Peri-implantitis is the major reason for late failure [13, 14]. The consensus report of the Sixth European Workshop on Periodontology described peri-implant mucositis in approx. 80% of subjects restored with implant, and peri-implantitis in 28–56% of subjects [15]. In the present study, the cumulative incidence of peri-implantitis was 9.5, 15.3, 21.0, and 27.9% at 5, 10, 15, and 25 years after the prosthesis setting, respectively. Derks and Tomasi reported a positive relationship between the incidence of peri-implantitis and the mean function time by performing a meta-regression analysis of a systematic review [16], whereas the current cumulative result shown in Fig. 3 may represent the time course of the peri-implantitis incidence. Interestingly, the incidence of the peri-implantitis increased gradually with time; the rate of increase was approx. 1–1.5% per year.

Many potential factors associated with the incidence of peri-implantitis were reported [17, 18]. In the present study, the gender, implant type, and width of keratinized mucosa were identified as risk factors. Regarding gender, Koldsland et al. also reported a male population with overt peri-implantitis [19], whereas Attard and Zarb reported that women experienced more peri-implant bone loss than men [20]. Other studies and reviews reported that gender had no effect on peri-implantitis [21, 22]. Some other gender-related factors might affect the results.

Regarding implant type, a difference between the S-types and the TPS-types is whether the existence of an abutment connection or not. The TPS-types are one-piece implants, and the S-types are two-piece but one-stage implants. Duda et al. reported that one-piece implants showed more marginal bone loss than two-piece implants [23]. In addition, a TPS surface is classified as “rough” surface when the surface roughness is more than 2 μm (Sa > 2 μm) [24]. Teughels et al. reported that a transmucosal implant surface with higher surface roughness facilitates biofilm formation [25] and thus TPS-type implants showed a higher incidence of peri-implantitis compared to the S-type.