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MUSCLES OF MASTICATION

By Rejoy Alexander1st yr PgDept. of Prosthodontics

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INTRODUCTION

•Food is the main source of energy this energy is derived through the complicated process of digestion.

•1st step of digestion is mastication.

•Teeth, jaws, muscles of the jaws, tongue and the salivary glands aid in mastication.

•Influence of these muscles in prosthetic dentistry.

Defines the borders & peripheral extensions.

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DEFNITIONS

GPT 8•Muscle : an organ that by contraction

produces movements of an animal; a tissue composed of contractile cells or fibers that effect movement of an organ or part of the body.

•Mastication is defined as the process of chewing food in preparation for swallowing and digestion.

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• Masticatory muscle : muscles that elevate the mandible to close the mouth.

• Mainly four pairs of muscles in the mandible make chewing movements possible.

•These muscles along with accessory ones together are termed as ‘MUSCLES OF MASTICATION’.

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•These muscles can be divided into:

•BASIC MUSCLES:

- TEMPORALIS - MASSETER - MEDIAL PTERYGOID - LATERAL PTERYGOID

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• ACCESSORY MUSCLES

Muscles of tongue, lip & cheek

Suprahyoid muscles :

Mylohyoid geniohyoid stylohyoid digastric muscle (anterior

belly)

Infrahyoid muscles: Sternothyroid Thyrohyoid Omohyoid Sternohyoid

complete denture prosthodontics by John J Sharry

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DEVELOPMENT•The basic muscles of mastication develop

from the mesoderm of the first phyaryngeal arch.

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•So they receive all their innervations from the mandibular branch of the trigeminal nerve, all from the anterior division except the medial pterygoid which gets its nerve supply from the main trunk.

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MOVEMENTS OF MANDIBLE

• Movements that the mandible can undergo are:

1. Depression: As in opening the mouth.

2. Elevation: As in closing the mouth.

3. Protraction: Horizontal movement of the mandible anteriorly.

4. Retraction: Horizontal movement of the mandible posteriorly.

5. Rotation: The anterior tip of the mandible is “slewed” from side to side.

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• These movements of mandible are performed by various muscles involved in it. So, functionally, the muscles of mastication are classified as:

• Jaw elevators: MasseterTemporalisMedial pterygoid

• Jaw depressors:Lateral pterygoidAnterior digastricGeniohyoidMylohyoid

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MUSCLES OF MASTICATION

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TEMPORALIS

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TEMPORALISIt is the largest among all the mastication

muscles and is a fan shape muscle.

It has been divided into 2 heads: Deep head (anterior, middle and posterior

fibers) Superficial head (much smaller)

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Origin: From the inferior temporal line , floor of the temporal fossa and from the overlying temporal fascia of the side of the skull.

Insertion: Superior border and medial tip of the coroniod process.

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•Action:▫Elevation

(anterior fibers)▫Retraction

(posterior fibers)

•Nerve supply:▫Anterior division

of the mandibular nerve

(by two deep temporal nerves)

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Its Action is done by

•The anterior fibers during function act vertically and elevate the mandible.

•The posterior fibers diverge and become horizontal and retract the mandible.

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•Blood supply: From the maxillary artery (one of two termination of external carotid artery).

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PALPATION

The muscle is divided into three functional areas and therefore each area is independently palpated.

The anterior region is palpated above the zygomatic arch and anterior to the TMJ .

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The middle region is palpated directly above the TMJ and superior to the zygomatic arch .

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•The posterior region is palpated above and behind the ear.

•If uncertainity arises regarding the proper finger placement. The patient is asked to clench the teeth together so that the temporal muscle contracts and the fibers should be felt beneath the finger tips.

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Clinical significance

Recording Coronoid process area

•The patient is instructed to close and move his mandible from side to side and then immediately asked to open wide.

•The side to side motion records the activity of the coronoid process in a closed position whereas opening causes the coronoid to sweep past the denture periphery

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LITERATURE REVIEW

Antje Tallgren, Dr.Odont, et al. studied jaw muscle activity in complete denture wearers – A longitudinal electromyographic study. J Prosthet Dent August 1980 Vol 44 (2) Pg 123-32.

Tallgren studied the patterns of activity of some masticatory muscles in partially edentulous subjects & fully edentulous.

The study indicated that loss of posterior teeth causes imbalance in muscular patterns concerning masseter , anterior temporal muscle and digastrics muscle and wearing immediate complete upper and lower dentures revealed inactivity of the jaw closing muscles during the biting actions.

