Diseases of the Teeth and Jaws - DentalCare

Diseases of the Teeth and Jaws

Allan G. Farman, B.S.D., EdS, MBA, PhD;
Sandra A. Kolsom, CDA, RDA;

Members of the ADAA Council on Education

Continuing Education Units: 4 hours

This continuing education course is intended for general dentists, hygienists, and dental assistants. This
course will help the dental auxiliary to understand the importance of high-quality radiographs and will, in
the long run, make him or her that much more valuable to the dental team.

Conflict of Interest Disclosure Statement
The author reports no conflicts of interest associated with this work.

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Overview

By law and by practice, the dentist is responsible for diagnosing conditions of the teeth and jaws.
Nevertheless, a dental auxiliary should have some knowledge of the basic dental disease appears
on radiographs. This knowledge will help the auxiliary to understand the importance of high-quality
radiographs and will, in the long run, make him or her that much more valuable to the dental team.

Learning Objectives

Upon the completion of this course, the dental professional will be able to:
• Recognize the radiographic appearance of dental caries, periodontal disease, periapical pathology, and

healing of extraction wounds.
• Have a basic knowledge of the radiographic appearance of tooth and bone fractures, developmental

anomalies and regressive changes of the teeth, and developmental abnormalities of the skull and jaws.

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Course Contents • Developmental Anomalies of the Jaws
Mandibular Tori
• Glossary Maxillary Torus
• Defective Restorations and Dental Caries Stafne Bone Cavity and Clefts

Defective Restorations • Summary
Enamel Caries • Course Test
Dentin Caries • References
Recurrent Caries • About the Authors
Cervical Burnout and Mach Banding
• Periodontal Disease Glossary
Dental Calculus
Proliferative Gingival Hyperplasia Abrasion – pathological wearing away of the
Horizontal Bone Loss and Vertical Bone Loss surface layers of hard or soft tissues.
• Periapical Pathology
Acute Apical Periodontitis, Acute Periapical Anomaly – abnormality.
Abscess and Chronic Periapical Abscess
Periapical Granuloma Apical foramen – an opening at a tooth’s root tip
Apical Radicular Cyst that allows the entry of nerve and blood vessels to
Osteosclerosis and Condensing Osteitis the pulp.
Osteoradionecrosis and Osteonecrosis
• Healing of Extraction Wounds Attrition – wearing away by friction or rubbing.
Normal Healing and Fibrous Healing
Socket Sclerosis and Residual Root Autosoma – pertaining to a chromosome other
Fragments than a sex chromosome.
• Fractures
Fractured Teeth Bilateral – two sided.
Fractured Bones
• Developmental Abnormalities Cementoenamel junction – the meeting of the
Supernumerary Teeth enamel of the crown and the cementum of the root
Hypodontia (Too Few Teeth) at the cervix of a tooth.
Macrodontia
Microdontia Chronic – persisting over a long period of time.
Hutchinson’s Teeth
Evagination Ectopic – out of place; e.g., an ectopic tooth
Invagination (Dens in Dente) eruption is one that occurs outside the normal
Taurodontism and Pyramidal Teeth path.
Dilaceration
Supernumerary Roots Embrasure – the V-shaped space between
Fusion and Gemination curved adjacent surfaces of teeth.
Concrescence
Regional Odontodysplasia Epithelial – type of tissue that forms the covering
Dentinogenesis Imperfecta and Dentin of all body surfaces.
Dysplasia
Amelogenesis Imperfecta Erosion – the destruction of tooth substance by
Turner’s Tooth and Environmental Hypoplasia chemical or mechanical-chemical action.
Talon Cusp and Enamel Pearl
• Regressive Changes in Teeth Exfoliate – to shed teeth, particularly referring to
Attrition and Abrasion primary teeth.
Erosion
Pulp Stones Exudate – a liquid substance that oozes from
Hypercementosis blood and lymph vessels, typically as a result of
Ankylosis inflammation.
External Resorption
Internal Root Resorption Fibrous – composed of or containing fibers.

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Furcation – the point at which the roots of multi- Radiodensity – the degree of radiolucency or
rooted teeth separate. radiopacity of a substance or tissue.

Gonadal – pertaining to the ovaries or testes. Radiolucent – a term that describes the ability
of a substance or tissue to allow passage of
Granuloma – a tumor that filled with granulation radiation with relatively little attenuation (reduction
tissue. of energy) resulting in a darker image on a finished
radiograph.
Hemihypertrophy – an excessive growth of one
half of the body, an organ, or a part (e.g., facial Radiopaque – a term that describes the ability
hemihypertrophy). of a substance or tissue to attenuate (reduce or
slow) the energy of radiation that passes through it
Incipient – the beginning stage; e.g., incipient resulting in a lighter image on a radiograph.
caries is the beginning stage of tooth decay when
the decay has not yet completely penetrated the Sclerosis – hardening of a body tissue.
enamel.
Scurvy – a condition that results from an
Intraosseous – within bone. ascorbic acid (vitamin C) deficiency; common
symptoms include weakness, poor wound healing,
Lamina dura – the compact bone that lines the and hemorrhage under the skin and mucous
tooth sockets. membranes.

Lobulated – divided into lobes, subdivisions. Suppurative – forming pus.

Necrosis – the death of cells or tissues. Taurodontism – an anatomical abnormality
in which a tooth’s pulp chamber is elongated,
Opalescent – a translucent appearance. enlarged, and extends into the region of the roots.

Orifice – the entrance or outlet of any body Defective Restorations and Dental Caries
cavity.
Defective Restorations
Osseous – bony or of bone-like structure or The junction of a restored tooth and the restorative
consistency. material should always appear sharp and distinct,
though there will be some qualitative differences
Ossification – the formation of bone or a change for interposed radiolucent bases. Restorations that
into bone. radiographically fail to extend to tooth preparation
margins (open margins), those that extend
Pathosis – a disease condition. beyond the preparation margins (overhangs),

Periodontium – a collective term that denotes Figure 1.
the tissues surrounding and supporting the teeth;
includes 1) the gingiva, 2) the cementum of the
tooth root, 3) the periodontal ligament, and 4) the
alveolar bone.

