Chewing

Biting and grinding food in your mouth so it becomes soft enough to swallow.

Chewing Cycle

Murphy summarized six phases in the chewing cycle. They are:

Preparatory phase

In this phase the tongue positions the food within the oral cavity and the mandible deviates towards the chewing side.

Food contact phase

This is a phase of momentary hesitation in movement that occurs due to triggering of sensory receptors due to food contact.

Crushing phase

This starts with high velocity and slows down as food gets crushed. Gibbs in 1969 observed that when the central incisor is about 5 mm from closure, the jaw motion is stabilized at the working condyle and the following final closing stroke is guided by this ‘braced’ condyle.

Phase of tooth contact

With slight change in direction without delay. Here all the reflex muscular adjustments for tooth contact are made.

Grinding phase

In this phase, there is grinding movement guided by the maxillary and mandibular occlusal tables.

Centric occlusion

The mandible returns to a single terminal point before it goes into the preparatory phase.

Masticatory frequency is variable. It is usually one to two strokes per second. When the chewing cycle is recorded in the sagittal plane using a pantograph, a characteristic ‘teardrop tracing’ is obtained. When the mandible moves along the posterior incline (PI) of the teardrop, food is sliced by the cuspal inclines. The apex of the tracing is formed when the opposing teeth are in cusp to fossa relationship (CO) and trituration of food occurs. Finally as the mandible moves to make the anterior incline (AI) of the teardrop, dispersion of churned food along the sluiceways occur.

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