Analysis Of The Effect Of Coronal Preflaring On Curved Canal Working Length

Objective: To determine whether canal working length (WL) is altered as a result of coronal preflaring (CP), to assess the correlation between the degree of angulation and the position of root canal curvatures and their influence on the comparative results between the pre- and post-CP and to compare the effect on WL change between by using Gates Glidden drills (GG drills) and the Sx file of ProTaper to CP.Methods: The 73 curved canals of 40 extracted molars were sorted by the degree of the curvatures as moderate (from over 5 to 25 degrees) and severe (over 25 degrees) and by the position of curvatures as median (the location of the curvature on the one-three middle of canal) and apical (the location of the curvature on the one-three of tip). The canals were divided into two similar groups having the approximative degree and position of curvatures: group 1, GG drills and group 2, ProTaper. The reference cusp tip and root-end were flattened to produce reproducible measurements. Then, CP was performed with GG drills in Group 1 and Sx file of ProTaper in Group 2. Measured and recorded the WL of each canal pre- and post-CP. Statistical analysis was performed using the Paired-Samples T Test, Independent-Samples T Test and Univariate analysis, respectively.Results: The WL decreased after CP in two groups (P<0.05). The mean decrease in WL for group 1 was 0.33mm and for group 2 was 0.30mm. There was no correlation between the WL decreased and the position of the root curvature, but there was significant correlation between the WL decreased and the degree of the root curvature(P<0.05). There was no significant difference in the effect on WL between group 1 and group 2 (P>0.05) .Conclusions: WL of curved canals decrease after CP. The more degree of the root curvature is, the more WL decreased occurs. There was no significant difference in the effect on WL change between using GG drills and Sx file of ProTaper to CP.