ANATOMY OF DENTURE BEARING AREA

ANATOMY OF DENTURE BEARING AREA

OSTEOLOGY The osseous structure not only support the denture but also have an direct bearing on impression making procedure. Maxillary denture is supported by two pairs of bones, maxillae & palatine bone. Mandibular denture is supported by one bone, the mandible.

MAXILLA There are two maxillae, each consisting of central body and four processes. Areas of the body two of the processes are involved in the support of maxillary denture. Anterolateral surface of the body of the maxilla forms the skeleton of the anterior part of the cheek and is termed the malar surface.

MAXILLARY CAST

1. Labial frenum 2. Labial vestibule 3. Buccal frenum 4
1.Labial frenum 2.Labial vestibule 3.Buccal frenum 4.Buccal vestibule 6.Crest of alveolar ridge 7.Maxillary tuberosity 8.Hamular notch 9.Hard palate 10.Fovea palatini 11.Mid-palatine raphe 12.Incisive papilla 13.Palatine rugae

The zygomatico-alveolar crest
:- -It starts at the tip of the zygomatic process and continues in an arc inferiorly and laterally in the direction of first molar. -This crest has been likened to the buccal shelf in the mandible as a stress bearing area.

Maxillary tuberosity :-
-It is the posterior convexity of the maxillary body. -The medial & lateral walls resist the horizontal and torquing forces which would move the denture base in lateral or palatal direction. -Therefore, max denture base should cover the tubercles and fill the hamular notches.

The square arch provides best form denture stability.

Alveolar process :- -It arises from lower surface of maxilla.
-It consists of two parallel plates of cortical bone, buccolingual or labiolingual,which unite behind the last molar tooth to firm the alveolar tubercle.

The palatine process :-
-It arises as horizontal plates from the body of maxilla,which unite in midline ,forming midpalatal suure -The horizontal palatine process of maxilla appear to resist resorption over a long period. -As the bone of the aleolar ridge resorb,pressure of the vertical forces is increased over the bone of the palate.

When this bone become prominent in mid palatal suture area,it becomes fulcrum point aroud which maxillary denture base will rotate. -This in results discomfort to the patient and damage to soft tissue covering.

The rugae area It consist of series of ridges in the anterior part of the hard palate It is made up of keratinized fibrous connective tissue It is the secondary stress bearing area because it resist the forward movement of denture

The mid palatine raphe It is present as a raised bony ridge along the midline of hard palate The mucousa is thin and non resilent It act as fulcrum point so relieved

Nasopalatine or incisal foramen:-
-Is located in the midline of the palateposterior to the maxillary central incisors. -Nasopalatine nerves and blood vessels make their exit to the palate at right angles to margins of the bony foramen. -Denture base should be relieved over the areato avoid pressure to the nerves & blood vessels.

palatine fovea The fovea palatine are indentation near he midline of the palated form by the coalescence of several mucous glands duct They are closed to the vibrating line and always in the soft palate and, an ideal guide for the location of posterior border of denture

Vibrating line Vibrating line is an imaginary line across the palate that mark the beginning of moation of soft palate , when the pt. say ‘ahh’ it extent from one pterygo-maxilary notch other at the midline it usually passes about 2mm in fornt of fovea palatine

The direction of the vibrating line usually waries with the shape of palate , the higher the wault the more abrupt and forward the vibrating line In mouth with flat wault the vibrating line is usually farther posterior and has a gradual curvature The distal ends of the upper denture must extent at least to the vibrating line

in most instence the denture should end 1 to 2 mm posterior to the vibrating line
when the anterior teeth are to be placed well anterior to the residual ridge it may be possible to extent the denture posteriorly provided the pt can tolerate

Labial frenum Labia frenum
The labial frenum is a fold of mucous membrane at the midline It starts superiorly as fan shape and converges as it descend to its terminal end attachment on the labial side of ridge It is a relief area

Buccal frenum It is a single fold of mm sometime double and sometimes broad and fan shaped The caninus attaches beneath and affects its position The orbiculeris oris pulls the frenum forward and buccinator pulls backward Inadequate relief or thick flange can cause dislodgement of denture when cheeks are moved posteriorly

Buccal vestibule It extends from buccal frenum to hamular notch
It size varies with contraction of buccinator ,position of mandible ,amount of bone lost from maxilla It is a peripheral seal area

MAXILLARY CAST

Palatine bone The horizontal plates of the palatine bone articulates with the posterior rough border of horizontal palatal process of maxilla. The posterior border of horizontal plates of the palatine bone unite at midline to form a sharp line,the posterior nasal spine. The posterior margins of hard palate serve as the anteior attachment for the aponeurosis of the soft palate.

The posterior palatal seal should follow the contour of the posterior border of the hard palate,this would extend from hamular notch to hamular notch but not in straight line. The major or anterior palatine foramen is located medial to 3rd molarat the junction of the maxilla and the horizontal plates of the palatine bone.

The bone is notched and the palatine groove extends anteriorly.
The nerves and blood vessels are housed in the groove so rarely a relief is required in the denture base over the area.

Pterygoid hamulus Pterygoid hamulus does not support a maxillary denture,its position is in the osseous limit of the maxillary denture base posterior to the alveolar tubercle. The pterygoid hamulus is a thin curve process at the terminal end of the medial plates of sphenoid bone. A hamular notch is present between the pterygoid hamulus and alveolar tubercle.

MANDIBLE The body of mandible is horse shoe shaped and carries the alveolar process. The distal portion of each side continues upward and backward into the mandibular ramus. The ramus divides superiorly into the two processes,posteriorly the condyloid and anteriorly the coronal process.

The condyle is the articulating surface of the condyloid process.
The connection of the condyle with the ramus is slightly constricted called as manibular neck. The coronoid process is the triangular bony plate ending in a sharp corner,the convex anterior border continues in to the anterior border of the ramus.

When the mandible is protruded the anterior border of ramus extends towards the alveolar tuberosity.
If disto-lingual flange of the maxillary denture overfills the vestibule,it causes discomfort when the mandible is protruded. The denture could be dislodged when mandible in protrution is moved into right or left position.

MANDIBULAR ANATOMIC LANDMARKS

EXTERNAL OBLIQUE RIDGE
The external oblique line is the ridge of dense bone,extending from just above mental foramen,posteriorly and distally becoming continuous with the anterior border of ramus. The external oblique ridge is an anatomic guide for the lateral terminaion of the madibular denture.

Buccal shelf area The buccal shelf area is bounded externally by the external oblique line and internally by the slope of the residual ridge. The bone is very dense and the resultant forces of the elevator muscles directed in this area are best resisted. Buccal shelf area is a primary stress bearing area due to its density mucosal covering and its relation to the vertical closure of the jaw are favourable to best resist the forces.

mental foramen mylohyoid ridge
The mental foramen located on the lateral surface of the mandible between the 1st and 2nd bicuspid If the loss of the residual ridge is extensive,the foramen occupies superior position and the denture base should be relieved over the area. The mylohyoid line is an irregular rough bony crest extending from the 3rd molar to the lower border of mandible in the region of chin.

The irregularity of the crest often presents a problem to the denture.
The lingual flange of the mandibular denture should extend inferior but not lateral to mylohyoid line. if bony crest is so prominent and sharp it becomes the fulcrum point,surgical intervention is indicated.

