Six maxillofacial materials were evaluated by determining their dynamic properties with use of a Goodyear Vibrotester. The dynamic modulus, internal friction, and dynamic resilience were measured for all materials over a temperature range of -15 to 37 C. The dynamic modulus ranged from 11.1 to 124.8 kg/cm2 and the dynamic resilience varied from 1.1 to 63.5%.

Chemical Phenomena↗

PubMedDate not supplied

Color stability of elastomers for maxillofacial appliances.

The color stability of polyvinyl chloride, polyurethane, and silicone polymers for maxillofacial applications was determined after accelerated aging using reflectance spectrophotometry. On the basis of color stability after accelerated aging, and ease of processing, several silicone materials were the most promising.

Color↗

PubMedDate not supplied

Color stability of restorative resins under accelerated aging.

The color stability of seven commercial composite resins, an unfilled resin, and three glazes was studied under conditions of accelerated aging by reflection spectrophotometry and visually with Munsell color tabs. After aging for 900 hours, most of the resins had lower values of luminous reflectance and excitation purity and higher values of dominant wavelength and contrast ratio compared to values at baseline.

Acrylic Resins↗

PubMedDate not supplied

Effect of soft denture liner on stress distribution in supporting structures under a denture.

This study examined the effect of a soft denture liner on the distribution of stresses in the denture-supporting structures. Dentures without a linear 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 areas decreased when a soft denture liner was used. However, the stresses in the bone increased remarkably up to 3.0 seconds after loading. 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.

Alveolar Process↗

PubMedDate not supplied

Bond strength of six soft denture liners processed against polymerized and unpolymerized poly(methyl methacrylate).

The bond strength of six commercial soft denture liners was evaluated by a two-phase tensile test. The soft denture liners investigated were VinaSoft, Prolastic, Flexor, Molloplast-B, Novus, and SuperSoft. The samples were fabricated by processing them (1) against polymerized poly(methyl methacrylate), and (2) against unpolymerized poly(methyl methacrylate). The soft denture liners were processed according to the manufacturers recommendations. The samples were tested using an Instron Universal Testing Machine. The mode of failure, adhesive or cohesive, was also recorded. The bond strength when processed against unpolymerized poly(methyl methacrylate) ranged from 0.48 to 2.60 MPa, and when processed against polymerized poly(methyl methacrylate) the bond strength ranged from 0.94 to 2.56 MPa. A two-way analysis of variance (P = .05) revealed a significant increase in bond strength when the liners were processed against polymerized poly(methyl methacrylate), except for Novus, which had no change, and VinaSoft, which decreased. The Tukey interval between materials was .22 and between methods of polymerization was .08. Four of the six liners investigated demonstrated increased bond strength when processed against polymerized poly(methyl methacrylate). It was concluded that bonding can be influenced by the processing method.

Acrylic Resins↗

PubMedDate not supplied

Impact absorption of four processed soft denture liners as influenced by accelerated aging.

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.

Acrylic Resins↗