Chapter 176. Dental Anesthesia and Analgesia

Dental anesthesia techniques are used by Emergency Physicians for a variety of intraoral and extraoral conditions. This includes dental caries, jaw fractures, dry sockets, intraoral hemorrhage, laceration repair, and tooth fractures. These techniques are simple to learn, easy to perform, and provide temporary pain relief for the patient. The Emergency Physician can provide pain-free intraoral manipulations, extraoral manipulations, facial manipulations, and simple pain control until the patient receives definitive evaluation and treatment by a Dentist or Oral Surgeon. The fundamental principles of dental anesthesia and anatomy will be discussed so that the Emergency Physician will feel knowledgeable and comfortable performing dental anesthetic techniques.

An understanding of the anatomy of the fifth cranial nerve is essential to performing dental nerve blocks1 (Figure 176-1). The fifth cranial nerve is also referred to as CN V or the trigeminal nerve. It is the largest cranial nerve. It is a mixed cranial nerve containing primarily sensory fibers to the skin of the face and scalp, the nasal cavity, and the oral cavity. The motor fibers innervate the muscles of mastication.

The trigeminal nerve originates in the brainstem as a small motor root and a large sensory root. These roots fuse as they leave the brainstem. The trigeminal nerve travels forward into the middle cranial fossa where it expands into a large and crescent-shaped trigeminal ganglion. The trigeminal ganglion divides to give rise to the three divisions of the trigeminal nerve: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3) (Figure 176-1). Each of these nerves leaves the middle cranial fossa through its own foramen.

Ophthalmic Nerve

The ophthalmic nerve is the smallest branch of the trigeminal nerve. It travels forward in the lateral wall of the cavernous sinus and enters the orbit via the superior orbital fissure. It provides sensory innervation to the forehead, scalp, upper eyelid, cornea, nasal cavity, sinuses, and the orbit. This nerve is not discussed further because it does not innervate any oral or dental structures.

Maxillary Nerve

The maxillary nerve is purely sensory. It travels forward in the lateral wall of the cavernous sinus and exits the cranial vault via the foramen rotundum into the pterygopalatine fossa. It then enters the orbit through the inferior orbital fissure to continue on as the infraorbital nerve and emerge on the face. The infraorbital nerve terminates as a sensory nerve to the lower eyelid, upper cheek, nose, and upper lip. The infraorbital nerve gives off the anterior superior alveolar nerves prior to its termination. These nerves supply the maxillary sinus, the maxillary incisors, the maxillary canine teeth, and the maxillary premolar teeth. The anterior superior alveolar nerve occasionally crosses the midline to supply the contralateral maxillary incisors.

The maxillary nerve forms numerous branches in the pterygopalatine fossa. The zygomaticofacial and zygomaticotemporal nerves are cutaneous to the face and temple. The nasal and nasopalatine nerves supply the nasal cavity and floor of the nasal cavity. The nasopalatine nerve exits the nasal canal through the midline incisive foramen, just posterior to the central incisors. It provides sensory innervation to the anterior hard palate and associated soft tissues. The greater palatine nerve exits the greater palatine foramen to provide sensory innervation to the posterior two-thirds of the hard palate. The lesser palatine nerve exits the lesser palatine foramen and provides sensory innervation to the soft palate. The greater and lesser palatine nerves exit 1 cm medial to the junction of the second and third molar on the hard palate. The middle superior alveolar nerve provides sensory innervation to the premolars, and occasionally the canine and the first molar teeth. The posterior superior alveolar nerve provides sensory innervation to the molars and, occasionally, the premolars.

Mandibular Nerve

The mandibular nerve is the largest division of the trigeminal nerve. It is the only division of the trigeminal nerve to contain motor fibers. The mandibular nerve exits the middle cranial fossa via the foramen ovale. It provides branches to the meninges and the small muscles of the palate and the medial pterygoid muscle. It divides into a small anterior division and a large posterior division.

The anterior division of the mandibular nerve is primarily motor. It innervates the muscles of mastication (i.e., masseter, temporalis, and lateral pterygoid). The sensory portion of the anterior division is the buccal nerve. This nerve travels between the two heads of the lateral pterygoid muscle, under the masseter muscle, and emerges from the anterior border of the masseter muscle. It travels forward to innervate a small and variable portion of the skin of the cheek. It primarily innervates the mucous membranes of the cheek.

The posterior division of the mandibular nerve is purely sensory. It divides into the auriculotemporal, inferior alveolar, and lingual nerves. The auriculotemporal nerve supplies sensory innervation to the skin of the auricle, external auditory canal, scalp, and temporomandibular joint. It conveys postganglionic parasympathetic fibers to the parotid gland.

The lingual nerve descends into the mouth and travels along the lateral surface of the tongue. It supplies sensory innervation to the anterior two-thirds of the tongue and the floor of the mouth. The lingual nerve receives, near its origin, and conveys the chorda tympani from the facial nerve. The chorda tympani provides taste sensation to the anterior two-thirds of the tongue and preganglionic fibers to the submandibular ganglion for the submandibular and sublingual glands.

