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ORAL SURGERY
Lec.4
Third
grade
Dr. Noor Sahban
Local anesthesia techniques
Anatomic Considerations in relation to local anesthesia:
Trigeminal Nerve
The management of pain in dentistry requires thorough knowledge of the fifth (V)
cranial nerve. It provides, among other functions, an overwhelming majority of
sensory innervations from teeth, bone, and soft tissues of the oral cavity.
The trigeminal nerve is the largest of the twelve cranial nerves. It is composed of a
small motor root and a considerably larger sensory root. The motor root supplies
the muscles of mastication and other muscles in the region. The three branches of
the sensory root supply the skin of the entire face and the mucous membrane of
the cranial viscera and oral cavity, except for the pharynx and base of the tongue.
Motor Root:
The motor root of the trigeminal nerve arises separately from the sensory root,
originating in the motor nucleus within the pons and medulla oblongata. Its fibers,
forming a small nerve root, travel anteriorly along with, but entirely separate from,
the larger sensory root to the region of the gasserian ganglion. At the ganglion, the
motor root passes in a lateral and inferior direction under the ganglion toward the
foramen ovale, through which it leaves the middle cranial fossa along with the
third division of the sensory root (the mandibular nerve). Just after leaving the
skull, the motor root unites with the sensory root of the mandibular division to
form a single nerve trunk.
Motor fibers of the trigeminal nerve supply the following muscles:
1.
2.
3.
4.
5.
Masticatory muscles: Masseter, Temporalis, medial and lateral Pterygoid.
Mylohyoid.
Anterior belly of the digastrics.
Tensor tympani.
Tensor palatine.
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Sensory Root:
Sensory root fibers of the trigeminal nerve constitute the central processes of
ganglion cells located in the trigeminal gasserian ganglion. Two ganglia are
present, one innervating each side of the face. They are located in Meckel's cavity,
on the anterior surface of the petrous portion of the temporal bone.
The three sensory divisions of the trigeminal nerve are:
Ophthalmic Division (V1)
It is the first branch of the trigeminal nerve. It is purely sensory and is the smallest
of the three divisions. It leaves the cranium and enters the orbit through the
superior orbital fissure. Just before the ophthalmic nerve passes through the
superior orbital fissure, it divides into its three main branches: nasociliary, frontal,
and lacrimal nerves.
It supplies the eyeball, conjunctiva, lacrimal gland, parts of the mucous membrane
of the nose and paranasal sinuses, and the skin of the forehead, eyelids, and nose.
Maxillary Division (V2):
The maxillary division of the trigeminal nerve arises from the middle of the
trigeminal ganglion. It passes horizontally forward, leaving the cranium through
the foramen rotundum. The foramen rotundum is located in the greater wing of the
sphenoid bone.
Once outside the cranium, the maxillary nerve crosses the uppermost part of the
pterygopalatine fossa (between the pterygoid plates of the sphenoid bone and the
palatine bone). As it crosses the pterygopalatine fossa, it gives off branches to the
sphenopalatine ganglion, the posterior superior alveolar nerve, and the zygomatic
branches.
Then it enters the orbit through the inferior orbital fissure. Within the orbit, it
occupies the infraorbital groove and becomes the infraorbital nerve, which courses
anteriorly into the infraorbital canal. The maxillary division emerges on the
anterior surface of the face through the infraorbital foramen, where it divides into
its terminal branches, supplying the skin of the face, nose, lower eyelid, and upper
lip.
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Branches:
The maxillary division gives branches in four regions:
Branch within the Cranium:
The middle meningeal nerve travels with the middle meningeal artery to provide
sensory innervations to the dura mater.
Branches in the Pterygopalatine Fossa:
1. The zygomatic nerve: enters the orbit through the inferior orbital fissure,
where it divides into the zygomaticotemporal (supplying sensory
innervations to the skin on the side of the forehead) and zygomaticofacial
nerves (supplying the skin on the prominence of the cheek).
2. The pterygopalatine nerves (ganglionic branches): are two short trunks
that unite in the pterygopalatine ganglion and are then redistributed into
several branches. They serve as a communication between the
pterygopalatine ganglion and the maxillary nerve (V2).
