Evolution in the Peri-Implant Oral Microbiome and Their Relationship to Long-Term Marginal Bone Loss: A Randomized Clinical Study.

Objectives: To analyze the clinical, radiographic, and microbiological changes around implants with a multiphosphonate-treated surface, prosthetically loaded with two different protocols after 5 years of functional loading.

Material and methods: A randomized clinical trial was designed to initiate prosthetic loading over single dental implants after 8 (control) or 4 weeks (test). Several variables were analyzed, including patients' level variables, intrasulcular biofilm, and marginal bone level at several time points, from 1 to 60 months after loading.

Results: A total of 23 patients attended the 5-year follow-up visit. No clinical variable changed over time, except mucosal thickness from dental impressions to prosthesis delivery. No significant radiographic differences were observed either over time or between groups. Microbiologically, there was a change in the microbiome from the constitution of the biological width to the final follow-up. Seven species changed significantly, with a significant increase in Porphyromonas gingivalis and Tannerella forsythia from 12 to 60 months and a decrease in the other species. However, changes in the relative abundance of species over time, whether increasing or decreasing, did not show a correlation with marginal bone loss.

Conclusion: Implants with a multiphosphonate-treated surface showed no differences in clinical and radiographic variables after 5 years of function, regardless of the prosthetic loading protocol used. From a microbiological point of view, although there was an evolution of the microbiome in the peri-implant sulcus towards Socransky's red circle pathogenic bacteria, no microorganism showed a significant correlation with the radiographic changes produced in the peri-implant bone over time.

Trial registration: ClinicalTrials.gov identifier: NCT03059108.