Prognathism: Abnormally Prominent Lower Jaw—Causes, Effects, and Treatment

Definition

Prognathism (mandibular prognathism) is a skeletal discrepancy where the mandible protrudes anteriorly relative to the maxilla, resulting in a Class III malocclusion (underbite).

Etiology

• Genetic – Familial (e.g., Habsburg jaw); syndromes (Crouzon, Acromegaly).
• Developmental – Excessive mandibular growth or deficient maxillary growth.
• Acquired – Trauma, tumors (osteosarcoma, giant cell lesion), endocrine disorders.

Clinical Features

• Protruding chin, concave facial profile.
• Class III malocclusion (anterior crossbite).
• Speech, mastication, TMJ dysfunction possible.

Treatment

• Orthodontics alone – Dental camouflage (mild cases).
• Orthognathic surgery (BSSO, Le Fort I) – Skeletal correction (moderate-severe).
• Combined ortho-surgical approach – Standard for significant discrepancies.