Classification of Teeth
Definition
Classification of teeth refers to the position of the first molars, and how they bite together.
Description
In 1844 J.F. Cravens, a dentist from Indianapolis, discussed the first dental deformities. He studied the first molar biting relationship and how the molars should line up with each other on the upper and lower jaws. Cravens called the first molar the "patriarch of the mouth," meaning the first molar determined the bite relationship for the entire mouth. J.N. Farrar, a leading dentist, in 1880 discussed the teeth relationship as an irregularity in his book "A Treatise on the Irregularities of the Teeth and Their Corrections."
In 1905 at the 4th Annual Meeting of American Society of Orthodontics the subject was again broached, but this time by Edward H. Angle, a dentist who dis- agreed with the other leading dentists and their terms and names of bite relationships. Angle had devised a simple and logical classification system for the teeth irregularities and deformities, which he didn't believe were irregularities or deformities at all, but rather malocclusions. He felt the first molar was "king of the mouth" and the basis for the classification of malocclusion of the teeth. Angle had studied Cravens's work and knew he could prove the theories.
Angle's classification system refers to the position of first molars and how they bite together and is broken into three main categories: Class I, II, III.
- Class I: The normal biting relationship between the upper and lower teeth and jaw, also known as a balanced bite. The front teeth may be spaced apart or crowding of the anterior teeth may be seen, but the biting relationship of the first molars is balanced.
- Class II: The lower first molar is posterior or more towards the back of the mouth than the upper first molar. In this abnormal biting relationship the upper front teeth of the jaw protrude further than the lower jaw, commonly called "buck teeth." There is a convex appearance in the profile of the patient with a receding chin and lower lip. Class II problems can be due to insufficient growth of the lower jaw or an over growth of the upper jaw, or a combination of the two. Class II cases are commonly genetically inherited and can be aggravated by environmental factors such as thumb sucking.
- Class III: The lower first molar is anterior or more towards the front of the mouth than the upper first molar. In this abnormal relationship the lower teeth and jaw project further forward than the upper teeth and jaws. There is a concave appearance in the profile with a prominent chin. Class III problems are commonly due to an overgrowth in the lower jaw or undergrowth of the upper jaw or a combination of the two. Like Class II, Class III is genetically inherited. Orthodontia may help relieve the class III biting relationship, but often surgery is required to shorten the lower jaw.
