Patient-friendly definition from the DentistsDirectory.org dental glossary.
The maxilla is the upper jaw — a paired bone (left and right halves fused at the midline) that forms the skeletal foundation of the middle face. Unlike the mandible, the maxilla is fixed and does not move independently. It articulates with many other facial bones and plays a structural role well beyond just holding the upper teeth.
The maxilla performs several structural functions simultaneously: it holds the upper teeth within the alveolar process; forms the hard palate (the bony roof of the mouth) together with the palatine bones; contributes to the floor of the eye sockets (orbits); forms the lateral walls and floor of the nasal cavity; and houses the maxillary sinuses — the large air-filled cavities on each side of the nose. The proximity of the upper molar roots to the maxillary sinus floor is clinically important: deep upper molar roots sometimes extend into the sinus, and extraction of these teeth can occasionally create a sinus communication that requires specific management.
Severe gum disease, tooth loss, and long-term denture wear all cause bone resorption in the maxillary alveolar process, reducing available bone for implants. The upper arch typically has less bone density than the lower jaw, making upper implants generally more technically challenging and requiring longer healing times. Upper jaw fractures (Le Fort fractures) from facial trauma can disrupt the midface significantly and typically require surgical fixation. Cleft palate — a developmental gap in the maxillary palate — is one of the most common birth defects and is treated surgically in early childhood.