal, with its discrete canals having unusual forms (94). There is significant ethnic variation in the incidence of C-shaped molars. This anatomy is much more common in Asians, than in Caucasians. Investigations in Japan and China showed a 31.5% incidence of Cshaped canals (95–96). Haddad et al. (97) found a 19.1% rate in Lebanese subjects while Seo and Park Table 7. Case reports of apical canal configurations for mandibular anterior and premolar teeth Authors Tooth 1 canal 2 canals 3 canals 4 canals Funato et al. (60) Central incisor – X – D’Arcangelo et al. (61) Canine – X – Orguneser and Kartal (62) Canine – Xn – Heling et al. (63) Canine – – X Holtzman (64) Second premolar – – – X El Deeb (65) Second premolar – – X – Ro¨dig and Hu¨lsmann (66) Second premolar – – X – Bram and Fleisher (67) Second premolar – – – X Rhodes (68) Second premolar – – – X Macri and Zmener (69) Second premolar – – – Xw nThree canals join into two. wFive canals join into four. Vertucci 16

(98) found that 32.7% of Korean’s had C-shaped mandibular second molars. Although the C-shaped canal anatomy creates considerable technical challenges, the use of the DOM, sonic and ultrasonic instrumentation and thermoplastic obturation techniques have made treatment more predictable. Apical region of the root The classic concept of apical root anatomy is that there exists three anatomic and histologic landmarks namely the apical constriction (AC), the cemento-dentinal junction (CDJ) and the apical foramen (AF). The anatomy of the root apex as described by Kuttler (99) (Fig. 15) shows the root canal tapering from the canal orifices to the AC which is generally 0.5–1.5 mm inside the AF. It is generally considered to be the part of the root canal with the smallest diameter. It is the reference point most often used by dentists as the apical termination of shaping, cleaning and obturation procedures. The CDJ is the point in the canal where cementum meets dentine. It is the point where pulp tissue ends Table 8. Case reports of apical canal configurations for mandibular molar teeth Authors Tooth 1 canal 2 canals 3 canals 4 canals Beatty and Krell (70) Mesial first molar – – X – Martinez-Berna and Badanelli (71) Mesial first molar – – X – Fabra-Campos (72) Mesial first molar – – X – Baugh and Wallace (73) Mesial first molar – Xn – – Ricucci (74) Mesial first molar – Xn – – DeGrood and Cunningham (75) Mesial first molar – Xn – – Jacobsen et al. (76) Mesial first molar – Xn X X Reeh (77) Mesial first molar –––X Ricucci (74) Distal first molar X – – DeGrood and Cunningham (75) Distal first molar – Xn – – Martinez-Berna and Badanelli (71) Distal first molar Xw Xn – – Beatty and Krell (70) Distal first molar – X – – Reeh (77) Distal first molar – – X – Beatty and Interian (78) Distal first molar – – X – Friedman et al. (2) Distal first molar – – X – Stroner et al. (79) Distal first molar – – X – Wells and Bernier (80) Distal second molar X – – – Beatty and Krell (70) Distal second molar – – X – Beatty and Krell (70) Distal second molar – X – – Wells and Bernier (80) Distal second molar Xz ––– nThree canals join into two. wThree canals join into one. zMesial and distal canals join. Root canal morphology 17

and periodontal tissues begin. Its location in the root canal is highly variable. It generally is not the same area as the AC and is not a fixed point in population of different countries (100). Smulson et al. (101) estimated that the CDJ is located approximately 1.0 mm from the AF. From the AC or minor diameter (102) the canal widens as it approaches the AF or major diameter. The shape of the space between the major and minor diameters has variously been described as funnelshaped, hyperbolic or ‘morning glory’. The mean distance between the major and minor diameters has been determined to be 0.5 mm in a young person and 0.67 mm in an older individual. The increased length in older individuals is due to the increased buildup of cementum. The AF is the ‘circumference or rounded edge, like a funnel or crater, that differentiates the termination of the cemental canal from the exterior Fig. 10. Comparison in size of the pulps of two mandibular first molars at different ages. (A) Age, 7 years. The pulp chamber is large. (B) 55 years. The pulp chamber is greatly reduced in size through reparative dentin formation mainly on the pulpal floor. Fig. 11. Mesial view of a mandibular premolar with Vertucci Type V canal configuration. Lingual canal separates from main canal at nearly a right angle necessitating widening of the access to the lingual. This should be preformed utilizing the DOM. Fig. 12. Diagrammatic representation of position of MB2 canal orifi in maxillary molars. Fig. 13. Diagrammatic representation of the orientation of MB-2 orifice before (A) and after (B) troughing procedure. Removing obstructions facilitates access into this orifice. Fig. 14. Mandibular first molar access with three mesial canals. Approximately half of the middle mesial canals terminate in a separate foramen. Vertucci 18

surface of the root’. Kuttler (99) determined that the diameter of the AF in individuals in the age range of 18– 25 was 502 mm and in those over 55 years of age was 681 mm, demonstrating its growth with age. The AF does not normally exit at the anatomic apex but is offset 0.5–3.0 mm. This variation is more marked in older teeth through cementum apposition. Studies have demonstrated that the AF coincides with the apical root vertex 17–46% of the time (12–16). Ponce and Vilar Fernandez (103) evaluated serial histologic sections of maxillary anterior teeth to determine the location and diameter of the CDJ and the diameter of the AF. They found that the extension of cementum from the AF into the root canal differed considerably on opposite canal walls. Cementum reached the same level on all canal walls only 5% of the time. The greatest extension generally occurred on the concave side of the canal curvature. This variability reconfirmed that the CDJ and AC are generally not the same area and that the CDJ should be considered just a point at which two histologic tissues meet within the root canal. The diameter of the canal at the CDJ was highly irregular and was determined to be 353 mm for maxillary centrals, 292 mm for lateral incisors and 298 mm for canines. Mizutani et al. (104) prepared serial cross-sections of 90 maxillary anterior teeth and found that the root apex and main AF coincided in 16.7% of central incisors and canines and in 6.7% of lateral incisors. Both the root apex and AF of the central incisors and canines were displaced distolabially while those of the lateral incisors were displaced distolingually. The perpendicular disFig. 15. Morphology of the root apex. From its orifice, the canal tapers to the apical constriction or minor diameter which is generally considered the narrowest part of the canal. From this point the canal widens as it exits the root at the apical foramen or major diameter. The space between the minor and major diameters is funnel shaped. Table 9. Mean perpendicular distance from the root apex to the apical constriction and both mesiodistal and labiolingual diameters at the constrictionn Teeth Mesiodistal (mm) Labiolingual (mm) Vertical (mm) Central incisor 0.370 0.428 0.863 Lateral incisor 0.307 0.369 0.825 Canine 0.313 0.375 1.010 nResults published previously in: Mizutani T, Ohno N, Nakamura H. Anatomical study of the root apex in the maxillary anterior teeth. J Endod 1992: 18(7): 344–347. Table 10. Size of main apical foraminan Teeth Mean values (u) Maxillary incisors 289.4 Mandibular incisors 262.5 Maxillary premolars 210.0 Mandibular premolars 268.25 Maxillary molars Palatal 298.0 Mesiobuccal 235.05 Distobuccal 232.20 Mandibular molars Mesial 257.5 Distal 392.0 nResults published previously in: Morfis A, Sylaras SN, Georgopoulou M, Kernani M, Prountzos F. Study of the apices of human permanent teeth with the use of a scanning electron microscope. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1994: 77(2):172–176. Root canal morphology 19

