Comparing the medians (Fig. 9) of the IM and CG, a difference of 0.7 mm at the time of insertion is visible. The respective values were 0 mm for the CG and 0.7 mm for the IM group. While at the time the patients received their definite restorations, a difference of only 0.3 mm was recorded (0.9 mm for IM and 0.6 mm for CG).

Over the years after definite restorations were emplaced, the medians for both groups mainly lay between 1 and 1.7 mm, the difference mostly being less than 0.5 mm (Fig. 9).

In summary, the mean and the median values stayed stable over the follow-up years. Both groups showed a slight increase of the mean and median values from the beginning of the study until the eighth to tenth year and mainly ranged from 1 to 1.7 mm.

The upper quartiles of the CG showed a tendency for smaller values up to the third year after restoration, while later, that tendency was no longer detectable. For the lower quartile, there was no significant difference visible (Fig. 7).

Statistical tests, shown in Table 4, were carried out to compare the data sets. A statistically significant difference between the two data sets was found at the time of insertion in all three tests, and the second year after patients had received their restorations, a rejection of the null hypothesis for the Wilcoxon test could be observed.