Dynamic torque analysis of rotary and reciprocating instruments during root canal instrumentation in simulated canals by an endodontist or a general dentist

BACKGROUND: Excessive torque is associated with engine-driven file fracture. AIMS: The aim of this study to evaluate the real-time torque of rotary and reciprocating instruments, working time, and the occurrence of procedural errors during root canal preparation of simulated canals by an endodontist and a general dentist. METHODS: Thirty-six commercially available simulated “J-shaped” root canals in resin blocks were used. Instrumentation was performed using WaveOne, WaveOne Gold, ProTaper Next, Reciproc, Reciproc Blue, and Mtwo. The real-time torque analysis and the number of times the maximum torque applied to the instrument were evaluated. Images were obtained to assess the occurrence of procedural errors, and working time was recorded. STATISTICAL ANALYSIS: The one-way analysis of variance with a Bonferroni post hoc test, Mann Whitney test and the t-test was used for statistical analysis (P < 0.05). RESULTS: Reciprocating instruments showed lower values in the number of times that reached maximum torque and percentage time in the area of critical torque, with significant differences compared to rotary instruments (P < 0.05). Operators influenced torque values only with rotary motion instruments. There was no significant difference in mean working time between the operators or instruments. No fracture of instruments or canal transportation occurred. CONCLUSIONS: Rotary instruments were associated with higher peaks in real-time torque variation during the preparation of simulated root canals.