The lingual tuberosity is an irregular area of bony prominance at the distal termination of the mylohyoid line. When this area s excessively prominent or rough, it may present an undesirable undercut area so sugically removed or rounded. The genial tubercles or mental spines are situated on the lingual aspect of the mandibular body in the midline.

When the loss of residual ridge is extensive,the spines are sometimes superior in position than crest of ridge so surgical procedure is implicated.

Crest of ridge The crest of the residual alveolar ridge is covered by favourable connective tissue but the underlying bone is cancellous so consider as secondary stress bearing area

Labial frenum and buccal frenum
It is band of fibrous connective tissue that help attach the orbicularis oris It is a relief area The part of denture that extends between labial and buccal frenum is called labial flange The buccal frenum is a continous band of through the modiolus at the corner of the mouth to the buccal frenum in maxilla

It is a relief area The tone of skin of lip and of orbicularis oris depends on thickness of flange and position of teeth Buccal vestibule It extends from buccal frenum posteriorly to the outside back corner of the retro molar pad and from crest of residual ridge to the cheek.

Muscles Masticatory Muscles MASSETER TEMPORALIS MEDIAL PTERYGOID
LATERAL PTERYGOID

Masseter It consists of three layers which blend anteriorly.
The superficial layer is the largest. It arises by a thick aponeurosis from the maxillary process of the zygomatic bone and from the anterior two-thirds of the inferior border of the zygomatic arch. Its fibres pass downwards and backwards, to insert into the angle and lower posterior half of the lateral surface of the mandibular ramus.

Masseter Intramuscular tendinous septa in this layer are responsible for the ridges on the surface of the ramus. The middle layer of masseter arises from the medial aspect of the anterior two-thirds of the zygomatic arch and from the lower border of the posterior third of this arch. It inserts into the central part of the ramus of the mandible.

Masseter The deep layer arises from the deep surface of the zygomatic arch and inserts into the upper part of the mandibular ramus and into its coronoid process. There is still debate as to whether fibres of masseter are attached to the anterolateral part of the articular disc of the temporomandibular joint.

Masseter Relations Skin, platysma, risorius, zygomaticus major, the parotid gland and duct, branches of the facial nerve and the transverse facial branches of the superficial temporal vessels are all superficial relations. Temporalis and the ramus of the mandible lie deep to masseter.

Masseter Relations The anterior margin of masseter is separated from buccinator and the buccal branch of the mandibular nerve by a buccal pad of fat and crossed by the facial vein. The posterior margin of the muscle is overlapped by the parotid gland. The masseteric nerve and artery reach the deep surface of masseter by passing over the mandibular incisure (mandibular notch).

Masseter Vascular supply
Masseter is supplied by the masseteric branch of the maxillary artery, the facial artery and the transverse facial branch of the superficial temporal artery. Innervation Masseter is supplied by the masseteric branch of the anterior trunk of the mandibular nerve.

Masseter Actions Masseter elevates the mandible to occlude the teeth in mastication and has a small effect in side-to-side movements, protraction and retraction. Its electrical activity in the resting position of the mandible is minimal.

TEMPORALIS Temporalis arises from the whole of the temporal fossa up to the inferior temporal line - except the part formed by the zygomatic bone - and from the deep surface of the temporal fascia. Its fibres converge and descend into a tendon which passes through the gap between the zygomatic arch and the side of the skull.

The muscle is attached to the medial surface, apex, anterior and posterior borders of the coronoid process and to the anterior border of the mandibular ramus almost up to the third molar tooth. The anterior fibres of temporalis are orientated vertically, the most posterior fibres almost horizontally, and the intervening fibres with intermediate degrees of obliquity, in the manner of a fan. Fibres of temporalis may occasionally gain attachment to the articular disc.

Temporalis Relations:-
Body Skin, auriculares anterior and superior, temporal fascia, superficial temporal vessels, the auriculotemporal nerve, temporal branches of the facial nerve, the zygomaticotemporal nerve, the epicranial aponeurosis, the zygomatic arch and the masseter muscle are all superficial relations.

Temporalis Posterior relations of temporalis are the temporal fossa above and the major components of the infratemporal fossa below. Behind the tendon of the muscle, the masseteric nerve and vessels traverse the mandibular notch. The anterior border is separated from the zygomatic bone by a mass of fat

Temporalis Vascular supply:-
Temporalis is supplied by the deep temporal branches from the second part of the maxillary artery. The anterior deep temporal artery supplies c.20% of the muscle anteriorly, the posterior deep temporal supplies c.40% of the muscle in the posterior region and the middle temporal artery supplies c.40% of the muscle in its mid-region.

Temporalis Body Innervation :-
Temporalis is supplied by the deep temporal branches of the anterior trunk of the mandibular nerve.

Temporalis Actions:- Temporalis elevates the mandible and so closes the mouth and approximates the teeth. This movement requires both the upward pull of the anterior fibres and the backward pull of the posterior fibres, because the head of the mandibular condyle rests on the articular eminence when the mouth is open. The muscle also contributes to side-to-side grinding movements. The posterior fibres retract the mandible after it has been protruded.

Lateral pterygoid Lateral pterygoid :-
is a short, thick muscle consisting of two parts.--The upper head arises from the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone. The lower head arises from the lateral surface of the lateral pterygoid plate.

Lateral pterygoid Vascular supply
Lateral pterygoid is supplied by pterygoid branches from the maxillary artery which are given off as the artery crosses the muscle and from the ascending palatine branch of the facial artery.

Lateral pterygoid Innervation
The nerves to lateral pterygoid (one for each head) arise from the anterior trunk of the mandibular nerve, deep to the muscle. The upper head and the lateral part of the lower head receive their innervation from a branch given off from the buccal nerve. However, the medial part of the lower head has a branch arising directly from the anterior trunk of the mandibular nerve.

Lateral pterygoid Insertion
From the two origins, the fibres converge, and pass backwards and laterally, to be inserted into a depression on the front of the neck of the mandible (the pterygoid fovea). A part of the upper head may be attached to the capsule of the temporomandibular joint and to the anterior and medial borders of its articular disc.

Lateral pterygoid Actions :-
When left and right muscles contract together the condyle is pulled forward and slightly downward. This protrusive movement alone has little or no function except to assist opening the jaw.

Lateral pterygoid If only one lateral pterygoid contracts, the jaw rotates about a vertical axis passing roughly through the opposite condyle and is pulled medially toward the opposite side. This contraction together with that of the adjacent medial pterygoid (both attached to the lateral pterygoid plate) provides most of the strong medially directed component of the force used when grinding food between teeth of the same side.

Lateral pterygoid It is arguably the most important function of the inferior head of lateral pterygoid. It is often stated that the upper head is used to pull the articular disc forward when the jaw is opene

Lateral pterygoid This contraction together with that of the adjacent medial pterygoid (both attached to the lateral pterygoid plate) provides most of the strong medially directed component of the force used when grinding food between teeth of the same side. It is arguably the most important function of the inferior head of lateral pterygoid. It is often stated that the upper head is used to pull the articular disc forward when the jaw is opened. Most of the power of a clenching force is due to contractions of masseter and temporalis. The associated backward pull of temporalis is greater than the associated forward pull of (superficial) masseter, and so their combined jaw closing action potentially pulls the condyle backward. This is prevented by the simultaneous

Medial Pterygoid Medial pterygoid :-
is a thick, quadrilateral muscle with two heads of origin. The major component is the deep head which arises from the medial surface of the lateral pterygoid plate of the sphenoid bone and is therefore deep to the lower head of lateral pterygoid.

