1 . 2 The largest of all the cranial nerves Motor & sensory roots Motor root originating in the motor nucleus.

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Kaan Yücel M.D., Ph.D.

23.November.2011 Wednesday

http://yeditepedentistryanatomy.wordpress.com

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TRIGEMINAL NERVEThe 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-pain-temperature 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.

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1- Ophthalmic 2- Maxillary3- Mandibular4- Great auricular C35- 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.

Trigeminal Ganglion (Semilunar ganglion)

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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.

OPHTHALMIC NERVE (CN V1)

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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.

MAXILLARY NERVE (CN V2)

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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.

MAXILLARY NERVE (CN V2)

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MANDIBULAR NERVE (CN V3)

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.

MANDIBULAR NERVE (CN V3)

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THE ANATOMY OF TRIGEMINAL ANESTHESIA

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.

ANESTHESIA OF THE MAXILLARY TEETH

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Techniques of Maxillary Regional AnesthesiaThe 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.

ANESTHESIA OF THE MAXILLARY TEETH

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POSTERIOR SUPERIOR ALVEOLAR (PSA) NERVE BLOCK

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.

POSTERIOR SUPERIOR ALVEOLAR (PSA) NERVE BLOCK

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MIDDLE SUPERIOR ALVEOLAR (MSA) NERVE BLOCK

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 height of mucobuccal fold in area of lateral incisor and canine. The mucobuccal fold over the maxillary first premolar is another suggested site for injection.

ANTERIOR SUPERIOR ALVEOLAR (ASA) NERVE BLOCK

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In order to anesthetically block the anterior and middle superior alveolar nerves, it is essential to localize the infraorbital foramen which, when reached with a needle, permits the diffusion of the anesthetic solution through the infraorbital canal.

ANTERIOR SUPERIOR ALVEOLAR (ASA) NERVE BLOCK

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INFRAORBITAL(ASA) NERVE BLOCK

The area of insertion is height of mucobuccal fold in area of lateral incisor and canine.

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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.

ANTERIOR SUPERIOR ALVEOLAR (ASA) NERVE BLOCK

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ANTERIOR SUPERIOR ALVEOLAR (ASA) NERVE BLOCK

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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Insert the needle over the first premolar toward the infraorbital foramen. The needle should be held parallel with the long axis of the tooth. Advance the needle toward the upper rim of the infraorbital foramen beneath the tip of the index.

ANTERIOR SUPERIOR ALVEOLAR (ASA) NERVE BLOCK

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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.

ANTERIOR SUPERIOR ALVEOLAR (ASA) NERVE BLOCK

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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.

PALATAL INNERVATION

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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

NASOPALATINE NERVE BLOCK

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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.

GREATER PALATINE NERVE BLOCK

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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.

GREATER PALATINE NERVE BLOCK

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GREATER PALATINE NERVE BLOCK

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.

ANESTHESIA OF THE 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.

ANESTHESIA OF THE MANDIBULAR TEETH

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The most common approach to inferior alveolar anesthesia is the traditional Halstead method.

INFERIOR ALVEOLAR NERVE BLOCK

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).

INFERIOR ALVEOLAR NERVE BLOCK

Injection in proper area of ramus to effect alveolar nerve block

Identifying mandibular ramus

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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.

INFERIOR ALVEOLAR NERVE BLOCK

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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.

INFERIOR ALVEOLAR NERVE BLOCK

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INFERIOR ALVEOLAR NERVE BLOCK

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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.

GOW-GATES MANDIBULAR NERVE BLOCK

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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.

AKINOSI-VAZIRANI CLOSED-MOUTH MANDIBULAR NERVE BLOCK

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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.

LINGUAL NERVE BLOCK

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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.

BUCCAL NERVE BLOCK

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The area of injection mucobuccal fold at or anterior to the mental foramen. This lies between the mandibular premolars.

MENTAL NERVE BLOCK

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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MENTAL NERVE BLOCK

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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.

LEGAL COMPLAINTS

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Nerve to block Technique / Area of insertion

Posterior Superior Alveolar

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

Middle Superior Alveolar The height of the mucobuccal fold above the maxillary 2nd premolar

Anterior Superior Alveolar The height of the mucobuccal fold above the maxillary 1st premolar

Nasopalatine The area immediately lateral to the incisive papilla into incisive foramen

Greater Palatine 1 cm. medial to the junction of the 2nd and 3rd molar

Inferior Alveolar 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.

Buccal 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.

Mental The mucobuccal fold at or anterior to the mental foramen which lies between the mandibular premolars

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References