A friend was reading some of the blog postings on endodontics and sent this along to share. I include it because the YOUTUBE is in Spanish and yet, it still speaks volumes.
Interesting article for your perusal…http://www.slideshare.net/kendo160/m4-handpiece
Gambarini G et al. Cyclic fatigue analysis of twisted file rotary NiTi instruments used in reciprocating motion - International Dental Journal March 19, 2012 Abstract Aim To evaluate the cyclic fatigue fracture resistance of engine-driven twisted file (TF) instruments under reciprocating movement. Methodology A sample of 30 size 25, 0.08 taper NiTi TF instruments was tested in a simulated canal with 60˚ angle of curvature and a 3 mm radius. During mechanical testing, different movement kinematics were used at a constant speed, which resulted in three experimental groups (each group n = 10). The instruments from the first group (G1) were rotated until fracture occurred. The instruments in the second (G2) and third group (G3) were driven under reciprocating movement with different angles of reciprocation. The time of fracture for each instrument was measured, and statistical analysis was performed using one-way analysis of variance followed by Tukey’s Honestly Significant Different test. Results Reciprocating movement resulted in a significantly longer cyclic fatigue life (P < 0.0001) when compared with continuous rotation. No difference was found between reciprocation 150° clockwise/30° counterclockwise (CW/CCW) and 30° CW/150° CCW. Conclusions The reciprocating movement was associated with an extended cyclic fatigue life of the TF size 0.25, 0.08 taper instruments in comparison with conventional rotation.