Chewing Cycle

Chewing is a rhythmic process that involves both opening and closing movements of the jaw in the sagittal plane as well as lateral movements. During the chewing cycle the lower jaw first falls away from centric occlusion towards the working side. From a position of maximum opening there is a fast closing stroke followed by a power stroke during which food is crushed between the teeth. An opening stroke completes the cycle. The entire chewing cycle is usually one continuous movement. The power stroke is the most variable part of the cycle and consists of two phases, During phase 1 (the buccal phase) the lower teeth move medially and upwards from their first contact with the upper teeth to the point of maximal intercuspation. In the shorter phase 2 (the lingual phase) the lower teeth continue to move medially but are displaced downwards as their buccal cusps slide against the palatal cusps of the upper teeth. Prominent canine teeth in both humans and great apes limit the lateral movements possible during the chewing cycle, so-called canine guidance.