File:Dynamometer;The Dental cosmos (1912).jpg

Identifier: dentalcosmos5419whit (find matches)
Title: The Dental cosmos
Year: 1912 (1910s)
Authors: White, J. D McQuillen, J. H. (John Hugh), 1826-1879 Ziegler, George Jacob, 1821-1895 White, James William, 1826-1891 Kirk, Edward C. (Edward Cameron), 1856-1933 Anthony, L. Pierce (Lovick Pierce), b. 1877
Subjects: Dentistry Dentistry
Publisher: Philadelphia, S. S. White Dental Manufacturing Co
Contributing Library: Yale University, Cushing/Whitney Medical Library
Digitizing Sponsor: The College of Physicians of Philadelphia and the National Endowment for the Humanities

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ossible. It is unfortunate forour profession and for those whom weserve that so large a percentage of thedental alloys that are being offered on themarket at the present time are made bymanufacturers who base their knowledgeon the test of time, and are used by prac-titioners because of their supposedly easymanipulation. Such practice on the partof the manufacturers is far from scien-tific, and there is no excuse for profes-sional men using such materials, in viewof the knowledge which is within ourreach. One of the dearest and mostwidely advertised alloys was tested, and Ifound, during the first twenty-four hours,6/10,000 of an inch, or six points, ofshrinkage ; twenty points, or 20/1000 ofan inch of flow, which is nearly one-fourth 176 THE DENTAL COSMOS. its volume, and an average strength of obtained only when the metals are corn-only 236 pounds. Such shrinkage is ab- bined chemically in the ratio of theirsolutely fatal. The flow is ten times chemical equivalence. The claim has been
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more than it should be, and the strengthonly two-thirds as much. THE CHEMICAL THEORY OF ALLOYINGM ETAL8. The chemical theory is based on thebelief thai the best dental alloys can be made that this procedure will furnish••; combination which will best resist theaction of Ihe oral fluids on the surface ofthe filling, but this seems an unimportantitem a.s compared with the movementsand changes of a filling within Ihe cavityitself. The dissolving of metals in each MCCAULEY.—AMALGAMS. 177 other in such proportions that movementsin one will exactly counteract movementsin the other will produce a mass which is Fig. and flow, and is also lacking in strength.One investigator who has done a greatdeal of work in this field for rnanv years 2.

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