Muscles of Facial Expression

Dr. Sriharsha VadapalliPG Student

Dept. of Prosthodontics

Over view

• Introduction• Classification• Individual muscles• Clinical significance.

INTRODUCTION

• The facial muscles are in the subcutaneous tissue of anterior and posterior scalp, face, and neck.

• Most muscles attach to bone on one side and soft tissue on another side, and produce their effects by pulling the skin.

• One of the greatest early workers in muscle physiology(1806-1875) is Duchenne, he wrote a book called physiology of motion in French. In 1949 E.B. KAPLAN translated it into English.

• Detailed and extensive studies on these muscles done by Huber(1931) and Lightoller(1925).

Primary functions:

• Regulate the size of the apertures.

• Expression of emotions.

• Articulation for speech.

• Embryology: All the muscles of facial expression develop from mesoderm and second pharyngeal arches.

• A subcutaneous muscular sheet forms during embryonic development, that spread over face and neck carrying branches of facial nerve with it to supply all the muscles formed from the arch.

• Because of common origin facial muscles are fused and their fibers are intermingled.

Nerve Supply:

Sensory nerve- Trigeminal nerve.

Motor nerve - Facial nerve. The branches are,

TemporalZygomaticBuccalMarginal mandibularcervical

Blood Supply: arterial supply: 1) Facial artery: this is the chief artery of face and arises from

external carotid artery. It divides into the following branches.

Superior labial Inferior labial

Lateral nasal2) Transverse facial artery, branch of superficial temporal

artery.3) Small arteries that accompany the cutaneous branches of

trigeminal nerve.4) Terminal part of supratrochlear and supra orbital arteries.

Venous supply:

1) Facial vein2) Retromandibular vein3) Supratrochlear vein.4) Supraorbital vein.5) Tributaries of superficial temporal vein.6) Tributaries of pterygoid plexus of veins.(Infraorbital, Buccal, and Mental veins)

Lymphatics:

• Preauricular lymph nodes.

• Submandibular lymph nodes.

• Submental lymph nodes.

Classification: Muscles of face can be broadly divided into (21)

Muscles of Scalp, Forehead, Eyebrows, Nose and opening of the Eye: (7) Occipito Frontalis, Procerus, Corrugator Supercilii, Levator Palpebrae Superioris, Orbicularis Occulii, Nasalis, Depressor Septii. Muscles of Mouth, Lips, and Cheeks: (14) These can be divided into Evertors, Elevators, Retractors of the upper lip (6)Levator Labii Superioris Alaque Nasii, Levator Labii Superioris, Levator angulii Oris, Zygomaticus major and minor. Incisivus Superioris. Depressors, Evertors, Retractors of the Lower LIP: (6)Depressor Angulii Oris, Depressor Labii Inferioris, Risorius, Platysma, Mentalis. Incisivus Inferioris. Orbicularis Oris. – Sphincter around mouth.Buccinator- cheek muscle.

• Occipito Frontalis. • Frontal belly: • Origin: Epicranial aponeurosis• Insertion: Skin and sub cutaneous tissue of eyebrows and fore

head.• Action: Elevates the eyebrows and wrinkles the skin of fore head,

protracts the scalp. • (Surprise and Curiosity)• • Occipital belly:• Origin: Lateral2/3rds of superior Nuchal line• Insertion: Epicranial Aponeurosis. • Action: Retracts Scalp; Increasing effectiveness of frontal belly.•

Corrugator Supercilii:

Origin: Medial end of Superciliary Arch. Insertion: Skin superior to mid supraorbital margin and superciliary arch. Action: Draws eye brows medially and inferiorly, creating vertical wrinkles above nose.(Demonstrating concern and worry)

3. Levator Palpebrae Superioris. Origin: Inferior surface lesser wing of sphenoid Insertion: - Medial margin attaches to Medial

Palpebral ligament. -Lateral margin attaches to whitnall’s

tubercle on zygomatic bone. -Central part inserts to skin of upper

eyelid, anterior surface of superior tarsus, Superior conjuctival fornix.Action: - Elevates the eyelids.

• 4..Procerus:• Origin: Fascia covering the nasal bone.• Insertion: Skin between Eyebrows• Action: Depresses medial end of eyebrow, acts

during Frowning

• 5.Nasalis:

Origin Anterior surface of maxilla near nasal notch

Insertion: into the alar cartilage and continues over the bridge of the nose with opposite muscle.

