Associations of Sinus Width, Septa, and Schneiderian Membrane Thickness with Bone Formation After Lateral Window Sinus Augmentation

Anatomical variations of the maxillary sinus may affect surgical access and graft distribution after lateral window sinus augmentation, but their association with histologic bone regeneration remains uncertain. This study aimed to evaluate associations between CBCT-derived sinus width, Schneiderian membrane thickness, and sinus septa and histomorphometric outcomes six months after lateral window sinus augmentation in severely atrophic posterior maxillae.

This prospective secondary analysis included 60 biopsy sites from 42 patients with residual bone height ≤4 mm. Sinus width was measured 10 mm above the sinus floor, and membrane thickness and sinus septa were assessed on clinically indicated CBCT examinations. Newly formed bone (NB) and residual graft material (R) were quantified in core biopsies obtained at six months. Site-level associations were explored using non-parametric methods, and patient-clustered linear mixed-effects models with a patient-specific random intercept were additionally fitted to account for multiple sites contributed by the same patient. Analyses were interpreted as exploratory because of the fixed cohort size and limited power for small associations.

Sinus width was greater in molar than premolar sites (19.75 ± 3.44 mm vs 15.63 ± 4.40 mm; p = 0.005). Sinus width was not significantly associated with NB or R. Septa were not associated with NB (p = 0.897), R (p = 0.327), baseline membrane thickness (p = 0.715), or post-augmentation membrane thickness (p = 0.941). Three membrane perforations (5.0%) were managed intraoperatively; no postoperative infections were recorded.

The data did not identify a moderate or larger association between the evaluated anatomical variables and six-month histomorphometric outcomes. The null findings should not be interpreted as proof of no effect because the study was a secondary analysis with clustered observations and limited power for small associations.

CBCT-defined sinus morphology was not significantly associated with NB or R in this cohort. CBCT remains important for surgical planning, while its value for predicting histologic bone formation requires confirmation in larger, cluster-aware studies.