The inferior alveolar nerve descends immediately posterior and adjacent to the lingual nerve. It enters the upper one-third of the ramus of the mandible, posterior to the lingula, to enter the mandibular canal. It provides sensory innervation to the mandible, the mandibular teeth, and the adjacent mucous membranes. The inferior alveolar nerve gives origin to the mental nerve. The mental nerve exits the mental foramen located on the outer surface of the mandible between the first and second premolars. It supplies sensory innervation to the lower lip, the skin of the chin, and the mucous membrane of the chin.

Dental nerve blocks can be performed to provide temporary relief of pain. They are often used to provide relief from alveolar ridge fractures, dental caries, dry sockets, mandible fractures, and tooth fractures. Nerve blocks can be performed prior to painful intraoral procedures such as incision and drainage of dental abscesses and laceration repair to the cheek, lips, oral mucosa, and tongue. Nerve blocks do not distort the local anatomy, when compared to infiltration of the surrounding soft tissue with local anesthetic solution, and allow better approximation of the wound edges during suturing. Nerve blocks are an excellent alternative if narcotic analgesics are contraindicated or to be avoided. Local anesthetic solutions containing epinephrine can be utilized to provide longer pain relief and vasoconstriction along the nerve distribution (Table 176-1).

The two absolute contraindications to dental anesthesia include a known hypersensitivity to the anesthetic agent and gross distortion of the anatomic landmarks required to perform the nerve block. Other relative contraindications include an uncooperative patient, such as an anxious adult, scared child, or any patient with altered mental status. These patients place themselves and the Emergency Physician at significant risk for injury. It may be most prudent to abort the procedure and perform procedural sedation and analgesia (or general anesthesia in the operating room) to ensure the safety of the patient and the Emergency Physician.

The needle used to inject local anesthetic solution should not traverse infected tissue. Injection of the local anesthetic solution into or through infected tissue is also a relative contraindication. These processes may result in spread of the infection into other adjacent tissues or tissue planes. It is possible to cause bacteremia when injecting into infected tissues. Local anesthetic solutions are less effective when injected into areas of infection or inflammation. An infection that tracks along a nerve and into a bone of the face and/or skull is extremely difficult to treat. Evaluate the risks and benefits of injecting through infected tissue and attempt an alternative method of anesthesia if possible.

• Nonsterile gloves
• Antiseptic mouth rinse, any of the following:
  • Hydrogen peroxide
  • Ethanol (7%) with chlorhexidine (0.5%)
  • Povidone iodine solution
  • 0.12% chlorhexidine or Peridex solution
• 4 × 4 gauze squares
• Cotton-tipped applicators
• Aspirating dental syringe (Figure 176-2)
• Local anesthetic solution (Table 176-1)
• Syringes, 1 and 3 mL
• Suction source and tubing
• Yankauer suction catheter
• Topical anesthetic (e.g., viscous lidocaine, viscous benzocaine, or aerosolized benzocaine)
• Overhead light source or headlamp
• 22 to 27 gauge needles, 2 inches long

The above-listed supplies are required to provide dental anesthesia. They are contained in every Emergency Department. An aspirating dental syringe and anesthetic cartridges, if available, are ideal to perform the nerve blocks (Figure 176-2). Standard 1 to 3 mL syringes armed with a 25 or 27 gauge, 2 inch long needle will work as a substitute. The aspirating dental syringe allows better control of the syringe and the ability to simultaneously aspirate and insert the needle with one hand. This allows the nondominant hand to be used to identify landmarks, retract the cheek or tongue, adjust the light source, and/or use the suction catheter. Many local anesthetic solutions are available in 1.8 mL carpules that fit into the dental aspirating syringe. The carpules are available with the local anesthetic solution, and also with or without a vasoconstrictor (usually epinephrine). A dental or multipositional procedure chair would be preferred to the use of a standard cart or gurney.2,3 Unfortunately, this may not be available in many Emergency Departments.

Numerous injectable agents are available to provide anesthesia (Table 176-1). The most commonly used agents are lidocaine and lidocaine without epinephrine (1:100,000). Longer acting agents are commonly available in the Emergency Department (e.g., bupivacaine and mepivacaine, with and without epinephrine) when a prolonged period of anesthesia is required. Avoid using long-acting local anesthetic agents if the tongue (i.e., inferior alveolar or lingual nerve blocks) or mucosa (i.e., buccal nerve block) is anesthetized, especially in children, to prevent the patient from biting the area and causing injury.

A relatively new device is the Accupal (Accupal, Little Rock, AR). It is an injection preparation tool that prepares the gums before the anesthetic needle is inserted. The Accupal vibrates and produces ultrasonic tissue stimulation to reduce pain sensation at the needle injection site. The Accupal is usually not available in the Emergency Department.

