Maxilla

Definition

The maxilla (plural: maxillae) is a vital viscerocranium bone that forms the upper jaw. It holds the upper teeth, forms the boundaries of three cavities (the roof of the oral cavity, the floor and lateral wall of the nasal cavity, and the floor of the orbit), and contains the largest of the paranasal sinuses.

The two maxillae fuse at the **intermaxillary suture** during embryonic development to form the upper jaw skeleton.

Anatomical Parts

The maxilla consists of a central body and four projections known as processes:

1. The Body of the Maxilla

The pyramid-shaped central portion containing the maxillary sinus (Antrum of Highmore).

Infraorbital foramen: Located on the anterior surface, transmitting the infraorbital nerve and vessels.
Maxillary tuberosity: A rounded eminence on the posterior surface, located distally to the third molar; an important landmark for local anesthesia (PSA nerve block).

2. The Four Processes

Alveolar process: The thickest part of the bone, containing the dental sockets (dental alveoli) for the maxillary teeth.
Zygomatic process: Points laterally to articulate with the zygomatic bone (cheekbone).
Frontal process: Extends upward to articulate with the frontal bone, forming part of the lateral boundary of the nose.
Palatine process: A horizontal projection that forms the anterior three-quarters of the hard palate.

Clinical Significance

The maxilla is of paramount importance in several dental specialties:

Sinus Proximity

The roots of the maxillary molars and premolars are often in close proximity to the floor of the maxillary sinus.

Oroantral communication: A potential complication after extraction where a hole is created between the mouth and the sinus.
Sinus lift: A surgical procedure to increase bone volume in the posterior maxilla for dental implant placement.

Le Fort Fractures

In oral and maxillofacial surgery, the maxilla is the site of classic "Le Fort" midface fractures:

Le Fort I: Horizontal fracture above the alveolar process (floating palate).
Le Fort II: Pyramidal fracture involving the nasal bones and orbital floor.
Le Fort III: Complete craniofacial dysjunction.

Orthodontics

The maxilla can be expanded using a Rapid Palatal Expander (RPE) by opening the mid-palatal suture, typically in growing patients.