Based on the findings of this in vitro study, the use of ZnO nanoparticles is recommended, since they did not negatively affect the properties of the materials evaluated.

The opacifier protects facial silicones against color degradation, and oil paint is a stable pigment even without addition of opacifier.

The failure of facial prostheses is caused by limitations in the properties of existing materials, especially flexibility and durability. Therefore, this study evaluated the Shore A hardness of silicone used for fabrication of facial prostheses, Silastic MDX4-4210, according to the influence of storage period, daily disinfection, and 2 types of pigmentation. Thirty specimens were fabricated and divided in 3 groups: colorless, pigmented with makeup, and pigmented with iron oxide. Analysis of results was assessed on a Shore A hardness meter immediately, 6 months, and 1 year after fabrication of specimens, following the guidelines of the American Society for Testing and Materials. The hardness values were statistically analyzed by the Tukey test. The silicone exhibited an increase in hardness with time. However, the hardness was stable from 6 months to 1 year. It was concluded that the silicone is within the values of Shore A hardness reported in the literature, regardless of the storage period, pigmentation, and chemical disinfection.

Acrylic resins have been widely used due to their acceptable esthetics and desirable characteristics such as easy handling, good thermal conductivity, low permeability to oral fluids and color stability. Flexible resins were introduced on the market as an alternative to the use of conventional acrylic resins in the construction of complete and partial removable dentures. Although these resins present advantages in terms of esthetics and comfort, studies assessing chromatic and microhardness alterations of these materials are still scarce in the related literature. The aim of this study was to evaluate the chromatic and microhardness alterations of two commercial brands of flexible resins in comparison to the conventional resin Triplex when submitted to accelerated aging. The resins were manipulated according to manufacturers' instructions and inserted into a silicone matrix to obtain 21 specimens divided into 3 groups: Triplex, Ppflex and Valplast. Triplex presented the highest microhardness value (p < 0.05) for all the aging periods, which was significantly different from that of the other resins, followed by the values of Valplast and Ppflex. Comparison between the flexible resins (Ppflex and Valplast) revealed a statistically significant difference (p < 0.05) as regards color. The flexible resin Ppflex and the conventional resin Triplex presented no statistically significant difference (p < 0.05) as regards aging. The accelerated aging significantly increased the microhardness values of the resins, with the highest values being observed for Triplex. Valplast presented the greatest chromatic alteration after accelerated aging.

No abstract

The ceramic pigment presented greater color stability regardless of disinfection and period. On the other hand, the makeup pigment exhibited the highest values of chromatic alteration.

Color stability of resin and silicone is an important factor for longevity of facial prostheses. The aim of this study was to evaluate the color stability of resins and silicone for facial prostheses. Three brands of acrylic resin and 1 of facial silicone were evaluated considering pigment incorporation for the colorless materials. Ten samples of each material were fabricated and submitted to measurements of chromatic alteration initially and after 252, 504, and 1008 hours of weathering through visual analysis and spectrophotometry. Data were evaluated by analysis of variance and Tukey test (P < 0.05). Results showed a statistically significant difference in color alteration among materials independent of aging. According to visual analysis, the color difference between pigmented and colorless Silastic MDX4-4210 and between pigmented and colorless Classico acrylic resin was statistically significant for the 3 weathering periods. Aging for 1008 hours represented a significant influence on color alteration of all resins. All materials presented chromatic alteration after accelerated artificial aging.

Opacifier addition, chemical disinfection, and accelerated aging procedures affected the color stability of the maxillofacial silicone.