Table 2.

Variables associated with isthmus

Independent variables	Isthmus	P value
Female(n(%))	101 (54.9)	0.839
Male(n(%))	97 (56.1)
Age (mean (SD))	37.06 (13.86)	< 0.001
Age (n(%))		< 0.001
< 20 years old	21 (75.0)
20–39 years	91 (66.4)
40–59 years	75 (52.4)
≥ 60 years	11 (22.4)
Separated distal-lingual root canal(n(%))	30 (41.1)	0.003
No Separated distal-lingual root canal(n(%))	168 (59.2)
Position right(n(%))	101 (53.2)	0.282
Position left(n(%))	97 (58.1)