Analysis of kinematic, kinetic and electromyographic patterns during root canal preparation with rotary and manual instruments

objective: this study assessed the muscular activity during root canal preparation through kinematics, kinetics, and electromyography (emg). material and methods: the operators prepared one canal with race rotary instruments and another with flexo-files. the kinematics of the major joints was reconstructed using an optoelectronic system and electromyographic responses of the flexor carpi radialis, extensor carpi radialis, brachioradialis, biceps brachii, triceps brachii, middle deltoid, and upper trapezius were recorded. the joint torques of the shoulder, elbow and wrist were calculated using inverse dynamics. in the kinematic analysis, angular movements of the wrist and elbow were classified as low risk factors for work-related musculoskeletal disorders. with respect to the shoulder, the classification was medium-risk. results: there was no significant difference revealed by the kinetic reports. the emg results showed that for the middle deltoid and upper trapezius the rotary instrumentation elicited higher values. the flexor carpi radialis and extensor carpi radialis, as well as the brachioradialis showed a higher value with the manual method. conclusion: the muscular recruitment for accomplishment of articular movements for root canal preparation with either the rotary or manual techniques is distinct. nevertheless, the rotary instrument presented less difficulty in the generation of the joint torque in each articulation, thus, presenting a greater uniformity of joint torques.