Changes in the cutting efficiency of different types of dental diamond rotary instrument with repeated cuts and disinfection.
BACKGROUND
Cutting efficiency is one of the most important factors to consider when a specific dental diamond rotary instrument is selected. However, the selection of a dental diamond rotary instrument is based on clinical experience rather than any scientific evidence.


OBJECTIVE
The purpose of this study was to identify how the cutting efficiency of different types of dental diamond rotary instrument changed with repeated cuts and disinfection.


METHODS
Four types of diamond rotary instrument from 2 dental manufacturers (Shofu, Jin Dental) were investigated with a high-speed air-turbine handpiece. The groups were as follows: S cham group (n=10): chamfer design from Shofu; J cham group (n=10): chamfer design from Jin Dental; S thin group (n=10): thin tapered design from Shofu; J thin group (n=10): thin tapered design from Jin Dental. Changes in the cutting efficiency of diamond rotary instruments on glass ceramic blocks were measured after repeated cuts. Changes in cutting efficiency also were measured for 30 diamond rotary instruments, the same type as those used in group J cham after disinfection with ethylene oxide gas, immersion in solution, or autoclaving. One-way ANOVA, 2-way ANOVA, and repeated-measures ANOVA were used to identify differences in cutting efficiency, in total cutting efficiency, and change trend in cutting efficiency (α=.05). The Tukey honestly significant difference method was used for the post hoc tests. The principal metal components of the diamond rotary instruments were detected with x-ray spectrometry.


RESULTS
The mean (standard deviation [SD]) total cutting efficiency after 10 cuts in the 4 groups was in the following order: J cham group (0.210 ± 0.064 g/min) > S cham group (0.170 ± 0.064 g/min) > J thin group (0.130 ± 0.042 g/min) > S thin group (0.010 ± 0.040 g/min) (P<.05).The decrease in the cutting efficiency was greatest after the first cut. The cutting efficiency was not influenced by repeated disinfection.


CONCLUSIONS
The cutting efficiencies of diamond rotary instruments with different designs and particle sizes showed a decreasing trend after repeated cuts but did not show any change after various disinfecting procedures.
Chief, Dental Department, The Armed Forces Daegu Hospital, Daegu, Korea.
Jin-Hyuk
JH
Bae
Resident, Department of Prosthodontics, Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, South Korea.
Jaeyoung
J
Yi
Assistant Professor, Department of Periodontology, Dental Research Institute, School of Dentistry, Seoul National University, Seoul, South Korea.
Sungtae
S
Kim
Professor, Department of Prosthodontics, Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, South Korea.
June-Sung
JS
Shim
Professor, Department of Prosthodontics, Department of Prosthodontics, College of Dentistry, Yonsei University, Seoul, South Korea. Electronic address: kwlee@yuhs.ac.
Keun-Woo
KW
Lee
D002516:Ceramics / Q000737:chemistry; D019551:Dental Disinfectants / Q000737:chemistry; D003754:Dental High-Speed Equipment / Q000592:standards*; D003764:Dental Materials / Q000737:chemistry; D018130:Diamond / Q000737:chemistry*; D004203:Disinfection / Q000379:methods; D004867:Equipment Design; D005027:Ethylene Oxide / Q000737:chemistry; D006801:Humans; D007101:Immersion; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D013052:Spectrometry, X-Ray Emission; D013242:Sterilization / Q000379:methods; D013499:Surface Properties; D019246:Tooth Preparation / Q000295:instrumentation* / Q000592:standards
D019551:Dental Disinfectants; D003764:Dental Materials; D018130:Diamond; C023506:Glass ceramics; D005027:Ethylene Oxide