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Bengt Ingervall, Dr Odont et al. did an electromyographic study of masticatory and lip function in patient with complete dentures J Prosthet Dent March 1980 Vol 43(3) pg 266-71

Two groups of patients having new and old dentures were studied.

The results showed muscle activity during maximal biting was markedly lower in patients with new denture than in patients using the old onesNo difference in chewing activity was seen with old and new dentures

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MASSETER

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MASSETERIt consist of three overlapping layers:

The origin of the whole muscle is mainly from the zygomatic process which consists of :

The superficial layer

The middle layer

The deep layer

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SUPERFICIAL LAYER

It is the largest component that arises from the anterior two thirds of the lower border of the zygomatic arch.

Its fibers run downwards and backwards and inserts into lower half of the ramus including angle of the mandible.

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The middle layer takes its orgin from the medial surface of the anterior two-thirds and the lower border of posterior one third of the arch.

The fibers run more directly downwards to be inserted into lateral surface of the middle part of the ramus.

MIDDLE LAYER

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DEEP HEAD

The deep layer arises from the whole length of medial surface of the zygomatic arch.

The fibers pass downwards to attach to the upper part of the mandible ramus.

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•Action of masseter is mainly to elevate the mandible (antigravity action) and also helps in protrusive movement.

•It is the main powerful muscle involved in the elevation of the mandible

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•Nerve supply: By the mandibular branch of the trigeminal nerve, from the anterior division(massetric nerve).

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•Blood supply is from the Maxillary artery which is a terminal branch from external carotid artery.

•One of the interesting property of this muscle is that, internally, the muscle has many tendinous septa that greatly increase the area for muscle attachment and so increase its power.

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PALPATION

•The patient is asked to clench their teeth and, using both hands, the practitioner palpates the masseter muscles on both sides extraorally, making sure that the patient continues to clench during the procedure.

•Palpate the origin of the masseter bilaterally along the zygomatic arch and continue to palpate down the body of the mandible where the masseter is attached.

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D-Palpation of the masseter muscles

E-Bimanual palpation ofthe masseter muscles

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Clinical Significance On Denture border :•An active masseter muscle will create a

concavity in the outline of the distobuccal border and a less active muscle may result in a convex border.

•In this area the buccal flange must converge medially to avoid displacement due to contraction of the masseter muscle because the muscle fibers in that area are vertical and oblique .

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Effect of masseter muscle on the distobuccal border

A. Moderate activity will create a straight line B. An active muscle will create a concavity. C. An inactive muscle will create a convexity.

Impressions for complete denture by Bernard levin

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Activation of Masseteric notch and distal areas.

• Instruct the patient to open wide and then to close against the resting force of your fingers.

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Opening wide activates the muscles of pterygomandibular raphe 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 buccinator muscle.

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Tempromandibular joint dysfunction.

•The masseter is most often tender along the central fibers of at its insertion.

•Masseter hypertonicity is found in patients who have premature contacts on the nonworking side.

•Parafunctions such as bruxism and clenching also give rise to masseter pain that is frequently associated with pain in the temporalis muscle.

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LITERATURE REVIEW

• According to Garrett NR, Kaurich M et. al a cross-sectional study on Masseter muscle activity in denture wearers with superior and poor masticatory performance was done.J Prosthet Dent 1995 Dec vol 74 (6) 628-36.

 

The results indicated that application of more equivalent force by the right and left masseter muscles during unilateral chewing is consistent with improved chewing ability in denture wearers.

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Jacob R, Van Steenberghe et al. studied on Masseter muscle fatigue before and after rehabilitation with implant-supported prostheses. J Prosthet Dent. 1995 Mar Vol 73(3):284-9.

 Study was performed in two groups of edentulous patientsOne group consisted of patients who were rehabilitated by means of an implant overdenture and another with an implant-supported fixed prostheses

A decrease in the biting force and clenching with implant-supported overdentures was noted. The absence of a spectral shift expressed a fear of biting too hard and fracturing the prosthesis when compared with implant fixed prostheses.

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Belser UC and Hannam AG studied the contribution of the deep fibers of the masseter muscle to selected tooth-clenching and chewing tasks. J Prosthet Dent. 1986 Nov; Vol 56(5):629-35

The purpose of this study was to describe functional behaviour in the deep fibers of the masseter muscle and to define any differences in its behaviour from that of the superficial fibers.

