Accelerated Aging Affects Color Stability of Provisional Restorative Materials

Purpose The color stability of two shades each of five acrylic resin and seven resin composite provisional restorative materials was evaluated by reflection spectrophotometry following in vitro accelerated aging. Materials and Methods Specimens of provisional restorative materials were polymerized according to manufacturers' instructions and aged in an artificial aging chamber with exposure to a total ultraviolet irradiation of 60 kj/m². Color was measured by CIE L*a*b* on a reflection spectrophotometer before and after aging. Color change (ΔE*) was calculated and analyzed statistically. Results Statistically significant changes in color were observed after accelerated aging. Nine of the 12 provisional materials tested showed perceptible color change of at least one of the shades tested. The most color-stable materials were the acrylic, Alike, and the resin composites, Luxatemp and Protemp Garant, which had no perceptible color changes under these conditions. Conclusions Some acrylic resin and composite provisional materials change color significantly and perceptibly when exposed to in vitro accelerated aging conditions.     

Microwave Pressure Chamber Processing of a Denture Repair Polymer

Most denture base repairs are made using a chemically activated acrylic resin polymer for reasons of cost and expediency. Heat-activated polymers are not typically used because they require a custom split cast gypsum mold, longer polymerization time, and higher laboratory fees. Repairs made using a chemically activated polymer compared with a heat-activated polymer generally have reduced transverse strength, poorer color stability, increased water sorption, and weak bond strength to existing acrylic resin. A method of utilizing a microwave polymer in a commercially available microwave flask is described. This technique allows denture base repairs to be made with a heat-activated polymer in a manner similar to that of chemically activated repairs.     

Color stability of provisional restorative materials after accelerated aging

PURPOSE: Color of 11 provisional restorative materials (4 acrylic resins and 7 resin composites) was evaluated by reflection spectrophotometry immediately after fabrication, after aging for 15 kJ/m(2), and after aging for 60 kJ/m(2) to determine relative color stability under experimental aging conditions. MATERIALS AND METHODS: Specimens of provisional restorative materials were polymerized according to manufacturers' instructions and aged in an artificial aging chamber with exposure to a total ultraviolet irradiation of 60 kJ/m(2) in increments of 15 kJ/m(2). Color was measured by CIE L*a*b* on a reflection spectrophotometer before and after aging. Color change (Delta E*) was calculated and analyzed statistically by analysis of variance with repeated measures after 15 and 60 kJ/m(2) intervals of aging. RESULTS: Statistically significant changes in color were observed after accelerated aging at both the initial and final aging intervals. Five of the 11 provisional materials tested showed perceptible color change (Delta E* from 3.6 to 9.3) after accelerated aging of 15 kJ/m(2). Seven of the 11 provisional materials tested showed perceptible color change (Delta E* from 3.4 to 9.4) after accelerated aging of 60 kJ/m(2). CONCLUSIONS: Clinically perceptible color changes (Delta E* Delta 3.3) can be expected in some acrylic resin and composite resin provisional materials after accelerated aging.     

Influence of Artificial Accelerated Aging on Dimensional Stability of Acrylic Resins Submitted to Different Storage Protocols

Purpose: The aim of this study was to evaluate the influence of artificial accelerated aging on dimensional stability of two types of acrylic resins (thermally and chemically activated) submitted to different protocols of storage. Materials and Methods: One hundred specimens were made using a Teflon matrix (1.5 cm × 0.5 mm) with four imprint marks, following the lost‐wax casting method. The specimens were divided into ten groups, according to the type of acrylic resin, aging procedure, and storage protocol (30 days). GI: acrylic resins thermally activated, aging, storage in artificial saliva for 16 hours, distilled water for 8 hours; GII: thermal, aging, artificial saliva for 16 hours, dry for 8 hours; GIII: thermal, no aging, artificial saliva for 16 hours, distilled water for 8 hours, GIV: thermal, no aging, artificial saliva for 16 hours, dry for 8 hours; GV: acrylic resins chemically activated, aging, artificial saliva for 16 hours, distilled water for 8 hours; GVI: chemical, aging, artificial saliva for 16 hours, dry for 8 hours; GVII: chemical, no aging, artificial saliva for 16 hours, distilled water for 8 hours; GVIII: chemical, no aging, artificial saliva for 16 hours, dry for 8 hours GIX: thermal, dry for 24 hours; and GX: chemical, dry for 24 hours. All specimens were photographed before and after treatment, and the images were evaluated by software (UTHSCSA – Image Tool) that made distance measurements between the marks in the specimens (mm), calculating the dimensional stability. Data were submitted to statistical analysis (two‐way ANOVA, Tukey test, p= 0.05). Results: Statistical analysis showed that the specimens submitted to storage in water presented the largest distance between both axes (major and minor), statistically different (p < 0.05) from control groups. Conclusions: All acrylic resins presented dimensional changes, and the artificial accelerated aging and storage period influenced these alterations.     