tance from the root apex to the AC and both mesiodistal and labiolingular root canal diameters at the AC are shown in Table 9. The labiolingual diameter in all maxillary anterior teeth is approximately 0.05 mm larger than the mesiodistal diameter. This has definite implications on shaping and cleaning procedures as only the mesiodistal diameter is evident on the radiograph. Morfis et al. (105) studied the apices of 213 permanent teeth with the use of a scanning electron microscope and determined the number and size of AF, its distance from the anatomic apex, and the size of accessory foramina. More than one main AF was observed in all teeth except for the palatal root of maxillary molars and the distal root of mandibular molars. Twenty-four percent of maxillary premolars and 26% of maxillary incisors showed no main AF. The mesial roots of mandibular molars (50%), the maxillary premolars (48.3%) and the mesial root of maxillary molars (41.7%) showed the highest percentage of multiple AF. This finding is consistent with observations that blunted roots usually have more than one root canal. The mean values of the size of the main AF are listed in Table 10. They varied from 210 mm for the maxillary premolars to 392 mm for the distal roots of mandibular molars. All groups of teeth demonstrated at least one accessory foramen. The maxillary premolars had the largest number and size of accessory foramen (mean value 53.4 mm) and the most complicated apical morphologic makeup. This was followed closely by the mandibular premolars and may be a reason why root canal therapy may fail in this group of teeth. Briseno Marroquin et al. (106) investigated the apical anatomy of 523 maxillary and 574 mandibular molars from an Egyptian population by means of a computeraided stereomicroscope (
40 magnification). The most common physiological foramen (apical constriction) shape was oval (70%); the mean of the narrow and wide physiological foramen diameters was 0.20– 0.26 mm in mandibular molars, 0.18–0.25 mm in maxillary mesio-buccal and distobuccal roots and 0.22–0.29 mm in the maxillary palatal root. There was a high percentage of two physiological foramina in mesial (87%) and mesiobuccal (71%) roots of mandibular and maxillary first molars, respectively; there was a high frequency of accessory foramina in maxillary mesiobuccal (33%) and mandibular mesial (26%) roots. Mjo¨r et al. (107,108), found tremendous variation in the morphology of the apical root including numerous Table 11. Median canal diameter (in mm) at 1, 2 and 5 mm from the apexn Buccal/lingual Mesial/distal Tooth (canal) Position 1 mm 2 mm 5 mm 1 mm 2 mm 5 mm Maxillary Central Incisor 0.34 0.47 0.76 0.30 0.36 0.54 Lateral Incisor 0.45 0.60 0.77 0.33 0.33 0.47 Canine 0.31 0.58 0.63 0.29 0.44 0.50 Premolar Single canal 0.37 0.63 1.13 0.26 0.41 0.38 Bucccal 0.30 0.40 0.35 0.23 0.31 0.31 Palatal 0.23 0.37 0.42 0.17 0.26 0.33 Molar Single Mesiobuccal 0.43 0.46 0.96 0.22 0.32 0.29 1st Mesiobuccal 0.19 0.37 0.46 0.13 0.27 0.32 2nd Mesiobuccal 0.19 0.31 0.38 0.16 0.16 0.16 Distobuccal 0.22 0.33 0.49 0.17 0.25 0.31 Palatal 0.29 0.40 0.55 0.33 0.40 0.74 Mandibular Incisor 0.37 0.52 0.81 0.25 0.25 0.29 Canine 0.47 0.45 0.74 0.36 0.36 0.57 Premolar Single 0.35 0.40 0.76 0.28 0.32 0.49 Buccal 0.20 0.34 0.36 0.23 0.29 0.41 Palatal 0.13 0.32 0.37 0.18 0.21 0.17 Molar Single Mesial 0.45 0.80 2.11 0.22 0.30 0.29 Mesiobuccal 0.40 0.42 0.64 0.21 0.26 0.32 Mesiolingual 0.38 0.44 0.61 0.28 0.24 0.35 Distal 0.46 0.50 1.07 0.35 0.34 0.59 nResults published previously in: Wu MK, R’Oris A, Barkis D, Wesselink P. Prevalence and extent of long oval canals in the apical third. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000: 89(6):739–743. Vertucci 20

