Clinical Parameters, Subgingival Microbiota, and MMP-8 Expression in Dental Implants and Homologous Teeth: Insights into Peri-Implant and Periodontal Health

Abstract

This study aimed to evaluate and compare clinical parameters, subgingival microbiota composition, and matrix metalloproteinase-8 (MMP-8) expression between dental implants and homologous teeth under healthy conditions, across distinct implant platform designs. A total of 47 patients contributed 79 implants and 79 homologous teeth. Clinical parameters, including probing depth (PD) and dimensions of keratinized mucosa (HKM, TKM, and WKM), were assessed. Subgingival biofilm samples underwent analysis by checkerboard DNA–DNA hybridization. Peri-implant and gingival crevicular fluid were collected for MMP-8 quantification. Results: Implants showed significantly increased PD and reduced keratinized mucosa dimensions compared with teeth. While overall microbial loads were comparable, the microbiological profiles differed: Actinomyces naeslundii I, Actinomyces oris, Prevotella intermedia, and Treponema denticola were detected at higher levels in teeth. Conversely, Prevotella nigrescens, Aggregatibacter actinomycetemcomitans A + B, and Selenomonas noxia were more prevalent in implants. High levels of Aggregatibacter actinomycetemcomitans A + B and Selenomonas noxia were observed in the External Hexagon (EH) group. Importantly, MMP-8 expression was approximately 29% higher in implants than in teeth (p<0.05), regardless of the implant platform design. MMP-8 levels correlated exclusively with crevicular fluid volume, but not with other clinical parameters. Dental implants differ from homologous teeth, presenting increased PD, reduced keratinized mucosa height (HKM), and distinct microbial compositions. Although total bacterial levels were similar, implants showed elevated MMP-8 levels compared with teeth, independent of implant platform, suggesting distinct biochemical activity even in clinically healthy sites.