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Purpose: Composite resin teeth are more widely used than porcelain or acrylic resin teeth in the fabrication of removable dentures because of their high fracture toughness and high abrasion resistance. The purpose of this study was to evaluate the shock absorbability of commercially available artificial posterior teeth by the free drop-ball test with an accelerometer and to evaluate the Vickers hardness at the surface., Materials and Methods: The tested artificial teeth included seven composite resin teeth, one acrylic resin tooth, and one porcelain tooth. Specimens were tested 50 hours after immersion in distilled water at 37 degrees C. The impact value and Vickers hardness were measured. A one-way analysis of variance was used to analyzed the data (P = .05)., Results: The composite resin teeth showed an intermediate impact value between that of the acrylic resin tooth and the porcelain tooth. Among the artificial teeth investigated, the porcelain tooth showed the highest impact value. A significant difference in the impact value was observed between the porcelain tooth and the composite resin and acrylic resin teeth. However, no significant difference was observed among the composite resin teeth tested. A significant correlation was found between the impact values and the Vickers hardness of the artificial teeth., Conclusion: The present findings suggest that composite resin teeth and acrylic resin teeth have a higher shock absorbability than porcelain teeth.

The cushioning effect of soft denture liners was evaluated by using a free drop test with an accelerometer. Materials tested included SuperSoft (Coe Laboratories, Chicago, IL), Kurepeet-Dough (Kreha Chemical, Tokyo), Molteno Soft (Molten, Hiroshima, Japan) and Molloplast-B (Molloplast Regneri, Karlsruhe, Germany). All materials were found to reduce the impact force when compared to acrylic denture base resin. A 2.4-mm layer of soft denture material demonstrated good impact absorption, and Molloplast-B and Molteno had excellent impact absorption. When the soft denture liner was kept in an accelerated aging chamber for 900 hours, the damping effect recorded increased for all materials tested. Aging of all materials also affected the cushioning effect. [ABSTRACT FROM AUTHOR]

This study examined the effect of a soft denture liner on the distribution of stresses in the denture-supporting structures, Dentures without a liner and with three configurations of a soft liner were simulated by using a two-dimensional viscoelastic finite-element stress analysis. The stress intensity at functional force-bearing stress decreased when a soft denture liner was used. However, the stresses in the bone increased remarkably up to 3.0 seconds after leading Because of the time-dependent effect of stresses applied to soft denture liners, denture patients who clench or brux may not benefit as greatly from soft denture liners. The study indicates that viscoelastic finite-element analysis is helpful for evaluating soft denture liners. Soft denture liners appear to be useful for improving the stress distribution in the supporting structures under dentures. [ABSTRACT FROM AUTHOR]

A pilot study was conducted to evaluate the strengthening effect of a Ni-Cr metal plate on an acrylic resin test specimen. Test specimens were retained using a mechanical method and adhesion with 4-META resin. Three positions of the metal plate were evaluated: on the compression surface, on the tension surface, and in the middle layer. A three-point bend test was used to compare physical properties of the specimens with metal-plate reinforcement to a resin specimen without reinforcement. No advantage was derived from placing the metal plate in the center of the resin. Both methods of retention produced improved physical properties when placed on either the compressive or tensile side, but the greatest advantages were gained when an adhesive-retained plate was placed on the side in tension. [ABSTRACT FROM AUTHOR]