During chewing, activity in the deep fibers of masseter muscle was distributed evenly bilaterally, whereas that in the superficial fibers of the masseter muscle was biased significantly toward the chewing side.

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Antje Tallgren, Dr.Odont, et al. studied jaw muscle activity in complete denture wearers – A longitudinal electromyographic study. J Prosthet Dent August 1980 Vol 44 (2) Pg 123-32.

Tallgren studied the patterns of activity of some masticatory muscles in partially edentulous subjects & fully edentulous.

The study indicated that loss of posterior teeth causes imbalance in muscular patterns concerning masseter , anterior temporal muscle and digastrics muscle and wearing immediate complete upper and lower dentures revealed inactivity of the jaw closing muscles during the biting actions.

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MEDIAL PTERYGOID

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MEDIAL PTERYGOID• It is also called as the Pterygoideus internus

(Internal pterygoid muscle).

• It consist of Two heads which differ in origin:

The superficial head

The deep head

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◦ SUPERFICIAL HEAD

The superficial head originates from the maxillary tuberosity.

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DEEP HEAD

The deep head originates from the medial surface of lateral pterygoid plate of the sphenoid bone.

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• The muscle inserts into the inner surface of the angle of the mandible.

• Nerve supply of the muscle comes from the main trunk of the mandibular nerve.

• Blood supply is chiefly from the maxillary artery.

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• Action:

1. Elevates the mandible .

2. Protrusion of the mandible (lateral & medial pterygoid on one side protrude the mandible to the opposite side).

3. Side to side movement (these lateral movements are achieved by lateral & medial pterygoid on both sides acting together to produce side to side movements).

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PALPATION It can be palpated by placing the finger on

the lateral aspect of the pharyngeal wall of the throat, this palpation is difficult and sometimes uncomfortable for the patient.

• Functional manipulation is done when the muscle becomes fatigued and symptomatic.

The muscle contracts as the teeth are coming in contact Also stretches when the mouth is open wide.

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G- Palpation of the medial pterygoid

muscle

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CLINICAL SIGNIFICANCE•Mandibular dysfunctions :

The medial pterygoid muscle is not usually involved in gnathic dysfunctions but when they are hypertonic, the patient is usually conscious of a feeling of fullness in the throat and an occasionally pain on swallowing.

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LITERATURE REVIEWWodd WW studied the medial pterygoid

muscle activity during chewing and clenching. J Prosthet Dent. 1986 May;Vol 55(5): 615-21.

Patterns of medial pterygoid muscle activity were consistent for ipsilateral chewing

Intercuspal clenching initiated less activity when force was directed posteriorly and more activity when directed anteriorly

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LATERAL PTERYGOID

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LATERAL PTERYGOID

•Also called as the Pterygoideus externus (External pterygoid muscle).

• It is a short conical muscle, having 2 heads: upper and lower.

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•Upper head:▫Origin: infra-temporal surface & crest of the

greater wing of sphenoid

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•Lower head:▫Origin: Lateral surface of the lateral

pterygoid plate

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▫Both the heads have the same insertion

▫These fibers run backwards and laterally to be inserted into:

a) Pterygoid fovea of the neck of the mandible

b) Articular disc c) Capsule of TMJ (anterior aspect)

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• Nerve supply is from the anterior division of the mandibular branch of trigeminal nerve(nerve to lateral pterygoid).

• Blood supply of lateral pterygoid muscle is from maxillary artery .

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• Actions of lateral pterygoid:

1. Depression of the mandible . 2 Side to side movement (lateral movement) . 3. Protrusion of the mandible.

•If the Pterygoid muscles of one side act, the other side of the mandible is drawn forward while the same condyle remains comparatively fixed.

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PALPATION• Silverman ( occlusion in prosthodontics and natural

dentition, ed 1 1962) recommended the bilateral use of tip of little finger of each hand in the back of maxillary tuberosity and as high as possible to compare the degree of pain on each side as reported by the patient.

• Schwartz and Chayes ( Facial pain and mandibular dysfunction ed 1 1968 ) suggested the use of the fore finger in much the same way.

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F-Palpation of the lateral pterygoid muscles

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•Jeffery P Okeson ( management of tempromandibular disorders and occlusion, ed. 4 1998) recommended palpation by functional manipulation, where each muscle is contracted and then stretched.

