|Year : 2020 | Volume
| Issue : 3 | Page : 322-328
Evaluation of the effect of various beverages on the color stability and microhardness of restorative materials
S Ozkanoglu1, EG G Akin2
1 Department of Restorative Dentistry, Faculty of Dentistry, Cumhuriyet University, Sivas, Turkey
2 Department of Restorative Dentistry, Faculty of Dentistry, Sakarya University, Sakarya, Turkey
|Date of Submission||06-Jun-2019|
|Date of Acceptance||28-Oct-2019|
|Date of Web Publication||5-Mar-2020|
Dr. S Ozkanoglu
Faculty of Dentistry, Department of Restorative Dentistry, Faculty of Dentistry, Cumhuriyet University, 58140 Sivas
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Objective: The aim of this in-vitro study was to investigate the effects of frequently consumed beverages on the color stability and microhardness of various restorative materials. Materials and Methods: Twenty-four samples were prepared in each group to examine the effect of different beverages on coloration and surface hardness of two direct composite resins (Filtek Z250, Filtek Z550); one indirect composite resin (Solidex); and one high viscosity glass ionomer cement (Equia Forte Fil). Samples were stored in four solutions (distilled water, black tea, coffee, and cola) at room temperature for 1 week (n = 6). The color values are taken at the beginning and the color and microhardness values taken at the end of 1 week were evaluated by the Kruskal–Wallis and Mann–Whitney U tests. Results: The highest color change was observed in the Equia Fil, while the least color change was observed in the Z550 group. The highest degree of color change was observed in coffee and cola groups. While the lowest values of hardness were observed in the Solidex group, the highest values of hardness were observed in the Z550 group. The highest levels of hardness change were detected in the coffee and cola groups. Conclusion: The color and hardness of restorative materials can be negatively affected by consumed beverages. Nanohybrid composite resins are resistant to external coloration and hardness change.
Keywords: Beverage, discoloration, material, microhardness, restoration
|How to cite this article:|
Ozkanoglu S, G Akin E G. Evaluation of the effect of various beverages on the color stability and microhardness of restorative materials. Niger J Clin Pract 2020;23:322-8
|How to cite this URL:|
Ozkanoglu S, G Akin E G. Evaluation of the effect of various beverages on the color stability and microhardness of restorative materials. Niger J Clin Pract [serial online] 2020 [cited 2020 Apr 2];23:322-8. Available from: http://www.njcponline.com/text.asp?2020/23/3/322/280026
| Introduction|| |
With the changing concepts in the field of restorative dentistry, developments in the characteristics and composition of materials have gained in importance. In dental clinical applications, composite resins are among the most popular restorative materials because of the strengthening quality of their physical and mechanical properties, as well as their enhancement of esthetic properties. Today, in addition to the development of adhesive resins, the use of indirect composite materials have increased significantly as an alternative to direct composite restorations with the development of adhesive systems and techniques. The esthetics of these materials, which have low polymerization shrinkage because of the formation outside of the mouth and the advantages of increasing the resistance of the tooth, as well as some negative clinical characteristics, directed the researchers to search for new materials.
Today, the focus of modern dentistry is on the minimal removal of dental tissue and the application of adhesive restorative materials that have a therapeutic effect on demineralized dentin. Nowadays, the newly developed high viscosity glass ionomer cements have been developed to increase the insufficient mechanical properties of conventional glass ionomer cements, increase the wear resistance against high occlusal forces, and to expand the use areas as a restorative material, which are limited by Class I and Class V cavities. These cements, which have similar curing mechanisms to conventional glass ionomer cements, have increased their resistance to abrasion resistance, surface hardness, bending, and compression forces, and their solubility has also been reduced. In addition, because of the release of fluoride and biocompatibility with tooth tissues, they have recently emerged as a new restorative system in the market.
In the oral cavity, dental restorations are exposed to a number of conditions that cause physical and mechanical change of the restorations, such as wear and discoloration. Thus, over time, the quality of the restoration deteriorates and then it requires change. In long-term clinical studies, the discoloration and wear of restorative materials are seen as major problems. The size, concentration, and resin formulation of the filler particles are known factors affecting the wear and discoloration of restorative materials. One of the factors that may affect the quality of the restorations is the consumption of certain beverages, such as coffee, tea, soft drinks, alcoholic beverages, and even fluoridated water. Many studies have shown that liquids consumed because of dietary habits cause a color change in restorative materials and affect surface hardness at different rates. The effect of these beverages on color and microhardness of restorative materials varies depending on the intrinsic features of the restorative material, such as their chemical composition. Although there are many studies on coloration and surface hardness of the restorative materials, there is a limited number of studies regarding the relationship between hardness and color change. The aim of this study is to investigate the effect of frequently consumed beverages on the color stability and microhardness of the restorative materials that are used in dentistry.
