Introduction
Force alone doesn't tell you what a tooth or the bone feels. What matters is pressure: force spread over an area. The same force concentrated on a small cusp tip crushes food; spread over a large root surface it barely stresses the bone.
σ is pressure (Pa or kg/cm²), P the force and F the area it acts on.
Masticatory pressure
Masticatory pressure is the overall name for the crushing effect of mastication. It has two sides: the occlusal pressure that processes food, and the opposite periodontal pressure that the supporting tissues must bear.
Occlusal pressure
The pressure between the occlusal surfaces of opposing teeth, the main physical factor in breaking up food.
Pₛ is the specific masticatory force on the tooth and Fₒ the area of its occlusal surface.
Molars get the biggest force but also have the widest occlusal surfaces; premolars are narrower, and incisors and canines have only small edges. Force and area fall together from back to front, so occlusal pressure is roughly the same in every part of the arch. This is form adapted to function, an outcome of evolution.