When the upper and lower teeth do not align properly, the condition is known as a malocclusion, or a “bad bite.” This misalignment affects the bite relationship across three dimensions: front-to-back, side-to-side, and top-to-bottom. Since dental alignment is a complex three-dimensional arrangement, it is possible for a person to experience issues in more than one plane simultaneously. Understanding these distinct issues clarifies how the vertical misalignment of an overbite can occur alongside the lateral misalignment of a crossbite.
Defining Overbite: Vertical Misalignment
An overbite, often called a deep bite, is a malocclusion defined by the excessive vertical overlap of the upper front teeth over the lower front teeth. A small amount of vertical overlap is normal and necessary for proper function, typically ranging from two to four millimeters. When the upper teeth cover the lower teeth by more than this amount, the condition is classified as a deep overbite.
This excessive overlap occurs in the anterior section of the mouth. A severe deep bite can cause the lower incisors to contact the gum tissue behind the upper incisors, leading to irritation and damage. The underlying causes can be skeletal (jawbone growth) or dentoalveolar (over-eruption of anterior teeth). The overbite fundamentally represents a discrepancy in the vertical plane of the bite.
Defining Crossbite: Lateral Misalignment
A crossbite is a malocclusion characterized by a misalignment in the lateral, or side-to-side, relationship of the dental arches. Unlike an overbite, a crossbite involves a horizontal mismatch where one or more upper teeth sit inside the lower teeth when the jaws are closed. In a healthy bite, the upper teeth should slightly rest outside the lower teeth all the way around the arch.
This lateral misalignment can occur in the front of the mouth, known as an anterior crossbite, where the upper front teeth sit behind the lower front teeth. It can also affect the back teeth, which is called a posterior crossbite, where the upper molars or premolars bite inside the lower ones. A posterior crossbite often indicates a narrow upper jaw compared to the lower jaw and can be unilateral, affecting one side, or bilateral, affecting both sides of the mouth.
How Both Conditions Coexist
Yes, a crossbite and an overbite can occur together, and this combination is not uncommon in orthodontic practice. These two conditions address completely different planes of dental geometry, making them independent variables that can manifest simultaneously. The overbite represents a vertical dimension problem, while the crossbite indicates a lateral dimension problem.
A patient might present with an excessive vertical overlap (deep bite) in the front teeth while simultaneously having a lateral mismatch in the back teeth (posterior crossbite). Since the underlying causes of malocclusion are a mix of skeletal and dental factors, a jaw structure can have a reduced vertical dimension alongside a narrow upper arch width. When both are present, the malocclusion is considered more complex and demands a specialized, comprehensive treatment plan.
Functional Issues and Dental Health Consequences
The combination of both an overbite and a crossbite creates a significantly more challenging environment for oral function and health. The excessive vertical overlap of a deep bite leads to premature wear on the lower front teeth, as they contact the inner surfaces of the upper teeth with too much force. This abnormal friction can cause enamel erosion, chipping, and gum recession around the lower incisors.
The presence of a crossbite, particularly a unilateral posterior one, introduces an uneven chewing pattern that can lead to asymmetrical muscle function and facial development, especially in growing patients. This uneven pressure and force distribution increases the risk of temporomandibular joint (TMJ) strain or pain. Furthermore, the misalignment makes certain areas of the mouth difficult to clean, increasing the risk of periodontal disease and bone loss over time.
Corrective Treatment Strategies
Correcting a malocclusion involving both an overbite and a crossbite requires a phased and customized orthodontic approach that addresses both vertical and lateral discrepancies. The crossbite component is frequently addressed first, particularly in growing patients, often utilizing a palatal expander to widen the upper jaw. This expansion corrects the lateral mismatch, allowing the upper teeth to align outside the lower teeth.
Overbite correction then focuses on adjusting the vertical relationship of the front teeth. Orthodontists use specific mechanics, such as intrusion (moving front teeth up) or extrusion (moving back teeth down), to open the bite vertically. Comprehensive orthodontic devices, such as traditional braces or clear aligners, apply controlled forces to move the teeth into their final, correct positions. The goal is to achieve a stable and functional bite where the vertical overlap is within the healthy 2-4 millimeter range and the lateral alignment is correct throughout the arch.