Numerous jet injectors for the delivery of local anesthetic agents are commercially available. These devices inject the local anesthetic solution under pressure and in a fine stream into the soft tissues without the use of a needle. The small volume of injected solution and its superficial penetration into the soft tissues only anesthetizes the soft tissues and not the teeth. Thus, jet injectors cannot be used to anesthetize teeth. They can be used to provide topical anesthesia.

Perform a thorough history and a directed physical examination, dependent on the clinical situation, in any patient undergoing dental anesthesia. Give special attention to the past medical history, past surgical history, current medications, and any history of allergic or adverse reactions to an anesthetic agent. A patient with severe systemic disease may be better served by rescheduling the procedure after appropriate consultation or referral. This will clarify functional reserve and treatment limitations.2,3 Any patient with cardiac valvular disease, congenital heart anomalies, artificial heart valves, or other indications should receive antibiotic prophylaxis to help prevent bacterial endocarditis caused from transient bacteremia. Please refer to Chapter 177 for more complete details of antibiotic prophylaxis.

Explain the procedure, its risks, and benefits to the patient and/or their representative. Obtain an informed consent for the specific technique to be performed. A formal consent may exist depending upon the institution in which one practices. Some physicians desire a formal signed and dated consent form. Other physicians choose to chart: “All the risks, benefits, and complications were described and discussed with the patient. They understood the procedure described and gave verbal consent for the procedure.” This is physician and institution dependent. Place the patient in a well-lighted environment. Reassurance often alleviates a patient's anxiety regarding injections or manipulations and puts them at ease.2

Prepare the mucosa at the injection site. Completely dry the mucosa with gauze squares. Apply an antiseptic solution (e.g., 7% ethyl alcohol (ETOH) with 0.5% chlorhexidine solution, diluted povidone iodine, 0.12% chlorhexidine solution, or hydrogen peroxide) to the working area with a cotton ball or gauze square for 15 seconds. Alternatively, the patient can swish 0.12% chlorhexidine mouth rinse or hydrogen peroxide for 30 seconds and then spit it out.

Apply a topical anesthetic agent (e.g., viscous lidocaine or benzocaine with a cotton-tipped applicator, or 20% benzocaine spray) for added patient comfort. It is not recommended to use TAC (tetracaine, adrenalin, and cocaine) or other topical anesthetic combinations that are used for cutaneous laceration repair on mucosal surfaces. Their use may lead to significant absorption and systemic toxicity.

The general procedure of a dental nerve block will be described. The specific details are contained within each nerve block described below. Identify the anatomic landmarks required to perform the nerve block. Clean the mucous membrane at the injection site with a gauze square. Apply an antiseptic solution. Apply a topical anesthetic and allow it to work for 2 to 3 minutes. Reidentify the anatomic landmarks. Insert a 25 or 27 gauge needle into the appropriate area to deliver the local anesthetic agent. If the patient experiences paresthesias, do not inject the local anesthetic solution. Paresthesias signify that the tip of the needle is within the nerve bundle. Withdraw the needle 1 to 2 mm and allow the paresthesias to resolve. This usually takes 5 to 20 seconds. Inject the local anesthetic solution. Allow up to 10 minutes for the local anesthetic solution to take effect. Some Dentists prefer to apply pressure to the area immediately next to the site of the anesthetic injection with a cotton-tipped applicator. This aids in distracting the patient from the pain of injection. Other Dentists “jiggle” the mucous membrane to and fro rapidly as they simultaneously introduce the needle.2,3

Supraperiosteal Infiltration (Field Block)

This technique is commonly used in dentistry. Excellent anesthesia can be achieved with this technique when it is used to anesthetize a branch of the anterior or middle superior alveolar nerve.3,4 This technique deposits local anesthetic agent against the periosteum of the alveolar ridge adjacent to a tooth (Figure 176-3A). The local anesthetic agent then infiltrates through the periosteum, the cortical plate of the maxilla, and the medullary bone to anesthetize the nerve root as it leaves the apex of the tooth. This technique works best for teeth with associated thin cortical bone. This includes the maxillary incisor, canine, and premolar teeth. The molars of the maxilla in an adult are less likely to be anesthetized with this technique as the cortical bone in which they lie is relatively thick and a poor conduit for the anesthetic. Supraperiosteal infiltration is also a poor technique for anesthesia of mandibular teeth in the adult patient for the same reasons. In children, the cortical bone of the maxillary molars and the mandible is thin and may allow this technique to be effectively utilized to anesthetize a tooth.

Anatomy

The anterior superior alveolar nerve provides sensory innervation to the ipsilateral medial and lateral incisors, canine, and sometimes the first premolar teeth. The middle superior alveolar nerve provides sensory innervation to the ipsilateral premolars, canine, and first molar teeth.

Patient Positioning

Place the patient recumbent in a dental chair with their neck extended 45°. Alternatively, position the patient sitting upright with their back and head firmly set against an examination chair or table.