Polyp – a general term that describes any mass
of tissue that bulges or projects outward or
upward from the normal surface level.

Prognathic – pertaining to a forward relationship
of the jaws to the head (anterior to the skull)
resulting in a protruding lower face.

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and those with inappropriate contours may Figure 2.
be considered defective restorations. Such
restorations are usually defective at the time they Figure 3.
are inserted, though they may become defective
as a result of fracture, attrition, abrasion or demineralized and thus will appear smaller in the
erosion. radiograph because the rest of the advancing edge
is not radiographically visible. Clinically the lesion
Figure 1 is a molar bitewing radiograph that will usually be larger than its radiographic image.
discloses a defective restoration on tooth #3. The Figure 2 illustrates fairly advanced enamel caries
restoration ends short of the margin mesially and with penetration into the dentin.
distally, and illustrates both open margins and Dentin Caries
overhangs. Dentin Caries extends into the tooth dentin
and can be recognized by noting the focal loss
Enamel Caries of dentinal radiopacity. Most commonly, this
While advanced dental caries may well involve darkened dentin is located beneath carious enamel
the entire tooth, early or incipient caries involves and, typically, the lateral dimension of the dentinal
only the enamel. Once a carious lesion involvement exceeds that of the associated enamel
penetrates through the enamel, it is usually caries (Figure 3). Dentin caries may be discerned
considered to be dentinal caries. Clinically, interproximally, on the occlusal surface, buccally/
enamel caries usually appears as a stained lingually, or on root surfaces.
system of occlusal grooves or as chalky
white bands along the labial/buccal gingival
aspects of the teeth. Radiographically, enamel
caries is characterized by a focal loss of the
normal enamel radiopacity, particularly on the
interproximal surfaces.

It appears as a radiolucent cone shape, with the
base at the exterior surface and the tip of the
cone toward the pulp. The lesion follows the
enamel rods. After progression into the dentin
the lesion usually takes on a radiolucent fan
shape.

To locate interproximal caries, and interproximal
or bitewing survey is usually most valuable
because the maxillary and mandibular teeth
are simultaneously imaged on one film and
the projection geometry is most favorable for
accurate imaging. Anterior bitewing examination
requires a change of geometry, which is not
as favorable for interproximal caries detection.
These interproximal surfaces are thin and can be
easily examined clinically. Periapical examination
of the anterior region is useful for the detection of
cemental caries.

To be detectable on a radiograph there must be a
30% to 50% change in the mineral content of the
enamel lesion. Less than 30% demineralization
will not produce a detectable image. The
advancing edge of the lesion may not be 30%

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Figure 4. sharp and distinct, and, as a rule, recurrent caries
should be suspected whenever radiolucencies are
Figure 5. present between the tooth and the restoration.

Incipient occlusal dentin caries may be difficult to In Figure 4, recurrent caries appears at the
identify on radiographs and root caries must be mesial of tooth #3 and #4, and the distal of tooth
carefully distinguished from cervical burnout, as #28. Also, note areas of interproximal caries on
we will discuss later. tooth #5.

Recurrent Caries Cervical Burnout and Mach Banding
Recurrent caries is the condition in which Cervical burnout is an area of apparently
carious lesions develop or extend along the increased radiolucency in the mesial and distal
margins of existing restorations. A diligent search cervical (neck) regions of the tooth. Such regions
for recurrent caries should be made whenever are often mistaken for interproximal caries when
radiographs detect (1) interproximal restoration in fact they only appear radiolucent because they
overhangs; (2) open margins on restorations; have neither the radiopaque enamel of the region
(3) restorations which appear to end short of immediately above nor the bone tissue below.
preparation margins; (4) restorations which
appear unusually shallow as judged by the Figure 5 illustrates cervical burnout in a
thickness of the restorative material. premolar bitewing radiograph. Note that the
cementoenamel junction and the crest of the
Radiographically, recurrent caries presents alveolar bone lie respectively just above and
as radiolucent lines that extend inward from just below the burnout area. As a point of
the tooth surface along a restoration or as comparison, note the interproximal enamel caries
radiolucent zones, which appear to lie completely on the first and second premolars.
beneath the restoration, without any observable
communication with the tooth surface. As While carious lesions and areas of cervical
mentioned previously, the junction of a restored burnout do resemble each other, there are a
tooth and the restorative material should appear couple of tips to help differentiate between them.
First, cervical burnout is found only in the cervical
region or tooth neck, which is fortunately an
uncommon area for caries to develop. Second,
the cementoenamel junctions sharply limit areas
of burnout incisally and occlusally, as the alveolar
crest limits the area apically. Caries would not be
so sharply defined.

Occlusal caries may be undetectable on a
radiograph until the decay reaches the dentin.
Early radiographic appearance may be a thin
radiolucent shadow below the enamel. An optical
illusion referred to as Mach banding can produce
the same image in healthy teeth. Detection of
incipient occlusal caries is most effective by direct
clinical examination.

Periodontal Disease

A tooth in the intact periodontium maintains firm
attachment to a collar of the gingiva through
connective tissue fibers. Beneath the gingiva,
bone is attached to the root surface through the
periodontal ligament, a complex system of fibrous

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connective tissue. Deposits of free bacteria and At times, calculus deposits become so heavy
bacteria-rich plaque produce inflammation in the that they completely surround the tooth. Not
gingival collar, which, in turn, disrupts the fibrous surprisingly, such severe cases are associated
gingival-tooth attachment. with advance periodontal bone loss.