加速老化对光固化复合树脂色度和显微结构的影响

目的考察加速老化后光固化复合树脂的色度稳定性、表面显微结构和内部化学结构的改变及其相互之间的关系。方法用老化仪加速老化4种光固化复合树脂样本,测量老化24 h和96 h后的色差。用环境扫描电子显微镜和傅里叶变换红外光谱仪分别观察老化前后样本表面的显微结构和化学键的改变。用方差分析法分析老化时间与树脂色度间的交互影响（α=0.05）。结果老化时间与复合树脂类型之间具有交互作用（P<0.05）,老化后复合树脂的色度改变具有统计学意义（P<0.05）。老化对复合树脂表面显微结构具有明显的影响,老化后基质出现凹陷,填料颗粒暴露,出现孔隙。老化使树脂内部化学键发生变化,基质中的化学键削弱和裂解,不饱和残余物再度聚合。结论随着老化时间的延长,复合树脂的色度变化加大;老化后混合型填料树脂的色度稳定性最好;老化使复合树脂内部化学键发生变化,色度发生改变。     

Color stability of resin cements after accelerated aging

PURPOSE: To study the color stability of different resin cements after accelerated aging. METHODS: The color stability of a self-adhesive resin cement (Unicem), one resin-based composite cement (Variolink II), one compomer cement (Principle) and one hybrid ionomer cement (FujiCEM) was studied. Two curing modes of Unicem (self-cured and dual-cured) and Variolink II (light-cured and dual-cured) were also tested. Specimen disks (n = 5) were prepared with a polytetrafluoroethylene split mold and subjected to accelerated aging for 150, 300 and 450 kJ/m2. Color (CIELAB system) was measured before and after each of the three aging cycles on a reflection spectrophotometer. deltaE*, deltaL*, deltaC* and deltaH* were calculated and analyzed by ANOVA. RESULTS: The largest color change occurred during the first 150 kJ/m2 aging cycle, where deltaE* values ranged from 5.6 to 20.5 with Principle showing the least color change and FujiCEM the most. The color changes of all the tested materials were perceptible. The greatest changes were recorded for deltaL* and/or deltaC*. All specimens became significantly rougher and showed evidence of cracking and degradation after aging except Variolink II.     

Effect of 5.25 % Sodium Hypochlorite on Color Stability of Acrylic and Silicone Based Soft Liners and a Denture Base Acrylic Resin

The purpose of the current study was to investigate the effect of a chemical disinfectant (sodium hypochlorite 5.25 %) on color stability of a denture base acrylic resin and two processed soft denture lining materials of two different types (acrylic-based and silicone-based). Ten specimens from each type of materials tested were made (2 × 20 × 20 mm). All specimens were immersed in sodium hypochlorite (5.25 %). Colorimetric measurements for each specimen were taken before immersion, and after 24 h and 7 days of immersion. Color changes were evaluated using the CIE L*a*b* colorimetric system. Data were statistically analyzed with one-way analysis of variance (ANOVA) (α = 0.05). ANOVA was followed by Bonferroni test to determine which groups differed from each other. ΔE and ΔL* of the silicone-based liner at the 1st and 7th days of immersion were significantly more than of denture base acrylic resin and acrylic-based liner. Change in ΔL* values of denture base acrylic resin and acrylic-based liner was small and statistically insignificant after 24 h of its immersion. However, the increase in ΔL* values of the acrylic-based liner after 7 days of immersion was considerably more than of denture base acrylic resin. Color changes in denture base acrylic resin and soft denture liners tended to increase with longer immersion times, and the color stability of the soft denture liners was influenced by its chemical type.     

Denture base resins: comparison study of color stability.

