Studies on Method for Measuring the Expansion of Dental Casting Investments : Part 1 On Method for Measuring the Expansion during Setting of Gypsum-bonded Investments

Abstract

The purpose of this investigation was to develop a new method for measuring expansion during setting of dental investments and to discuss the results obtained by this method.A modified casting flask lined with kaowool or asbestos and gypsum-bonded investments was used.In the measurements are made through a glass plate put on the flask, the obtained values of expansion during setting show wide variation.Furthermore, the values were also markedly affected by the exudation of excess water from the investment.Therefore, we used a modified metal cover instead of the upper glass plate and sealed the flask to a bottom glass plate using vaseline.These modifications markedly decreased the variation of experimental results.We also found that the variation was greatly influenced by the interval between mixing and pouring into flask.