1. FACIAL NERVE
AND ITS PROSTHODONTIC IMPLICATIONS
PRESENTED BY – DR. DIPESH MADGE
1ST YEAR POST GRADUATE STUDENT
DEPARTMENT OF PROSTHODONTICS
2. CONTENTS
• INTRODUCTION
• NERVE AND ITS CONDUCTION
• CLASSIFICATION OF NERVOUS SYSTEM
• INTRODUCTION TO FACIAL NERVE
• NUCLEI OF ORIGIN
• FUNCTIONAL COMPONENTS
• COURSE
• BRANCHES AND DISTRIBUTION
• GANGLIA
• BLOOD SUPPLY
• APPLIED ASPECTS
• SYNDROMES ASSOCIATED WITH FACIAL NERVE
• PROSTHODONTIC IMPLICATIONS
• CONCLUSION
3. WHAT IS NERVE?
A bundle of fibres that uses
electrical and chemical signals
to transmit sensory and motor
information from one body part
to another.
4. NERVE AND IT’S CONDUCTION
1. The Neuron (nerve cell)- is
the structural unit of the
nervous system.
2. It transmits messages
between the CNS and all
parts of the body.
5. NERVE AND IT’S CONDUCTION
3. There are two basic types of neurons:
the sensory(afferent) and motor (efferent).
4. Sensory neurons- are capable of transmitting
the impulses from site to the CNS.
5. Motor neurons- conduct impulses from the
CNS toward the periphery.
8. INTRODUCTION TO FACIAL NERVE (Nervus facialis)
● There are 12 cranial nerves.
● The Facial nerve is the 7th cranial nerve (CN VII).
● It is the nerve of the second branchial arch.
● Hence supplies all the muscles that develop
from the mesoderm of this arch.
● It is a mixed nerve with a large motor root and a
small sensory root.
9. MICROANATOMY OF FACIAL NERVE
● It is estimated that each of the
7000 neuron cell bodies which
extend axons from the facial
nucleus innervates 25 muscle
fibres.
● The smaller the ratio of muscle
fibres to neuron cell bodies , the
greater is the degree of specialized
movement possible.
10. ● Diameter of facial nerve axons varies between
3-20 µm and the nodes of Ranvier are spaced
from 0.1-1.8µm apart.
● Because facial nerve fibres are myelinated the
wave of depolarization can jump from one
node of Ranvier to the next, a process called
saltatory conduction.
● This accounts for the rapid conduction velocity
of the facial nerve, which is 70-110m/sec.
11. EMBRYONIC DEVELOPMENT
● It is Derived from 2nd branchial
arch.
● Course of FN, its branching
pattern, anatomical
relationships are established
during first three months of
prenatal life.
● The nerve is not fully developed
until about 4 years of age.
12. ● The motor division from– basal plate of
the embryonic pons.
● Sensory division from- the cranial neural
crest.
● Nerve fibres for taste are supplied by chorda
tympani branch of facial nerve.
● supplies motor and sensory innervations to
the muscles formed by hyoid arch.
13. NUCLEI OF ORIGIN AND THEIR COMPONENTS
● THE FIBRES OF FACIAL NERVE ARE
CONNECTED TO FOUR NUCLEI :
1. MOTOR NUCLEUS
2. NUCLEUS OF TRACTUS
SOLITARIUS
3. SUPERIOR SALIVATORY NUCLEUS
4. UPPER PART OF THE SPINAL
TRACT OF THE TRIGEMINAL NERVE
14. ● Motor nucleus: divided into
lateral, intermediate and medial
lemnisci
● Lateral portion supplies muscles around
the mouth and buccinator.
● Intermediate portion supplies muscles
of upper face including orbicularis oculi.
● Medial portion supplies the stapedius,
stylohyoid, posterior belly of digastric,
platysma and occipitofrontalis.
15. ● Nucleus of Tractus
Solitarius:
Special sensory
nucleus Brings
sensations from the
anterior 2/3rd of
tongue and palate.
19. STRUCTURE
● Two roots – sensory root and motor root.
