EVALUATION OF THE VISCOELASTIC PROPERTIES OF DENTURE SOFT LINING MATERIALS

Denture soft lining materials are widely used in prosthetic dentistry. Their success has been attributed to their softness and resilience, p roperties described by their viscoelasticity. Though these properties have been extensively investigated in laboratory studies, clinical stu dies have been limited. The viscoelastic properties of the temporary s oft lining material Coe Soft and the permanent soft lining materials P alasiv 62 and Molloplast-B have been studied using a force/distance pr obe whereby penetration was measured against time under constant stres s. Derived values of an initial and time-dependent compliance has allo wed a quantitative in vivo and in vitro assessment of freshly prepared samples of each test material and comparison between materials. The b aseline behaviour of each test material in response to the test regime n was similar for both clinical and laboratory specimens. Three types of behaviour could be identified: (i) constant strain in which penetra tion was clearly less than specimen thickness-elastic behaviour (Mollo plast-B); (ii) constant strain in which the penetration was equal or n early equal to specimen thickness-apparent elastic behaviour (Coe Soft ); (iii) strain which increased with time of load application-viscoela stic behaviour(Palasiv 62). The mean and range of baseline clinical th ickness for Coe Soft was approximately half that seen for the permanen t soft lining materials. There was a much smaller range in the baselin e compliance of all materials than might have been anticipated from a knowledge of their relative softness.