Fatigue life of protaper next TM instruments, an in vitro analysis

Tese de mestrado, Medicina Dentária, Universidade de Lisboa, Faculdade de Medicina Dentária, 2014INTRODUCTION: Nickel-titanium instruments were introduced to facilitate canal preparation. Despite several advantages, instrument separation remains a major concern in Endodontics due to several factors. There are several systems of endodontic files and the purpose of this study was to characterize the cyclic fatigue of ProTaper Next TM instruments, and compare it to other rotary and reciprocating systems. MATERIAL AND METHODS: Twenty-four rotary nickel-titanium of the ProTaper Next TM system were used and analyzed in this study. The instruments were divided into three groups whether they were X1, X2 or X3 instruments. A mechanical device was used to simulate the root canal system with a radius of curvature of 4,7 mm and an angle of curvature of 45º. Each instrument was submitted to the test with a rotational speed of 300 rpm and a torque of 4 N cm. The testing time was registered with a digital chronometer until tip separation occured. Data obtained such as time to fracture, fracture length of the instrument tested and number of cycles to fracture were statistically analyzed by the non-parametric Kruskal-Wallis test. ProTaper Next X2 and WaveOneTM Primary data were analyzed with the t-student test for independent samples. Significance was set at the 95% confidence level. RESULTS: X1 instrument proved to be statistically significant more resistant to cyclic fatigue that instruments X3 and X2, respectively. DISCUSSION AND CONCLUSIONS: Compared with different rotary and reciprocating systems such as WaveOneTM, ProFile® and ProTaper Universal®, the ProTaper Next TM system suggests being less resistant to cyclic fatigue. During clinical practice, clinicians should be aware of the mechanical properties of the instruments chosen and take into account the lower resistance to cyclic fatigue of ProTaper Next TM files when compared to other instrumentation systems