Background: Understanding microbial colonization on different membranes is critical for guided bone regeneration procedures such as socket preservation, as biofilm formation may affect healing and clinical outcomes. This randomized controlled clinical trial (RCT) investigates, for the first time, the microbiome of two different high-density polytetrafluoroethylene (d-PTFE) membranes that are used in socket preservation on a highly molecular level and in vivo. Methods: This RCT enrolled 39 participants, with a total of 48 extraction sites, requiring subsequent implant placement. Sites were assigned to two groups, each receiving socket grafting with a composite bone graft (50% autogenous bone, 50% bovine xenograft) and covered by either a permamem^® (group P) or a Cytoplast™ (group C). The membranes were removed after four weeks and analyzed using scanning electron microscopy (SEM) for bacterial adherence, qPCR for bacterial species quantification, and next-generation sequencing (NGS) for microbial diversity and composition assessment. Results: The four-week healing period was uneventful in both groups. The SEM analysis revealed multispecies biofilms on both membranes, with membranes from group C showing a denser extracellular matrix compared with membranes from group P. The qPCR analysis indicated a higher overall bacterial load on group C membranes. The NGS demonstrated significantly higher alpha diversity on group C membranes, while beta diversity indicated comparable microbiota compositions between the groups. Conclusion: This study highlights the distinct microbial profiles of two d-PTFE membranes during the four-week socket preservation period. Therefore, the membrane type and design do, indeed, influence the biofilm composition and microbial diversity. These findings may have implications for healing outcomes and the risk of infection in the dental implant bed and should therefore be further explored.

In guided bone regeneration (GBR) procedures, d-PTFE membranes are often used as a barrier to promote alveolar ridge regeneration. The aim of this randomized clinical trial was to examine the microbial diversity and structure of biofilms on two types of d-PTFE membranes, Permamem^® and Cytoplast™, over four-week oral cavity exposure periods. Bacterial biofilm analysis was performed using 16S rRNA next-generation sequencing (NGS) on 36 samples (20 Permamem^® and 16 Cytoplast™). The results showed significant differences in the microbial profiles: Cytoplast™ membranes showed reduced microbial diversity and an enhanced proportion of pathobionts like Selenomonas, Segatella, Fusobacterium and Parvimonas, which are associated with periodontal and peri-implant diseases and alveolar bone loss. Permamem^® membranes promoted colonization by bacteria associated with healthy oral conditions, such as the genera Streptococcus, Kingella and Corynebacterium. Overall, our results showed that Cytoplast™ membranes generate a specific type of biofilm, leading to reduction in health-related bacterial species and facilitating growth conditions for dysbiosis shift. Further research and patient follow-ups are essential to thoroughly evaluate the clinical implications of different d-PTFE membranes used in guided bone regeneration.