The purposes of this study were to compare the apical terminus width of simulated curved root canal prepared with three NiTi file systems used by undergraduates for evaluation the effects of flute angle and pitch or radial land on reducing screw-in effect and to determine more safe NiTi file system for inexperienced operators.

Fifty inexperienced undergraduate students prepared 150 simulated curved root canals in resin blocks with three NiTi file systems ; ProFile®, Hero Shaper®, K3™. The electric motor set at a speed of 300 rpm and torque of 30 in a 16 : 1 reduction handpiece was used. The simulated root canal was prepared to ISO #25 sizes with each file system. The scanned images of pre- and post-instrumented canal of resin block were superimposed. To evaluate the screw-in effect of three NiTi file systems, apical terminus width of root canal was measured from superimposed images and statistical analysis was performed.

There were significant differences in three NiTi file systems. ProFile® had significantly smaller width than Hero Shaper® and K3™ (P < 0.05), but no significant difference was observed between K3™ and Hero Shaper®.

Under the condition of this study, active file system (Hero Shaper®, K3™) with variable pitch and helical angle had more screw-in effect than passive file system (ProFile®) with constant pitch and helical angle. It seems that the radial lands play more important role in reducing screw-in effect.

Citations

Citations to this article as recorded by  

• Mechanical and geometric features of endodontic instruments and its clinical effect
  Hyeon-Cheol Kim
  Journal of Korean Academy of Conservative Dentistry.2011; 36(1): 1.     CrossRef
• Comparison of screw-in effect for several nickel-titanium rotary instruments in simulated resin root canal
  Jung-Hong Ha, Myoung-Uk Jin, Young-Kyung Kim, Sung-Kyo Kim
  Journal of Korean Academy of Conservative Dentistry.2010; 35(4): 267.     CrossRef
• Influence of taper on the screw-in effect of nickel-titanium rotary files in simulated resin root canal
  Hye-Jin Sung, Jung-Hong Ha, Sung-Kyo Kim
  Journal of Korean Academy of Conservative Dentistry.2010; 35(5): 380.     CrossRef
• Influence of root canal curvature on the screw-in effect of nickel-titanium rotary files in simulated resin root canal
  Ji-Young Son, Jung-Hong Ha, Young-Kyung Kim
  Journal of Korean Academy of Conservative Dentistry.2010; 35(5): 374.     CrossRef

This study compared the shaping ability of nickel-titanium rotary files with different rake angle and radial land.

The nickel-titanium files used in this study were Profile(Dentsply, Maillefer, Ballaigues, Switzerland), Hero 642(Micromega, Besancon, France), and K3(SybronEndo, Glendora, Ca, USA) file. Resin blocks substituted for root canals. 36 resin blocks were divided into 3 groups with 12 canals each. The time for canal preparation was recorded. The images of pre- and postoperative resin canal were scanned and those were superimposed. Amounts of canal deviation, total canal widths, inner canal widths, and outer canal widths were measured at apical 1, 2, 3, 4, 5, 6, and 7mm levels.

The amount of canal deviation was the smallest in Profile group, and the time for canal preparation was the shortest in Hero 642 group. K3 group resulted in competent characteristics in both measurements. Positive rake angle seemed to result in fast shaping of root canal and radial land guide the instrument in center of the canals and around curvatures. Radial land also tended to reduce the sense of screwing into the root canal.

The proper selection of the nickel-titanium file based on the knowledge about file design is needed for the safer, simpler and faster root canal therapy.

Citations

Citations to this article as recorded by  

• Comparison of screw-in effect for several nickel-titanium rotary instruments in simulated resin root canal
  Jung-Hong Ha, Myoung-Uk Jin, Young-Kyung Kim, Sung-Kyo Kim
  Journal of Korean Academy of Conservative Dentistry.2010; 35(4): 267.     CrossRef
• Influence of root canal curvature on the screw-in effect of nickel-titanium rotary files in simulated resin root canal
  Ji-Young Son, Jung-Hong Ha, Young-Kyung Kim
  Journal of Korean Academy of Conservative Dentistry.2010; 35(5): 374.     CrossRef
• Comparison of shaping ability using various Nickel-Titanium rotary files and hybrid technique
  Jung-Won Kim, Jeong-Kil Park, Bock Hur, Hyeon-Cheol Kim
  Journal of Korean Academy of Conservative Dentistry.2007; 32(6): 530.     CrossRef
• Comparison of shaping ability of rotary Ni-Ti file systems used by undergraduates
  Mun-Seong Kang, Hyeon-Cheol Kim, Bock Hur, Jeong-Kil Park
  Journal of Korean Academy of Conservative Dentistry.2006; 31(1): 1.     CrossRef
• Comparative study on morphology of cross-section and cyclic fatigue test with different rotary NiTi files and handling methods
  Jae-Gwan Kim, Kee-Yeon Kum, Eui-Seong Kim
  Journal of Korean Academy of Conservative Dentistry.2006; 31(2): 96.     CrossRef
• Comparison of shaping ability between various hybrid instrumentation methods with ProTaper
  Eun-Sook Hong, Jeong-Kil Park, Bock Hur, Hyeon-Cheol Kim
  Journal of Korean Academy of Conservative Dentistry.2006; 31(1): 11.     CrossRef