Cone-beam CT scans illustrating maxillary sinus floor defects classified according to the proposed topographic-anatomical system. A. Type I: Small defects surrounded by four bony walls, with at least one linear dimension <5mm. B. Type II: Larger four-wall defects, where all linear dimensions exceed 5mm. C. Type III: Defects lacking one wall, typically the buccal wall; less frequently the palatal wall. D. Type IV: Extensive defects with only one or two remaining bony walls.