Studies that evaluate the peri-implant bone situation specifically in the Frialit 2 implant system were, among others, conducted by Krennmair et al. and Ricci et al. Krennmair et al. found a bone resorption of 1.4 ± 1.2 mm over their follow-up period [24], which compares to the results found in this study. Ricci et al. found a higher bone resorption of the crestal bone after a 5-year follow-up, being 2.17 ± 1.6 mm in average [25]. Noteworthy is the high percentage of implants showing a bone loss of more than 3 mm (28.6 %).

One possibility for the outlier values could be a peri-implant defect with less than three walls. These defects tend to have a lower chance of spontaneous healing [5].

When comparing the data sets in our study, there is no deviation from the range of measured tolerance being 0.5 mm for the medians or means among the two groups. The median value for the CBD lies significantly higher for the immediate implants compared to the median value for the control group at the time of insertion. One possible explanation could be the incongruity between the shape of the alveolus and the shape of the implant, thus resulting in a possibility of a contact point, between bone and implant, lying closer to the reference line and therefore showing a higher value for the CBD. The fact that the null hypothesis for the Wilcoxon test was rejected in the second year after prosthodontics could be a result of the assumption of the test. Since the test assumes two groups with distributions different from the normal distribution.

That immediate and non-immediate placements of Frialit-type implants can achieve similar results was reported by Perry and Lenchewski in 2003. Perry and Lenchewski reported on a similar survival rate for Frialit implants placed as immediate implants and in healed sites [26]. However, in his study, there was no radiographic evaluation of the surrounding bone situation.