The maxilla is the bone that forms your upper jaw. It holds your upper teeth, shapes the middle of your face, and creates the floor of your eye sockets and the roof of your mouth. What most people think of as a single bone is actually a pair: a left maxilla and a right maxilla fused together at the midline of your palate. Together, these two bones connect to nearly every other bone in the face, making the maxilla one of the most structurally important bones in the skull.
Where the Maxilla Sits in the Skull
The maxilla occupies the center of the face. It sits below the eye sockets, above the mouth, and on either side of the nose. The two maxillary bones meet at the center of the hard palate, forming a seam called the median maxillary suture. From there, the maxilla extends upward to meet the forehead bone, outward to meet the cheekbones, and backward toward the base of the skull.
In total, each maxilla connects to several neighboring bones: the frontal bone (forehead), the nasal bones (bridge of the nose), the zygomatic bone (cheekbone), the lacrimal bone (inner eye socket), the ethmoid bone (between the eyes), the palatine bone (back of the hard palate), the sphenoid bone (skull base), and the opposite maxilla. This web of connections is what gives the midface its structural rigidity.
The Four Processes of the Maxilla
The maxilla isn’t a simple block of bone. It has four projections, called processes, that reach out in different directions to form different parts of the face.
- Alveolar process: The horseshoe-shaped ridge along the bottom of the maxilla. This is where your upper teeth sit. Each tooth root is embedded in its own bony socket, and small channels run through the bone carrying blood vessels and nerves to each tooth.
- Palatine process: A thick, horizontal shelf that forms about two-thirds of the hard palate (the roof of your mouth). It also creates the floor of the nasal cavity, separating your mouth from your nasal passages.
- Zygomatic process: A lateral projection that connects the maxilla to the cheekbone. It sits above the first upper molar and helps define the width of your face and the prominence of your cheeks.
- Frontal process: A thin projection that extends upward along the side of your nose to meet the forehead bone. It shapes the bridge of your nose and forms part of the groove that channels tears from your eyes down into your nasal cavity.
What the Maxilla Does
The maxilla plays a role in almost everything your face does. Its alveolar process anchors all of your upper teeth, making it essential for biting and chewing. The palatine process separates the oral cavity from the nasal cavity, which is critical for both breathing and speaking. Without that bony partition, air would leak between your nose and mouth during speech, and swallowing would be far more difficult.
The bone also forms the lower rim and part of the floor of each eye socket, supporting and protecting the eyes. And because the maxilla connects to the cheekbone, the nasal bones, and the forehead, it serves as a structural keystone for the entire midface. The shape of your maxilla influences how prominent your cheeks look, how wide your face appears, and how your upper and lower teeth align when you close your mouth.
The Maxillary Sinus
Hollowed out inside each maxilla is a large air-filled cavity called the maxillary sinus. It’s the largest of the four pairs of sinuses in the skull, with a typical volume of roughly 8 cubic centimeters per side. The sinus sits just above the roots of the upper back teeth, sometimes separated from them by only a paper-thin layer of bone. This close relationship is why a bad upper molar infection can sometimes spread into the sinus, and why sinus pressure can feel like a toothache.
The sinus drains into the nasal cavity through a small opening. When that opening gets blocked by swelling or mucus, fluid backs up inside the sinus, producing the pain and pressure of sinusitis.
Maxillary Bone Density
The maxilla is noticeably less dense than the lower jaw (mandible). Measured on CT scans, the cortical bone of the maxilla ranges from about 810 to 940 Hounsfield units in most areas, while the mandible ranges from 800 to 1,580 units and gets progressively denser toward the back. The densest areas of the maxilla are around the canine and premolar teeth. The least dense area is the maxillary tuberosity, the rounded bump at the very back of the upper jaw.
This difference matters most in dentistry. Because the maxilla is softer and more porous than the mandible, dental implants placed in the upper jaw sometimes need longer healing times or specialized techniques to achieve a secure hold.
What Happens After Tooth Loss
When upper teeth are lost or extracted, the alveolar process that once held them begins to shrink. Bone needs the mechanical stimulation of chewing transmitted through tooth roots to maintain itself. Without it, the body gradually reabsorbs the bone. In the maxilla, this resorption narrows the dental arch from the outside in, meaning the upper ridge gets smaller over time.
After significant resorption, the width of the lower jaw typically exceeds the width of the upper jaw in the molar region by an average of 6 to 7 millimeters. That mismatch stays relatively constant regardless of how much time has passed, which is one reason dentures become harder to fit and less stable as the years go on. Dental professionals plan implants and prosthetics around these predictable shrinkage patterns.
Maxillary Fractures
Because the maxilla sits at the center of the face, it’s vulnerable in high-impact trauma like car accidents, falls, and sports injuries. Maxillary fractures are classified using the Le Fort system, which describes three patterns based on where the fracture line runs.
A Le Fort I fracture runs horizontally through the maxilla just above the tooth roots, separating the hard palate from the rest of the face. It typically causes a swollen upper lip, a misaligned bite, and mobility of the upper jaw when pressed. A Le Fort II fracture follows a pyramidal path through the nasal bridge, the inner eye sockets, and the lower orbital rims before extending backward. It produces significant facial swelling, bruising around both eyes, nosebleeds, and sometimes double vision or numbness in the cheek and upper lip area.
A Le Fort III fracture is the most severe. The fracture line runs along the base of the skull, completely separating the entire midface from the cranium. The face appears elongated and flattened, sometimes described as a “dish-face” deformity. Cerebrospinal fluid may leak from the nose, and the eyes can appear sunken. All three types require surgical repair, with recovery timelines ranging from weeks to months depending on severity.