The effect of repeated firings on the color change and surface roughness of dental ceramics

PURPOSE

The color of the ceramic restorations is affected by various factors such as brand, thickness of the layered the ceramic, condensation techniques, smoothness of surface, number of firings, firing temperature and thickness of dentin. The aim of this study was to evaluate the color change and surface roughness in dental porcelain with different thicknesses during repeated firings.

MATERIALS AND METHODS

Disc-shaped (N=21) metal-ceramic samples (IPS Classic; Ivoclar Vivadent; Shaar, Liechtenstein) with different thickness were exposed to repeated firings. Color measurement of the samples was made using a colorimeter and profilometer was used to determine surface roughness. ANOVA and Tukey tests with repeated measurements were used for statistical analysis.

RESULTS

The total thickness of the ceramics which is less than 2 mm significantly have detrimental effect on the surface properties and color of porcelains during firings (P<.05).

CONCLUSION

Repeated firings have effects on the color change and surface roughness of the dental ceramics and should be avoided.     

The effect of repeated firings on the color change of dental ceramics using different glazing methods

PURPOSE

Surface color is one of the main criteria to obtain an ideal esthetic. Many factors such as the type of the material, surface specifications, number of firings, firing temperature and thickness of the porcelain are all important to provide an unchanged surface color in dental ceramics. The aim of this study was to evaluate the color changes in dental ceramics according to the material type and glazing methods, during the multiple firings.

MATERIALS AND METHODS

Three different types of dental ceramics (IPS Classical metal ceramic, Empress Esthetic and Empress 2 ceramics) were used in the study. Porcelains were evaluated under five main groups according to glaze and natural glaze methods. Color changes (ΔE) and changes in color parameters (ΔL, Δa, Δb) were determined using colorimeter during the control, the first, third, fifth, and seventh firings. The statistical analysis of the results was performed using ANOVA and Tukey test.

RESULTS

The color changes which occurred upon material-method-firing interaction were statistically significant (P<.05). ΔE, ΔL, Δa and Δb values also demonstrated a negative trend. The MC-G group was less affected in terms of color changes compared to other groups. In all-ceramic specimens, the surface color was significantly affected by multiple firings.

CONCLUSION

Firing detrimentally affected the structure of the porcelain surface and hence caused fading of the color and prominence of yellow and red characters. Compressible all-ceramics were remarkably affected by repeated firings due to their crystalline structure.     

排龈技术在牙体缺损修复中的应用

目的观察排龈对3MZ250复合树脂修复牙体缺损疗效的影响。方法选择31例120颗唇颊面牙颈部龋缺损牙,随机分为实验组和对照组,每组60颗,经窝洞预备后,实验组排龈线排龈后3MZ250复合树脂修复,对照组直接树脂修复,随访2年,评价修复体保存、继发龋以及边缘密合状况。结果充填后1周复查,使用排龈线组修复后悬突的发生率低于对照组,差异有显著性（P〈0．01）。充填后0．5年复查两组脱落率无明显差异;1年及2年后复查实验纽充填体的脱落率明显低于对照组（P〈0．05）。结论排龈可提高3MZ250复合树脂修复牙体缺损的修复体保存率,可以作为一项常规使用措施。     

个性化复合树脂分层修复比色板的设计与临床应用

目的 为方便临床医师在应用复合树脂修复牙齿缺损时进行比色,设计一种牙科复合树脂分层修复比色系统.方法 本比色系统包括比色板底板,复合树脂比色片及比色片制作模具3个部分,可以实现对牙齿不同位置进行精准比色并定量明确各区域所使用树脂的种类及对应的厚度.选取54名患者的87颗缺损前牙,分别使用个性化比色板+分层复合树脂修复及...     

