Biomedical subjects

Yong-Keun Lee

Publications and source records attributed to Yong-Keun Lee.

At least 19 recordsLinked to original sources

PubMed2007

Changes in scattering and absorption properties of esthetic filling materials after aging.

OBJECTIVES: Assuming that color changes after aging are related to changes in translucency of materials, the purpose of the present study was to determine the correlation between the changes in color and the changes in scattering and absorption properties after accelerated aging with representative dental esthetic restorative materials: glass ionomer, resin-modified glass ionomer, compomer, and resin composite. METHODS: Color was measured according to the CIELAB color scale in the transmittance and reflectance modes and used to calculate changes in color (deltaE*(ab)), color coordinates (deltaL*, delta a*, and delta b*), translucency parameter (deltaTP), scattering coefficient (deltaS), absorption coefficient (deltaK), and light reflectivity (deltaRI) after accelerated aging. Simple correlations between each pair of the changes in optical values were calculated, and multiple regression analysis was used to determine the parameters influencing the changes in color and color coordinates (p = 0.05). RESULTS: In the resin composite and compomer, deltaS, deltaK, and deltaRI values were approximately zero, whereas deltaS was as high as 8.9 in the glass ionomer. For most comparisons, correlation coefficient (r) was between 0.700 and 0.997. DeltaL* was found to have a major influence on color changes, and deltaS, deltaTP, and deltaRI influenced deltaL*. Therefore, changes in scattering and absorption properties, after aging, were closely correlated with changes in color and color coordinates, especially in glass ionomer-based filling materials.

Acrylic Resins↗

PubMed2007

The effect of nanofiller on the opacity of experimental composites.

The purpose of this study was to evaluate the effect of the nanofiller in experimental composites on opacity (contrast ratio). Thirteen experimental composites were prepared with three different sizes of fillers: barium glass minifiller (1 microm; 69-76 wt %), silica microfiller (0.04 microm; 0-6 wt %), and silica nanofiller (7 nm; 0-7 wt %). After disk-type specimens were irradiated with a halogen light curing unit at 500 mW/cm(2) for 30 s, the specimens were aged for 6 h at room conditions and were stored in deionized water for 1, 7, 14, 21, 28, 56, and 84 days. The contrast ratios of the specimens were measured as a function of aging period using a spectrophotometer. The distribution morphology of the filler particles in the resin matrix was also examined using energy-filtering transmission electron microscopy. The experimental composites that contained more than 3% nanofiller had significantly lower contrast ratios (p < 0.05). The composites that contained 6 wt % nanofiller had contrast ratios 34-65% lower than the composite that did not contain nanofiller. The values of the contrast ratio from the composites that excluded microfiller were lower than the values from the composites that included microfiller. From the comparison with the 3 different sizes of filler, the contrast ratio of the composite that contained 70 wt % minifiller and 6 wt % microfiller was the highest, the contrast ratio of the composite that contained only 76 wt % minifiller was the median value, and the contrast ratio of the composite that contained 70 wt % minifiller and 6 wt % nanofiller was the lowest. When the microfiller content was decreased from 6 wt % to 0 wt %, the contrast ratio decreased 6-9%. Energy-filtering transmission electron microscopy images indicated that the contrast ratio of experimental composites is related to the distribution morphology of the filler particles in the resin matrix.

Acrylic Resins↗

PubMed2007

Changes in color and color parameters of dental resin composites after polymerization.