Medial Pterygoid The small, superficial head arises from the maxillary tuberosity and the pyramidal process of the palatine bone, and therefore lies on the lower head of lateral pterygoid.

Medial Pterygoid Insertion The fibres of medial pterygoid descend posterolaterally and are attached by a strong tendinous lamina to the posteroinferior part of the medial surface of the ramus and angle of the mandible, as high as the mandibular foramen and almost as far forwards as the mylohyoid groove. This area of attachment is often ridged.

Medial Pterygoid Relations
The lateral surface of medial pterygoid is related to the mandibular ramus, from which it is separated above its insertion by lateral pterygoid, the sphenomandibular ligament, the maxillary artery, the inferior alveolar vessels and nerve, the lingual nerve and a process of the parotid gland. The medial surface is related to tensor veli palatini and is separated from the superior pharyngeal constrictor by styloglossus and stylopharyngeus and by some areolar tissue.

Medial Pterygoid Vascular supply
Medial pterygoid derives its main arterial supply from the pterygoid branches of the maxillary artery. Innervation Medial pterygoid is innervated by the medial pterygoid branch of the mandibular nerve.

Medial Pterygoid Actions
The medial pterygoid muscles assist in elevating the mandible. Acting with the lateral pterygoids they protrude it. When the medial and lateral pterygoids of one side act together, the corresponding side of the mandible is rotated forwards and to the opposite side, with the opposite mandibular head as a vertical axis. Alternating activity in the left and right sets of muscles produces side-to-side movements, which are used to triturate food.

Medial Pterygoid Pterygospinous ligament .The pterygospinous ligament, which is occasionally replaced by muscle fibres, stretches between the spine of the sphenoid bone and the posterior border of the lateral pterygoid plate near its upper end. It is sometimes ossified, and then completes a foramen which transmits the branches of the mandibular nerve to temporalis, masseter and lateral pterygoid

Muscle of pharynx SUPERIOR CONSTRICTOR
The superior constrictor is a quadrilateral sheet of muscle and is thinner than the other two constrictors. It is attached anteriorly to the pterygoid hamulus (and sometimes to the adjoining posterior margin of the medial pterygoid plate), the posterior border of the pterygomandibular raphe, the posterior end of the mylohyoid line of the mandible, and, by a few fibres, to the side of the tongue. The fibres curve back into a median pharyngeal raphe which is attached superiorly to the pharyngeal tubercle on the basilar part of the occipital bone

SUPERIOR CONSTRICTOR The fibres curve back into a median pharyngeal raphe which is attached superiorly to the pharyngeal tubercle on the basilar part of the occipital bone

SUPERIOR CONSTRICTOR Relations
The upper border of the superior constrictor is separated from the cranial base by a crescentic interval which contains levator veli palatini, the pharyngotympanic tube and an upward projection of pharyngobasilar fascia. The lower border is separated from the middle constrictor by stylopharyngeus and the glossopharyngeal nerve

SUPERIOR CONSTRICTOR Relations
Anteriorly the pterygomandibular raphe separates the superior constrictor from buccinator, and posteriorly the superior constrictor lies on the prevertebral muscles and fascia, from which it is separated by the retropharyngeal space. The ascending pharyngeal artery, pharyngeal venous plexus, glossopharyngeal and lingual nerves, styloglossus, middle constrictor, medial pterygoid, stylopharyngeus, and the stylohyoid ligament all lie laterally, and palatopharyngeus, the tonsillar capsule and the pharyngobasilar fascia lie internally.

SUPERIOR CONSTRICTOR Vascular supply.
The arterial supply of the superior constrictor is derived mainly from the pharyngeal branch of the ascending pharyngeal artery and the tonsillar branch of the facial artery. Innervation. The superior constrictor is innervated by the cranial part of the accessory nerve from the pharyngeal plexus.

SUPERIOR CONSTRICTOR Actions
The superior constrictor constricts the upper part of the pharynx.

MUSCLES OF THE TONGUE The tongue is divided by a median fibrous septum, attached to the body of the hyoid bone. There are extrinsic and intrinsic muscles in each half, the former extending outside the tongue and moving it bodily, the latter wholly within it and altering its shape.

MUSCLES OF THE TONGUE The extrinsic musculature consists of four pairs of muscles namely genioglossus, hyoglossus, styloglossus (and chondroglossus) and palatoglossus. The intrinsic muscles are the bilateral superior and inferior longitudinal, the transverse and the vertical.

MUSCLES OF THE TONGUE Genioglossus
Genioglossus is triangular in sagittal section, lying near and parallel to the midline. It arises from a short tendon attached to the superior genial tubercle behind the mandibular symphysis, above the origin of geniohyoid. From this point it fans out backwards and upwards. The inferior fibres of genioglossus are attached by a thin aponeurosis to the upper anterior surface of the hyoid body near the midline (a few fasciculi passing between hyoglossus and chondroglossus to blend with the middle constrictor of the pharynx).

Genioglossus Intermediate fibres pass backwards into the posterior part of the tongue, and superior fibres ascend forwards to enter the whole length of the ventral surface of the tongue from root to apex, intermingling with the intrinsic muscles. The muscles of opposite sides are separated posteriorly by the lingual septum.

Genioglossus Vascular supply
Genioglossus is supplied by the sublingual branch of the lingual artery and the submental branch of the facial artery. Innervation Genioglossus is innervated by the hypoglossal nerve.

Genioglossus Actions Genioglossus brings about the forward traction of the tongue to protrude its apex from the mouth. Acting bilaterally, the two muscles depress the central part of the tongue, making it concave from side to side. Acting unilaterally, the tongue diverges to the opposite side

MUSCLES OF THE TONGUE Hyoglossus (
Hyoglossus is thin and quadrilateral, and arises from the whole length of the greater cornu and the front of the body of the hyoid bone. It passes vertically up to enter the side of the tongue between styloglossus laterally and the inferior longitudinal muscle medially. Fibres arising from the body of the hyoid overlap those from the greater cornu.

Hyoglossus Relation Hyoglossus is related at its superficial surface to the digastric tendon, stylohyoid, styloglossus and mylohyoid, the lingual nerve and submandibular ganglion, the sublingual gland, the deep part of the submandibular gland and duct, the hypoglossal nerve and the deep lingual vein. By its deep surface it is related to the stylohyoid ligament, genioglossus, the middle constrictor and the inferior longitudinal muscle of the tongue, and the glossopharyngeal nerve.

Hyoglossus Posteroinferiorly it is separated from the middle constrictor by the lingual artery. This part of the muscle is in the lateral wall of the pharynx, below the palatine tonsil. Passing deep to the posterior border of hyoglossus are, in descending order: the glossopharyngeal nerve, stylohyoid ligament and lingual artery

Hyoglossus Vascular supply
Hyoglossus is supplied by the sublingual branch of the lingual artery and the submental branch of the facial artery. Innervation Hyoglossus is innervated by the hypoglossal nerve. Action Hyoglossus depresses the tongue.

MUSCLES OF THE TONGUE Styloglossus
Styloglossus is the shortest and smallest of the three styloid muscles. It arises from the anterolateral aspect of the styloid process near its apex, and from the styloid end of the stylomandibular ligament.

