An evaluation of acrylic complete-dentures using the discrimination of elastic bodies or viscous fluids

The discrimination test on elastic bodies and viscous fluids was carried ou t for 16 young dentists and 13 denture patients, because it is considered t hat dentures affect the ability to discriminate food. The materials used in this test were six thermoplastic polyurethane elastomers with compressive elastic moduli from 11.8 to 62.0 MPa and six silicone impression pastes wit h coefficients of viscosity from 1.77 x 10(-2) to 23.0 x 10(-2) MPa . s. Th e subjects (dentists and patients) discriminated the materials based on dif ferences in elastic moduli or coefficients of viscosity by chewing the mate rials for 10 s. From these experiments, it became clear that the ability to discriminate between elastic bodies or viscous fluids upon chewing, of sub jects who use complete-dentures in combination with their own teeth and eit her an upper or lower complete-denture (S/D) or who have a set of complete- dentures in both jaws (D/D) decreased considerably, compared with that of s ubjects who have their own teeth in upper and lower jaws (S/S). The ratios of SID and D/D against S/S were 0.5 and 0.3, respectively. This indicates t hat with an increase in the area occupied by dentures in the oral cavity, t he value of the differential threshold increased markedly and made food dis crimination more difficult. In addition, discriminating viscous fluids was 2.4 to 3.1 times more difficult compared with the discrimination of elastic bodies, independent of denture placement.