Influence of Optimum Torque Reverse Motion on Dentinal Cracks after Root Canal Preparation with Two Nickel-Titanium Rotary Systems.

OBJECTIVES

This study was aimed to evaluate the cause-effect relationship between canal preparation with ProTaper Next (PTN) and ProTaper Gold (PTG) using optimum torque reverse (OTR) motion or continuous rotation and dentinal crack formation.

MATERIALS AND METHODS

Fifty distobuccal roots of human maxillary first molars were divided into five groups; Group I: PTG Full rotation, Group II: PTG in OTR, Group III: PTN Full rotation, Group IV: PTN in OTR, Group V: unprepared (control group). After mechanical preparation, the distobuccal roots were sectioned horizontally at 3, 6, and 9 mm from the apex. Images were captured using a stereomicroscope at 25X to determine the presence or absence of dentinal cracks. Friedman test was used to compare between root sections followed by Wilcoxon signed-rank test for pairwise comparison. Kruskal-Wallis test was used to compare between tested rotary systems followed by pairwise comparison with Dunn Bonferroni correction (α = 0.05).

RESULTS

Crack development was significantly higher in PTG using OTR motion 36.7% followed by PTN using OTR 33.3%, while the control group showed no cracks. PTG and PTN with full rotation showed crack development with 23.3% and 13.3%, respectively.

CONCLUSIONS

The type of motion kinematics used during mechanical preparation have an impact on dentinal crack formation. Nickel-titanium instruments with larger taper tend to induce more cracks.