Branches of the pterygopalatine nerves include those that supply four areas:
orbit, nose, palate, and pharynx.
a. The orbital branches: supply the periosteum of the orbit.
b. The nasal branches: supply the mucous membranes of the superior
and middle conchae, the lining of the posterior ethmoidal sinuses, and
the posterior portion of the nasal septum. One branch is significant in
dentistry, the nasopalatine nerve, which passes across the roof of the
nasal cavity downward and forward, where it lies between the mucous
membrane and the periosteum of the nasal septum. The nasopalatine
nerve continues downward, reaching the floor of the nasal cavity and
giving branches to the anterior part of the nasal septum and the floor of
the nose. It then enters the incisive canal, through which it passes into
the oral cavity via the incisive foramen, located in the midline of the
palate about 1 cm posterior to the maxillary central incisors. The right
and left nasopalatine nerves emerge together through this foramen and
provide sensation to the palatal mucosa in the region of the premaxilla
(canines through central incisors).
c. The palatine branches (fig.1): include the greater palatine nerve and
the lesser palatine nerves. The greater palatine nerve descends through
the pterygopalatine canal, emerging on the hard palate through the
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greater palatine foramen (which is usually located about 1 cm toward the
palatal midline, just distal to the second molar). It passes anteriorly
between the mucoperiosteum and the osseous hard palate, supplying
sensory innervation to the palatal soft tissues and bone as far anterior as
the first premolar, where it communicates with terminal fibers of the
nasopalatine nerve. It also provides sensory innervation to some parts of
the soft palate. The lesser palatine nerve emerges from the lesser palatine
foramen. It provides sensory innervation to the mucous membrane of the
soft palate.
d. The pharyngeal branch: is a small nerve that provides innervations to
the mucous membrane of the nasal part of the pharynx.
(Fig. 1: Blood and sensory nerve supply to hard and soft palate)
3. The posterior superior alveolar (PSA) nerve: descends from the main
trunk of the maxillary division in the pterygopalatine fossa just before the
maxillary division enters the infraorbital canal. Commonly there are two
PSA branches, but on occasion a single trunk arises. Passing downward
through the pterygopalatine fossa, they reach the posterior surface of the
maxilla. When two trunks are present, one remains external to the bone,
along the posterior surface of the maxilla to provide sensory innervations to
the buccal gingiva in the maxillary molar region and adjacent facial mucosal
surfaces, whereas the other branch enters into the maxilla (along with a
branch of the internal maxillary artery) through the PSA canal to travel
down the posterior or postero-lateral wall of the maxillary sinus, providing
sensory innervations to the mucous membrane of the sinus. Continuing
downward, this second branch of the PSA nerve provides sensory
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innervations to the alveoli, periodontal ligaments, and pulpal tissues of the
maxillary third, second, and first molars (with the exception of the
mesiobuccal root of the first molar).
Branches in the Infraorbital Canal:
Within the infraorbital canal, the maxillary division (V2) gives off two branches of
significance in dentistry: the middle superior and anterior superior alveolar nerves.
While in the infraorbital groove and canal, the maxillary division is known as the
infraorbital nerve.
1. The middle superior alveolar (MSA) nerve: branches off the main nerve
trunk (V2) within the infraorbital canal. It provides sensory innervations to
the two maxillary premolars and to the mesiobuccal root of the first molar
and periodontal tissues, buccal soft tissue, and bone in the premolar region.
Sometimes the MSA nerve is absent, in this case its usual innervations are
provided by either the PSA or the anterior superior alveolar (ASA) nerve
but most frequently ASA.
2. The anterior superior alveolar (ASA) nerve: a relatively large branch is
given off the infraorbital nerve (V2) before it exits from the infraorbital
foramen. Descending within the anterior wall of the maxillary sinus, it
provides pulpal innervation to the central and lateral incisors and the canine,
and sensory innervation to the periodontal tissues, buccal bone, and mucous
membranes of these teeth.
(Fig. 2: Lateral view of the skull (a portion of the lateral wall of the orbit has
been removed) with the branches of the maxillary nerve highlighted)
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Note:
The actual innervations of individual roots of all teeth, bone, and periodontal
structures in both the maxilla and the mandible derived from terminal branches of
larger nerves in the region. These nerve networks are termed the dental plexus.
