UPPER JAW (MAXILLA)
The upper jaw (maxilla) is an irregular bone formed from the right and left
maxillary bones, which unite along the midline of the face (see figure 2-2). It joins in the
palate (roof of the mouth) at the intermaxillary suture or at the median palatal suture.
The maxilla is considered the key to the architecture of the face. All the bones of the
face, except the mandible, come in direct contact with the maxilla, that is, they have
sutural contact. The maxilla consists of a body which gives shape to the face and forms
part of the orbits and nasal cavity. Within the body of each maxillary bone is a large
cavity called the maxillary sinus (or the antrum of Highmore). The maxilla also consists
of four processes--nasal, zygomatic, alveolar, and palatal. The maxillary sinus and the
alveolar process are important landmarks in dental radiography.
a. Maxillary Sinus. The maxillary sinus (antrum of Highmore) is a large
pyramidal cavity in the maxilla with its base toward the nose. This cavity is separated
from the nasal cavity by a very thin wall of bone (see figure 2-4). Within this wall is an
irregular opening connecting the sinus with the nasal cavity above the inferior nasal
conchae. The floor or lower wall of the sinus is formed by the maxillary alveolar process
(see paragraph "d" below). It is level with the floor of the nose. Projecting into the floor
of the sinus are many cone-shaped processes. These processes correspond to the
roots of the maxillary teeth (usually bicuspids and molars) located in the region of the
sinus. Because of this proximity, the pain of a sinus infection and that of a toothache
are sometimes hard to tell apart.
Figure 2-4. Lateral aspect of maxilla and adjacent bones.