Several denture base resins have been recently introduced that provide easier or faster processing. Although these materials have adequate strength properties, the color stability is also of interest. This study evaluated the color stability of five denture base acrylic resins and one denture base repair resin. The samples were subjected to conditions of accelerated aging to test color stability. Five samples of each material were processed and aged for 100 and 300 hours. The color stability was quantitatively measured using the Minolta Chroma Meter II. Color measurements were made before weathering and at 100 and 300 hours the color difference delta E was calculated for all samples. At 300 hours the color change of the materials was significantly different at p less than 0.01. It was found that: (1) the color of Lucitone Hy-pro and Acron was least affected by conditions of accelerated aging; (2) Triad, Accelar 20, and Perm demonstrated noticeable color changes; and (3) Compak-20 had an appreciable color change and was the least color-stable of the materials tested.     

紫外线照射老化树脂黏固剂对色度值及相对透明率的影响

目的探讨紫外线照射老化对4种树脂黏固剂颜色及相对透明率参数的影响。方法分别采用Biscem（双固化型）、Choice（光固化型）、PermaCem（化学固化型）和RelyX Aplicap（化学固化型）树脂黏固剂制取树脂试件,每种黏固剂制取5个试件,分别设为A、B、C、D组,按厂家推荐的方法光照或自然固化。在黑暗环境保持24 h后用色度计测量色度值CIE L*、a*、b*,并计算其相对透明率。然后将各组试件分别经紫外线照射老化8、16、24 h后再次测量,分析色度值和相对透明率的变化。结果4组树脂黏固剂试件在紫外线照射后均发生了颜色变化,照射时间越长色差值越大。照射时间相同时,4组试件的色差值不同,B组与D组的色差值较小,C组最大。A、B与D组的相对透明率受紫外线老化的影响较小,C组在紫外线照射后相对透明率发生改变。结论紫外线照射老化能够引起树脂黏固剂发生颜色改变,但是多数产品的相对透明率能够保持相对稳定。     

Color Stability of Hybrid Ionomers After Accelerated Aging

Purpose The color stability and surface roughness of three commercial hybrid ionomers were determined in vitro after accelerated aging. Three shades of each hybrid ionomer prepared in light-cured and dark-cured conditions were tested. Materials and Methods Samples were aged in an artificial aging chamber by subjecting them to total ultraviolet light irradiation of 150 kJ/m² over a period of 77 hours. Color (CIE LAB system) was measured before and after aging on a reflection spectrophotometer. Surface roughness was measured with a profilometer. Results After accelerated aging, all samples became lighter. Photac-Fil Aplicap (ESPE-Premier, Norristown, PA) and Fuji II LC (GC America, Chicago, IL) also became less chromatic (less red and less yellow). Among the light-cured samples, Fuji II LC had the greatest change in color followed by Photac-Fil Aplicap and Vitremer (3M Dental Products, St Paul, MN). For the dark-cured samples, Fuji II LC had the greatest change in color followed by Vitremer and Photac-Fil Aplicap. There were no differences in delta E* between the two lightest shades, but the darker shades of each product showed the greatest changes in color. All samples became significantly rougher after aging. Conclusions Hybrid ionomers changed color significantly and perceptibly after in vitro accelerated aging. Surfaces became significantly rougher and showed evidence of cracking and degradation.     

厚度和遮色剂对Artglass透光率的影响

目的：观察厚度和遮色剂对Artglass透光率的影响。方法：制作0．50、0．75、1．00、1．25、1．50、1．75、2．00mm厚、使用和不使用遮色剂的Arglass树脂片，分别测定其在标准白板和金属底板上的色度，计算色差，并用激光测定其透光率。结果：Artglass树脂的透光率随厚度增加呈对数下降，在相同厚度下，遮色组比无遮色组透光率明显降低。结论：树脂厚度和遮色剂对复合树脂的透光率有明显影响。由于树脂的透光率与其颜色有密切关系，在修复体制作时应考虑厚度的影响和遮色剂的正确应用。     

人工老化对不同厚度瓷聚体及不同类型树脂黏固材料颜色稳定性的影响

目的 评价人工老化后不同厚度瓷聚体与不同类型树脂黏固材料联合体的颜色稳定性,为临床合理选择和应用瓷聚体贴面以及粘接剂提供参考。方法 3种厚度（1.00、0.75、0.50 mm）瓷聚体Ceramage分别与光固化树脂水门汀RelyX Veneer、双固化树脂水门汀RelyX Unicem和流动树脂Filtek Z350 Flow共3种类型树脂黏固材料制备瓷聚体-树脂黏固材料联合体样本,共9组（每组5个样本）。所有样本同时放入氙灯老化仪中进行人工加速老化,采用分光光度仪测量老化前后样本的明度（L*）、红绿色品（a*）和蓝黄色品（b*）值,计算老化前后明度变化（ΔL）、红绿色品变化（Δa）、蓝黄色品变化（Δb）和色差（ΔE）。用双因素方差分析探讨瓷聚体厚度和树脂黏固材料类型对老化前后ΔE的影响。结果 瓷聚体厚度及树脂黏固材料类型对联合体老化前后ΔE均有影响,且两者间存在交互作用（P<0.05）。所有组ΔE均小于3.3,老化后L*、 a*、b*值均降低,且ΔL均小于2.0。结论 瓷聚体厚度与树脂黏固材料类型对瓷聚体-树脂黏固材料联合体的颜色稳定性有影响;联合体老化后的明度变化和色差均在临床可接受的范围内。     

