Overjet is a measure of how far the top incisor teeth are ahead of the bottom incisors. Normally, the top and bottom front teeth should be touching upon closure leaving no or zero overjet. If the top teeth are ahead by some distance this is referred to as positive overjet. If the top teeth are behind the bottom teeth are referred to as negative overjet, underbite or underjet.

Overjet (some people refer to it mistakenly as overbite) may be caused by one or more reasons. Crowding of teeth may “push out” the top incisor teeth or push in the bottom incisors. Some habits like “thumb sucking” during the growing years of a child may result in an increased overjet. A common cause of increased overjet is a skeletal disharmony in which the top jaw is relatively “ahead” of the bottom jaw. This relative discrepancy may result because of an overdeveloped upper jaw and/or small (underdeveloped) lower jaw.

Increased overjet results in a poor appearance that may affect the psychosocial health of the child especially if they are teased by their peers. Additionally, an increased overjet increased the risk of injury to the top incisor teeth if the child gets any kind of injury to the face. A study has shown that the risk of damage to the top incisors increased significantly if the overjet is severe. Such injuries may result in fractures or even complete loss of one or more of the upper incisors.

Overjet can be easily diagnosed by the dentist or the orthodontist when the permanent incisor teeth erupt at about 7-8 years of age. Treatment timing should be decided by an orthodontist and is usually done when all permanent teeth erupt although some orthodontists chose to treat these cases at an earlier limited “phase I” treatment to reduce the chances of tooth damage. This early treatment, however, does not necessarily negate the need for a second “phase II” treatment a few years later.

Treatment of increased overjet depends on the age of the patient, the severity and the cause of the problem. It is usually easier to treat this problem in a growing child since growth can be “harnessed” to correct this problem. Treatment may involve the use of palatal expanders, headgears, functional appliances, rubber bands and/or even tooth extractions. If overjet is severe in a person who is not growing or whose growth is unfavorable, jaw surgery may be the ideal option.