Long-term dimensional stability and reproduction of surface detail of four polyvinyl siloxane duplicating materials

Duplicating materials must routinely accurately reproduce the details of dental casts and thus contribute significantly to the close adaptation and success of a removable prosthesis or fixed indirect restoration. It is important to establish the long-term dimensional stability of polyvinyl siloxane materials (PVS) as they are widely used in dental technology and over the duration of a course of treatment, are stored under dental laboratory conditions. The dimensional stability of four PVS duplicating materials was investigated over a 13-week period.

Forty PVS duplicate moulds of a partially dentate maxillary arch were produced from four materials (Elite double 8, Gemini transparent, C & J pourable silicone and Z Dupe). Three dimensions were measured in triplicate at baseline 1, 5, 9 and 13 weeks using computerised image analysis. Half of the specimens were measured following storage at room temperature (21+/-2 degrees C) and half at 37 degrees C to represent storage in hot climates. Specimens for scanning electron microscopy were prepared by duplicating a rugosity standard.

At room temperature two materials Elite Double 8 and Z Dupe showed no statistically significant dimensional change, the other two materials showed a slight increase of dimensions. Specimens stored at 37 degrees C showed greater differences in dimensions with Z Dupe showing statistically significant shrinkage. SEM investigation showed no surface deterioration of two materials.

None of the materials showed a change in dimension greater than 2% and the four PVS materials showed good dimensional stability over the time period of the study.