ABSTRACT Muscles of Facialexpressions play a vital role in nonverbal form of communication and projectingindividual’s personality. This articlepresents a brief overview for clinicians of muscles of facial expressions andtheir significance in prosthetic dentistry. INTRODUCTION The muscles of facial expression situatedin superficial fascia arise from the skull and are inserted into the skin. Many of these are named for action in Latin/Greek. They are salient form of nonverbal communication. Eyes are most obvious and immediatecues that lead to the formation of impressions.
Blink rate can reveal how nervous or at ease a person may be. They also act as sphincters or dialators oforifice of face. Movementselicited in test for Facial Nervefunction results from one or more motions or positions ofthe muscles of the face. Happiness or sadness, are expressed through asmile or a frown, respectively. Seven universally recognized emotions shownthrough facial expressions: fear, anger, surprise, contempt, disgust,happiness, and sadness. These play indispensable role in Prosthetic dentistry.
Awell-fitting and retentive complete denture requires a well-fitting tissuesurface, a peripheral border compatible with the muscles and tissues which makeup the mucobuccal and mucolabial spaces so that a peripheral seal is created bythe soft tissue draping over them. Thusthese muscles exert a direct and indirect influence upon the peripheralextensions, shape, and thickness of denture bases, the positions of teethhorizontally and vertically and facial appearance.DEVELOPMENT OF FACIAL MUSCLES Muscles offacial expressions are derived from the secondbrachial arch. It is known as hyoid arch or meckel’s cartilage.
Sometomeres six is responsible for thedevelopment of facial muscles. These areMesodermal in origin. NERVESUPPLY All muscles of Facialexpression are supplied by Facial nerve from 2nd Brachial Arch. Facialnerve courses through the petro uspart of the temporal bone through internal acoustic meatus with CN VIIIThanit passes Into facial canal, along walls of the tympanic cavity exits skull viastylomastoid foramen, most branches go through parotid gland anddivides intoTemporal, Zygomatic, Buccal, Cervical, Posterior auricular,Marginalmandibular. BLOODSUPPLY Muscles of Facialexpression are supplied by FacialArtery. It branch of External Carotid Artery.
Superior andInferior Labial Arteries supply Upper and Lower Lip. Angular artery supplies Nose. BRIEFOVERVIEW OF ALL MUSCLES OF FACIAL EXPRESSIONS FRONTALIS It is Thin, quadrilateral muscle intimatelyadherent to the superficialfascia.
It is Located on thefront of the head. It has no bony attachments. Medial fibers are continuous with thoseof the Procerus; itsimmediate fibers blend with the Corrugator and OrbicularisOculi and are attached to the skin of the eyebrows. The fibers are directed upward, and jointhe galea aponeurotica below the coronal suture.
Primary function is to lift eyebrows (thus opposing the orbital portion of the orbicularis), especially when lookingup. It acts when a view is too distantor dim. It is supplied by OphthalmicArtery and innervated by Facial Nerve.ORBICULARIS OCULI The Orbicularis Oculi Broad, flat,elliptical muscle arises from the nasal part of the frontal bone, from the frontalprocess of the maxilla in front of the lacrimal groove, and from the anteriorsurface and borders of a short fibrous band, the medial palpebral ligament. It has Palpebral, Orbitaland lacrimal parts. The palpebral portion ofthe muscle is thin and arises fromthe bifurcation of the medial palpebral ligament, forms a series of concentriccurves, and is inserted into the lateral palpebral raphe. The orbital portion Arises from the nasal component of the frontal bone.
Upperorbital fibers blend with the frontal part of occipitofrontalis and the Corrugator supercilii and Inserted intothe skin and subcutaneous tissue of the eyebrow. The lacrimal arises from the posterior part of the lacrimalcrest, and the adjacent orbital surface, of the lacrimal bone. It Passes laterally behind the nasolacrimal sac and divides into upper and lower slips. It is inserted into tarsi of eyelids. Orbital part causes vertical furrowing above thebridge of the nose, narrowing ofthe palpebral fissure and Protrusion ofthe eyebrows, which reduces the amount of light entering the eyes.
PALPEBRAL PART is contracted voluntarily, to close thelids gently as in sleep, or reflex to close the lids protectively in blinking. Lacrimal part aids in drainage of tears by dilating the lacrimal sac. When it contracts,the skin is thrown into folds which radiate from the lateral angle of the eyelids. Such folds, when permanent, causewrinkles in middle age (‘crow’s feet’). It is supplied by Branchesof the facial, superficial temporal, maxillary and ophthalmic arteries and Innervated by temporal and zygomaticbranches of the facial nerve.CORRUGATOR SUPERCILLI It is Small, narrow, Pyramidal muscle placedat the medial end of the eyebrow, beneath the Frontalis and just above Orbicularis Oculi and medial end of the superciliary arch. Itis inserted into the deepsurface of the skin, above the middle of the orbital arch. The Corrugator draws the eyebrowdownward and medial ward, producing the vertical wrinkles of the forehead.
