Effects of specular component on color differences of different filler type resin composites after aging.

OBJECTIVE: This study evaluated the effects of specular component mode of specular component excluded (SCE) and specular component included (SCI) on color changes of different filler type resin composites after aging of 1 week and 1 year. METHODS: Resin composites and shades used in this study were submicron-filled Estelite Sigma (Sigma: Inc, A2, A3, B3, C2, OA2, OA3) and nanofilled Filtek Supreme XT (XT: Clear, A2E, A2B, A3B, C2B, A2D, A3D). Resin disks of 2mm in thickness and final polish with 2400-grit silicon carbide paper were stored in 100% relative humidity. One-week and 1-year after curing, the colors of the composite disks were measured with a spectrophotometer in SCI and SCE modes. RESULTS: For both 1-week and 1-year specimens, the values of L* with SCI were significantly higher than SCE for all shades of Sigma and XT; however, a* and b* were depended on brands and shades. Comparing 1-week and 1-year values, DeltaE*ab ranged 1.5 (A3 and B3)-2.9 (Inc) with SCI and 1.4 (A3)-2.9 (Inc) with SCE for Sigma, and 1.1 (A3D)-7.1 (Clear) with SCI and 1.4 (A3D)-7.6 (Clear) with SCE for XT. The values of DeltaE*ab with SCE were higher than those of SCI for all shades of XT; however, for Sigma, the differences varied with shades. CONCLUSION: Specular component mode (SCE vs. SCI) significantly influenced L* values; however, the color differences affected by aging were dependent on brands and shades of the resin composites tested.

Color characteristics of resin composites in different color modes and geometries.

Color characteristics of the shades for different filler type resin composites were compared in the reflectance and transmittance modes, and specular component included (SCI) and specular component excluded (SCE) geometries for reflectance mode. Resin composites and shades used in this study were submicron filled Estelite Sigma (Sigma: Inc, A2, A3, B3, C2, OA2, OA3) and nanofilled Filtek(TM) Supreme XT (XT: Clear, A2E, A2B, A3B, C2B, A2D, A3D). Resin disks of 2 mm in thickness and final polish with 2,400-grit silicon carbide paper were kept in 100% humidity. One week after curing, color of the resin disks were measured with a spectrophotometer. Both for Sigma and XT, reflectance of each of all shades measured with SCI were significantly higher than those with SCE. Compared to the values with SCI and SCE, the L with SCI were significantly higher for all shades of Sigma and XT, however, a and b were depended with brands and shades. Different filler type resin composites showed different color characteristics, reflectance, transmittance and L a b distribution. In some shades, color difference between the measurement with SCI and SCE was visually perceptible level. It would be concluded that the color of resin composite measured with the SCI and SCE geometries differed.

The effect of bleaching on the elastic modulus of bovine enamel.

The purpose of this study was to determine the elastic modulus of enamel during bleaching procedure with the use of an ultrasonic device. Enamel sections were obtained from freshly extracted bovine incisors. Specimens were exposed to 10% carbamide peroxide for two hours, followed by an application of a fluoride-containing toothpaste for five minutes and stored in artificial saliva (pH 7.0). An ultrasonic device was used to measure the sound velocities of longitudinal and shear waves as well as elastic modulus. The mean elastic modulus of bleached enamel decreased with time, from 15.5 GPa to 10.1 GPa. Conversely, the elastic modulus of bleached enamel followed by application of a fluoride-containing toothpaste increased with time, from 15.2 GPa to 20.2 GPa. Results of this study indicated that a decrease in elastic modulus associated with bleaching occurred, and that fluoride-containing toothpaste reversed this effect.

Effect of CPP-ACP paste on tooth mineralization: an FE-SEM study.

Milk and milk products, such as cheese, have been shown to exhibit anticariogenic properties in human and animal models. CPP-ACP shows an anti-caries effect by suppressing demineralization, enhancing remineralization, or possibly a combination of both. The purpose of this study was to evaluate the effect of CPP-ACP paste on demineralization by observing the treated tooth surface using an FE-SEM. The specimens were prepared by cutting enamel and dentin of bovine teeth into blocks. A few specimens were stored in 0.1 M lactic acid buffer solution for 10 min and then in artificial saliva (negative control). The remaining specimens were stored in a 10 times-diluted solution of CPP-ACP paste or a placebo paste containing no CPP-ACP for 10 min, followed by 10 min immersion in a demineralizing solution (pH = 4.75, Ca) twice a day before storage in artificial saliva. After treatment of the specimens for 3, 7, 21 and 28 days, they were fixed in 2.5% glutaraldehyde in cacodylate buffer solution, dehydrated in ascending grades of tert-butyl alcohol, and then transferred to a critical-point dryer. The surfaces were coated with a thin film of Au in a vacuum evaporator, and were observed under field emission-scanning electron microscopy (FE-SEM). The SEM observations revealed different morphological features brought about by the various storage conditions. Demineralization of the enamel and dentin surfaces was more pronounced with the longer test period in the control and negative control specimens. On the other hand, enamel and dentin specimens treated with CPP-ACP paste revealed slight changes in their morphological features. From the morphological observations of the enamel and dentin surfaces, it could be considered that the CPP-ACP paste might prevent demineralization of the tooth structure.