The Effect of Polymerization Cycles on Color Stability of Microwave-Processed Denture Base Resin

Purpose: This study evaluated the effect of different microwave polymerization cycles on the color changes of a microwave-processed denture base resin after accelerated aging and immersion in beverages.
Materials and Methods: Specimens of light pink acrylic resin were divided into three groups according to polymerization cycle: (A) 500 W for 3 minutes, (B) 90 W for 13 minutes + 500 W for 90 seconds, and (C) 320 W for 3 minutes + 0 W for 4 minutes + 720 W for 3 minutes. Control groups were a heat-processed acrylic resin (T) and a chemically activated denture repair resin (Q). Eight specimens per group were aged in an artificial aging chamber and evaluated at 20, 192, and 384 hours. Another series of 40 specimens per group were immersed in water, coffee, tea, cola, or red wine and evaluated at 1, 12, and 36 days. Color was measured by a spectrophotometer before and after aging or immersion. Color changes (ΔE) were analyzed by ANOVA/Bonferroni t -test (α= 0.05).
Results: Mean ΔE (±SD) after 384 hours of accelerated aging were (A) 2.51 ± 0.50; (B) 3.16 ± 1.09; (C) 2.89 ± 1.06; (T) 2.64 ± 0.34; and (Q) 9.03 ± 0.40. Group Q had a significantly higher ΔE than the other groups. Color changes of immersed specimens were significantly influenced by solutions and time, but the five groups showed similar values. Mean ΔE at 36 days were (water) 1.4 ± 0.8; (coffee) 1.3 ± 0.6; (tea) 1.7 ± 0.5; (cola) 1.4 ± 0.7; and (red wine) 10.2 ± 2.7. Results were similar among the five test groups.
Conclusions: Color changes of the microwave-polymerized denture base resin tested were not affected by different polymerization cycles after accelerated aging or immersion in beverages. These changes were similar to the conventional heat-polymerized acrylic resin test, but lower than the repair resin after accelerated aging.     

厚度和遮色剂对Artglass颜色的影响

目的：测量Artglass DA3材料的标准色度及无限光学厚度，分析厚度和遮色剂对Artglass色度的影响。方法：测色仪器使用美能达CS-321型便携式色差仪。使用CIE L*a*b*比色系统描述试件颜色。△E表示两颜色之间的色度差异，由以下公式计算得出：△E=[(△L)^2 (△a)^2 (△b)^2]^1/2，将△E=1．5NBS(National Bureau of Standards)作为肉眼可察觉两物体颜色差异的界限值。制作厚度为4．0mm的Artglass试件，两片叠放，测量其色度作为标准色度。再用色差仪测试厚度，由4．0至0．5mm、每两组厚度间隔为0．25mm的15组试件在标准白板和金属底板上的色度，计算色差。铸造金属底板，涂布遮色剂，在其上分层堆塑3．5mm厚的Artglass材料，依次磨去0．25mm后测试其色度。结果：Artglass DA3色材料的标准色度值为L*61.23.a*-1．18，b*11．29，无限光学厚度在2．75mm左右。遮色剂可使Artglass的明度升高，色相偏红黄，这种影响直至修复体厚度为2．50mm时才能不为肉眼察觉。结论：Artglass的色度值在白色背景下随厚度增加而降低，厚度和遮色剂对Artglass的颜色有明显影响。     

Adaptation of acrylic resin dentures as influenced by the activation mode of polymerization

With the advent of newer methods of activation of the polymerization of denture base resins, there is a need to compare dentures constructed using various modes of activation such as heat, light, and microwave energy. This study compares the dimensional accuracy of a conventional heat-activated acrylic resin poly (methyl methacrylate) with a new pour resin, a visible light-activated resin, and microwave-activated acrylic resin, all polymerized for denture bases. All groups showed a processing contraction; the poorest-fitting group was processed in a brass flask and a water bath at 70-100 C, using a heat-activated resin (Acron); the relatively new light-activated resin (Triad) produced dentures of intermediate accuracy, as did Acupac 20, when either heat- or microwave-activated. The two best-fitting groups were prepared from an autopolymerizing resin (PERform) and the microwave-activated resin (Acron MC).     

