A deep bite, or excessive overbite, is a common form of dental misalignment where the upper front teeth significantly overlap the lower front teeth when the mouth is closed. While a certain degree of vertical overlap is expected in a healthy bite, an excessive overlap can lead to numerous functional and health issues. This misalignment is classified as a malocclusion, a condition affecting the proper relationship between the upper and lower dental arches. Recognizing the difference between a normal overbite and an excessive one is the first step in understanding why treatment is often necessary. The condition requires careful diagnosis and a tailored treatment approach.
Defining Excessive Vertical Overlap
A deep bite is defined by the extent of the vertical overlap between the upper and lower incisors. In a normal, healthy bite, the upper front teeth should cover approximately 20 to 40 percent of the crowns of the lower front teeth, measured as a vertical overlap of about two to four millimeters.
A deep bite exists when this vertical overlap exceeds the normal range, often covering more than half of the lower incisors. In the most severe cases, the upper teeth completely hide the lower teeth, sometimes causing the lower incisors to contact the gum tissue behind the upper front teeth. The condition is sometimes categorized as an incomplete deep bite or a complete deep bite. The most severe form, called an impinging overbite, occurs when the lower teeth bite into the roof of the mouth or the gum tissue.
Common Etiological Factors
The development of a deep bite is often due to a combination of skeletal, dental, and muscular factors. Skeletal factors involve discrepancies in the jaw structure, where the lower third of the face may be shorter than average, creating a reduced vertical dimension. This often results from a horizontal growth pattern of the jawbones during development.
Dental factors include the over-eruption of the front teeth (supraocclusion) or the under-eruption of the back teeth (infraocclusion). When the back teeth do not erupt enough, the bite naturally deepens in the front. The loss of posterior teeth can also remove support, allowing the bite to collapse and the front teeth to overlap excessively.
Muscular factors play a role, involving habits like chronic teeth clenching (bruxism) or hypertonic masticatory muscles. Abnormal muscular habits, such as a lateral tongue thrust, can prevent the proper eruption of the back teeth, contributing to the deep bite. Diagnosing the underlying cause for each patient is complex due to these varied factors.
Health and Functional Consequences
An untreated deep bite can cause significant functional problems and health risks to the oral structures.
Excessive Tooth Wear
One of the most common issues is excessive tooth wear, particularly on the biting edges of the lower incisors and the inner (palatal) surfaces of the upper incisors. Continuous friction between the opposing teeth prematurely erodes the enamel, leading to sensitivity, chipping, and potentially exposing the inner dentin layer.
Soft Tissue Trauma
Soft tissue trauma occurs when the lower front teeth bite directly into the gum tissue behind the upper teeth. This impinging contact can cause irritation, inflammation, gum recession, and painful sores or ulcers on the palate. Over time, this chronic trauma can predispose a patient to periodontal involvement and damage the supporting structures of the teeth.
Jaw Strain and Aesthetics
The misalignment also places undue stress on the temporomandibular joints (TMJ), which connect the jawbone to the skull. This strain can lead to TMJ disorders, resulting in symptoms like chronic jaw pain, headaches, clicking sounds, and difficulty chewing. Furthermore, a deep bite can affect facial aesthetics by making the lower third of the face appear vertically compressed or shorter.
Corrective Treatment Options
Correcting a deep bite involves a tailored approach based on the patient’s age and the specific skeletal or dental components of the malocclusion.
Early Intervention (Phase I)
For growing children, early intervention, often referred to as Phase I treatment, may use functional appliances to guide jaw growth and encourage the eruption of the back teeth. Appliances like bite plates or specific types of headgear can be used to modify the developing bite before all permanent teeth have erupted.
Orthodontic Treatment
For adolescents and adults, comprehensive orthodontic treatment with fixed braces or clear aligners is the most common method. Treatment mechanics typically involve a combination of intruding the front teeth and extruding the back teeth to open the bite vertically. Intrusion involves moving the incisors deeper into the jawbone, while extrusion encourages the molars and premolars to move out of the jawbone.
The choice between these mechanics depends on the patient’s facial height. Intrusion of the front teeth is preferred for those with a normal or long lower face, while extrusion of the back teeth is often used in growing patients with a short lower face.
Surgical Intervention and Retention
In cases where a severe deep bite is combined with a major skeletal discrepancy that cannot be corrected with orthodontics alone, orthognathic surgery (jaw surgery) may be necessary to reposition the jawbones. Following any treatment, retainers are necessary to prevent the deep bite from relapsing, as the corrected position must be maintained long-term for stability.