Background: Dental implants are one of the most frequently used medical devices for therapeutic purposes in dentistry. Peri-implantitis is a severe, microbial biofilm-associated condition, characterized by inflammation in peri-implant soft tissues and destruction of supporting bone. It has been suggested that metal particles originating from the implant may influence the local host response to microbial biofilms.

Methods: Soft tissue biopsies were collected from implant sites with and without peri-implantitis in 21 patients. Micro Proton-induced X-ray Emission (mu -PIXE) analysis was used to localize, quantify and characterize titanium micro-particles within tissues. RNA sequencing was performed to evaluate potential associations between titanium micro-particles and gene expression profiles in peri-implantitis lesions.

Results: Titanium micro-particles are consistent findings in soft tissues surrounding dental implants. Their occurrence varies across patients but not between sites with and without peri-implantitis within the same individual. Most particles reside in a 2-mm wide tissue portion close to the implant/tissue interface. The time in function of the implants does not influence the volumetric density of titanium micro-particles, while implant systems do. Fourteen differentially expressed genes are identified when comparing peri-implantitis samples with high and low densities of titanium micro-particles. The gene-set enrichment analysis reveals functions related to the regulation of the immune response and epithelial development.

Conclusions: The present results indicate that titanium micro-particles are commonly found in tissues surrounding dental implants and are not associated with the occurrence of peri-implantitis.