Table 6.

Multinomial logistic regression analyses of the frequencies of complicated canals and C-shaped canals in mandibular first premolars

Explanatory variables (test category/reference category)	Multinomial logistic regression analyses
	Complicated canal		C-shaped canal
	Odds ratio (95% CI)	P value	Odds ratio (95% CI)	P value
Sex (male/female)	2.166 (1.520–3.087)	< 0.001*	3.039 (1.404–6.580)	0.005*
Age (per year)	0.991 (0.973–1.009)	0.324	0.969 (0.929–1.010)	0.136
Side (left/right)	1.042 (0.736–1.475)	0.817	0.740 (0.356–1.537)	0.419
DLRs in M1 s (yes/no)	1.376 (0.933–2.019)	0.107	2.616 (1.257–5.443)	0.010*

*The significance level is P = .05