The continued presence of plaque and calculus Figure 6.
produces inflammation in the periodontal
ligament, leading to bone loss and weakened Figure 7.
attachment strength between the ligament and
the tooth. In time, the inflammatory process can Figure 8.
cause considerable bone loss – to the point that
the tooth becomes unstable and eventually is lost.

Ongoing research is pointing towards
collaboration between certain systemic diseases
and periodontal health. As dental professionals it
is our responsibility to discuss these findings with
our patients.

Clinically, the extensive bone loss and gingival
recession of advanced periodontal disease may
be easily visualized. In less advanced cases,
the periodontal probe can be used to measure
the distance between the gingival crest and the
periodontal attachment. Bleeding at the point of
probing and measurement of significant distances
are strong indications of periodontal disease.
Figure 6 radiographically illustrates probe depth
in a case of moderate periodontal disease with
early alveolar bone loss. Figure 7 illustrates
severe periodontal disease with extensive loss of
alveolar bone around the tooth.

Dental Calculus
Dental Calculus is mineralized dental plaque.
Heavy calculus deposits are most commonly
found opposite the salivary duct orifices located
near the mandibular incisors and maxillary
molars. Calculus is usually classified as
supragingival, which occurs above the gingiva
on the exposed tooth surfaces and subgingival,
which is found beneath the gingiva. It is well
known that the bacteria on the calculus induces
inflammation in the periodontal tissue and
contributes to the development of gingivitis and
periodontal disease.

On a dental radiograph, calculus is commonly
seen interproximally, either filling the dental
embrasures or producing distinct radiopaque
spurs such as that seen on the distal of the
maxillary molar in Figure 8.

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Figure 9. Figure 10.

Proliferative Gingival Hyperplasia Figure 11.
Gingival enlargements arise from a variety of
local and systemic factors, and may be localized defects whose height varies markedly compared
(Figure 9) or may involve the entire gingival to the adjacent tooth crowns. This defect
area. Localized gingival enlargements most is known as vertical bone loss and can be
commonly result when a discrete area of the recognized on a radiograph by noting that a line
gingiva is irritated by plaque, calculus or extrinsic representing the residual bone crest sharply
factors such as popcorn hulls or hard candy. intersects another line between the tooth necks.
Less frequently, local conditions represent an Vertical loss is sharply apparent distal to the
extension of underlying bone disease. maxillary first molar and between the premolars
(Figure 11).
Generalized gingival enlargement may result from Vertical bone loss may extend to the root apex,
longstanding, chronic inflammation such as that and prominent calculus deposits are often noted.
noted in chronic gingivitis or periodontitis. It has Care must be taken to assess the degree of
also been associated with the hormonal changes bone loss, especially around molars where
that occur with puberty and pregnancy, with special attention should be directed to the
certain drug therapy (i.e., Cyclosporins, Dilantin, furcational periodontal ligament space.
Nifedipine), with systemic disorders such as Vertical bone loss extending into this area may
scurvy and leukemia, and with genetic disorders appear as a focally widened ligament space.
such as fibromatosis gingiva.

In nearly all cases, generalized gingival
enlargements produce only minimal osseous
change; and, thus, if they are definable on
radiographs at all, it is only on the basis of their
increased gingival soft tissue outline.

Horizontal Bone Loss
Generalized, extensive periodontal bone loss, in
which the crest of the residual bone is parallel
to the cementoenamel junction, is referred to as
horizontal bone loss (Figure 10).

Vertical Bone Loss
With periodontal disease, bone loss may be
relatively severe around some teeth, while
leaving the immediately adjacent teeth firmly
anchored. Such focal loss creates osseous

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Periapical Pathology Figure 12.

Acute Apical Periodontitis Figure 13.
Following the necrosis of the dental pulp through
any cause, irritants drain and can cause a periodontium. These remnants can proliferate
reaction in the periodontal tissues adjacent to within an apical granuloma to form an apical
the apical foramen. There is usually little, if any, radicular cyst, which can grow to several
immediate bone resorption, so apical periodontitis centimeters if left untreated. Apical radiolucencies
is often difficult to detect with radiographs except greater than about six millimeters usually contain
that the tooth may appear slightly elevated in the epithelial cyst material. Figure 14 illustrates
tooth socket due to the collection of inflammatory a clearly defined apical periodontal cyst in a
exudate. pulpless tooth following acute trauma.
A cyst can continue to grow even after the
Acute Periapical Abscess irritation has ceased or the source has been
Acute, by definition, means short term. Acute removed. Such continuing growths are termed
abscesses often show little radiographic change residual cysts.
because over the short run, the body has not had If the process starts from a lateral, rather than an
sufficient time to resorb bone. apical canal, a lateral radicular cyst can occur.

Chronic Periapical Abscess
The chronic periapical abscess represents a
suppurative process that has been present long
enough to cause the body to resorb bone. It is
not possible to absolutely differentiate between
a chronic abscess, dental granuloma, or small
radicular cyst solely by using a dental radiograph.
However, a radiographic image of multiple
foraminae (many openings or passages) within
the pathological area is strongly suggestive of
sinus tract formation and drainage of pus. Notice
the four prominently radiolucent foraminae in the
resorbed periapical area (Figure 12).

Periapical Granuloma
The periapical granuloma represents the body’s
defense mechanism attempepresents the body’s
defense mechanism attempting to wall off irritants
draining from a non-vital dental pulp. While
they cannot be radiologically differentiated from
abscesses or cysts, they can be differentiated
from normal anatomical landmarks such as the
incisive fossa because the periodontal ligament
space is widened and the lamina dura is not
continuously intact.

Figure 13 illustrates apical periodontal pathosis in
the area of the right central incisor. Note the loss
of continuity of the lamina dura and the widened
periodontal ligament space on the affected side.

Apical Radicular Cyst
Epithelial remnants from tooth formation are
always present as builder’s debris within the

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Figure 14. Notice how the cystic formation in Figure 15
Figure 15. follows the lateral aspect of the tooth root, thus
Figure 16. differentiating it from an apical cyst.