Itis the “frowning” muscle, and may be regarded as the principal muscle in theexpression of suffering. Its vascular Supply is through ophthalmic artery and is innervated by Facialnerve.PROCERUS This is Small pyramidal slip like muscle. Itarises by tendinous fibers fromthe fascia covering the lower part of the nasal bone andupper part of the lateral nasal cartilage and is inserted into the skin over the lower part of the forehead betweenthe two eyebrows. Fibers merge withthose of the Frontalis. It pulls the skin between the eyebrowsdownwards, which assists in flaringthe nostril and contributes to an expression of anger. Also it drawsdown the medial angle ofthe eyebrow giving expressions of frowning.
Thismuscle is innervated by zygomatic branch of facial nerve.NASALIS MUSCLE It is Sphincter-like muscle divided into two parts, transverse and alar. Transverse part arisesfrom the maxilla, expanding into a thin aponeurosis and is continuous withopposite side muscle, and withthe aponeurosis of the Procerus.Alar part is attached at one end tothe greater alar cartilage,and integument at the point of the nose.It Compresses bridge, depressestip of nose, and elevates cornersof nostrils.Dilator naris muscle It is a part of the nasalis muscle. Dilator naris Posterior arises from the margin of the nasal notch of the maxilla, and fromthe lesser alar cartilage, andis Inserted into the skin nearthe margin of the nostrils. The Dilator naris anterior passes from the greater alar cartilage to the integument near the margin ofthe nostril.
DEPRESSOR SEPTI This muscle arises from the incisive fossa of the maxilla; its fibers ascend tobe inserted into theseptum and back part of the ala of the nose. It lies between the mucous membrane andmuscular structure of the lip. TheDepressor septi is a direct antagonist of the other muscles of the nose, drawingthe ala of the nose downward, and thereby constricting the aperture of thenares.muscles of the mouthBUCCINATOR It is thin quadrilateral muscle. It originsfrom the outer surfaces of the alveolar processes of the maxilla andmandible, corresponding to the three molar teeth; and behind, from the anteriorborder of the pterygomandibular raphe. The fibers converge toward the angle ofthe mouth, where the central fibers intersect each other, those from belowbeing continuous with the upper segment of the Orbicularis oris, and those fromabove with the lower segment; the upper and lower fibers are continued forwardinto the corresponding lip without decussation.
The Buccinators compress thecheeks, so that, during the process of mastication, the food is kept under theimmediate pressure of the teeth. When the cheeks have been previously distendedwith air, these muscles expel it from between the lips, as in blowing a trumpet.PROSTHODONTIC SIGNIFICANCE: Overextensions of a lower denture are commonin this region, either because the impression material is viscous enough toexcessively displace the soft tissues, or because the buccinator attachment ismore medially than expected.
Any suchoverextension will result in either displacement of the denture or pain. ORBICULARIS ORIS It is Ring-like muscle lies within theupper and lower lips. Contracts, it causes the lips to close. No true bony origin. It is Not simplesphincter muscle Consists of numerous strata of muscular fibers. It is partlyderived from the other facial muscles and partly of fibers proper to the lipsand is inserted at angle of mouth and lips.
It mainly functions in, bringing the lips together and also protruding them forward. ZYGOMATICUS MAJOR It arises from the zygomatic bone, in front of the zygomaticotemporalsuture and is inserted intothe angle of the mouth. This muscle Drawsthe angle of the mouth upwards and laterally as in laughing, raises the corners of the mouth. Dimples may becaused by its variations.ZYGOMATICUS MINIOR This muscle Arises from the lateralsurface of the zygomatic bone and passes downwards and medially into themuscular substance of the upper lip.
It elevates the upper lip; exposing themaxillary teeth also it assists in deepening and elevating the nasolabialfurrow. Like other elevators of the lip this muscle curls the upper lip insmiling, and in expressing smugness, contempt or disdain.LEVATOR LABII SUPERIORIS It extends from the side ofthe nose to the zygomatic bone and Inserted intothe greater alar cartilage and skin of the nose and other lateralpart of upper lip Lateral fibers, arise from the malar surface ofthe zygomatic bone and passes downward and medial ward. It elevates the Upper Lip.QUADRATUS LABII INFERIORIS It arises from the oblique line of themandible and Inserts on the skin of the lower lip, blending in withthe orbicularis oris muscle. Depressor labii is continuous with the fibersof the platysma muscle.
It helps todepress the lower lip. This muscleoriginates near to the crest of the ridge and extends down and below thealveololabial sulcus thus its contraction can reduce the denture space. In action it pulls the modioli forward andtenses the buccinator thereby applying pressure on the polished surface.LEVATOR ANGULI ORIS It arisesfrom the canine fossa of the maxilla and Inserts into and below the angle ofthe mouth. Its fibers mingle with zygomaticusmajor, depressor anguli oris, orbicularis oris fibers.
It contributes in formation of Angle of themouth during smiling and formation of the depth and contour of the nasolabialfurrow.DEPRESSOR ANGULI ORIS This is Long, linear muscle. It originsfrom the mental tubercle of the mandible. It is Narrow fasciculus and blends at the angle of the mouth with Orbicularisoris and Risorius. It Pass below the mental tubercle and cross the midline tointerlace with its contra lateral fellows. These constitute the transversusmenti (The ‘mental sling’).RISORIUS It arises in the fascia over parotid gland,passing horizontally forward and Inserts onto the skin at the angle of themouth.
