An overjet bite is a form of dental misalignment, or malocclusion, where the upper front teeth protrude excessively forward over the lower front teeth. This condition is a relatively common finding in orthodontic practice. While some protrusion is normal for proper bite function, an increased overjet presents both aesthetic and functional challenges for an individual.
Defining Overjet and Overbite Differences
Overjet is a measurement of the horizontal projection of the upper incisors past the lower incisors. A dentist measures the distance from the back surface of the upper teeth to the front surface of the lower teeth. This horizontal overlap is considered normal when it measures between one and three millimeters. An overjet is diagnosed when this measurement exceeds three millimeters, and severe cases can extend up to ten millimeters.
The term overjet is often confused with an overbite, but they describe different dimensions of tooth overlap. Overjet refers to the horizontal protrusion. In contrast, an overbite refers to the vertical overlap, indicating how much the upper front teeth cover the lower front teeth when biting down. An excessive vertical overlap is sometimes called a deep bite.
Factors Contributing to Overjet Development
Overjet development stems from a combination of underlying genetic factors and acquired environmental habits. Skeletal discrepancies, which are largely inherited, are a primary cause. This often involves an underdeveloped lower jawbone (mandible) or one positioned too far back relative to the upper jaw (maxilla), causing the upper teeth to protrude.
Certain childhood behaviors can contribute to or worsen an existing overjet. Prolonged habits like thumb or finger sucking, particularly past the age of four, exert continuous pressure that pushes the upper front teeth outward. Extended use of a pacifier beyond the toddler years can have a similar effect. Tongue thrusting, where the tongue presses against the back of the upper teeth when swallowing, is also a contributing factor.
Health and Functional Impacts
A significant consequence of protruding upper teeth is the increased susceptibility to dental trauma. Individuals with an overjet greater than three millimeters are nearly twice as likely to sustain injury, such as chipping or fracturing, to their front teeth. The prominent position of the teeth leaves them exposed and vulnerable to accidents or falls.
An excessive overjet can impair everyday oral functions, including difficulty biting or chewing food effectively. This misalignment may also contribute to speech impediments, such as lisping, because the tongue cannot correctly articulate sounds. Furthermore, improper alignment can place stress on the jaw joints, potentially leading to chronic headaches or temporomandibular joint (TMJ) issues. Severe protrusion can make it difficult to fully close the lips, which may lead to dry mouth and an increased risk of tooth decay.
Corrective Measures
The treatment approach for an overjet depends on the patient’s age and the severity of the underlying misalignment. In younger children, early intervention often focuses on growth modification appliances. Functional appliances, such as the Twin Block or Herbst appliance, guide the growth of the jawbones to encourage forward development of the lower jaw while the child is still growing.
For adolescents and adults, comprehensive orthodontic treatment with fixed braces or clear aligner therapy is the most common path. These appliances apply controlled forces to retract the upper teeth and align the bite. In cases where a severe skeletal discrepancy exists and cannot be resolved by orthodontics alone, orthognathic surgery (corrective jaw surgery) may be necessary. This surgical procedure repositions the jawbones to achieve proper alignment.