A cyst can continue to grow even after the
irritation has ceased or the source has been
removed. Such continuing growths are termed
residual cysts.

Osteosclerosis and Condensing Osteitis
Increased bone deposition may be secondary to
a variety of local irritants, most notable infection.
Such increased bone deposits are termed
osteosclerosis, or alternatively, condensing
osteitis. Figure 16 illustrates the radiographic
appearance of condensing osteitis surrounding
the apices of a deeply carious first molar.

Although osteosclerosis is commonly associated
with carious, frequently non-vital teeth, it may also
be found at the apices of entirely normal teeth,
most commonly the mandibular first permanent
molar. It should be pointed out that involved
teeth usually show fully formed roots without a
significant degree of root resorption. (Other terms
used to indicate condensing osteitis are rarefying
or sclerosing osteitis.)

Osteoradionecrosis and Osteonecrosis
Osteoradionecrosis (ORN) also known as
postradiation osteonecrosis (PRON), is a serious,
debilitating and deforming potential complication
of radiation therapy for the treatment of cancer.
It is known to occur following radiation treatment
when the maxilla or mandible is directly in the
field of radiation.

Bisphosphonate-associated osteonecrosis of the
jaw (ONJ) is uncommon but has been associated
with intravenous bisphosphonate cancer therapy.
Any needed dental procedures should be
completed before intravenous bisphosphonate
cancer treatment is started. More research is
needed for patients receiving oral bisphosphonate
for the treatment of osteoporosis. At this time, it
does not seem to be a serious risk and normal
dental services are recommended.

Diagnosis depends primarily on clinical and
radiographic changes in the bone. These signs
and symptoms typically include ulceration of the
mucosa, loosening of the teeth and exposure of
necrotic bone.

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Figure 17. Figure 19.

Figure 18. Figure 20.

Healing of Extraction Wounds Socket Sclerosis
If healing is accompanied by excessive bone
Normal Healing deposition, socket sclerosis results, leading to
Following normal tooth extraction, the extraction radiodense areas within the socket as illustrated
socket is clearly demarcated by the radiopaque (Figure 19).
bundle bone into which the periodontal ligaments
had anchored the tooth. A radiograph of a recent Residual Root Fragments
first mandibular molar extraction site is illustrated If the tooth is not completely removed, e.g., If the
(Figure 17). Note the clear outline of the root tooth is not completely removed, e.g., because of
socket. a root fracture or residual deciduous tooth root,
a residual tooth fragment may persist. These
With healing, new bone is deposited into the fragments can be distinguished from socket
socket, and, with time, the bundle bone slowly sclerosis by the presence of a root canal and
fades. After about 18 months, it can no longer be an intact periodontal ligament space. Figure 20
distinguished from the surrounding tissue. illustrates the appearance of a residual root and
intact ligament space following the extraction of a
Fibrous Healing mandibular first molar.
Occasionally dental extraction sites lay down a
fOccasionally dental extraction sites lay down a Fractures
fibrous tissue healing. Such tissues appear as
radiolucent areas such as that in Figure 18 and Fractured Teeth
sometimes last for periods well in excess of the Traumatic injuries, extensive caries and oral
normal healing time. neglect can lead to fracturing of the dental tissues.

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Figure 21. Figure 22. Figure 23.

Maxillary incisors are particularly prone to retained intraosseous wiring is visible at the healed
traumatic injuries. The fracture often leads to fracture site (Figure 25).
losing portions of the tooth crown such as the
traumatic loss of the incisal edges (Figure 21). Developmental Abnormalities

Fracture can also affect the tooth root, appearing Supernumerary Teeth
as a radiolucent line across or with the tooth’s The relatively common abnormality of teeth
long axis. Be careful not to mistake the artifact numbering in excess of the standard 32 permanent
of a fingernail crimp as a fracture! Figure 22 is a or 20 deciduous is known as supernumerary
radiograph of a fractured tooth. A fingernail crimp dentition. Areas of the jaws most frequently
would be very similar, though possibly somewhat affected with supernumeraries include the
more broad and radiolucent (Figure 23). maxillary central and lateral incisor and molar
regions, and the mandibular premolar region.
Fractured Bones
Even though bone is usually strong and resilient, The most common supernumerary tooth is the
Even though bone is usually strong and resilient, mesiodens, occurring between the maxillary
a forceful blow can cause it to break. Therefore, central incisors (Figures 26 & 27). This tooth is
patients with a history of traumatic injury and a usually small and cone-shaped and may be either
clinical picture of bruising and tenderness should erupted or impacted.
be radiographed to detect a fracture. Depending
on the nature of the injury, a fracture can be Supernumerary teeth of the maxillary molar region
a straight or jagged line, which may penetrate occur either distal to the third molar, thus called
partially or completely through the bone and leave fourth molars, or between or adjacent to the third
the bones normally aligned or displaced. Figure and second molars, becoming paramolars.
24 illustrates a non-displaced mandibular fracture
in the canine region. Multiple-impacted supernumerary teeth are
classically associated with Gardner’s Syndrome,
If the fracture site is unstable, or displaced, a hereditary condition marked by multiple polyps
intraosseous wiring is used to maintain position of the colon, and cleidocranial dysplasia, a rare
during healing. hereditary condition in which there is defective
ossification of the cranial bones and complete
During healing, the body often lays down excess or partial absence of the clavicles. Given the
bone or callus in the injured area. This callus and serious ramifications of these diseases, it is vitally

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Figure 26.

Figure 24.

Figure 27.

Figure 25. Figure 28.

important to consider them whenever multiple first permanent molar, and retention and ankylosis
supernumerary teeth are encountered. of the mandibular second deciduous molars.

