Garcia J, et al. - This trial was conducted to assess the effect of the membrane exposure on the guided bone regeneration (GBR) results at peri-implant sites and edentulous ridges. Experts concluded that a significant detrimental influence was exerted on the outcome of bone augmentation by the membrane exposure after GBR procedures. The sites without membrane exposure had 74% more horizontal bone gain than the sites with exposure, in case of the edentulous ridges. The sites without membrane exposure displayed 27% more defect reduction as compared to the sites with exposure, for the peri-implant dehiscence defects.