J Korean Acad Conserv Dent.  2005 May;30(3):184-192. 10.5395/JKACD.2005.30.3.184.

Lifetime and fracture patterns of NiTi rotary files in molars

• Kim JW
• Ahn BD
• Park SH
• Shin HJ
• Cho KM

• KMID: 2045244
• DOI: http://doi.org/10.5395/JKACD.2005.30.3.184

Abstract

Intracanal separation of the rotary files is a serious concern in modern endodontic practice. The objective of this study was to compare the life span and fracture patterns of three NiTi rotary files in molar teeth. Mesiobuccal roots of upper molar (n = 150) and mesial roots of lower molar (n = 150) were divided into three groups and each group was prepared with Profile, ProTaper, and K3 respectively. Every file was used until separation and/or deterioration of the cutting blade was happened, and then the number of canals to separation and/or unwinding were recorded. Radiographs and Scanning electon microscope (SEM) photographs were taken to evaluate the patterns of separation. The results were as follows : 1. There were no significant differences in numbers of canals to separation and/or unwinding among the groups. 2. Comparing between flaring files, K3 showed significant lower numbers of canals to separation and/or unwinding (p < 0.05), and there was no significant difference between shaping files 3. Separations of instruments were occurred at the midpoint of curvatures within the canals. 4. In SEM observations, ductile fractures were seen in most of cases, characterized by shallow dimples. Additional researches is needed to provide a new guideline that informs the appropriate number of times to use NiTi files.

Keyword

NiTi file; separation; Unwinding; SEM

MeSH Terms

Molar*
Tooth

Figure

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  Figure 1 SEM photographs of representative fracture surface. a: ProFile group b: ProTaper group c: K3 flaring group d: K3 shaping group

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  Figure 2 SEM photoghaph of representative cutting blade. Files shown are (from top to bottom): K3 #20/.06, new K3 #20/.06, ProFile #20/.06 and new ProFile #20/.06. Unwinding of K3 file was seen to the point of fracture.

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