1,721,393 research outputs found
Old anatomical models as makeshifts of measurements in medicine
Full text linkIn 18th century obstetrics became a special branch of medicine, with a corpus of physiological and practical knowledge sufficient to improve the outcome of childbearing. The same period also saw the emergence of new techniques and the development of instruments that would later come into widespread use, such as the forceps, as well as the first production of teaching models to provide surgery students and midwives with three-dimensional illustrations of the anatomy of the pregnant woman, the physiology of childbearing, and potential complications. Some obstetrical wax models, that can be considered makeshifts of measurements in medicine, are illustrated. They are exposed, in number of twenty-one, in the Galileo Museum of Florence and were commissioned, around 1770, by Felice Fontana, who was working on the installation of the Museum of Physics and Natural History of Florence, from the sculptor Giuseppe Ferrini and his assistant Clemente Susini. The anatomical models contributed, in a context in which the measurement was not easy to be taken in situ, to formalize medical knowledge, strictly tied, in the past, to the various communities, that had different ideas about the causes of and cures for suffering, illness and disease. As a matter of facts, instead of being based on objective parameters, medical knowledge was based often on spiritual beliefs as well as practical therapies and techniques
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
PROMET state-of-the-art approach for protecting, preserving and interpreting metals from museum in the Mediterranean basin
No full textIn vitro corrosion of dental amalgams
No full textA series of dental alloys were characterized with respect to chemical composition, microstructure and corrosion resistance in artificial saliva. The following types of amalgams were studied: conventional and high copper dispersed phase dental alloys. Anodic polarization curves were recorded on these samples and periodic polarization resistance measurements were performed during a test of immersion in artificial saliva. The results are in accordance with extensive clinical findings, which attribute a greater corrosion resistance to the dispersion phase alloys. Examination by scanning electron microscopy and electron probe microanalysis allowed the identification of the various phases present on the amalgams and of the main corrosion products
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
- …
