Table 5.

Multivariate logistic regression analyses of the frequencies of non-single canal configurations in mandibular first premolars

Explanatory variables (test category/reference category)	Multivariate logistic regression analyses
	Non-single canal
	Odds ratio (95% CI)	P value
Sex (male/female)	2.281 (1.637–3.179)	< 0.001*
Age (per year)	0.988 (0.971–1.005)	0.156
Side (left/right)	0.987 (0.713–1.367)	0.939
DLRs in M1 s (yes/no)	1.539 (1.077–2.200)	0.018*

Complicated canals and C-shaped canals were categorized as non-single canal

*The significance level is P = .05