Download Clinical Anatomy of Oral Cavity

CLINICAL ANATOMY OF ORAL CAVITY
AND SALIVARY GLANDS
Associate Professor
Dr. A. Podcheko
2015
Oral Region
•The oral region includes the oral cavity, teeth, gingivae, tongue,
palate, and the region of the palatine tonsils.
•The oral cavity is where food is ingested and prepared for
digestion in the stomach and small intestine.
•Food is chewed by the teeth, and saliva from the salivary glands
facilitates the formation of a manageable food bolus.
•Deglutition (swallowing) is voluntarily initiated in the oral
cavity.
•The voluntary phase of the process pushes the bolus from the
oral cavity into the pharynx, the expanded part of the alimentary
(digestive) system, where the automatic phase of swallowing
occurs.
Oral Cavity
•The oral cavity consists of two parts: the oral vestibule and the oral
cavity proper
•It is in the oral cavity that food and drinks are tasted and savored and
where mastication and lingual manipulation of food occur.
•The oral vestibule is the slit-like space between the teeth and buccal
gingiva and the lips and cheeks.
•The vestibule
communicates with
the exterior through
the mouth.
Oral Cavity
•The size of the oral fissure (rima oris - the oral opening) is controlled
by the circumoral muscles, such as the orbicularis oris (the sphincter of
the oral fissure), the buccinator, risorius, and depressors and elevators
of the lips (dilators of the fissure).
Oral Cavity
•The oral cavity proper is the space between the upper and the lower
dental arches (maxillary and mandibular alveolar arches and the teeth
they bear).
•It is limited laterally and anteriorly
by the maxillary and mandibular
alveolar arches housing the teeth.
•The roof of the oral cavity is formed
by the palate.
•Posteriorly, the oral cavity
communicates with the oropharynx
(oral part of the pharynx).
•When the mouth is closed and at
rest, the oral cavity is fully occupied
by the tongue.
Tongue
•The tongue (L. lingua; G. glossa) is a mobile muscular organ that can
assume a variety of shapes and positions.
•It is partly in the oral
cavity and partly in the
oropharynx.
•The tongue is involved
with mastication, taste,
deglutition (swallowing),
articulation, and oral
cleansing; however, its
main functions are
forming words during
speaking and squeezing
food into the oropharynx
when swallowing.
Parts and Surfaces of the Tongue
•The tongue has a root, a body, an apex, a curved dorsum, and an
inferior surface.
•The root of the tongue is the part of the tongue that rests on the floor
of the mouth. It is usually defined as the posterior third of the
tongue.
Parts and Surfaces of the Tongue
•The body of the tongue is the anterior two thirds of the tongue.
•The apex (tip) of the tongue is the anterior end of the body, which
rests against the incisor teeth.
•The body and apex of the tongue are extremely mobile.
Parts and Surfaces of the Tongue,
contd.
•The dorsum (dorsal surface) of the
tongue is the posterosuperior surface,
which is located partly in the oral
cavity and partly in the oropharynx.
•It is characterized by a V-shaped
groove, the terminal sulcus or groove
(sulcus terminalis), the angle of which
points posteriorly to the foramen
cecum -
small pit, frequently
absent, is the nonfunctional remnant of the
proximal part of the
embryonic thyroglossal
duct from which the thyroid
gland developed.
Parts and Surfaces of the Tongue, contd.
•The terminal sulcus divides the dorsum of the tongue into the
anterior (oral) part in the oral cavity proper and the posterior
(pharyngeal) part in the oropharynx.
•The margin of the tongue is related on each side to the lingual
gingivae and lateral teeth.
•The mucous membrane on the anterior part of the tongue is rough
because of the presence of numerous small lingual papillae (4 types)
Lingual papillae
1. Vallate papillae:
•Large and flat topped, they lie directly anterior to the terminal
sulcus and are arranged in a V-shaped row.
•They are surrounded by deep moat-like trenches, the walls of
which are studded with taste buds.
•The ducts of the serous glands of the tongue open into the
trenches.
2. Foliate papillae:
•Small lateral folds of the lingual mucosa.
•They are poorly developed in humans.
3. Filiform papillae:
•Long and numerous, they contain afferent nerve endings that are
sensitive to touch.
•These scaly, conical projections are pinkish gray and are arranged in
V-shaped rows that are parallel to the terminal sulcus, except at the
apex, where they tend to be arranged transversely.
