Muscles Of Facial Expression

MUSCLES OF FACIAL EXPRESSIONS

Presented by: Harsha vardhan k.v Department of prosthodontics SVSIDS

CONTENTS

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INTRODUCTION

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EMBRYOLOGY

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CLASSIFICATION

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ANATOMY OF FACIAL MUSCLES AND ITS PROSTHODONTIC SIGNIFICANCE

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FACIAL EXPRESSIONS AND CONCERNED MUSCLES

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FACIAL MUSCLES DISORDERS

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REFERENCES

INTRODUCTION Face is ‘Window of the soul’. Facial expressions are a form of nonverbal communication. Facial expression results from one or more motions or positions of the muscles of the face. These movements convey the emotional state of the individual to observers. The importance of facial musculature in dentistry is emphasized, to create a desire to learn more, and point out what information is known or felt to be of direct consequence to the art and science of complete denture prosthodontics. The action of muscles as prime movers of the mandible and hence as the power for repeated occlusion of the teeth. They are active during mastication, deglutition and speech. Has a direct or indirect influence on the peripheral extensions, shape and thickness of denture bases, the position of the teeth both horizontally and vertically and facial appearance. The import of the raised eye brow, a contemplative frown or any contagious smile is often far more a key to the individual than the spoken words which may accompany these expressions. The fleeting and varied facial movements is responsible for personality and are characteristics of an individual. The modifications or loss of such characteristics has a tremendous psychologic impact on a patient.Preservation of these important functions is necessarily the responsibility of the dentist charged with prosthodontic treatment of the patient.

To know about various expression we should first know the anatomy of muscles of facial expression.

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The muscles of facial expression are located in the subcutaneous tissue, originating from bone or fascia, and inserting onto the skin.

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By contracting, the muscles pull on the skin and exert their effects. They are the only group of muscles that insert into skin.

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They migrate from the arch, taking their nerve supply with them.

EMBRIOLOGY These muscles have a common embryonic origin – the 2nd pharyngeal arch.

SECOND PHARYNGEAL ARCH •

The cartilage of the second or hyoid arch (Reichert’s cartilage) gives rise to the stapes, styloid process of the temporal bone, stylohyoid ligament, and ventrally, the lesser horn and upper part of the body of the hyoid bone.

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Muscles of the hyoid arch are the stapedius, stylohyoid, posterior belly of the digastric, auricular, and muscles of facial expression.

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Each pharyngeal arch is supplied by its own cranial nerve.

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The nerve of the second arch is supplied by the facial nerve.

CLASSIFICATION The facial muscles can broadly be split into three groups; orbital, nasal and oral. 

ORBITAL GROUP 1. ORBICULARIS OCULII 2. CORRUGATOR SUPERCILLI 3. LEVATOR PALPEBRE SUPERIORIS

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NASAL GROUP 1. PROCERUS 2. COMPRESSOR NARIS 3. DILATOR NARIS 4. DEPRESSOR SEPTI

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ORAL GROUP 1. ORBICULARIS ORIS 2. LEVATOR LABII SUPERIORIS 3. ZYGOMATICUS MAJOR 4. LEVATOR ANGULI ORIS 5. ZYGOMATICUS MINOR 6. DEPRESSOR ANGULI ORIS 7. DEPRESSOR LABII INFERIORIS 8. MENTALIS 9. RISORIUS 10. BUCCINATOR

THE ORBICULARIS OCULI MUSCLE It is Broad, flat, elliptical muscle. Surrounded by orbital opening. Spread into anterior temporal region, infraorbital cheek region and superciliary region •

This muscle, closes the lids when blinking and allows you to squint or wink your eye, is one of the muscle that affect the functions of the lids.

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The muscle has fibers that form two semicircles, one above and one below the eye.

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These fibers arise on the nasal part of the frontal bone, on the frontal process of the maxilla in front of the lacrimal goove, and on the borders of the medial canthal tendon.