accessory canals, areas of resorption and repaired resorption, attached, embedded and free pulp stones and varied amounts of irregular secondary dentine. Primary dentinal tubules were found less frequently than in coronal dentine and were more or less irregular in direction and density. Some areas were completely devoid of tubules. Fine tubular branches (300–700 mm in diameter) which run at 451 to the main tubules and microbranches (25–200 mm diameter) which run at 901 to the main tubules were frequently present. This variable structure in the apical region presents challenges for root canal therapy. Obturation techniques which rely on the penetration of adhesives into dentinal tubules may not be successful. These authors concluded that the hybrid layer may become a very important part of adhesive systems in the apical part of the root canal. Although debated for decades, there is considerable controversy concerning the exact termination point for root canal therapy procedures (109–110). Clinical determination of apical canal morphology is difficult at best. The existence of an AC may be more conceptual than actual. Dummer et al. (111) determined that a traditional single AC was present less than half the time. Frequently, the apical root canal is tapered or parallel or contained multiple constrictions. Other authors (112– 113) have suggested that an apical constriction is usually not present, particularly when there is apical root resorption and periradicular pathology. Weine (114) recommends the following termination points for therapy: 1 mm from the apex when there is no bone or root resorption; 1.5 mm from the apex when there is only bone resorption and 2 mm from the apex when there is bone and root resorption. Wu et al. (115) feel that it is difficult to locate the AC and AF clinically and that the radiographic apex is a more reliable reference point. These authors recommend that root canal procedures terminate 0–3 mm from the radiographic apex depending upon the pulpal diagnosis. For vital cases, clinical and biologic evidence (116–117) indicates that a favorable point to terminate therapy was 2–3 mm short of the radiographic apex. This leaves an apical pulp stump which prevents the extrusion of irritating filling materials into the periradicular tissues. With pulp necrosis, bacteria and their byproducts may be present in the apical root canal and jeopardize healing. In these cases, a better success rate was achieved (116–117) when therapy ended at or within 2 mm of the radiographic apex. When therapy ended shorter than 2 mm or extended past the radiographic apex, the success rate decreased by 20%. For retreatment cases, therapy should extend to or preferably 1–2 mm short of the radiographic apex to prevent overextension of instruments and filling materials into the periradicular tissues. Langeland (118–121) and Ricucci and Langeland (122) concluded after evaluating apical and periradicular tissues following root canal therapy, that the most favorable prognosis was obtained when procedures were terminated at the AC while the worst was obtained when working beyond the AC. The second worst prognosis occurred when procedures were terminated more than 2 mm from the AC. These findings occurred in vital and necrotic tissue and when bacteria were present beyond the AF. The presence of sealer and/or gutta-percha into the periradicular tissues, into lateral canals and into apical ramifications always produced a severe inflammatory reaction (123– 125). These authors, however, admit that it is difficult at best to clinically locate the AC. Finally, Schilder (126) recommended a termination point for all therapy at or beyond the radiographic apex and advocated the filling of all apical ramifications and lateral canals. The apical limit of instrumentation and obturation continues to be one of the major controversies in root canal therapy. A hallmark of the apical region is its variability and unpredictability. Because of the tremendous variation in canal shapes and diameters there is concern about a clinicians ability to shape and clean canals in all dimensions. The ability to accomplish this depends upon the anatomy of the root canal system, the dimensions of canal walls and the final size of enlarging instruments. The initial file that explores canal anatomy and binds in the canal is sometimes used as a measure of apical root canal diameter. Attempting to gauge the size of oval-shaped apical root canals, Wu et al. (127) demonstrated that in 75% of the cases the initial file contacted only one side of the apical canal wall; in the remaining 25% the instrument failed to contact any wall. In 90% of the canals, the diameter of the initial instrument was smaller than the short diameter of the canal. Consequently, using the first file to bind for gauging the diameter of the apical canal and as guidance for apical enlargement is not reliable. Leeb (128) recognized this problem and determined that it could be remedied by removing the interferences in the Root canal morphology 21

coronal and middle thirds of the canal. Contreras et al. (129) concluded that radicular flaring before canal exploration removed interferences and increased the initial file size that was snug at the apex (almost two file sizes greater). Early flaring gives the dentist a better sense of apical canal size so that better decisions can be made concerning the appropriate final diameter needed for apical shaping and cleaning. Gani and Visvisian (130) compared the shape of the apical portion of the root canal system of maxillary first molars with the D0 diameter of endodontic instruments and found that correlations between maximum canal diameters and instrument diameters were highly variable. Evaluation of the root canal diameter showed that a circular shape (both diameters are equal) predominates in the palatal and MB-2 canals; a flat shape (largest diameter exceeds the smallest by more than the radius) occurs most often in the MB-1 canal; both circular and flat shapes are found in the distobuccal canal. Flat and ribbon shaped canals persist near the apex even in elderly patients and mainly in the MB-1 canal. This finding was believed to be due to the concentric narrowing of ribbon shaped canals primarily along their smallest diameter. Oval canals narrow mainly along their largest diameter and tend to become circular. These authors concluded that the maxillary first molar shows a very complicated canal shape at the apical limit of its canal system and this anatomy makes shaping, cleaning and obturation difficult. This is particularly true of the MB-1 and distobuccal canals. Because of this great variability it was virtually impossible for them to establish guidelines for instrument calibers that would guarantee adequate canal preparation. Wu et al. (131) studied the apical root canal diameters and tapers of each tooth group and demonstrated that root canals are frequently long oval or ribbon-shaped in the apical 5 mm (Table 11). These authors defined a long oval canal as one that has a ratio of long to short canal diameter that is greater than 2. This type of canal morphology was found to occur in 25% of the crosssections studied. They have a buccal/lingual diameter which is larger than its mesial/distal diameter. This was found to be true for all canals except the palatal canal of maxillary molars. The canal measurements suggest that apical preparations need to be taken to larger sizes than previously recommended (132). These authors concluded that ‘because of long oval canals, larger canal tapers in the buccal-lingual direction, wider ranges in the apical diameters of canals, and the lack of technology to measure these diameters, it is very difficult if not impossible to adequately debride all canals by instrumentation alone.’ This fact was further emphasized by Wu and Wesselink (133) when they reported uninstrumented extensions in 65% of oval canals prepared with files utilizing the balanced force technique and by Rodig et al. (134) who determined that nickel–titanium rotary instruments did not allow controlled preparation of the buccal and lingual extensions of oval canals. The instruments created a round bulge in the canal leaving the extensions unprepared and filled with smear layer and debris. The complete shaping and cleaning of root canals is often difficult to achieve because of variations in canal cross-sectional shapes (135–137) and the presence of canal irrigularities and curvatures. Stainless steel hand files and tapered nickel–titanium rotary files are currently used for root canal enlargement. Excessive flaring with these instruments particularly in curved roots pose the danger of thining or perforating the root canal wall on the concave surface of a root (138). Furthermore, the risk of iatrogenic mishaps increase because root canals tend to be closer to the inner (concave) part of curved roots (139–140). Abou-Rass et al. (141) recommended ‘anticurvature filing’ when preparing curved canals. ‘This is a controlled and directed canal preparation into the bulky portions or safety zones and away from the thinner portions or danger zones of root structure where root perforation or stripping of the canal walls can occur.’ Lim and Stock (142) compared anticurvature filing using the step back technique with a standard circumferential step back method in curved molar root canals and showed that anticurvature filling reduces the risk of perforation through the furcal or curved root surface. These authors designated that an arbitrary value of 0.3 mm of dentine is the minimal canal wall thickness that should remain after preparation inorder to provide sufficient resistance to obturation forces and to forces exerted during function. Gluskin et al. (143) showed that canal shapes prepared with nickel–titanium rotary GT files (Dentsply-Tulsa Dental, Tulsa, USA) were better centered and conserved more dentine in the danger zone region of curved molars than hand instruments. Garala et al. (144) determined that significant differences in remaining canal wall thickness were not present when either the ProFile rotary system (Maillefer) or the Hero 642 system Vertucci 22

