What Are the Main Causes of a Deep Bite?

A deep bite, also known as an excessive overbite, is an orthodontic condition where the upper front teeth significantly overlap the lower front teeth when the mouth is closed. This vertical overlap extends beyond what is considered typical, which is usually around 30-40% coverage or 3-5 millimeters. It represents a common alignment issue that can affect both children and adults. If left unaddressed, a deep bite can lead to various problems, including accelerated tooth wear, gum damage, and discomfort in the jaw.

Genetic and Developmental Influences

Inherited traits play a substantial role in the development of a deep bite, as the size, shape, and growth patterns of the jaws and teeth are often passed down through families. If parents have a deep bite or other tooth misalignments, their children are more likely to develop similar conditions.

Uneven growth patterns of the jaw and facial bones during childhood also contribute to deep bites. For instance, a smaller lower jaw compared to the upper jaw, or an overgrown upper jaw, can result in the excessive vertical overlap characteristic of a deep bite. Skeletal deep bites often involve discrepancies in the vertical positioning of the maxilla and mandible, or insufficient development of the mandibular ramus.

During development, if the vertical growth of the molar area is less than the condylar growth, the mandible may rotate in a way that deepens the bite. This can be influenced by horizontal growth patterns of the face.

Dental Factors

Specific issues related to the teeth themselves can also cause or worsen a deep bite. The absence of posterior (back) teeth is a significant factor, as it removes the necessary support in the back of the mouth. This lack of support can cause the front teeth to over-erupt, leading to an increased overlap and deepening of the bite.

Severe tooth wear, particularly on the chewing surfaces of the back teeth, can contribute to a collapsed bite. When posterior teeth wear down, the overall height of the bite decreases, allowing the front teeth to overlap more significantly.

Abnormal eruption or positioning of certain teeth further influences bite alignment. For example, over-eruption of the upper or lower front teeth (incisor supraversion) or under-eruption of the back teeth (molar infraocclusion) can directly contribute to a deep bite. Additionally, dental crowding can lead to misalignments that promote excessive overlap of the front teeth.

Oral Habits and Muscle Dynamics

Certain learned behaviors and the forces exerted by facial and jaw muscles can contribute to the development of a deep bite. Chronic teeth grinding, known as bruxism, and jaw clenching are significant contributors. These habits can cause excessive wear on the back teeth, reducing their height and allowing the front teeth to over-erupt and deepen the bite.

Prolonged thumb sucking or pacifier use can negatively influence jaw and tooth development. These habits can alter the natural growth patterns, contributing to a deep bite. Similarly, tongue thrusting, where the tongue pushes against the front or side teeth during swallowing, can prevent posterior teeth from erupting fully, leading to a deep bite.

Muscle imbalances also play a part, as the strong forces of chewing muscles can encourage the over-eruption of front teeth. Hyperactive masticatory muscles can lead to a reduction in the vertical height of teeth. Masticatory muscle activity can be increased in individuals with a deep bite. Chronic mouth breathing, often due to airway issues, can also impact jaw development and contribute to bite alignment problems.