Action 

Palpebral part - Mediates involuntary eye closure, such as blinking.

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Orbital part - Provides voluntary eyelid closure, such as a response to bright light.

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Lacrimal Part - When the eyelid closes, the lacrimal portion pulls the inside corners of the lid toward the nose and turns them inward slightly. This action positions tiny holes, called puncta, in the most favorable position to collect tears.

BLOOD SUPPLY 

Superficial temporal artery

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Maxillary artery

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Opthalmic artery

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Facial artery

NERVE SUPPLY 

Temporal and zygomatic branch of facial nerve

CLINICAL SIGNIFICANCE 

As it is the only muscle capable of closing the eyelid, disruption of the function of this muscle produces exposure of the eyeball, requiring lubricants and possibly, surgery.

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Blepharospasm is a condition in which the eyelids twitch or blink involuntarily. In cases of blepharospasm, the orbicularis oculi muscles contract excessively.

THE CORRUGATOR SUPERCILII AND THE PROCERUS MUSCLES

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Corrugator in Latin- wrinkle. Supercilii in Latin-hairs above the eye-lashes or the eyebrows. Cilia in Latin lashes of the lid. Procerus Greek, before the horn. These are the frowning muscles. Both have fibers that originate with the frontalis muscle and insert just above the root of the nose.

THE AURICULARIS MUSCLES • There are three of them: anterior, superior, and posterior. The anterior muscle is in front, the superior muscle above and the posterior muscle behind the ear. •

These are very superficial muscles whose attachments are not to bone but to underlying fascia.

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Most people cannot use these muscles, but if they can, they are able to wiggle their ears

THE NASALIS MUSCLE • The nasalis muscle allows you to flare your nostrils. • One part arises from the tendinous end of the procerus muscle at the bridge of the nose, on each side of the nose, and the other part goes from the tip and over the outside of the nostrils.

THE DEPRESSOR SEPTI MUSCLE • The depressor septi muscle draws the nose downward. • It arises from the maxilla, just under the nose, and inserts into the septum of the nose.

THE BUCCINATOR MUSCLE •

The buccinator is the muscle of the cheek which aids in chewing by holding the cheek close to the teeth.

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It arises from the outer surfaces of the maxilla, the mandible, and the superior constrictor pharyngis muscle, and is joined to that muscle by the pterygomandibular raphe.

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It inserts into the orbicularis oris and the modiolus, beneath the risorius muscle.

ACTION 

Flattens cheek against gums and teeth which prevents food accumulation

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Whistling muscle

BLOOD SUPPLY 

Facial artery

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Buccal branch of maxillary artery

NERVE SUPPLY 

Buccal branch of facial nerve

PROSTHODONTIC SIGNIFICANCE 1. In lower jaw it becomes part of denture bearing area in buccal shelf region. 2. Its action is parallel to plane of occlusion. 3. Activation of masseter pushes the buccinator medially in distobuccal region, which accommodates masseteric notch in the denture border. If not recorded properly can cause dislodging of denture. 4. In upper jaw- its position of origin in the upper jaw determines the vertical height of distobuccal flange of the maxillary denture. 5.

If the Distobuccal flange of the denture base is not contoured to allow freedom for this action, the denture will be displaced.

6. Its action pulls the corner of the mouth laterally and posteriorly.

THE ORBICULARIS ORIS MUSCLE Broad, flat, elliptical muscle Surround orbital opening Spread into anterior temporal region, infraorbital cheek region and superciliary region One section joins in the middle of the upper lip forming a little “gutter” under the nose. Another is in the middle of the lower lip without a gutter. •

This muscle is used when you to close your mouth and to pout.

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It has some similarities with the orbicularis oculi muscle, discussed above, in that its fibers encircle the mouth just as the fibers of the oculi muscle encircle the eye, and both are sphincter muscles.

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Most of these fibers go around the mouth, but unlike the fibers of the oculi muscle, they are in four sections with some of the fibers attaching to the underside of the skin.