(Micromega, Besancon, France) were used according to manufacturers directions. Canal wall structure removed during preparation never exceeded 60%. Neither system over-prepared canals or compromised the integrity of the root by excessive removal of the canal wall. However, the authors found that the apical preparations showed the least amount of preparation. Many apical and coronal preparations were seen where only a portion of the canal wall was instrumented. Further apical canal enlargement seems necessary inorder to incorporate the original canal into the final preparation. Peters et al. (145–146) came to similar conclusions in studying the effect of five nickel– titanium rotary instrumentation systems on canal debridement. They found that all techniques left 35% or more of the canal surface area unchanged. All of these results are fairly predictable considering the highly variable and unfriendly environment that the root canal system provides and the current state of endodontic intracanal instruments which are unable to contact all of the recesses present along canal walls. They do a good job in shaping the canal but a poor job in accomplishing total canal debridement. When attempting to find better ways to clean and sterilize root canals, Card et al. (147) determined that enlarging canals above the traditional recommended apical sizes was the only way to effectively remove culturable bacteria from the canal. The larger apical sizes optimized irrigation and disinfection and facilitated the mechanical elimination of microbes. Usman Fig. 16. (A) X-section of mandibular anterior tooth showing pulp remnants remaining in recesses of root canal walls in apical 1 mm. Rotary nickel titanium preparation (size 40, 0.08 taper) and manual irrigation [6% NaOCL and RC prep (Premier)]. (B) Electron photomicroscopy of canal wall in (A) illustrating much debris. (C) X-section of mandibular anterior tooth showing clean canal walls in the apical 1 mm following rotary nickel titanium preparation (size 40, 0.08 taper) and sonic accoustic irrigation with 6% NaOCL. Fig. 17. Leakage through dentinal tubules originating at beveled root surface. (A) Reverse filling does not extend coronally to height of bevel. Arrows indicate potential pathway for fluid penetration. (B) Reverse filling extends coronally to height of bevel and blocks fluid penetration (arrows) into the root canal space. From Vertucci FJ and Beatty RG. Apical leakage associated with retrofilling technique: a dye study. J Endod 1986: 12(8): 335. Root canal morphology 23

et al. (148) similarly concluded that an increase in size of canal instrumentation at working length produced an increase in canal cleanliness. However, irrigant volume, number of instrument changes and depth of penetration of irrigant needles had a much less effect on canal debridement. The price of increasing apical canal diameter may be procedural errors and/or root fractures. As a supplement to these techniques, acoustic microstreaming by sonic and ultrasonic irrigation appears to have a positive effect on the cleanliness of oval canals as demonstrated by Lumley et al. (149) and Jurecko et al. (150) (Fig. 16). However, further research needs to be conducted to determine the best treatment procedures for a highly variable root canal system. Peters et al. (151) recently demonstrated a detailed three-dimensional model of the pulp cavity obtained by means of high-resolution computed tomography. This method holds great promise for further increasing our knowledge of root canal anatomy. Studying maxillary molars, these authors determined the volume, area and dimensions of the root canal systems. The mean canal diameters in the apical 0.5 mm were 188  5, 174  12 and 318  23 mm for the mesiobuccal (MB-1), distobuccal and palatal canals. Such information goes a long way toward helping us establish final instrumentation sizes for cleaning and shaping procedures. Taken together, the in vivo studies and case reports discussed above underline the importance of a thorough knowledge of dental anatomy for non-surgical root canal treatment. However, the natural anatomy is altered during surgical procedures and additional anatomic features need to be addressed. As a result of their studies on apical anatomy, Morfis et al. (105) concluded that beveling the root apex 2–3 mm during surgical procedures removes the vast majority of unprepared and unfilled accessory canals and thereby eliminates the possibility of failure. This finding agrees with the results of Kim et al. (152) who determined that the amount of apical root resection depends upon the incidence of accessory and apical ramifications at the root end. Using a bevel perpendicular to the long axis of a root, they found that the removal of 1 mm of apex eliminated 52% of apical ramifications and 40 % of accessory canals. Removal of 2 mm of apex eliminated 78% of apical ramifications and 86% of the accessory canals. Removal of 3 mm eliminated 98% of apical ramifications and 93% of accessory canals. Consequently apical resections of 3 mm are most effective for eliminating the majority of these structures. During apical root resection, a bevel perpendicular to the long axis of a root exposes a small number of microtubules (107–108). However, a 451 bevel exposes a significantly greater number. Vertucci and Beatty (153) theorized that beveling the root apex at such an angle increases the number of dentinal tubules and the chance of leakage into and out of the root canal. To prevent this from occurring, they recommended that retropreparations extend coronally to the height of the bevel (Fig. 17). Tidmarsh and Arrowsmith (154) corroborated their theory by examining the root ends of developed roots with a scanning electron microscope. The root apex houses a variety of anatomic structures and tissue remnants. If surgery becomes necessary, an apical root resection can alter canal anatomy. Intercanal connections can become exposed and a single foramen may become multiple foramina. Results will be poor if this altered anatomy is not recognized and treated. Fig. 18. (A) Complete isthmus on beveled root surface between two canals. (B) Isthmus has become part of the retropreparation which should have a uniform depth of 3 mm. Fig. 19. Types of canal isthmi. Vertucci 24

