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Research Article

The Color Stability of Silorane-based Versus Methacrylate-based Composites after Immersion in 100% Orange Juice and Nonalcoholic Beer

Sedighe Sadat HashemiKamangar, Farnoosh Yazdanpanah, Mehrzad Gholampur Dehaky and Mohammad Javad Kharazifard

Correspondence Address :

Sedighe Sadat Hashemi Kamangar
International Campus, School of Dentistry
Operative Department
Tehran University of Medical Sciences
Tehran, Iran
Tel: 02155851151, Fax: 02155851131113
Email: smhk58950@gmail.com

Received on: July 07, 2015, Accepted on: July 20, 2015, Published on: July 24, 2015

Citation: HashemiKamangar SS, Yazdanpanah F, Dehaky MG, Kharazifard MJ (2015). The Color Stability of Silorane-based Versus Methacrylatebased Composites after Immersion in 100% Orange Juice and Nonalcoholic Beer

Copyright: 2015 HashemiKamangar SS, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Abstract
Objective: The aim of the present study was to determine the color stability of a siloranebased composite compared to that of two methacrylate-based composites after immersing in 100% orange juice, nonalcoholic beer, and distilled water, applying spectrophotometric analysis.
Materials and methods: Disc-shaped composite specimens with A2 shade were prepared (15 samples from each composite type). The specimens were divided into three groups of five samples each, and were immersed in 100% orange juice, nonalcoholic beer, and distilled water for 28 days (three hours each day). A spectrophotometer (CIE L *a*b*) was used to assess the color of all specimens before (p<0.05) and after the immersion period. ANOVA and Tukey HSD tests served for statistical analysis.
Results: The composite and beverage types (p<0.001) and their interactions (p<0.001) had significant effects on total color change. After immersing in orange juice, ΔE values were 2.17 +/- 0.65, 3.78 +/- 1.1, and 2.30 +/- 0.58 for Z250, Z350, and P90 respectively. These values were 1.91 +/- 0.7, 2.5 +/- 0.64, and 1.94 +/- 1.39 after immersing in nonalcoholic beer, and 1.49 +/- 0.92, 1.31 +/- 0.44, and 2.95 +/- 1.25 after immersing in distilled water.
Conclusion: The total color changes (ΔE) of microhybrid, nanofilled methacrylatebased and silorane-based composites were less than 3 following exposure to orange juice and nonalcoholic beer, except for those of Z350 after immersing in orange juice.
Fulltext
Keywords: Silorane composite resin, Color, Beverages
Introduction
In recent years, new composites are widely used for restorative treatments of anterior teeth [1] not only due to their improved chemo-physical properties but also because of their esthetic features. Esthetics in dentistry means exact imitation of the natural tooth and one of its determinants is the color. In the long term, the composite color stability could eclipse its clinical success or failure. Poor color matching between the tooth and the composite can even make it necessary to replace a composite restoration [2]. Color instability in composites may result from intrinsic color changes or extrinsic staining [3-6]. Extrinsic staining can be a result of food stain absorption by the composite [6,7]. The extrinsic stains can be eliminated by composite polishing but if the deeper layers of the composite get involved, the color changes may be irreversible [1]. Intrinsic staining, on the other hand, can be related to the resin matrix composition [6,7], the size of the filler particles [1], and their distribution within the resin [1,8]. The silorane-based composite in which the monomer is obtained from the reaction of oxirane and siloxane molecules [9-11] was introduced as an alternative restorative material for methacrylate-based composites. Hydrophobicity and low polymerization shrinkage are two properties of this composite type [9,12,13].
According to the previous studies, the water sorption, solubility, and diffusion coefficient of the silorane-based composite was acceptable [13-15] but contradictory results were obtained as for its superficial features and rate of leakage [16-20]. Many studies have evaluated the effect of various colored beverages on the color stability of methacrylate-based composite [1,21-25], though there has been few studies about the influence of beverages on the color stability of silorane-based composites [26,27]. In addition, most of these studies have assessed the effect of alcoholic drinks, Coca-Cola, tea, or coffee, and beneficial drinks such as orange juice has been rarely investigated [26]. No investigation exists about the effect of nonalcoholic beer, which is a popular drink in Iran, on the color changes of the silorane-based composite. Thus, the aim of the present study was to determine the effect of orange juice and nonalcoholic beer versus distilled water on the color stability of silorane-based composite compared to that of two types of methacrylate based composites with different filler particle sizes (nanofilled and microhybrid).
