its best a filling made with silicate cement does n o t hold up well in the mouth and cannot be regarded as a permanent t o o t h restoration.
Field f o r Study in Dental Cements There is y e t much to b e learned of the chemistry and physics of dental cements. The cements that are available today do not possess nearly all the properties desired by the dentist. What these desirable properties are m a y be summarized as follows: Permanency and insolubility in the fluids of the mouth. Constancy of volume. Resistance to stress. Adhesion. Density and non-porosity. Suitable rate of setting. Color and translucency to match tooth shades. Absence of toxic action on the pulp of the tooth. "Hydraulicity" or the ability to set in the presence of moisture. Ease of manipulation.
It is likely that some of these dental requirements will b e difficult to meet. But t h e dentist is confident that the chemist will continue to study dental cements and eventually give h i m a formula that will answer most if n o t all his requirements. The dentist's greatest problem has always been that of finding satisfactory materials for restoring t e e t h and with the aid of t h e chemist his problem is on the w a y to satisfactory conclusion.
Seek to Simplify Production of Insulin. A new and simpler way of making insulin, the great boon to diabetics, may result from studies now being made. Prof. John J. Abel, who was the first to make pure crystalline insulin, reported recently to members of the American Association for the Advancement of Science that probably only a part of the complex insulin molecule is responsible for the action of the substance. In that case, it will probably not be necessary to build up the whole complex structure in order to get an active compound. Prof. Abel and Dr. H. Jensen of the Johns Hopkins School of Medicine are now studying the chemical composition and structure of insulin, which is a substance secreted by the pancreas which acts to regulate the body's utilization of sugar. Lack of insulin results in the disease known as diabetes. Drs. Banting, MacLeod, Collie, and Best of the University of Toronto were able t o prepare a pancreatic extract which contained insulin and was effective in treating diabetes. Prof. Abel and associates later succeeded in synthesizing the aystalline insulin. Insulin is of protein nature. "The outstanding characteristic of crystalline insulin in comparison with other proteins is its high sulfur content (3.1 t o 3.2y0) and its instability toward alkali," said Prof. Abel. Crystalline insulin has a very powerful action. The average daily dosage of insulin given t o a patient suffering from diabetes would correspond to 1 mg.. or about one-hundredth of a grain, of crystalline insulin.-Science Senice
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