4. Fungiform papillae:
•Mushroom shaped pink or red spots, they are scattered among the
filiform papillae but are most numerous at the apex and margins of
the tongue.
•The vallate, foliate, and most of the fungiform papillae contain taste
receptors in the taste buds.
Groove of the tongue
•The mucous membrane over the anterior part of the dorsum of the
tongue is thin and closely attached to the underlying muscle.
•A shallow midline groove of the tongue divides the tongue into right
and left halves.
•The groove also indicates the site of fusion of the embryonic distal
tongue buds.
Posterior part of the tongue
•The mucous membrane of the posterior part of the tongue is thick
and freely movable.
•It has no lingual papillae, but the underlying lymphoid nodules give
this part of the tongue an irregular, cobblestone appearance.
•The lymphoid nodules are known collectively as the lingual tonsil.
•The pharyngeal part of the tongue constitutes the anterior wall of
the oropharynx and can be inspected only with a mirror or downward
pressure on the tongue with a tongue depressor.
Inferior surface of the tongue
•The inferior surface of the tongue is covered with a thin, transparent
mucous membrane through which one can see the underlying veins.
•This surface is connected to the floor of the mouth by a midline fold
called the frenulum of the tongue.
•The frenulum allows the anterior part of the tongue to move freely.
Inferior surface of the tongue
•On each side of the frenulum, a deep lingual vein is visible through the
thin mucous membrane.
•A sublingual caruncle (papilla) is present on each side of the base of the
lingual frenulum that includes the opening of the submandibular duct
from the submandibular salivary gland.
Muscles of the Tongue
•The tongue is essentially a mass of muscles that is mostly covered by
mucous membrane.
•The muscles of the tongue do not act in isolation and some muscles
perform multiple actions; parts of a single muscle are capable of acting
independently, producing different, even antagonistic actions.
•In general, however, extrinsic muscles alter the position of the
tongue while intrinsic muscles alter its shape.
•The four intrinsic and four extrinsic muscles in each half of the tongue
are separated by a median fibrous lingual septum, which merges
posteriorly with the lingual aponeurosis.
Tongue
Extrinsic Muscles of the Tongue
• palatoglossus
• styloglossus
• hyoglossus
• genioglossus
Tongue
Proximal
Muscle
Shape and Position Attachment
Extrinsic muscles of the tongue
Genioglossus
Distal Attachment
Main Action(s)
Fan-shaped muscle; Via a short tendon Entire dorsum of tongue; Bilateral activity depresses tongue,
constitutes bulk of from superior part inferior most and posterior especially central part, creating a
tongue
of mental spine of most fibers attach to body longitudinal furrow; posterior part
mandible
of hyoid bone
pulls tongue anteriorly for
protrusion; most anterior part
CNXII
21
retracts apex of protruded tongue;
unilateral contraction deviates
(wags•
) tongue to contralateral side
Tongue
Proximal
Muscle
Shape and Position Attachment
Extrinsic muscles of the tongue
Hyoglossus
CNXII
Thin, quadrilateral
muscle
Distal Attachment
Body and greater Inferior aspects of lateral
horn of hyoid
part of tongue
bone
Main Action(s)
Depresses tongue,
especially pulling its sides
inferiorly; helps shorten
(retrude) tongue
Tongue
Proximal
Muscle
Shape and Position Attachment
Extrinsic muscles of the tongue
Styloglossus
CNXII
Palatoglossus
CNX
23
Small, short
triangular muscle
Distal Attachment
Main Action(s)
Anterior border of Sides of tongue posteriorly, Retrudes tongue and curls
distal styloid
interdigitating with
(elevates) its sides, working with
process; stylohyoidhyoglossus
genioglossus to form a central
ligament
trough during swallowing
Narrow crescentPalatine
Enters posterolateral
Capable of elevating posterior
shaped palatine
aponeurosis of
tongue transversely,
tongue or depressing soft palate;
muscle; forms
soft palate
blending with intrinsic
most commonly acts to constrict
posterior column of
transverse muscles
isthmus of fauces
isthmus of fauces
Tongue
Intrinsic Muscles of the Tongue
– The superior and inferior longitudinal
– transverse
– vertical muscles
• They have their attachments entirely within the tongue and are not attached to bone
• The superior and inferior longitudinal muscles act together to make the tongue short
and thick and to retract the protruded tongue
• The transverse and vertical muscles act simultaneously to make the tongue long and
narrow, which may push the tongue against the incisor teeth or protrude the tongue
from the open mouth (especially when acting with the posterior inferior part of the
genioglossus).
