ABSTRACT
Objective: Selection of an appropriate shade of composite is critical in achieving an esthetic restoration. Different systems are used to assess and describe color parameters. This study aimed to assess the effect of color and thickness of Filtek Supreme [FS] and Premise [P] composite resins on correction of tooth discoloration
Methods: In this in vitro experimental study, 10 anterior teeth with Vita A2 color shade were selected. Composite specimens were fabricated in 0.5 and 0.75 mm thicknesses of FS and P composites. Intact teeth, prepared teeth, prepared teeth with enamel and dentin composite discs on their buccal surfaces, stained teeth and stained teeth with composite discs were photographed using a digital camera under standard conditions and color change [[Delta]E] at different phases was calculated
Results: The L[asteristk], a[asteristk] and b[asteristk] color parameters in prepared and unstained teeth were not significantly different from those of intact teeth. In stained teeth, the L[asteristk] parameter only in prepared and stained teeth with 0.75mm P composite was not significantly different from the L[asteristk] parameter in intact teeth. Significant differences were seen in other stained teeth. The a[asteristk] and b[asteristk] parameters only in prepared and stained teeth with 0.5 mm FS composite were significantly different from those in intact teeth. By increasing the thickness of composite, the color change in comparison with intact teeth decreased in both groups
Conclusion: The results showed that the effect of type of composite, its thickness and their interaction on the color change was significant when using FS and P composites in 0.5 and 0.75mm thicknesses in comparison to intact teeth and the lowest color difference with intact teeth was achieved using 0.75mm thickness of P composite [enamel and dentin]
ABSTRACT
Objective: Zirconia cores have limited light transmittance and data are scarce on light transmission through zirconia cores with and without the veneering ceramic
Methods: In this in vitro study, Disc-shaped specimens [11.5 mm in diameter and 0.4 [0.05] mm in thickness] were fabricated of three types of zirconia namely Mamut, Heany and ZirkonZahn [n=5]. A disc-shaped specimen [11.5 mm in diameter and 0.65 [0.05] mm in thickness] of veneering ceramic [Cerabien ZR, Kuraray, Noritake, Japan] was also fabricated. The intensity of light transmitted through the zirconia specimens with and without the veneering ceramic was recorded using a light curing unit [LED, SDI Radii Plus, Australia] and its respective radiometer [LED Radiometer, SDI, Australia]. Data were analyzed using repeated measures ANOVA and Tukey's HSD test
Results: A significant difference was noted in light transmission among different types of zirconia before and after veneering. After veneering, light transmission decreased in all specimens and the reduction in light transmission in Zirkonzahn group was significantly greater than that in Heany and Mamut groups [p<0.001]
Conclusion: Veneered zirconia systems have limited translucency and ceramic veneering significantly decreases light transmission through zirconia
ABSTRACT
Objective: Bulk-fill composites are a group of composite resins designed for easy and fast filling of large cavities. This study aimed to assess the color stability of bulk-fill composites subjected to xenon radiation and evaluate their color change [[delta]E] following polymerization
Methods: In this in vitro experimental study, 30 specimens [4mm in height and 8mm in diameter] were fabricated of x-traFil and Tetric N-Ceram universal color bulk-fill composites and A2 shade of Grandio composite [as control]. Bulk-fill composites were placed in the mold in 4mm thickness according to the manufacturers' instructions. In the control group, composite was applied to the mold in two layers each with 2mm thickness. Tetric and Grandio composites were cured for 20 seconds and x-traFil was cured for 10 seconds with a LED light-curing unit. A total of 15 specimens [five of each composite] were used for each test. For assessment of color change due to polymerization, L[asterisk], a[asterisk] and b[asterisk] color parameters were measured before and immediately after polymerization and also 30 days after immersion in distilled water in an incubator at 37[degree sign] and 70% humidity using a spectroradiometer. For xenon test, the specimens were subjected to color analysis after 48 hours of storage in distilled water. Next, they were subjected to xenon lamp radiation in xenon environment chamber for 122 hours at 22[degree sign] and 25% humidity and then the color parameters were measured again. The mean and standard deviation [SD] of all values were calculated. One-way and repeated measures ANOVA were used to compare [delta]E and [delta]L among the groups. Tukey's HSD test was used for pairwise comparisons
Results: The value of [delta]E immediately after polymerization was the lowest for Grandio [4.91] and the highest for Tetric [9.44]. Thirty days after the polymerization, [delta]E was the lowest in Grandio [3.07] and the highest in Tetric [9.27]; [delta]E showed a decreasing trend over time in all specimens. Under xenon light radiation, Grandio showed the lowest [1.50] and Tetric showed the highest [delta]E [11.15]
Conclusion: Following polymerization and under xenon lamp radiation, [delta]E of conventional composite was less than that of bulk-fill composites