crossbite

Crossbite is a dental alignment condition in which one or more teeth of the upper jaw bite inside the teeth of the lower jaw. It can be anterior (front teeth) or posterior (back teeth) and may involve one side (unilateral) or both sides (bilateral). It can be dental in origin, meaning tooth position, or skeletal, reflecting jawbone discrepancy, and may be present in a single bite or be part of a broader occlusal misalignment.

Anterior crossbite involves the upper front teeth biting on or behind the lower front teeth; posterior crossbite involves the upper molars or premolars biting inside the lower cheek teeth. Skeletal crossbite indicates a mismatch in jaw width or progression and may require different treatment than a primarily dental misalignment.

Causes include genetic factors affecting jaw size and tooth alignment, early loss of primary teeth, prolonged pacifier use, thumb or finger sucking, tongue thrust, mouth breathing, crowding, and asymmetrical eruption. Trauma and developmental disturbances can also contribute.

Diagnosis relies on clinical examination of occlusion, intraoral photographs, and dental casts or three-dimensional imaging. Radiographs help assess jaw position, skeletal relationships, and airway considerations. A functional bite shift may be observed when the bite is closed or opened.

Treatment depends on age and underlying cause. In children, interceptive approaches such as rapid maxillary expansion or removable/ fixed appliances can widen the upper jaw and correct transverse discrepancies. In adolescents and adults, braces or clear aligners move teeth; skeletal crossbites may require orthognathic surgery for substantial jaw discrepancies. Early intervention improves long-term outcomes.

Untreated crossbites can lead to asymmetric facial growth, abnormal tooth wear, periodontal stress, and temporomandibular joint problems. With appropriate treatment, occlusion and function can improve.