ABSTRACT muscles of the face. Happiness or sadness, are

ABSTRACT

     Muscles of Facial
expressions play a vital role in nonverbal form of communication and projecting
individual’s personality.  This article
presents a brief overview for clinicians of muscles of facial expressions and
their significance in prosthetic dentistry. 

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INTRODUCTION         

     The muscles of facial expression situated
in 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 immediate
cues 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 of
orifice of face.  Movements
elicited in test for Facial Nerve
function results from one or more motions or positions of
the muscles of the face. Happiness or sadness, are expressed through a
smile or a frown, respectively.  Seven universally recognized emotions shown
through facial expressions:  fear, anger, surprise, contempt, disgust,
happiness, and sadness.  These play indispensable role in Prosthetic dentistry.   A
well-fitting and retentive complete denture requires a well-fitting tissue
surface, a peripheral border compatible with the muscles and tissues which make
up the mucobuccal and mucolabial spaces so that a peripheral seal is created by
the soft tissue draping over them.  Thus
these muscles exert a direct and indirect influence upon the peripheral
extensions, shape, and thickness of denture bases, the positions of teeth
horizontally and vertically and facial appearance.

DEVELOPMENT OF FACIAL MUSCLES

     Muscles of
facial expressions are derived from the second
brachial arch.  It is known as hyoid arch or meckel’s cartilage.   Sometomeres six is responsible for the
development of facial muscles.  These are
Mesodermal in origin.

 NERVE
SUPPLY

     All muscles of Facial
expression are supplied by Facial nerve from 2nd Brachial Arch.  Facial
nerve courses through the petro us
part of the temporal bone through internal acoustic meatus with CN VIII
Than
it passes Into facial canal, along walls of the tympanic cavity exits skull via
stylomastoid foramen, most branches go through parotid gland and
divides intoTemporal, Zygomatic, Buccal, Cervical, Posterior auricular,Marginal
mandibular.

BLOOD
SUPPLY

     Muscles of Facial
expression are supplied by Facial
Artery.  It branch of External Carotid Artery. Superior and
Inferior Labial Arteries supply Upper and Lower Lip.  Angular artery supplies Nose.

 

 

BRIEF
OVERVIEW OF ALL MUSCLES OF FACIAL EXPRESSIONS

FRONTALIS

     It is Thin, quadrilateral muscle intimately
adherent to the superficial
fascia.  It is Located on the
front of the head.  It has no bony attachments.  Medial fibers are continuous with those
of the Procerus; its
immediate fibers blend with the Corrugator and Orbicularis
Oculi and are attached to the skin of the eyebrows.  The fibers are directed upward, and join
the galea aponeurotica below the coronal suture.   Primary function is to lift eyebrows (thus opposing the orbital portion of the orbicularis), especially when looking
up.  It acts when a view is too distant
or dim.  It is supplied by Ophthalmic
Artery 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 frontal
process of the maxilla in front of the lacrimal groove, and from the anterior
surface and borders of a short fibrous band, the medial palpebral ligament. 
It has Palpebral, Orbital
and lacrimal parts.  

    
The palpebral portion of
the muscle is thin and arises from
the bifurcation of the medial palpebral ligament, forms a series of concentric
curves, and is inserted into the lateral palpebral raphe. The orbital portion Arises from the nasal component of the frontal bone. Upper
orbital fibers blend with the frontal part of occipitofrontalis and the Corrugator supercilii and Inserted into
the skin and subcutaneous tissue of the eyebrow.

     The lacrimal arises from the posterior part of the lacrimal
crest, 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 the
bridge of the nose, narrowing of
the palpebral fissure and Protrusion of
the eyebrows, which reduces the amount of light entering the eyes. PALPEBRAL PART is contracted voluntarily, to close the
lids 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, cause
wrinkles in middle age (‘crow’s feet’). It is supplied by Branches
of the facial, superficial temporal, maxillary and ophthalmic arteries and Innervated by temporal and zygomatic
branches of the facial nerve.

CORRUGATOR SUPERCILLI

     It is Small, narrow, Pyramidal muscle placed
at the medial end of the eyebrow, beneath the Frontalis and just above Orbicularis Oculi and medial end of the superciliary arch. It
is inserted into the deep
surface of the skin, above the middle of the orbital arch. The Corrugator draws the eyebrow
downward and medial ward, producing the vertical wrinkles of the forehead. It
is the “frowning” muscle, and may be regarded as the principal muscle in the
expression of suffering. Its vascular Supply is through ophthalmic artery and is innervated by Facial
nerve.

