Endodontic shaping performance and muscular loads using different handle-material files

Objectives: To evaluate different file handle materials affect the shaping performance and muscular loads in simulated curved canals by dental students. Methods: Plastic- and silicone-made handle of files were used: K-flex file (Kerr, Sybron Endo, Sybron Dental, Orange, CA), Senseus FlexoFile(Dentsply, Maillefer, Ballaigues, Switzerland). Sixteen dental students prepared the simulated 40° curved canal resin blocks (Dentsply, Maillefer, Ballaigues, Switzerland) which were fixed in the left lower anterior incisal area and first molar area in the typodont of dental simulation units (KaVo Dental GmbH, Bismarckring, Germany) using watch and wind motion. Flexor pollicis brevis muscle, flexor carpi radialis muscle, and brachioradialis muscle were tested by surface electromyography. The preparation time, % MVC of the three muscles, and the shaping performance in the middle and apical third of the simulated canals were recorded. Data were collected and statistical analyzed. Results: The preparation times in the anterior teeth were 3 min 31 sec using K-flex file, 4 min 20 sec using Senseus FlexoFile; in the posterior teeth were 3 min 31 sec using K-flex file, 3 min 42 sec using Senseus FlexoFile. The % MVC of flexor pollicis brevis muscle was significant larger than the flexor carpi radialis muscle, and brachioradialis muscle (p<0.05) using both types of files. Sensus files revealed less %MVC than K-Flex file but having no significant difference. The shaping performance was no significant different at the apical and middle third of the simulated curved canals between the two types of files or the two tooth location. Conclusions: The flexor pollicis brevis muscle was the most contributing in watch and wind motion. The silicone handle (Senseus FlexoFile) showed less muslce load in canal preparation using watch and wind motion by the dental students.This research was supported by China Medical University (CMU-95-90).