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:
  1. Opening phase (mandible is depressed)
  2. Closing Phase (mandible is elevated)
  3. 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:
  1. Failure to penetrate the intervening food particle even after power stroke
  2. Slow penetration of food particle & tooth contact
  3. Sudden breakage of food particle leading  to unloading reflex & separation of occluding surfaces




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