OBJECTIVES: The objectives were to measure the color change of varied shades of dental resin composites after polymerization, and to determine the correlation among the polymerization color change and the changes in color parameters after polymerization. METHODS: Eight light-curing resin composites, a total of 41 shades, were studied. Color of specimens (1 mm in thickness) was measured on a reflection spectrophotometer before and after polymerization over a white background. Changes in color (Delta E*(ab)), and color parameters (Delta L*, Delta C*(ab), Delta a*, and Delta b*: value after polymerization - value before polymerization) were calculated. RESULTS: The range of changes in each shade of resin composites was 1.1-7.9 for color (Delta E*(ab)), -7.5 to 2.3 for Delta L*, -6.8 to 3.1 for Delta C*(ab), -0.9 to 1.2 for Delta a*, and -6.8 to 3.1 for Delta b*. Delta E*(ab), Delta L*, Delta C*(ab), Delta a*, and Delta b* were influenced by the brand and shade of resin composites, and there was a significant interaction between two independent variables (p < 0.05). On the basis of the multiple regression analysis, in which Delta E*(ab) after polymerization was set as a dependent variable and Delta L*, Delta C*(ab), Delta a* and Delta b* as independent variables, multiple correlation coefficient (r) was 0.842 and the included predictors were Delta L* [standardized partial correlation coefficient (beta) = -0.760] and Delta C*(ab) (beta = -0.715). This result indicated that the polymerization changes in color and color parameters were varied by the brand and shade of resin composites, and the polymerization color change was caused by the changes in lightness and chroma with the similar power of influence.

Color↗

PubMed2007

Combined effect of staining substances on the discoloration of esthetic Class V dental restorative materials.

The purpose of this study was to determine the combined effect of an organic substance (mucin as a substitute for salivary organic substances), chlorhexidine, and an iron compound/tea solution on the changes in the color of esthetic Class V dental restorative materials. Color of a glass ionomer, resin-modified glass ionomer, compomer and flowable resin composite of A2 shade, respectively, was determined according to the CIELAB color scale relative to the standard illuminant D65. Color was measured at baseline, and after sequential immersion in the following substances: Step-1, mucin in PBS (MCP) for 48 h; Step-2, chlorhexidine (CHX) for 24 h; Step-3, iron compound (IRN) or tea solution (TEA) up to 7 days; and Step-4, ultrasonic cleaning for 1 h. Color change (DeltaE(ab )*) was calculated by the equation: DeltaE(ab)* = [(DeltaL*)(2) + (Deltaa*)(2) + (Deltab*)(2)](1/2), of which DeltaL(*) indicates changes in value, Deltaa(*) indicates changes in red-green parameter and Deltab(*) indicates changes in yellow-blue parameter. DeltaE(ab)* values after immersion in MCP and CHX were compared, and DeltaE(ab)* values after immersion in IRN or TEA, and subsequent ultrasonic cleaning were compared with respect to the restorative material and immersion substance. DeltaE(ab)* and changes in the color parameters (DeltaL(*), DeltaC(ab)* and DeltaH(ab)*) were analyzed by repeated measures, analysis of variance and a post-hoc test at the 0.05 level of significance. Color changes after immersion in MCP were acceptable (DeltaE(ab)* < 3.3), and those after immersion in CHX were generally acceptable. The range of DeltaE(ab)* values after immersion in IRN was 3.1-19.6, and that after ultrasonic cleaning was 2.4-9.6. The range of DeltaE(ab)* values after immersion in TEA was 10.7-21.1, and that after ultrasonic cleaning was 11.9-14.5. Color changes of four Class V restorative materials after combined treatment with mucin, chlorhexidine and an iron compound/tea solution were not acceptable. Colors did not recover to their original values after ultrasonic cleaning. Modifications on the surface of a restoration should be considered to reduce stain accumulation.

Acrylic Resins↗

PubMed2006

Fluorescent emission of varied shades of resin composites.

OBJECTIVES: The objectives of this study were to measure the fluorescent emission and the corresponding color difference by the inclusion and exclusion of the UV component of the standard illuminant D65 of varied shades of commercial resin composites, and to determine the influence of the color parameters and difference in color parameters by the UV component on the color difference caused by the fluorescent emission. METHOD: Eight light-curing resin composites, a total of 41 shades, were studied. Color and spectral reflectance of specimens, 12 mm in diameter and 1mm in thickness, were measured on a reflection spectrophotometer. An UV filter was adjusted to 100% or 0% location to include or exclude the UV component of the standard illuminant D65. From the spectral reflectance values, subtraction spectrum by the inclusion or exclusion of the UV component was calculated, and fluorescence peak height was determined. Color difference caused by the inclusion or exclusion of the UV component (DeltaE*(ab)-FL) was calculated. Differences in color coordinates (DeltaL*, Deltaa* and Deltab*) by the inclusion or the exclusion of the UV component were calculated. RESULTS: Fluorescence peak height and DeltaE*(ab)-FL were influenced by the brand and the shade of resin composites and there was a significant interaction between the variables based on two-way ANOVA (p<0.05). DeltaE*(ab)-FL was correlated with the chroma component of the shade, and also with Deltab* [standardized partial correlation coefficient (beta)=-0.699], DeltaL* (beta=0.464) and Deltaa* (beta=0.105) based on multiple regression analyses (p<0.05). CONCLUSION: Fluorescent emission was influenced by the brand and the shade of resin composites. Fluorescent resin composites showed color shift to blue direction and increased lightness under the UV included illumination.