Landmarks

Use the nondominant hand to grasp and pull the upper lip outward and upward (Figure 176-3B). Identify the mucobuccal fold above the tooth to be anesthetized.3

Needle Insertion and Direction

Clean, prep, and apply a topical anesthetic agent to the mucobuccal fold above the tooth to be anesthetized. Firmly grasp the upper lip. Pull it outward and upward to tighten the tissues and allow a clear identification of the maxillary mucobuccal fold (Figure 176-3B). Insert a 27 gauge needle through the mucobuccal fold over the center of the tooth to be anesthetized (Figure 176-3B). Aim the tip of the needle toward the maxilla. Advance the needle 1.0 to 1.5 cm until it contacts the maxilla (Figure 176-3A). Withdraw the needle 1 mm. Aspirate to confirm that the tip of the needle is not within a blood vessel. Inject 1 to 2 mL of local anesthetic solution.

Remarks

The anesthetic will be deposited in a nonoptimal location if the needle is too deep or too shallow. It may take as long as 10 minutes to achieve anesthesia as the local anesthetic solution diffuses through the cortical bone and to the nerve root. Be careful when using this technique for anesthesia of the incisor or canine teeth because advancing the needle too far may breach the nasal cavity or maxillary sinuses.

Infraorbital Nerve Block

Anatomy

The infraorbital nerve is the terminal branch of the maxillary nerve. It exits the maxilla via the infraorbital foramina and supplies sensation to the ipsilateral upper lip, cheek, lateral nose, and lower eyelid. It may be blocked by either an extraoral or intraoral approach.

Patient Positioning

Place the patient recumbent in a dental chair with their neck extended 30°. Alternatively, position the patient sitting upright with their head and back against an examination chair or table with their neck extended 30°. Instruct the patient to slightly open their mouth.

Landmarks

Identify the infraorbital foramen by palpation. It is located below the infraorbital ridge in the midpupillary line (Figure 176-4). The midpupillary line is a line drawn in the sagittal plane (vertical) through the pupil while the patient is staring straight ahead.

Needle Insertion and Direction (Extraoral Approach)

Identify the infraorbital foramen as above. Clean and prep the skin over the infraorbital foramen. Instruct the patient to close their eyes. Insert a 25 or 27 gauge needle through the skin overlying the infraorbital foramen (Figure 176-5). Advance the needle to just beneath the subcutaneous tissue. Do not enter the infraorbital canal as this may damage the nerve. Aspirate to confirm that the tip of the needle is not within a blood vessel. Inject 1 to 2 mL of local anesthetic solution. Massage the area over the infraorbital foramen for a few seconds to ensure optimal infiltration.

Needle Insertion and Direction (Intraoral Approach)

Clean, prep, and apply a topical anesthetic agent to the mucosa opposite the first maxillary premolar. Place the nondominant index finger over the infraorbital foramen (Figure 176-6). Retract the upper lip using the nondominant thumb. Identify the mucobuccal fold above the first premolar. Insert a 25 or 27 gauge needle through the mucobuccal fold. Advance the needle toward the nondominant index finger situated over the infraorbital foramen (Figure 176-6B). Stop advancing the needle when the tip is felt beneath the index finger. The estimated depth of penetration of the needle tip is 1.0 to 1.5 cm in an older child or an adult and 0.5 to 1.0 cm in a younger child. Aspirate to confirm that the tip of the needle is not within a blood vessel. Inject 1 to 2 mL of local anesthetic solution.

Remarks

Be careful not to penetrate too deeply when performing the intraoral approach. The infraorbital venous plexus may be disrupted and result in a hematoma. The globe may also be accidentally penetrated. Avoid these complications by positioning the nondominant index finger over the infraorbital foramen and using it to palpate and track the advancing needle tip. The intraoral approach is the preferred technique.

Nasopalatine Nerve Block

Anatomy

The nasopalatine nerve provides sensory innervation to the anterior one-third of the hard palate (Figure 176-7A). It exits the maxilla via the incisive foramen in the midline and 0.5 cm posterior to the central incisors.

Patient Positioning

Place the patient recumbent in a dental chair with their head extended 45°. Alternatively, place the patient supine with a rolled sheet beneath their shoulder blades to assist in neck extension. Instruct the patient to fully open their mouth.

Landmarks

The incisive foramen lies in the midline and approximately 5 mm posterior to the central incisors of the maxilla. Overlying the incisive foramen is the incisive papilla, a soft tissue elevation.