Wada et al. (155) evaluated the root apex of teeth with refractory apical periodontitis that did not respond to root canal therapy. They removed the root end and found that 70% contained significant apical ramifications. This frequency is highly suggestive of a close relationship between the anatomical complexity of the root canal system, persisting intracanal bacteria and the failure of periradicular pathology to heal (156–158). Cambruzzi and Marshall (159) called an intercanal connection or transverse anastomosis an ‘isthmus’ and stressed the importance of preparing and filling it during surgery. An isthmus is a narrow, ribbon-shaped communication between two root canals that contains pulp or pulpally derived tissue. It can also function as a bacterial reservoir. Any root that contains two or more root canals has the potential to contain an isthmus (Fig. 18). Thus whenever multiple canals are present on a resected root surface an isthmus must be suspected. Cambruzzi and Marshall also advocate the in vivo use of methylene blue dye as an aid in visualizing the outline of the resected root surface and the presence of an isthmus. Weller et al. (160) found that the highest incidence of isthmi in the mesiobuccal root of maxillary first molars occurred 3–5 mm from the root apex. The 4 mm level contained a complete or partial isthmus 100% of this time. The presence of a partial isthmus was reported by Teixeira et al. (161) who found that they occurred more frequently than a complete isthmus. Identification and treatment of isthmi is vitally important for the success of surgical procedures. Hsu and Kim (162) identified five types of isthmi which can occur on a beveled root surface (Fig. 19). Type I Two or three canals with no communications. Type II Two canals with a definite connection between them. Type III Three canals with a definite connection between them Type IV Canals extend into the isthmus area. Type V Is a true connection or corridor throughout the section. Isthmi are found in 15% of anterior teeth, 16% of maxillary premolar teeth at the 1 mm resection level and 52% at the 6 mm resection level. They occur 30% of the time at the 2 mm level in mandibular premolars and 45% at the 3 mm level and 50% at the 4 mm level in the mesiobuccal root of the maxillary first molar. The mesial root of the mandibular first molars contain isthmi 80% of the time at the 3–4 mm resection level while 15% of distal roots have isthmi at the 3 mm level. Microsurgical endodontic techniques have allowed the dentist to visualize the resected root surface and identify the isthmus, prepare it with ultrasonic tips and fill the preparation with acceptable filling materials. The recognition and microendodontic treatment of the canal isthmus is a factor that has significantly reduced the failure rate of endodontic surgery (163–164). In conclusion, outcomes of non-surgical and surgical endodontic procedures are influenced by highly variable anatomic structures. Therefore clinicians ought to be aware of complex root canal structures, of crosssectional dimensions and of iatrogenic alterations of canal anatomy. Careful interpretation of angled radiographs, proper access preparation and a detailed exploration of the interior of the tooth, ideally under magnification, are essential prerequisites for a successful treatment outcome. Acknowledgments From Cohen S, Hargreaves, KM: Pathways of the Pulp, ed. 9, Chapter 7, St. Louis, 2006, Mosby. References 1. Martinez-Lozano MA, Forner-Navarro L, SanchezCortes JL. Analysis of radiologic factors in determining premolar root canal systems. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999: 88: 719–722. 2. Friedman S, Moshonov J, Stabholz A. Five root canals in a mandibular first molar. Dent Traumatol 1986: 2: 226–228. 3. Nattress BR, Martin DM. Predictability of radiographic diagnosis of variations in root canal anatomy in mandibular incisor and premolar teeth. Int Endod J 1991: 24: 58–62. 4. Stropko JJ. Canal morphology of maxillary molars, clinical observations of canal configurations. J Endod 1990: 25: 446–450. 5. Baldassari-Cruz LA, Lilly JP, Rivera EM. The influence of dental operating microscopes in locating the mesiolingual canal orifices. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002: 93: 190–194. 6. Coelho de Carvalho MC, Zuolo ML. Orifice locating with a microscope. J Endod 2000: 26: 532–534. 7. Go¨rduysus MO, Gorduysus M, Friedman S. Operating microscope improves negotiation of second mesiobucRoot canal morphology 25

