The RTV data were normally distributed (Shapiro-Wilk test). The mean RTVs (N cm) of all groups are shown in Table 1. The RTVs in all groups decreased. The mean initial RTV of the control group was 27.67 N cm, a decrease of 7.78% compared to the insertion torque. After mechanical cyclic loading, all experimental groups from 50,000 to 2,000,000 cycles of loading showed significant decreases in mean RTVs when compared with the initial RTVs (P < 0.05) (Table 2). Similar results were found from 50,000 cycles to 1,800,000 cycles but without significant differences (P > 0.05). The statistically significant reductions of RTVs were found at 2,000,000 cycles (P < 0.05) (Table 3, Fig. 8). The comparison of the mean RTVs among groups are shown in Table 3. Although decreases in RTVs were observed in all groups, no screw loosening occurred.