Needle Insertion and Direction

Clean, prep, and apply a topical anesthetic agent to the mucosa on the anterior one-third of the hard palate. Identify the incisive foramen by first identifying the incisive papilla. Insert a 27 to 30 gauge needle, with the bevel facing the hard palate, from a position immediately lateral to the edge of the incisive papilla (Figure 176-7B). Advance the needle 3 to 4 mm toward the midline or until bone is identified. Aspirate to confirm that the tip of the needle is not within a blood vessel. Inject 0.25 to 0.35 mL of local anesthetic solution. The area surrounding the injection site will blanch upon deposition of the local anesthetic solution.2,3

Remarks

This is a particularly painful injection due to the adherent nature of the mucosa to the underlying hard palate. Topical anesthetics will provide adequate preinjection anesthesia. Some clinicians use a cotton-tipped applicator or a blunt instrument to put pressure on the incisive papilla for 30 seconds prior to and during the injection.3 This seems to defer the attention of the patient and make the injection more bearable. Be careful not to penetrate too deeply with the needle and enter the incisive foramen. Insertion into the incisive foramen will cause severe pain. Injection into the incisive foramen can result in permanent nerve damage.2,3 The mucosa of the hard palate receives its blood supply from the hard palate. Injection of more than 0.4 mL will elevate the mucosa from the hard palate and result in mucosal necrosis. This block may be performed to repair lacerations of the mucosa of the anterior hard palate.

Greater Palatine Nerve Block

Anatomy

The greater palatine nerve provides sensory innervation to the ipsilateral posterior two-thirds of the hard palate (Figure 176-7A). It enters the oral cavity via the greater palatine foramen. The greater palatine foramen lies between the second and third maxillary molar and approximately 1 cm onto the hard palate.

Patient Positioning

Place the patient recumbent in a dental chair with their head extended 45°. Alternatively, place the patient supine with a rolled sheet beneath their shoulder blades to assist in neck extension. Instruct the patient to fully open their mouth.

Landmarks

The greater palatine foramen lies 1 cm medial to the gingival junction of the second and third maxillary molar (Figure 176-7C).

Needle Insertion and Direction

Clean, prep, and apply a topical anesthetic agent to the hard palate adjacent to the second and third maxillary molars. Insert a 27 to 30 gauge needle 1 cm medial to the junction of the second and third maxillary molars (Figure 176-7C). Ensure that the tip of the needle is held at 90° to the curve of the palate. Aspirate to confirm that the tip of the needle is not within a blood vessel. Inject 0.25 to 0.35 mL of local anesthetic solution. The area surrounding the injection site will blanch upon deposition of the local anesthetic solution.2,3

Remarks

This block may be performed to repair lacerations of the mucosa of the hard palate. The mucosa of the hard palate receives its blood supply from the hard palate. Injection of more than 0.4 mL will elevate the mucosa from the hard palate and result in mucosal necrosis. The position of the lesser palatine foramen is 2 to 4 mm posterior to the greater palatine foramen. The lesser palatine nerve provides sensory innervation to the soft palate and uvula. If anesthetized, as it often is when blocking the greater palatine nerve, the patient may experience a feeling of dysphagia or throat closure. Reassurance is usually adequate to alleviate the patient's anxiety until the anesthesia wears off.

Posterior Superior Alveolar Nerve Block

Anatomy

The maxillary nerve exits the skull via the foramen rotundum. It then courses anteriorly into the pterygopalatine fossa and divides into its constituent branches. The posterior superior alveolar nerve provides sensory innervation to the maxillary molar teeth and their associated mucosal tissues.

Patient Positioning

Place the patient semirecumbent in a dental chair with their head extended 30°. Alternatively, place the patient sitting upright with their head and back firmly against the examination chair or table and their head extended 30° to 45°. Instruct the patient to fully open their mouth.

Landmarks

Pull the buccal mucosa laterally and identify the inferior-most posterior portion of the zygoma. It lies posterior, lateral, and superior to the third maxillary molar. The pterygomaxillary fissure lies posterior, medial, and superior to the vestibule between the third maxillary molar and the posterior zygoma. The pterygopalatine fossa can be reached by following the pterygomaxillary fissure superiorly and medially.2,3

Needle Insertion and Direction

Clean, prep, and apply a topical anesthetic agent to the recess posterior and lateral to the maxilla. Insert the nondominant index finger between the maxillary molars and the cheek (Figure 176-8A). Palpate the zygomatic process of the maxilla with the index finger. Rotate the index finger 180° so that the pad is against the patient's cheek (Figure 176-8B). Apply outward pressure to move the cheek away from the teeth. Place the needle along the middle of the nail plate of the index finger. Aim the needle and syringe along the index finger (Figure 176-8B). The needle and syringe should be aimed posteriorly, superiorly, and medially (Figure 176-8C). Insert and advance the needle 2.5 cm along the index finger. If the needle contacts bone, withdraw the needle completely and direct it more laterally.2,3 Aspirate to confirm that the tip of the needle is not within a blood vessel. Inject 3 mL of local anesthetic solution.

Remarks

Bend the needle 30° at the hub to assist in achieving a medial direction of the needle. Do not bend the needle more than 30° as the needle may fracture. It is extremely important to never change the direction of a needle once it is inserted. This is associated with an increased risk of needle breakage requiring an operative procedure to recover the needle segment. Never force the needle. The needle is inappropriately positioned if it is meeting resistance. Abort the procedure, reidentify the landmarks, and reattempt the procedure.2,3 Occasionally, the first molar is only partially anesthetized by this block. Consider supplementation of this block with a supraperiosteal infiltration of the first molar.

