Influence of Barrier Membrane and Peri-Implantitis-Like Bone Defect Configurations on Graft Stability.

Objectives
The objective of this ex vivo investigation was to study the significance of barrier membrane application on graft stability across different peri-implantitis-related bone defect configurations.Materials And Methods
Fresh pig mandibles were used to create standardized peri-implant-like bone defects, including dehiscence defects, 2-3 wall defects, and circumferential defects. Defects were treated using identical grafting and flap closure protocols, with or without barrier membrane application. High-resolution cone-beam computed tomography (CBCT) scans were obtained before flap closure, after primary closure, and following simulated soft-tissue movement in order to analyze graft material thickness at multiple predefined levels along the implant surface. Changes in graft thickness over time were analyzed using generalized estimating equation (GEE) linear regression models.Results
A total of 120 bone augmentation procedures in 20 pig hemimandibles were analyzed. In dehiscence defect morphologies, graft thickness decreased significantly over time, with the greatest dimensional changes occurring immediately after primary wound closure (GEE main effect of TIME, p < 0.001). In these defects, pronounced coronal (platform level) graft displacement was observed, with thickness reductions of approximately 1.2-1.4 mm after closure and total reductions exceeding 85% following simulated soft-tissue movement. Barrier membrane application did not prevent graft collapse nor modify the coronal temporal pattern; however, it resulted in a limited attenuation of graft loss at selected middle levels (approximately 0.15-0.25 mm, corresponding to 5%-15% relative reduction). In 2-3 wall defects, graft thickness also decreased significantly over time across all evaluated levels (p < 0.001), with membrane application consistently attenuating early graft displacement at coronal and middle levels. In contrast, circumferential defects demonstrated high intrinsic dimensional stability, with minimal dimensional changes over time (< 0.1 mm) and no significant membrane-related effects. Across defect types exhibiting graft displacement, coronal measurements consistently showed the greatest susceptibility to thickness reduction.Conclusion
Graft stability following reconstructive therapy of peri-implantitis-like bone defects is primarily influenced by defect morphology. Hence, the effect of barrier membrane coverage appears to be defect-dependent. Membrane application provides limited attenuation of graft displacement in 2-3 wall defects while no consistent or clinically meaningful additional effect is observed in dehiscence or circumferential defects.