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128. Leeb J. Canal orifices enlargement as related to biomechanical preparation. J Endod 1983: 9: 463–470. 129. Contreras MA, Zinman EH, Kaplan SK. Comparison of the first file that fits at the apex, before and after early flaring. J Endod 2001: 27: 113–116. 130. Gani O, Visvisian C. Apical canal diameter in the first upper molar at various ages.J Endod 1999: 25: 689–691. 131. Wu M-K, R’oris A, Barkis D, Wesselink PR. Prevalence and extent of long oval canals in the apical third. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000: 89: 739–743. 132. Walton RE, Torabinejad M. Principles and Practice of Endodontics, 3rd edn. Philadelphia: WB Saunders Company, 1996: 213–215. 133. Wu MK, Wesselink PR. A primary observation on the preparation and obturation of oval canals. Int Endod J 2001: 34: 137–141. 134. Ro¨dig T, Hu¨lsmann M, Muhge M, Scha¨fers F. Quality of preparation of oval distal root canals in mandibular molars using nickel–titanium instruments. 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Morphological Measurements of Anatomic Landmarks in Human Maxillary and Mandibular Molar Pulp Chambers Allan S. Deutsch, DMD, and Barry Lee Musikant, DMD The aim of this in vitro study was to measure critical morphology of molar pulp chambers. One hundred random human maxillary and mandibular molars (200 teeth in total) were used. Each molar was radiographed mesiodistally on a millimeter grid. Using a stereomicroscope, the measurements were read to the nearest 0.5 mm. Results were as follows (mean, mm): pulp chamber floor to furcation, maxillary
3.05  0.79, mandibular
2.96  0.78; pulp chamber ceiling to furcation, maxillary
4.91  1.06, mandibular
4.55  0.91; buccal cusp to furcation, maxillary
11.15  1.21, mandibular
10.90  1.21; buccal cusp to pulp chamber floor, maxillary
8.08  0.88, mandibular
7.95  0.79; buccal cusp to pulp chamber ceiling, maxillary
6.24  0.88, mandibular
6.36  0.93; and pulp chamber height, maxillary
1.88  0.69, mandibular
1.57  0.68. The pulp chamber ceiling was at the level of the cementoenamel junction in maxillary, 98%, and mandibular, 97% of the specimens. The measurements showing the lowest percentage variance were buccal cusp to furcation (approximately 11%) and buccal cusp to pulp chamber ceiling (approximately 14%). The measurements were similar for both maxillary and mandibular molars. One of the irreversible complications of endodontics is perforation into the furcation while gaining access to the pulp chamber of molar teeth. Perforations can sometimes be repaired but often result in extraction of the tooth (1). Access preparations are performed by a qualitative method involving the clinician’s tactile perception and knowledge of dental anatomy. However, a reliance on tactile perception alone may lead to undesirable results, including perforation of the pulp chamber (2). Calcification of the pulp cavity may reduce tactile perceptions, possibly leading to perforation of the furcation floor and an iatrogenic failure (3, 4). In this situation, the pulp chamber roof and floor approximate each other, and perforation may result when the bur traverses the relatively thin floor. A review of the dental literature regarding the morphology of the pulp chamber revealed very little information. Comparatively few studies describe the morphology of the furcation as it relates to the floor of the pulp chamber. One study measured the distance from the floor of the pulp chamber to five predetermined sites on the furcation root surface and found it to range from 2.7 to 3.0 mm for both mandibular and maxillary molars (5). Another study reported that the mean distance from the pulp chamber floor to the root separation of maxillary molars was equal to or less than 3 mm in 86% of the teeth measured (6). Clearly, knowledge of the general location and dimensions of the molar pulp chamber may reduce perforations of the chamber during the access process. However, few studies have evaluated external anatomical landmarks as predictors for location of the roof and floor of the pulp chamber. Therefore, the aim of this experiment was to measure key external anatomical landmarks relating to pulp chamber morphology in maxillary and mandibular molars. MATERIALS AND METHODS One hundred random human mandibular and maxillary molars (200 teeth in total) were used in this study. The samples were gathered from oral surgery and denture center practices. No teeth were crowned, but some teeth contained caries, restorations, or both. No tooth was used if the caries and or restorations violated the pulp chamber. The age, gender, and systemic condition of the patients were unknown. Every tooth had a closed apex, and the number of third molars was limited to nine mandibular and 10 maxillary teeth. Each tooth was mounted with wax on a periodontal millimeter X-ray grid. The teeth were mounted perpendicular to the grid in a mesiodistal direction. This is the same radiographic orientation that would be recorded in vivo. The radiographs were taken on the molar setting with a numerical value of 25 (Heliodent; Siemans). Each radiograph was developed in an automatic developer (Air Techniques, Farmingdale, NY). Each radiograph was examined using a Bausch and Lomb (Rochester, New York) stereoscopic microscope using a magnification of 10
. The measurements were recorded to the nearest 0.5 mm. One evaluator examined and made all measurements. JOURNAL OF ENDODONTICS Printed in U.S.A. Copyright © 2004 by The American Association of Endodontists VOL. 30, NO. 6, JUNE 2004 388

A drawing of the location of the measurements for maxillary and mandibular molars can be seen in Fig. 1. Three direct measurements were taken of each tooth. Measurement A represented the distance between the floor of the pulp chamber and the closest point to the furcation. Measurement B was the distance from the ceiling of the pulp chamber to the closest point to the furcation. Measurement C was the distance from the buccal cusp tip to the closest point to the furcation. BA represents the height of the pulp chamber. CA measures the distance from the buccal cusp to the pulp chamber floor and CB represents the distance from the buccal cusp to the pulp chamber ceiling. It was also noted whether the pulp chamber ceiling was located at the level of the cementoenamel junction. RESULTS The mean, SD, and coefficient of variation for each measurement are presented for both maxillary molars (Table 1) and mandibular molars (Table 2). It should be noted that means for all the measurements are very similar. The pulp chamber ceiling was found at the level of the cementoenamel junction in maxillary molars in 98% of the specimens and in mandibular molars in 97% of the specimens. DISCUSSION A review of the endodontic literature contains relatively few studies that actually measure anatomic landmarks relating to the pulp chamber. Great variance in overall molar tooth size, morphology, and arch position may have led to the assumption that the dimensions of the pulp chamber would also show such great variability that these measurements would be clinically useless. In this study, we measured variance as a percentage of the mean (i.e. coefficient of variation [CV]  SD/mean). When comparing both maxillary and mandibular teeth, the range of CV values was 10% to 43%. For both maxillary and mandibular molars, the largest CV values were observed for the pulp chamber height (measurement F in Tables 1 and 2). This intertooth variation in pulp chamber height is probably the result of the biologic process of secondary dentin apposition. Several studies suggest that secondary dentin apposition occurs primarily on the pulp chamber floor instead of the ceiling. For example, one study evaluated ancient and contemporary populations and observed no significant changes in the dentin thickness at the roof of the pulp chamber with increasing age, whereas the dentin at the floor of the pulp chamber showed a definite increase in thickness with increasing age (7). Another study reported a highly significant reduction in the height of the pulp chamber of the mandibular first permanent molar (15%) that was caused mainly by an increase in thickness of the pulpal floor (8). Tidmarsh (9) stated that “the growth of dentin upon the floors of pulp chambers, apparently without cause, is of some significance to the endodontist who must gain entrance to the root canals.” Because this is a radiographic study, it is possible that variation in radiographic measurement versus anatomic measurement could be responsible for variation between groups. However, Scotti et al. (10) demonstrated that the residual error between the anatomic and radiographic measurement was 4.46%, which, when extrapolated to our data, is equivalent to an average difference of 0.12 mm. This number is smaller than all of the measured SDs; thus, we do not believe that this theoretical problem confounds our results. The results of this study agree with the measurements reported in two other studies. Sterrett et al. (5) reported that the average distance from the pulp to the root surface (furcation) was 2.83 mm (SD of 0.49) for mandibular first molars and 2.88 mm (SD of 0.44) for mandibular second molars. Majzoub and Kon (6) measured maxillary molars and found that the distance from the pulp chamber floor to the most coronal aspect of the area of root separation (furcation) on the distal aspect was equal to or less than 3 mm in 86% of the teeth measured. In this study, we reported pulp floor to furcation measurements in maxillary molars of 3.05 mm (SD of 0.79) and in mandibular molars of 2.96 mm (SD of 0.78). Other studies have measured the relation between external landmarks and pulp chamber locations. One study measured the distance from each cusp tip to the corresponding height of the pulp chamber ceiling and reported mean distances for maxillary first molars (5.77 mm), maxillary second molars (5.66), mandibular first molars (6.42 mm), and mandibular second molars (6.24 mm) (11). These values are similar to those obtained in the present study (Tables 1 and 2). The reported measurements in this study and their similarity to measurements from other studies give us a general guideline for a more quantitative approach to endodontic molar access. In general, the distance from the cusp tip to pulp chamber ceiling height is approximately 6.0 mm, the distance from the pulpal floor to the TABLE 2. Mean measurements (mm) for mandibular molars n  100 A B C D  (C  A) E  (C  B) F  (B  A) Mean 2.96 4.57 10.9 7.95 6.36 1.57 SD 0.78 0.91 1.21 0.79 0.93 0.68 % CV 26 20 11.1 9.94 14.6 43 * Values A–F refer to measurement distances illustrated in Fig. 1. (%CV  [SD/Mean] and are a measure of the percent variance observed in the sample. FIG. 1. Location of Measurement for Maxillary and Mandibular Molars. TABLE 1. Mean measurements (mm) for maxillary molars n  100 A* B C D  (C  A) E  (C  B) F  (B  A) Mean 3.05 4.91 11.15 8.08 6.24 1.88 SD 0.79 1.06 1.21 0.88 0.88 0.69 % Variance 25.8 21.6 10.9 10.9 14.11 36.5 * Values A–F refer to measurement distances illustrated in Fig. 1. (%CV  [SD/Mean] and are a measure of the percent variance observed in the sample. Vol. 30, No. 6, June 2004 Pulp Chamber Morphology 389