It is a narrow bundle of fibers,broadest at its origin, but varies much in its size and form. Risorius retracts the angle of the mouth toproduce a smile, albeit an insincere-looking one. Also it has beensuggested that the risorius is only found in humans.MENTALIS It is conical fasciculus lying at the sideof the frenulum of the lower lip arising from the incisive fossa of themandible and Descending to attach to the skin of the chin. Mentalis raises thelower lip, causes wrinkling the skin of the chin and Protruding and evertingthe lower lip resulting in Expressing doubt or disdain.
It is sometimes referred to as the”POUTING MUSCLE Its Contraction capable of dislodging a mandibular dentureparticularly when the residual ridge in anterior region is non-existent. MODIOLUS The modiolus is a chiasma of facial muscles heldtogether by fibrous tissue, located lateral and slightly superior to each angleof the mouth. Contributedby the following muscles: orbicularis oris, buccinator, levatoranguli oris, depressor anguli oris, zygomaticus major, Risorius quadratuslabii superioris and quadratus labii inferioris. This Eight paired muscles ofexpression in combination with the single, orbicularis oris muscle controlmovements of the lips and cheeksAPPLIED ANATOMY Facialmuscles are dramatically affected bythe position of the artificial teeth Inadequate support makes people look olderwhile excessive support distorts a person’s features by making them lookstretched. Also they play an importantpart in forming the anterior and lateral portions of maxillary and mandibularimpression borders. This is because allof these muscles can alter the depth of vestibular sulci and unseat completedentures. In dentate patients, the lipsrely on 2 types of support: 1) Intrinsic support from muscles, fibrousconnective tissue, and glands; 2) Support from underlying structures such asthe anterior teeth and associated alveolar bone.
Proper position and functional length of themuscles that attach to the orbicularis oris include the zygomatic, quadratuslabii superior, caninus, Mentalis, quadratus labii inferior, triangularis,buccinator, and Risorius. Where there isno support for the lips and face due to missing teeth, border-molded flange tolift and support the face, and in doing so, counter gravity’s downward pull onaging skin. This is used toincrease the retention and stability of Dentures. SupportIncreases esthetics and make look younger. For Maxillary arch Orbicularis Oris anImportant Muscle. Its Tone depends onsupport received from Labial Flange and Position of Teeth Buccal Frenum is broadand Fan shaped which is pulled by Orbicularis Oris & buccinator Backwards.
It requiresclearance for its action. For MandibularArch anteriorly Flange area has to be thin, Orbicularis Oris is responsible fornarrowing the sulcus teeth arrangement should be in Neutral zone. The loss of support of these muscles,combined with laxity of subcutaneous connective tissue and fat atrophy, resultin an aging facial appearance. Deepeningof the nasolabial fold, a drooping of the corners of the mouth, and a loss ofvermilion border of the lips. There is adepression of the lips with exaggerated wrinkling. Occlusal wear and loss of vertical dimensionmake the chin more prominent, and the contours of the philtrum and mentolabialsulcus are altered. Appearance of lowerHalf of face depends on dentures. Tensed, wrinkle lips appear due to improperteeth arrangement.
Nasolabial Fold should not be obliterating duringarrangement. BELL’S PALSY is named by Sir Charles Bellin 1821Resulting from damage to VII cranial nerve. In Unilateral UMN contralaterallower 1/2-2/3 of face paralysed. InUnilateralLMN or CN VII: entire ipsilateral face paralysed. CLINICAL FEATURES are Weaknesson entire side of the face.
Inability toclose eye also Forehead doesn’t wrinkle. Such patients are Unable to lift theirmouth resulting in Dry mouth and impairment of taste. There is Difficulty witheating and drinking. Also Dry eyes are present and Tooth decay and gumdisease due to reduced saliva and impairment of chewing and affectedSpeech. Usually recovery is within fewmonths Ocular ointments, steroid medications to reduce inflammation, Antiviralmedications – such as acyclovir Analgesics or moist heat – to relieve pain or Botulinumtoxins to relax facial muscles can be prescribed. Prosthodontic managementrequires alteration in establishing Height of Occlusal plane & developing polished surfaceof Dentures.
Implantsare also good option for such patients.Botulinum toxin therapy is used to reduce the wrinkles. It is derivedfrom Bacterium Clostridium Botulinum Works to block the nerve impulses,temporarily paralyzing the muscle, action seen immediately, within 5-7 days, andit remains effective till six months.CONCLUSION Face is the tangible projector panels ofmechanisms that govern emotional and social Behaviors. Facial muscles not onlyhelp in expressing the emotions, but they do help in support of the dentures.
and Increase in Esthetics, after loss of natural teeth. Facial muscles are inwell toned and healthy, person’s face looks younger. Thus efficiency comfortand stability of artificial masticatory machine depends on its surroundingbiological environment.