Malocclusion (literally “bad bite”) is most often caused by hereditary factors such as an abnormal relationship between the size of the teeth and the size of the jaws. Malocclusion may also result from missing teeth or habits such as thumb sucking or tongue thrusting.
Malocclusions are classified based on the relationship of the maxillary (upper jaw) and mandibular (lower jaw) first permanent molars.
There are three basic classes of malocclusion, Class I, Class II, and Class III:
Class I malocclusion involves crowding, spacing, or overlapping of the teeth. In this classification the upper jaw is in a normal relationship to the lower jaw; that is, neither jaw protrudes.
Class II malocclusion occurs when the bottom jaw is in a more posterior (backward) position than normal. The top teeth appear to protrude out over the lower teeth. One example of this type of malocclusion is often referred to as “buck” teeth.
Class III malocclusion occurs when the lower jaw is in a more anterior (forward) position than normal. The lower teeth protrude out beyond the upper teeth. This is often the most difficult type of malocclusion to correct.