A deep bite, or deep overbite, is a common form of malocclusion, which is the technical term for a misalignment of the upper and lower teeth. This condition is defined by an excessive vertical overlap of the upper front teeth over the lower front teeth when the jaws are closed. While a slight overlap is normal for a healthy bite, a deep bite is a deviation that can lead to various functional and health issues that extend beyond aesthetic concerns. Correcting this vertical discrepancy is a primary goal in orthodontic treatment to ensure proper function and long-term oral health.
Defining Excessive Vertical Overlap
A normal overbite involves the upper incisors covering the lower incisors by approximately 2 to 4 millimeters, or about 5% to 25% of the visible surface of the lower teeth. This slight overlap is necessary for efficient chewing and protecting the front teeth. A deep bite occurs when this vertical overlap significantly exceeds the normal range, typically covering the lower teeth by more than 40%.
In severe cases, the overlap is so pronounced that the lower front teeth are completely obscured by the upper teeth, sometimes called a cover bite. An impinging deep bite is a more serious presentation where the lower incisors contact and traumatize the gum tissue behind the upper teeth, or the upper incisors impact the lower gum tissue. This constant trauma can cause gum recession, inflammation, and sores.
Underlying Factors Contributing to Deep Bites
The development of a deep bite is often multifactorial, stemming from a combination of skeletal, dental, and muscular elements. Skeletal factors relate to the underlying structure and growth pattern of the jawbones. Individuals frequently exhibit a horizontal growth pattern, characterized by a shorter lower third of the face and a reduced anterior facial height. This pattern involves a forward and upward rotation of the lower jaw, which effectively deepens the bite.
Dental factors involve the position and eruption of the teeth, independent of jaw structure. A common contributor is the over-eruption (supraeruption) of the upper or lower incisors, meaning the front teeth have moved too far out of the jawbone. Conversely, the under-eruption (infraocclusion) of the posterior teeth can cause the front teeth to close too deeply because the back teeth do not provide enough vertical support. The excessive curvature of the biting surface of the lower teeth, known as an exaggerated Curve of Spee, is also strongly associated with deep bites.
Muscular and functional factors also play a part in the bite’s development. Habits such as teeth grinding or clenching can cause excessive wear on the back teeth, reducing the vertical dimension of the bite and deepening the overlap. The premature loss of multiple posterior teeth without replacement can cause the overall bite to collapse, allowing the front teeth to overlap further.
Health and Functional Consequences
The mechanical issues caused by a deep bite can result in significant long-term damage to the dentition and surrounding structures. A common issue is accelerated wear (attrition) on the front teeth, where the lower incisors repeatedly strike the palate or the back surfaces of the upper incisors. This friction wears down the protective enamel, exposing the sensitive underlying dentin and increasing the risk of chipping or fracture.
The excessive vertical overlap can also strain the temporomandibular joint (TMJ). This stress leads to symptoms like chronic jaw pain, headaches, clicking or popping sounds in the joint, and stiffness in the jaw muscles. Impingement on the gum tissue behind the upper teeth can cause chronic inflammation, gum recession, and periodontal problems.
From an aesthetic perspective, a deep bite can alter the appearance of the lower face. The lower third of the face may appear compressed or shorter, which can contribute to an aged look. In severe cases, the lower jaw may appear pushed backward, creating the perception of a receding or weak chin. Correcting the deep bite often improves both aesthetics and functional harmony.
Orthodontic Treatment Approaches
Orthodontic treatment aims to reduce the excessive vertical overlap, with the chosen method depending on the patient’s age and the underlying cause. One common approach uses bite planes or bite turbos, which are small ramps placed on the back of the upper front teeth or the biting surfaces of the back teeth. These appliances temporarily prevent the front teeth from fully contacting, allowing the posterior teeth to erupt (extrude), which effectively opens the bite. This process, known as relative intrusion, is often effective in growing patients.
For adults and cases where the front teeth are over-erupted, the focus shifts to true intrusion, which involves pushing the anterior teeth back into the jawbone. This movement is precisely controlled using specialized archwires, such as a reverse Curve of Spee archwire, or temporary anchorage devices (TADs). TADs are small implants that provide a stable anchor point for applying force. Intrusion of the incisors is considered a stable method for deep bite correction in non-growing patients.
The treatment plan often utilizes traditional fixed braces or clear aligners in conjunction with these specific appliances to achieve overall tooth alignment. Extrusion of the posterior teeth is preferred when the lower facial height is short, while intrusion of the incisors is indicated when there is excessive gum tissue visible when smiling. The goal is to establish a balanced bite that removes damaging vertical forces and prevents future complications.