● Sensory Root: Also called as nervous intermedius.
● Conveys gustatory fibres from anterior 2/3rd of the tongue
20. ● Secretory and vasomotor fibres supplies to :
lacrimal gland
submandibular and sublingual salivary glands
glands of nasal and palatine mucosa.
● Carries Cutaneous sensory impulses from external
auditory meatus and the region back of the ear.
21. ● Motor root: Largest root
● Supplies muscles of face, scalp and auricle,
the buccinator, platysma, stapedius,
stylohyoid and the posterior belly of
digastric.
22. COURSE
● The path of facial nerve can be divided into six
segments :
1) Intracranial segment: Motor part arises from the facial
nucleus
Sensory and parasympathetic parts from sensory
nucleus and superior salivatory nucleus
2) Meatal segment: Enters the petrous temporal bone via
internal auditory meatus.
23. 3)Labyrinthine segment: Short and contains
geniculate ganglion.
4) Tympanic segment: Facial nerve runs through
the tympanic cavity.
5) Mastoid segment: It has Pyramidal eminence.
Chorda tympani and nerve to stapedius in the
temporal part.
6) Extratemporal segment: Emerges out from
stylomastoid foramen and gives five terminal
branches.
24. INTRACRANIAL COURSE
1) Intrapontine Course:
The fibres from the motor nucleus course
through the pons taking a sharp bend around
the abducent nucleus producing internal
genu of the facial nerve and they leave the
pons between the nucleus of spinal tract of
trigeminal and the other facial nucleus.
25. 2) Attachment to the
brain stem:
The sensory and motor roots
are attached to the lateral
aspects of the pontomedullary
junction.
26. 3) Course Through Posterior
Cranial Fossa:
From the superficial attachment to the brainstem to
the opening of the internal acoustic meatus the two
roots of the facial nerve pass laterally and forward in
the cerebellopontine angle along with
vestibulocochlear nerve and labyrinthine artery.
These structures together enter the internal acoustic
meatus.
27. INTRAPETROUS COURSE
1) Meatal segment:
It is in the internal acoustic meatus where the motor
root is lodged in a groove on the antero-inferior
surface of the vestibulocochlear nerve, but the
sensory root separates them.
At the bottom of the internal acoustic meatus , the
two roots unite to form the trunk of the facial nerve
and then it enters the facial canal.
28. ● Facial canal part : Divided into 3 segments
2) Labyrinthine segment :
passes laterally above the vestibule of the inner ear to
reach the anterior end of the medial wall of the middle
ear.
Here it bends backwards at a sharp turn called the
external genu of the facial nerve which has the
geniculate ganglion on it.
29. 3) Tympanic segment :
● Passes backwards in the medial wall of the
middle ear till it reaches the posterior end of
this wall.
● It is also known as the horizontal part.
30. 4) Mastoid segment or
vertical segment:
Begins at the posterior end of the medial
wall and passes downwards in relation to
the posterior wall of the middle ear to
reach the stylomastoid foramen.
32. ● The facial nerve crosses
the lateral side of the base
of the styloid process.
● It enters the posteromedial
surface of the Parotid
gland.
EXTRACRANIAL COURSE
33. Within the gland it runs forward for a short distance
superficially to the retromandibular vein and external carotid
artery and then divides into :
1. Temporofacial Trunk
2. Cervicofacial Trunk
34. ● The terminal branches radiate like a goose’s foot from the
anterior border of the parotid gland –
“Pes anserinus”
40. ● Carries gustatory and parasympathetic fibres.
● Arises from the geniculate ganglion of the facial nerve,
and enters the middle cranial fossa through the hiatus
for the greater petrosal nerve on the anterior surface of
the petrous temporal bone.
● It proceeds towards the foramen lacerum where it joins
the deep petrosal nerve which carries sympathetic fibres
to form nerve of pterygoid canal.
41. ● The nerve of the pterygoid canal passes through the pterygoid
canal to reach the pterygoplatanine ganglion. The
parasympathetic fibres relay in this ganglion.
