Maxillary sinus floor defects: a key challenge in posterior maxillary implant planning

Introduction: Maxillary sinus floor defects pose a notable challenge in posterior maxillary implant planning due to their complex anatomy and frequent association with insufficient bone volume. This study aimed to evaluate the anatomical characteristics of such defects, introduce a topographic-anatomical classification system, and assess its clinical utility for guiding augmentation techniques and implant timing. Materials and methods: A retrospective cohort study was conducted on 91 patients who underwent evaluation for posterior maxillary implant rehabilitation at Bogomolets National Medical University (2021–2024). Defects were classified based on size, extent, and bony wall integrity. CT data were analyzed using Mimics Medical 23.0 to assess defect area, mesiodistal and vestibulo-oral dimensions, and residual bone height. ANOVA and Kruskal–Wallis tests were used to compare defect types and assess treatment feasibility. Results: Defects varied widely in size and morphology. Type I defects (37.4%) were small and surrounded by four walls, while Type IV (18.6%) were extensive and involved major wall loss. Types I and II could support transcrestal sinus lift and simultaneous implantation, while Types III and IV typically required staged lateral augmentation and additional ridge reconstruction. Residual bone height did not differ significantly across types ( p >0.05), but linear dimensions and area increased progressively ( p <0.001). Conclusion: The proposed classification supports individualized treatment planning by integrating defect dimensions and wall integrity, potentially improving outcomes in posterior maxillary implantology.