Styloglossus Passing downwards and forwards, it divides at the side of the tongue into a longitudinal part, which enters the tongue dorsolaterally to blend with the inferior longitudinal muscle in front of hyoglossus, and an oblique part, overlapping hyoglossus and decussating with it.

Styloglossus Vascular supply
Styloglossus is supplied by the sublingual branch of the lingual artery. Innervation Styloglossus is innervated by the hypoglossal nerve. Action Styloglossus draws the tongue up and backwards.

MUSCLES OF THE TONGUE Intrinsic muscles Superior longitudinal
The superior longitudinal muscle constitutes a thin stratum of oblique and longitudinal fibres lying beneath the mucosa of the dorsum of the tongue. It extends forwards from the submucous fibrous tissue near the epiglottis and from the median lingual septum to the lingual margins. Some fibres are inserted into the mucous membrane.

Intrinsic muscles Inferior longitudinal
The inferior longitudinal muscle is a narrow band of muscle close to the inferior lingual surface between genioglossus and hyoglossus. It extends from the root of the tongue to the apex. Some of its posterior fibres are connected to the body of the hyoid bone. Anteriorly it blends with styloglossus.

Intrinsic muscles Transverse
The transverse muscles pass laterally from the median fibrous septum to the submucous fibrous tissue at the lingual margin, blending with palatopharyngeus.

Intrinsic muscles Vertical
The vertical muscles extend from the dorsal to the ventral aspects of the tongue in the anterior borders

Intrinsic muscles Vascular supply
The intrinsic muscles are supplied by the lingual artery. Innervation All intrinsic lingual muscles are innervated by the hypoglossal nerve.

Intrinsic muscles The intrinsic muscles alter the shape of the tongue. Thus, contraction of the superior and inferior longitudinal muscles tend to shorten the tongue, but the former also turns the apex and sides upwards to make the dorsum concave, while the latter pulls the apex down to make the dorsum convex.

Intrinsic muscles The transverse muscle narrows and elongates the tongue while the vertical muscle makes it flatter and wider. Acting alone or in pairs and in endless combination, the intrinsic muscles give the tongue precise and highly varied mobility, important not only in alimentary function but also in speech.

SOFT PALATE SOFT PALATE
The soft palate is a mobile flap suspended from the posterior border of the hard palate, sloping down and back between the oral and nasal parts of the pharynx. The boundary between the hard and soft palate is readily palpable and may be distinguished by a change in colour, the soft palate being a darker red with a yellowish tint. The soft palate is a thick fold of mucosa enclosing an aponeurosis, muscular tissue, vessels, nerves, lymphoid tissue and mucous glands.

SOFT PALATE In most individuals two small pits, the fovea palatini, one on each side of the midline, may be seen: they represent the orifices of ducts from some of the minor mucous glands of the palate. The anterior third of the soft palate contains little muscle and consists mainly of the palatine aponeurosis. This region is less mobile and more horizontal than the rest of the soft palate and is the chief area acted upon by tensor veli palatini.

SOFT PALATE A small bony prominence, produced by the pterygoid hamulus, can be felt just behind and medial to each upper alveolar process, in the lateral part of the anterior region of the soft palate.

SOFT PALATE The pterygomandibular raphe –
a tendinous band between buccinator and the superior constrictor - passes downwards and outwards from the hamulus to the posterior end of the mylohyoid line. When the mouth is opened wide, this raphe raises a fold of mucosa that marks internally the posterior boundary of the cheek, and is an important landmark for an inferior alveolar nerve block.

SOFT PALATE Palatine aponeurosis
A thin, fibrous, palatine aponeurosis strengthens the soft palate, and is composed of the expanded tendons of the tensor veli palatini muscles. It is attached to the posterior border and inferior surface of the hard palate behind any palatine crests, and extends medially from behind the greater palatine foramina. .

SOFT PALATE It is thick in the anterior two-thirds of the soft palate but very thin further back. Near the midline it encloses the musculus uvulae. All the other palatine muscles are attached to the aponeurosis.

SOFT PALATE The lateral wall of the oropharynx presents two prominent folds, the pillars of the fauces. The anterior fold, or palatoglossal arch, runs from the soft palate to the side of the tongue and contains palatoglossus. The posterior fold, or palatopharyngeal arch, projects more medially and passes from the soft palate to merge with the lateral wall of the pharynx. It contains palatopharyngeus.

SOFT PALATE A triangular tonsillar fossa (tonsillar sinus) lies on each side of the oropharynx between the diverging palatopharyngeal and palatoglossal arches, and contains the palatine tonsil

HARD PALATE HARD PALATE
The hard palate is formed by the palatine processes of the maxillae and the horizontal plates of the palatine bones. The hard palate is bounded in front and at the sides by the tooth-bearing alveolus of the upper jaw and is continuous posteriorly with the soft palate. It is covered by a thick mucosa bound tightly to the underlying periosteum.

HARD PALATE In its more lateral regions it also possesses a submucosa containing the main neurovascular bundle. The mucosa is covered by keratinized stratified squamous epithelium which shows regional variations and may be ortho- or parakeratinized. The periphery of the hard palate consists of gingivae. A narrow ridge, the palatine raphe, devoid of submucosa, runs anteroposteriorly in the midline.

HARD PALATE An oval prominence, the incisive papilla, lies at the anterior extremity of the raphe and covers the incisive fossa at the oral opening of the incisive canal. It also marks the position of the fetal nasopalatine canal. Irregular transverse ridges or rugae, each containing a core of dense connective tissue, radiate outwards from the palatine raphe in the anterior half of the hard palate: their pattern is unique. .

HARD PALATE The submucosa in the posterior half of the hard palate contains minor salivary glands of the mucous type. These secrete through numerous small ducts, although bilaterally a larger duct collecting from many of these glands often opens at the paired palatine foveae. These depressions, sometimes a few millimetres deep, flank the midline raphe at the posterior border of the hard palate. They provide a useful landmark for the extent of an upper denture. The upper surface of the hard palate is the floor of the nasal cavity and is covered by ciliated respiratory epithelium

HARD PALATE

Facial Muscles Orbicularis oculi
Orbicularis oculi is a broad, flat, elliptical muscle which surrounds the circumference of the orbit and spreads into the adjacent regions of the eyelids, anterior temporal region, infraorbital cheek and superciliary region It has orbital, palpebral and lacrimal parts.

Orbicularis oculi The orbital part arises from the nasal component of the frontal bone, the frontal process of the maxilla and from the medial palpebral ligament. The fibres form complete ellipses, without interruption on the lateral side, where there is no bony attachment. The upper orbital fibres blend with the frontal part of occipitofrontalis and the corrugator supercilii.

Orbicularis oculi Many of them are inserted into the skin and subcutaneous tissue of the eyebrow, constituting depressor supercilii. Inferiorly and medially, the ellipses overlap or blend to some extent with adjacent muscles (levator labii superioris alaeque nasi, levator labii superioris and zygomaticus minor). At the extreme periphery, sectors of complete, and sometimes incomplete, ellipses have a loose areolar connection with the temporal extension of the epicranial aponeurosis.

Orbicularis oculi The palpebral part arises from the medial palpebral ligament, mainly from its superficial surface, and from the bone immediately above and below the ligament. The fibres sweep across the eyelids anterior to the orbital septum, interlacing at the lateral commissure to form the lateral palpebral raphe. A small group of fine fibres, close to the margin of each eyelid behind the eyelashes, constitutes the ciliary bundle.