PROCERUS

     This is Small pyramidal slip like muscle.  It
arises by tendinous fibers from
the fascia covering the lower part of the nasal bone and
upper part of the lateral nasal cartilage and is inserted into the skin over the lower part of the forehead between
the two eyebrows.  Fibers merge with
those of the Frontalis.   It pulls the skin between the eyebrows
downwards, which assists in flaring
the nostril and contributes to an expression of anger.  Also it draws
down the medial angle of
the eyebrow giving expressions of frowning.  This
muscle is innervated by zygomatic branch of facial nerve.

NASALIS MUSCLE

     It is Sphincter-like muscle divided into two parts, transverse and alar.  Transverse part arises
from the maxilla, expanding into a thin aponeurosis and is continuous with
opposite side muscle, and with
the aponeurosis of the Procerus.
Alar part is attached at one end to
the greater alar cartilage,
and integument at the point of the nose.
It Compresses bridge, depresses
tip of nose, and elevates corners
of 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 from
the lesser alar cartilage, and
is Inserted into the skin near
the margin of the nostrils.  The Dilator naris anterior passes from the greater alar cartilage to the integument near the margin of
the nostril.

DEPRESSOR SEPTI

     This muscle arises from the incisive fossa of the maxilla; its fibers ascend to
be inserted into the
septum and back part of the ala of the nose.  It lies between the mucous membrane and
muscular structure of the lip.  The
Depressor septi is a direct antagonist of the other muscles of the nose, drawing
the ala of the nose downward, and thereby constricting the aperture of the
nares.

muscles of the mouth

BUCCINATOR

      It is thin quadrilateral muscle.  It origins
from the outer surfaces of the alveolar processes of the maxilla and
mandible, corresponding to the three molar teeth; and behind, from the anterior
border of the pterygomandibular raphe. The fibers converge toward the angle of
the mouth, where the central fibers intersect each other, those from below
being continuous with the upper segment of the Orbicularis oris, and those from
above with the lower segment; the upper and lower fibers are continued forward
into the corresponding lip without decussation. The Buccinators compress the
cheeks, so that, during the process of mastication, the food is kept under the
immediate pressure of the teeth. When the cheeks have been previously distended
with air, these muscles expel it from between the lips, as in blowing a trumpet.

PROSTHODONTIC SIGNIFICANCE:  Overextensions of a lower denture are common
in this region, either because the impression material is viscous enough to
excessively displace the soft tissues, or because the buccinator attachment is
more medially than expected.  Any such
overextension will result in either displacement of the denture or pain.

ORBICULARIS ORIS

     It is Ring-like muscle lies within the
upper and lower lips. Contracts, it causes the lips to close.  No true bony origin. It is Not simple
sphincter muscle Consists of numerous strata of muscular fibers. It is partly
derived from the other facial muscles and partly of fibers proper to the lips
and 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 zygomaticotemporal
suture and is inserted into
the angle of the mouth. This muscle Draws
the angle of the mouth upwards and laterally as in laughing, raises the corners of the mouth. Dimples may be
caused by its variations.

ZYGOMATICUS MINIOR

     This muscle Arises from the lateral
surface of the zygomatic bone and passes downwards and medially into the
muscular substance of the upper lip. It elevates the upper lip; exposing the
maxillary teeth also it assists in deepening and elevating the nasolabial
furrow. Like other elevators of the lip this muscle curls the upper lip in
smiling, and in expressing smugness, contempt or disdain.

LEVATOR LABII SUPERIORIS

     It extends from the side of
the nose to the zygomatic bone and Inserted into
the greater alar cartilage and skin of the nose and other lateral
part of upper lip Lateral fibers, arise from the malar surface of
the zygomatic bone and passes downward and medial ward.  It elevates the Upper Lip.

QUADRATUS LABII INFERIORIS

      It arises from the oblique line of the
mandible and Inserts on the skin of the lower lip, blending in with
the orbicularis oris muscle.  Depressor labii is continuous with the fibers
of the platysma muscle.  It helps to
depress the lower lip.  This muscle
originates near to the crest of the ridge and extends down and below the
alveololabial sulcus thus its contraction can reduce the denture space.  In action it pulls the modioli forward and
tenses the buccinator thereby applying pressure on the polished surface.

LEVATOR ANGULI ORIS

      It arises
from the canine fossa of the maxilla and Inserts into and below the angle of
the mouth.  Its fibers mingle with zygomaticus
major, depressor anguli oris, orbicularis oris fibers.  It contributes in formation of Angle of the
mouth during smiling and formation of the depth and contour of the nasolabial
furrow.

DEPRESSOR ANGULI ORIS

     This is Long, linear muscle. It origins
from the mental tubercle of the mandible. 
It is Narrow fasciculus and blends at the angle of the mouth with Orbicularis
oris and Risorius. It Pass below the mental tubercle and cross the midline to
interlace with its contra lateral fellows. These constitute the transversus
menti (The ‘mental sling’).

