Measurement of dimensional stability of elastomeric impression materials by holographic interferometry

A technique for measuring changes in the dimensions of elastomeric impression materials is described. The technique involves using holographic interferometry to determine the rate of dimensional change on setting of the materials. The total change in dimension is found by integration with time. The sensitivity of the technique allows accurate determination of these quantities. Holography involves no direct physical contact with the test sample and more than one sample can be tested at the same time under the same conditions. In a preliminary investigation, the technique was applied to several classes of commercially available impression materials. The results are compared with those obtained by other techniques.