The Big Nose Pattern at the Second Upper Molar-A Retrospective CBCT Study.

Area of Science:

• Anatomy and Morphology
• Dental Implantology
• Radiology

Background:

• Anteroposterior gradient of nasal fossa pneumatization documented at the second premolar level.
• Pneumatization patterns above the maxillary alveolar base at the second upper molar (M2) remain uncharacterized.
• M2 is a primary site for posterior implant rehabilitation.

Purpose of the Study:

• Quantify the pneumatization gradient at M2.
• Classify pneumatization patterns (Type 1: pure antral; Type 2: antral with palatine recess; Type 3: Big Nose pattern).
• Assess bilateral symmetry, sex distribution, and compare with second premolar data.

Main Methods:

• Retrospective study of 165 cone-beam computed tomography (CBCT) scans (330 sides) from a Romanian population.
• Classification of pneumatization patterns into Type 1, Type 2, and Type 3.
• Bilateral symmetry assessed using Cohen's kappa; sex differences analyzed using Fisher's exact test.

Main Results:

• Type 1 pattern observed in 93.3% of sides, Type 2 in 4.2%, and Type 3 in 2.4%.
• High bilateral symmetry (98.8%, kappa = 0.904), with Type 3 patterns occurring bilaterally.
• The 'Big Nose' pattern was 6.8-fold less prevalent at M2 compared to the second premolar level.

Conclusions:

• A significant anteroposterior gradient in nasal fossa pneumatization exists over the maxillary alveolar base.
• Maxillary sinus dominates exclusively in 97.6% of M2 sides, enabling predictable standard sinus floor elevation.
• Invariable bilaterality of the 'Big Nose' pattern at M2 supports symmetrical surgical planning.