Significance of muscles of mastication in prosthodontics

1. Muscles of MASTICATION
Dr. Neeraja M Menon
Dept. Of Prosthodontics
Coorg Institute Of Dental Sciences
PROSTHODONTIC CONSIDERATION

2. DEFINITIONS
MUSCLE (GPT 9): an organ that by contraction produces
movements of an animal; a tissue composed of contractile cells
or fibres that effect movements of an organ or part of the body.
MASTICATION (GPT 9): the process of chewing food for
swallowing and digestion

3. Border Moulding
1. Masseter:
• When the Masseter is activated it pushes the Buccinator medially against
the denture border in the area of retromolar pad.
• This is a dislodging force and the denture base should be contoured to
accommodate this action.
• This contour of the denture base is termed the masseteric groove.
.

4. Masseteric Notch Action on Denture Border
 An active masseter muscle will create concavity in the outline of the distobuccal
border and a less active muscle may result in convex border .

5. Activation of Masseteric Notch and Distal Area
 Instruct the patient to open wide and then to close against the resting force of the fingers.
 Opening wide activates the muscles of pterygomandibular raphae by stretching, which
thereby defines the most distal extension
 Instructing the patient to close against your fingers on the tray handle causes masseter
muscle to contract and push against the medially situated buccinators muscle.

7. 2. Medial Pterygoid
 It is one of the muscles that influence the
denture border in the region of the retro
mylohyoid curtain.
 Medial pterygoid is one of the elevators of the
mandible. When the patient closes his jaw , the
medial pterygoid contracts against the superior
constrictor of pharynx which is immediately
anterior to it which in turn forms the postero
lateral aspect of the retro mylohyoid curtain
which molds the border of the mandibular
denture in the region of the retromylohyoid
fossa.
Masseter
Mandible
Medial
pterygoid
Pterygomandibular
raphae

8. Border extension
Masseter
If the distobuccal flange of denture base is not contoured to allow freedom of
masseteric action, the denture will be displaced.
At the masseteric notch buccal flange must converge medially to avoid displacement due to
contraction of masseter muscle because the muscle fibers in that area are vertical and
oblique.

9. Medial Pterygoid
Care should be taken that the lingual flange should not be overextended
as the lingual nerve is closely related to the lingual flange and even the
submandibular duct can be blocked.

10. CENTRIC RELATION
 Temporalis
• As its most posterior fibers pass very close to the condyle the
posterior temporalis functions as a stabilizer of TMJ.
• It suspends the mandible in centric relation. Anterior group of
fibers which are aligned vertically hold the mandible in superior
most position.
• Temporal headaches are common in TMD’s .

11.  Lateral Pterygoid
• During closure of the mouth
the backward gliding of the
articular disc & condyle is
controlled by slow elongation of
lateral pterygoid while Masseter
& Temporalis restore the jaw to
the occlusal position.
Thus it acts as a stabilizer of
TMJ .
• It holds the condyles in centric
relation position

12. Occlusal harmony
 Unilateral failure of lateral pterygoid muscle to contract results in deviation of the mandible
toward the affected side on opening .
 Bilateral failure results in limited opening , loss of protrusion , and loss of full lateral
deviation.
 In patients with non-working side interferences ,the lateral pterygoid muscle on the
opposite of the interference is painful.

13. Disharmony Between the occlusion and the TMJ
 If the condyles must be displaced from centric relation to achieve max
intercuspation ,the lateral pterygoid must contract (pulled down).
 This causes muscle incoordination with potential for occlusal disease,
muscle pain, or disorders of TMJ

14. Tooth interferences to the centric relation arc of closure
Activates lateral pterygoid
Hyperactivity of the closing muscles

15. Placement of a simple flat interocclusal device on the anterior teeth
Separates the posterior teeth
Allow the TMJ to completely seat up into CR
Lateral pterygoid releases contraction
Co-ordinated muscle function

16. OCCLUSALSPLINTTHERAPY
Occlusal splints promote muscle relaxation by providing a platform for the
teeth that allows for equal distribution of tooth contacts, immediate posterior
tooth disocclusion in all movements (with anterior guidance), and reduced
stress on the joint. Neuromuscular harmony that follows provides for optimal
function and comfort.

17. NTI (Nociceptive Trigeminal Inhibition) Tension Suppression
System
 The direct stimulation of the periodontal ligament of the lower incisors
activates a feedback loop, which significantly limits the contraction intensity
of the closing muscles.

18. Stabilization splint
 Provides a temporary and removable ideal occlusion. Providing an ideal
occlusion by the use of splint therapy reduces abnormal muscle activity and
produces neuromuscular balance.

19. Anterior Bite Plane
It disengage the posterior teeth and thus eliminate their influence
in the function or dysfunction of the masticatory system
Anterior Bite Plane Lucia Jig Anterior deprogrammer

20. SOFT(RESILIENT) SPLINT
 These appliances are generally worn only at night and if they are
successful, will produce symptomatic relief within 6 weeks.

21. Muscle Reconditioning Splint
 It is used for its effect on the muscular reconditioning and
also to reinforce the personal responsibility of the patient.
 In all cases of persistent TMD and the presence of acute
musculoskeletal pain, despite a preliminary treatment
Michigan occlusal splint

22. CONCLUSION
 The masticatory system is extremely complex, primarily made
of bones, muscles, ligaments and teeth.
 Precise movement of mandible by the musculature is required
to move the teeth effectively across each other during
function.
 The knowledge of the anatomy physiology and mechanisms
of these muscles are basic to understand the movements.