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The patient is asked to protrude the mandible against resistance & Clench on maximum intercuspation

For Inferior lateral pterygoid :

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•For Superior lateral pterygoid muscle:

The muscle contracts and stretches on clenching.

Inorder to differentiate pain arising from elevator muscle, the patient is asked to open the jaw wide.

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CLINICAL SIGNIFICANCE•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 nonworking side interferences, the lateral pterygoid muscle on the opposite of the interference is sometimes painful

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A B

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• The insertion of the lateral pterygoid in the articular disc occurs in the medial aspect of the anterior border of the disc and thus it plays a role in the T.M.J. diseases especially internal derangement.

• Some of the T.M.J. diseases have been due to an attributed variation of the function and attachment of the superior head as an etiological factor in T.M.J. diseases.

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LITERATURE REVIEW

• R. Johnstone and Mc cormick templeton studied the feasibility of palpating the lateral pterygoid muscle ( J Prosthet Dent Vol 44 (3) Sept 1980 Pg 318-23) and came to a conclusion through dissections and lateral head radiographs that it is not possible to palpate the lateral pterygoid muscle directly by conventional clinical techniques without applying pressure through the overlying superficial head of medial pterygoid muscle.

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• . Stratmann U. et al studied the clinical anatomy and palpability of the inferior lateral pterygoid muscle ( J Prosthet dent 2000 May VOL 83(5):548-54) and came to a conclusion that the inferior lateral pterygoid muscle palpation technique should no longer be considered as a standard clinical procedure because it is nearly impossible to palpate the muscle anatomically and because the risk of false-positive findings (by palpation of the medial pterygoid muscle) is high.

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ACCESSORY MUSCLES OF MASTICATION

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BUCCINATOR

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BUCCINATOR:

•It is an accessory muscle of mastication, occupying the gap between mandible and maxilla forming important part of the cheek.

•Its origin is from the maxilla and mandible adjacent to the molar teeth and from the pterygomandibular raphe

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Course and insertion :

Upper fibers gets inserted into upper lip,

Lower fibers gets inserted into lower lip,

Middle fibers decussate at the angle of the mouth, the upper fibers pass to lower lip while the lower fibers pass to the upper lip .

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•Nerve supply is from buccal branch of facial nerve.

•Blood supply is from facial artery.

•The main action of buccinator is to prevent the accumulation of food in the vestibule of mouth and to bring the food on to the occlusal table during mastication.

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CLINICAL SIGNIFICANCE•On Denture border : For buccal flange area in mandibular

impressions.

The area is moulded by massaging the cheek in an anterior-posterior direction using moderate manual pressure against the compound.This moves the fibers of the buccinators muscle and the tissues of the cheek in the direction of functional action of the buccinators muscle.

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•In maxillary impressions:

• The cheek is manually molded in anterior-posterior direction using slight finger pressure against the compound or the patient is instructed to control the amount of movement by sucking action.

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ANTERIOR BELLY OF DIGASTRIC:

Origin: It arises from the digastric fossa on the lower border of mandible on both sides of symphysis menti.

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•Insertion; into the intermediate tendon which is connected to the hyoid bone by a fibrous loop.

•Nerve supply; is through anterior division of mandibular branch of trigeminal nerve.

•Action; its main action is to depress the mandible .

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ANTERIOR BELLY AND ITS ACTION

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MYLOHYOID MUSCLE:

•It forms the floor of the mouth.

•Origin is from mylohyoid line on the internal aspect of mandible.

•Insertion; The fibers slops downwards and forwards to inter-digitate with the fibers of the other side to form the median raphe.

•This median raphe insert in the chin from above and the hyoid bone from below.

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• Action: Elevates hyoid bone,

supports and raises floor of mouth which aids in early stage of swallowing, depress the mandible.

•Nerve supply: By nerve to

mylohyoid: which is a branch of Inferior alveolar branch of mandibular nerve, which originates before it enters inferior alveolar canal.

MYLOHYOID MUSCLE

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•Blood supply: by Facial artery and Lingual artery.

•This muscle provides a separation between the submandibular and sublingual salivary glands.

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CLINICAL SIGNIFICANCE•On denture borders :Mylohyoid area.

Instruct the patient to place the tip of his tongue into the upper and lower vestibules on the right and left side.The area to be molded is reheated and the patient and is instructed to swallow two or three times in rapid succession.The tongue movements raise the level of the floor of the mouth through contraction of the mylohyoid muscle.