Mental Nerve Block, Intraoral Approach

Anatomy

The mental nerve is one of the two terminal divisions of the inferior alveolar nerve. It provides sensory innervation to the ipsilateral skin and mucosa of the lower lip and chin. It exits the bony mandible at the mental foramen.

Patient Positioning

Place the patient recumbent in a dental chair. Alternatively, place the patient sitting upright or supine with their head against the examination table and in the neutral position. Instruct the patient to slightly open their mouth.

Landmarks

The mental foramen lies in the same plane as the infraorbital foramen and the midpupillary line (Figure 176-4). The mental foramen is located approximately 1 cm beneath the gum line, between the first and second premolar.

Needle Insertion and Direction

Clean, prep, and apply a topical anesthetic agent to the oral mucosa overlying the mental foramen. Grasp the lower lip with the nondominant hand. Pull it outward and downward (Figure 176-9). Insert a 27 gauge needle into the mucobuccal fold between the first and second premolar (Figure 176-9). Advance the needle medially until it contacts the mandible. Aspirate to confirm that the tip of the needle is not within a blood vessel. Inject 1.5 to 2.0 mL of local anesthetic solution.

Remarks

The mental nerve block, as the infraorbital nerve block, has an intraoral and an extraoral approach. The extraoral approach will not be discussed as it is more painful and there is no benefit to its use over the intraoral approach. A description of the extraoral approach to the mental nerve block is found in Chapter 126. A near midline lower lip or chin injury may necessitate bilateral mental nerve blockade due to the midline crossover from each of the mental nerves.2

Buccal Nerve Block

Anatomy

The buccal nerve is one of the main branches of the mandibular nerve. It travels down the medial aspect of the ramus of the mandible, anterior to the inferior alveolar neurovascular bundle. It crosses from the medial mandible into the soft tissue of the cheek at the level of the occlusive plane. It supplies the sensory innervation to the mucous membrane of the cheek and vestibule.1 It innervates, to a variable degree, a small patch of skin over the cheek.

Patient Positioning

Place the patient recumbent in a dental chair with their head extended 30°. Alternatively, place the patient sitting with their head and back firmly against an examination chair or upright table with their head extended 30° to 45°. Instruct the patient to fully open their mouth.

Landmarks

Visually identify the third mandibular molar. Palpate the anterior border of the ramus of the mandible. The buccal nerve traverses the anterior border of the ramus of the mandible, posterior and slightly lateral to the third molar at the level of the occlusive plane.

Needle Insertion and Direction

Clean, prep, and apply a topical anesthetic agent to the oral mucosa over the anterolateral border of the ramus of the mandible. Place the thumb of the nondominant hand on the inner surface of the cheek. Pull the cheek outward. Insert a 27 gauge needle 1 mm lateral to the anterior border of the ramus of the mandible and at the level of the occlusal plane (Figure 176-10). Advance the needle 3 to 4 mm into the soft tissues. Aspirate to confirm that the tip of the needle is not within a blood vessel. Inject 2 mL of local anesthetic solution.

Remarks

Buccal nerve blocks are used when extensive intraoral manipulation is anticipated, when buccal manipulation or repair is required, or for the incision and drainage of an abscess. It provides additional patient comfort. The block is nearly always performed as an adjunct to an inferior alveolar, maxillary, or posterior superior alveolar nerve block.3

Inferior Alveolar Nerve Block

Anatomy

The lingual and inferior alveolar nerves are two of four branches of the mandibular nerve. The nerves initially travel together and inferiorly on the medial side of the mandibular ramus (Figure 176-11A). The lingula is a palpable bony landmark immediately anterior to the mandibular foramen. The inferior alveolar nerve courses posterior to the lingula and enters the mandibular canal via the mandibular foramen. It continues to travel anteriorly within the mandible to provide sensory innervation to the body of the mandible, the mandibular teeth, and the overlying oral mucosa. One of the terminal branches of the inferior alveolar nerve is the mental nerve. The inferior alveolar nerve may be blocked by the classic, open-mouth approach or the closed-mouth approach.

Patient Positioning

Place the patient in a dental chair with their head neutral, such that the occlusive surface is parallel to the floor. Alternatively, place the patient sitting upright in an examination chair or on a gurney with their head positioned firmly against the back of the gurney or chair. Instruct the patient to fully open their mouth. Perform the open-mouth approach if the patient can fully open their mouth. Perform the closed-mouth approach if the patient has trismus or cannot fully open their mouth.

Landmarks

Identify by palpation the anterior border of the ramus of the mandible within the mouth, the coronoid notch within the mouth, and the posterior border of the ramus of the mandible externally (Figure 176-11B). Approximately equidistant from these two points lie the lingual and the inferior alveolar nerves. Palpate the lingula of the ramus of the mandible. It is a bony projection on the medial surface of the ramus of the mandible and 1 cm above the occlusive plane.

