The middle superior alveolar nerve is a nerve that drops from the infraorbital portion of the maxillary nerve to supply the , the roots of the maxillary premolars, and the of the first maxillary molar.It is not always present; in 72% of cases it is non existent with the anterior superior alveolar nerve innervating the premolars and the posterior superior alveolar nerve innervating the molars, including the mesiobuccal root of the first molar.