六种常用冠修复材料的摩擦磨耗性能比较

目的 探讨6种常用冠修复材料与滑石瓷对磨时的摩擦磨耗性能,为口腔常用冠修复材料的摩擦磨耗性能与牙釉质的匹配性提供依据.方法 使用MMJ-5G微机控制高温端面磨损实验机,以滑石瓷为对磨物,以15颗因正畸拔除的上颌第一前磨牙制作的10个试件为对照组,对纯钛(A组)、钴铬合金(B组)、Superporcelain Ti-22体瓷(C组)、喜美乐体瓷(D组)、松风饰瓷(E组)、e.max饰瓷(F组)(每组均为10个试件)与滑石瓷组成的摩擦副在37℃人工唾液润滑工况下进行摩擦磨耗实验.记录动态摩擦系数曲线、计算体积磨损百分比,扫描电镜观察表面磨损形貌.结果 试件体积磨损百分比由大至小为:对照组[(90.17×10-4)％]、A组[(79.23×10-4)％]、C组[(23.31 ×10-4)％]、D组[(20.41×10-4)％]、F组[(19.22 × 10-4)％]、E组[(8.53 × 10-4)％]、B组[(2.54×10-4)％].滑动摩擦系数由大到小依次是:D组(0.65)、C组(0.45)、E组(0.40)、A组(0.35)、B组和F组(0.30).扫描电镜观察显示,E组表面最光滑,以下依次是F组、D组、C组.结论 纯钛与天然牙磨耗性能相近,是理想的修复金属材料.4种瓷粉中Surperporcelain Ti-22体瓷磨损滑石瓷最少.     

Color and luminescence stability of selected dental materials in vitro

Purpose: To study luminescence, reflectance, and color stability of dental composites and ceramics. Materials and Methods: IPS e.max, IPS Classic, Gradia, and Sinfony materials were tested, both unpolished (as‐cast) and polished specimens. Coffee, tea, red wine, and distilled water (control) were used as staining drinks. Disk‐shaped specimens were soaked in the staining drinks for up to 5 days. Color was measured by a colorimeter. Fluorescence was recorded using a spectrofluorometer, in the front‐face geometry. Time‐resolved fluorescence spectra were recorded using a laser nanosecond spectrofluorometer. Results: The exposure of the examined dental materials to staining drinks caused changes in color of the composites and ceramics, with the polished specimens exhibiting significantly lower color changes as compared to unpolished specimens. Composites exhibited lower color stability as compared to ceramic materials. Water also caused perceptible color changes in most materials. The materials tested demonstrated significantly different initial luminescence intensities. Upon exposure to staining drinks, luminescence became weaker by up to 40%, dependent on the drink and the material. Time‐resolved luminescence spectra exhibited some red shift of the emission band at longer times, with the lifetimes in the range of tens of nanoseconds. Conclusions: Unpolished specimens with a more developed surface have lower color stability. Specimens stored in water develop some changes in their visual appearance. The presently proposed methods are effective in evaluating the luminescence of dental materials. Luminescence needs to be tested in addition to color, as the two characteristics are uncorrelated. It is important to further improve the color and luminescence stability of dental materials.     

Color stability of glazed and polished dental porcelains.

PURPOSE: The purpose of this study was to compare the visual and colorimetric color stability of two ultra low-fusing and three conventional low-fusing porcelains on both glazed and polished surfaces. MATERIALS AND METHODS: Twelve disks, 10 mm in diameter and 3 mm in thickness, were fabricated for each porcelain. Specimens were glazed using their specific glaze materials. For each type of porcelain, the specimens were divided into two groups: one group was immersed in methylene blue and the other group in distilled water as a control. The surfaces were visually examined for staining without magnification. Objective color measurement was performed for each sample using a Tristimulus colorimeter. After examining the color of the glazed specimens, glazed layers were removed from the surface of the specimens to simulate an intraoral environment. Then, porcelain polishing points and diamond polishing paste were applied. The samples were immersed again in methylene blue and distilled water, and after removing from the staining solution and distilled water, visual and objective measurements were performed again. RESULTS: Visually discernible stain was present on the polished groups of all five porcelains immersed in methylene blue, whereas the glazed group immersed in methylene blue showed no staining. No staining was observed with glazed and polished samples immersed in distilled water. The objective evaluation showed that the polished porcelain surface of all five porcelain products had statistically significant color deviation than the glazed surface in the same group after immersion in methylene blue. The results of this study show a statistically significant difference in color stability between the polished and glazed specimens. CONCLUSION: It may be concluded that the glazed specimens showed a better color stability, although the staining observed in the polished specimens was not clinically noticeable.     

Composite resin color stability: influence of light sources and immersion media

Objective

This study evaluated the influence of light sources and immersion media on the color stability of a nanofilled composite resin.

Material and Methods

Conventional halogen, high-power-density halogen and high-power-density light-emitting diode (LED) units were used. There were 4 immersion media: coffee, tea, Coke^® and artificial saliva. A total of 180 specimens (10 mm x 2 mm) were prepared, immersed in artificial saliva for 24 h at 37±1ºC, and had their initial color measured with a spectrophotometer according to the CIELab system. Then, the specimens were immersed in the 4 media during 60 days. Data from the color change and luminosity were collected and subjected to statistical analysis by the Kruskall-Wallis test (p<0.05). For immersion time, the data were subjected to two-way ANOVA test and Fisher''s test (p<0.05).

