An overbite, known clinically as a Class II malocclusion, is a common alignment issue where the upper teeth and jaw are positioned forward relative to the lower jaw. This condition affects the aesthetics of a smile and disrupts the proper function of the bite. Addressing this misalignment requires understanding the underlying causes and a tailored orthodontic approach. Treatment plans range from interceptive measures in children to complex procedures for adults, all aimed at achieving a balanced relationship between the upper and lower arches.
Defining the Overbite
An overbite is a dental alignment where the upper front teeth vertically overlap the lower front teeth significantly. A normal bite features a slight vertical overlap of approximately one to two millimeters. When this vertical overlap becomes excessive, generally exceeding two to four millimeters, it is diagnosed as an overbite. The severity determines whether it is a minor misalignment or a deep bite, which can completely cover the lower front teeth.
In severe instances, the lower teeth may contact the gum tissue behind the upper teeth, known as an impinging overbite. This excessive overlap can lead to complications, including uneven wear on the tooth enamel, gum irritation, and discomfort in the temporomandibular joint (TMJ). Correction is necessary to restore proper bite mechanics, preserve tooth structure, and improve the patient’s facial profile. An overbite is a vertical issue, distinct from an overjet, which describes a horizontal protrusion of the upper teeth.
Underlying Causes and Risk Factors
The development of an overbite stems from a combination of hereditary factors and environmental influences that affect jaw growth and tooth alignment. Genetic predisposition is a factor, as the size and position of the jawbones are inherited, often leading to a disproportionately smaller lower jaw (mandible) or a larger upper jaw (maxilla). These skeletal discrepancies create the foundation for a Class II malocclusion.
Prolonged non-nutritive sucking habits, such as thumb or pacifier use past the age of three or four, apply consistent external pressure that physically alters developing oral structures. This pressure can push the upper front teeth forward and the lower front teeth backward, exacerbating the vertical and horizontal overlap. Such habits also contribute to a narrower upper jaw, as cheek muscles exert force inward while the tongue is displaced downward.
Another factor is the premature loss of primary (baby) teeth, often due to decay or trauma. When primary teeth, particularly the molars, are lost too early, adjacent permanent teeth can drift into the empty space, reducing arch length. This loss of space disrupts the eruption pathway of the adult teeth, contributing to crowding and impacting the front-to-back relationship of the dental arches. Early loss of primary canines can also cause the lower incisors to tip inward, increasing the depth of the overbite.
Treatment Options for Correction
Correction of an overbite depends on the patient’s age, the severity of the malocclusion, and whether the issue is primarily dental or skeletal. For growing patients, typically between the ages of 8 and 16, growth modification appliances are used to correct jaw alignment by harnessing natural development.
The Herbst appliance is a fixed functional device that connects the upper and lower arches, forcing the lower jaw into a forward position. This device stimulates mandibular length increase and pushes upper molars backward, achieving a Class I bite relationship within six to eight months.
Headgear is another growth-modifying appliance used for Class II correction, primarily by restraining the forward growth of the upper jaw. The cervical-pull headgear uses a neck strap to apply a backward and downward force, while the high-pull variation uses a strap over the head to apply a backward and upward force. This external appliance requires dedicated wear for 12 to 14 hours per day, often for one to two years, to effectively control the size of the maxilla.
For patients who have completed skeletal growth, standard orthodontic treatment with braces or clear aligners can move teeth to camouflage a mild to moderate skeletal discrepancy. This approach involves repositioning the teeth to align the bite, but it does not change the underlying bone structure.
In cases of severe skeletal overbites, such as those with an overjet greater than 10 millimeters or a pronounced chin recession, orthognathic surgery is indicated to permanently reposition the jaws. This surgical-orthodontic approach involves advancing the lower jaw to create proper skeletal harmony and is usually reserved for non-growing adolescents or adults.
Preventive Measures and Early Intervention
Preventive strategies focus on mitigating environmental factors and guiding favorable jaw development. The American Association of Orthodontists recommends that all children have their first orthodontic evaluation no later than age seven. At this age, the orthodontist can assess the emerging permanent teeth and the relationship between the jaws, which is often referred to as interceptive or Phase I treatment.
Addressing prolonged oral habits is a primary focus of prevention, as stopping thumb sucking or pacifier use by age three often allows the teeth and jaw to self-correct. If the habit persists beyond age five or six, an appliance like a palatal crib may be bonded to the upper teeth to create a physical barrier and interrupt the habit. This device is worn for several months until the habit is fully broken, removing the continuous force that contributes to the overbite.
Phase I treatment, when needed, typically begins between the ages of seven and ten. It may involve appliances like palatal expanders to widen a narrow upper jaw or functional appliances, such as a Twin Block, to encourage forward growth of the mandible. This treatment aims to guide jaw growth and create space for the permanent teeth, which can reduce the severity of the overbite and simplify or eliminate the need for more extensive treatment later. Another preventive measure is the use of space maintainers when a baby tooth is lost prematurely, ensuring the permanent tooth has room to erupt correctly and preventing adjacent teeth from drifting.