Objectives To assess contour changes of peri-implant tissues comparing a one- and a two-piece dental implant system over 12 years. Materials and methods Patients seeking implant therapy were enrolled and randomly allocated to receive implants (a one-piece (STM) or a two-piece (BRA) system). Impressions were taken at the time of insertion of the final reconstruction (BL), after 1 year (FU-1), 5 years (FU-5), and at 12 years (FU-12). Thirty patients were included in the analysis (STM, 16; BRA, 14). Digital scans of casts were superimposed and analyzed in an image analysis program. Measurements included changes of the crown height, contour changes on the buccal side of the implants and the contralateral teeth (control). Results Contour changes at implant sites revealed a loss of − 0.29 mm (STM) and − 0.46 mm (BRA) during an observation period of 12 years. Contour changes at the corresponding tooth sites amounted to − 0.06 mm (STM) and − 0.12 mm (BRA) during the same time period. The implant crown gained 0.25 mm (STM) and 0.08 mm (BRA) in height due to recession of the marginal mucosa. The corresponding gain in crown height at the contralateral tooth sites amounted to 0.36 mm (STM) and 0.10 mm (BRA). Interproximal marginal bone level changes measured − 0.28 mm (STM) and − 1.11 mm (BRA). The mean BOP amounted to 38.8% (STM) and 48.7% (BRA) at the 12-year follow-up (FU-12). Conclusion Minimal changes of the peri-implant soft tissue contour were observed at implant sites over the period of 12 years irrespective of the use of a one- or a two-piece implant system. The differences between the implant sites and corresponding teeth were clinically negligible. Clinical relevance Peri-implant soft tissue stability is of high clinical relevance when monitoring dental implant sites on the long run. Clinical data on the extent of soft tissue changes around different implant systems are scarce. The present RCTs demonstrate minimal changes of the peri-implant soft tissue contour 12 years after implant insertion independent of the use of a one- or a two-piece implant system.

Background: Implant therapy is a well-documented and commonly applied treatment option. Survival rates of implant and the respective reconstructions are reported to be high over 10 years. From a clinicians' perspective, survival rates are not sufficient; therefore, further criteria were defined to assess the success of implant therapy. Among those, the stability of peri-implant hard and soft tissues is important to be monitored on the long-run. Aim/Hypothesis: To evaluate profilometric and contour changes of peri-implant tissues comparing a one-and a two-piece dental implant system over 12 years. Materials and Methods: Patients seeking implant therapy were enrolled and randomly allocated to receive implants (a one-piece (STM) or a two-piece (BRA) system). Impressions were taken at the time of insertion of the final reconstruction (BL), after one year (FU-1), 5 years (FU-5) and at 12 years (FU-12). Thirty patients were included in the analysis (STM: 16, BRA: 14). Stereolithography files were superimposed and analyzed in an image analysis program. Measurements at implant sites and the contralateral teeth included linear and profilometric changes of the peri-implant tissue contour, changes in crown height (recession) and marginal bone level changes. Results: Contour changes at implant sites revealed a loss of −0.29 mm (STM) and −0.46 mm (BRA) (within group comparison P = 0.0106, P = 0.0029; intergroup comparison P = 0.787) after an observation period of 12 years. Contour changes at the corresponding tooth sites amounted to −0.06 mm (STM) and −0.12 mm (BRA) (within group comparison P = 0.5534, P = 0.5016; intergroup comparison P = 0.755). The height of the implant crowns increased (recession) by 0.25 mm (STM) and by 0.08 mm (BRA) (within group comparison P = 0.126, P = 0.670; intergroup comparison P = 0.244). The corresponding figures at the contralateral tooth sites amounted to 0.36 mm (STM) and 0.10 mm (BRA) (within group comparison P = 0.006, P = 0.334; intergroup comparison P = 0.244). Marginal bone level changes were −0.28 mm (STM) and −1.11 mm (BRA) (within group comparison P = 0.0386, P = 0.002; intergroup comparison P = 0.0138). Conclusions and Clinical Implications: Peri-implant soft tissue stability is of importance when monitoring dental implant sites on the long-run. Minimal changes of the peri-implant soft tissue contour were observed at implant sites over the period of 12 years irrespective of the implant system. The differences between implant sites and corresponding teeth were clinically negligible.