Volumetric Assessment of Maxillary Sinus Using CBCT in Relation to Sinonasal Anatomic Variations in an Iraqi Population

BACKGROUND: Maxillary sinus volume (MSV) influences sinus floor elevation, dental implant planning, and rhinologic decision-making. Anatomic variants [nasal septal deviation (NSD), concha bullosa (CB), maxillary sinus septa (MSS)] and mucosal thickening (MT) may alter aeration/ventilation and, consequently, MSV; prior reports are mixed. OBJECTIVE: To compare MSV among normal, NSD, MSS, inferior concha bullosa (ICB), and mucosal thickening (MT >2 mm) groups in an Iraqi CBCT cohort. DESIGN SETTING PARTICIPANTS: A retrospective cross-sectional study of 200 adult CBCT scans obtained for dentomaxillofacial indications (2020-2025) at a tertiary center in Baghdad (5 independent groups; n=40 each). Reporting follows STROBE guidelines. METHODS: Bilateral MS were segmented in OnDemand3D and averaged per subject (cm3). Assumptions were checked (Shapiro-Wilk; Levene). Given non-normality and heteroscedasticity, Welch ANOVA was the primary test; Games-Howell handled pairwise contrasts; Dunnett (two-sided) compared each variant versus normal. Effect sizes: partial η2, ω2, and Hedges g (95% CI). RESULTS: Assumptions were violated (Shapiro-Wilk P<0.05 in 4/5 groups; Levene P<0.001). Welch ANOVA showed a large between-group effect [F(4,≈96.41)=45.85, P<0.001; η2≈0.468; ω2≈0.456]. Mean MSV (cm3): ICB 15.05, MSS 14.17, normal 13.95, NSD 13.08, MT 12.08. Games-Howell: ICB>all and MT<all (all P<0.001); NSD<normal (Δ=0.88 cm3, P=0.003); MSS≈normal (Δ=0.22 cm3, P=0.91). Largest standardized contrast: ICB versus MT g=2.50. CONCLUSIONS: In this Iraqi CBCT cohort, ICB presented the largest MSV and MT the smallest; NSD showed a modest reduction versus normal, while MSS did not differ. A ventilation-pathway model (ostium/infundibulum geometry and mucosal disease) better explains volume differences than variant labels alone.