Action: - Compress the nasal aperture below the bridge of the nose.

-Alar part dilates the anterior nasal aperture.

• 6. Depressor Septii:• Origin: Incisive fossa on the anterior surface of the

maxilla.• Insertion: Nasal septum• Action: Dilatation of anterior nasal aperture

7. Orbicularis Occulii: it has 3 parts. Palpebral, Orbital, Lacrimal.Origin: Medial Palpebral ligament, adjoining frontal bone, and frontal process of maxilla, lacrimal fascia and crest of lacrimal bone.Insertion: subcutaneous tissue of eyebrow, Lateral Palpebral raphae.Action: it causes closure of eyelids both voluntarily or while blinking.-Aids in transport of lacrimal fluid by dilating lacrimal sac.

Injury to facial nerve, causes paralysis of facial muscles(Bells Palsy). Loss of muscle tone in Orbicularis Occulii causes inferior eyelid to Evert and fall away from eyeball. As a result lacrimal fluid does not spread on cornea preventing lubrication, hydration and causes flushing of surface of cornea. This results in corneal ulceration and impairment of vision.

Muscles of Mouth, Lips, and Cheeks: (12) Evertors, Elevators, Retractors of the upper lip (5): 8.Levator Labii Superioris Alaque Nasii:

Origin: Lateral surface of frontal process of maxilla.

Insertion: forms two thin slips which attach on –Ala of the nose,-Skin of upper lip.

Action: Elevates and Evert the upper lip and dilates the nostril.

9.Levator Labii Superioris:

Origin: Anterior surface of maxilla, close to infra orbital foramen.

Insertion: lateral surface of skin and subcutaneous tissue of upper lip.

Action: Elevates and Everts the upper lip.

10.Levator Anguli Oris: ( caninus)Origin: Below the infra orbital foramen, in the canine fossa of Maxilla.Insertion: Angle of the mouth.Action: Raises the angle of the mouth.

11.Zygomaticus Major:

Origin: Zygomatic Bone

Insertion: Angle of the mouth.

Action: Pulls the angle of the mouth upwards and laterally.

• Action of zygomatici muscles in elevating corners of the mouth for smiling produces nasolabial sulcus.

• Many older patients wants to have nasolabial sulcus obliterated because , it becomes a wrinkle as the skin loses resilience.

• The removal of nasolabial sulcus can be done by thickening of the denture base under the fold, but excess thickening gives an artificial look.

12.Zygomaticus Minor: Origin: Zygomatic BoneInsertion: Skin of upper lip in lateral part.Action: -Elevates and Everts the upper lip,-Increases Nasiolabial furrow.

Depressors, Evertors, Retractors of the Lower LIP: (5)

13.Depressor Angulii Oris:Origin: Posterior part of oblique line of mandible.

Insertion: Angle of Mouth.Action: Pulls the angle of the mouth downwards and laterally.

14.Depressor Labii Inferioris: Origin: Oblique line of Mandible.Insertion: Skin of Lower Lip.Action: Pulls the Lower lip downwards and laterally.

15.Risorius:

Origin: Parotid Fascia.

Insertion: Angle of the Mouth.

Action: Pulls angle of mouth downwards and laterally.

• 16.Mentalis: •

Origin: Incisive Fossa.•

Insertion: Skin of Chin.•

Action: Puckers the Chin.

• The origin of this muscle is above the level of lower fornix.

• Thus the shallow the lower vestibule, on contraction, This muscle is capable of dislodging lower denture, when the ridge in anterior region is the same height as the fornix of the vestibule.

• The level of attachment of this muscle to the alveolar ridge, dictates the extension of flange of the lower denture. Surgical repositioning of this muscle is sometimes advisable.

•

17.Platysma: Origin: Fascia over the anterior surface of deltoid and pectoralis major up to 2nd ribInsertion: Lower border of body of mandible, and few fibers to angle of mouth.Action: Depresses the mandible and pulls the angle of the mouth downwards and laterally.Its contraction mainly aids in venous return.

18.Buccinator:

• Main muscle of entire cheek.

• It is covered by Buccopharyngeal membrane.

• It is not a muscle of facial expression.

• It does not possess the facial-sheath.