Acrylic Resins↗

PubMed2006

Comparison of the color of natural teeth measured by a colorimeter and Shade Vision System.

OBJECTIVES: The objectives were to measure the difference in the color and color parameters of natural teeth measured by a tristimulus colorimeter (CM, used as a reference) and Shade Vision System (SV), and to determine the influence of color parameters on the color difference between the values measured by two instruments. METHOD: Color of 12 maxillary and mandibular anterior teeth was measured by CM and SV for 47 volunteers (number of teeth=564). Color parameters such as CIE L*, a* and b* values, chroma and hue angle measured by two instruments were compared. Chroma was calculated as C*ab=(a*2 = b*2)1/2, and hue angle was calculated as h degrees =arctan(b*/a*). The influence of color parameters measured by CM on the color difference (DeltaE*(ab)) between the values measured by two instruments was analyzed with multiple regression analysis (alpha=0.01). RESULTS: Mean DeltaE*(ab) value between the values measured by two instruments was 21.7 (+/-3.7), and the mean difference in lightness (CIE L*) and chroma was 16.2 (+/-3.9) and 13.2 (+/-3.0), respectively. Difference in hue angle was high as 132.7 (+/-53.3) degrees . Except for the hue angle, all the color parameters showed significant correlations and the coefficient of determination (r(2)) was in the range of 0.089-0.478. Based on multiple regression analysis, the standardized partial correlation coefficient (beta) of the included predictors for the color difference was -0.710 for CIE L* and -0.300 for C*(ab) (p<0.01). CONCLUSION: All the color parameters showed significant but weak correlations except for hue angle. When lightness and chroma of teeth were high, color difference between the values measured by two instruments was small. Clinical accuracy of two instruments should be investigated further.

Adult↗

PubMed2006

Combined effects of staining substances on resin composites before and after surface sealant application.

The objective was to measure the combined effect of mucin, chlorhexidine and tea solution on the staining of four dental resin composites, and to determine the effect of surface sealant on staining. One side of cured resin composite specimens of 10 mm in diameter and 2 mm in thickness were polished with 600-grit silicon carbide paper. One group of specimens (n = 5) was treated with a surface sealant [BisCover, Bisco, USA; SS (surface sealant) group], and the other group was not (NO group; control). Specimens were sequentially immersed in the following substances: Mucin in phosphate buffered saline (PBS); chlorhexidine; tea solution; and ultrasonic cleaning and then immersion in PBS. Color was measured on a reflection spectrophotometer. Changes in color (DeltaE (*) (ab)) and color parameters, such as hue, chroma and value, after immersion in tea solution and subsequent cleaning were analyzed by repeated measures, analysis of variance at the 0.05 level of significance. The range of DeltaE (*) (ab) values after immersion in tea solution was 11.4-21.1 for NO group and 10.5-19.6 for SS group, and that after cleaning was 2.4-10.0 for NO group and 2.7-8.3 for SS group. After staining, CIE L (*) value (lightness) decreased, and CIE a (*) and b (*) values increased. Color changes of resin composites were not acceptable after sequential immersion treatment (DeltaE (*) ( ab ) > 3.3). The changes in color and color parameters of sealant applied group were not significantly different from those of control group except for a few combinations of color parameters and resin composites.

Chlorhexidine↗

PubMed2006

Influence of fluorescent whitening agent on the fluorescent emission of resin composites.