The null hypothesis of this study is that staining solutions have no effect on discoloration and microhardness of the restorative materials.
| Materials and Methods|| |
Preparation of samples
In this study, two direct composite resins (Filtek Z250, Filtek Z550); one indirect composite resin (Solidex); and one high viscosity glass ionomer cement (Equia Forte Fil) were used. All the materials used A2 color, and their properties and contents are shown in [Table 1]. For each restorative material, twenty-four disk-shaped specimens (10 mm diameter, 2 mm thickness) were prepared using a cylindrical plastic molds. The restorative materials used in the study were placed in plastic molds as recommended by the manufacturers. After the Equia Forte material was placed in plastic molds, the cellulose acetate strip and a 1 mm thick cement glass were placed on it. Slight pressure was applied to overflow excess material and obtain a smooth surface. After waiting for the time period (2 min), recommended by the manufacturer to complete the chemical polymerization, samples were removed from the molds. A cellulose acetate strip was placed on the other materials, then a 1 mm thick cement glass was placed on the strip, and light pressure was applied. Light-curing materials were polymerized with a light-emitting diode (LED) light device (Woodpecker® Dental Curing Light LED.C, Guilin Woodpecker Medical Instrument CO. LTD., China) on the surface and with the tip of the light device in contact with the glass. During light polymerization of the samples, light intensity was measured at regular intervals with a radiometer (Hilux Dental Curing Light Meter; Dental Benlioglu Inc., Ankara, Turkey). The polymerized samples were removed from the molds, and after the removal of the cellulose acetate strip and the cement glass, additional light was applied for 20 sec to ensure complete polymerization. An indirect composite polymerization unit (Solidilite V, Shofu, Japan) was used in the polymerization of the samples in the Solidex group, according to the manufacturer's recommendations. Samples were polished with polishing discs (Soflex; 3M ESPE, St. Paul, MN, USA). All samples were then kept in an oven at 37°C for 24 h.
Initial color values of all samples were measured using a standard white background (Vita Easyshade, Vita Zahnfabrik, Germany) using the Commission internationale de l'éclairage L*a*b* ( CIELAB) system. Measurements were made under standard lighting conditions D65, and the device was calibrated according to the manufacturer's recommendations before each measurement. Each measurement was repeated three times and the mean L*, a*, and b* values were recorded. After determining the initial color value, samples were stored in four different solutions for 1 week as follows:
- Samples in Group 1 were determined to be the control group, and these samples were stored in distilled water at 37°C.
- Samples in Group 2 were stored in tea at 37°C. For this, two tea bags (2 × 2 g) (Yellow Label Tea, Lipton, London and Turkey) were suspended in 300 ml boiling water by immersion for 10 min.
- Samples in Group 3 were stored at 37°C in coffee. For this purpose, 3.6 g coffee (Nescafe Classic, Nestle, Switzerland) was prepared by dissolving in 300 ml boiled water, mixed for 10 min, and passed through solution filter paper.
- Samples in Group 4 were stored at 37°C in cola (Coca-Cola, The Coca-Cola Co., Istanbul, Turkey).
Samples removed from the solutions after 1 week were washed in distilled water for 5 min and dried on blotting paper. Secondary color measurements were performed with the same spectrophotometer. The following formula was used to calculate the color difference (ΔE) between the two obtained measurements:
ΔE = [(L1* − L0*) 2+ (a1* − a0*) 2+ (b1* − b0*) 2 ] ½
After the restorative materials were removed from the solutions, they were stored for 1 week and the second color measurements were made. The microhardness of the upper surfaces of the materials was measured with a Vickers Microhardness Tester (Shimadzu HMV-M3, Kyoto, Japan). The hardness measurements were taken from the upper surfaces of all samples with a 200 g load and an 11 sec loading time. Three measurements were performed on each sample, and the average of these three measurements was accepted as the surface hardness of the samples.