Hypodontia (Too Few Teeth) More severe forms of congenital hypodontia are
Missing teeth is an exceedingly common finding, associated with hereditary anhidrotic ectodermal
which can usually be attributed to extraction or dysplasia, a disease characterized by the
traumatic evulsion. Such acquired hypodontia absence of eyebrows and eye lashes, a depressed
must be contrasted with congenital hypodontia, nasal bridge, prominent supraorbital ridges,
which arises because of a developmental error. light, scanty hair and wrinkled palms secondary
to hyperkeratosis. In such patients, it is not
Congenital hypodontia most commonly affects uncommon for only three or four teeth to develop.
the third molars, the permanent maxillary lateral
incisors and the maxillary and mandibular
premolars. Frequently, hypodontia is bilateral.
Figure 28 is an example of a patient with
congenital hypodontia, affecting the mandibular
second premolars bilaterally, the left mandibular

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Figure 29. Figure 31.

Figure 30. Figure 32.

Macrodontia Microdontia
Macrodontia is the formation of unusually large Microdontia is a condition characterized by
teeth. Most commonly, this developmental unusually small teeth. Again, it commonly affects
anomaly presents as a single enlarged tooth, and, only one tooth, most often the maxillary lateral
less frequently, as multiple macrodonts. Figure 29 incisor or peg lateral and the third molar. It may
is a right maxillary lateral incisor macrodont with also manifest as a feature of other anomalies such
a small hypoelastic enamel defect on the labial as supernumerary teeth. Figure 31 is a maxillary
tooth surface. third molar microdont.

The patient’s radiograph, shown in Figure 30 Generalized microdontia is very uncommon. It has
clearly outlines the macrodont and additionally been associated with pituitary dwarfism, hypoplastic
reveals an impacted maxillary canine. type amelogenesis imperfecta and anhidrotic
ectodermal dysplasia.
As noted earlier, macrodontia usually results
in a single large tooth. Much less frequently, Hutchinson’s Teeth
multiple macrodonts are encountered with such Hutchinson’s teeth result from a highly distinctive
conditions as facial hemihypertrophy and pituitary form of enamel hypoplasia, occurring only in
giantism. Tooth fusion, which will be discussed congenital syphilis. Affected incisors demonstrate
later, produces teeth that are virtually identical convergence of mesial-distal dimension approaching
to macrodonts; and, indeed, it may well be the incisal edge. Typically, there is a distinctive
impossible to distinguish between the two. notch on the mid-incisal edge, which has been
likened to the appearance of a screwdriver (Figure
32). All maxillary and mandibular incisors may show
the defect, although the maxillary lateral incisor may
appear normal while the others are defective.

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Figure 33. Figure 34.

Evagination Figure 35.
Evaginationrepresents a somewhat rare dental
developmental malformation in which there a pattern of large pulp chambers and short roots.
appears to be a small accessory cusp arising Clinically, the teeth appear normal, but on a
from the occlusal surface of a tooth. Figure 33 radiograph, they demonstrate a distinct rectangular
illustrates a maxillary premolar with evagination outline, such as seen in tooth #19 (Figure 36).
occupying the space between the buccal and Taurodontism may affect multiple teeth, but it
lingual cusps. is limited almost entirely to the molars. It is
associated with Kleinfelter’s Syndrome, a
Although it may occur on any tooth, it is most syndrome of gonadal defects, appearing in males,
commonly observed on the premolars. The with an extra X chromosome, which should be
malformation is composed of enamel and dentin suspected whenever taurodontism is encountered
and may extend into the pulp; and thus, attrition in patients with unexplained mental retardation, a
on caries involving the evagination may lead to tall, thin appearance, long legs and arms, and a
pulp necrosis and periapical disease. distinctly prognathic jaw.

Invagination (Dens in Dente)
Invagination represents a deep infolding of the
tooth with extension of the enamel down through
the dentin into the pulp. Such teeth can be
severely deformed, appearing with an enlarged
pulp chamber that has been likened to a tooth
within a tooth (dens in dente).

The most commonly affected tooth is the
permanent maxillary lateral incisor (Figures 34 &
35). Single dens in dente are most common, but
double varieties also occur.

Taurodontism and Pyramidal Teeth
Taurodontism is a fairly common developmental
defect in which the affected multi-rooted teeth
display apically displaced furcation, producing

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Figure 36.

Figure 38.

Figure 39.

Figure 37. The curvature is more visible if it occurs in a
plane perpendicular to the central X-ray beam. If
Pyramidal teeth are morphologically similar to it occurs parallel to the beam, it casts a shadow
taurodontism. They exhibit enlarged, elongated similar to a radiopaque cyst or bone deposit
pulp chambers but only single roots as illustrated because the axis is oriented toward or away from
in tooth #18 (Figure 36). In effect, the condition the beam.
appears to represent extreme apical displacement
of the furcation, resulting in a single broad root, Supernumerary Roots
which, in actuality, is the body of the tooth. Teeth having a greater number of roots than is
The clinician will sometimes encounter both anatomically typical have supernumerary roots.
taurodontism and pyramidal teeth in the same The canines, mandibular premolars and maxillary
patient. second premolars are usually single rooted, and a
radiographic appearance such as that in Figure 39
Dilaceration would be diagnostic of supernumerary roots.
Dilaceration is an unusual bend in the tooth
root(s). The curvature usually results from trauma Fusion and Gemination
and can occur anywhere along the root. Since FusionFusion is defined as the joining of two
the tooth crown is clinically normal, the degree of originally separate teeth through the dentin, or
dilacerations can only be detected radiographically. through the dentin and enamel. In contrast,
gemination represents incomplete division of what
Dilaceration may range from mild curvature should have been two separate teeth. Fusion
(Figure 37) to severe bending (Figure 38). may involve supernumerary teeth, and gemination

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

Figure 40.

Figure 42.