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GENIOHYOID:

• Origin: From inferior genial tubercle (in the

midline of inner surface of mandible).

• Insertion: is into the hyoid bone.

• Action: depresses the mandible.

• Blood supply: is through lingual artery.

• Nerve supply: is by hypolossal nerve.

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GENIOHYOID

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ORBICULARIS ORIS:• It has two parts: intrinsic and extrinsic part.

• Intrinsic part is a very thin sheet and originates from superior and inferior incisivus from maxilla & mandible. It inserts into the angle of mouth.

•The extrinsic part is actually formed by elevator and depressor muscles of the lips and inserts into the angle of the mouth.

•The orbicularis oris functions is to compress the lips against the teeth and close the oral orifice

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ORBICULARIS ORIS

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CLINICAL SIGNIFICANCE•For mandibular impressions : On recording Labial flange and labial

frenum The lip is massaged from side to side to mold the compound to desired functional extension. In order to activate the mentalis muscle the patient is asked to pout or lick his lower lip.

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•For maxillary impressions in labial flange and labial frenum area.Manually mold the compound by externally moving the lip side to side, simultaneously applying finger pressure to control the width of the borderLift the patients upper lip and vertically place the frenum into the softened compound and mold with your fingers using a side to side external motion

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Orgin : It arises from the posterior and

lateral surface of the styloid process of the temporal bone.

Insertion : Is inserted into the body of the hyoid

bone, at its junction with the greater cornu, and just superior the omohyoid muscle.

Action : draws the hyoid bone upward, backward and elongates the floor of the mouth

STYLOHYOID

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STYLOHYOID

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•INFRAHYOID MUSCLES:

The origin and insertion of this group of muscles have no particular significance in complete denture prosthodontics insofar having any influence in denture borders.

The action of these muscles is important to the prosthodontist, for they are a part of kinetic chain of mandibular movement. Their action is to fix or depress the hyoid bone so that the suprahyoid muscles can act.

TEXTBOOK OF COMPLETE DENTURES – CHARLES M HEARTWELL

99SUMMARY OF THE ANATOMY AND

FUNCTION

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CHEWING•Two separate acts are recognized in the

chewing process.

•First is a combination of prehension and incision in which the food is secured by the lips and bitten by the front teeth.

•The second is mastication, the major activity during which the food is mashed between the back teeth.

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•The total chewing cycle occurs through three phases:

1. The opening stroke during which the mandible is lowered.

2. The beginning closing stroke during which the mandible is rapidly raised until the entrapped food is felt and

3. The power stroke in which the food is compressed, punctured, crushed and sheared.

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CHEWING MOVEMENTS AND MECHANICS

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•The chewing process generally acts as a 2nd order lever system resulting in compression at TMJ.

•The turning moment generated along mandibular body and ramus creates a sheer at Tempromandibular joint.

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• Chewing in humans is actually asymmetrical and unilateral.

• At the working side:

• It possesses the greatest adductor force, but articular emminence is less substantially loaded.

• At the balancing side:

• It possesses the less adductor force and the articular emminence is substantially loaded.

• At the initial action, contraction of inferior head of lateral pterygoid muscle occurs to initiate mandibular deviation to working side.

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MASTICATORY MUSCLE DISORDERS

•Some of the common masticatory muscle disorders involve:

•Congenital hyperplasia/ hypoplasia•Hypermobility/ hypomobility of the

muscle•Muscle pains•MPDS•Myositis ossificans etc.

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CONGENITAL HYPOPLASIA/ HYPERPLASIA

• It occurs very rarely, and is more common in masseter and orbicularis oris.

• Its oral symptoms include enlargement or decreased size of the affected muscle, which may show an asymmetric facial pattern and stiffness in the temporo-mandibular joint.

• It may or may not be associated with hypermobility/ hypomobility of the muscles.

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MUSCLE HYPERMOBILITY/ HYPOMOBILITY

•This disorder involves extreme or diminished activity of the masticatory muscles.

• Its etiology includes various factors such as:•Decreased/ increased threshold potential of

neural activity.•Parkinsonism•Facial paralysis•Nerve decompression•Secondary involvement of systemic diseases.

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MUSCLE PAINS• It usually occurs as a result of reflex protective

mechanism and myofacial triggers.

• It is usually felt as a non-pulsatile variable aching sensation, with a boring quality. It may also present with tightness, weakness, swelling or tenderness.

