Discoloration of various CAD/CAM blocks after immersion in coffee

OBJECTIVES: This study evaluated color differences (ΔEs) and translucency parameter changes (ΔTPs) of various computer-aided design/computer-aided manufacturing (CAD/CAM) blocks after immersion in coffee. MATERIALS AND METHODS: Eight CAD/CAM blocks and four restorative composite resins were evaluated. The CIE L*a*b* values of 2.0 mm thick disk-shaped specimens were measured using the spectrophotometer on white and black backgrounds (n = 6). The ΔEs and ΔTPs of one day, one week, and one month immersion in coffee or water were calculated. The values of each material were analyzed by two-way ANOVA and Tukey's multiple comparisons (α = 0.05). The ΔEs after prophylaxis paste polishing of 1 month coffee immersion specimens, water sorption and solubility were also evaluated. RESULTS: After one month in coffee, ΔEs of CAD/CAM composite resin blocks and restorative composites ranged from 1.6 to 3.7 and from 2.1 to 7.9, respectively, and ΔTPs decreased. The ANOVA of ΔEs and ΔTPs revealed significant differences in two main factors, immersion periods and media, and their interaction except for ΔEs of TEL (Telio CAD, Ivoclar Vivadent). The ΔEs significantly decreased after prophylaxis polishing except GRA (Gradia Block, GC). There was no significant correlation between ΔEs and water sorption or solubility in water. CONCLUSIONS: The ΔEs of CAD/CAM blocks after immersion in coffee varied among products and were comparable to those of restorative composite resins. The discoloration of CAD/CAM composite resin blocks could be effectively removed with prophylaxis paste polishing, while that of some restorative composites could not be removed.

Effect of Plasma Treatment Time on Tensile-shear Bond Strength between Fiber-reinforced Composite Post and Flowable Composite Core and Wettability on Polymer Surfaces

Plasma treatment is an alternative way in improving bonding properties of fiber-reinforced post. However, technical parameters of this treatment need to be clarified, especially treatment time. The purpose of this study was to evaluate the effect of plasma treatment time on adhesion between fiber-reinforced post and a flowable composite core. Two types of post, methacrylate-based matrix (FRC Postec) and epoxy resin-based matrix (DT Light post) were treated with the mixture of Helium and Nitrogen (He+N2) plasma using a radiofrequency generator with various times before bonding to flowable methacrylate-based composite. Pull-out tests were performed using a universal testing machine. One-way ANOVA revealed that the best plasma treatment time for FRC Postec and DT Post was 10 and 15 minutes respectively. The adhesive properties of both posts tend to degrade with longer plasma treatment time. Water advancing contact angles on methacrylate-based polymer and epoxy resin-base polymer were decreased as the plasma treatment time was increased.Keywords: Fiber-reinforce composite post, tensile-shear bond strength, plasma treatment, contact angle