• Origin: -outer surface of alveolar process of maxilla and mandible opposite the 3

molar teeth. -Pterygomandibular raphae • Insertion: Upper fibers insert into upper lip,

lower fibers insert into lower lip while intermediate fibers decussate to

upper and lower lips.• Action: - Flattens the cheek against the gums and

teeth, which helps during mastication. • -Helps in blowing out air through mouth.• - participates in deglutition.

• It runs from the corner of the mouth, and passing along the outer surface of maxilla and mandible, until it reaches the ramus, where it passes to the lingual surface to join superior constrictor of pharynx, and Pterygomandibular raphae.

Two Buccinator muscles and the Orbicularis oris forms a functional unit that depends on position of dental arches and labial contours of the mucosa or the denture base for effective action.

• In extreme cases of resorption of residual ridge, Mylohyoid and Buccinator cover the bone from 1st molar to retromolarpad.

• The action of this muscle does not dislodges the denture, because the fibers run parallel to plane of occlusion.

•

• But run perpendicular to masseter, when masseter is activated it pushes the Buccinator medially against denture in Retromolarpad area.

• This is a dislodging force, so denture base should be contoured to accommodate insertion between these two muscles.

• The contour in the denture base is termed as masseter groove.

• The position of the attachment of buccinator in upper jaw determines the vertical height of the distobuccal flange of upper denture.

• In senile individuals, patients with facial paralysis,

and individuals with reduced tone of Buccinator cheeks will collapse, and caught between the teeth.

19. Orbicularis Oris: • Origin: Extrinsic part: surrounds Facial muscles. Intrinsic part: Incisive fossa of maxilla and Mandible. • Insertion: fibers intermingle and surround the orifice of the mouth and attach to angle of the mouth and skin of lips.

• Action: -Closure of lips. -Compresses lip against gums and teeth which helps in mastication. -Protrusion of lips.

The muscles that merge into Orbicularis oris are the • Zygomaticus,• Quadrates Labii Superioris,• caninus or Levator angulii oris,• Mentalis,• Quadrates Labii Inferioris,• Triangularis or Depressor Anguli oris, • Buccinator and• Risorius.

• It is the muscle of the lips, it is sphincter like and attaching to the maxillae along a median line under the nose by means of a band of fibrous connective tissue known as maxillary labial frenum, and mandible on median plane by means of mandibular labial frenum.

• The marginal portion of muscle adjacent to the oral fissure acts less forcefully against the labial surface of the anterior teeth than does its peripheral portion. This permits more natural anterior position of the teeth, especially when labiolingual inclination keeps the neck of the tooth nearer the ridge.

• The superior border of lower lip is supported by

incisal third of upper anteriors, if not so, lower lip will be caught between anteriors during occlusion.

Three factors affect the face in repositioning the Orbicularis oris with complete dentures.

• Thickness of labial flanges of both the dentures.

• Anteroposterior position of anterior teeth

• Amount of separation between the mandible and maxilla.

• The upper lip is supported by the 6 upper anterior teeth. and lower lip is supported by labial surfaces of lower anteriors. And not by the denture flange.

• When teeth are in occlusion, the superior border of the lower lip is supported by the incisal third of the maxillary anterior teeth. So lower teeth should extend up to mentolabial sulcus

• If this were not so, the lower lip is caught between the U/l anterior teeth during occlusal contact.

• Angle of the mouth are easily irritated if the lips are stretched taught when impression tray is inserted

• If the jaws are closed too far, or dental arches are located too far posteriorly, the upward and backward positioning of the O.oris will cause movement of its merging muscles nearer to their origins.

• this causes sagging of merging muscles at rest. This causes dropping of the corners of the mouth. With a resultant senile edentulous expression, and causes atrophy of muscle fibers.

• If the mouth has been edentulous for a long time, with considerable resorption of ridges, the borders need to be thick to restore the position of the muscles.

• 20&21) Incisivus Labii Inferioris, and Superioris , • are small muscles , arises from the maxillary and

mandibular alveolar processes.• Then course laterally and blend with the orbicularis

oris muscle.

• It is doubtful that , contraction of these muscles alone will dislodge the dentures.

• However their presence beneath the mucous membrane might present problems associated with flange extension and denture retention.

Modiolus: (in Latin means hub of a wheel) .

• The bundle of tissues 1cm lateral to the corner of mouth called Modiolus or muscular node.

