Slayt 1 - Yeditepe University Dentistry Anatomy

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The largest of all the cranial nerves
Motor & sensory roots
Motor root originating in the motor nucleus within the pons and
medulla oblongata, and sensory root in the anterior aspect of the
pons.
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Sensory nerve for the face and the motor nerve for the muscles of
mastication and several small muscles.
The sensory portion of the trigeminal supplies touch-paintemperature to the face.
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The trigeminal nerve [V] divides into three major divisions before
leaving the middle cranial fossa. :
Ophthalmic nerve[V1]
Maxillary nerve[V2]
Mandibular nerve [V3]
These nerves are named according to their main areas of termination:
the eye, maxilla, and mandible, respectively.
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Each of these divisions passes out of the cranial cavity to innervate a
part of the face, so most of the skin covering the face is innervated by
branches of the trigeminal nerve [V].
The exception is a small area covering the angle and lower border of
the ramus of mandible and parts of the ear, which are innervated by the
trigeminal [V], facial [VII], vagus [X], and cervical nerves.
1- Ophthalmic
2- Maxillary
3- Mandibular
4- Great auricular C3
5- Lesser occipital C2
6- Other branches of the cervical plexus
.
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Crescent-shaped
Situiated within an invaginated pocket of dura in the middle cranial
fossa.
Lies near the apex of the petrous temporal bone.
Represents the first cell station for all sensory fibres of the trigeminal
nerve except those subserving proprioception.
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Superior division of the trigeminal nerve
Smallest of the three divisions of CN V.
Exits the skull through the superior orbital fissure and enters the
orbit.
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Intermediate division of the trigeminal nerve
Arises as a wholly sensory nerve.
Supplies upper lip, lateral and posterior portions of nose, upper
cheek, anterior temple, mucosa of nose, upper jaw, upper teeth, roof of
mouth, and dura of part of the middle cranial fossa.
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Passes anteriorly from the trigeminal ganglion and leaves the cranium
through the foramen rotundum in the base of the greater wing of the
sphenoid.
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Inferior and largest division of the trigeminal nerve.
Exits the skull through the foramen ovale.
Supplies lower lip, chin, posterior cheek, temple, external ear, mucosa
of lower part of mouth, anterior two-thirds of the tongue, and portions
of the dura of anterior and middle cranial fossae.
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The only division of CN V that carries motor fibers.
The major cutaneous branches of CN V3
Auriculotemporal, buccal, and mental nerves.
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The local infiltration technique anesthetizes the terminal nerve
endings of the dental plexus.
The field block anesthetizes the terminal nerve branches in the area
of treatment.
A nerve block anesthetizes the main branch of a specific nerve
allowing treatment to be performed in the region innervated by the
nerve.
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 The most commonly anesthetized nerves in dentistry are branches or
nerve trunks associated with the maxillary and mandibular divisions
of the trigeminal nerve.
 Dentists are aware of the relative ease of successfully performing
pain-free intraoperative procedures in maxillary teeth. The maxilla’s
relatively porous alveolar bone allows for the use of straightforward
local anesthetic techniques of paraperiosteal field blocks or
infiltrations.
 The mandible is different. The outer layer of cortical bone is thick and
nonporous and thus normally requires the use of a nerve block at a
site away from the teeth being treated.
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From an anatomical perspective, maxillary injections generally are
believed to be not only more predictable than mandibular injections,
but also more benign and associated with fewer complications.
However, this is not necessarily true, particularly for block injections.
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Techniques of Maxillary Regional Anesthesia
The techniques most commonly employed in maxillary anesthesia
include
• Supraperiosteal (local) infiltration
• Periodontal ligament (intraligamentary) injection
• Posterior superior alveolar nerve block
• Middle superior alveolar nerve block
• Anterior superior alveolar nerve block
• Greater palatine nerve block
• Nasopalatine nerve block
• Local infiltration of the palate
• Intrapulpal injection
Of less clinical application are the maxillary nerve block and intraseptal
injection.
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Maxillary nerve block (V2 block) can be used to anesthetize maxillary
teeth, alveolus, hard and soft tissue on the palate, gingiva, and skin of
the lower eyelid, lateral aspect of nose, cheek, and upper lip skin and
mucosa on side blocked.
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The PSA nerve block is used to
anesthetize the pulpal tissue,
corresponding alveolar bone, and
buccal gingival tissue to the
maxillary 1st, 2nd, and 3rd molars.
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The area of insertion is the height of mucobuccal fold between 1st
and 2nd nd molar.
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 Useful for procedures where the maxillary premolar teeth or the
mesiobuccal root of the 1st molar require anesthesia.
 Although not always present, it is useful if the PSA or ASA nerve
blocks or supraperiosteal infiltration fails to achieve adequate
anesthesia. Present in about 28% of the population.
The height of the mucobuccal fold
above the maxillary 2nd premolar is
the injection site.
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The ASA nerve block is used to anesthetize the maxillary
canine, lateral incisor, central incisor, alveolus, and buccal gingiva.
The area of insertion is where the mucobuccal fold intersects with
the apex of the canine.