Color change (ΔE) data and microhardness values were analyzed by the Kruskal–Wallis and Mann–Whitney U test at 0.05 significance level to compare the different groups by loading on the Statistical Package for the Social Sciences (SPSS) 22.0 program.
| Results|| |
[Table 2] shows the differences between the mean and standard deviation (SD) and color deviations of restorative material groups in each solution. The mean Δ Elab values and SDs obtained at the end of this study were determined by measuring at the end of the seventh day. Due to the measurements, the lowest Δ E value in the composite samples group was determined to occur in Group 1, followed by Group 4, and no statistically significant difference was observed between these two groups. The highest Δ E value was obtained in Group 2 and Group 3, and there was no statistically significant difference between these two groups. In the Equia Forte group, the lowest Δ E value was determined in Group 1 while the highest Δ E value was determined in Group 4. When the restorative materials were compared, there was no statistically significant difference between the Z250, Z550, and Solidex groups while the Equia Forte group showed a statistically significant change in color from the other groups [Figure 1].
|Table 2: Color change averages for restorative materials and staining solution ΔE and SD|
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|Figure 1: Average color change values for restorative materials on staining solutions|
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The microhardness values of the restorative materials are shown in [Table 3]. When the hardness values of the materials were listed, the highest hardness value was found in the Z550 group and the lowest hardness value was observed in the samples in the Solidex group. When the effect of different solutions on the restorative materials was evaluated, the highest hardness value in Z250 group was seen in the samples that were stored in coffee, but there was no statistically significant difference in the hardness value with the control group. In the Z550 group, the highest microhardness was seen in the control group, and no statistically significant difference was found between this value and other solutions (P > 0.05). The Solidex group in the tea solution showed that the highest microhardness value was observed to be statistically significant from the other solutions (P < 0.05). In the Equia Forte group, the highest microhardness value was shown in the tea solution, and it was found to have statistically similar results with the measured values from the samples in the control group.
|Table 3: Average microhardness values and SDs of the restorative materials used|
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Compared with the staining media, the highest hardness value was shown in the Z550 group, and the results were statistically similar to Equia Forte in the same medium. The lowest value was observed in the Solidex group, and this value was statistically different from other materials. When the other solutions were observed, the highest hardness value was observed in the Z550 in the cola group while this value had a statistically significant difference from the other materials in the same media. The lowest hardness value was observed in the coffee group Solidex, but this value was statistically different from the other materials in the same media [Figure 2].
|Figure 2: Average microhardness values for restorative materials on staining solutions|
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| Discussion|| |
Color plays an increasingly important role in providing the optimal esthetic dental restorations. The color stability in restorative materials has been reported to be related to the size of the resin matrix, size of the filler particles, depth of polymerization, and type of coloring agents;,, therefore, different restorative materials were used in this study to examine the effects of both monomer structures and filler particle sizes. In the case of detecting the color, there is a very complex phenomenon that includes factors like the light in the environment, light permeability of the material, opacity, reflected light, and color perception by the human eye. Color measurement devices have been developed to minimize these potential errors. In this way, it was possible to calculate Δ Elab values obtained using color parameters in the CIELAB color system and show color differences. To eliminate potential subjective errors in color assessment, the present study used a spectrophotometer for color measurements. Chan et al. reported that most staining occurs within the first week, and stain penetration reached up to 5 μ. Based on the results of this study, the restorative materials used in the study were kept in the solutions for 1 week so that they could be renewed every day. In previous studies, the clinically acceptable color change threshold value was determined as ΔElab ≤ 3.3., According to the results of this study, the ΔE value of all the restorative materials measured in tea, coffee, and cola was found to be above the clinically acceptable level.
The composition and size of the filler particles affect the surface roughness of the restorative materials and, therefore, are related to the external coloration. Thus, it can be expected that nanocomposite with a smaller particle size, will have a smoother surface and will retain less surface stains. In this study, the lowest ΔE value in the Z550 group was thought to be because of the nanohybrid structure. The color change in the microhibrid composite used in the study may have influenced a large number of filler particles. Guler et al. reported that an excess of silane-binding agent and resin amount was a significant difference that increased coloration. Therefore, the excess amount of silane in Z250 can be said to cause more color. The highest ΔE value in the study was seen in the samples of restorative materials of the Equia Forte group. Cattoni et al. reported that when the glass ionomer material was exposed to the aqueous medium, the structure of the material was affected, and the surface of the material was eroded, causing hydrolysis. No study has examined the coloring effect of staining solutions on Equia Forte. However, according to the results, we believe that the Equia Forte group material was degraded and higher values have been observed because of the increase in surface roughness.
