2012 Volume 4 Issue 2 Pages 193-200
Purpose: Nonmetal clasp dentures have been used recently in dental treatment because thermoplastic resins have particular elasticity that allows them to be retained without metal clasps. These nonmetal clasp dentures have often been designed to be especially aesthetic by using only thermoplastic resins without occlusal rests. The purpose of this study was to examine the influence of metal rests in nonmetal clasp dentures on the pressure distribution to the soft tissue.
Methods: Three pressure sensors were seated on a model simulating mandibular unilateral bounded saddles. Three types of experimental dentures were fabricated on a simulation model: a nonmetal clasp denture with a metal rest, a nonmetal clasp denture with a thermoplastic resin rest, a nonmetal clasp denture without a rest, and two types of control dentures (acrylic resin denture with a metal rest and metal structural denture with a metal rest). Silicone impression material was injected to simulate soft tissue; the pressure distribution during displacement of the soft tissue by the denture was measured using 49.0 N loading. The data obtained (n = 5) were analyzed by one-way ANOVA and Tukey's multiple comparisonstest (α = 0.01).
Results: Statistically significant differences were noted among the five types of dentures. The pressure distribution of the metal structural denture was the lowest, and the pressure distribution of the nonmetal clasp denture with a thermoplastic resin rest was highest. By using a metal rest, we found that pressure was reduced in the nonmetal clasp dentures (p < 0.01).
Conclusions: The above findings indicated that a metal rest should be used for nonmetal clasp dentures to increase pressure on the soft tissue.
