Association of Global DNA Methylation to Titanium and Peri-Implantitis: A Case-Control Study

Introduction: Epigenetic changes are associated with various inflammatory diseases and are influenced by environmental factors. Recent data support all association between titanium dissolution products and peri-implantitis. We hypothesize that site-specific changes in gene methylation, a form of epigenetic regulation, around dental implants may be influenced by local environmental factors, such as titanium dissolution particles. Objectives: The primary purpose of this study was to assess global methylation patterns related to the disease status of dental implants and the concentration of titanium particles. Methods: We assessed peri-implantitis cases defined according to established definitions from a cross-sectional study that had implants in function for at least 2 y. Controls were sampled from the same population and had healthy implants. Peri-implant crevicular fluid samples were collected and prepared for immunohistochemical analysis of 5-methylcytosine (5mC), and submucosal plaque samples were collected and subjected to inductively coupled plasma mass spectrometry (ICP-MS) for measuring titanium. Data were analyzed via generalized estimating equation models to account for multiple implants per participant. Results: Forty participants were included; 21 implants with peri-implantitis and 24 healthy implants were included in the analysis. Epigenetic alterations in global gene methylation were significantly more pronounced in peri-implantitis cases as compared to controls (P = 0.002). Adjustment for smoking status further strengthened the association (P = 0.0079). Higher adjusted titanium quantities had significantly higher 5mC (p<0.001). Conclusions: Peri-implantitis cases exhibited increased levels of methylated DNA cytosine (5mC) as compared to controls, suggesting that peri-implantitis is associated with epigenetic alterations in the peri-implant tissues. In addition. the finding that titanium concentrations were associated with global methylation levels independent of peri-implantitis status suggests that methylation may be affected by titanium dissolution products. Collectively, these results support further investigations to determine if these associations are causal or ecological in nature. Knowledge Transfer Statement: These are the first human data to elucidate the epigenetic regulation of gene transcription via hypermethylation as a potential mechanism involved in peri-implantitis. Furthermore, they identify titanium dissolution products as a potential environmental factor associated with this hypermethylation, which provides cues for novel therapeutic targets for peri-implantitis.