• Innervation is CN XII
Innervation of the Tongue
•All muscles of the tongue, receive motor innervation from CN XII, the
hypoglossal nerve, except the palatoglossus m. (CN X, vagus nerve)
Innervation of the Tongue
•For general sensation (touch and temperature), the mucosa of the
anterior two thirds of the tongue is supplied by the lingual nerve, a
branch of CN V3.
Innervation of the Tongue
•For special sensation (taste), anterior 2/3rd part of the tongue, except
for the vallate papillae, is supplied through the chorda tympani nerve,
a branch of CN VII.
•The chorda tympani joins the lingual nerve and runs anteriorly in its
sheath.
Innervation of the Tongue
•chorda tympani nerve - branch of CN VII
•The chorda tympani joins the lingual nerve and runs anteriorly in its
sheath.
Innervation of the Tongue
•The mucous membrane of the
posterior third of the tongue and the
vallate papillae are supplied by the
lingual branch of the glossopharyngeal
nerve (CN IX) for both general and
special sensation.
•Small branches of the internal
laryngeal nerve (CN X), supply mostly
general but some special sensation to
a small area of the tongue just
anterior to the epiglottis.
•These mostly sensory nerves also
carry parasympathetic secretomotor
fibers to serous glands in the tongue.
Innervation of the Tongue
•Parasympathetic fibers from the chorda tympani nerve travel with
the lingual nerve to the submandibular and sublingual salivary glands.
•These nerve fibers synapse in the submandibular ganglion, which
hangs from the lingual nerve.
Taste Anatomy
•There are four basic taste sensations: sweet, salty, sour, and bitter.
•Sweetness is detected at the apex, saltiness at the lateral margins,
and sourness and bitterness at the posterior part of the tongue.
•All other ‘tastes’ expressed by gourmets are olfactory (smell and
aroma).
Vasculature of the Tongue
•The arteries of the tongue are derived from the lingual artery, which
arises from the external carotid artery.
•On entering the tongue, the lingual artery passes deep to the
hyoglossus muscle.
•The dorsal lingual arteries supply the posterior part (root); the deep
lingual arteries supply the anterior part.
Vasculature of the Tongue
•The veins of the tongue are the dorsal lingual veins, which
accompany the lingual artery; the deep lingual veins, which begin at
the apex of the tongue, run posteriorly beside the lingual frenulum to
join the sublingual vein.
•The sublingual veins in elderly
people are often varicose
(enlarged and tortuous).
•All these lingual veins
terminate, directly or indirectly,
in the internal jugular vein.
The lymphatic drainage of the tongue is
exceptional
•Most of the lymphatic drainage converges toward and follows the
venous drainage; however, lymph from the tip of the tongue, frenulum,
and central lower lip runs an independent course.
•Lymph from the tongue takes 4
routes:
1. Lymph from the posterior third
drains into the superior deep cervical
lymph nodes.
2. Lymph from the medial
part of the anterior two
thirds drains directly to the
inferior deep cervical lymph
nodes.
3. Lymph from the lateral parts of the anterior two thirds drains to the
submandibular lymph nodes.
4. The apex and frenulum drain to the submental lymph nodes.
Gag Reflex
•It is possible to touch the anterior part of the tongue without
feeling discomfort; however, when the posterior part is touched,
the individual gags.
•Glossopharyngeal (CN
IX) and vagus (CN X)
are responsible for the
muscular contraction
of each side of the
pharynx.
•Glossopharyngeal
branches provide the
afferent limb of the gag
reflex.
Paralysis of the Genioglossus
•When the genioglossus muscle is paralyzed, the tongue has a
tendency to fall posteriorly, obstructing the airway and
presenting the risk of suffocation.
•Total relaxation of the genioglossus muscles occurs during general
anesthesia; therefore, an airway (intubation tube) is inserted in an
anesthetized person to prevent the tongue from relapsing.
Injury to the Hypoglossal Nerve
•Trauma, such as a fractured mandible, may injure the hypoglossal
nerve (CN XII), resulting in paralysis and eventual atrophy of one side
of the tongue.
•The tongue deviates to the
paralyzed side during protrusion
because of the action of the
unaffected genioglossus muscle
on the other side.