Orbicularis oculi The lacrimal part arises from the upper part of the lacrimal crest, and the adjacent lateral surface, of the lacrimal bone. It passes laterally behind the nasolacrimal sac (where some fibres are inserted into the associated fascia), and divides into upper and lower slips. Some fibres are inserted into the tarsi of the eyelids close to the lacrimal canaliculi, but most continue across in front of the tarsi and interlace in the lateral palpebral raphe.

Orbicularis oculi Vascular supply
Orbicularis oculi is supplied by branches of the facial, superficial temporal, maxillary and ophthalmic arteries. Innervation Orbicularis oculi is supplied by temporal and zygomatic branches of the facial nerve.

Orbicularis oculi Actions
Contraction of the upper orbital fibres produces vertical furrowing above the bridge of the nose, narrowing of the palpebral fissure, and bunching and protrusion of the eyebrows, which reduces the amount of light entering the eyes. Eye closure is largely affected by lowering of the upper eyelid, but there is also considerable elevation of the lower eyelid.

Orbicularis oculi The palpebral portion can be contracted voluntarily, to close the lids gently as in sleep, or reflexly, to close the lids protectively in blinking. The palpebral part has upper depressor and lower elevator fascicles. The lacrimal part of the muscle draws the eyelids and the lacrimal papillae medially, exerting traction on the lacrimal fascia and may aid drainage of tears by dilating the lacrimal sac.

Orbicularis oculi It may also influence pressure gradients within the lacrimal gland and ducts. When the entire orbicularis oculi muscle contracts, the skin is thrown into folds which radiate from the lateral angle of the eyelids. Such folds, when permanent, cause wrinkles in middle age (the so-called 'crow's feet').

Buccinator Buccinator
The muscle of the cheek, buccinator, is a thin quadrilateral muscle which occupies the interval between the maxilla and the mandible. Its upper and lower boundaries are attached respectively to the outer surfaces of the alveolar processes of the maxilla and mandible opposite the molar teeth. Its posterior border is attached to the anterior margin of the pterygomandibular raphe. .

Buccinator In addition, a few fibres spring from a fine tendinous band that bridges the interval between the maxilla and the pterygoid hamulus, between the tuberosity of the maxilla and the upper end of the pterygomandibular raphe. The posterior part of buccinator is deeply placed, internal to the mandibular ramus and in the plane of the medial pterygoid plate. Its anterior component curves out behind the third molar tooth to lie in the submucosa of the cheek and lips.

Buccinator The fibres of buccinator converge towards the modiolus near the angle of the mouth. Here the central (pterygomandibular) fibres intersect, those from below crossing to the upper part of orbicularis oris, and those from above crossing to the lower part. The highest (maxillary) and lowest (mandibULar) fibres of buccinator continue forward to enter their corresponding lips without decussation. As buccinator courses through the cheek and modiolus substantial numbers of its fibres are diverted internally to attach to submucosa

Buccinator Relations Posteriorly, buccinator lies in the same plane as the superior pharyngeal constrictor, which arises from the posterior margin of the pterygomandibular raphe, and is covered there by the buccopharyngeal fascia. Superficially, the buccal pad of fat separates the posterior part of buccinator from the ramus of the mandible, masseter and part of temporalis. Anteriorly, the superficial surface of buccinator is related to zygomaticus major, risorius, levator and depressor anguli oris, and the parotid duct.

Buccinator It is crossed by the facial artery, facial vein and branches of the facial and buccal nerves. The deep surface of buccinator is related to the buccal glands and mucous membrane of the mouth. The parotid duct pierces buccinator opposite the third upper molar tooth, and lies on the deep surface of the muscle before opening into the mouth opposite the maxillary second molar tooth.

Buccinator Vascular supply
Buccinator is supplied by branches from the facial artery and the buccal branch of the maxillary artery. Innervation Buccinator is supplied by the buccal branch of the facial nerve.

Buccinator Actions Buccinator compresses the cheek against the teeth and gums during mastication, and assists the tongue in directing food between the teeth. As the mouth closes, the teeth glide over the buccolabial mucosa, which must be retracted progressively from their occlusal surfaces by buccinator and other submucosally attached muscles.

When the cheeks have been distended with air, the buccinators expel it between the lips, an activity important when playing wind instruments, accounting for the name of the muscle (Latin buccinator = trumpeter). when the massetor is activated is pushes the buccinator medialy against rhe denture in the area of he retromolar pad This is adislodging force and the dunture base should be contoured to accommodate the action

MENTALIS Mentalis Mentalis is a conical fasciculus lying at the side of the frenulum of the lower lip. The fibres arise from the incisive fossa of the mandible and descend to attach to the skin of the chin.

MENTALIS Vascular supply
Mentalis is supplied by the inferior labial branch of the facial artery and the mental branch of the maxillary artery. Innervation Mentalis is innervated by the mandibular branch of the facial nerve.

MENTALIS Actions Mentalis raises the lower lip, wrinkling the skin of the chin. Since it raises the base of the lower lip, it helps in protruding and everting the lower lip in drinking and also in expressing doubt or disdain. The contraction of this muscle is capable of dislodging a mandibular denture particularly when the residual ridge in anterior region is non-existent

LEVATOR ANGULI ORIS Levator anguli oris
Levator anguli oris arises from the canine fossa of the maxilla, just below the infraorbital foramen and inserts into and below the angle of the mouth. Its fibres mingle there with other muscle fibres (zygomaticus major, depressor anguli oris, orbicularis oris).

LEVATOR ANGULI ORIS Some superficial fibres curve anteriorly and attach to the dermal floor of the lower part of the nasolabial furrow. The infraorbital nerve and accompanying vessels enter the face via the infraorbital foramen between the origins of levator anguli oris and levator labii superioris. Vascular supply Levator anguli oris is supplied by the superior labial branch of the facial artery and the infraorbital branch of the maxillary artery.

LEVATOR ANGULI ORIS Innervation
Levator anguli oris is innervated by the zygomatic and buccal branches of the facial nerve. Actions Levator anguli oris raises the angle of the mouth in smiling, and contributes to the depth and contour of the nasolabial furrow.

ZYGOMATICUS MAJOR Zygomaticus major
Zygomaticus major arises from the zygomatic bone, just in front of the zygomaticotemporal suture, and passes to the angle of the mouth where it blends with the fibres of levator anguli oris, orbicularis oris and more deeply placed muscular bands. Vascular supply Zygomaticus major is supplied by the superior labial branch of the facial artery.

ZYGOMATICUS MAJOR Innervation
Zygomaticus major is innervated by the zygomatic and buccal branches of the facial nerve. Actions Zygomaticus major draws the angle of the mouth upwards and laterally as in laughing.

ZYGOMATICUS MINOR Zygomaticus minor
Zygomaticus minor arises from the lateral surface of the zygomatic bone immediately behind the zygomaticomaxillary suture, and passes downwards and medially into the muscular substance of the upper lip. Superiorly it is separated from levator labii superioris by a narrow triangular interval, and inferiorly it blends with this muscle.

ZYGOMATICUS MINOR Vascular supply
Zygomaticus minor is supplied by the superior labial branch of the facial artery. Innervation Zygomaticus minor is innervated by the zygomatic and buccal branches of the facial nerve.

