Microbial communities of titanium versus zirconia abutments on implant-supported restorations: Biodiversity composition and its impact on clinical parameters over a 3-year longitudinal prospective study

Background: Shifts in microbial communities are common over time, but they may disturb the host-microbiome homeostasis and result in inflammation of the peri-implant issues if a dysbiotic biofilm is established. Purpose: Considering that different oral substrate surfaces may have a relevant impact on the microbial adhesion and colonization, the aim of this study was to investigate the microbial communities of the biofilm formed on single-implant restorations using titanium or zirconia abutments and how they correlate with clinical parameters after 3-years of implant loading. Materials and methods: MiSeq sequencing of 16S rRNA amplicons was used to characterize the oral biofilms of individuals (n = 20) who were sampled longitudinally during 3 years of masticatory loading. Bioinformatics analysis and multivariate statistical analysis were used to evaluate the microbial diversity and clinical outcomes. Results: Microbiomes of both abutment materials presented high alpha-diversity indices during all the experimental period, irrespective of the time of sampling. Microbial communities of titanium and zirconia were quite different over time, differing about 30% after 3 years of functional loading. Similarity of microbiomes between tested abutments and contralateral teeth was also low, ranging between 45% and 50% after 3 years of investigation. Periodontal pathogens commonly associated with peri-implantitis were found in both groups. Furthermore, both abutment materials presented strong correlations of diversity indices and microbial taxa with clinical outcomes. Conclusions: The type of abutment substrate significantly influenced diversity and clustering of communities during 3 years of functional loading. The time of sampling had no effect on the variables. Large correlations were found between microbial findings and clinical outcomes. (AU)