The way your upper and lower teeth bite together are classified into three types of malocclusion.
The traditional system for classifying malocclusions is Angle’s Classification from 1907.
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.
The mesiobuccal cusp of the upper 1st molar interlocks with the mesiobuccal grove of the lower 1st molar.
- 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 (overjet), 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.
The mesiobuccal cusp of the upper first molar has moved forward of its correct position creating an overjet.
- 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.
The lower molar has moved forward of its normal position often creating an anterior crossbite.