Chi CW, Lai EHH, Liu CY, Lin CP, Shin CS. Influence of heat treatment on cyclic fatigue and cutting efficiency of ProTaper Universal F2 instruments.
J Dent Sci 2017;
12:21-26. [PMID:
30895019 PMCID:
PMC6395258 DOI:
10.1016/j.jds.2016.06.001]
[Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 06/06/2016] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND/PURPOSE
Heat pretreatment can improve the cyclic fatigue life of nickel-titanium (NiTi) instruments. This study evaluated the effects of two different heat treatments on the cyclic fatigue resistance and cutting efficiency of ProTaper Universal F2 files.
MATERIALS AND METHODS
The files were divided into three groups: no treatment (control), heat treatment at 400°C (HT400) and heat treatment at 600°C (HT600). The phase transformation of the files was evaluated by differential scanning calorimetry. In cyclic fatigue tests, the differences in file performance in four simulated canals among the three groups were assessed. The cutting efficiency was tested at four cutting portions (3 mm, 6 mm, 9 mm, and 12 mm) from the tip of the file.
RESULTS
Differential scanning calorimetry showed a prolonged phase transformation of the files only after 600°C treatment. At 3 mm cutting portion, 400°C heat-treated files had significantly better cutting ability than those in the control group. However, the files in the HT600 group had significantly lower cutting efficiency than those in the other two groups at the four tested positions. In the cyclic fatigue test, fatigue lives of the files after 400°C and 600°C treatment were prolonged from 2.1 to 2.8 times and from 1.7 to 5.5 times, respectively.
CONCLUSION
Although 600°C treatment increased resistance to cyclic fatigue, it reduced the cutting efficiency of the files. The 400°C treatment maintained the cutting ability and prolonged the cyclic fatigue life of the files. Therefore, for clinical use of ProTaper Universal F2 files, 400°C pretreatment is a better choice than 600°C pretreatment.
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