RISORIUS

     It arises in the fascia over parotid gland,
passing horizontally forward and Inserts onto the skin at the angle of the
mouth.  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 to
produce a smile, albeit an insincere-looking one. Also it has been
suggested that the risorius is only found in humans.

MENTALIS

     It is conical fasciculus lying at the side
of the frenulum of the lower lip arising from the incisive fossa of the
mandible and Descending to attach to the skin of the chin. Mentalis raises the
lower lip, causes wrinkling the skin of the chin and Protruding and everting
the lower lip resulting in Expressing doubt or disdain. It is sometimes referred to as the
“POUTING MUSCLE Its Contraction capable of dislodging a mandibular denture
particularly when the residual ridge in anterior region is non-existent.

MODIOLUS

     The modiolus is a chiasma of facial muscles held
together by fibrous tissue, located lateral and slightly superior to each angle
of the mouth. Contributed
by the following muscles: orbicularis oris, buccinator, levator
anguli oris, depressor anguli oris, zygomaticus major, Risorius quadratus
labii superioris and quadratus labii inferioris. This Eight paired muscles of
expression in combination with the single, orbicularis oris muscle control
movements of the lips and cheeks

APPLIED ANATOMY

     Facial
muscles are dramatically affected by
the position of the artificial teeth Inadequate support makes people look older
while excessive support distorts a person’s features by making them look
stretched.  Also they play an important
part in forming the anterior and lateral portions of maxillary and mandibular
impression borders.  This is because all
of these muscles can alter the depth of vestibular sulci and unseat complete
dentures.  In dentate patients, the lips
rely on 2 types of support: 1) Intrinsic support from muscles, fibrous
connective tissue, and glands; 2) Support from underlying structures such as
the anterior teeth and associated alveolar bone.  Proper position and functional length of the
muscles that attach to the orbicularis oris include the zygomatic, quadratus
labii superior, caninus, Mentalis, quadratus labii inferior, triangularis,
buccinator, and Risorius.  Where there is
no support for the lips and face due to missing teeth, border-molded flange to
lift and support the face, and in doing so, counter gravity’s downward pull on
aging skin.  

This is used to
increase the retention and stability of Dentures.   Support
Increases esthetics and make look younger.  For Maxillary arch Orbicularis Oris an
Important Muscle.   Its Tone depends on
support received from Labial Flange and Position of Teeth Buccal Frenum is broad
and Fan shaped which is pulled by Orbicularis Oris & buccinator Backwards.   It requires
clearance for its action.  For Mandibular
Arch anteriorly Flange area has to be thin, Orbicularis Oris is responsible for
narrowing 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, result
in an aging facial appearance.  Deepening
of the nasolabial fold, a drooping of the corners of the mouth, and a loss of
vermilion border of the lips.  There is a
depression of the lips with exaggerated wrinkling.  Occlusal wear and loss of vertical dimension
make the chin more prominent, and the contours of the philtrum and mentolabial
sulcus are altered.  Appearance of lower
Half of face depends on dentures. Tensed, wrinkle lips appear due to improper
teeth arrangement. Nasolabial Fold should not be obliterating during
arrangement.

 

     BELL’S PALSY is named by Sir Charles Bell
in 1821Resulting from damage to VII cranial nerve. In Unilateral UMN contralateral
lower 1/2-2/3 of face paralysed. In
Unilateral
LMN or CN VII: entire ipsilateral face paralysed.

CLINICAL FEATURES are Weakness
on entire side of the face.  Inability to
close eye also Forehead doesn’t wrinkle. Such patients are Unable to lift their
mouth resulting in Dry mouth and impairment of taste. There is Difficulty with
eating and drinking. Also Dry eyes are present and Tooth decay and gum
disease due to reduced saliva and impairment of chewing and affected
Speech.  Usually recovery is within few
months Ocular ointments, steroid medications to reduce inflammation, Antiviral
medications – such as acyclovir Analgesics or moist heat – to relieve pain or Botulinum
toxins to relax facial muscles can be prescribed. Prosthodontic management
requires alteration in establishing Height of Occlusal plane & developing polished surface
of Dentures. Implants
are also good option for such patients.

Botulinum toxin  therapy is used to reduce the wrinkles. It is derived
from Bacterium Clostridium Botulinum Works to block the nerve impulses,
temporarily paralyzing the muscle, action seen immediately, within 5-7 days, and
it remains effective till six months.

CONCLUSION

     Face is the tangible projector panels of
mechanisms that govern emotional and social Behaviors. Facial muscles not only
help 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 in
well toned and healthy, person’s face looks younger. Thus efficiency comfort
and stability of artificial masticatory machine depends on its surrounding
biological environment.