Results

High-power-density LED (∆E=1.91) promoted similar color stability of the composite resin to that of the tested halogen curing units (Jet Lite 4000 plus - ∆E=2.05; XL 3000 - ∆E=2.28). Coffee (∆E=8.40; ∆L=-5.21) showed the highest influence on color stability of the studied composite resin.

Conclusion

There was no significant difference in color stability regardless of the light sources, and coffee was the immersion medium that promoted the highest color changes on the tested composite resin.     

Effect of the applied load on surface contact fatigue of dental filling materials

OBJECTIVE: The purpose of this study was to investigate the effect of the applied load in a rolling-ball device on the surface contact fatigue of two dental filling materials: a microfilled composite (FA) and a glass ionomer (GFII). METHODS: Disk specimens 10 mm diameter by 1.5 mm thick were set into cavities cut in plates of PMMA. After setting, the specimens were ground and polished using wet-carborundum paper followed by 1 microm alumina and then stored for 24 h in water at 23 degrees C. The surface fatigue test was carried out using loads ranging from 100 to 500 gf through a ruby ball 2 mm diameter using a rolling-ball device. The ball was set to rotate at 720 rpm and a surface profile was determined on impressions recorded at regular intervals. Fatigue life was defined as the number of cycles to produce a track 5 microm deep and was determined by interpolation. Data were statistically analyzed by ANOVA and t-tests at a significance level of 0.05. RESULTS: At loads ranging from 200 to 500 gf the fatigue life was 0.7-10.6 x 10(5) cycles for FA, and 0.7-4.8 x 10(3) cycles for GFII. For both materials the fatigue life was reduced significantly by increasing the test load (p<0.05). The surface contact fatigue life for FA was at least 100 times greater than that for GFII at all loads. SIGNIFICANCE: The rolling ball device was confirmed as a simple and meaningful device for the study of surface contact fatigue. A microfilled composite is very much more resistant to contact fatigue than a glass ionomer.     

Resin based restorative dental materials: characteristics and future perspectives

This review article compiles the characteristics of resin based dental composites and an effort is made to point out their future perspectives. Recent research studies along with few earlier articles were studied to compile the synthesis schemes of commonly used monomers, their characteristics in terms of their physical, mechanical and polymerization process with selectivity towards the input parameters of polymerization process. This review covers surface modification processes of various filler particles using silanes, wear behaviour, antimicrobial behaviour along with its testing procedures to develop the fundamental knowledge of various characteristics of resin based composites. In the end of this review, possible areas of further interests are pointed out on the basis of literature review on resin based dental materials.     

Early cell response of osteogenic cells on differently modified implant surfaces: Sequences of cell proliferation,adherence and differentiation

Objectives

Osseointegration of dental implants is a crucial prerequisite for long-term survival. Therefore, surface modifications are needed to interact with the extracellular environment and to trigger osteogenic cell responses such as cell proliferation, adherence, and differentiation. The purpose of this study was to investigate different surface modifications in vitro over 2 weeks.

Effect of polishing and glazing on the color and spectral distribution of monolithic zirconia

PURPOSE

The aim of this study was to evaluate the effect of polishing and glazing on the color and spectral distribution of monolithic zirconia.

MATERIALS AND METHODS

Forty-five monolithic zirconia specimens (16.3 mm × 16.4 mm × 2.0 mm) were fabricated and divided into 5 groups according to the number of A2-coloring liquid applications (Group I to V). Each group was divided into 3 subgroups according to the method of surface treatments (n=3): N: no treatment; P: polishing; G: glazing. Color and spectral distribution of five different areas of each specimen were measured according to CIELAB color space in the reflectance mode relative to the standard illuminant D65 on a reflection spectrophotometer. Data were analyzed using one-way ANOVA followed by Tukey''s HSD test, Pearson correlation and regression analysis (α=.05).

RESULTS

There was a significant difference in CIE L^* between Subgroup N and P, and in CIE b^* between Subgroup P and G in each group. Spectral reflectance generally decreased in Subgroup P and G in comparison with Subgroup N. Color differences between Subgroup P and G were within the perceptibility threshold (ΔE^*_ab< 3.7) in most groups. Highly significant correlation was found between CIE b^*and each subgroups as the number of coloring liquid applications increased (R²>0.88, P<.001).

