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: Evidence shows that the powder/liquid mixing ratio recommended by the manufacturers is often not respected when mixing the glass ionomer [GI] powder and liquid, yielding a GI cement with disproportionate powder/liquid ratio. Considering the confirmed effect of powder/liquid ratio on the GI properties, and more importantly, its fluoride release potential, this study aimed to assess the effect of powder/liquid ratio on fluoride release of GI cements
Methods: Fuji II, Fuji II LC Improved and Fuji IX GI cements were used in this experimental study. Of each material, three groups with powder 20% less than recommended, the exact recommended ratio and powder 20% more than recommended, were prepared. To assess the fluoride release potential, 45 disc-shaped specimens measuring 2×4mm were prepared [5 per each group]. After fabrication, the specimens were immersed in 5 mL of distilled water. The amount of fluoride released into distilled water was measured at days 1 to 7, and also at 13, 14, 15, 28, 29, 30, 58, 59, 60, 88, 89, and 90 days, using Ion Selective Electrode [ISE]. After each time of measurement, distilled water was replaced. Data were analyzed using repeated measures ANOVA. Tukey's post hoc test was used for pairwise comparison of groups and powder/liquid mixing ratio. For pairwise comparison of time points, the Bonferroni adjustment was applied [p<0.05]
Results: Based on the results, although the amount of fluoride released from Fuji IX was higher than Fuji II, this difference was not statistically significant [p=0.589]. The lowest fluoride release was seen in Fuji II LC and this difference was statistically significant [p<0.05]. Change by 20% in the powder/liquid mixing ratio in the three GI cements had no significant effect on fluoride release [p=0.650, p=0.103, p=0.082]
Conclusion: Fluoride release from GI was time-dependent and the amount of released fluoride decreased over time. Fuji II LC resin-modified GI [RMGI] released less fluoride than Fuji II and Fuji IX. Also, 20% change in powder/liquid mixing ratio had no significant effect on fluoride release in different groups
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
Endodontically treated teeth are weakened structurally for vast decayed areas, access cavity preparation and filling. RCT is a common routine dental service in daily practice and the use of composite post are proposed for the increase of weak teeth, this study designed to evaluate the effect of composite posts on RCT teeth. The study was experimental. A total of 20 maxillary central teeth - extracted for periodontal reasons - were divided in control and experimental groups. The teeth were endodontically treated. In ontrol teeth, access cavities were restored with Tetric composite and Bonding agent [3M Scotchbond Multi-purpose Plus]. In experimental group, Tetric composite posts were prepared after canal preparation and canals were cemented with Variolink Dual Cure and the same bonding agent. Finally, access cavities were restored with Tetric composite. The teeth were mounted in acrylic blocks and the force caused to break them was determined by Instron Universal Machine. The force to break the teeth with composite posts was greater [760 +/- 141.4 N]. This force was 590 +/- 191.5 N in teeth without post and the difference between two groups was statistically significant [P<0.04]. The use of composite post in invitro situation can increase the strength of RCT treated teeth against the exposed forces