OBJECTIVES: The objective of this study was to determine the fluorescent emission of experimental resin composites after addition of a fluorescent whitening agent in varied concentrations. The effects of thermocycling and composition of resin matrix on the fluorescent emission were also determined. METHODS: An experimental light curing resin matrix was made by mixing Bis-GMA, UDMA and TEGDMA in the ratio of 1:1:1 by weight, and silane coated glass filler was added in the ratio of 50 wt.% of resin composite. A fluorescent whitening agent [FWA, 1,4-double-(benzoxazole-group-2-group)naphthalene] was added with the concentration of 0.01-0.1%. To determine the difference by the resin matrix, two resin composites (60 wt.% Bis-GMA or UDMA with 40 wt.% TEGDMA) with the same filler content were made, and the FWA was added. Five specimens of 2mm in thickness were made for each group. Spectral reflectance was measured relative to the illuminant D65 on a reflection spectrophotometer. From the spectral reflectance values, the difference in reflectance (fluorescence spectra) by the inclusion or exclusion of UV component was calculated. After the baseline measurement, thermocycling was performed for 500 and 1000 cycles, and the fluorescent emission was measured again. RESULTS: The concentration of FWA influenced the fluorescent peak heights and areas (p<0.05), but thermocycling up to 1000 cycles did not influence the values. Fluorescence peak wavelength was not changed by the resin matrix, but peak height and area were influenced by the resin matrix (p<0.05). SIGNIFICANCE: FWA added with the concentrations of 0.01 and 0.05% emitted fluorescence, which was higher than those from commercial resin composites.

Analysis of Variance↗

PubMed2006

Changes in the translucency of porcelain and repairing resin composite by the illumination.

OBJECTIVES: The objectives were to evaluate the difference in the translucency parameter (TP) by the illuminants, to determine the correlation between the contrast ratio (CR) and three TP values relative to the illuminants, and to measure the correlation between the differences in TP (DeltaTP) and color (DeltaE(ab)*) by the illuminants based on dental porcelain and porcelain repairing resin composites. METHODS: Color and spectral reflectance of three shades of one dental porcelain and three porcelain repairing resin composites were measured before and after thermocycling for 3000 cycles relative to the CIE standard illuminants D65, A and F2 over a white and a black backgrounds. Specimen was 1.8mm in thickness after polishing. CR was calculated, and the differences in TP and color caused by the change of illuminants were compared. Three-way analysis of variance by the material (porcelain or resin composite), shade and illuminant was used to compare differences (alpha=0.05). RESULTS: The TP value was influenced by the illuminant (p<0.05), and the TP values relative to the illuminants A and F2 were higher than those relative to D65. The correlation coefficients between the CR and three TP relative to the three illuminants were around -0.95. Color difference was positively correlated with the difference in translucency in resin composites (r=0.65 between A and D65 and 0.47 between F2 and D65), but was negatively correlated in porcelain (r=-0.37 between A and D65 and -0.69 between F2 and D65). SIGNIFICANCE: Difference in translucency by illumination should be considered when matching shade of porcelain and repairing resin composite.

Analysis of Variance↗

PubMed2006

Metameric effect between dental porcelain and porcelain repairing resin composite.

OBJECTIVES: The objectives were to evaluate the metameric color and hue angle (degrees) changes between dental porcelain and porcelain repairing resin composites. METHODS: Color of three shades (A2, A3, A3.5) of one brand of dental porcelain and three original shades (A2, A3, A3.5) and three combinations (A2-A3, A3-3.5, A2-A3.5) of three brands of porcelain repairing resin composites (ABT, FSP, TCR) were measured relative to the three standard illuminants (D65, A and F2). Specimen was 2mm in thickness, and 1mm of each shade was layered to make combined shades. Color differences (DeltaEab*) between each shade of dental porcelain and repairing resin composites relative to the three illuminants were calculated, and the ratios of color difference (modified metamerism index) by the change of illuminant were calculated. The ratios of hue angle changes were also compared. RESULTS: Differences in modified metamerism index and the ratio of hue angle changes were influenced by the porcelain shade, brand of resin composites and shade of resin composites. In all three brands of resin composites, A3.5 shade showed the smallest values in modified metamerism index regardless of the shade of porcelain. The average ratio of hue angle changes between each porcelain shade and all the shades of each resin composites showed similar trend when illuminant was changed from D65 to F2. SIGNIFICANCE: Metameric effect between dental porcelain and repairing resin composites varied depending on the shade of porcelain, brand of resin composite and the illuminant. Therefore, shade matching between porcelain and repairing resin composite should be performed carefully. This study confirmed that shades should be matched under the light corresponding to that of use.

