Mandibular movements: Border movements and Envelope of Motion 

Mandibular movements occur around the Temporomandibular joint (TMJ), which is capable of making complex movements in 3 dimensional planes. The maxillomandibular relation varies every second during mandibular movements. A through knowledge of these movements is essential prior to recording the jaw relation. The major determinants of mandibular movements are: Condylar guidance which acts as the posterior determinant, Incisal guidance which is the anterior determinant and neuromuscular factors which is related to the muscles of mastication. Border movements are mandibular movements at the limits dictated by anatomic structures in a given plane. Border movements recorded in horizontal plane produce a characteristic 'Diamond' tracing, in sagittal plane records a 'Beak' tracing and in coronal plane, a "Shield' tracing. Combining the border movements of all the three planes produces a three dimensional limiting space within which mandibular movements are possible, which is termed as Envelope of Motion.