热固化基托树脂外源性着色的体外研究

目的评价5种食物、药物对热固化基托树脂着色的程度。方法制作90块热固化基托树脂试件,随机分为6组,分别浸泡于蒸馏水(对照)、绿茶、橙汁、漱口水、药酒和黄连水中,用电子比色仪测量树脂浸泡前及浸泡1、2、3、4周后的颜色,得到L*、a*、b*值,计算各时间点与浸泡前的色差ΔE,进行统计学分析。结果除对照组外,5组实验组试件的ΔE值(颜色改变)均随浸泡时间延长而增大;不同浸泡液中试件的ΔE值有显著性差异,其大小顺序为:黄连水>漱口水>绿茶>药酒>橙汁。结论绿茶、橙汁、漱口水、药酒和黄连水均可导致热固化基托树脂表面着色,尤以黄连水着色最重。且随着时间延长,基托树脂表面着色加重。     

Influence of background color on the color changes of resin composites after accelerated aging

PURPOSE: To evaluate the changes in color and color coordinates after accelerated aging of resin composites depending on the background color. METHODS: Color of seven resin composites (14 shades, 1 mm-thick) was measured in the reflectance mode over a zero calibration box, a white background, and a black background. After baseline color measurement, specimens were aged for total energy of 150 kJ/m2. Color change after aging was calculated over three backgrounds. Based on the data of A2 shade composites, the influence of the background color on the changes in color (deltaE*ab) and changes in three color coordinates (deltaL*, deltaa* and deltab*) after aging was analyzed by ANOVA (P < 0.01). Correlation among the color changes over three backgrounds was determined with a linear regression analysis. RESULTS: Background color influenced deltaE*ab, deltaL*, deltaa* and deltab* values. There were significant correlations among the color changes over three backgrounds in the reflectance mode (r = 0.95-0.98).     

Color stability and hardness in dental composites after accelerated aging.

OBJECTIVES: To investigate the color and microhardness changes of five chemically- and five light-curing composites as a function of accelerated aging from light exposure. MATERIALS AND METHODS: From each material five composite specimens were embedded in epoxy resin prior to determining the Knoop microhardness of the surface. For analyzing the color DeltaE*=f((L*a*b*)) with a spectrophotometer, three discs per composite were prepared. After measuring the baseline for hardness and color the same specimens were exposed to a xenon arc light and water in a Weather-Ometer machine for a total radiant energy of 150 kJ/m2 and 122 h. The microhardness and the color were again determined following the aging treatment. RESULTS: Each material showed a significant increase in hardness after aging treatment (p<0.05). Comparing the hardness changes (in %) of the light-cured materials with the chemically cured materials, no significant difference could be found. Perceptible color differences could be observed for all the materials. Three brands showed small differences with DeltaE*=1.6-2.2, while four composites had DeltaE* ranging from 6.2 to 15.5. A significant correlation between hardness values and color changes could not be established. CLINICAL SIGNIFICANCE: The findings suggest that, since light-curable materials showed significantly more resistance to color changes after accelerated aging by light and water than chemically-cured materials, they may be more esthetically acceptable. Color changes were not correlated with surface hardness changes of the materials after aging.     

体层厚度对Ceramage聚合瓷树脂修复体颜色的影响

目的研究体层树脂厚度的变化对Ceramage聚合瓷树脂修复体颜色的影响。方法制作遮色层厚度为0.2mm、体层厚度分别为0.8、1.0、1.2、1.4、1.6mm的A2色Ceramage聚合瓷树脂试件,同时制作厚度10mm无遮色层的体层树脂试件作为对照组。使用Vita Easyshade电脑比色仪测定各组试件的L*、a*、b*值,并计算各厚度组与对照组之间色差值⊿E。结果随着体层厚度的增加,试件的L*值、a*值与b*值均逐渐降低,1.4mm和1.6mm厚度组与对照组之间的色差值⊿E小于1.5NBS。结论在临床适用范围内,体层树脂厚度变化对聚合瓷修复体的颜色有影响。当遮色层厚度为0.2mm时,体层树脂在1.4～1.6mm左右的厚度范围内,A2色Ceramage聚合瓷修复体能较理想再现选定的颜色。