ACTION 1. Puckering of lip 2. Closes mouth 3. Pursing of lips BLOOD SUPPLY 1. Superior labial artery 2. Inferior labial artery 3. Infraorbital artery 4. Mental artery 5. Transverse facial artery NERVE SUPPLY 1. Buccal 2. Marginal mandibular branch of facial nerve PROSTHODONTIC SIGNIFICANCE 1. Upper lip is supported by maxillary anterior teeth and not the denture border. 2. When teeth are in occlusion, the superior border of the lower lip is supported by incisal third of the maxillary anterior teeth. If not so lower lip would get caught between the anterior teeth during occlusal contacting. 3. When muscles are relaxed, lips become flaccid. This can happen with the jaws open and is important in impression making. 4. Angle of mouth are easily irritated when an impression tray is inserted. 5. On wide opening the Orbicularis oris muscle along with the muscle of lower lip becomes stretched and the sulcus will be narrow. 6. If the flange is thick, this would displace the mandibular denture and hence impressions will be narrow in the anterior region.

THE LEVATOR ANGULI ORIS MUSCLE •

This muscle contributes to the naso-labial fold in the cheek.

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It leaves the upper lip exposing the teeth when smiling.

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It originates on the maxilla just below the Infraorbital foramen and inserts into the modiolus.

THE DEPRESSOR ANGULI ORIS MUSCLE •

The depressor anguli oris muscle of the lower lip aids in drawing the lower lip downward.

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It inserts at the modiolus, mingling its fibers with the risorius and the orbicularis oris, and arises out of the fibers of the platysma muscle

MODIOLUS •

Dense, compact, mobile, fibromuscular consisting of terminal fibres of muscles converging towards or diverging from it.

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Total of 9 muscles are attached to it.

1. orbicularis oris, 2. buccinator, 3. levator anguli oris, 4. depressor anguli oris, 5. zygomaticus major, 6. risorius, 7.

platysma,

8. levator labii superioris. 9. Mentalis

PROSTHODONTIC SIGNIFICANCE 

The importance of this hub /nave region where all the radial muscles converge is recognized by us.

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Lightoller describes it as a thick mass just distal to the corner of mouth with a total vertical depth of 3.5-4.5 mm from the exterior to the mucous membrane.

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It is flattened cone shape and extreme mobile. It can be fixed instantly and moved voluntarily.

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Dentures should be constructed not only to accommodate it but also to allow for its flexibility and for its radial muscle components.

PLATYSMA 

The platysma is a superficial muscle that overlaps the sternocleidomastoid

ORIGIN 

Upper fibers of pectoral and deltoid fascia

INSERTION 

Anterior fibers to the base of the mandible

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Posterior fibers to the skin of the lower face and lips and may be continuous with the risorius

ACTION

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Depresses the mandible

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Pulls the angle of the mouth downwards as in horror or surprise

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Releases the pressure of the skin on the subjacent veins

BLOOD SUPPLY Branches of the Submental artery and Suprascapular artery

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NERVE SUPPLY Cervical branch of the facial nerve

FACIAL EXPRESSIONS AND CONCERNED MUSCLES

LAUGHING & SMILING 

Angle of the mouth is drawn upwards and laterally

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Zygomaticus major.m

IMPORTANCE OF SMILE 

Smile is produced by the elevation of the lips assisted by retractors and the true laughter occurs when the Orbicularis oris is completely and involuntarily inhibited.

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A prosthodontic significance of a smile is the recognition that if one part of this complex is out of position will affect other components which make up the smile.

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The lips are drawn against the teeth by the elevation of the maxillary lip and the retraction of the corner of mouth.

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So the placement of teeth become extremity important in forming the backdrop for the smile.

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If the teeth are placed too far labially, the orbicularis oris is stretched and this effect tends to exert a dislodging effect on the maxillary denture.

