Does Early Re-Entry Surgery Following Simultaneous Guided Bone Regeneration Compromise the Dimension of Peri-Implant Tissues?

To investigate whether early re-entry surgery following simultaneous guided bone regeneration (GBR) and implant placement has a negative impact on the outcome of bone regeneration and osseointegration. In the edentulous mandible of six mongrel dogs, buccal peri-implant dehiscence defects were surgically created. Bone-level implants were placed with GBR, followed by submerged healing. Two experimental groups were randomly assigned according to the timing of re-entry and healing abutment connection at 2 months (early group) and 4 months (late group) following GBR. All animals were euthanised 5 months after GBR for histological analysis. One implant in the late group failed as a result of fibrin incarceration. There was no statistically significant difference between the two groups regarding new bone area (1.98 mm2 [interquartile range, 1.53-2.98] and 0.88 mm2 [0.09-1.79]; early vs. late group, respectively; p = 0.063); bone-to-implant contact (53.80% [40.88-63.10] and 54.15% [45.21-66.02], early vs. late groups, respectively; p > 0.999); width and height of the augmented tissue (p > 0.05); and peri-implant mucosal dimensions including thickness, height and volume (p > 0.05). Early second-stage surgery results in similar bone regeneration, osseointegration and mucosal dimensions as late abutment connection.