Hi frens, this is Dr. Bhavana Gupta, M.D.S Oral pathology

1. MASTICATION
Dr. BHAVANA GUPTA

2. INTRODUCTION
• The amount of food that a person ingests is determined
principally by the intrinsic desire for food- hunger.
• The type of food that a person preferentially seek is
determined- appetite.
• Mechanical aspects of food ingestion- mastication and
deglutition.
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3. 3
MASTICATION

4. MASTICATION (chewing)
• Cutting the food substances into small particles and grinding
them into a soft bolus.
• Cutting action- anterior teeth.
• Grinding action- posterior teeth.
• Jaw muscles working together can close the teeth (incisors)-
force of 55 pounds, & molars 200 pounds.
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5. • For food to be broken down, the food is to be
positioned by the tongue in conjuction with
the buccinator muscles of the cheek between
the occlusal surface of the teeth.
• The tongue transports solid and liquid food
within the oral cavity.

6. Mastication:
• Processes involved in food preparation,
including moving un chewed food onto the
grinding surface of the teeth, chewing, it, and
mixing it with saliva in preparation for
swallowing
Deglutition:
• swallowing

7. EVOLUTION OF MASTICATION
• Arrangement of jaw bones- dental
arcade. Evolution from straight rows
to curved parabolic rows.
• Reduction of molars series as a
whole & reduction of 3rd molar, trend
seen in later stage of human
evolution. Associated with
preparation of food by cooking,
lessens the need of prolonged
mastication.
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Ape to Man

8. DEVELOPMENT OF MASTICATION
Mouth:
• Stomatodaeum and foregut-
separated by
buccophayngeal membrane.
• Epithelium lining-lips,
cheeks, palate, is
ectodermal.
• Teeth and gums- ectodermal
origin.
• Epithelium of tongue-
endoderm. 8

9. SIGNIFICANCE OF MASTICATION
• Food stuffs to smaller particles.
• Increases salivary secretion.
• Mixing of saliva with food substance thoroughly.
• Lubrication and moistening of dry food.
• Appreciation of taste of the food.
• Important for digestion.
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10. STRUCTURES INVOLVED IN
MASTICATION
• TEETH
• LIPS
• CHEECKS
• TONGUE
• PALATE
• GINGIVA
• PERIODONTIUM
• MUSCLES OF MASTICATION
• TMJ

11. • Food taken into mouth is crushed by the
grinding action of the teeth.
• This makes it suitable for swallowing.
• Breakdown of food into smaller particles
increases the surface area of the food
particles which in turn increases the
enzymatic action ..leading to effective food
digestion.
• Tongue plays an important role while chewing
by controlling the movement of food and
formation of bolus.

12. Jaw movements during mastication
• Vertical movement of mandible/lower jaw
• Transverse movement of mandible.
• Protrusion and retrusion of the tongue.
• While chewing jaw moves rhythmically and
opening and closing occurs in a series of cycle
called CHEWING CYCLE.
• Movement of mandible during chewing is in –
TEAR DROP PATTERN

13. • A single chewing cycle is divided into four
phases-
1. Minimum opening phase.
2. Faster opening phase
3. Fast closing phase.
4. Slow closing phase.
• The masticatory sequence consists of many
chewing cycles and extends from ingestion to
swallowing.

14. The masticatory sequence is divided
into three periods
• 1.PREPARATORY-
• food is transported back to posterior teeth
• 2.REDUCTION
• Immediate period where food is ground up.
• 3.PRESWALLOWING
• Final period where bolus is formed for
swallowing.
• Movement of jaws in these period differs
depending on the type of food stuff and the
species of animal.

15. Muscles
• 1.Elevators –
• Masseter, medial pterygoid, temporalis.
• 2. Depressors-
• Lateral pterygoid, digastric, mylohyoid,
geniohyoid
• 3. PROTRUSION-
• Medial pterygoid, lateral pterygoid, massater
• 4. RETRACTION-
• Temporalis
• 5.Side wise movement-
• Medial and lateral pterygoid

16. MASTICATORY CYCLE
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• Pathway of mandible in
chewing.
• Opening phase- teeth &
condyle downward &
forward.
• Closing phase- elevated,
lateral movement of
mandible.
• Intercuspal phase- forward
and medial.