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Two approaches
Intraoral
The mucosa opposite the upper second bicuspid, approximately 0.5 cm
from the buccal surface
Extraoral
Infraorbital foramen
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The anatomical location of this foramen has been studied
by numerous authors. Martani and Stefani (1965), studying the
position of this anatomic accident within statistical, morphological
and topographical aspects, provide an extensive bibliographical
review of this topic.
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In adults, the infraorbital foramen lies significantly below the
infraorbital rim (8 to 10 millimeters), a safe distance from the
cavity of the orbit.
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To locate the infraorbital foramen, the dentist can palpate a small
depression in the infraorbital rim—the infraorbital notch—created by
the zygomaticomaxillary suture.
Place your in this notch, and direct the needle through the vestibular
mucosa over the first premolar tooth and toward the finger.
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The mucosa of the hard palate and the palatal gingiva
are supplied by the nasopalatine and greater palatine nerves.
The boundary between the areas innervated by the two nerves
corresponds roughly to a line drawn between the maxillary
canines; however, the two areas are not so sharply delineated
as such animaginary line might suggest.
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The nasopalatine nerve block can be used to anesthetize the soft and
hard tissue of the maxillary anterior palate from canine to canine.
The area of insertion is immediately lateral to the incisive papilla into
incisive foramen to completely anesthetize the central incisors
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In the greater palatine canal technique, the area of insertion is greater
palatine canal. The target area is the maxillary nerve in the
pterygopalatine fossa.
The dentist performs a greater
palatine block and waits 3 3-5 mins.
Then h/she inserts needle
in previous area and walks
into greater palatine foramen.
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The foramen has been shown to lie 1.9 mm in front of the posterior
border of the hard palate and 15 mm from the palatal midline. These
measurements are useful for more easily locating the greater palatine
foramen and enhancing the anesthetic injection technique in the
posterior palate.
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The greater palatine foramen can be located by on the palatal tissue
approximately one centimeter medial to the junction of the 2nd and
3rd molar. While this is the usual position for the foramen, it may be
located slightly anterior or posterior to this location.
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The buccal cortical plate of the mandible most often is sufficiently dense
to preclude effective infiltration anesthesia in its vicinity. The infiltration
techniques do not work in the adult mandible due to the dense cortical
bone.
Therefore, the dentist must rely on block anesthesia for effectively
anesthetizing mandibular teeth.
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Nerve blocks are utilized to anesthetize the inferior alveolar, lingual, and
buccal nerves.
It provides anesthesia to the pulpal, alveolar, lingual and buccal gingival
tissue, and skin of lower lip and medial aspect of chin on side injected.
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The most common approach to inferior alveolar anesthesia is the
traditional Halstead method.
Inferior alveolar nerve is approached in the pterygomandibular space,
called the infratemporal fossa, via an intraoral route located just
before the nerve enters the mandibular foramen.
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The area of insertion is the mucous membrane on the medial border of
the mandibular ramus at the intersection of a horizontal line (height of
injection) and vertical line (anteroposterior plane).
Identifying mandibular ramus
Injection in proper area of ramus to effect
alveolar nerve block
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As the target site for the deposition of anesthetic solution in the
conventional inferior alveolar block injection, the mandibular foramen
is an essential structure to accurately locate.
The technique involves blocking the inferior alveolar nerve prior to entry
into the mandibular lingula on the medial aspect of the mandibular
ramus.
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During administration of anesthetic to the inferior alveolar nerve, the
clinician must be aware of the proximal extremity of the maxillary
artery, as well as the course of the inferior alveolar artery.
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Traditionally, the inferior alveolar nerve block (IANB), also known
as the “standard mandibular nerve block” or the “Halsted block,”
has a success rate of only 80 to 85 percent, with reports of even
lower rates.
Investigators have described other techniques as alternatives to
the traditional approach, of which the Gow-Gates mandibular
nerve block and Akinosi-Vazirani closed-mouth mandibular nerve
block techniques have proven to be reliable.
Dentists who know how to perform all three techniques increase
their probability of providing successful mandibular anesthesia in
any patient.
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The primary goal of each of the three mandibular nerve blocks is
anesthesia of the inferior alveolar nerve, which innervates the pulps of
the mandibular teeth on the same side of the mouth, as well as the
buccal periodontium anterior to the mental foramen.
For each of the three techniques, this goal is accomplished by
depositing anesthetic within the pterygomandibular space.
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Described by Gow-Gates in 1973.
The objective of the technique
To place the needle tip and administer the local anesthetic at the neck
of the condyle.
This position is in proximity to the mandibular branch of the trigeminal
nerve after it exits the foramen ovale.
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Described as an alternative to the IANB in 1977.
What makes this technique unique is that the patient’s mouth is
closed.
The objective is to place the needle tip between the ramus and the
medial pterygoid muscle.
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Branches of the lingual nerve supply the lingual gingiva and adjacent
mucosa of the mandible.
The lingual nerve courses through the infratemporal fossa anterior to
the inferior alveolar nerve.
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Traditionally, the buccal nerve block injection is delivered to the anterior
ramus of the mandible at the level of the mandibular molar occlusal
plane in the vicinity of the retromolar fossa.