● Postganglionic parasympathetic fibres arising in the ganglion
ultimately supply the lacrimal gland and the mucosal glands
of the nose, palate and pharynx.
The gustatory or taste fibres do not relay in the ganglion and
are distributed to the palate.
42. NERVE TO THE STAPEDIUS
● Arises opposite the pyramid
of the middle ear and
supplies the stapedius
muscle.
● The muscle damps excessive
vibrations of the stapes
caused by high- pitched
sounds.
43. THE CHORDA TYMPANI
● Arises in the vertical part of the facial canal about 6mm above the
stylomastoid foramen.
● It runs upwards and forwards in a bony canal. It enters the middle ear
and runs forwards in close relation to the tympanic membrane.
44. ● It leaves the middle ear by passing through
pterygopalatine fissure. It then passes medial to the
spine of the sphenoid and enters the infratemporal
fossa. Here it joins the lingual nerve through which it
is distributed.
● It carries the preganglionic fibres to the
submandibular and sublingual salivary glands and
taste fibres from the anterior two-thirds of the
tongue.
45. AT THE EXIT FROM THE STYLOMASTOID
FORAMEN
Posterior auricular nerve
● Arises just below the stylomastoid foramen.
● It ascends between the mastoid process and
the external acoustic meatus and supplies:
a) The posterior auricularis
b) The occipitalis
c) The intrinsic muscles on the back of the
auricle.
46. THE DIAGASTRIC BRANCH
● Arises close to the posterior auricular nerve.
● It is short and supplies the posterior belly of digastric.
47. STYLOHYOID BRANCH
● It arises with the digastric branch.
● It is long and supplies the stylohyoid muscle.
51. GANGLIA ASSOCIATED WITH FACIAL NERVE
1) GENICULATE GANGLION
● is located on the first bend of the
facial nerve, in relation to the
medial wall of the middle ear.
● It is a sensory ganglion.
● The taste fibres present in the
nerve are present in the
geniculate ganglion.
52. 2) SUBMANDIBULAR GANGLION
● It is a parasympathetic ganglion for relay of secretomotor
fibres to the submandibular and sublingual salivary glands.
53. ● The motor or parasympathetic fibres pass from the
lingual nerve to the ganglion through the posterior
root.
● These are preganglionic fibres that arise in the
superior salivatory nucleus and pass through the
facial nerve- the chorda tympani and the lingual nerve
to reach the ganglion.
The fibres relay in the ganglion.
55. ● It is the largest parasympathetic peripheral ganglion.
● It serves as a relay station for secretomotor fibres to
the lacrimal gland and to the mucous glands of the
nose, paranasal sinuses, palate and the pharynx.
● It is also called hay fever ganglion.
PTERYGOPLATINE GANGLION
(SPHENOPALATINE GANGLION)
56. BLOOD SUPPLY
● The facial nerve gets its blood supply from 4 vessels:
1) Anterior inferior cerebellar artery
- At the cerebellopontine angle
2) Labyrinthine artery (branch of anterior inferior cerebellar artery)
- within internal acoustic meatus
3) Superficial petrosal artery (branch of middle meningeal artery)
- geniculate ganglion and nearby parts
4) Stylomastoid artery (branch of posterior auricular artery)
- mastoid segment
57. FUNCTION
● The facial nerve is responsible for:
Contraction of the muscles of the face
Production of tears from a gland (Lacrimal gland)
Conveying the sense of taste from the anterior 2/3rd of the
tongue (via the Chorda tympani nerve)
The sense of touch at auricular conchae
59. VARIATONS OF FACIAL NERVE
BRANCHING PATTERN
● Flower (1961) reviewed seven variations including
changes in angulation.
● Curtis and May (1986) reported a case of progressive
facial nerve canal along the internal auditory canal,
creating a double internal auditory canal.
60. ● Caprosa and Klassen (1966) observed
bifurcation of facial nerve just distal to the
geniculate ganglion.
● Duncan, Shea and Sleeckx (1967) found
bifurcation of branches of the chorda
tympani.
