Changes in crestal bone level are well-documented in the literature. Bone remodeling is reported to take place between surgery and loading. The reported changes are generally around 0.5 mm [17, 27, 30] but can reach more than 1 mm [31] in randomized or observational trials. The present study is well in accordance with these findings with its bone remodeling of − 0.52 ± 0.55 mm. Nearly 45% of the implants were placed subcrestally. These are associated with a remodeling of the crestal bone to the level of the implant shoulder which may be an explanation for the initial mean bone loss [10, 32, 33]. From loading to 5-year follow-up, clinically stable crestal bone levels at the implant shoulder were documented (− 0.09 ± 0.43 mm). Stable bone level or bone gain was noticed for 76.7% of the implants between loading and 5-year post-loading. A total of 23.3% of the evaluated implants were noted with a bone loss (12.8% with a loss > 0.5 mm). This bone gain corresponds well with the randomized clinical trial from Donati et al. [34], where 52% of the implants showed a bone gain over a 5-year observation period. These results are also in accordance with the controlled clinical studies published by Messias et al. [27] and Ioannidis et al. [4] and by the clinical study of Wennström et al. [35]. Additionally, the present results are consistent with the preliminary 1-year results with the same implant system published by Moergel et al. [17]. The integrated platform switching of the implants might additionally contribute to the stabilization of the bone as reported in several studies [21, 22, 27, 36].

Further contributing factors for the good survival data and bone level maintenance might be the regular follow-up controls with radiographs and patients’ care (plaque control, bleeding on probing, etc.). This allows an early detection of any focuses of inflammation and regular oral hygiene instructions. A recent meta-analysis by Lin et al. [37] showed a correlation between supportive care and peri-implant health. However, within an observational setting, study participants might be more difficult to follow up, especially when they are satisfied with their restorations and without any severe complications; they might tend to omit the control visits. This stresses the absolute importance of an excellent collaboration and guidance of the patients by their dental practices in terms of their continuing follow-up after the abutments are set. The very low drop-out rate of 19% in this purely observational multicenter study is in accordance with the results of randomized clinical studies published by others [18, 38] and is probably due to the stringent follow-up programs of the individual centers.