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The nerves that are anesthetized are the anterior superior alveolar, middle superior alveolar, and the infraorbital nerve (inferior palpebral, lateral nasal, and superior labial).  The areas that are anesthetized are the pulps of the maxillary central incisor through the canine on the injected side, along with the labial periodontium and bone of the corresponding teeth.  In about 72% of patients, the pulps of the maxillary premolars and mesiobuccal root of the first molar may also be anesthetized.  The lower eyelid, lateral aspect of the nose, and the upper lip is also anesthetized with this block.

The anterior superior alveolar (ASA) nerve block is used in place of multiple supraperiosteal injections in the maxillary anterior region due to the smaller volume of local anesthetic solution being deposited to achieve equivalent anesthesia.  Many dentists avoid this nerve block due to fear of injuring the patient's eye.  Fortunately, there have been no confirmed cases of this sort of injury.  Following the proper protocols produce a high success rate with minimal complications and adverse side effects.  

Proper technique:

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  1. 25 or 27-gauge short needle is recommended 

  2. Area of insertion: height of mucobuccal fold between the maxillary lateral and canine 

  3. Target area: infraorbital foramen (where the ASA nerve exits), located below the infraorbital notch

  4. Landmarks

    • Mucobuccal fold​

    • Infraorbital notch

    • Infraorbital foramen

  5. Orientation of the bevel: toward bone

Procedures:

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  1. Correct patient & clinician positioning

    • Right/Left ASA, right-handed clinician sit at 10:00 facing patient or facing in the same direction of the patient/ left-handed clinician sit at 2:00 facing patient or facing in the same direction of the patient

    • Position patient supine or semisupine with neck extended slightly (to avoid clear patient's chest interfering with the syringe barrel)

  2. Prepare tissue at the injection site

    • Dry with gauze or blow air with air/water syringe​

    • Apply topical anesthetic for minimum of 1 minute

  3. Retract the lip, pulling the tissues in the mucobuccal fold taut and increasing visibility

    • Using a gauze aids in retraction​

  4. Insert needle into height of mucobuccal fold between the maxillary lateral and canine with the bevel facing bone (1/4 of the needle)

  5. Orient syringe toward infraorbital foramen 

    • Needle should be held parallel with long axis of tooth as it is advanced ​

    • Advance needle slowly until bone is gently contacted

  6. Aspirate in two planes

  7. Slowly deposit 0.9-1.2mL of anesthetic solution (1/2 to 2/3 cartridge) approximately 30-40 seconds 

  8. Slowly withdraw needle and safely recap

  9. Wait 3-5 minutes before starting dental procedure​

A N T E R I O R   S U P E R I O R   A L V E O L A R  ( A S A )

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