furcation is approximately 3.0 mm, and the average height of a pulp chamber is 1.5 to 2.0 mm. In addition, the pulp chamber ceiling was found at the level of the cementoenamel junction in 97% to 98% of the maxillary and mandibular molars. This knowledge of pulp chamber morphology should be integrated with an examination of preoperative radiographs (to assess for other potential factors such as taurodontism (12)) and intraoperative tactile perception during endodontic access preparations. Dr. Deutsch and Dr. Musikant are Co-Directors of Dental Research, Essential Dental Laboratories, S. Hackensack, NJ. Address requests for reprints to Dr. Allan S. Deutsch, Essential Dental Laboratories, 89 Leuning Street, South Hackensack, NJ 07606. E-mail: [email protected] References 1. Aguirre R, ElDeeb ME, ElDeeb ME. Evaluation of the repair of mechanical furcation perforations using amalgam, gutta-percha, or Indium foil. J Endodon 1986;12:249–56. 2. Christie WH, Thompson GK. The importance of endodontic access in locating maxillary and mandibular molar canals. J Can Dent Assoc 1994;60: 527–36. 3. Alhadainy HA. Root perforations, a review of literature. Oral Surg, Oral Med, Oral Path 1994;78:368–74. 4. Goon WWY, Lundergan WP. Redemption of a perforated furcation with a multidisciplinary treatment approach. J Endodon 1995;21:576–9. 5. Sterrett JD, Pelletier H, Russell CM. Tooth thickness at the furcation entrance of lower molars. J Clin Periodontol 1996;23:621–7. 6. Majzoub Z, Kon S. Tooth morphology following root resection procedures in maxillary first molars. J Periodontol 1992;63:290–6. 7. Philippas GC. Influence of occlusal wear and age on formation of dentin and size of the pulp chamber. J Dent Res 1961;40:1186–98. 8. Shaw L, Jones AD. Morphological considerations of the dental pulp chamber from radiographs of molar and premolar teeth. J Dent 1984;12:139– 45. 9. Tidmarsh BG. Micromorphology of pulp chambers in human molar teeth. Int Endod J 1980;13:69–75. 10. Scotti R, Villa L, Carossa S. Clinical applicability of the radiographic method for determining the thickness of calcified crown tissues. J Prosthet Dent 1991;65:65–7. 11. Stambaugh RV, Wittrock JW. The relationship of the pulp chamber to the external surface of the tooth. J Prosthet Dent 1977;37:537–46. 12. Tsesis I, Shifman A, Kaufman AY. Taurodontism: an endodontic challenge: report of a case. J Endodon 2003;29:353–5. 390 Deutsch and Musikant Journal of Endodontics

