RESUMO
PURPOSE: Staining of prosthodontic materials may result in patient dissatisfaction and additional expense for replacement. This study aimed to determine the color stability of two heat-cured denture base acrylic (Lucitone 550, Vipi Cril) and one nylon denture base resin (Transflex) after immersion in beverages. MATERIALS AND METHODS: Forty disks of each resin (20.0-mm diameter, 3.0-mm thick) were prepared and stored in distilled water for 24 hours at 37°C. During that time (T(0) ), the color of all specimens was spectrophotometrically measured. Each specimen was immersed in coffee, cola, red wine, and distilled water as a means of control. After 15-day (T(1) ) and 30-day (T(2) ) periods of immersion, the color of the specimens was measured again. The CIE (Commission Internationale de L' Eclairage) L*a*b* system was used to determine mean ΔE (color changes) values for each material and compared statistically with two-way ANOVA and Bonferroni intervals at 0.95. RESULTS: In ΔET(0) T(1) and ΔET(0) T(2) the most severe staining was apparent with red wine (p < 0.001), followed by coffee (p < 0.01), when compared to the specimens stored in distilled water. Transflex also showed significant color change after immersion in cola (p < 0.01). In ΔET(1) T(2) only red wine promoted significant staining of all resins (p < 0.0001). CONCLUSION: Chromatic changes were exhibited by specimens immersed in red wine, followed by coffee. For Transflex, cola also promoted color changes. The values of color changes converted to National Bureau of Standard units showed them to be perceivable to the human eye.
Assuntos
Resinas Acrílicas , Bebidas , Cor , Bases de Dentadura , Nylons , Resinas Acrílicas/química , Colorimetria , Teste de Materiais , Nylons/químicaRESUMO
PURPOSE: To determine whether the adverse interaction between a two-step/acidic etch-and-rinse adhesive (One-Step Plus [OS], Bisco) and chemically cured resin luting cement [Variolink II, Ivoclar Vivadent] can improve adhesive coupling by reducing the dentin permeability with an oxalate desensitizer (BisBlock, Bisco). MATERIALS AND METHODS: After exposing dentin on the occlusal surfaces of human third molars, bonding was performed on either oxalate treated (BB) or nontreated (NB) demineralized dentin. A resin luting cement was placed in the format of a crown following the light-curing mode (only with the base syringe [LC]) or the chemically curing mode (mixture of base and catalyst syringes [CC]). The activation of the LC or CC cements was either immediately [IM], meaning soon after the placement of LC and the initial set of CC cement (5 min), or after a delay of 20 min [DP] for both modes of polymerization. Five teeth were assigned to each experimental condition. Teeth were sectioned to obtain sticks with a cross-sectional area of 0.95 mm2, which were tested using the microtensile bond strength test soon after the specified periods of polymerization. The bond strength values of each adhesive were analyzed by three-way repeated measures ANOVA and Tukey's tests (α = 0.05). Fractographic analysis of the specimens was performed using SEM. RESULTS: The delayed polymerization (for both LC and CC cements) produced low bond strength values compared to IM activation. When the BB was employed, the bond strength values of the CC cement was approximately doubled, while the BB did not affect the bond strength of the LC cement. Bond strength values of LC cements were higher than CC. The use of BB significantly improved the bond strength of CC cement only. The morphological observations confirmed the bond strength results. A myriad of voids could be detected in the luting cement side when BB was not applied, except for the immediately light-cured group. CONCLUSION: The use of an oxalate desensitizer (BisBlock) reduced the incompatibility between a two-step etch-and rinse adhesive and chemically cured resin cements and light-cured systems in the delayed polymerization mode.