• It represents the origin, insertion or decussation of many fibers from various muscles of facial expression. The muscles form the Modiolus are:

• The Zygomaticus major.• Levator angulii oris.• Incisivus superious.• Buccinator.• Depressor angulii oris. • Incisivus inferiors.• Risorius• Orbicularis oris muscles

• This bundle is very active and act as a movable attachment to aid the Orbicularis oris and Buccinator muscles in their functions associated with mastication, speech, and deglutition.

• The other muscles listed above, act to stabilize this mass in various positions. This action tends to draw Modiolus medially, and hence exerts forces against teeth or denture flanges in the premolar area.

• Denture that is wide in premolar area will therefore tend to be displaced from its tissue seat.

• If thumb is placed inside the corner of the mouth,and finger on outside of the prominence, and then lip and cheeks are contracted, the modiolus feels like a knot.

• The modiolus becomes fixed every time the

buccinator muscle contracts, which is a natural accompaniment of all chewing efforts.

The contraction of modiolus presses the corner of the mouth against the premolars, so the occlusal table is closed in front.

• Food is crushed by the premolars and molars and does not escape the corner of the mouth. Unless seventh nerve damage has occurred.

• A good reminder of this observation is drooling that frequently occurs when a patient with an inferior nerve block attempts to drink.

•Clinical significance of facial muscles:

• Muscles of face do not insert into the bone and need support from the teeth for proper support.

• If these muscles are not properly supported, either by natural substitute or by artificial teeth, none of facial expressions appears normal.

• Lack of support allows sagging of muscles, stretching inhibits normal contraction of these muscles. They depend on the vertical dimension of the face, as determined by the occlusion of teeth in order that they may be neither stretched nor permitted to sag.

These factors affect the function, appearance of complete denture prosthesis, also to comfort of the patient.

•Forces exerted by these muscles against labial,buccal surfaces, and peripheral borders of dentures will obviously affect their dentures.

• Interplay of forces between tongue and cheek in placing and maintaining food on occlusal surfaces of teeth, that teeth should be placed in ideal position in neutral zone.

The memory pattern of facial expression developed within neuromuscular system when patient had natural teeth is continued or reinforced, when all these muscles are correctly supported by the complete dentures.

• Summary: The normal facial expression , and proper tone of the skin of the face depend on the position and function of the facial muscles.

• These muscles can function physiologically only when the dentist has positioned and shaped the dental arches correctly and has given the mandible a favorable vertical position.

• In addition dentures themselves must have a pleasing and natural appearance in patients mouth, A condition that is dependent on arranging the artificial teeth in a plan that simulates the nature.

Paralysis of buccinator and orbicularis oris accumulates the food in oral vestibule during chewing, and requires continuous removal of food with help of finger. Saliva dribble out through lips and patient will have a sad look when face is relaxed.

Expression Changes in skin of face Muscles involved

Surprise -Transverse wrinkles of forehead-Transverse wrinkles at bridge of nose

-Frontalis-Procerus

Frowning -Vertical wrinkles of fore head -Corrugator Supercilii

Anger -dilatation of anterior nasal aperture-Depression of lower part of nasal septum.

-Dilator naris-Depressor Septii

Laughing, Smiling -Angle of mouth is drawn upwards and laterally.

Zygomaticus major

Sadness Angle of the mouth drawn downwards and laterally

Depressor angulii Oris

Sorrow and grief Accentuation of Nasiolabial furrow with elevation and eversion of upper lip

-Levator Labii Superioris-Levator Anguli Oris

Grinning Retraction of angle of mouth Risorius

Disdain/Doubt Puckering of skin over chin with protrusion of lower lip

Mentalis

Whistling Pressing the cheek against gum with pursing of mouth with small opening

Buccinator

Facial expressions and concerned muscles:

Summary

• All the muscles of facial expression are developed from single bronchial arch, thus they share single nerve and blood supply.

• Each muscle has got its own importance.• Knowing the prosthodontic significance of

these muscles help us in daily practice.

Bibliography:• B.D. Chaurasia’s human anatomy 3rd edition.• Essentials of complete denture Prosthodontics

Sheldon Winkler ,Second Edition.• Complete denture Prosthodontics, John .J. sharry,

third edition.• Text book of complete denture, Rahn, fifth Edition.• Prosthodontic treatment for edentulous patient,

Zarb-Bolender, 12th Edition.