A Nomogram for Predicting Buccal Bone Coverage at the Implant Shoulder in Bone Augmentation Using the Full-Thickness Envelope Flap Technique: A Retrospective Cohort Study.
OBJECTIVES To identify the predictors, develop and validate a nomogram for implant buccal shoulder dehiscence following horizontal bone augmentation using the full-thickness envelope flap technique (FEFT). MATERIAL AND METHODS A total of 318 implants in 250 patients receiving FEFT were included in the study. Implants were classified as "buccal shoulder dehiscence" or "buccal shoulder coverage" based on radiographic images obtained at 6 months postoperatively. Predictive factors for buccal shoulder dehiscence were evaluated using regression analysis. A nomogram was constructed, and model performance was assessed through calibration and discrimination analyses. RESULTS Six factors were identified as predictors: initial deficit depth, graft overhanging angle, bone graft contour relative to the bone arch, type of bone substitute material, implant bucco-lingual position with respect to the initial alveolar bone profile, and implant site. The model showed an apparent area under the curve (AUC) of 0.899. This performance remained robust after patient-level cluster bootstrap validation (mean AUC = 0.886). The model demonstrated acceptable calibration, and decision curve analysis confirmed net clinical benefit. CONCLUSIONS This nomogram provides a practical tool for predicting buccal shoulder coverage at 6 months after implant placement with simultaneous FEFT. TRIAL REGISTRATION Trial Registration: The study protocol was registered at the Chinese Clinical Trial Registry (ChiCTR2500115545).