An uneven jaw, technically known as mandibular asymmetry, describes a visible difference in the size, shape, or position between the left and right sides of the lower facial structure. While no human face is perfectly symmetrical, a noticeable imbalance affects both appearance and the functionality of the bite and jaw movement. This imbalance often relates to the deviation of the chin or the lower dental midline from the center of the face. Addressing this condition requires accurately diagnosing the origin of the imbalance.
Identifying the Cause of Jaw Asymmetry
Finding a solution begins with a thorough examination by specialists, typically an orthodontist, an oral and maxillofacial surgeon, or a dentist. Diagnosis often requires advanced imaging, such as three-dimensional Cone-Beam Computed Tomography (CBCT) scans, to precisely map the underlying skeletal and soft tissue structures. Unevenness is broadly categorized into three origins: developmental, acquired, and functional.
Developmental or skeletal asymmetry arises from differences in how the jawbones grew during childhood and adolescence. Conditions like hemimandibular hyperplasia cause one side of the lower jaw to grow excessively compared to the other. This results in a structural imbalance, often involving a discrepancy in the length or volume of the mandibular ramus or condyle.
Acquired asymmetry occurs after the jaw has matured, often resulting from an external event or disease. Common causes include traumatic injuries, such as fractures that heal improperly, or conditions causing inflammatory changes to the temporomandibular joint (TMJ) condyle. These factors can lead to the slow resorption or destruction of bone on one side, resulting in a progressive shift of the jaw.
Functional asymmetry results from issues related to the muscles or the dental bite, rather than the bone structure. Temporomandibular Joint Disorder (TMD) can cause the jaw to shift when opening or closing due to muscle spasm or joint disc displacement. Habitual actions, such as consistently chewing on one side or poor posture, can also lead to uneven muscle development that pulls the jaw off-center.
Non-Surgical and Dental Fixes
For cases of mild to moderate asymmetry, particularly those rooted in dental or muscular imbalances, non-surgical and restorative dental approaches are effective. Orthodontic treatments are frequently employed when teeth are misaligned, which may contribute to or camouflage a slight underlying skeletal deviation. Both traditional braces and clear aligners apply controlled forces to reposition teeth, aligning the upper and lower dental arches to improve the bite (occlusion).
Orthodontists may use microimplants, which are small temporary screws placed into the jawbone, as anchors for applying precise directional forces. This technique assists in the non-surgical movement and repositioning of the lower jaw relative to the upper jaw, especially in younger patients whose growth plates are still active. This approach aims to achieve a more balanced appearance by shifting the dental midline and encouraging skeletal remodeling.
Cosmetic adjustments address soft tissue components that contribute to unevenness. Dermal fillers, such as hyaluronic acid, can be injected to add volume to deficient areas along the jawline, creating the perception of greater symmetry. Botulinum toxin (Botox) injections treat functional asymmetry caused by an overdeveloped masseter muscle on one side. By temporarily relaxing the muscle, the treatment reduces its size, leading to a more streamlined and symmetrical contour in the lower face.
Dental reconstruction techniques, such as porcelain veneers or crowns, correct an “occlusal cant,” which is a sloped appearance of the biting surface of the teeth. Although these restorations do not change the underlying jawbone, they cosmetically mask the issue by altering the visible length and angle of the teeth. Reshaping the teeth allows the dentist to create a new, level biting plane that appears parallel to the facial midlines, improving the overall balance of the smile and lower face.
Physical therapy and specialized appliances are recommended for functional asymmetry stemming from TMD. Treatments include custom-fitted occlusal splints worn at night to stabilize the jaw joint and relax the surrounding musculature. Physical therapy exercises improve jaw mobility, strengthen weaker muscles, and promote a more centered resting position of the mandible.
Corrective Jaw Surgery
For severe cases where the structural difference is significant and affects functionality, corrective jaw surgery is the required treatment. This procedure is reserved for instances where the jawbones are mismatched in size or position, leading to problems with chewing, speaking, or breathing that non-surgical methods cannot resolve. The goal is to physically reposition the maxilla (upper jaw), the mandible (lower jaw), or both, to achieve proper alignment and facial harmony.
The treatment spans two to three years and requires collaboration between an oral and maxillofacial surgeon and an orthodontist. Pre-surgical orthodontics, lasting between 12 and 18 months, is the initial step where braces or aligners straighten the teeth. This positions the teeth correctly on the underlying jawbones, ensuring they will fit together perfectly once the skeletal components are moved during the operation.
The surgical procedure is performed under general anesthesia. It involves making precise cuts, called osteotomies, in the jawbones, often accessed through incisions inside the mouth to avoid visible external scarring. The surgeon moves the bone segments into their planned, corrected positions. The segments are then secured using small, biocompatible titanium plates and screws, which hold the jaw in its new alignment until healing is complete.
The recovery phase involves a short hospital stay, typically one to three days, for initial monitoring and pain management. Initial healing is achieved within six weeks, during which the patient must maintain a liquid or soft food diet to protect the surgical site. Complete bone consolidation and the final resolution of swelling can take six to twelve months. This procedure corrects the asymmetry and improves the functional aspects of the jaw and bite.