protraction

Protraction is a term used in anatomy and biomechanics to describe the forward movement or anterior displacement of a body part in relation to a reference point. It is the opposite of retraction, which describes backward movement. Protraction is typically defined in the horizontal plane and can occur at joints such as the jaw or shoulder girdle, or as part of orthodontic treatment.

In the jaw, mandibular protraction, commonly called protrusion, is the forward movement of the mandible relative to the skull. It participates in biting and speaking and is controlled by muscles of the jaw including the lateral pterygoids and the masseter. Excessive or restricted protraction can be a feature of temporomandibular disorders.

In the shoulder girdle, scapular protraction is the forward and medial movement of the scapula away from the spine, along the rib cage. It is produced mainly by the serratus anterior and pectoral muscles and is countered by retraction movements produced by the rhomboids and middle trapezius. Protraction is important in pushing actions and functional shoulder mechanics.

In orthodontics, protraction can refer to the forward movement of the upper jaw (maxilla) or lower jaw (mandible) through appliance therapy. Maxillary protraction, often using a facemask or headgear, aims to correct Class III malocclusion by guiding the maxilla forward. Protraction is typically part of a broader treatment plan that may include expansion.

Etymology and related terms: protraction derives from Latin protractus, meaning dragged forward. See also retraction, protrusion, and other directional movements in anatomy and dentistry.