No failure occurred as none of the tested crowns or implants was fractured or loosened during or after CS.

The tested crowns showed a maximum wear depth of M = 0.31 ± 0.04 mm (mean ± SD) and volume wear of M = 0.74 ± 0.23 mm³ (mean ± SD). Table 2 shows the mean and standard deviation of assessed parameters (pull-out forces, maximum wear, volume wear) of each round of CS. Abrasion was macroscopically observed.

The Kolmogorov-Smirnov test and a visual inspection of the histograms and the quantile-quantile plot showed no significant divergence from the normal distribution in any of the groups (maximum wear depth after CS, volume wear after CS, pull-off forces without and after CS).

One-way ANOVA showed differences neither in pull-out forces F(3,16) = 0.02, p = 0.997, nor in maximum wear F(3,15) = 0.39, p = 0.764, or volume wear F(3,15) = 0.77, p = 0.530, among the four rounds of CS (Table 3), thereby demonstrating stable and comparable conditions within all rounds of CS.

In the pull-out tests, the crowns from the control group were removed from the implants at a 1.8 times higher load (M = 588.4 ± 57.7 N) than the crowns of the experimental group (M = 322.8 ± 61.9 N). Therefore, the bond strength of the control group was significantly higher than the bond strength of the experimental group (t(23) = 8.69, p < 0.001). Table 4 shows the resulting characteristics of PICN crowns on one-piece zirconia implants.

Under the stereomicroscope, approximately 90% of the luting agent could be stereomicroscopically located in the crowns, not on the implants. Figure 4 shows the luting agent situated mostly in the crown (a) and only sparsely on the implant (b).

The crowns' surface of abrasion revealed avulsion and a rough surface under SEM. The polished surface and the surface of abrasion do not appear similar. Figure 5 shows SEM images of the mesial margin of abrasion under topography (a) and material contrast (b).