After storage in 37��C distilled water for 2 months, each crown was sectioned buccolingually through the center of the crown with a diamond blade in an Isomet Saw (Buehler, Lake Bluff, IL, USA), resulting in two portions. One portion of each specimen was placed under a measuring microscope (Profile Projector V-16D, Perifosine Akt Nikon, Tokyo, Japan), with a measuring sensitivity of 1 ��m, under ��100 magnification. The thickness of the adhesive system, low-viscosity microfilled resin and resin cement was measured at 10 positions as shown in Figure 1. Thickness of the resin materials was measured in a direction perpendicular to the dentin surface at each position. Figure 1 Bucco-lingual section of the preparation.

The thickness of the resin cement, adhesive and low-viscosity microfilled resin were measured at 10 different positions along the preparation The final thickness of the resin materials (adhesive, low-viscosity microfilled resin and resin cement) at the different positions in each group was compared using the Friedman and Wilcoxon signed-rank non-parametric tests. The Kruskal-Wallis and Mann-Whitney U non-parametric tests were also used to compare the final thickness values between the groups in each position. Fracture loads were analyzed using the one-way analysis of variance, followed by Tukey’s multiple comparison tests. The correlation between fracture load and the thickness of the resin materials was analyzed by the Pearson correlation test. The significance level was set at 0.01.

RESULTS The mean film thickness of the adhesive, low-viscosity microfilled resin and resin cement in each position for the different groups is shown in Table 2 and in Figures Figures22�C4. The thickness of the resin cement was higher in positions 5 and 6 than in other positions. The thickness of adhesive was higher in positions 2 and 9 and lower in positions 1 and 10. Intermediate values were obtained in the other positions. The thickness of the low-viscosity microfilled resin was higher in positions 5 and 6 and lower in positions 1 and 10. Table 2 Mean thickness (��m) and standard deviation of the resin cement, adhesive and low-viscosity microfilled resin of the experimental groups in the different positions Figure 2 Group 1 – Mean thickness (��m) of the resin cement Figure 4 Group 3 – Mean thickness (��m) of adhesive, low-viscosity microfilled resin, and resin cement The sum of the resin materials in each position is presented in Table 3.

According to the Friedmann non-parametric test, statistically significant differences were noted between the positions (P < 0.01). In Group 1, a significantly higher resin cement thickness was obtained in positions 5 and 6. In Group 2 (adhesive + resin cement) and Group 3 (adhesive + low-viscosity microfilled resin + resin cement), significantly lower resin thickness values were obtained in positions 1 and 10. Intermediate values were found Carfilzomib in positions 2, 3, 7, and 8.