Temporomandibular Joint Disorders

The lower jaw movement trajectory is defined by the dentitions.In case of dentition changes, the activity of muscular-articular component of the dentofacial apparatus also changes.The lower jaw, with normal muscle function, carries out movements allowing the chewing, swallowing, and pronunciation of sounds.The lower jaw movement is provided by the following muscles: temporal muscle -lifts and retracts the advanced lower jaw; masticatory muscle -consists of 2 parts, superficial and deep, function -lower jaw lifting, superficial part -pushes forward; medial pterygoid muscle -originates in the infratemporal fossa and attached to the jaw angle medial surface; lifts the lowers jaw when contracted; lateral pterygoid muscle -attached to the neck of the condylar process of mandible, to the capsule, the articular disc of the temporomandibular joint (TMJ); pushes the lower jaw forward with bilateral contraction, and retrudes the jaw to the opposite side with unilateral contraction.Muscles, lowering and retruding the lower jaw when contracted: mylohyoid, digastric, geniohyoid, genioglossal.Occlusion factors: articular path, Bennett movement, occlusal plane, curve of Spee, curve of Wilson, incisal path, lower jaw canine guidance.Articular path.When moving the lower jaw forward, opening in the area of the molars takes place when moving the temporomandibular joint head along the articular tubercle slope.This distance is called the articular path.Bennett movement.Lateral displacement of the temporomandibular joint working head.The lateral articular head working movement averages 1 mm.Lower jaw lateral movement consists of working articular head rotation around the vertical axis.Occlusal plane.The surface passing through the chewing surfaces and tooth cutting edges are called the occlusal plane.Curve of Spee: distal and superior curvature of the occlusal plane.Curve of Wilson: occlusal plane curvature viewed in the frontal plane is called curve of Wilson.