Figure 41. Figure 43.

may occur in quadrants also affected by partial Regional Odontodysplasia
anodontia; thus, counting the teeth in the affected Regional odontodysplasiarepresents a
area is of limited diagnostic value. Regardless of developmental disorder in which one or several
which process initiated the error, it is practically teeth in a contiguous group fail to properly form.
impossible to distinguish between fusion and The condition occurs sporadically without a
germination, and in either case, the tooth will distinct familial pattern and most commonly affects
appear much like that in Figure 40. the anterior maxillary quadrants. The involved
teeth often fail to erupt, or if they do erupt, they
The distinction between fusion and germination are misshapen with irregular crowns and defective
is primarily of academic interest and thus, the mineralization. Unerupted teeth are characterized
etiology is of less clinical concern than is the by soft tissue swelling and painful symptoms.
presence of the condition and the potential
ramifications involved. Radiographic features typically consist of one
tooth, or segment of teeth, demonstrating
Concrescence incomplete formation and reduced radiopacity.
Concrescence represents the joining of adjacent Because of their radiolucency, they are sometimes
teeth via the cementum with obliteration of the known as ghost teeth. In Figure 43, the posterior
intervening periodontal ligaments. Concrescence maxillary segment demonstrates an unerupted
is usually found in two teeth, rarely in three or and incompletely mineralized second premolar
more. The clinical appearance of the condition and second molar. The first molar is absent and
is shown in Figure 41 and the appearance on a swelling of the overlying soft tissue is noted.
radiograph in Figure 42.

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

Figure 46.

Figure 44.

Figure 45. Figure 47.

Dentinogenesis Imperfecta and Dentin The second type is coronal dentin dysplasia
Dysplasia and is characterized by the thistle-funnel pulp
Dentinogenesis Imperfecta is an inherited chamber enlargement in the permanent teeth
disorder, usually showing a dominant autosomal (Figure 46).
pattern. Clinically, the teeth have a peculiar
translucent appearance with discoloration ranging Amelogenesis Imperfecta
from brown to yellow to gray. Such teeth are Amelogenesis Imperfecta constitutes a diverse
termed opalescent. group of distinct, genetic disorders which share
generalized defective enamel formation. As
Radiographically, all teeth in the deciduous and distinct conditions, varieties of amelogenesis
permanent dentitions show early and frequently imperfecta have been linked to autosomal,
complete obliteration of the pulp chambers and X-linked, dominant, and recessive genes.
canals with short, blunted roots (Figure 44).
Clinically, the enamel may be partially missing
Dentin dysplasia is another autosomal dominant (hypoelastic); very soft (hypocalcified); or
condition in which there is markedly disturbed firm but chippable (hypomaturation). Varying
dentin formation. This extremely rare condition degrees of yellow to brown tooth discoloration
occurs in two distinct patterns. The first, may be present. On the radiograph, the
referred to as radicular dentin dysplasia, is teeth may show hypoplasia from failure of
characterized by partial or complete obliteration enamel formation or a chipped and worn-away
of the pulp chamber and extremely short, blunted appearance from partial formation (Figure 47).
roots (Figure 45). When persistent, the pulp
chamber displays a characteristic crescent.

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

Figure 48.

In cases of hypocalcification, the radiodensity Figure 49.
of the enamel and the dentin are very close and,
thus, delineating between them is difficult. Mild opacification and focal surface pitting may
not be visible on radiographs.
Turner’s Tooth and Environmental Hypoplasia
Enamel hypoplasia, limited to a single tooth, Talon Cusp and Enamel Pearl
is known as Turner’s Hypoplasia and the The talon cusp represents a developmental
affected tooth is termed Turner’s tooth. The anomaly in which a peculiar lingual cusp forms
most frequently affected teeth are the permanent on the maxillary or mandibular incisors. When
maxillary incisors and the maxillary and small, the cusp cannot be distinguished from an
mandibular premolars. Common causes for accentuated cingulum. When well-developed,
the condition include local trauma or infection the cusp appears clinically (Figure 50) and, on a
derived from an overlying deciduous tooth. radiograph (Figure 51).
Clinical appearance can range from mild, opaque
chalkiness or brown discoloration or frank enamel The enamel pearl is a misplaced (ectopic)
pitting (Figure 48). globule of enamel, occurring most commonly in
the furcation areas or near the cementoenamel
In contrast to the genetic nature of Turner’s root surfaces of the molar teeth. Affecting the
Hypoplasia, environmentally-induced maxillary more often than the mandibular areas,
developmental failure of enamel formation the relatively rare enamel pearls may contain a
affecting multiple teeth is termed generalized dentin core, occasionally with pulpal extension.
environmental enamel hypoplasia.
Environmental factors can include nutritional Radiographically, the pearl appears as a round
deficiencies, excessive fluoride ingestion, and or semi-spherical area of increased radiodensity.
severe, fever-producing childhood diseases. When occurring on the mesial or distal aspects,
the pearl produces an obvious convex profile.
Clinically, the affected teeth show localized On the buccal or palatal/lingual aspects, it is less
enamel deficiency ranging from focal opacification easily seen and may resemble pulp stones.
to severe pitting. The distribution of enamel
defects reflects the chronology of enamel Regressive Changes in Teeth
formation with most severely affected areas
representing the area that were forming at the Attrition
time of the environmental influence. Attrition represents the physiologic wearing
away of tooth structure through such causes
The radiographic features of generalized as normal mastication. The incisal, occlusal
environmental enamel hypoplasia consist of linear
bands of relatively radiolucent enamel (Figure 49).

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

Figure 50.

Figure 52.