Anatomy of the Pulp-Chamber Floor Paul Krasner, DDS, and Henry J. Rankow, DDS Locating the number and position of orifices on pulp-chamber floors can be difficult. This is especially true when the tooth being treated is heavily restored, malposed, or calcified. After evaluating 500 pulp chambers of extracted teeth, new laws for finding pulp chambers and root-canal orifices are proposed. The use of these laws can aid in the determination of the pulp-chamber position and the exact location and number of root canals in any individual tooth. Endodontic therapy is essentially a surgical procedure, a microneurologic surgical procedure. Because the fundamental foundation on which all surgical procedures are performed is an intimate knowledge of anatomy, any attempt to perform endodontic therapy must be preceded with a thorough understanding of the anatomy of both the pulp chamber and the root-canal system. Attempting to treat the root-canal system without detailed anatomic description would be the equivalent of a physician looking for an appendix without ever having read Gray’s Anatomy. Literature describing pulp-chamber anatomy in the past has been very general and offered little specificity for determining orifice number and location. Discussions, in print and in the classroom, typically present generalizations about the average number of canals in different teeth. However, the average number of canals in a tooth is of no value when dealing with an individual tooth. Likewise, the description of the location of canal orifices has often been presented in a nonsystematic manner. Essentially, most advice has been to make an access in an appropriate position in the clinical crown and look for the orifices in the hope that they are seen. If they are not easily seen, there is little guidance for safely locating them without the danger of excessive tooth destruction or even perforation. As any experienced operator knows, looking for root-canal orifices in teeth that are heavily restored, cariously broken down, or gouged by previous accessing is very difficult. In these cases, normal anatomy is often severely distorted and the advice given in articles and textbooks is of little value We felt, after accessing thousands of teeth in our practices, that there are consistent, identifiable, anatomic configurations of the pulp chamber and the pulp-chamber floor. This study was undertaken to observe the anatomy of the pulp chamber and the pulpchamber floor and to see if specific, consistent landmarks or configurations exist and are quantifiable. If these landmarks exist, then the task of locating orifices can be made more systematic and, therefore, with greater certainty. This could aid in a rational approach to root-canal therapy. MATERIALS AND METHODS A total of 500 extracted, permanent, human teeth were used. The teeth were equally distributed between maxillary and mandibular anteriors, premolars, and molars. The teeth had a wide variety of crown conditions: virgin crowns, small restorations, large restorations, metal and porcelain crowns, and caries. A total of 400 teeth had their crowns cut off horizontally at the level of the CEJ so that the outline of the pulp chamber relative to the external surface of the tooth could be observed. Fifty teeth were sectioned in a buccolingual direction through the crown and the roots. Fifty teeth were sectioned in a mesiodistal direction through the crown and the roots. Each cut section was irrigated with water, dried, and examined. Two observers examined each specimen independently and recorded all observed anatomical relationships. These relationships included orifice location, size, color, and shape. These observations were then correlated and any consistent patterns were listed. Lines were drawn on horizontal sections to observe the relationships more easily. RESULTS Two categories of anatomic patterns were observed: relationships of the pulp chamber to the clinical crown and relationships of orifices on the pulp-chamber floor. Relationships of the Pulp Chamber to the Clinical Crown The following observations were noted: 1. The pulp chamber was always in the center of the tooth at the level of the CEJ (Figs. 1–3). 2. The walls of the pulp chamber were always concentric to the external surface of the crown at the level of the CEJ (Fig. 2). 3. The distance from the external surface of the clinical crown to the wall of the pulp chamber was the same throughout the circumference of the tooth at the level of the CEJ (Fig. 3). These observations were consistent enough that several anatomic laws could be formulated: Law of centrality: the floor of the pulp chamber is always located in the center of the tooth at the level of the CEJ (Figs. 1–3). Law of concentricity: the walls of the pulp chamber are always JOURNAL OF ENDODONTICS Printed in U.S.A. Copyright © 2003 by The AmericanAssociationof Endodontists VOL. 30, NO. 1, JANUARY 2004 5

concentric to the external surface of the tooth at the level of the CEJ (Figs. 1–3). Law of the CEJ: the CEJ is the most consistent, repeatable landmark for locating the position of the pulp chamber. Relationships on the Pulp-chamber Floor The following observations were noted relative to all teeth: 1. The floor of pulp chamber is always a darker color than the surrounding dentinal walls (Fig. 4A). 2. This color difference creates a distinct junction where the walls and the floor of the pulp chamber meet (Figs. 4B and 5). 3. The orifices of the root canals are always located at the junction of the walls and floor (Figs. 5 and 6). 4. The orifices of the root canals are located at the angles in the floor wall junction [Fig. 6 (A and B)]. 5. The orifices lay at the terminus of developmental root fusion lines, if present [Fig. 7 (A–C)]. 6. The developmental root fusion lines are darker than the floor color (Fig. 7A). 7. Reparative dentin or calcifications are lighter than the pulpchamber floor and often obscure it and the orifices (Fig. 8). The following observations were noted relative to all teeth except maxillary molars: 1. If a line is drawn in a mesial-distal direction across the center of the floor of the pulp chamber, the orifices of the canals on either side of the line are equidistant [Fig. 9 (A and B)]. 2. If a line is drawn in a mesial-distal direction across the center of the floor of the pulp chamber, the orifices of the canals on either side are perpendicular to it [Fig. 9 (C and D)]. FIG 1. Cut specimen of a mandibular molar showing the centrality of the pulp chamber. FIG 2. Cut specimen of a mandibular molar showing the concentricity of the pulp-chamber walls to the external tooth surface at the CEJ. FIG 3. Cut specimen of a mandibular molar showing the equality of the distance of the pulp chamber walls from the external root surface (arrows). 6 Krasner and Rankow Journal of Endodontics

These observations were consistent enough that several anatomic laws regarding the pulp chamber floor can now be proposed: Law of symmetry 1: except for maxillary molars, the orifices of the canals are equidistant from a line drawn in a mesial distal direction through the pulp-chamber floor [Fig. 9 (A and B)]. Law of symmetry 2: except for the maxillary molars, the orifices of the canals lie on a line perpendicular to a line drawn in a mesial-distal direction across the center of the floor of the pulp chamber [Fig. 9 (C and D)]. Law of Color Change: the color of the pulp-chamber floor is always darker than the walls (Fig. 4A). Law of orifice location 1: the orifices of the root canals are always located at the junction of the walls and the floor (Fig. 5). Law of orifice location 2: the orifices of the root canals are located at the angles in the floor-wall junction (Figs. 5 and 6A). Law of orifice location 3: the orifices of the root canals are located at the terminus of the root developmental fusion lines (Fig. 7A). A summation of all of the laws and rules are shown in [Fig. 10 (A and B)]. DISCUSSION Definite patterns and relationships of the pulp chamber and on the pulp-chamber floor were observed. From these observations, specific laws have been proposed to help the clinician more systematically locate pulp chambers and the number and position of root-canal orifices on the pulp-chamber floor. Most practitioners begin root-canal treatment with preconceived ideas about the anatomy and position of pulp chambers and roots canals. These ideas are based on stylized pictures of virgin teeth presented in textbooks. Access to the pulp chamber is usually FIG 4. (A) Cut specimenshowing the dark chamber floor (FI). (B) Cut specimen showing the junction of the light walls and the dark floor (FWJ). FIG 5. Cut specimen showing the orifices (OL) located at the junction of the floor and walls (FWJ). Vol. 30, No. 1, January 2004 Pulp–Chamber-floor Anatomy 7