The superior dental plexus is composed of smaller nerve fibers from the three
superior alveolar nerves.
Three types of nerves emerge from these plexuses (each is accompanied along its
pathway by a corresponding artery):
a. Dental nerves: they enter the tooth through the apical foramen, dividing into
many small branches within the pulp. Pulpal innervations of all teeth is
derived from dental nerves. Although in most instances one easily
identifiable nerve is responsible, in some cases (usually the maxillary first
molar) more than one nerve is responsible.
b. Interdental branches (also termed perforating branches): travel through the
entire height of the interradicular septum, providing sensory innervations to
the periodontal ligaments of adjacent teeth through the alveolar bone. They
emerge at the height of the crest of the interalveolar septum and enter the
gingiva to innervate the interdental papillae and the buccal gingiva.
c. Interradicular branches: it traverses the entire height of the interradicular
or interalveolar septum, providing sensory innervations to the periodontal
ligaments of adjacent roots. They terminate in the periodontal ligament
(PDL) at the root furcations.
Branches on the Face:
The infraorbital nerve emerges through the infraorbital foramen onto the face to
divide into its terminal branches:
1. The inferior palpebral branches: supply the skin of the lower eyelid with
sensory innervations.
2. The external nasal branches: provide sensory innervations to the skin on
the lateral aspect of the nose.
3. The superior labial branches: provide sensory innervations to the skin and
mucous membranes of the upper lip.
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Mandibular Division (V3) (fig.3):
The mandibular division is the largest branch of the trigeminal nerve. It is a mixed
nerve with two roots: a large sensory root and a smaller motor root. The two roots
emerge from the cranium separately through the foramen ovale. They unite just
outside the skull and form the main trunk of the third division. This trunk remains
undivided for only 2 to 3 mm before it splits into a small anterior and a large
posterior division.
Branches:
Branches from the main nerve trunk:
1. Nervus spinosus (meningeal branch of the mandibular nerve): it reenters
the cranium through the foramen spinosum along with the middle
meningeal artery to supply the dura mater and mastoid air cells.
2. Medial pterygoid nerve: it is a motor nerve to the medial pterygoid
muscle. It gives off small branches that are motor to the tensor veli palatini
and the tensor tympani.
Branches from the Anterior Division:
The anterior division of the mandibular nerve is primarily motor with a small
sensory component. Its branches provide motor innervations to the muscles of
mastication and sensory innervations to the mucous membrane of the cheek and
the buccal mucous membrane of the mandibular molars.
Motor branches:
1. Deep temporal nerves: supplying the temporalis muscle.
2. Masseter nerve: supplying the masseter muscle.
3. Lateral pterygoid nerve: supplying the lateral pterygoid muscle.
Sensory branch:
The buccal (long buccal) it passes between the two heads of the lateral pterygoid
to reach the external surface of that muscle. It then emerges under the anterior
border of the masseter muscle. At the level of the occlusal plane of the mandibular
third or second molar, it crosses in front of the anterior border of the ramus and
enters the cheek through the buccinator muscle. Some sensory fibers are
distributed to the skin of the cheek; while others pass into the retromolar triangle,
providing sensory innervations to the buccal gingiva of the mandibular molars and
the mucobuccal fold in that region.
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Note: The buccal nerve does not innervate the buccinator muscle; the facial nerve
does.
Branches of the Posterior Division:
The posterior division of mandibular nerve is primarily sensory with a small motor
component.
1. Auriculotemporal nerve: it provides sensory innervations to
auriculotemporal area.
2. Lingual nerve: it passes downward medial to the lateral pterygoid muscle
and, as it descends, lies between the ramus and the medial pterygoid muscle
in the pterygomandibular space. It runs anterior and medial to the inferior
alveolar nerve, whose path it parallels. It then continues downward and
forward, deep to the pterygomandibular raphe and below the attachment of
the superior constrictor of the pharynx, to reach the side of the base of the
tongue slightly below and behind the mandibular third molar. Here it lies
just below the mucous membrane in the lateral lingual sulcus. It then
proceeds anteriorly across the muscles of the tongue, looping downward and
medial to the submandibular duct to the deep surface of the sublingual
gland, where it breaks up into its terminal branches. The lingual nerve
provides sensory innervations to the anterior two thirds of the tongue (both
general sensation and taste sensation through the chorda tympani -a branch
of the facial nerve-). In addition, the lingual nerve provides sensory
innervations to the mucous membranes of the floor of the mouth and the
gingiva on the lingual of the mandible.
