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Inferior wall of maxillary sinus

The inferior wall of the maxillary sinus, also known as the floor of the maxillary sinus, forms the lower boundary of the sinus cavity and separates it from the oral cavity. It is closely related to the alveolar process of the maxilla and the roots of the maxillary posterior teeth, making it highly relevant in dental imaging, sinus disease assessment, and maxillofacial surgery.

Its thickness and contour are variable and influenced by age, dentition, and pneumatization of the maxillary sinus.

Synonyms

  • Floor of the maxillary sinus

  • Inferior maxillary sinus wall

Location

  • Forms the inferior boundary of the maxillary sinus

  • Situated superior to the alveolar process of the maxilla

  • Extends from the anterior premolar region to the posterior molar region

  • Lies inferior to the sinus cavity and superior to the oral cavity

  • Closely related to the roots of maxillary premolars and molars

Anatomical components

  • Thin cortical bone forming the sinus floor

  • Alveolar process of the maxilla

  • Dental root prominences (may project into the sinus cavity)

  • Schneiderian membrane lining the sinus internally

Relations

Superiorly:

  • Maxillary sinus cavity

  • Schneiderian membrane

Inferiorly:

  • Alveolar process of the maxilla

  • Roots of maxillary premolars and molars

Anteriorly:

  • Premolar region of the maxilla

Posteriorly:

  • Maxillary tuberosity

  • Posterior alveolar canals

Medially:

  • Nasal cavity (via the medial sinus wall)

Laterally:

  • Zygomatic process of the maxilla

Developmental and anatomical variations

  • Sinus pneumatization: May extend inferiorly between tooth roots

  • Root protrusion: Dental roots may elevate or indent the sinus floor

  • Asymmetry: Common between right and left sides

  • Post-extraction changes: Sinus floor may descend after tooth loss

X-ray appearance

Periapical and panoramic radiographs:

  • Sinus floor: Thin, curved radiopaque line superior to maxillary teeth

  • Continuity: Smooth and uninterrupted cortical outline

  • Dental relationship: Roots may appear close to or projecting into the sinus

  • Visibility: Best appreciated in panoramic (OPG) views

CT appearance

Non-contrast CT:

  • Inferior wall: Thin hyperdense cortical bone forming the sinus floor

  • Contour: Smooth or scalloped appearance related to tooth roots

  • Alveolar relationship: Clear depiction of proximity to dental roots

Post-contrast CT:

  • Bony floor: No enhancement

  • Sinus lining: Thin mucosal lining may be visible

3D CT VRT appearance

Volume-rendered technique (VRT):

  • Sinus floor contour: Clearly visualized inferior boundary of the maxillary sinus

  • Alveolar ridge relationship: Demonstrates spatial relation to dental sockets

  • Utility: Helpful in pre-implant planning and maxillofacial surgery

  • Symmetry assessment: Allows comparison of right and left sinus floors

MRI appearance

T1-weighted images:

  • Cortical bone of sinus floor: Low signal intensity

  • Marrow of alveolar process: Intermediate to high signal

  • Sinus cavity: Low signal if air-filled

T2-weighted images:

  • Cortical bone: Low signal

  • Sinus cavity: High signal if fluid-containing, low if air-filled

CT image

ct Inferior wall of maxillary sinus anatomy image -img-00000-00000

X-Ray image

Inferior wall of maxillary sinus