Effect of Hand and Rotary Instruments on the Fracture Resistance of Teeth: An In Vitro Study.

Objective: Endodontic treatment should be both conservative and effective. Endodontic instruments with a greater taper are used for coronal flaring, for proper debridement with efficient irrigation. However, increased taper of an instrument can remove a larger amount of pericervical dentin, compromising the strength of the tooth. The aim of this study was to determine the effect of hand files, ProTaper Universal, ProTaper Next, and V Taper rotary instrument systems on the fracture resistance of teeth. Materials and Methods: In total, 60 extracted human maxillary first premolars were divided into four groups-Group I (Hand Files; HF), Group II (ProTaper Universal; PT), group III (ProTaper Next; PTN) and Group IV (V Taper; VT) (N = 15). Each group was instrumented with the respective instrument system, irrigated, obturated, restored, and mounted in cold cure acrylic. A universal load-testing machine (Shimadzu, Japan) was used to apply a vertical compressive load. The maximum force was recorded in Newton. Analysis of variance (ANOVA) and Independent t-tests were applied to compare the maximum mean force required to fracture the tooth. Results: There was a statistically significant difference in fracture resistance between Group I (HF) and Group II (PT) and between Group II (PT) and Group IV (VT) (p < 0.001). Similarly, a significant difference was observed between Group II (PT) and Group III (PTN) (p < 0.01). Furthermore, a significant difference was observed between Group I (HF) and Group III (PTN), and between Group III (PTN) and Group IV (VT) (p < 0.05), too. However, there was no statistically significant difference between Group I (HF) and group IV (VT) (p > 0.05). Conclusion: Rotary files with more taper seem to remove more pericervical dentin than traditional manual and rotary files with less taper, thus altering the strength of the tooth.