3. The inferior alveolar nerve (IA) is the largest branch of the mandibular
division. It descends medial to the lateral pterygoid muscle and
lateroposterior to the lingual nerve, to the region between the
sphenomandibular ligament and the medial surface of the mandibular
ramus, where it enters the mandibular canal at the level of the mandibular
foramen. Throughout its path, it is accompanied by the inferior alveolar
artery (a branch of the internal maxillary artery) and the inferior alveolar
vein. The artery lies just anterior to the nerve. The nerve, artery, and vein
travel anteriorly in the mandibular canal as far forward as the mental
foramen, where the nerve divides into its terminal branches: the incisive
nerve and the mental nerve. The IA nerve provided pulpal innervations of
the posterior teeth. The incisive nerve remains within the mandibular canal
and forms a nerve plexus that innervates the pulpal tissues of the
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mandibular first premolar, canine, and incisors via the dental branches. The
mental nerve exits the canal through the mental foramen and divides into
three branches that innervate the skin of the chin and the skin and mucous
membrane of the lower lip and labial gingival.
4. Mylohyoid nerve: branches from the inferior alveolar nerve before entry of
IA nerve into the mandibular canal. It provides motor innervations to the
mylohyoid muscle and the anterior belly of the digastric.
(Fig.3: Medial view of the mandible with the motor and sensory branches of
the mandibular nerve highlighted)
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Methods of administration of local anesthesia
1. Topical anesthesia:
It is obtained by the application of a suitable anesthetic agent to an area of either
skin or mucous membrane which it penetrates to anesthetize superficial nerve
ending. It is commonly used to obtain anesthesia of mucosa prior to injection.
There are several types:
a. Sprays: containing an appropriate local anesthetic agent that particularly
suitable for this purpose because of their rapidity in action. The active
ingredient is 10% lidocaine hydrochlorid. The onset time of anesthesia is
approximately 1 minute and the duration about 10 minutes.
b. Ointment: containing 5% lidocaine hydrochloride but the time of onset is 34 minutes to produce surface anesthesia.
c. Emulsion: containing 2% lidocaine hydrochloride. This is of value when
full mouth impressions are to be taken in patients who are having gagging
reflex.
d. Ethyl chloride spray: It produces anesthesia by refrigeration. When sprayed
onto either mucous membrane or skin, it gets volatilized rapidly, and
produces rapid anesthesia. This phenomenon is of clinical value when the
spray is directed over a limited area until "snow" appears. Care must be
taken to avoid stimulation of the pulps of the adjacent teeth. This technique
occasionally used to produce surface anesthesia prior to the incision of
fluctuating abscesses.
2. Infiltration anesthesia:
In this method the anesthetic solution deposited near the terminal fibers of any
nerve, it will infiltrate through the tissues to reach the nerve fibers and thus
produce anesthesia of the localized area served by them, this technique is
subdivided into:
A. Sub-mucous injection: in this technique the local anesthetic solution is
deposited just beneath the mucous membrane. This technique is unlikely to
produce anesthesia of the dental pulp, it is often employed to anesthetize the
long buccal nerve prior to the extraction of mandibular molars or for soft
tissue surgery.
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B. Supra-periosteal injection: in some sites, such as the maxilla, the outer
cortical plate of alveolar bone is thin and perforated by tiny vascular canals.
In these areas when the anesthetic solution is deposited outside the
periosteum, it will infiltrate through the periosteum, cortical plate and
medullary bone to reach the nerve fibers. By this means, anesthesia of the
dental pulp can be obtained by injection alongside the approximate position
of the tooth apex. The supra-periosteal injection is the most frequently used
technique for obtaining anesthesia in dentistry.