CONCLUSION

A perceptible color difference can be detected after polishing of monolithic zirconia. Polishing decreases the lightness, and glazing also decreases the lightness, but increases the yellowness of monolithic zirconia.     

Effect of the amount of thickness reduction on color and translucency of dental monolithic zirconia ceramics

PURPOSE

This study investigated the effect of amount of thickness reduction on color and translucency of dental monolithic zirconia ceramics.

MATERIALS AND METHODS

One-hundred sixty-five monolithic zirconia specimens (16.3 mm × 16.3 mm × 2.0 mm) were divided into 5 groups (Group I to V) according to the number of A2-coloring liquid applications. Each group was then divided into 11 subgroups by reducing the thickness up to 1.0 mm in 0.1-mm increments (Subgroup 0 to 10, n=3). Colors and spectral distributions were measured according to CIELAB on a reflection spectrophotometer. All measurements were performed on five different areas of each specimen. Color difference (ΔE^*_ab) and translucency parameter (TP) were calculated. Data were analyzed using one-way ANOVA and multiple comparison Scheffé test (α=.05).

RESULTS

There were significant differences in CIE L^* between Subgroup 0 and other subgroups in all groups. CIE a^* increased (0.52<R²<0.73), while CIE b^* decreased (0.00<R²<0.74) in all groups with increasing thickness reduction. Perceptible color differences (ΔE^* _ab>3.7) were obtained between Subgroup 0 and other subgroups. TP values generally increased as the thickness reduction increased in all groups (R²>0.89, P<.001).

CONCLUSION

Increasing thickness reduction reduces lightness and increases a reddish, bluish appearance, and translucency of monolithic zirconia ceramics.     

饰面瓷表面粗糙度对全瓷修复体颜色及透射率的影响

目的：探讨不同饰面瓷表面粗糙度对全瓷修复体颜色及透射率的影响。方法：将Cercon氧化锆陶瓷材料和IPS e.max铸瓷材料分别制作成厚2.0 mm、直径15 mm的圆盘状试件,各分为4组,每组5个试件,试件表面分别用水砂纸打磨至400#、600#、800#、1000#,测量其表面粗糙度Ra值、L*a*b*颜色参数及透射率。结果：随着饰面瓷表面粗糙度的增加,Cercon氧化锆的明度L*值呈增大趋势,b*值呈减小趋势,IPS e.max热压铸瓷的L*、a*、b*值无明显变化趋势;可见光透射率呈上升趋势。结论：不同饰面瓷表面粗糙度对Cercon氧化锆和IPS e.max全瓷修复体的颜色及透射率有一定影响。     

Wear of 3D printed and CAD/CAM milled interim resin materials after chewing simulation

PURPOSEThe purpose of this in vitro study was to investigate the wear resistance and surface roughness of three interim resin materials, which were subjected to chewing simulation.MATERIALS AND METHODSThree interim resin materials were evaluated: (1) three-dimensional (3D) printed (digital light processing type), (2) computer-aided design and computer-aided manufacturing (CAD/CAM) milled, and (3) conventional polymethyl methacrylate interim resin materials. A total of 48 substrate specimens were prepared. The specimens were divided into two subgroups and subjected to 30,000 or 60,000 cycles of chewing simulation (n = 8). The wear volume loss and surface roughness of the materials were compared. Statistical analysis was performed using one-way analysis of variance and Tukey''s post-hoc test (α=.05).RESULTSThe mean ± standard deviation values of wear volume loss (in mm³) against the metal abrader after 60,000 cycles were 0.10 ± 0.01 for the 3D printed resin, 0.21 ± 0.02 for the milled resin, and 0.44 ± 0.01 for the conventional resin. Statistically significant differences among volume losses were found in the order of 3D printed, milled, and conventional interim materials (P<.001). After 60,000 cycles of simulated chewing, the mean surface roughness (Ra; μm) values for 3D printed, milled, and conventional materials were 0.59 ± 0.06, 1.27 ± 0.49, and 1.64 ± 0.44, respectively. A significant difference was found in the Ra value between 3D printed and conventional materials (P=.01).CONCLUSIONThe interim restorative materials for additive and subtractive manufacturing digital technologies exhibited less wear volume loss than the conventional interim resin. The 3D printed interim restorative material showed a smoother surface than the conventional interim material after simulated chewing.     

