Fracture strength of roots instrumented with three different single file systems in curved root canals

OBJECTIVE The aim of this study was to compare the fracture strength of roots instrumented with three different single file rotary systems in curved mesial root canals of maxillary molars. MATERIALS AND METHODS Curvatures of 25°-35° on mesial roots of 60 maxillary molar teeth were sectioned below the cementoenamel junction to obtain roots 11 mm in length. The roots were balanced with respect to buccolingual and mesiodistal diameter and weight. They were distributed into three experimental groups and one control group (no instrumentation) (n = 15): Reciproc rotary file (R25, VDW, Munich, Germany), WaveOne Primary rotary file (Dentsply Tulsa Dental Specialties, Tulsa, UK) and OneShape (Micro-Mega, Besancon, France) rotary file. Vertical load was applied until fracture occurred. Data were statistically analyzed using one-way analysis of variance test (P < 0.05). RESULTS The mean fracture load was 412 ± 72 Newton (N) for the control group, 395 ± 69 N for the Reciproc group, 373 ± 63 N for the WaveOne group and 332 ± 68 N for the OneShape group. The fracture load differences among three experimental groups were not statistically significant (P > 0.05.) Whereas, the fracture loads of control and OneShape groups were significantly different (P = 0.012). CONCLUSIONS Fracture resistance of the roots instrumented with WaveOne and Reciproc file systems were similar to the control group whereas it was observed that OneShape rotary file systems enhance the fracture strength of standardized curved roots when compared with the control group.