Effects of Flap Management and Membrane Fixation on Augmented Ridge Dimensions in Guided Bone Regeneration: A Preclinical In Vivo Study

Objectives To investigate the main effects of flap management and membrane fixation and their interaction on augmented ridge dimensions 12 weeks after guided bone regeneration (GBR) in chronic noncontained defects. Materials and Methods Implants were placed into chronic noncontained defects in six male dogs using a split‐mouth 2 × 2 factorial design ( n = 6 sites per condition). Buccal defects were augmented with particulate bone substitute and resorbable collagen membranes and assigned to four groups based on the stabilization strategy: retentive flap (limited periosteal release) with or without membrane fixation (Ret‐F, Ret‐UF) and extensive flap release with or without membrane fixation (Ex‐F, Ex‐UF). Augmented ridge dimensions and tissue composition were assessed using micro‐computed tomography and histomorphometric analyses at 12 weeks. Results Flap × fixation interactions were identified for micro‐CT augmented ridge area ( p = 0.015) and volume ( p = 0.005) and for several histomorphometric outcomes. A flap main effect occurred only at 5‐mm augmented tissue width ( p = 0.033). Micro‐CT volume was greater for Ret‐UF than for Ex‐UF (difference, 106.70 mm 3 ; p = 0.029) and for Ex‐F than for Ex‐UF (114.65 mm 3 ; p = 0.021). Micro‐CT area was greater for Ex‐F than for Ex‐UF (8.072 mm 2 ; p = 0.042), and tissue width at 5 mm was greater for Ret‐UF than for Ex‐UF (2.442 mm; p = 0.015). Conclusion In this exploratory study, flap management and membrane fixation had context‐dependent associations with augmented dimensions. Limited release without fixation and extensive release with fixation showed greater dimensions than extensive release without fixation in selected comparisons.