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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. 2

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-pain temperature to the face. 3

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. 4

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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 5

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. 6

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. 7

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. 9

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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. 11

The only division of CN V that carries motor fibers.

The major cutaneous branches of CN V 3 Auriculotemporal, buccal, and mental nerves . 12

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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. 16

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. 18

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. 19

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 23

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. 24

In adults, the

infraorbital foramen

lies significantly below the infraorbital rim (8 to 10 millimeters), a safe distance from the cavity of the orbit. 25

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. 26

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. 27

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 28

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. 34

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 is an essential structure to accurately locate.

mandibular foramen

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. 43

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. 44

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

Posterior Superior Alveolar Infraorbital Middle Superior Alveolar

Technique / Area of insertion

The height of the mucobuccal fold over the maxilalry 2nd molar 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 49