Restor Dent Endod.  2012 May;37(2):104-109.

An evaluation of canal curvature at the apical one third in type II mesial canals of mandibular molars

• Yun HR
• Lee DK
• Hwang HK

Abstract

OBJECTIVES
The purpose of this study was to evaluate the buccolingual curvature at the apical one third in type II mesial canals of mandibular molars using the radius and angle of curvature.
MATERIALS AND METHODS
Total 100 mandibular molars were selected. Following an endodontic access in the teeth, their distal roots were removed. #15 H- or K-files (Dentsply Maillefer) were inserted into the mesiobuccal and mesiolingual canals of the teeth. Radiographs of the teeth were taken for the proximal view. Among them, type II canals were selected and divided into two subgroups, IIa and IIb. In type IIa, two separate canals merged into one canal before reaching the apex and in type IIb, two separate canals merged into one canal within the apical foramen. The radius and angle of curvature of specimens were examined.
RESULTS
In type II, mean radius of curvature in mesiolingual and mesiobuccal canals were 2.82 mm and 3.58 mm, respectively. The radius of the curvature of mesiolingual canals were significantly smaller than that of mesiobuccal canals in type II, and especially in type IIa. However, there were no statistically significant differences in radius of curvature between mesiobuccal and mesiolingual canals in type IIb and there were no significant differences in angle of curvature between type IIa and IIb.
CONCLUSION
In this study, type II mesial canals of mandibular molars showed severe curvature in the proximal view. Especially, mesiolingual canals of type IIa had more abrupt curvature than mesiobuccal canals at the apical one third.

Keyword

Angle of curvature; Mandibular molars; Radius of curvature; Type II canal

MeSH Terms

Molar
Radius
Tooth
Tooth Apex

Figure

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  Figure 1 The proximal radiographic views of type II mesial canals of mandibular molar. (a) It shows type IIa mesial canals of mandibular molar; (b) It shows type IIb mesial canals of mandibular molar.

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  Figure 2 Technique used for determining the radius and angle of curvature in the proximal view. (a) Technique used for determining the radius and angle of curvature in type IIa mesial canals of mandibular molars; (b) Technique used for determining the radius and angle of curvature in type IIb mesial canals of mandibular molars. To determine these parameters, a straight line (l1 or l'1) is drawn along the long axis of coronal portion of the canal. A second line (l2 or l'2) is drawn along the long axis of the apical portion of the canal. There is a point on each of these lines at which the canal deviates to begin (point a1 or a2) or end (point b1 or b2) the canal curvature. The curved portion of the canal is represented by a sector with tangents at points a1 (or a2) and b1 (or b2). The angle of curvature (α1 and α2) is angle formed by perpendicular lines drawn from the points a1 (or a2) and b1 (or b2) that intersect at the center of sector (c1 or c2). The radius of curvature (γ1 and γ2) is the length of the radius of the sector measured in millimeters. a1 or a2, a point on each of lines at which the canal deviates to begin; b1 or b2, a point on each of lines at which the canal deviates to end; c1 or c2, center of sector; l1 or l'1, line along the long axis of coronal portion of the canal; l2 or l'2, line along the long axis of the apical portion of the canal; α1 and α2, the angle of curvature; γ1 and γ2, the radius of curvature. This figure was partly modified with permission from the original one of Pruett et al.18

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  Figure 3 Radius and angle of curvature in Type IIa and IIb. In type IIa, radius of curvature of MLs were significantly smaller than MBs (p < 0.05). However, there were no statistically significant differences in radius of curvature between mesiobuccal and mesiolingual canals in type IIb and there were no significant differences in angle of curvature in type IIa, IIb. ML, mesiolingual canal; MB, mesiobuccal canal. *A significant difference was found between radius of ML and MB (p < 0.05).

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