Analysis of Variance↗

PubMed2006

Color changes of resin composites in the reflectance and transmittance modes.

OBJECTIVES: The objective of this study was to evaluate the changes in color and color coordinates after accelerated aging of resin composites depending on the measuring modes of reflectance and transmittance. METHODS: Color of seven resin composites (1-mm thick specimens) was measured in the reflectance mode and in the transmittance mode. After the baseline color measurement, the specimens were aged for total energy of 150 kJ/m2. Color change after aging was calculated in the reflectance mode and in the transmittance mode. Based on the data of A2 shade composites, the influence of measuring mode on the color change (DeltaEab*) and changes in three color coordinates (DeltaL*, Deltaa* and Deltab*) after aging was analyzed by ANOVA (p<0.01). RESULTS: Measuring mode influenced DeltaEab*, DeltaL* and Deltaa* values. There were significant correlations between the color changes measured in the reflectance mode and in the transmittance mode (r=0.91). SIGNIFICANCE: The color changes in the transmittance mode can roughly be estimated based on the reflected color changes.

Analysis of Variance↗

PubMed2006

Influence of scattering/absorption characteristics on the color of resin composites.

OBJECTIVES: Optical scattering has been studied because of its important effects on the color and translucency of a material. The objective of this study was to determine the influence of the scattering and absorption characteristics including translucency and opalescence on the CIE color coordinates (L(*), a(*), and b(*)) of resin composites. METHODS: Color and spectral distribution of seven resin composites (14 shades, 1mm thick) were measured in the reflectance and the transmittance modes. Optical constants including scattering coefficient (S), absorption coefficient (K) and light reflectivity (RI) were calculated from the spectral reflectance data using Kubelka's equations. The opalescence parameter (OP) was calculated as the difference in yellow-blue (Deltab(*)) and red-green (Deltaa(*)) coordinates between the reflected and transmitted colors. The translucency parameter (TP) was calculated for the translucency evaluation. Simple correlation among each of CIE L(*), a(*) and b(*) values measured using varied protocols with optical parameters (S, K, RI, OP and TP) was determined, and multiple regression analysis was used to determine the significantly influencing variables on the color coordinates (p<0.05). RESULTS: CIE L(*), a(*), and b(*) values were influenced by S, K, RI, TP and OP values. The CIE L(*) value without backing and that in the transmission mode were highly correlated with S. OP and TP values also influenced CIE L(*) value. The CIE b(*) value was correlated with the OP value when different composites with the same shade designation were compared. SIGNIFICANCE: Since the scattering and absorption characteristics influence the color of resin composites, the size and volume fraction of fillers should be controlled for the best color reproduction, considering the refractive indices of filler and resin matrix.

Absorption↗

PubMed2006

Involvement of oxidative stress in mutagenicity and apoptosis caused by dental resin monomers in cell cultures.

