Masticatory Cycle Phases

The pathway of mandible during chewing is referred to as chewing cycle.

Characterized by opening, closing, retrusive, protrusive & lateral jaw movements

The chewing cycle can take many forms; classically tear drop shape when viewed in frontal or saggital plane

There are about 15 chews in a series from the time of food entry until swallowing

Avg jaw opening during chewing is between 16-20mm

Duration of each cycle – 0.8 – 1.0 sec

The 3 phases Of Masticatory Cycle:

Opening phase (mandible is depressed)
Closing Phase (mandible is elevated)
Occlusal / Intercuspal phase

Opening phase:

Intake of bolus in the mouth – mouth opens by reflex inhibition of elevators

Isotonic contraction of depressors

Condyles move forward & downward

Divided into two types:

Slow opening
Rapid opening

Closing Phase:

In the beginning of this phase – elevators show isotonic contraction

In the end of this phase – elevators (masseter) shows isometric contraction

Gradual transition from isotonic contraction to isometric contraction

Condyles –

On working side – moves back almost horizontally
On balancing side – moves upwards & backwards in reverse direction

Intercuspal phase:

Tooth to tooth contact occurs
Path of mandibular closure determined by slide of mandibular teeth along the cuspal inclines of maxillary teeth
First cuspal contact B-B, then L-L, then cusps glide sideways

The 3 Possibilities:

Failure to penetrate the intervening food particle even after power stroke
Slow penetration of food particle & tooth contact
Sudden breakage of food particle leading to unloading reflex & separation of occluding surfaces

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