Underbite

Underbite is a dental and facial condition in which the lower front teeth and jaw project in front of the upper teeth and jaw. It is commonly classified as Class III malocclusion and may be referred to as a reversed overjet or prognathism, reflecting both dental misalignment and jaw relationship.

Causes of an underbite include genetic predisposition and skeletal imbalances, such as a relatively small upper jaw (maxilla) or an overdeveloped lower jaw (mandible). Environmental factors, including mouth breathing, early loss of baby teeth, or certain oral habits, can contribute. In many cases, the condition is present from childhood and may become more pronounced as growth occurs.

Signs and potential consequences include a lower set of teeth that sit ahead of the upper teeth, a prominent chin, and difficulties with biting or chewing. Patients may experience uneven tooth wear, speech problems, and in some cases sleep-disordered breathing or temporomandibular joint discomfort.

Diagnosis involves a clinical examination by a dentist or orthodontist, along with dental impressions, photographs, and imaging. Panoramic and lateral cephalometric radiographs help distinguish dental from skeletal causes and guide treatment planning.

Treatment depends on age and severity. In children, interceptive orthodontics may use functional appliances to guide growth or a reverse-pull facemask to advance the maxilla, sometimes with braces and elastics. In adults, orthognathic surgery to reposition the jaws is common, typically combined with orthodontics, followed by a retention phase to maintain results.

Prognosis improves with early, appropriate intervention. Untreated, underbites can lead to bite dysfunction, uneven tooth wear, jaw pain, or breathing-related issues in some cases. See also: Malocclusion; Orthodontics; Orthognathic surgery; Sleep apnea.