62. THREE DEGREES OF FACIAL NERVE INJURY
Seddon’s Classification
Neuropraxia – temporary paralysis of nerve caused by lack of blood flow
or by pressure on the affected nerve with no loss of structural
continuity.
Axonotmesis
Neural tube intact but axons are disrupted.
Nerves are likely to recover.
Neurotmesis
The neural tube is compromised.
Injuries are likely permanent without repair.
64. APPLIED ANATOMY
Disorders of facial nerve:
1) Supranuclear lesions Features:
Paralysis of lower part of face (opposite side)
Partial paralysis of upper part of face
Normal taste and saliva secretion
Stapedius is not paralysed
65. 2) Infranuclear lesions Features :
Paralysis of facial muscle (same side)
Paralysis of lateral rectus
Internal strabismus
66. Localization of Peripheral lesions
1) At the Internal acoustic meatus Features :
Paralysis of secretomotor fibres
Hyperacusis
Loss of corneal reflex
Taste fibres are unaffected
Facial expression and movements are paralysed
67. 2) Injury distal to geniculate ganglion
Features:
Hyperacusis
Loss of corneal reflex
Taste fibres are affected
Facial expression and movements are
paralysed
68. 3) Injury at the Stylomastoid foramen
This Condition is known as “bells palsy”
69. HOUSE-BRACKMAN(1985) CLASSIFICATION FOR
FACIAL FUNCTION
● Grade I-normal function without weakness.
● Grade II-mild dysfunction with slight facial asymmetry with a minor degree
of synkinesis.
● Grade III-moderate dysfunctions-obvious , but not disfiguring, asymmetry
with contracture and/or hemifacial spasm , residual forehead motion and
incomplete eye closure.
● Grade IV-moderately severe dysfunction- obvious, disfiguring asymmetry
with lack of forehead motion and incomplete eye closure.
● Grade V-severe dysfunction-asymmetry at rest and only slight facial
movement.
● Grade VI-total paralysis-complete absence of tone or motion
70. BELL’S PALSY (FACIAL PALSY)
● It is defined as an idiopathic paresis
or paralysis of the facial nerve of
sudden onset.
● The name was ascribed to SIR
CHARLES BELL, who in 1821
demonstrated the separation of
motor and sensory innervation of
face.
71. ● INCIDENCE - 15-40 cases per 1 lakh cases
● SEX PREDILECTION - Women more affected than men.
3.3 times common in pregnancy and in the third trimester.
● AGE – It can occur at any age, common in middle aged
people.
● SIDE INVOLVMENT - can be equally seen, usually
unilateral.
72. CAUSES OF FACIAL NERVE PARALYSIS
1. BIRTH CAUSES :
● Facial Nerve Injury from Birth Trauma
● Trauma (forceps delivery)
● Congenital Facial Palsy:
a) Moebius syndrome
b) Cardiofacial syndrome
73. 2. INFECTIONS
● Herpes zoster virus
● Acute or chronic otitis media
● Lyme disease
● HIV infection
● Mastoiditis
● Skull base osteomyelitis
● Meningitis
● Syphilis
77. A variety of factors increase the risk of
Bell’s Palsy, some of those are:
● Pregnancy (mostly 3rd trimester)
● Preeclampsia
● Diabetes
● Hypertension
● Obesity
● Upper respiratory infection
79. CLINICAL FEATURES
Inability to smile, close eye and raise eyebrow.
Whistling is impossible.
Drooping of corners of the mouth.
Slurred speech.
Inability to close eyelid (Bell’s sign).
Loss of blinking reflex.
Inability to wrinkle forehead.
Mask like appearance of the face.
Loss or alteration of taste.
80. COURSE AND PROGNOSIS
● Partial paralysis always resolves completely within a
few weeks.
● Recovery from complete paralysis takes longer
(months) and is complete in only about 60-70% of
cases.
● Approximately 15% of patients are left with
troublesome residual palsy.
82. RAMSAY HUNT SYNDROME
A special form of herpes zoster
infection of the geniculate
ganglion with the involvement
of the external ear and the oral
mucosa.
