Viscoelastic properties of some soft lining materials - I - effect of temperature

The time dependent, viscoelastic characteristics of a number of dental soft liners (occasionally called resilient liners) were investigated using a dynamic mechanical analyser (DMA). The materials consisted of eight commercial products including methacrylate, silicone and phosphazine-based soft polymers as well as two experimental formulations. The DMA used was of the forced vibrational variety. The test conditions, such as frequency and temperature, were chosen to mimic in use (masticatory) conditions. A wide variety of behaviour was observed and accounted for. This included a seven fold range in the storage modulus (2.79–19.7 MPa) and a 50-fold range in the loss tangent (0.029–1.52) at 37°C and 1 Hz. The materials could generally be divided into either rubbery behaviour with low modulus and loss tangent, i.e. the silicones, or leathery behaviour with both higher modulus and loss tangent, i.e. the methacrylates. A search of the literature did not find a universally preferred set of properties, although a possible link with residual ridge resorption is indicated.