Studies show that the coloring of the restorative materials was influenced by beverages containing coloring pigments, such as tea, coffee, cola, red wine, fruit juices, and energy drinks.,, In addition, factors like the type of drink, amount of pigment, and power of hydrogen (pH) value are reported to cause different degrees of coloration. Um and Ruyter stated that the colorants in the coffee were fixed after sticking to the surface and colorants in the tea were removed; therefore, the staining by the coffee was more pronounced. According to Chan et al., two different composite resins were kept in different liquids; at the end of 6-week staining period, they reported that the staining capacity of coffee was higher than that of cola and tea, and no difference was observed between the composite materials. Similar results in other studies show that coffee is a more effective colorant than tea. Mundim et al. stated that despite the phosphoric acid content of the cola, it was not effective in the color change of the composite resins. Due to the study, it was concluded that the coloring of coffee is more pronounced, and the difference between the color changes in the composite samples of cola and distilled water is not significant.
In many studies evaluating the coloring of various restorative materials, it was concluded that composite resins have higher color stability than glass ionomers. The glass ionomer-based restorative material used in the study showed a significant color change compared with the composite groups. Walti et al. evaluated the water absorption and abrasion of composite and glass ionomer cement. Both the composite and the glass ionomer showed that substance was lost because of a chemical dissolution, the roughness value of the composite remained constant, and the roughness value of the glass ionomer cement continued to increase. Iazetti et al. reported that, generally, hydrophobic materials have less color change and have color stability. The high color stability of the composite group has been shown to be more hydrophobic compared with glass ionomers because of the porous structure formed on the surface because of the glass particles in the filler of the glass ionomer-based material. The highest ΔE value in the study was measured in the samples in the cola group for the restorative material of the Equia Forte group. In studies, it has been reported that glass ionomer cement, when stored in acidic environments, releases more fluoride than those stored in neutral or basic media. Continuous exposure to changes in pH may result in ion exchange and significant discoloration. Based on the results, it is believed that because of the low pH value of the cola, cola may cause deterioration of the material surface and, therefore, may have caused more staining.
The concept of surface hardness, which gives information about the structural adjustment of the fill materials, is one of the most important factors affecting the clinical success of restorations. Low hardness values are often associated with low wear resistance and low scratch resistance, which can lead to restoration failures., The hardness measurement tests are carried out in the form of a static diamond tip that has been selected to leave a mark when pressed on a material under a certain load within a certain time. In this study, the Vickers microhardness test was used, which has also been used in many previous studies.,
Due to the effect of the chemical composition and filler content properties of each material on their physical properties, differences are observed between the hardness values. Yap et al. concluded that the changes in the surface hardness of the chemical environment were dependent on the material. Yeşilyurt et al. reported that the hardness values of composite materials can vary greatly in different chemical environments, and this is reported to occur in the first 7 days. Braem et al. and Chung and Greener observed that high hardness values were measured in materials with high filler content. According to the results of this study, the Z550 group restorative material showed a higher surface hardness compared with other materials, and Solidex showed low hardness values compared with other materials. This result can be explained by the filler content of the material. Compared with Z250 and Solidex, Equia Forte has higher hardness values. In a study evaluating the fracture resistance of capsular-shaped restorative materials, Equia Forte was seen as the material with the highest fracture resistance, and it was reported that this value was related to new, ultra-fine, and highly reactive glass particles in the content of the material.
In many studies,, where measurements were made of the microhardness of composite resin materials, different storage media were used. In a study by Yanıkoǧlu et al., a reduction was observed in the surface hardness of various restorative materials after storing in tea, cola, and coffee compared to storing in distilled water. Researchers explained this as a result of the acid effect of the drinks. Similar to our study, in this study, the hardness of the materials stored in coffee and cola were found to be lower than those stored in distilled water.
Therefore, the null hypothesis that different drinks would not have an effect on the color stability and microhardness of restorative materials was rejected.
| Conclusions|| |
- Based on the methodology used and results obtained, it can be concluded thatthe effect of the coloring solution relates to the type of beverage and the composition of the restorative materials.
- While the highest color change among composite resins was observed in tea and coffee, it was observed that cola caused more color change than tea and coffee in high viscosity glass ionomer cement.
- Nanohybrid composite resins are resistant to external coloration and hardness change.
- Different beverages did not significantly affect the surface hardness of restorative materials.
- The values determined in the study reveal the potential for the coloration and microhardness of restorative materials to be affected, but the data obtained should be supported by clinical studies.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]