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Mandibular Anesthesia
The success rates for mandibular anesthesia are significantly lower than with maxillary anesthesia. The bone is more dense around the mandibular apecies, which inhibits the diffusion of the anesthetic. The anatomical variations from patient to patient can make a textbook-perfect injection ineffective.
Inferior Alveolar Nerve Block
The inferior alveolar nerve block is the most commonly used injection in mandibular anesthesia. It provides anesthesia to the mandibular teeth to the midline on the side injected as well as the body of the mandible, the buccal mucosa and bone of the teeth anterior to the mandibular first molar, the anterior two thirds of the tongue and floor of the mouth, and the mucosa and bone lingual to the mandibular teeth on the side of injection. Use a 25 gauge long needle. A 27 or 30 gauge needle tends to be deflected or bent by the tissues and the anesthetic may end up being deposited off target. Patients have not demonstrated an ability to differentiate between a 25 or 30 gauge needle.
The tissue should be penetrated at the medial border of the mandibular ramus at the height of the coronoid notch at the pterygomandibular raphe. The puncture point should be about 1.5 cm above the mandibular occlusal plane with the bevel toward the bone. The barrel of the needle should be parallel with the occlusal plane of the mandibular molars, and come across the premolars of the opposite quadrant.  Approximate the posterior border of the ramus by observing the most distal area of the pterygomandibular raphe as it turns up toward the palate. The needle insertion point is on the line of the coronoid notch and about three-fourths the distance from the ramal border. The needle should be advanced slowly, depositing a few drops of anesthetic and aspirating, until bone is contacted. Usually in an adult patient, the needle will be inserted 20 to 25 mm (about 2/3 the length of the needle). The anesthetic will be delivered directly above the mandibular foramen. If the bone is contacted at 1/2 needle depth or less, withdraw slightly and reposition the barrel of the needle over the canine or lateral incisor of the opposite quadrant. If bone is not contacted the needle is too far posterior and the barrel should be repositioned over the first molar of the opposite quadrant. After bone has been contacted, withdraw the needle 1 mm and aspirate. If negative, slowly deposit 1/4 cartridge and reaspirate. If still negative, continue the process of slow deposition and aspiration until 1.5 ml of anesthetic has been delivered to the site. Withdraw the needle to about 1/2 of its length and reaspirate. If negative, deposit the remainder of the anesthetic in the cartridge for the lingual nerve.
The most common problems leading to failure in achieving anesthesia of the inferior alveolar nerve include:
Problem
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Suggestion
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| Anesthetic is deposited below the mandibular foramen. |
Reinject at a higher site. |
| Anesthetic is deposited too far anteriorly on the ramus. |
Reinject with the needle tip more posterior. |
| Needle deflected by tissue, anesthetic deposited to the left or right of the foramen. |
Use a 25 gauge long needle. |
| Anesthetic doesn't reach the nerve. |
Use and anesthetic without vasoconstrictor for second injection to allow for diffusion. Remember, this anesthetic effect will not last as long. |
| There may be accessory nerves supplying the mandibular teeth. |
Reinject distal lingual to the tooth not anesthetized at the lingual border of the mandible or use a periodontal ligament injection. |
Buccal Nerve Block
The buccal nerve is not anesthetized by an inferior alveolar nerve block. This nerve innervates the tissues and periosteum buccal to the molars, so if these soft tissues are involved in treatment, the buccal nerve should be injected as well.  The additional injection is unnecessary when treating only the teeth. A 25 gauge long needle is recommended (because the injection usually follows an inferior alveolar nerve block, so the same needle can be used after more anesthetic is loaded). The needle is inserted in the mucous membrane distal buccal to the last
molar with the bevel of the needle facing towards the bone after the tissue has been prepared with antiseptic and topical. If tissues are pulled taut, the injection is more comfortable for the patient. Insert the needle to 2 to 4 mm to gently contact bone, and aspirate. If negative, slowly deposit about 1/8 of the solution in the cartridge.
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Technique
