The maxillary sinus is the largest of the four paired paranasal sinuses, occupying a hollow cavity within the maxillary bone on each side of the face, just lateral to the nose and above the upper posterior teeth. Because the roots of the maxillary premolars and molars often project into or lie in close proximity to the sinus floor, this anatomical relationship carries significant consequences for everyday dental practice.

Anatomy and Structure

Each maxillary sinus is roughly pyramidal in shape, with its base formed by the lateral nasal wall and its apex extending toward the zygomatic arch. The floor of the sinus — also called the antral floor — rests just above the roots of the upper first and second molars and, to a lesser degree, the second premolars. In some individuals, root apices may indent or even perforate the sinus floor, leaving only the thin Schneiderian membrane separating the root tip from the sinus cavity.

Clinical Significance in Dentistry

The maxillary sinus plays a central role in dental diagnosis and treatment planning. Its relationship to the alveolar bone of the upper jaw means that infections, bone loss, and surgical procedures in this region can directly affect — or be affected by — sinus health.

• Sinusitis of dental origin: Infection from a periapical abscess or advanced periodontal disease on an upper molar can cause unilateral maxillary sinusitis, often mistaken for a primary sinus condition.
• Oroantral communication: Extraction of upper posterior teeth can create an opening between the oral cavity and the sinus, requiring prompt surgical closure to prevent chronic infection.
• Dental implant planning: Insufficient vertical bone height between the sinus floor and the alveolar crest may necessitate a sinus lift (sinus augmentation) before implant placement can proceed safely.
• Diagnostic imaging: Panoramic radiographs and cone-beam CT (CBCT) scans routinely capture the maxillary sinuses, enabling detection of mucosal thickening, polyps, or retention cysts that indicate sinus pathology.
• Referred pain: Sinus pressure from congestion or infection can mimic toothache in the upper posterior teeth, complicating differential diagnosis between dental and sinonasal conditions.

The Schneiderian Membrane

Lining the interior of the maxillary sinus is the Schneiderian membrane, a thin, delicate mucoperiosteum that must be carefully preserved during sinus augmentation procedures. Perforation of this membrane is the most common intraoperative complication and can compromise graft stability and healing. Pre-surgical CBCT evaluation of membrane thickness and local anatomy is now considered standard of care to minimize this risk.

A thorough understanding of the maxillary sinus and its relationship to the upper posterior dentition is indispensable for accurate diagnosis, safe extractions, successful implant rehabilitation, and correctly distinguishing dental pain from sinus-related discomfort.