Color change of airborne particle–abraded acrylic resin surfaces: A palatography method

Statement of problem

A palatogram aids prosthodontists and speech pathologists in evaluating the precise prosthetic treatment needed and the effectiveness of such treatment to improve speech intelligibility. Powder is commonly used to visualize tongue-palate contact, where wetted areas of powder in the oral cavity reveal such contact during palatography. However, discomfort and the risk of aspiration are among the shortcomings of this method, and an improved method is needed.

不同消毒方式对口腔印模消毒效果、线性尺寸变化及细节再现性的影响

目的 研究不同消毒方式对口腔印模材料消毒效果、线性尺寸变化及细节再现性的影响。方法根据印模材料（藻酸盐、聚醚和硅橡胶），消毒剂（次氯酸钠、戊二醛），消毒方法（喷洒、浸泡），以及不同消毒浓度和消毒时间等进行实验分组，并设未消毒处理组作为空白对照，共计15组，通过涂布平板法进行菌落计数以实施印模消毒效果试验，并利用细节再现性试验块及配套环形模具实施线性尺寸变化和细节再现试验。结果 藻酸盐印模样品需经0.5%次氯酸钠喷洒消毒10 min后方可达到印模消毒要求；硅橡胶（重体+轻体）印模样品需在0.5%次氯酸钠或2%戊二醛浸泡消毒10 min后才可达到印模消毒要求；而聚醚和硅橡胶（重体）印模样品在用0.5%次氯酸钠浸泡消毒5～10 min或2%戊二醛浸泡消毒10 min后均符合印模消毒要求。所有组印模材料样品消毒前后的线性尺寸变化和细节再现性试验结果均符合要求。结论 不同消毒方式对印模材料消毒后的线性尺寸变化及细节再现性均符合要求，但从消毒的有效性考虑，藻酸盐印模材料可选用0.5%次氯酸钠喷洒消毒10 min，聚醚印模材料可选用0.5%次氯酸钠浸泡消毒5～10 min或2%戊二醛浸泡消毒10 m...     

Surface hardness evaluation of different composite resin materials: influence of sports and energy drinks immersion after a short-term period

Objectives:

This study evaluated the effect of sports and energy drinks on the surface hardness of different composite resin restorative materials over a 1-month period.

Material and Methods:

A total of 168 specimens: Compoglass F, Filtek Z250, Filtek Supreme, and Premise were prepared using a customized cylindrical metal mould and they were divided into six groups (N=42; n=7 per group). For the control groups, the specimens were stored in distilled water for 24 hours at 37º C and the water was renewed daily. For the experimental groups, the specimens were immersed in 5 mL of one of the following test solutions: Powerade, Gatorade, X-IR, Burn, and Red Bull, for two minutes daily for up to a 1-month test period and all the solutions were refreshed daily. Surface hardness was measured using a Vickers hardness measuring instrument at baseline, after 1-week and 1-month. Data were statistically analyzed using Multivariate repeated measure ANOVA and Bonferroni''s multiple comparison tests (α=0.05).

Results:

Multivariate repeated measures ANOVA revealed that there were statistically significant differences in the hardness of the restorative materials in different immersion times (p<0.001) in different solutions (p<0.001). The effect of different solutions on the surface hardness values of the restorative materials was tested using Bonferroni''s multiple comparison tests, and it was observed that specimens stored in distilled water demonstrated statistically significant lower mean surface hardness reductions when compared to the specimens immersed in sports and energy drinks after a 1-month evaluation period (p<0.001). The compomer was the most affected by an acidic environment, whereas the composite resin materials were the least affected materials.

Conclusions:

The effect of sports and energy drinks on the surface hardness of a restorative material depends on the duration of exposure time, and the composition of the material.     

抛光和自上釉对陶瓷表面平滑度的影响

目的：比较研究抛光和自上釉这两种不同的陶瓷表面处理方法，对陶瓷表面平滑度产生的影响。方法：分别以SEM和粗糙度测试仪，对抛光组和自上釉组的试件表面进行定量测试分析。试件的制作及处理均按照临床所用的常规方法。结果：SEM观察表明抛光组的平滑度与自上釉相似。经粗糙度测试仪测得的Ra值，抛光组为0.412μm，自上釉组为0．417μg。两者比较未见显著性差异（P＞0．05），且SEM的检查与Ra值的测定具有一致性。结论：采用抛光处理可以获得与自上釉相同平滑度的陶瓷表面。