Figure 1. The constrained lever model of jaw biomechanics.

During biting, the bite point (b) and the temporomandibular joints on the working side (ws) and balancing side (bs) form a “triangle of support” that changes shape when biting on different teeth. During a premolar bite (A) the resultant vector of the jaw adductor muscles (v) passes through the triangle, producing compression (green circles) at all three points. However, during some molar bites (B) the vector falls outside the triangle when the muscles are being recruited equally on both sides of the head, producing compression at the bite point and bs joint, but distraction (red circle) at the ws joint. The recruitment of the balancing side muscles must be lessened in order to eliminate this distraction, thereby causing the vector to shift its position towards the working side and back into the triangle (yellow arrow).