The Effect of Defect Morphology and Membrane Fixation on 3D Graft Material Displacement During Primary Wound Closure in Horizontal Bone Augmentation—An Ex Vivo Study

Objectives: This preclinical study evaluated the influence of two defect morphologies on graft material displacement (GMD) during primary wound closure in horizontal bone augmentation (HBA). Secondary aims included assessing the effect of membrane stabilization and the role of local soft tissue characteristics on GMD. Materials and Methods: Standardized HBA procedures following guided bone regeneration principles were performed on fresh pig hemimandibles. Each mandible received two sequential HBAs, randomized for defect morphology—partially contained (PCD) vs. contained (CD)—and membrane stabilization with (+Pins) or without (−Pins) four fixation pins. GMD was assessed using cone-beam computed tomography and intraoral scanning by comparing graft dimensions before and after wound closure, at nine levels from the implant platform and across nine delimited sections, respectively. Results: Sixty HBA procedures were analyzed. A notable GMD was observed for both PCD and CD, with no significant differences between them. In contrast, membrane stabilization significantly reduced three-dimensional GMD across all sections, with the most pronounced effect in the central-crestal section (p < 0.001). At the implant platform level, GMD was −15.8% ± 25.6% with pins vs. −38.1% ± 27.4% without pins (p < 0.001). Across all groups, GMD occurred in an apico-lateral direction, with the greatest volume loss in the central-crestal, mesial, and distal crestal sections. Soft tissue phenotype did not affect GMD (p ≥ 0.240). Conclusion: Defect morphology did not significantly influence the notable apico-lateral GMD. However, membrane stabilization using pins effectively reduced graft displacement, minimizing movement during primary wound closure.