An evaluation of the viscoelastic characteristics of soft denture liners

Abstract

The purpose of this study was to evaluate the viscoelastic characteristics of a group of soft denture liners by means of a creep test. The materials evaluated included a silicone rubber base direct liner (Sofreliner MS), a polyolefin base indirect liner (Molteno S), and a conventional tissue conditioner (Coe Soft) as a control. Cylindrical specimens of each material were fabricated using a metal mold. Half of the specimens were subjected to mechanical fatigue with a 75-N load at 1.2 Hz for 200,000 cycles. The creep test was performed on each material and condition with and without a fatigue test using low-load conditions to achieve a 10% strain on all specimens. Viscosity and elasticity were measured, and the data were statistically analyzed using 1-way analysis of variance and Fisher's Protected Least Significant Difference (PLSD) test (p < 0.05). The silicone rubber direct liner (1.31 +/- 2.1 MPa) exhibited a similar mean elastic property as the conventional tissue conditioner (0.90 +/- 0.22 MPa) and an intermediate viscosity between the conventional tissue conditioner (0.11 +/- 0.01 GPa. s) and polyolefin base indirect liner (9.84 +/- 1.08 GPa. s). The elasticity did not change for polyolefin and silicone rubber after the fatigue process. Significant differences in the viscosity of silicone rubber were seen with and without fatigue testing (p < or = 0.05). The silicone rubber was as soft as the tissue conditioner and softer than the polyolefin liner. The stiffer the material, the lower the permanent deformation observed.