Table 1: Incidence of isthmus (Type IV and V) in maxillary permanent teeth at 3 mm level from the original apex.

Table 1: Incidence of isthmus (Type IV and V) in maxillary permanent teeth at 3 mm level from the original apex.

Tooth	Root	Author/year	Number of Teeth	Number teeth with Isthmus	% Total	%
First Premolar		Vinegas, et al. [13]	28	8	29%	29%
First Molar	MB	Weller, et al. [8]	50	19	38%	44%
		Vinegas, et al. [13]	22	3	14%
		Von Arx [14]	29	22	76%
		Degerness & Bowles [15]	90	50	56%
		Tonelli, et al. [20]	62	16	25.8%
	DB	Von Arx [14]	11	0	0%	0%
	P	Von Arx [14]	4	0	0%	0%

MB: Mesiobuccal; DB: Distalbuccal; P: Palatal