C. Sub-periosteal injection: in this technique, the solution is deposited between
the periosteum and the cortical plate. This technique is painful since the
periosteum is firmly bond to the cortical plate.
3. Regional (block) anesthesia:
In this technique, the anesthetic solution is deposited near the nerve trunk and
this will lead to blocking all impulses and produce anesthesia of the area supplied
by that nerve. Although this technique may be used in the maxilla, it is of
particular value in dentistry for producing anesthesia in the mandible. Due to the
density of the outer cortical plate of the mandible (especially the posterior area)
the use of infiltration technique is unreliable, by placing the anesthetic solution in
the pterygomandibular space near the mandibular foramen; regional anesthesia
over the whole distribution of the inferior alveolar nerve on that side is obtained.
4. Other injection techniques:
A. Intra- ligamentous (periodontal ligament) injection:
This technique introduces a small amount of local anesthetic solution
directly into the periodontal space. The force required for this
technique is quite substantial, so specialized syringes is available to
achieve this. In oral surgery this technique is most frequently used if pain
is still felt despite the use of correct techniques (infiltration or block),
this can occur in teeth with acute pulpitis or apical infection. It may be
also of value if limitation of mouth opening makes inferior alveolar
block injection difficult or impossible.
B. Intra-osseous injection:
In this technique, the solution is deposited within the medullary bone.
The procedure is carried out by drilling a hole in the outer cortical plate
using a specialized of bone drill and the introducing a needle especially
designed for this purpose and inject the solution. In practice, the
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effectiveness of the anesthetic solution available has reduced
considerably the need for this technique and it is rarely used.
C. Intra-pulpal injection:
It is direct deposition of the solution inside the pulp chamber. This
technique is used when pain control is required for pulp extirpation in
the absence of adequate anesthesia from other techniques or even during
extraction when the tooth remains painful on manipulation which is a
feature of some pulpal or apical infections.
Local anesthesia in the upper jaw (maxilla)
Infiltration anesthesia of the upper anterior teeth:
The upper central, lateral and canine teeth and labial supporting tissue and the
mucoperiosteum attached to them are innervated via anterior superior alveolar
nerve.
 Technique (fig.4):
In this technique we deposit the anesthetic solution to the nerve ending of the
anterior superior alveolar nerve to anesthetize the specific target tooth as follows:
1. Hold the syringe parallel or at 45° angle to the long axis of the tooth.
2. The bevel of the needle should be facing the bone, insert the needle into the
height of mucobuccal fold over the target tooth.
3. Advance the needle for few millimeters.
4. Inject slowly.
5. Slowly withdraw the syringe and re-sheath the needle.
(Fig.4: Infiltration “supraperiosteal” injection—the position of the point of
the needle is above the periosteum)
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Infiltration anesthesia of the upper premolar teeth:
The mesio-buccal root of the upper 1st molar, both premolars and the buccal
supporting tissue and the mucoperiosteum attached to them are innervated via
middle superior alveolar nerve.
 Technique:
This technique is usually employed to anesthetize these teeth (same procedure
mentioned above).
Infiltration anesthesia of the upper molar teeth:
The pulp of the upper 3rd , 2nd and 1st molars with the exception of the mesiobuccal root of the 1st molar are innervated by the posterior superior alveolar nerve
which is also responsible for innervations of the buccal gingiva in the molar region
and the mucoperiosteum attached to them.
 Technique:
This technique is usually employed to anesthetize these teeth (same procedure
mentioned above).
Block anesthesia of the upper anterior and premolar teeth:
Infra-orbital block injection:
This technique is based upon the fact that the anesthetic solution is deposited at
the orifice of the infra-orbital foramen passes along the canal to involve both the
anterior and the middle superior alveolar nerves thus producing anesthesia of the
incisors, canine, premolar teeth and the supporting structures.
This technique is rarely used since the infiltration techniques are so effective in the
maxilla, however it may have value when:
1. Multiple extractions or extensive surgery are to be undertaken in the
maxillary incisor, canine and premolar regions.
2. The use of infiltration technique is precluded by the presence of infection in
the site of injection.
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This technique could be achieved either by an intra oral or extra oral approach.
Intra oral approach (fig.5):
1. The infra-orbital margin is palpated and the infra-orbital notch is located
with the tip of the index finger.
