Journal of Jilin University(Medicine Edition) ›› 2021, Vol. 47 ›› Issue (4): 984-989.doi: 10.13481/j.1671-587X.20210423

• Research in basic medicine • Previous Articles     Next Articles

Cyclic fatigue resistance of five kinds of thermally treated nickel-titanium instruments

Qingcui WU1,Yingyi WANG1,Ang MA1,Yiran LI1,Shan JIAO1,Chengkun WANG1(),Qiu JIANG2()   

  1. 1.Department of Endodontics,Stomatology Hospital,Jilin University,Changchun 130021,China
    2.Department of Pediatric Dentistry,Stomatology Hospital,Jilin University,Changchun 130021,China
  • Received:2021-01-06 Online:2021-07-28 Published:2021-07-22
  • Contact: Chengkun WANG,Qiu JIANG E-mail:wck1964@163.com;jiangqiu1221@163.com

Abstract: objective

To compare the cyclic fatigue resistance of five kinds of thermally treated nickel-titanium instruments(nickel-titanium files)Reciproc Blue(RB),M-Pro(MP),HyFlex CM(HCM),Orodeka Plex-2.0(OP) and P3-Blue(PB) with the same tip size, and to provide the reference for clinical selection of thermally treated nickel-titanium instruments.

Methods

Twenty new files were selected from RB(25/0.08),MP(25/0.06),HCM(25/0.06),OP(25/0.06)and PB(25/0.06). Each group was further divided into two subgroups with 10 files in each subgroup: RB group, HCM group, MP group, OP group and PB group under 60 ° bending simulated root canal and RB group, HCM group, MP group, OP group and PB group under 90 ° bending simulated root canal.The root canal motor was set according to the speed and torque recommended by the manufacturer.The flexural fatigue resistance of the nickel-titanium files was tested in the curved simulant canals which were made of stainless steel with an inner diameter of 1.5 mm, 60° and 90°angles of curvatures and a radius of curvature of 5 mm.The time from rotation to fatigue fracture (TTF) of each nickel-titanium file was recorded with a timer, and the length of the fracture segment (FL) was measured and recorded with a vernier caliper.After the experiment, the broken nickel-titanium files were collected, and scanning electron microscopic(SEM) evaluation was performed at the fracture sites to investigate the morphology of fracture.

Results

In 60 ° curved simulated root canals, the TTF of nickel-titanium file in RB group was the longest (P<0.05), followed by HCM group and MP group (P< 0.05), and OP group and PB group were the longest(P<0.05);there was no statistically significant difference in TTF between HCM and MP group(P>0.05), and there was no statistically significant difference in TTF between OP group and PB group (P>0.05).In 90 ° curved simulated root canals, the TTF of nickel-titanium file in RB group was the longest(P<0.05), followed by MP group (P<0.05),and HCM group, PB group and OP group were the lowest(P<0.05);there were no significant differences in TTF among HCM group, PB group and OP group (P>0.05).The TTF of nickel-titanium files in each subgroup in simulated root canal bending at 90° were significantly lower than those corresponding subgroups at 60° (P<0.05).There were no statistically significant differences in FL among all groups (P>0.05).The cross sections of nickel-titanium files in each group showed typical characteristics of cyclic fatigue including fatigue striations and fibrous dimples under SEM.

Conclusion

RB nickel-titanium file shows statistically higher cyclic fatigue resistance in artificial canals with 60° and 90° than the other nickel-titanium files.

Key words: cyclic fatigue resistance, nickel-titanium instruments, thermal treatment, curved root canal, instrument separation

CLC Number: 

  • R781.05