83. GUILLIAN- BARRE SYNDROME
● Bilateral facial paralysis
● Difficulty with bladder control
or bowel function
● Rapid heart rate
● Low or high blood pressure
● Difficulty in breathing
84. MOEBIUS SYNDROME
● Results from the underdevelopment of
cranial nerve VI and VII
● The VI cranial nerve controls lateral
eye movement, and the VII cranial
nerve controls facial expression and is
manifested in infancy.
85. MELKERSON’S SYNDROME
● Recurrent attacks of facial paralysis
● Associated with multiple episodes
of non-pitting, non-inflammatory
painless edema of the face
● Chelitis granulomatosa
● Fissured tongue
86. PROSTHODONTIC IMPLICATIONS
● The most common form of facial nerve injury
is Bell’s palsy.
● The prosthodontic management of these patients
requires a systematic approach as the clinical
features of Bell’s palsy may interfere with most of
the steps such as impression making, jaw relation,
denture retention, and stability.
87. OBJECTIVES OF PROSTHODONTIC
REHABILITATION
● To support the weakened musculature.
● To decrease the number of surgical
procedures.
● To provide comfort and aesthetics.
● To increase confidence and improve social
interactions.
88. PROBLEMS FACED DURING
REHABILITATION
● Poor muscle co-ordination.
● Mask like expressionless appearance.
● Uncontrolled flow of saliva.
● Unpredictable and erratic mandibular movements.
● Difficulty with labial sounds and labiodental sounds.
● Dryness of mouth.
● Cheek biting.
89. STAGES THAT REQUIRE
MODIFICATIONS
● Making of Impressions.
● Jaw relation recording.
● Teeth arrangement.
● Denture retention.
● Denture stability.
90. NEUTRAL ZONE IMPRESSION
TECHNIQUE
Gahan and Walmsley (2005)
defined neutral zone as the area
where during function, the forces
of the tongue pressing outwards
are neutralized by the forces of
the cheeks and lips pressing
inwards.
91. MOLDING OF MUSCLES ACTIVITY
● Swallowing
● Speaking
● Sucking
● Pursing lips
● Pronouncing vowels
● Sipping water
● Slightly protruding the tongue
93. EXTENDED BUCCAL FLANGE
● In this technique, the buccal flange of the affected side is
extended.
● Extension serves as a curtain to prevent the food
escaping into the buccal corridor.
● It also enhances the stability and retention for the
mandibular denture.
94. J SHAPED BUCCAL LOOP
● It is used for stability and retention of
complete denture in edentulous patients
suffering from facial paralysis.
● The J loop also improves the facial
aesthetics.
95.
96. DENTURE WITH DETACHABLE
CHEEK PLUMPER
● Used when the slumped tissue
need extra support.
● Less in weight.
● Easy to insert and remove and
also prevents muscle fatigue.
98. FACE LIFT DEVICES
● The heat polymerizing clear acrylic buccal plate is
fabricated, which is retained through Adam's clasp on
tooth 16 and 15.
● A loop is tagged to lift the lip.
99. ● The heat polymerizing pink acrylic buccal plate is fabricated
which is retained through C clasp on 17 and 14.
● The buccal plate extended from first premolar to the second
molar area on the affected side. Wax block is designed on the
plate to camouflage the asymmetry.
101. CONCLUSION
● The poor neuromuscular control is considered to be the main
reason for the poor voluntary movements of the mandible.
● Edentulous patients are unable to perform satisfactory
mandibular functional movements as they receive very
limited input signals and proprioception from muscle fibres.
● The modification of conventional method of complete
denture fabrication and planning of a systematic approach to
improve the mandibular movements, a good prosthetic
rehabilitation can be done.
102. REFERENCES
● B D Chaurasia’s Human Anatomy Volume 3 5th ed.
● Shafer’s textbook of Oral Pathology, 7th ed.
● Textbook of Oral and Maxillofacial Surgery, Neelima
Malik, 3rd ed.
● Prosthodontic Rehabilitation of Patients with
Bell's Palsy: Our Experience. J Int Oral Health.
2015;7(Suppl 2):77-81.
