Which tooth group is NOT typically anesthetized by an MSA nerve block?

• A. Premolars
• B. Canine
• C. MB root of first molar
• D. Buccal bone over premolars

Answer: (B)

The MSA block targets the middle superior alveolar nerve, a branch of the infraorbital nerve that supplies the maxillary premolars and often the mesiobuccal root of the first maxillary molar, along with the surrounding buccal bone and gingiva. The canine, however, is primarily innervated by the anterior superior alveolar nerve, not the middle superior alveolar nerve. Because the MSA block does not reliably reach the canine’s innervation, the canine is not typically anesthetized by this block. The buccal bone over the premolars is included in the anesthesia because the buccal periosteum and gingiva of those teeth receive sensory supply from the same regional nerves targeted by the block.