Cyclic fatigue of ProTaper Gold in single and double curvature canals

Objectives: This study aimed to evaluate and compare the fatigue resistance of ProTaper Gold (PG) and ProTaper Universal (PU) in artificial single and double curvature canals in 5% sodium hypochlorite (NaOCl) at body temperature. Methods: PG and PU files (size F1) were subjected to fatigue tests inside two different custommade ceramic artificial canals. The first one was a single curvature canal (group 1: 60° curvature, 5 mm radius) and the second was a double curvature canal (group 2: first [coronal] curve of 60° curvature and 5-mm radius and the second one [apical] of 30° curvature and 2 mm radius). The artificial canals were milled in an InCoris ZI zirconium oxide disc (Dentsply Sirona, Bensheim, Germany) using the inLab MC X5 Digital CAD/CAM System (Dentsply Sirona). The first 19 mm of each file tip was introduced into the artificial canal which was immersed in either distilled water or 5% NaOCl at body temperature (37oC). The total number of cycles to failure (NCF) was recorded, and the length of the detached fragments was measured. Data were analyzed using t-test and multiple linear regression analyses. Results: The fatigue performance of PG is better than that of PU (P<0.001) in all tested groups. The NCF of ProTaper files was significantly influenced by the type of file (β=0.854; P