•Main action of Genioglossus:
Bilateral activity depresses tongue,
especially central part, creating a
longitudinal furrow; posterior part
pulls tongue anteriorly for
protrusion; most anterior part
retracts apex of protruded tongue;
unilateral contraction deviates
tongue to contralateral side.
Sublingual Absorption of Drugs
For quick absorption of a drug, for instance, when nitroglycerin is used
as a vasodilator in angina pectoris, the pill or spray is put under the
tongue where it dissolves and enters the deep lingual veins in less
than 1 min.
Salivary Glands
• The salivary glands are the parotid,
submandibular, and sublingual glands.
•
The clear, tasteless, odorless viscid
fluid, saliva, secreted by these glands
and the mucous glands of the oral
cavity:
– Keeps the mucous membrane of the
mouth moist.
– Lubricates the food during mastication.
– Begins the digestion of starches.
– Serves as an intrinsic mouthwash.
– Plays significant roles in the prevention
of tooth decay and in the ability to
taste.
• In addition to the main salivary glands,
small accessory salivary glands are
scattered over the palate, lips, cheeks,
tonsils, and tongue.
40
Parotid Gland
• is the largest of three paired salivary
glands.
• is enclosed within a tough fascial capsule,
the parotid sheath, derived from the
investing layer of deep cervical fascia .
• has an irregular shape because the area
occupied by the gland, the parotid bed, is
anteroinferior to the external acoustic
meatus, where it is wedged between the
ramus of the mandible and the mastoid
process .
• Fatty tissue between the lobes of the
gland confers the flexibility the gland must
have to accommodate the motion of the
mandible.
• The apex of the parotid gland is posterior
to the angle of the mandible, and its base
is related to the zygomatic arch.
• The subcutaneous lateral surface of the
parotid gland is almost flat.
.
41
Parotid Gland
• The parotid duct passes horizontally from the anterior edge of the gland .
The parotid duct
42
Parotid Gland
• At the anterior border of the masseter, the duct turns medially, pierces the buccinator,
and enters the oral cavity through a small orifice opposite the 2nd maxillary molar
tooth.
Stensen's duct: also known
as
the
parotid
duct,
serves as a conduit for
saliva between the parotid
gland and the oral cavity.
Blockage of the duct can
lead to inflammation and
pain of the parotid gland
(parotitis).
Parotid Gland
• Embedded within the substance of the parotid gland, from superficial to deep, are the
parotid plexus of the facial nerve (CN VII) and its branches ,the retromandibular vein,
and the external carotid artery.
facial nerve (CN VII)
retromandibular vein
external carotid artery
44
Innervation of Parotid Gland and Related Structures
•
•
•
Although the parotid plexus of CN VII is embedded within it, the CN VII does NOT provide innervation to the
gland.
The auriculotemporal nerve, a branch of CN V3, is closely related to the parotid gland and passes superior to
it with the superficial temporal vessels provide innervation to the gland – Provides sensory innervation!!!!
The auriculotemporal nerve
45
Innervation of Parotid Gland and Related Structures
• The great auricular nerve, a branch of the cervical plexus composed of fibers from C2 and
C3 spinal nerves, innervates the parotid sheath as well as the overlying skin.
The great auricular nerve
46
Innervation of Parotid Gland and Related Structures
Innervation of Parotid Gland and Related Structures
• The parasympathetic component of the glossopharyngeal nerve (CN IX) supplies
presynpatic secretory fibers to the otic ganglion.
• The postsynaptic parasympathetic fibers are conveyed from the ganglion to the
gland by the auriculotemporal nerve .
Innervation of Parotid Gland and Related Structures
• Sympathetic fibers are derived from the cervical ganglia through the external
carotid nerve plexus on the external carotid artery .The vasomotor activity of
these fibers may reduce secretion from the gland.
• Sensory nerve fibers pass to the gland through the great auricular and
auriculotemporal nerves.
auriculotemporal nerves.
great auricular Nerve
48
Parotid Gland- Clinical Note
Parotidectomy
• About 80% of salivary gland tumors
occur in the parotid glands.
• Most tumors of the parotid glands are
benign, but most salivary gland cancer
begins in the parotid.
• Because the parotid plexus of CN VII is
embedded in the parotid gland, the
plexus and its branches are in jeopardy
during surgery.
• An important step in parotidectomy is
the identification, dissection, isolation,
and preservation of the facial nerve.
