Abstract
Hydrocolloid impression materials are often used in clinical practice. However, the materials may undergo chronological dimensional changes caused by loss of water because of their fluid nature.
Therefore, as an experimental material we used, reversible hydrocolloid impression materials which are often used when taking precise impressions of inlay and crown-bridge, and conducted the measurement with a scanning laser microscope to examine the chronological microdimensional changes, reproduced on a 20 μm detail line on the surface of the impression.
Thanks to the scanning laser microscope, microdimensional changes which appeared immediately after removal of the impression could be measured without touch, which had been considered impossible by previous methods of measurements.
The reversible hydrocolloid impression materials shrank chronically. The shrinkage tendency differed with the kind of impression material. Some impression materials shrank slowly and ohers shrank markedly immediately after the removal of the impression.
All the tested materials showed a similar rate of shrinkage, 26 minutes after the removal of the impression.
