# Maxilla > Maxilla anatomy for BDS Oral Anatomy — body, four processes, maxillary sinus relations, Le Fort fractures and exam favourites explained simply. - Canonical URL: https://prepelephant.com/topics/bds/oral-anatomy/maxilla-anatomy-bds - Exam / course: BDS · Subject: Oral Anatomy - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Maxilla", PrepElephant, https://prepelephant.com/topics/bds/oral-anatomy/maxilla-anatomy-bds ## Direct answer Paired, pyramidal and hollowed by the largest paranasal sinus, the maxilla carries the upper teeth, forms the roof of the mouth, the floor of the nasal cavity and part of the floor of the orbit. Each maxilla ossifies intramembranously from a single centre in the sixth week in utero and grows mainly at the tuberosity and the sutures. Its clinical anatomy revolves around four processes — frontal, zygomatic, alveolar and palatine — the infraorbital foramen, and the maxillary sinus, whose floor lies so close to the molar roots that an upper posterior extraction can end in an oro-antral communication. For exams the bone is inseparable from the Le Fort fracture lines and from the upward-and-inward resorption of the edentulous ridge. ## What you must remember - Largest bone of the face after the mandible; body plus four processes — frontal, zygomatic, alveolar and palatine; the two palatine processes meet at the midpalatal suture and fuse behind with the horizontal plate of the palatine bone. - Maxillary sinus (antrum of Highmore): present at birth, pneumatises with eruption; the first molar roots lie closest, sometimes separated from the sinus only by mucosa — the anatomy behind oro-antral fistula and post-extraction sinusitis. - Canine fossa, behind the canine eminence, gives origin to levator anguli oris; the incisive fossa in front gives origin to the nasalis (depressor septi). - Infraorbital foramen sits about 8–10 mm below the infraorbital margin in the pupillary line and transmits the infraorbital nerve and vessels — the landmark for the infraorbital nerve block. - Nerve supply is the maxillary division (V2); blood comes from maxillary artery branches — posterior superior alveolar, infraorbital, descending palatine and sphenopalatine. - Le Fort I is the Guérin or "floating maxilla" fracture; Le Fort II is pyramidal; Le Fort III is craniofacial dysjunction. - After tooth loss the maxillary ridge resorbs upward and inward, shrinking the denture-bearing area — the mirror image of the mandible's downward-and-outward pattern. - Cleft palate follows failure of the palatal shelves to fuse with each other and the nasal septum around the eighth to twelfth week in utero. ## Following a Le Fort I fracture line Begin at the piriform aperture and trace the Le Fort I line backwards: through the lateral wall of the nose and the anterior then posterior walls of the maxillary sinus, passing below the infraorbital foramen so the nerve escapes injury, across the pterygomaxillary fissure until the pterygoid plates separate from the tuberosity. The entire tooth-bearing segment — Guérin's floating maxilla — now moves on gentle manipulation. Clinically expect a step in the gingival buccal sulcus, gagging of occlusion from premature molar contact, bilateral epistaxis and crepitus. That same logic drives treatment — plates are placed on the buttresses (piriform rim and zygomaticomaxillary buttress are the standard maxillary approaches), with intermaxillary fixation used first to re-establish the occlusion before the segments are fixed. ## Viva traps on the maxilla The opening gambit is usually "largest bone of the face?" — the safe answer names the mandible first, then adds that the maxilla is largest excluding the mandible; half marks are lost either way if the qualifier is missing. The second trap is the sinus: asked which tooth is most easily pushed into the antrum during extraction, candidates name the third molar, but the classic answer is the first molar, whose buccal roots lie nearest the floor. Third, an oro-antral communication question expects the nose-blow test, instructions against nose blowing, decongestants and antibiotics, and a buccal advancement flap for a persistent fistula. Finally, when asked why the edentulous maxilla resorbs inward, say that the labial and buccal cortical plates are thinner and resorb faster than the palatal side, so the ridge migrates palatally. ## Frequently asked questions ### Which tooth roots lie closest to the maxillary sinus floor? The first permanent molar, particularly its buccal roots; the second premolar and other molars are also related, and occasionally only sinus mucosa separates them from the roots. ### Name the four processes of the maxilla. Frontal (articulates with the frontal and nasal bones), zygomatic, alveolar (carries the tooth sockets) and palatine (forms the anterior hard palate). ### Which fracture is called the Guérin fracture? Le Fort I, the transverse or low maxillary fracture that detaches the tooth-bearing segment and produces the floating maxilla. ### How is an oro-antral communication confirmed? By the nose-blow test — escape of air or bubbles from the socket — supported by radiographs; small communications close spontaneously within days, larger ones need a buccal advancement or palatal flap. ### Why does the edentulous maxilla resorb upward and inward? The thinner labial and buccal plates resorb faster than the thicker palatal cortical plate, so the crest shifts palatally and superiorly while the basal bone remains relatively stable. ### What structures pass through the infraorbital foramen? The infraorbital nerve with its artery and veins, emerging 8–10 mm below the orbital rim to supply the cheek and upper lip.