Date of Award
Summer 1962
Document Type
Thesis - Restricted
Degree Name
Master of Science (MS)
Department
Dentistry
Abstract
With the general acceptance of the casting technique by the dental profession more than half a century ago, there subsequently appeared many problems. One of the major problems encountered was that of dimensional reproducibility. Early dental castings exhibited different dimensions than those of the wax pattern. This resulted from volumetric shrinkage during cooling from solidification temperature to room temperature. After a long and concentrated effort this problem was partially overcome by the development of casting investments which expand during the hardening and during heating by setting, hygroscopic, and thermal expansion to compensate for the volumetric shrinkage of the gold alloys. In addition to the thermal contraction of gold alloy when it is cooled from the solidus temperature to room temperature, the gold alloy also contracts during its solidification. This shrinkage may result in porosity in the finished casting. Several types of porosity have been described in the literature, and the effect of various casting conditions on the porosity of dental gold alloys have been investigated by qualitative methods. Two main types of porosity have been described, namely (1) porosity due to solidification, and (2) gas porosity. It has been shown that the former type depends upon mold temperature and dimension (length anbd diameter) of the spruce or ingate. Limited information is available, however, as to the quantitative evaluation of the role of these factors, and it was, therefore, decided to attempt to devise a method which would yield numerical values to illustrate the effects on porosity of the above mentioned factors. In addition, it was decided to study the effect of surface area-to-volume ratio upon porosity. Determination of specific gravity was chosen as a suitable means for the quantitative analysis of porosity.
Recommended Citation
Leinfelder, Karl F., "Effects of Variation of Surface Area-to-Volume Ratio, Mold Temperature and Sprue Dimensions on the Specific Gravity of Dental Gold Castings" (1962). Master's Theses (1922-2009) Access restricted to Marquette Campus. 5271.
https://epublications.marquette.edu/theses/5271