OBJECTIVE: This investigation studied the possibility that apoptosis as well as mutagenicity induced by resin monomers are mediated by oxidative stress. METHODS: A range of dilutions of three resin monomers (GMA, TEGDMA, and HEMA) was added to culture medium (DMEM/10% FBS), of V79-4 fibroblasts and RPC-C2A pulp cells for 24 h. Their cytotoxic effects were measured by a colorimetric functional assay (MTT). Chromosomal aberration induced by the resin monomers was investigated by counting micronuclei in V79-4 cells. The effects of the resin monomers on DNA fragmentation were viewed by agarose gel electrophoresis of DNA, isolated from RPC-C2A pulp cells that were treated by resin compounds. Resin monomer-induced apoptosis was further confirmed by flow cytometry (staining with both annexin V-FITC and PI). RESULTS: All monomers exhibited a dose-dependent cytotoxic effect, and the ranking of the cytotoxicity based on TC50 was GMA > TEGDMA > HEMA. The resin monomer-induced cytotoxicity was significantly decreased by co-treatment with N-acetylcystein (NAC), an antioxidant. The authors also confirmed a dose-dependent genotoxicity of the resin monomers that had induced micronucleated cells in V79-4 fibroblasts. Similar to the effects on cytotoxicity, NAC reduced the numbers of micronuclei in comparison with those generated by the resin monomers. The preventive effects of NAC were also observed in monomer-induced apoptosis in RPC-C2A cells. A DNA ladder pattern, characteristic of apoptosis, was shown at cytotoxic concentrations, but NAC blocked the resin monomer-mediated DNA fragmentation. The preventive effects of NAC on apoptosis were confirmed by Annexin V staining. Cells exposed to 300 microM GMA, 7 mM TEGDMA, or 14 mM HEMA for 24 h showed a significant increase in apoptotic cells, while NAC co-treatment caused a reduction in apoptotic cells compared to controls. SIGNIFICANCE: These findings suggest that glutathione depletion and oxidative stress are responsible for GMA, TEGDMA, and HEMA-induced mutagenicity and apoptosis.

Animals↗

PubMed2006

Influence of fluorescent and opalescent properties of resin composites on the masking effect.

The objective of this study was to determine the influence of fluorescent properties in the reflectance and transmittance modes and opalescent properties and translucency under ultraviolet (UV)-included and -excluded conditions on the masking effect of commercial resin composites quantitatively. Color and spectral distribution of seven resin composites (14 shades) of 1-mm thick were measured in the reflectance and transmittance modes under UV-included and -excluded conditions. For the fluorescence evaluation, subtraction spectra by the inclusion and exclusion of the UV component of the illumination in the reflectance and transmittance modes were calculated. Opalescence parameter (DeltaO*(ab)) was calculated as the difference in yellow-blue (Deltab*) and red-green (Deltaa*) coordinates between the reflected and transmitted colors under UV-included and -excluded conditions. Under UV-included and -excluded conditions, translucency parameter (TP) was calculated and masking effect was calculated as the color difference between a specimen over a black tile and black tile itself. Fluorescent and opalescent properties varied by the brand and shade of composites and measurement protocols. Masking effect was correlated with TP values when TP values of materials were obviously different. But when TP values were in the similar range, the opalescent property influenced the masking effect of resin composites. The influence of fluorescent property on masking effect was also confirmed, although the degree of correlation was very low.

Biocompatible Materials↗

PubMed2006

Difference in color and color parameters between dental porcelain and porcelain-repairing resin composite.

The objective of this study was to measure the differences in color and color parameters between dental porcelain and porcelain-repairing resin composites. The colors of three shades (A2, A3, A3.5) of one brand of dental porcelain, three original shades (A2, A3, A3.5), and three combinations (A2/A3, A3/3.5, A2/A3.5) of three brands of porcelain-repairing resin composites (ABT, FSP, TCR) were measured. The specimens were 2 mm thick, and 1 mm of each shade was layered to make combined shades. Differences in color (DeltaE(ab) (*)), lightness (DeltaL*), chroma (DeltaC(ab) (*)), and hue (DeltaH(*)) between porcelain and resin composite were calculated. Color difference was calculated as DeltaE(ab) (*) = (DeltaL*(2) + Deltaa*(2) + Deltab*(2))(1/2), chroma difference was calculated as DeltaC(ab) (*) = (Deltaa*(2) + Deltab*(2))(1/2), and hue difference was calculated as DeltaH(ab) (*) = (DeltaE(ab) (*2) - DeltaL*(2) - DeltaC(ab) (*2))(1/2). The influence of porcelain shade, brand of resin composites, and shade of resin composites were analyzed by three-way analyses of variance, and the differential influence of color parameters on color difference was analyzed with multiple regression analysis (alpha = 0.05). Differences in color and color parameters were influenced by the porcelain shade, brand and shade of resin composites. The DeltaE(ab) (*) value was in the range of 2.2-16.9. The DeltaE(ab) (*) value was correlated with DeltaC(ab) (*) (standardized correlation coefficient, beta = - 0.85), DeltaL* (beta = - 0.52), and DeltaH(ab) (*) (beta = 0.08). Between the same shade designated pairs of porcelain and repairing composite, color difference was perceptible. Therefore, studies to improve the color matching between porcelain and repairing resin are recommended.