Figure 51. Figure 53.

and interproximal surfaces are typically affected, acidic and the process does not involve bacterial
and often the enamel is worn away so that the action. Clinically, erosion is usually described in
exposed dentin is clearly visible. Although attrition connection with the gingival one-third of the labial
rarely results in serious disease, advance cases aspect of the anterior teeth, although any tooth
can lead to pulp necrosis and periapical disease. surface can be affected. Erosion may arise due
to environmental factors such as personal diet
Abrasion and occupations that involve working with acids.
The pathologic wearing away of tooth structure
secondary to friction is abrasion. Agents, which Chronic vomiting may produce extensive erosion
contribute, include abrasive toothpaste, improper of the lingual tooth surfaces due to the acid
use of toothbrush, flosses and toothpicks, and nature of stomach contents (Figure 53).
personal habits such as excessive brushing, and
holding pins, nails and tacks between the teeth. Pulp Stones
A common form of abrasion involves the cervical Pulpal calcification is an extremely common
areas, producing a sharply defined V-shaped finding and is considered by many to be a
defect such as that crossing the buccal aspect of
the premolar (Figure 52).

Erosion
Erosion represents loss of tooth structure caused
by chemical action. Usually these chemicals are

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

Figure 54. Hypercementosis
Excessive deposition of cementum along the
Figure 55. root surface is termed hypercementosis.
The precise cause of this condition is not well
Figure 56. understood, although the loss of tooth antagonism
and local inflammation is often associated with
variation of normal pulpal development. it. A special exception is osteitis deformans or
Calcifications presenting as distinct intra-chamber Padget’s disease, in which teeth in an affected
(or less often intra-canal) radiopacities are known jaw typically demonstrate a remarkable degree of
as pulp stones. Figure 54 illustrates a prominent hypercementosis.
stone in the pulp chamber of the second maxillary
molar. It must be noted that it is often difficult Radiographically, the condition is characterized
to differentiate the radiographic appearance of by a bulbous, opaque expansion of root contours,
a pulp stone from the simple superimposition of usually involving much of the root length, while
furcation contours. preserving the periodontal ligament space and
lamina dura (Figure 55). Less commonly, the
overgrowth is limited to the root apex.

Ankylosis
Tooth ankylosis represents a direct union of tooth
to bone, eliminating the normally interposed
periodontal ligament. Ankylosis is uncommon,
usually encountered with deciduous teeth and
often, though not exclusively, associated with local
trauma and/or infection.

Clinically, deciduous ankylosis typically presents
a retained tooth positioned below the level of the
occlusal plane and is termed a submerged tooth.
Radiographically, the ankylosed tooth typically
exhibits signs of partial root resorption, obliteration
of portions of the periodontal ligament, mild
osseous sclerosis and apparent direct attachment
of root and bone (Figure 56). On occasion,
impacted teeth will become ankylosed in the jaw.

External Resorption
Mild external resorption of permanent teeth is a
relatively common finding. Its specific causes can
often be attributed to trauma, orthodontic therapy,
reimplantation, cysts, tumors and infection. In
other cases, no specific cause can be identified.

Root resorption most commonly is limited to the
apical portion of the root and lacks any clinical
manifestations. However, the condition can
advance to the point that teeth become mobile
and exfoliate.

Radiographic appearances include blunting of
root apices with shortening of root length. In

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

Figure 57. Figure 58.

some cases, abrupt loss may be noted, and, with chamber or canal (Figure 58). If the canal is
advancing disease, the entire root may appear involved, it is virtually impossible to distinguish
lost. Figure 57 illustrates a marked blunting and between internal and external resorption.
root loss following orthodontic therapy.
Developmental Anomalies of the Jaws
It is critically important to examine the tissues
immediately surrounding the resorbing root. Mandibular Tori
While, in most cases, the resorption is mild and Mandibular tori epresent benign overgrowths
relatively inconsequential, it can be severe and of mature, lamellar bone, occurring on the
may be secondary to a number of significant lingual mandibular cortex. Typically attached to
tumors, including odontogenic neoplasms and the mandible opposite the premolar region and
metastatic cancer. Care must be taken to avoid superior to the mylohyoid line, they are most
simply identifying the condition without making commonly bilateral. There is some variation in
a thorough investigation for signs of a far more incidence among races with a higher incidence
serious disease. among Orientals than in Caucasians. Apparently,
genetic factors also influence tori development, as
Internal Root Resorption the offspring of parents with mandibular tori have
Internal resorption represents a peculiar internal a much higher incidence of development.
dissolution of dentin, which can extend eventually
into the enamel and/or cementum by the tooth Radiographically, tori appear as well-defined
root. Usually, only a single tooth is involved, and areas of radiopacity overlying the tooth roots
although the cause is not clearly understood, it is (Figure 59), particularly extending from the
often linked to inflammation. canine to the molar regions. If tori are seen on
radiographs, they should be clinically confirmed
Clinically, internal resorption in the pulp in order to rule out other conditions, which lead to
chamber may lead to the Tooth of Mummery osseous radiopacity.
with a developing pink hue in the tooth crown.
Resorption in the root canal is not clinically Maxillary Torus
visible; however, perforation of the root usually The maxillary torus presents as a hard,
requires that the tooth be extracted. frequently lobulated, benign overgrowth of
mature lamellar bone. It is frequently located in
Radiographic evidence of internal resorption the midline of the hard palate (Figure 60) and
consists of an unusual widening of the pulp attached by a broad, bony base.

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

Figure 59. Figure 61.

Figure 60. Figure 62.

The condition is more common in Native well-defined radiolucency found at the angle of the
Americans, American Indians and Eskimos than mandible below the mandibular canal that has no
in Caucasians or Blacks and has a population- significance except in its differentiation from other
wide frequency of occurrence of about 25 conditions (Figure 62).
percent. Hereditary factors have been implicated.
Radiographically, the maxillary torus appears as Clefts
a well-defined radiopacity situated at, or superior Developmental clefts of the palate are not
to, the apices of the maxillary teeth (Figure 61). uncommon. They result from a smooth defect
On panoramic radiographs, it may be visualized and are often associated with marked tooth
in the midline and over the roots of the canines, displacement.
premolars and molars.
Summary
Stafne Bone Cavity
The Stafne cavity is an osseous defect caused Many conditions of the hard and soft tissues of the
by pressure of the submandibular salivary gland oral cavity and surrounding area can be diagnosed
on the mandible during its development. It is a and treated through the use of quality dental
radiographs. The importance of quality dental
radiographs cannot be overstated and is covered
in other continuing education courses offered by
the American Dental Assistants Association.