ZYGOMATICUS MINOR Actions
Zygomaticus minor elevates the upper lip, exposing the maxillary teeth. It also assists in deepening and elevating the nasolabial furrow. Acting together, the main elevators of the lip - levator labii superioris alaequae nasi, levator labii superioris and zygomaticus minor - curl the upper lip in smiling, and in expressing smugness, contempt or disdain.

Depressor anguli oris Depressor anguli oris
Depressor anguli oris has a long, linear origin from the mental tubercle of the mandible and its continuation, the oblique line, below and lateral to depressor labii inferioris. It converges into a narrow fasciculus that blends at the angle of the mouth with orbicularis oris and risorius.

Depressor anguli oris Some fibres continue into the levator anguli oris muscle. Depressor anguli oris is continuous below with platysma and cervical fasciae. Some of its fibres may pass below the mental tubercle and cross the midline to interlace with their contralateral fellows; these constitute the transversus menti (the 'mental sling').

Depressor anguli oris Vascular supply
Depressor anguli oris is supplied by the inferior labial branch of the facial artery and the mental branch of the maxillary artery. Innervation Depressor anguli oris is innervated by the buccal and mandibular branches of the facial nerve.

Depressor anguli oris Actions
Depressor anguli oris draws the angle of the mouth downwards and laterally in opening the mouth and in expressing sadness. During opening of the mouth the mentolabial sulcus becomes more horizontal and its central part deeper.

Incisivus labii superioris
Incisivus labii superioris has a bony origin from the floor of the incisive fossa of the maxilla above the eminence of the lateral incisor tooth. Initially it lies deep to orbicularis oris pars peripheralis superior. Arching laterally, its fibre bundles become intercalated between, and parallel to, the orbicular bundles. Approaching the modiolus, it segregates into superficial and deep parts: the former blends partially with levator anguli oris and attaches to the body and apex of the modiolus and the latter is attached to the superior cornu and base of the modiolus.

Incisive labii inferioris
Incisivus labii inferioris, an accessory muscle of the orbicularis oris muscle complex, has many features in common with incisivus labii superioris. Its osseous attachment is to the floor of the incisive fossa of the mandible, lateral to mentalis and below the eminence of the lateral incisor tooth. Curving laterally and upwards, it blends to some extent with orbicularis oris pars peripheralis inferior before reaching the modiolus, where superficial bundles attach to the apex and body, and deep bundles attach to the base and inferior cornu.

The action of muscle of facial expression is responsible for the facial posture associated with the smiling laughing frowning or scrowling if the muscle of facial expression are not properly supported b y natural teeth or artificial subsitute none of the facial expression appear normal Incorrectly position teeth or incorrectly conture border base will destroy the normal tonacity of muscle

Platysma Platysma Platysma is described as a muscle of the neck but it is considered here as a contributor to the orbicularis oris muscle complex. The pars mandibularis attaches to the lower border of the body of the mandible. Posterior to this attachment, a substantial flattened bundle separates and passes superomedially to the lateral border of depressor anguli oris, where a few fibres join this muscle.

Platysma The remainder continue deep to depressor anguli oris and reappear at its medial border. Here they continue within the tissue of the lateral half of the lower lip, as a direct labial tractor, platysma pars labialis. Pars labialis occupies the interval between depressor anguli oris and depressor labii inferioris and is in the same plane as these muscles. The adjacent margins of all three muscles blend and they have similar labial attachments.

Platysma Platysma pars modiolaris constitutes all the remaining bundles posterior to pars labialis, other than a few fine fascicles that end directly in buccal dermis or submucosa. Pars modiolaris is posterolateral to depressor anguli oris and passes superomedially, deep to risorius, to apical and subapical modiolar attachments.

Saliva

suprahyoid MYLOHYOID Mylohyoid lies superior to the anterior belly of digastric and, with its contralateral fellow, forms a muscular floor for the oral cavity. It is a flat, triangular sheet attached to the whole length of the mylohyoid line of the mandible. The posterior fibres pass medially and slightly downwards to the front of the body of the hyoid bone near its lower border.

MYLOHYOID The middle and anterior fibres from each side decussate in a median fibrous raphe that stretches from the symphysis menti to the hyoid bone. The median raphe is sometimes absent, in which case the two muscles form a continuous sheet, or it may be fused with the anterior belly of digastric. In about one-third of subjects there is a hiatus in the muscle through which a process of the sublingual gland protrudes.

MYLOHYOID Relations The inferior (external) surface is related to platysma, anterior belly of digastric, the superficial part of the submandibular gland, the facial and submental vessels, and the mylohyoid vessels and nerve. The superior (internal) surface is related to geniohyoid, part of hyoglossus and styloglossus, the hypoglossal and lingual nerves, the submandibular ganglion, the sublingual gland, the deep part of the submandibular gland and its duct, the lingual and sublingual vessels and, posteriorly, the mucous membrane of the mouth.

MYLOHYOID Vascular supply
Mylohyoid receives its arterial supply from the sublingual branch of the lingual artery, the maxillary artery, via the mylohyoid branch of the inferior alveolar artery, and the submental branch of the facial artery. Innervation MYlohyoid is supplied by the mylohyoid branch of the inferior alveolar nerve.

MYLOHYOID Actions Mylohyoid elevates the floor of the mouth in the first stage o f deglutition It may also elevate the hyoid bone or depress the mandible.

GENIOHYOID GENIOHYOID
Geniohyoid is a narrow muscle which lies above the medial part of mylohyoid. It arises from the inferior mental spine (genial tubercle) on the back of the symphysis menti, and runs backwards and slightly downwards to attach to the anterior surface of the body of the hyoid bone. The paired muscles are contiguous and may occasionally fuse with each other or with genioglossus.

GENIOHYOID Vascular supply
The blood supply to geniohyoid is derived from the lingual artery (sublingual branch). Innervation Geniohyoid is supplied by the first cervical spinal nerve, through the hypoglossal nerve.

GENIOHYOID Actions Geniohyoid elevates the hyoid bone and draws it forwards, and therefore acts partly as an antagonist to stylohyoid. When the hyoid bone is fixed, geniohyoid depresses the mandible.

Omm Maxillary arch The mucous membrane is composed of two layer mucousa and submucous The mucousal covering of the gingiva and hard palate have common epitheliun that is thick and hornified The two areas may vary in their submocousa There is no well differentiated submucusa layer in the gingiva ,inellastic connective tissue of the lamina propria fuses with the periosteum the alveolar process

The mm covering the crest of alveolar ridge isfirmly attached to periosteum of bone
The stratified squamous epitheliun is thickly keratinizd The submucousa is devoid of fat or glandular cells The outer surface of bone is compact in nature

This compact nature with tightly attached mm makes the crest of ridge best able to provide primary support to denture As the mm moves along slope of ridge it tends to lose its firm attachment to bone and epithelium is non keratinized or slightly keratinized

There is distinct submucousal layer in the covering of palate
The mucous membrane is tightly attached to the periosteum of the maxillary and palatine bone The submucousa is divided into three spaces ,middle third of hard palate is filled with adipose tissue , posterior third contains glands

So tissues are recorded in resting condition because when they are displaced in final impression they tend to return their normal position form within the complete denture base creating soreness The submucosa is extremely thin in the region of mid palatine and mucosa is practically in contact with bone

So soft tissue covering mid palatine region is non resilient and relief is required in this area during final impression

In the fornix vestibule and the sublingual sulcus the mucous membrane is loosely and movably attached to the deep structure The mm has thin epithelium that is non keratinized These areas are easily displaced and act as excellent areas to create seal for the denture border

