The effect of the interproximal contour of single external hexagon implant restorations on the prevalence of peri-implantitis: A retrospective study

Purpose: The objective of this retrospective study was to evaluate the effect of the interproximal contour of single external hexagon implant restorations on the prevalence of peri-implantitis. Material and Methods: Records of 96 patients and 148 external hexagon (EH) implants with time in function ranging from 1 to 17 years were included in the study. The most recent clinical and radiographic data were collected from records and the prevalence of peri-implantitis was defined according to the 2017 World Workshop on the Classification of Periodontal and Peri-implant Diseases and Conditions. Marginal bone level (MBL), emergence angle (EA), emergence profile (EP), and crown/implant platform horizontal ratio (CIHR) were obtained from periapical radiographs. Dichotomous variables at the patient- and implant level were compared with association tests. Mann-Whitney U-Test was performed to compare continuous quantitative values between the studied groups. Binomial logistic regression was conducted to identify risk indicators associated with the peri-implantitis event at the patient- and implant level, with the significance level set at 5% for all tests. Results: Nineteen patients (19.2%) and 24 implants (16.2%) with a mean time in function of 5.0 +/- 4.7 years were classified as having peri-implantitis. No statistically significant differences concerning gender, mean age, implant location in the jaw, or time in function were observed between patients with or without peri-implantitis (p > 0.05). Of 24 implants with peri-implantitis 10 (41.7%) displayed EA <= 30(degrees) (16.4%) while 14 (58.3%) presented EA > 30(degrees) with no statistical difference between the groups (p > 0.05). No statistically significant associations were identified between EA, EP, or CIHR and the prevalence of peri-implantitis. Conclusion: The findings seem to indicate that the EA, EP, and CIHR of single restorations over external hexagon implants are not associated with the presence of peri-implantitis. However, prospective studies with larger samples are required to better ascertain such an association in the long term.