49
Parotid Gland- Clinical Note
Infection of the Parotid Gland
•
•
•
50
The parotid gland may become infected by infectious
agents that pass through the bloodstream, as occurs in
mumps, an acute communicable viral disease.
Infection of the gland causes inflammation (parotiditis)
and swelling of the gland.
Severe pain occurs because the parotid sheath limits
swelling. Often the pain is worse during chewing
because the enlarged gland is wrapped around the
posterior border of the ramus of the mandible and is
compressed against the mastoid process of the
temporal bone when the mouth is opened.
The mumps virus may also cause inflammation of the
parotid duct, producing redness of the parotid papilla,
the small projection at the opening of the duct into the
superior oral vestibule. Because the pain produced by
mumps may be confused with a toothache,
redness of the papilla is often an
early sign that the disease
involves the gland and not a
tooth.
•Parotid gland disease often causes pain in the
auricle, external acoustic meatus, temporal
region, and TMJ because the
auriculotemporal nerve, from which the
parotid gland and sheath receive sensory fibers,
also supplies sensory fibers to the skin over the
temporal fossa and auricle.
Parotid Gland- Clinical Note
Abscess in the Parotid Gland
• A bacterial infection localized in the parotid gland usually produces an abscess.
• The infection could result from extremely poor dental hygiene and spread to the gland through
the parotid ducts. Physicians and dentists must determine whether a swelling of the cheek results
from infection of the parotid gland or from an abscess of dental origin.
51
Parotid Gland- Clinical Note
Sialography of the Parotid Duct
• A radiopaque fluid can be injected into the duct system of the parotid gland
through a cannula inserted through the orifice of the parotid duct in the
mucous membrane of the cheek. This technique (sialography) is followed by
radiography of the gland. Parotid sialograms (G. sialon, saliva + G. grapho, to
write) demonstrate parts of the parotid duct system that may be displaced or
dilated by disease.
52
Parotid Gland- Clinical Note
Blockage of the Parotid Duct
• The parotid duct may be blocked by a calcified deposit, called a sialolith or calculus . The
resulting pain in the parotid gland is made worse by eating. Sucking a lemon slice is painful
because of the buildup of saliva in the proximal part of the blocked duct.
Accessory Parotid Gland
• Sometimes an accessory parotid gland lies on the masseter muscle between the parotid duct
and the zygomatic arch. Several ducts open from this accessory gland into the parotid duct.
53
Submandibular Glands
• Lie along the body of the mandible, and partly superficial and partly deep to the mylohyoid
muscle .
• The submandibular duct, approximately 5 cm long
– opening by one to three orifices on a small sublingual papilla beside the base of the
lingual frenulum. The orifices of the submandibular ducts are visible, and saliva can
often be seen trickling from them (or spraying from them during yawning).
• The arterial supply is from the submental arteries . The veins accompany the arteries.
54
Submandibular Glands
• are supplied by presynaptic parasympathetic secretomotor fibers conveyed from the facial
nerve to the lingual nerve by the chorda tympani nerve, which synapse with postsynaptic
neurons in the submandibular ganglion .
• The latter fibers accompany arteries to reach the gland, along with vasoconstrictive
postsynaptic sympathetic fibers from the superior cervical ganglion.
• The lymphatic vessels of the glands end in the deep cervical lymph nodes, particularly the
jugulo-omohyoid node .
Sublingual Glands
• the smallest and most deeply situated
of the salivary glands .
• Each almond-shaped gland lies in the
floor of the mouth between the
mandible and the genioglossus muscle.
• The glands from each side unite to form
a horseshoe-shaped mass around the
connective tissue core of the lingual
frenulum.
• Numerous small sublingual ducts open
into the floor of the mouth along the
sublingual folds.
• The arterial supply - branches of the
lingual and facial arteries
• The
nerves:
Presynaptic
parasympathetic secretomotor fibers
are conveyed by the facial, chorda
tympani, and lingual nerves to synapse
in the submandibular ganglion
Salivary Glands
Frenectomy
•An overly large lingual frenulum interferes with tongue
movements and may affect speech.
•In unusual cases, a frenectomy (cutting the frenulum) in
infants may be necessary to free the tongue for normal
movement and speech.
Ankyloglossia, also known as tongue-tie
Oral Region
Gingivae
• The gingivae (gums)
– are composed of fibrous
tissue covered with mucous
membrane.