• It includes 3 types:1. local muscle soreness:it is a primary hyperalgesia with lowered pain threshold due to local factors such as stress, injury, infection etc.

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• This may be due to:1. distortion of blood vessels within the muscle or2. forceful or sustained contraction repeatedly.

2. Muscle splinting pain:it is defined as rigidity of the muscle occuring as a means of avoiding pain caused by movement of the part.

it is a reflex protective mechanism.

Splinting of masticatory muscle may occur as a protective mechanism in conditions such as toothache, overstressed teeth, effect of local anaesthetics, trauma etc.

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3. Non-spastic myofacial pains:There is no spasm and pain is the only complaint and this is generally referred to structures outside the muscle proper.

it may be due to atrophied muscle mass because of inactivity, illness or nutritional deficiency.

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ZONES OF REFFERED PAIN• The masseter muscle pain refers to the ear,

TMJ and the mandibular teeth.

• The temporalis refers to the temple, orbit and maxillary teeth.

• The medial pterygoid refers to the infra-auricular and post-mandibular area.

• The lateral pterygoid always refers its pain to the TMJ.

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MYOFACIAL PAIN DYSFUNCTION SYNDROME (MPDS)

•Muscular Disorders (Myofacial Pain Disorders) are the most common cause of TMJ pain associated with masticatory muscles.

•Common etiologies include:1. Many patient with “high stress level”2. Poor habits including gum chewing, bruxism, hard candy chewing3. Poor dentition

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•Its treatment includes 4 phases of therapy which includes muscle exercises and drugs involving NSAIDs and muscle relaxants.

•A bite appliance is also worn by the patient in the furthur stages to ‘splint’ the muscle movement.

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MYOSITIS OSSIFICANS

• It is a condition wherein fibrous tissue and heterotropic bone forms within the interstitial tissue of muscle, as well as in associated tendons or ligaments.

• It is of two types: localized and generalized.

A. Localized myositis ossificans:• It is caused by trauma or heavy muscular

strains or by metaplasia of pluripotential intermuscular cnnective tissue.

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•The affected site remains swollen and tender, and the overlying skin may be red and inflamed.

•There may present a difficulty in the opening of the mouth.

•management is done by giving sufficient rest to the muscle and excision of the involved muscle after the process has stopped.

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B. Generalized myositis ossificans:• In this, formation of bone in tendons and fascia

occurs alongwith subsequent replacement of muscle mass by the bony tissue.

•The masseter muscle is the most frequently involved.

• It usually occurs in children less than 6 years of age.

• It shows an evidence of dense osseous structures in the greater part or whole of the muscle.

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•There is a gradual increase in stiffness and limitation in the motion of masticatory muscles. Ultimately, the entire muscle may get transformed into bone resulting in no movement.

•Management: there is no specific treatment. The muscles involved are to be excised.

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CONCLUSION•The masticatory muscles include a vital part

of the orofacial structure and are important both functionally and structurally.

• It can be influenced by a variety of factors many of which are controlled by the practicing prosthodontist namely

During functional impression making Accurate recording of various clinical

parameters like vertical dimension, centric relation

Morphology of artificial tooth Maintenance of arch form

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•The proper management and periodical self- examination of the muscles may provide a greater chance of catching the disease process at an early stage which may be useful for its better prognosis.

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REFERENCES•Human anatomy by B.D. Chaurasia, 3rd ed.•Human anatomy by dental students by

M.K.Anand, 1st ed.•Complete denture prosthodontics by John J

sharry.•Mastering the art of complete denture by

Alexander R Halperin.•Anatomy for dental students by D.R Johnson

and W.J Moore•Burkits oral medicine diagnosis & treatment

10th edition.•Textbook of Complete dentures by Charles

M Heartwell

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•Management of Tempromandibular disorders and occlusion by Jeffrey P Okeson 4 rth ed.

• Impressions for complete dentures by Bernard Levin.

• Jaw muscle activity in complete denture wearers by Antje Tallgren, Dr Odont. J Prosthet dent aug 1980 vol 44(2) 123-32

•Feasibility of palpating the lateral pterygoid by R Johnstone and Mc Cormick templeton J Prosthet Dent 1980 Vol 44(3) 318-321.

•An Electromyographic study of masticatory and lip muscle functions in patients with complete dentures by Bengt Ingervall, Dr Odont et al. J Prosthet Dent March 1980 Vol 43(3) 266-71

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