The submucosa in the region of vibrating line contains glandular tissue
The submucosa in hamular notcn region is thick and made up of areolar tissue Additional pressure can be placed on tissue in the centre of notch to create the peripheral seal

Mandibular arch The mm covering the crest of residual ridge is similar to that of maxillary ridge but underlying bone is cancellous in nature The mm covering the buccal shelf area is loosely attached and less keratinized and contains thick submucosal layer The bone is compact in nature

In the mandibular arch the distal end is well marked
After the loss of last molar ,the retromolar papilla remains attached to scar This area is firm ,and pale and easily distinguished from the retromolar pad, which is soft dark red and readily displaced

The mucosa is thin and non keratinized in retro molar region
The submucosa has loose aerolar tissue , glandular tissue , fibre of buccinator and superior constrictor, pteryomandibular raphe , tendon of temporalis

The mm lining the vestibular space and alveololingual sulcus is similar to lining of vestibular space of maxilla the epithelium is thin and non keratinized and submucosa is formed by loosely arranged connective tissue fibre mixed with elastic fibre

Hanau demonstration The making of impressions recording and verifying of jaw relations ,harmoning of occlusion of the teeth to coincide with the jaw movements are greatly influenced by the quality and quantity of soft tissues Hanau has demonstrated the mucosa supporting the denture bases is displaceable and compressible

Some of the finding are The tissue un the elderly take many hour to recover from the effect of moderate mechanical force where as youngs need only a short time for complete recovery The thicker the tissue the more is deformity The sex of the individual does not affect the result

Small forces can produce distinct compression of the tissue
Light load of long duration of time deform tissue more than heavy load of short duration When this knowledge is applied in complete denture prosthodontics , several factor appear pertinent

dentures particularly for pt
dentures particularly for pt. over 25 yr of age should be removed when making impression for new denture for sufficient time for tissue recovery this may be 24 hr for younger pt and several days for geriatric pt. a low viscosity impression material which will flow freely after the impression material is seated should be used, pressure is release after seating

3. Impression material should not be confined when making the refined impression, escaped holes should be provided 4. An impression should not be removed and inserted any more repeatedly than necessary 5. para-function habit produce light load for long duration , physiologic practices occur as heavy load short duration

6. It is responsibility of the dentist to recognize the problem and institute procedure to correct the source 7. Excessively thick mucosa should be evaluated for possible surgical reduction

The presence of fatty tissue provide a cushioned type of support ,so hard palate is primary stress bearing area The residual alveolar ridge is covered by tissue which in its structure is identical with attached gingiva It is a firm , thick layer of inelastic ,dense connective tissue ,immovabily attached to periosteum

The mucous membrane that comes in contact with the denture border is thin nonhornified epithelium and thin lamina propria The submucosal structure may be either tightly or loosely attached On the lips ,cheeks ,and under side of the tongue the lining mucosa is fixed to the epimysium or the fascia of the muscle

SALIVA Types of saliva Serrous (thin and watery)
Mucous (thick,lucid and adhesive) Mixed

Saliva is considered a major factor in evaluating the physical influences that contribute to denture retention The physical forces in which saliva is involved are: 1)Adhesion 2)Cohesion 3)Capillarity 4)Atmospheric pressure

Adhesion is the binding force exerted by the molecules of the unlike substances in contact.
Cohesion is that force by which molecules of the same body or same kind are held together. Capillarity is the form or surface tension between the molecules of a liquid and those of solid.

Increasing or reducing the surrounding pressure and temperature influences the retention of denture because the capillary forces affected.

Factors affecting the saliva
physiologic factors:- Agreeable taste stimuli result in profuse salivaton,distasteful stimulus result in temporary cessation. A smooth object inserted into the mouth increases salivation so denture surface should be smooth,a rough object inhibit salivation. When a person is dehydrated salivation decreases.

Pathologic conditions that decreases salivation are:-
Sennile atrophy of salivary gland. Radiation therapy of head and neck tumours. Diseases of brain stem that directly depresses salivary nucleous. Encephalitis,poliomyelitis. Diabetic mellitus.

Diarrhea caused by bacteria or food.
Elevated temperature. Vitamin deficiencies.

Pathologic conditions causing increased salivation:-
Digestive tract irritants. Painfull afflictions of oral cavity.

