Posterior superior alveolar nerve
The posterior superior alveolar nerve, also known as the posterior superior dental nerve, is the first branch of the infra-orbital nerve, from the maxillary division of the trigeminal nerve. It is the first of the superior alveolar nerves and contributes to the superior dental plexus.
It arises from the infra-orbital nerve in the pterygopalatine fossa just before it enters the inferior orbital fissure, and descends into the pterygomaxillary fissure. From here it or several individual branches enter the maxilla via alveolar canals. Terminal dental branches enter the apical foramina at the dental roots.
The nerves supply the maxillary sinus, posterior maxillary oral mucosa and the maxillary molar teeth apart from the mesiobuccal root of the first maxillary molar tooth, which is supplied by the middle superior alveolar nerve.
When the middle superior alveolar nerve is absent, the posterior superior alveolar nerve will supply all the molars and premolars.