| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1996: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1995: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
1. The Effect of Autoclaving on the Bearing of the Air-turbine Handpieces
Of the dental instruments there are special difficulties in the disinfection of dental air-turbine handpieces (THP). The difficulty exists in their complex, delicate mechanical structure, the cost of purchasing extra sets to fill the vacancy during disinfection cycles and shortening of their useful life by autoclaving procedure. The purpose of this study is to clarify the delicate mechanical structure of eight THPs, and to evaluate the change of characteristics of THPs after repeated autoclaving (121ﾟC,15min).
The results were as follows.
1) Each dearing was composed of a outer ring, a inner ring, seven or eight balls and a supporter for the bearing ball (retainer). There was large difference in shape and materials of the retainer between THPs.
2) The microscopic views indicated existence of some substances or many small holes in the surface of bearing part in all THPs, and some abrasion, or adhesion of the discolore
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d lubricating oil in soeme THPs. There was large difference in the damage of the bearing parts between THPs (Freedman's test)
3) The THP sound was collected relationship between the rotor speed and repetitive autoclaving procedure to clarify the effect of autoclaving on the mechanical characteristics of the THP.THP sound was collected by a microphone and recorded on the magnetic tape and its power spectrum was analyzed by Fast Fourier Transformation (FFT) program on a stored program computer. The spectra obtained after 100 cycles autoclaving were different in frequency and relative power strength of the maximum peak frequency (MPF) from those of initial condition in all the THPs. In some of the THPs, change of the MPF not depending on the rotor speed was observed, those changes indicated the existence of some deformation in the internal structure of the THPs, especially in the retainer.
The rotor sound is an useful clue to evaluate its mechanical condition.
2. The Effect of an Oxygen Plasma Treatment
Corrosion of carbon steel instruments and the decomposed bacterial substances remaining on the surface of the instruments have been the problem with autoclave. The purpose of this study was to investigate the effect of an oxygen plasma reactor (PR-31 YAMATO Sci. Co. Ltd).
1) When the power of 300 W was applied to the specimen contaminated by whole saliva (circa 10^4 to 10^6 CFU), all of the 25 cultures were negative.
2) The ashed effect on the metal plate covered with gelatin and water was examined. This specimen lost weight by plasma treatment.
3) The surface of the dental burs treated by 3 different methods (plasma treatment, steam heat and ary heat). The SEM views indicated that the plasma treatment of 100W for 10 min produced the cleanest surface. In conclusion, the oxygen plasma treatment was considered useful as a dental sterilizer. Less
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