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If there is a lack of maxillary lip support and teeth are set on the crest of the ridge, there is a downward cast to the smile which is similar to the expression of grief and this is one of the pitiful prosthodontic error.

SURPRISE 

Transverse wrinkles of forehead & bridge of the nose. Frontalis.M Procerus.M

FROWNING 

Vertical wrinkles of forehead - Corrugator supercilli.m

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Dilatation of anterior nasal aperture - Dilator naris.m Depression of lower part of nasal septum - Depressor anguli oris.m

ANGER

SADNESS 

Angle of the mouth drawn downwards and laterally - Depressor angulii oris.M

SORROW & GREIF 

Accentuation of nasolabial furrow with elevation and eversion of upper lip. Levator labii superioris.m Levator anguli oris.m Zygomaticus minor.m

GRINNING 

Retraction of angle of mouth Risorious.M

DOUBT 

Puckering of skin over chin with protrution of lower lip Mentalis.m

WHISTLING 

Pressing the cheek against gum with pursing of mouth with small opening Buccinator.M

MUSCLE DISORDERS

HEMIFACIAL SPASM 

It is a disease characterized by repeated, painless, irregular, nonrhythmic, unilateral contractures of the facial muscles.

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It is caused by compression of facial nerve in the facial canal.

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Begins in the periorbital muscles but soon spreads to the entire half face.

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Spasms are often triggered by fatigue, tension or facial activity.

FACIAL HEMIATROPY Parry–Romberg syndrome (also known as progressive hemi facial atrophy) Is a rare neurocutaneous syndrome 

Slowly progressive wasting of subcutaneous fat skin ,cartilage, bone and muscle

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Accompanied usually by contralateral Jacksonian epilepsy, trigeminal neuralgias and changes.

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Caused due to unregulated sympathetic activity

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Painless cleft near midline of face

MYSTHENIA GRAVIS 

Acquired autoimmune disorder characterize by weakness of skeletal muscle and fatigability on exertion.

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Antibodies against the ach receptors at neuromuscular junction

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Most frequently involved muscle are that of mastication and facial muscle

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Difficulty in mastication and deglutition and drooping of jaw . Speech is slow and slurred

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Diplopia and ptosis along with drooping of eyelid lead to sorrowful appearance

BELL’S PALSY 

Abrupt isolated unilateral peripheral facial nerve paralysis without detectable cause

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Inflammation of facial nerve with resultant edema cause nerve compression while it passes through temporal bone

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Infranuclear lesion of facial nerve

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Asymmetrical face draws to normal side

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Wrinkles disappear from forehead

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During mastication food accumulates between teeth and cheek

LYMPHATIC DRAINAGE OF MUSCLE OF FACIAL EXPRESSION •

Maxillary and anterior mandibular region - Ant. Middle and post. Submandibular nodes - submental nodes

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Anterior temporal, zygomatic and posterior mandibular region - parotid nodes

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Ear - retroauricular and subauricular nodes

All drain into cervical lymph nodes around the jugular vein.

CONCLUSION 

An understanding of all the muscles of facial expression is important to successful complete denture construction. These muscles must be observed at work by the dentist when he first views his patient when begins to speak.

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Prosthodontic treatment must be in terms of all functions performed in mouth.

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We should 1. Consider the role which the facial muscles play in expression 2. Analyze these muscles in terms of the expressions of various emotions 3. Evaluate their prosthodontic significance

REFERENCES 

Bones And Muscles-an Illustrated Anatomy Written And Illustrated By Virginia Cantarella

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Human Anatomy Regional & Applied 4TH Edition- B.D.Chaurasia

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Langman's Medical Embryology 8th Edition

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Anand's Human Anatomy For Dental Students 3RD Edition

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Anatomy of facial expression and its prosthodontic significance J.P.D 1962 12-6,1020– 42

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Lightoller G.S : Facial muscles: the modiolus and muscles surrounding the rima oris with some remarks about the paniculus adiposus J.anat 60:1-85, 1925-26