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Influence of sterilization on the corrosion resistance of high speed dental handpieces
No full textBall bearings of high-speed dental handpieces were sterilized by various procedures and examined under scanning electron microscopy for evidence of corrosion. The metallic parts of ball bearings (rings and spheres), if not correctly lubricated, were dramatically corroded in chemical vapor and steam sterilizer. The nonmetallic parts (the retainers made of phenolic resins) appeared to be more sensitive to heat treatments, as revealed by the occurrence of darkening and embrittlement phenomena. In the absence of correct lubrication procedures, the performance of high-speed dental handpieces appears to be adversely influenced by sterilization, mostly in wet environments. On the other hand, daily maintenance that follows the manufacturer's instructions reduces and delays the damage to a great extent
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Caratteristiche semiconduttrici di strati passivanti formati su leghe Fe-Cr e sull'acciaio AISI 304
No full textPhotopotential measurements were used to determine the semiconducting properties of the oxide layers formed on Fe-Cr alloys and AISI 304 stainless steel. The oxide films were obtained by two different procedures: thermal oxidation in air, and anodic oxidation. On the basis of the results obtained, it is concluded that the photoeffects are due to two independent processes: (1) the photovoltaic one, which occurs within the surface oxide film, and (2) the photogalvanic, which is produced by the photodecomposition of the oxide itsel
Dental casting alloys : in vitro tarnish and corrosion
No full textFive dental alloys of various noble metal concentrations and one Pd-Cu alloy were examined for corrosion and tarnish resistance by means of anodic polarization curves in artificial saliva containing increasing amounts of sulphide. The electrochemical data were compared with the results obtained from immersion experiments in sulphide-rich solutions. Good agreement between the two kinds of measurement was found. Emphasis is given to the use of electrochemical tests (rapidly performed) in predicting the behaviour of dental alloys in aggressive solutions
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