Dynamic viscoelastic properties of vinyl polysiloxane denture soft lining materials

P>The aim of this study was to investigate the dynamic viscoelastic properties of seven commercially available vinyl polysiloxane denture soft lining materials. Five rectangular specimens (2 x 10 x 30 mm) were prepared from each material. The complex modulus E* (MPa) and loss tangent (tan delta) of each specimen were determined with a non-resonance forced vibration method using an automatic dynamic viscoelastometer at 1 Hz after 1 day of dry storage, and after 1, 30, 60, 90 and 180 days of wet storage at 37 degrees C. All data were analysed using one-way anova and Bonferroni/Dunn's test for multiple comparisons with a significance level of P < 0 center dot 01. All materials varied widely in terms of viscoelasticities and showed both an increase in E* and a decrease in tan delta at 1 Hz after the 1-day wet storage. After 60 days of wet storage, both E* and tan delta did not change significantly. The stiffer materials (> 30% filler content) with high E* values (> 2 center dot 00 MPa) showed elastic behaviour with tan delta values of around 0 center dot 03. The softer materials (6% filler content) with high tan delta values (initial value > 0 center dot 10) showed viscous behaviour and were easily affected by water absorption after the 1-day wet storage. It can be concluded that for the proper selection of vinyl polysiloxane denture soft lining materials, it is very important to evaluate the viscoelastic properties after 60 days of wet storage.