CLEANING AND STERILIZATION EFFECT ON THE TORSIONAL PROPERTIES OF PROTAPER ROTARY TITANIUM COBALT (Ti-C0) ENDODONTIC INSTRUMENT

This study was conducted to evaluate the effect of the number of cycles of cleaning using NaOCl solution of different concentration and sterilization using autoclave and dry heat oven on the torsional properties of rotary (Ti-Co) instruments. A total of forty five rotary protaper finisher instruments were divided into 3 groups: Group 1 were subjected to neither cleaning nor sterilization cycles and assigned as the control group. Group 2 and group 3 were subjected to 5 and 10 cleaning and sterilization cycles respectively, soaked within (2% and 5%) NaOCl, were sterilized with autoclave and dry heat oven. Then, all instruments were subjected to a clockwise torsional load until fracture, the torsional moment and angular deflection at fracture were calculated. The results show a significant reduction in the torsional strength after cleaning and sterilization cycles regardless the concentration of NaOCl, type and number of sterilization cycles. For the angular deflection, there was a highly significant reduction, where, the number of cycles was the most influencing factor for reduction of the angular deflection whereas, theconcentration of NaOCl and the type of sterilization were show no significant influence on the angular deflection.