Table 4. Summary of reports on root and canal curvature.

Author	Year	Country	Ref.	Method	Sample size	Root/canal curvature
Rocha et al.	1996	Brazil	[19]	In vitro (clearing technique) assessment of root curvature	232	Mesial root: 73% distal, 17% straight
						Distal root: 8% distal, 12% mesial, 78% straight
Estrela et al.	2015	Brazil	[17]	CBCT (in vivo) assessment of canal curvature	200	92.7% curvature in the apical third, 73.2% curvature in the cervical third
Schäfer et al.	2002	Germany	[18]	CBCT (in vitro) assessment of canal curvature	50	58% to 76% of curved canals with 33° to 48° angles

CBCT, cone-beam computed tomography.