Statistical analysis
The data were presented as mean ± SD and statistical graphs were performed by the GraphPad Prism 9.0 (GraphPad Software Inc., San Diego, CA, USA). The normality of the data in each group was measured by the Shapiro-Wilk test. Statistical comparisons were performed by the one-way analysis of variance (ANOVA). Pain threshold data satisfied the assumptions of normality, variance, and sphericity, and repetitive measures ANOVA was used. LSD method was used as a post-hoc test.P < 0.05 was considered statistically significant.