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

Course Test Preview

To receive Continuing Education credit for this course, you must complete the online test. Please go to
www.dentalcare.com and find this course in the Continuing Education section.
1. The carious lesion on the canine tooth in the below image involves which dental structures?

a. Enamel only
b. Dentin only
c. Pulp
d. Enamel and dentin

2. What type of bone loss affects the molar tooth in the below image?
a. Horizontal bone loss
b. Vertical bone loss
c. Osteosclerotic
d. Attrition

3. The radiolucency at the upper left associated with the apex of tooth #8 in the below image
could be:
a. An abscess
b. A cyst
c. A granuloma
d. All of the above

4. The radiopacity to the right of the molar in the below image is:
a. A root fragment
b. Condensing osteitis
c. Calculus
d. A maxillary torus

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

5. The radiolucency across the lateral incisor in the below image is:
a. A fracture of the tooth root
b. A transverse carious lesion
c. A fingernail crimp artifact
d. Horizontal bone loss

6. The radiopacity above the maxillary premolar in the below image is:
a. Calculus
b. An enamel pearl
c. An impacted supernumerary tooth
d. Osteosclerosis

7. The tooth in the below image probably resulted from:
a. Fusion or gemination
b. Evagination
c. Invagination
d. Fracture

8. What regressive change is illustrated in the below image?
a. Internal resorption
b. External resorption
c. Ankylosis
d. Hypercementosis

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

9. The radiolucency in the patient’s left mandible in the below panoramic radiograph is most
likely a:
a. Circular fracture
b. Talon cusp
c. Mandibular tori
d. Stafne bone cavity

10. The apical radiopacity at the base of the premolar in the below image is:
a. Condensing osteitis
b. External resorption
c. A root fragment
d. Cervical burnout

11. A diligent search for recurrent caries should be made when radiographs detect __________.
a. open margins on restorations
b. interproximal restoration overhangs
c. restorations which appear to end short of the preparation margins
d. All of the above.

12. A normal anomaly of the X-ray process which sometimes causes an image that looks
suspiciously like interproximal caries is:
a. Proliferative gingival hyperplasia
b. Dental calculus
c. vertical bone loss
d. Cervical burnout

13. Disorders that may clinically show a peculiar translucent appearance with discoloration
ranging from brown to yellow to gray is/are ____________.
a. dentinogenesis imperfecta
b. amelogenesis imperfecta
c. Turner’s hypoplasia
d. All of the above.

14. ____________ is an anatomical abnormality in which a tooth’s pulp chamber is elongated,
enlarged, and extends into the region of the roots.
a. Taurodontism
b. Hemihypertrophy
c. Lobulated
d. Ossification

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

15. Dilaceration is a ____________.
a. unusual bend in the tooth crown
b. unusual bend in the tooth root(s)
c. v-shaped space between curved adjacent surfaces of teeth
d. disease condition

16. Epithelial remnants (builder’s debris) can proliferate within an apical granuloma to form
____________.
a. an apical or lateral radicular cyst
b. a macrodont
c. a pulp stone

17. Which of the following is associated with the Tooth of Mummery?
a. Pulp stones
b. Impacted supernumerary molars
c. Internal root resorption
d. Periapical granuloma
e. Pyramidal teeth

18. Teeth numbering in excess of the standard 32 permanent or 20 deciduous teeth are known as:
a. Macrodonts
b. Microdonts
c. Hypodonts
d. Supernumeraries

19. Mineralized plaque seen opposite the salivary ducts is ____________.
a. proliferative gingival hyperplasia
b. dental calculus
c. an enamel pearl
d. a talon cusp
e. early concrescence

20. A congenital disease characterized by the presence of only three or four teeth, the absence of
eyebrows and eye lashes, and wrinkled palms is ____________.
a. ectodermal dysplasia
b. Hutchinson’s syndrome
c. Kleinfelter’s syndrome
d. facial hemihypertrophy
e. Turner’s syndrome

21. The approximate population-wide incidence of the maxillary torus is _____.
a. 66%

b. 33%
c. 15-18%
d. 10%
e. 25%

22. Gingival enlargements can occur as a result of ____________.
a. plaque
b. calculus
c. extrinsic factors
d. All of the above.

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

23. Bone loss which demonstrates remarkable variation in height relative to the adjacent tooth
crowns is:
a. Internal resorption
b. Vertical bone loss
c. Socket sclerosis
d. Bundle bone

24. The laying down of excess bone in an extraction socket is known as:
a. Incomplete healing
b. Socket fibrosis
c. Socket sclerosis
d. Bundle bone

25. A tooth with the notched appearance of a screwdriver is known as:
a. Hutchinson’s tooth
b. Turner’s tooth
c. Tooth of Mummery
d. Kleinfelter’s tooth
e. Talon’s tooth

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References

No references cited.

About the Authors

Original Manuscript:
Allan G. Farman, B.S.D., EdS, MBA, PhD

Dr. Farman is a Diplomate of the Board of Oral and Maxillofacial Radiology, and
Professor of Oral and Maxillofacial Radiology in the Department of Primary Patient
Care at the University of Louisville School of Dentistry.

Revised 2004 and 2009:
Members of the Council on Education of the ADAA
Members of the Council on Education of the American Dental Assistants Association helped with the
revision of this course. All members of the Council on Education are ADAA Active or Life Members with
an interest in dental assisting education. Each one volunteers their time to the lifelong learning of dental
assistants.

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010