歯牙酸蝕症に関する研究
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概要
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I. Tooth Erosion in a Dye Factory. 224 workers of a dye factory located in the suburbs of Tokyo were subjected to the oral examinations with a view to looking into the possible erosion of their teeth by the influence of acid which was involved in their operation. By use of a magnifying glass careful inspections of the early stage of acid erosion was also carried out. Although it was not easy to measure the exact amount of acid contained in the air, the author believes that fairly accurate estimations were obtained through combination of instant and continuous sampling. The rate of prevalence differs for different groups. Among those who are constantly exposed to the acid-poluted air, the rate is found to be over 90%. This rate of prevalence of acid erosion increase in proportion to the length of employment. The longer the years of employment, the more advanced the stage of erosion too. Anterior teeth are found to be more affected than posterior ones and the lower front teeth are much more affected than the upper front teeth. When the workers wear no gas-masks, they are placed in such conditions that their lower front teeth are directly exposed to the acid-poluted air passing through the mouth by inspiration. Therefore, the use of gas-masks is recommended as a means of protection against the acid erosion besides the protection of respiratory organs. II. Corrosive Mechanism of Teeth by Acids In order to see the mechanism of acid corrosion of teeth, the author investigated, ground sections of affected teeth by means of an electron microscope. As a result of these studies, the conclusion is that it is impossible to determine definitely whether the base of enamel rods or the intrarod substance is affected first in the erosive process. Calcium which has been liberated as a result of decalcification by erosion collects itself again on the dental surface to form crystal, thus serving as a protective larger against further erosion. III. Tolerance of Teeth in Inorganic Acids Extracted teeth were immersed in aqueous solutions of hydrochloric acid, sulphuric acid or nitric acid of different concentrations, for about eight hours respectively. pH at which acid erosions started was investigated under the electron microscopy. At the same time, another set of teeth had been exposed to the acid-polluted air and pH of the surface of those teeth was examined. Comparison of these findings indicates that the concentration of these acids should be kept under 0.08 mg/lit from the point of view of acid erosion prevention and maintenance of healthy air conditions. The maximum allowabe concentration of the acid from 0.007 to 0.03 mg/lit. as recommended by A.C.G.I.H. is also desirable as a proper security against the acid erosion of teeth in the exposure of any long period.
- 社団法人日本産業衛生学会の論文