TMJ TEMPOROMANDIBULAR JOINT
None Each joint involves the articular fossa (also known as the mandibular fossa or glenoid fossa) above and the mandibular condyle below It is probably impossible to measure the pressure developed on the articular surfaces of the human jaw joint when biting. There is, however, irrefutable theoretical evidence based on Newtonian mechanics that the jaw joint is a weight-bearing jointThe non-working condyle is more loaded than the condyle on the working side, which may help explain why patients with a fractured condyle choose to bite on the side of the fracture abstract: FIBROUS CAPSULE The lower part of the joint is surrounded by tight fibres which attach the condyle of the mandible to the disc. The upper part of the joint is surrounded by loose fibres which attach the disc to the temporal bone . Thus the articular disc is attached separately to the temporal bone and to the mandibular condyle forming what could be considered two joint capsules. Longer fibres joining the condyle directly to the temporal bone may be regarded as reinforcing. The capsule is attached above to the anterior edge of the preglenoid plane, posteriorly to the lips of the squamotympanic fissure, between these to the edges of the articular fossa, and below to the periphery of the neck of the mandible. LIGAMENTS :Sphenomandibular ligament The sphenomandibular ligament is medial to, and normally separate from, the capsule. It is a flat, thin band that descends from the spine of the sphenoid and widens as it reaches the lingula of the mandibular foramen. Some fibres traverse the medial end of the petrotympanic fissure and attach to the anterior malleolar process. This part is a vestige of the dorsal end of Meckel's cartilageThe left temporomandibular joint. With the jaw closed, there is c.5 mm slack within the ligament, but it becomes taut when the jaw is about half open. Lateral pterygoid and the auriculotemporal nerve are lateral relations, the chorda tympani nerve lies medial near its upper end and medial pterygoid is an inferomedial relation. The sphenomandibular ligament is separated from the neck of the mandible below lateral pterygoid by the maxillary artery and from the ramus of the mandible by the inferior alveolar vessels and nerve and a parotid lobule. At this point the vessels and nerve to mylohyoid pierce the ligament. It is separated from the pharynx by fat and a pharyngeal vein. Stylomandibular ligament The stylomandibular ligament is a thickened band of deep cervical fascia that stretches from the apex and adjacent anterior aspect of the styloid process to the angle and posterior border of the mandible. Its position and orientation indicate that it cannot mechanically constrain any normal movements of the mandible and does not seem to warrant the status of a ligament of the joint. Body_ID: P Temporomandibular (lateral) ligament Body_ID: HC This broad ligament (Fig. 30.9) is attached above to the articular tubercle on the root of the zygomatic process of the temporal bone. It extends downwards and backwards at an angle of c.45° to the horizontal, to attach to the lateral surface and posterior border of the neck of the condyle, deep to the parotid gland. It appears to be poorly developed in the edentulous. A short, almost horizontal, band of collagen connects the articular tubercle in front to the lateral pole of the condyle behind. It may function to prevent posterior displacement of the resting condyle. Body_ID: P SYNOVIAL MEMBRANE Body_ID: HC The synovial membrane lines the inside of the capsule of the joint but does not extend to cover the disc or the articular surfaces. Body_ID: P ARTICULAR DISC Body_ID: HC Body_ID: P Body_ID: F Figure A sagittal section of the temporomandibular joint. The upper and lower joint spaces are normally compressed. They have been widened to illustrate the anteroposterior extent of each. The bilaminar posterior region contains a venous plexus. The transversely oval articular disc is composed predominantly of dense fibrous connective tissue (Fig ). It has a thick margin which forms a peripheral annulus and a central depression in its lower surface that accommodates the articular surface of the mandibular condyle. The depression probably develops as a mechanical response to pressure from the condyle as it rotates inside the annulus. The disc is stabilized on the condyle in three ways. Its edges are fused with the part of the capsular ligament that tightly surrounds the lower joint compartment and is attached around the neck of the condyle. Well-defined bands in the capsular ligament attach the disc to the medial and lateral poles of the condyle. The thick annulus prevents the disc sliding off the condyle, provided that the condyle and disc are firmly lodged against the articular fossa (as is normally the case). Body_ID: P In sagittal section, the disc appears to possess a thin intermediate zone and thickened anterior and posterior bands, and its upper surface appears concavo- convex where it fits against the convex articular eminence and the concavity of the articular fossa. Posteriorly the disc is attached to a region of loose vascular and nervous tissue which splits into two laminae, the bilaminar region: unlike the rest of the disc, its normal function is to provide attachment rather than intra- articular support. The upper lamina, composed of fibroelastic tissue, is attached to the squamotympanic fissure, and the lower lamina, composed of fibrous non-elastic tissue, is attached to the back of the condyle. The bilaminar region contains a venous plexus, but the central part of the disc is avascular. Body_ID: P The collagen is crimped, and this probably serves to absorb energy when a sudden tensile force is applied, and so briefly protects the disc from potential rupture. Cells in the disc also secrete chondroitin sulphate - a glycosaminoglycan found in cartilage - which is most heavily concentrated in the centre of the disc and which probably gives the disc some of the resilience and compressive strength of cartilage. The amount increases in response to load and to age, and by the fifth decade the disc shows signs of ageing including fraying, thinning and perforation. Body_ID: P Functions of the articular disc Body_ID: HC The functions of the articular disc remain controversial. It is generally believed that the disc helps to stabilize the temporomandibular joint. The articulating surfaces of the mandibular condyle and the articular fossa fit together poorly (Fig ) and are therefore separated by an irregular space. Muscle forces control the position of the mandible, and therefore of the condyle, in relation to the articular eminence, and these in turn set the shape and thickness of the irregular space. The position of the disc is controlled by neuromuscular forces: the upper head of lateral pterygoid anteriorly, and the elastic tissue in the bilaminar region posteriorly, together pull the disc backward or forward to keep the joint space filled and thereby stabilize the condyle. The articular disc may reduce wear, because the frictional wear on the condyle and the articular eminence is halved by separating slide and rotation into different joint compartments. It may also aid lubrication of the joint because it stores fluid that is squeezed out to create a weeping lubricant from the loaded part of the disc. Body_ID: P A final view is based on the fact that the addition of a slippery disc doubles the number of virtually friction free sliding surfaces suggesting that its function is to destabilize the condyle (certainly not stabilize it) in the same way that stepping on a banana skin destabilizes the foot. All other joints are most heavily loaded when their articular surfaces are closely fitted together, creating a large area of contact, and braced to prevent further movement. However the condyle of the mandible is most heavily loaded when it is required to move, sliding backward during the buccal phase of the power stroke of a masticatory cycle on the opposite side of the jaw. If the articular tissues were composed of hyaline cartilage, the small area of contact between poorly fitting surfaces would promote free sliding (Fig A) but simultaneously create a potentially damaging pressure (force per unit area). Making them of compressible fibrous tissue would reduce the pressure by increasing the surface area of contact and thereby spread the load, but the compressed tissues would interfere with free sliding movements (Fig B). The problem is overcome by fitting a disc between them (Fig C), which therefore destabilizes the condyle. In this context it is perhaps telling that the pathological absence of a disc, and not its presence, stabilizes the condyle during grinding movements and thereby renders the articular tissues vulnerable to damage. If these tissues respond by increasing their cartilaginous properties, the increased resistance to compression reduces the area of contact and results in damagingly large articular pressures. If they respond by becoming more fibrous the sliding condyle destructively gouges through the compressed fibrous tissue on the articular eminence. Body_ID: P Temporomandibular joint syndrome Body_ID:

forms most of the articular surface of the articular fossa.
Its steepness is variable, and it becomes flatter in the edentulous. Its anterior limit is the summit of the articular eminence, a transverse ridge that extends laterally out to the zygomatic arch as far as the articular tubercle.

Articular tissue extends anteriorly beyond the articular summit and on to the preglenoid plane.
Posteriorly it extends behind the depth of the fossa as far as the squamotympanic fissure. A postglenoid tubercle (at the root of the zygomatic arch, just anterior to the fissure) is usually poorly developed in human skulls.

The articular surface of the mandibular condyle is slightly curved and tilted forward at c.25° to the occlusal plane. Like the articular eminence, its slope is variable. In the coronal plane its shape varies (Osborn & Baranger 1992) from that of a gable (particularly marked in those whose diet is hard), to roughly horizontal in the edentulous.

The advantages and disadvantages of covering articular surfaces with cartilage
(A) and fibrous tissue (B). The addition of a fibrous disc (C) decreases the intra-articular pressure while simultaneously facilitating loaded sliding movements, unique requirements of the temporomandibular .. the precise aetiology posteriorly they drain into the

. Symptoms arising from the temporomandibular joints and their associated masticatory muscles are very common (temporomandibular joint syndrome/internal derangement). Diffuse facial pain due to masseteric muscle spasm, headache due to temporalis muscle spasm and jaw ache due to lateral pterygoid spasm are typical presenting symptoms.

.These may be associated with clicking, which is often audible whilst the patient is chewing, and sometimes locking, when the patient is unable to open fully. Changes in the normal structure of the articular disc occur and the disc does not smoothly follow the movements of the condyle.

There is, however, irrefutable theoretical evidence based on Newtonian mechanics that the jaw joint is a weight-bearing joint The non-working condyle is more loaded than the condyle on the working side, which may help explain why patients with a fractured condyle choose to bite on the side of the fracture abstract:

These symptoms affect predominantly adolescents and young adults and affect females more frequently than males. The symptoms occur particularly when the subject is under stress. Although predisposing factors have been implicated, such as the nature of the dental occlusion, the morphology of the head of the condyle, and variations in the attachments of lateral pterygoid,

of VASCULAR SUPPLY AND INNERVATION
The articular tissues and the dense part of the articular disc have no nerve supply. Branches of the auriculotemporal and masseteric nerves and postganglionic sympathetic nerves supply the tissues associated with the capsular ligament and the looser posterior bilaminar extension of the disc. The temporomandibular joint capsule, lateral ligament and retroarticular tissue contain mechanoreceptors and nociceptors. The input from mechanoreceptors provides a source of proprioceptive sensation that helps control mandibular posture and movement.

The joint derives its arterial supply from the superficial temporal artery laterally and the maxillary artery medially. Penetrating vessels that supply lateral pterygoid may also supply the condyle of the mandible. Veins drain the anterior aspect of the joint and associated tissues into the plexus surrounding lateral pterygoid, and

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ANATOMY OF DENTURE BEARING AREA

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