The second division of the trigeminal nerve, maxillary branch, exits
the skull through the foramen rotundum, passes the pterygomaxillar fossa,
enters the infraorbital canal, becomes the infraorbital nerve, and runs
along the orbital floor (Figure 18–14). In other words, the
infraorbital nerve is an extension of the maxillary nerve as it reaches the
infraorbital fossa. The nerve emerges at the anterior side of the maxilla
through the infraorbital foramen, ending in three terminal branches: lateral
nasal, superior labial, and inferior palpebral (see Figure 18–13). About 5
to 6 mm before the foramen, the infraorbital nerve supplies the anterior
maxillary alveolar nerve, whose branches descend by narrow canals in the
maxilla, running between the sinus mucosa and the bony wall, penetrating
through the radicular apices, to innervate the pulp of maxillary incisors
and canines. Its branches also go to the outer bone plate, periosteum, and
other lining structures in the region of these teeth.
The middle superior alveolar nerve leaves the infraorbital nerve at the
posterior part of the floor of the infraorbital canal and continues in a
downward frontal direction until the premolar apices. At other times, it
separates near the infraorbital foramen and descends by the anterior wall or
the anterolateral maxillary sinus until the superior premolars, innervating
the dental pulp, the external alveolar lamina, the periosteum and the
mucosa.