– The
gingiva
(attached gingiva)
•
•
proper
is firmly attached to the
alveolar processes of the jaws
and the necks of the teeth
The gingiva proper is normally
pink, stippled, and keratinizing.
– The
alveolar
mucosa
(unattached gingiva)
•
59
is normally shiny red and nonkeratinizing.
Gingivae- Clinical Note
Gingivitis
• Improper oral hygiene results in food and bacterial deposits in tooth and gingival
crevices that may cause inflammation of the gingivae (gingivitis).
• The gingivae swell and redden as a result.
• If untreated, the disease spreads to other supporting structures, including alveolar
bone, producing periodontitis (inflammation and destruction of the bone and the
periodontium).
• Dentoalveolar abscesses (collections of pus resulting from death of inflamed tissues)
may drain to the oral cavity and lips.
60
Teeth
Teeth
• Children have 20 deciduous teeth;
• adults normally have 32 permanent teeth .
• The types of teeth are identified by their
characteristics:
– incisors, thin cutting edges;
– canines, single prominent cones;
– premolars (bicuspids), two cusps;
– molars, three or more cusps.
• The vestibular surface (labial or buccal) of each
tooth is directed outwardly, and the lingual
surface is directed inwardly.
61
Teeth, Innervation
62
Teeth
63
Teeth
Parts and Structure of the Teeth
• A tooth has a crown, neck, and root .
• Most of the tooth is composed of dentin ,which
is covered by enamel over the crown and
cement (over the root.
• The pulp cavity contains connective tissue,
blood vessels, and nerves.
• The root canal (pulp canal) transmits the
nerves and vessels to and from the pulp cavity
through the apical foramen.
• Adjacent sockets are separated by interalveolar
septa;
64
Teeth
Vasculature of the Teeth
• The superior and inferior alveolar arteries, branches of the maxillary
artery, supply the maxillary and mandibular teeth, respectively
• Alveolar veins with the same names and distribution accompany the
arteries.
• Lymphatic vessels from the teeth and gingivae pass mainly to the
submandibular lymph node
65
Teeth
Deciduous
Teeth
Eruption
(months)a
Shedding
(years)
66
Central
Incisor Lateral Incisor Canine
6-8
8-10
16-20
6-7
7-8
10-12
1st Molar
12-16
2nd
Molar
20-24
9-11
10-12
Teeth
Permane Central Lateral Canine 1st Premolar
nt Teeth Incisor Incisor
Eruption 7-8
8-9
10-12 10-11
(years)
67
2nd Premolar
11-12
1st
2nd Molar
Molar
6-7
12
3rd
Molar
13-25
Teeth- Clinical Note
Dental Caries, Pulpitis, and Tooth Abscesses
•
Decay of the hard tissues of a tooth results in the formation of dental caries
(cavities). Treatment involves removal of the decayed tissue and restoration
of the anatomy of the tooth with a dental material. Neglected dental caries
eventually invade and inflame tissues in the pulp cavity. Invasion of the pulp
by a deep carious lesion results in infection and irritation of the tissues
(pulpitis). Because the pulp cavity is a rigid space, the swollen tissues cause
considerable pain (toothache). If untreated, the small vessels in the root
canal may die from the pressure of the swollen tissue, and the infected
material may pass through the apical canal and foramen into the
periodontal tissues. An infective process develops and spreads through the
root canal to the alveolar bone, producing an abscess. Pus from an abscess
of a maxillary molar tooth may extend into the nasal cavity or the maxillary
sinus. The roots of the maxillary molar teeth are closely related to the floor
of this sinus. As a consequence, infection of the pulp cavity may also cause
sinusitis or sinusitis may stimulate nerves entering the teeth and simulate a
toothache.
Extraction of the Teeth
•
Sometimes it is not practical to restore a tooth because of extreme tooth
destruction. The only alternative is tooth extraction. A tooth may lose its
blood supply as a result of trauma. The blow to the tooth disrupts the
blood vessels entering and leaving the apical foramen. It is not always
possible to save the tooth. Unerupted 3rd molars are common dental
problems; these teeth are the last to erupt, usually when people are in
their late teens or early 20s. Often there is not enough room for these
68 molars to erupt, and they become lodged (impacted) under or against the
2nd molars .If impacted 3rd molars become painful, they are usually
removed. When doing so, the surgeon takes care not to injure the alveolar