The initial bone level differed significantly (p = 0.05) between both groups with a median value of 5.69 mm in the study group and 3.87 mm in the control group (Fig. 4). A Mann-Whitney-U-Wilcoxon test revealed no significant difference between bone level postoperatively (p = 0.7851; median value control group 17.40 mm; median value perforation group 16.91 mm), in follow-up (p = 0.2238; median value control group 13.88 mm; median value perforation group 13.31 mm), or for bone resorption (p = 0.9455, median value study/perforation group 3.45 mm; Fig. 5). The data are further summarized in Table 3.

Groups were further subdivided and separated at an initial bone level of 4 mm, above which the sinus lift procedure is considered a relative indication for achievement of primary stability [16]. Regarding the height of augmented sinus floor postoperatively, a multiple comparison analysis revealed a significant difference between the groups. The adjusted p values of multiple comparisons are depicted in Table 4. Interestingly, only two group comparisons revealed a relevant difference. Multiple comparisons of bone resorption in subgroups did not reveal a statistically significant difference (p = 0.1418).

Fisher’s exact test revealed a statistically significant difference of proportions of one-stage versus two-stage procedures due to the presence of perforation (p = 0.0003; Table 5) and a significantly higher trend for peri-implantitis in patients with perforation (p = 0.0004; Table 6).