Influence of Temperature Changes on Stability of Vinyl Polysiloxane Impression

Methods: Heavy and regular consistencies addition-reaction polysiloxane impression materials were dispensed and mixed according to the manufacturer’s instructions. Specimens were either stored dry or wet for 24 hours in 100% humidity at 37°C. A diamond saw was used to prepare the specimens into disks of comparable sizes for testing. Thermomechanical analysis (TMA) was performed on the prepared specimens and dimensional changes were evaluated over a range of temperature from 23°C to 37°C. Means and standard deviations were calculated and results were subjected to 2-way analysis of variance followed by Tukey Studentized Range test (α = 0.05).

Results: Thermal expansion coefficients were not significantly different for the material consistency (P=0.33) and storage medium (P=0.23). The mean dimensional change for the heavy consistency impression material was 4.03 μm and 3.95 μm for the dry and wet conditions respectively, while the regular consistency impression material had mean values of 5.36 μm and 5.23 μm for the dry and wet conditions respectively. 

Conclusions: Temperature changes within the range evaluated do not affect the dimensional accuracy of vinyl polysiloxane impression materials