Needle Insertion and Direction (Open-Mouth Approach)

Clean, prep, and apply a topical anesthetic agent to the inner surface of the ramus of the mandible. Stand opposite the side to be blocked. Place the thumb of the nondominant hand on the anterior border of the ramus of the mandible. Move the thumb posteromedially to identify the lingula. Place the index finger of the nondominant hand against the extraoral border of the mandibular ramus, just above the angle of the mandible. Grasp the ramus between the thumb and the forefinger (Figure 176-11C). Pull the cheek outward using the nondominant thumb as a lever. Place a 27 gauge, 2 inch needle on a 3 mL syringe that contains local anesthetic solution. A 5 mL syringe is too large for this approach. A syringe smaller than 3 mL will not carry enough anesthetic.

Introduce the needle from the opposite side (Figure 176-11D). Align the tip of the needle toward the lingula with the barrel of the syringe between the contralateral first and second premolars (Figure 176-11D). Hold the syringe parallel to the occlusal plane and 3 to 4 mm above the premolars. Insert the needle into the oral mucosa just superior and posterior to the lingula. Advance the needle until the tip contacts the ramus of the mandible. Aspirate to confirm that the tip of the needle is not within a blood vessel. Inject 2 mL of local anesthetic solution.

The above technique is optimal if the operator is right-handed and a right-sided inferior alveolar block is attempted. If the operator is right-handed and attempting a left-sided inferior alveolar nerve block, it is still necessary to stand opposite the side to be anesthetized with the syringe in the dominant hand. Place the nondominant arm over and around the patient's head so that the thumb of the nondominant hand can contact the anterior border of the mandibular ramus and the index finger can grasp the posterior border above the angle of the mandible. The remainder of the technique is the same.

Needle Insertion and Direction (Closed-Mouth Approach)

This method can be used when the patient cannot fully open their mouth due to an abscess, edema, mandible fractures, trismus, or if the mandible is wired-closed to the maxilla. This approach deposits the local anesthetic solution superior to the site of the classic, open-mouth approach. The local anesthetic solution will descend, due to gravity, to bathe the inferior alveolar nerve and provide adequate anesthesia.

Place the nondominant thumb on the inner surface of the cheek. Pull the cheek outward. Place a 27 gauge needle on a 3 mL syringe that contains local anesthetic solution. Place the needle and syringe parallel to the occlusal plane and aligned along the junction of the maxillary molars and their gingiva (Figure 176-11E). Direct the needle just medial to the ramus of the mandible (Figures 176-11E & F). Advance the needle 3 cm through the mucosa. Aspirate to confirm that the tip of the needle is not within a blood vessel. Inject 2 mL of local anesthetic solution.

Remarks

It is crucial that the tip of the needle contacts the mandible in the open-mouth approach. The needle is usually advanced 0.5 to 1 cm before the mandible is encountered. The needle is most likely inappropriately placed and deposition of anesthesia will not produce the desired results if the mandible is not encountered. Remove the needle, reidentify the appropriate anatomic landmarks, and reattempt the procedure if the mandible is not encountered. The buccal, inferior alveolar, and lingual nerves must be blocked on one side to achieve complete anesthesia of the hemimandible. Facial nerve paralysis can occur if the needle is inserted too far posterior and enters the capsule of the parotid gland. This paralysis is usually transient and resolves as the anesthetic wears off.

Lingual Nerve Block

Anatomy

The lingual nerve is a branch of the mandibular division of the trigeminal nerve. It travels with the inferior alveolar nerve until the inferior alveolar nerve enters the mandible. The lingual nerve leaves the medial aspect of the mandibular ramus and penetrates the posterior tongue at the level of the occlusive plane, just medial to the third mandibular premolar. It courses anteriorly to provide sensory innervation to the anterior two-thirds of the tongue, the floor of the mouth, and the lingual mucous membrane.1

Patient Positioning

Place the patient in a dental chair with their head neutral, such that the occlusive surface is parallel to the floor. Alternatively, place the patient sitting upright in an examination chair or on a gurney with their head firmly against the back of the gurney or chair. Instruct the patient to fully open their mouth.

Landmarks

Identify the lingual side of the second mandibular molar. The injection site is 1 cm medial to the second mandibular molar.

Needle Insertion and Direction

Approach the patient from the contralateral side. Move the tongue upward or toward the contralateral side with a tongue blade. Insert a 27 gauge, 2 inch needle into the mucosa 1 cm medial to the second mandibular premolar (Figure 176-12). Advance the needle posteriorly 1 cm. Aspirate to confirm that the tip of the needle is not within a blood vessel. Inject 1.0 to 1.5 mL of local anesthetic solution.

