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Objective: Chemical solutions have been widely used for disinfection of dentures, but their effect on color stability of denture tooth acrylic resins after repeated procedures is still unclear. The aim of this in vitro study was to evaluate whether repeated cycles of chemical disinfectants affected the color stability of two denture tooth acrylic resins., Material and Methods: Sixty disc-shaped specimens (40 mm x 3 mm) were fabricated from two different brands (Artiplus and Trilux) of denture tooth acrylic resin. The specimens from each brand (n=30) were randomly divided into 6 groups (n=5) and immersed in the following solutions: distilled water (control group) and 5 disinfecting solutions (1% sodium hypochlorite, 2% sodium hypochlorite, 5.25% sodium hypochlorite, 2% glutaraldehyde, and 4% chlorhexidine gluconate). Tooth color measurements were made by spectrophotometry. Before disinfection, the initial color of each tooth was recorded. Further color measurements were determined after subjecting the specimens to 7, 21, 30, 45, 60, and 90 immersion cycles in each tested solution. Color differences (ΔE*) were determined using the CIE L*a*b* color system. Data were analyzed using two-way repeated measures analysis of variance (ANOVA) followed by Tukey tests. The significance level was set at 5%., Results: There were statistically significant differences in ΔE* among the 5 disinfectants and water during the 90 cycles of immersion for both denture tooth acrylic resins. Distilled water promoted the greatest color change in both denture tooth acrylic resins, nevertheless none of tested disinfectants promoted ΔE* values higher than 1.0 on these acrylic materials during the 90 cycles of disinfection., Conclusions: Repeated immersion cycles in disinfecting solutions alter ΔE* values, however these values do not compromise the color of the tested denture tooth acrylic resins because they are imperceptible to the human eye.

The aim of this study was the evaluation about the influence of the quantity and the localization of resin patterns to cast metallic posts in its diameter and length reproduction. Seventy-two patterns for posts were fabricated by using prefabricated FKG plastic posts and divided for casting in 3 groups: G1-small ring/4 patterns, G2- medium ring/6 patterns, G3- big ring/8 patterns. Half of the patterns of each group were placed on the right side of the ring midline and the other half, on the left side, in order to guide the ring inside of the centrifuge. Using the comparative microscope, measures of diameter and length in different places were obtained before and after casting. The results were submitted to statistic analysis (ANOVA two way and Tukey's test), to make possible these observations: 1°) the position of patterns didn't influenced the measured dimensions. 2°) the same happened with the quantity of patterns inside the ring. 3°) only the pins of group G3 have presented statistically significant diameter differences. In conclusion, 1°) the position of patterns inside the ring and its quantity did not result in significant changes in pins length and diameter. 2°) Although there were no significant length alterations, significant ones were observed in the diameters 3, 6, and 9mm of Group G3.