Superior Alveolar Arteries
The posterior superior alveolar artery branches from the maxillary artery superior to the maxillary tuberosity to enter the alveolar canals along with the posterior superior alveolar nerves and supplies the maxillary teeth, alveolar bone, and membrane of the sinus. A branch of variable size runs forward on the periosteum at the junction of the alveolar process and maxillary body supplying the gingiva, alveolar mucosa, and cheek. When it is large, it may supplant in part the buccal artery.
A middle superior alveolar branch is usually given off by the infraorbital continuation of the maxillary artery somewhere along the infraorbital groove or canal. It runs downward between the sinus mucosa and bone or in canals in the bone and joins the posterior and anterior alveolar vessels. Its main distribution is to the maxillary premolar teeth.
Anterior superior alveolar branches arise from the infraorbital artery just before this vessel leaves its foramen. They course down the anterior aspect of the maxilla in bony canals to supply the maxillary anterior teeth and their supporting tissues and to join the middle and posterior superior alveolar branches in completing an anastomotic plexus.
Branches to the teeth, periodontal ligament, and bone are derived from the superior alveolar artery in the same manner as described for the inferior alveolar artery.
DESCENDING PALATINE AND SPHENOPALATINE ARTERIES
The palatal blood supply comes from two sources but chiefly from the descending palatine artery, which descends from its origin from the maxillary through the greater canal. Its greater palatine branch enters the palate through the greater palatine foramen and runs forward with its accompanying vein and nerve in a groove at the junction of the palatine and alveolar processes. It is distributed to the bone, glands, and mucosa of the hard palate and to the bone and mucosa of the alveolar process, in which it forms anastomoses with fine branches of the superior alveolaris. Minor branches of the descending palatine artery pass to the soft palate through lesser palatine foramina in the palatine bone.
The nasopalatine branch of the sphenopalatine artery courses obliquely forward and downward on the septum and enters the palate through the incisive canal. It has a limited distribution to the incisive papilla and adjacent palate and forms an anastomosis with the greater palatine.
Nerve Supply to the Jaws and Teeth
The sensory nerve supply to the jaws and teeth is derived from the maxillary and mandibular branches of the fifth cranial, or trigeminal nerve (Figure 14-36), whose ganglion, the trigeminal, is located at the apex of the petrous portion of the temporal bone. The innervation of the orofacial region includes, in addition to the trigeminal nerve (including V2 and V3), other cranial nerves, (e.g., VII, XI, XII) (Figure 14-37).
Figure 14-36 Distribution of the trigeminal nerve.
MAXILLARY NERVE
The maxillary nerve (see Figure 14-36) courses forward through the wall of the cavernous sinus and leaves the skull through the foramen rotundum.5 It crosses the pterygopala-tine fossa, where it gives branches to the pterygopalatine ganglion, a parasympathetic ganglion. This ganglion gives off several branches, now containing visceral motor and sensory fibers, to the mucous membrane of the mouth, nose, and pharynx.
The branches of clinical significance include a greater palatine branch that enters the hard palate through the greater palatine foramen and is distributed to the hard palate and palatal gingiva as far forward as the canine tooth; a lesser palatine branch from the ganglion that enters the soft palate through the lesser palatine foramina; and a nasopalatine branch of the posterior or superior lateral nasal branch of the ganglion that runs downward and forward on the nasal septum. Entering the palate through the incisive canal, it is distributed to the incisive papilla and to the palate anterior to the anterior palatine nerve.
The maxillary nerve also has a posterior superior alveolar branch from its pterygopalatine portion. This nerve enters the alveolar canals on the infratemporal surface of the maxilla and, forming a plexus, is distributed to the molar teeth and the supporting tissues.
Figure 14-37 Mandibular nerve. The inferior alveolar nerve branch (in the cut section of the mandible and the mandibular canal) provides innervation for the mandibular teeth. The injection of a local anesthetic into the vicinity of the lingula (see Figure 14-17) blocks the sensory innervation of the inferior alveolar nerve and the lingual nerve ("mandibular block"), which results in a feeling of numbness of the mandibular teeth, lower lip, and side of the tongue on the side of the injection.
The maxillary nerve enters the orbit and, as the infraorbital nerve, runs forward in its floor, first in the infraorbital groove and then in the infraorbital canal. It terminates at the infraorbital foramen in branches distributed to the upper face. At a variable distance after it enters the orbit, a middle superior alveolar branch arises from the infraorbital nerve and runs through the lateral wall of the maxillary sinus. It is distributed to the premolar teeth and surrounding tissues and joins the alveolar plexus. The middle superior alveolar nerve may be associated closely with the posterior superior alveolar nerve as its origin but often branches near the infraorbital foramen.
An anterior superior alveolar branch leaves the infraorbital nerve just inside the infraorbital foramen and is distributed through bony canals to the incisor and canine teeth. All three superior alveolar nerves join in a plexus above the process. From the plexus, dental branches are given off to each tooth root and interdental branches to the bone, perio-dontal membrane, and gingiva, the distribution being similar to that described for the arteries.
MANDIBULAR NERVE
The mandibular nerve (see Figure 14-37) leaves the skull through the foramen ovale and almost immediately breaks up into its several branches. The chief branch to the lower jaw is the inferior alveolar nerve, which at first runs directly downward across the medial surface of the lateral pterygoid, at the lower border of which it is directed laterally and downward across the outer surface of the medial pterygoid muscle to reach the mandibular foramen. Just before entering the foramen, it releases the mylohyoid branch, which is a motor branch to the mylohyoid muscle and anterior belly of the digastric muscle.
The inferior alveolar nerve continues forward through the mandibular canal beneath the roots of the molar teeth to the level of the mental foramen. During this part of its course, it gives off branches to the molar and premolar teeth and their supporting bone and soft tissues. The nerves to the teeth do not arise as individual branches but as two or three larger branches that form a plexus from which inferior dental branches enter individual tooth roots and interdental branches supply alveolar bone, periodontal membrane, and gingiva.
At the mental foramen, the nerve divides and a smaller incisive branch continues forward to supply the anterior teeth and bone, and a larger mental branch emerges through the foramen to supply the skin of the lower lip and chin.
Other branches of the mandibular nerve contribute in some degree to the innervation of the mandible and its investing membranes. The buccal nerve, although chiefly distributed to the mucosa of the cheek, has a branch that is usually distributed to a small area of the buccal gingiva in the first molar area, but in some cases, its distribution may extend from the canine to the third molar. The lingual nerve, as it enters the floor of the mouth, lies against the body of the mandible and has mucosal branches to a variable area of lingual mucosa and gingiva. The mylohyoid nerve may sometimes continue its course forward on the lower surface of the mylohyoid muscle and enter the mandible through small foramina on either side of the midline. In some individuals, it is thought to contribute to the innervation of central incisors and periodontal ligament.