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The area of injection mucobuccal fold at or anterior to the mental
foramen. This lies between the mandibular premolars.
The position of this foramen varies greatly, making it difficult to
predictably locate this nerve using intraoral landmarks in a patient
with an intact dentition.
Penetrate the mucous membrane at the injection site, at the canine or first premolar,
directing the syringe backward and downward transversally toward the mental
foramen. Advance the needle until the foramen is reached.
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Most local anaesthesia 'failures' occur with IAN blocks.
Injuries to inferior alveolar and lingual nerves are caused by local
analgesia block injections and have an estimated injury incidence of
between 1:26,762 to 1/800,000.
The nerve that is usually damaged during inferior alveolar nerve
block injections is the lingual nerve. which accounts for 70% of nerve
injuries.
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Nerve to block
Technique / Area of insertion
Posterior Superior
Alveolar
Infraorbital
The height of the mucobuccal fold over the maxilalry 2nd molar
Middle Superior Alveolar
Intraoral approach.
The mucosa opposite the upper second bicuspid, approximately 0.5
cm from the buccal surface
Extraoral approach
Infraorbital foramen
The height of the mucobuccal fold above the maxillary 2nd premolar
Anterior Superior Alveolar Where the mucobuccal fold intersects with the apex of the canine
Nasopalatine
Greater Palatine
Inferior Alveolar
Buccal
Mental
The area immediately lateral to the incisive papilla into incisive
foramen
1 cm. medial to the junction of the 2nd and 3rd molar
With the mouth open maximally, identify the coronoid notch and the
pterygomandibular raphae. Three quarters of the anteroposterior
distance between these two landmarks, and approximately six to ten
millimeters above the occlusal plane is the injection site.
The dentist should identify the most distal molar tooth on the side to
be treated. The tissue just distal and buccal to the last molar tooth is
the target area for injection.
The mucobuccal fold at or anterior to the mental foramen which
lies
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between the mandibular premolars
• Bahl R. Local anesthesia in dentistry. Anesth Prog. 2004;51(4):138-42.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2007495/pdf/anesthprog00004-0030.pdf
• Trigeminal nerve injuries related to local anaesthesia in dentistry.
http://blogohj.oralhealthjournal.com/2011/06/trigeminal-nerve-injuries-related-to-local-anaesthesia-in-dentistry.html
• Local Anesthesia Techniques in Oral and Maxillofacial Surgery, Sean M. Healy, D.D.S., October 2004
http://www.utmb.edu/otoref/grnds/Anesth-mouth-0410/Anesth-mouth.pdf
• New Anatomic Intraoral Reference for the Anesthetic Blocking of the Anterior and Middle Maxillary Alveolar Nerves (Infraorbital Block)
http://www.forp.usp.br/bdj/t0411.html
• Benaifer D. Dubash, DMD; Adam T. Hershkin, DMD; Paul J. Seider, DMD; Gregory M. Casey, DMD. Oral and Maxillofacial Regional Anesthesia
http://www.nysora.com/peripheral_nerve_blocks/head_and_neck_block/3062-oral_maxillofacial_regional_anesthesia.html
• Maxillary Injection Techniques
• http://www.iusb.edu/~sbdental/Local%20Anesthesia/Maxillary%20Injection%20Techniques.ppt
• Haas DA. Alternative mandibular nerve block techniques: a review of the Gow-Gates and Akinosi-Vazirani closed-mouth mandibular nerve
block techniques. J Am Dent Assoc. 2011 Sep;142 Suppl 3:8S-12S.
• Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 61. Cranial Nerve V:
The Trigeminal Nerve. Authors Walker HK. Editors In: Walker HK, Hall WD, Hurst JW, editors. 1990, Butterworth Publishers, a division of Reed
Publishing.
• Boynes SG, Echeverria Z, Abdulwahab M. Ocular complications associated with local anesthesia administration in dentistry. Dent Clin North
Am. 2010 Oct;54(4):677-86.
• Arasho B, Sandu N, Spiriev T, Prabhakar H, Schaller B. Management of the trigeminocardiac reflex: facts and own experience. Neurol India.
2009 Jul-Aug;57(4):375-80.
• Blanton PL, Jeske AH; ADA Council on Scientific Affairs; ADA Division of Science. The key to profound local anesthesia: neuroanatomy. J Am
Dent Assoc. 2003 Jun;134(6):753-60.
• Richard L. Drake, A. Wayne Vogl, Adam W. M. Mitchell. Gray’s Anatomy for Students, Second Edition, Churchill Livingstone Publications, 2009.
• Richard S. Snell, Clinical Anatomy by Regions, 8 edition, Lipott Wims W-ins, 2007.
• Keith L. Moore, Arthur F. Dalley, Anne M.R. Agurquot, Clinically Oriented Anatomy, 6th International Edition, Lippincott Williams Wilkins, 2009.
• Harold Ellis. Clinical Anatomy. A revision and applied anatomy for clinical students.10th edition, Blackwell Publishing, 2002.
 Infraorbital nerve block
http://emedicine.medscape.com/article/82660-overview
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