Remarks

The inferior alveolar nerve and the lingual nerve can be, and usually are, blocked simultaneously during an inferior alveolar nerve block. The lingual nerve, however, can be blocked in an isolated fashion. Perform an isolated lingual nerve block only when the initial combined block has failed or for isolated tongue lacerations.1,3 This is an optimal block for tongue laceration repair. However, bilateral lingual nerve blocks may be necessary.

Anesthesia is usually achieved within 5 minutes of the injection. However, depending upon the particular injection and the local anesthetic used, anesthesia can be achieved anywhere from 20 seconds to 10 minutes. The block was properly performed if the patient experiences anesthesia. Repeat the block if anesthesia is not achieved by 10 minutes.

The aftercare of dental anesthesia is minimal. Reexamine the area of the local anesthetic injection before the patient is discharged to ensure that a hematoma has not developed. Instruct the patient to use caution as there is no sensation in the area anesthetized. Encourage them to refrain from meals, chewing gum, hot beverages, aggravated scratching, placing foreign bodies in the mouth, or anything that may cause injury to the anesthetized area. Parents must be informed to discourage children from testing the anesthetized area by biting or chewing. Many Dentists and Physicians place a cotton roll, or rolled 2 × 2 gauze, between the area anesthetized and the teeth to provide added protection from a self-inflicted bite injury.2,3

Any patient receiving dental anesthesia has the potential to develop complications. The key is to have knowledge of these complications and be prepared to deal with them should they occur. Most severe complications will declare themselves in a rapid fashion. These severe complications include intravascular injection of local anesthetic, allergic reactions to the local anesthetic, cardiovascular toxicity, neurologic toxicity, seizures, and unintentional overdosage. Allergic reactions can occur from the latex vial/carpule seal or the preservative in the local anesthetic.5 These complications can be avoided by aspiration before injection, obtaining an appropriate history of prior anesthesia, and cautious calculation of anesthetic dosages, respectively.2–4

Late complications of dental anesthesia include hematomas, neuropathy, infection, and trismus.2,3 Hematomas after dental anesthesia occur after the inadvertent puncture of an artery or vein. Arterial hematomas enlarge more rapidly and are usually more painful than venous hematomas. They can cause a significant facial deformity. Hematomas following dental anesthesia are usually of little significance, require no intervention, and resolve spontaneously with time. A proper preprocedural history should determine if the patient is using anticoagulants or blood thinners, has a real or potential bleeding disorder, or had adverse bleeding complications from previous procedures. Treatment initially involves applying cold packs. Heat in the form of an externally placed heating pad should be used to help disintegrate the clot after 24 hours.2,3

A peripheral neuropathy can occur in the form of prolonged anesthesia, paresthesias (burning or itching sensation), hyperesthesias (increased sensitivity to noxious stimuli), and dysesthesias (painful sensation to non-noxious stimuli). This may be a result of direct damage to the nerve from traumatic needle insertion, hemorrhage or hematoma within the nerve sheath, deposition of local anesthetic into a foramen or canal causing pressure injury to the nerve, or chemical injury to the nerve.6,7 Reduce the risk of causing a neuropathy by avoiding injections into a foramen, using a small gauge needle, and withdrawing the needle slightly before injection if the patient should feel a shock or paresthesias with needle insertion.2,3 While many nerve injuries are temporary and will resolve with time, some can be permanent.7

Infection due to dental anesthesia is rare, but does exist. Follow several simple measures to minimize potential infections. Never inject through an infected area. Doing so may carry bacteria through facial planes into deeper compartments. Refrain from multiple injections (needle misadventures) as this increases the risk of iatrogenic infection. This is easily resolved by appropriately identifying the anatomic landmarks prior to needle insertion.

Needle breakage can occur as a result of manufacturing defects or operator imprudence. To prevent needle breakage, never exert force against resistance. Resistance signifies that the tip of the needle is against bone or a tooth. Withdraw the needle and reattempt insertion if this occurs. Never advance the needle to the hub. The greatest percentage of needle breaks occur when the needle is inserted to the hub.2,3 Never redirect the needle after it is inserted through the skin or mucosa. This puts abnormal force on the needle and potentiates breakage. The needle may inadvertently be in an undesired anatomic location. Withdraw the needle completely, identify the appropriate anatomic landmarks, and reinsert the needle. Do not bend the needle as this can weaken it and make it more prone to breakage. If a needle breaks, grasp the fragment with a forceps or hemostat and remove it from the soft tissue. If the needle fragment is not palpable with an instrument, consult a Dentist or Oral Surgeon for possible removal. The consultant may choose to see the patient in the Emergency Department, see the patient in their office within 24 to 48 hours, or leave the needle fragment in place and not remove it.

Dental anesthetic techniques are easy to learn, simple to perform, and effective in providing temporary pain relief. The required equipment is readily available in every Emergency Department. Consider using local anesthetic agents that contain epinephrine because they provide significantly longer analgesia than those without epinephrine. A rapidly performed local anesthetic injection goes a long way toward patient satisfaction.