17. • 15 chews in a series.
• Jaw opening greatest- food first enters.
• Average jaw opening-16-20 mm
• Lateral displacement-3 and 5 mm.
• Duration- 0.6 and 1.0 seconds.
• Duration decreased, chewing force increased.
• Consistency, shape, size, taste-bolus.
• Tooth contact- 17.5 minutes in 24 hours.
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18. REFLEX
• Jaw closing reflex
• Jaw opening reflex
• Unloading reflex.

19. 1. JAW CLOSING REFLEX
• Example of stretch reflex and is similar to knee-
reflex.
• Produced by giving a sharp downwards tap on
the chin when mandible is out of occlusion
• The reflex activity of massater brings the teeth
into occlusion.

20. • Depressor muscles relax during Jaw –jerk
reflex
• This cycle is about 7-12 milliseconds.
• It occurs because of stretching of muscle
spindles of massater

21. 2. Jaw –Opening reflex
• Initiated by mechanical stimulation of the
periodontal ligament and mucosal
mechanoreceptors.
• The result is excitation of jaw-opening muscles
and inhibition of jaw-closing muscles
• This is not a monosynaptic reflex and at least
one interneuron is involved in the reflex
pathway
• It is initiated by the stimulation of numerous
other areas innervated by the trigeminal and
other cranial nerve

22. • 3. THE UNLOADING REFLEX
• The unloading reflex helps protect the teeth
during a heavy occlusal load.
• This reflex stops mandibular closure by
decreasing masseter and digastric muscle
activity.

23. CHEWING PATTERN IN CHILDREN &
ADULTS
• Chewing patterns of adult- opening stroke is medial to wide
lateral closing stroke.
• Child-opening stroke- typically lateral. Less wide lateral
closing stroke.
• Children- less velocity.
• Duration of chewing cycle-constant.
• Central pattern of generator.
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24. NERVOUS CONTROL OF
MASTICATION
• The centre of mastication is located in
medulla and cerebral cortex.
• Chewing process- chewing reflexes.
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25. Bolus of
food
Initiates
reflex
inhibition of
muscles of
mastication
Lower jaw
to drop
Rebound
contraction.
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Chewing reflex

26. INFLUENCE OF FOOD
PROPERTIES ON CHEWING
• Food hardness is sensed during mastication.
• Food characteristics- number of chewing cycles needed
to prepare the food for swallowing.
• Volume of the food. Larger portion sizes- subject
needed more time, chewing strokes.
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27. • Dry and hard products- more chewing cycles.
• Dry product needs a longer time in the mouth to allow for
enough secretion of saliva.
• Buttering dry foods (cake and toast) significantly reduced the
number of chewing cycles of these foods.
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28. MASTICATORY EFFICIENCY WITH
AGING
• Atrophy of buccal musculature.
• Unreplaced missing teeth, loose teeth, poorly fitting dentures,
unwillingness to wear dentures.
• Poor chewing habits- digestive disturbances.
• Select foods requiring less chewing effort.
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29. CONCLUSION
For food to be processed optimally in the alimentary tract,
appropriate mixing must be provided. The requirements for
mixing and propulsion are quite different at each stage of
processing, multiple autonomic nervous and hormonal
feedback mechanism control each aspect of these so that
they will both occur optimally, not too rapidly, not too
slowly.
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30. SUMMARY
Ingestion of food involves following process:
• Placing of food into mouth.
• Mastication, i.e. chewing the food into smaller pieces,
• Lubrication of food with saliva,
• Swallowing, i.e. deglutition.
• Stages of deglutition- oral stage, pharyngeal stage,
esophageal phase. 30

31. REFERENCES
• Guyton & Hall, Textbook of Medical Physiology, 9th ed, 813-
16.
• K. Sembulingam, Essentials of Medical Physiology, 3rd ed,
211-14.
• G.K.Pal, Medical Physiology for Dental students, 281-82.
• Indu Khurana, Essentials of Medical Physiology, 1st ed, 350-
56.
• Chaudhury, Textbook of Medical Physiology, 4th ed, 104-07.
• Andrew Davis, Blakeley, Human physiology, 843-45
• Ganong, Medical physiology, 18th ed, 456-58.
• Carranza, Newman, Clinical periodontology, 8th ed, 177-78.
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32. QUESTIONS FOR MASTICATION
• LONG QUESTION
• 1.Describe the sequence of mastication and the
significance of mastication.
• SHORT QUESTIONS
• Enumerate and describe briefly muscles of
mastication.
• Muscle activity can be studied by _____________
• Jaw jerk reflex is a type of which
reflex_____________

33. THANK YOU
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