Color↗

PubMed2006

Influence of salivary organic substances on the discoloration of esthetic dental materials-a review.

The objective of this article was to review the articles on the interaction of salivary organic substances with resin-based dental materials and on the interaction of these organic substances with exogenous chemical agents, which results in discoloration. Original scientific articles or reviews on the saliva, acquired pellicle, and the interaction with pellicle and chemical agents related to dental resin-based materials were reviewed. Salivary esterases can increase or decrease the internal and external discoloration. The formation of acquired pellicle on the surface of a material varies by the properties of material, and the pellicle interacts with denaturation agents, such as tannin and chlorhexidine, to form stains and also adsorbs staining substances. Therefore, for the quality and longevity of restorations, protocols for the evaluation of the influence of organic substances on the extrinsic staining of restorative materials should be included in the evaluation of aesthetic restorative materials.

Dental Materials↗

PubMed2006

Influence of a series of organic and chemical substances on the translucency of resin composites.

The objective of this study was to investigate the changes in the translucency of resin composites following a series of immersion treatments in organic and chemical substances. Color of resin composites was measured according to the CIELAB color scale relative to the standard illuminant D65 over a white and a black background. Translucency parameter (TP) of resin composites was calculated at baseline, and after sequential immersion: Step 1, porcine liver esterase (a substitute for a salivary esterase); Step 2, organic substances (mucin and serum) and phosphate-buffered saline (PBS) as a control; Step 3, chemical alteration agents [chlorhexidine (CH) and carbamide peroxide (CP)]; and Step 4, 2% methylene blue. Porcine liver esterase caused small changes in TP (DeltaTP = -0.5 to 0.2). After Step 2, DeltaTP values of three groups were similar in the range of -0.7 to 1.2. After Step 3, DeltaTP values of all groups were small in the range of -1.5 to 2.2. After Step 4, DeltaTP values were high and differences that varied by the resin composite and the immersion protocol were clearly observed (DeltaTP = -13.4 to -2.5). Changes in TP were mainly influenced by resin composite. After Step 4, mucin and serum groups showed generally small changes in TP compared to PBS group. It is a possibility that the high changes in TP after immersion in methylene blue is an indication of dye absorption which might be an indication of the degree of resin composite degradation.

Animals↗

PubMed2006

Changes in color and translucency of porcelain-repairing resin composites after thermocycling.

The objective of this study was to determine the changes in color and translucency of dental porcelain-repairing resin composites compared to dental porcelain after thermocycling. Color and spectral reflectance of three shades (A2, A3, and A3.5) of one brand of dental porcelain and three basic shades (A2, A3, and A3.5) and three combinations (A2/A3, A3/3.5, and A2/A3.5) of three brands of porcelain-repairing resin composites (ABT, FSP, and TCR) were measured, before and after thermocycling for 3000 cycles, relative to the illuminant D65. The specimen was 2 mm in thickness, and 1 mm of each shade was layered to make combined shades. Changes in color (DeltaE*ab) and translucency parameter (DeltaTP) were calculated. A general linear model by the material (porcelain or resin composite) and shade was used to compare differences (alpha = 0.05). The range of color changes was 0.68-1.67 in porcelain, 0.56-1.30 in ABT, 2.28-3.10 in FSP, and 0.36-1.15 in TCR. The range of DeltaTP was 0.45-0.96 in porcelain, -0.48 to 0.94 in ABT, -1.31 to 0.82 in FSP, and -0.51 to 1.91 in TCR. After thermocycling, changes in color and TP were correlated with the shade of the material, but not with the material. The discrepancy in the changes of color and translucency after thermocycling between porcelain and porcelain-repairing resin composites should be considered when selecting repairing materials.

Color↗