2. The index finger is moved slightly downward to lie directly over the infraorbital foramen.
3. The finger tip maintained in that position and the thumb is used to reflect
the upper lip and expose the site of injection.
4. The tip of a long needle is inserted into the mucous membrane over the apex
of the second premolar.
5. The needle should be held parallel with the long axis of the tooth as it is
advanced to avoid premature contact with bone to a depth of 1.5-2 cm then
the anesthetic solution is deposited.
6. Withdraw the syringe slowly and re-sheath the needle.
(Fig.5: Infraorbital nerve block. The position of the needle is in the vicinity of
infraorbital foramen)
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Extra oral approach:
This technique include direct injection through the skin to the foramen
1. The infra-orbital margin is palpated.
2. The eye of the patient should be closed and protected by the fingers of the
free hand with the thumb palpating the infra-orbital margin.
3. The site of injection is 1 cm below the midpoint of the infra-orbital margin,
inject the solution slowly.
4. Carefully withdraw the syringe and re-sheath the needle.
Block anesthesia of the upper molar teeth:
Posterior superior alveolar nerve block:
In this technique we have local anesthesia by blocking the posterior superior
alveolar nerve by the deposition of the anesthetic solution close to the nerve trunk
of the posterior superior alveolar just after it leaves its bony canal. Partially open
the patient's mouth.
 Technique (fig.6):
1. Retract the patient's cheek with your finger (for visibility).
2. Insert the needle into the height of the mucobuccal fold over the second
molar.
3. Advance the needle slowly in an upward, inward, and backward direction in
one movement (not three).
4. Slowly advance the needle through soft tissue to the desired depth (in
adults, penetration to a depth of 1.5 cm places the needle tip in the
immediate vicinity of the foramina through which the nerve enter the
posterior surface of the maxilla).
5. Deposit 1-1.8 ml of the anesthetic solution.
6. Slowly withdraw the syringe and re-sheath the needle.
One disadvantage of this technique is the possibility of damaging the pterygoid
venous plexus.
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(Fig.6: Posterior superior alveolar nerve block. The position of the point of
the needle is in relation to the posterior superior)
Anesthesia of the palatal tissue:
Anesthesia of the hard palate is necessary for dental procedures involving
manipulation of palatal soft or hard tissues (like extraction of a tooth). The palatal
mucoperiosteum is firm in consistency and closely adapted to the bone. These
features make it necessary to inject local anesthetic solution under greater pressure
than is required in other sites, for this reason the patient should be informed prior
to injection that palatal injection cause some discomfort or pain. This can be
minimized by inserting the needle with the bevel facing the bone and at right angel
to the vault of the palate. Palatal anesthesia can be achieved by:
 Infiltration technique:
A. Infiltration to the nasopalatine nerve (for extraction of anterior teeth): the
solution is deposited in the palatal tissue just next to the target tooth.
B. Infiltration to the greater palatine nerve (fig.7) (for extraction of posterior
teeth): the solution is deposited in the palatal tissue about half way between
the midline and the gingival margin of the target tooth.
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X
(Fig.7: Infiltration to the greater palatine nerve)
 Block technique:
A. Block of the nasopalatine nerve (fig.8): produce anesthesia of the
anterior portion of the hard palate, the solution is deposited near the
incisive foramen which is located in the midline of the palate about 1 cm
posterior to the maxillary central incisors.
(Fig.8: Nasopalatine nerve block. The position of the point of the needle is in
the incisive papilla)
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B. Block of the greater palatine nerve (fig.9): produce anesthesia of the
posterior portion of the hard palate, the solution is deposited near the
greater palatine foramen which is located distal to the maxillary second
molar about 1 cm toward the midline.
(Fig.9: Greater palatine nerve block. The position of the point of the needle is
in relation to the greater palatine neurovascular bundle)
Anesthesia of the upper deciduous teeth:
In children, multiple vascular canals perforate the thin labial, buccal alveolar plate,
for this reason infiltration techniques are highly effective in producing anesthesia
of upper deciduous teeth. Care should be taken to avoid the misjudging the length
of the roots and inserting the needle too deeply into the tissue.
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