Best Invisalign Islington London dentist is highly specialized dentists. Their main focus is on the prevention and treatment of "improper bites". This is an important dental issue, as improper bites can lead to a variety of problems such as tooth irregularities, lop-sided jaws and crooked teeth. Orthodontics was actually the first sub class of dentistry to be recognized as its own specialty field. Generally speaking, it takes two to three years of extra schooling after graduating as a dentist to earn the qualifications to become an orthodontist.