Materials and Methods
In this experimental investigation, microhybrid methacrylatebased (Filtek Z250; 3M-ESPE, St Paul MN USA), nanofilled methacrylate-based (Filtek Z350 XT Enamel; 3M-ESPE, St Paul MN USA), and silorane-based (Filtek P90; 3M-ESPE, St Paul MN USA) composites were used. The properties of the composites and the beverages are given in Table 1. 
Sample preparation
Stainless steel molds were used to prepare 45 disc-shaped composite specimens (15 specimens from each composite type) with the uniform size of 2 mm in thickness and 10 mm in diameter. The stainless steel mold with a celluloid matrix strip on its lower side was placed on a glass slide and filled by composite. The composite was then covered with another celluloid matrix strip and gently pressed by a glass slide to remove the voids and additional composite. Then, according to the manufacturer's instructions, the composite was cured for 20 seconds at each upper and lower side of the mold using a LED light curing device (Valo, Ulteradent) previously calibrated to 1100 mW/ cm2 by a radiometer.
After removing the glass slides and celluloid matrix strips, the specimens were polished using 1200, 1500, 2000, 2500, 3000, 5000 grit silicon carbide papers respectively. Ultrasonic cleaning of the polished specimens was performed for four minutes in distilled water to remove the debris and keep the samples clean. The samples were then stored in distilled water for 24 hours to complete the polymerization process.
Immersion in beverage solutions
The specimens of each composite types were randomly divided in to three groups of 5 specimens each. The samples of one group served as controls and were stored in distilled water and the samples of the remaining two groups were stored The specimens of each composite types were randomly divided in to three groups of 5 specimens each. The samples of one group served as controls and were stored in distilled water and the samples of the remaining two groups were stored in 100% orange juice and nonalcoholic beer for 28 days. The specimens were kept in dark glass vials containing 10 ml of the mentioned solutions for three hours a day. Each day, after three hours of immersion, the specimens were washed with soft tooth brush under running water and kept in distilled water at room temperature. The distilled water was daily replaced for all groups.
Color change measurement
The colors of all specimens were assessed before and after storage in the given solutions for 28 days using a spectrophotometer according to CIE-L*a*b system. In order to the color measurement, the specimens were placed on a white Leneta paper and a holder plate. The light source was set at an angle of 45˚ with the perpendicular line to the sample surfaces, and a Konica Minolta CS 2000 spectroradiometer was mounted at an angle of approximately 0˚ with the perpendicular line to the sample surfaces and a distance of one meter to the specimens. The device view angle was set at 0.2˚ which provided a circular measuring area with a diameter of three mm on the middle of the samples.
The experiment was performed under the environmental conditions of the lab at approximately 20 degree C and the color coordinates were calculated under D65/2˚ standard CIE observer by CS-S10W software. In this system "L*" represents the brightness axis, "a*" represents the red-green spectrum, and "b*" indicates the blue-yellow spectrum.
The total color changes of the specimens were calculated using the following equation:
ΔE=[(L1* -L0*)2+(a1* - a0*)2+(b1* -b0*)2]1/2
Statistical analysis
The version 18 of Statistical Package for Social Sciences (SPSS) software was used for the statistical analysis. Repeated measures ANOVA was used to assess the effects of the composite and beverage types and their interactions on different color parameters and total color changes. In cases where the results of two-way ANOVA test showed statistically significant difference, Tukey-HSD test was used to statistically analyze the differences between pairs of groups. Significance level was set at p<0.05.
Results
Different color parameter changes are given in Table 2.
The L* color parameter (ΔL*): The average numerical values of L* before and after immersion in the respective solutions are given in Figure 1. The effects of the composite and the beverage types were statistically significant (P<0.001), but their interaction did not significantly influence the L* changes (P=0.349). Statistically significant differences existed between Z350 and P90 groups (p<0.001), Z250 and P90 groups (P<0.001), and Z350 and Z250 groups (P=0.017). Among the different beverage groups, statistically significant differences existed between the orange juice and nonalcoholic beer groups (P<0.001), and the nonalcoholic beer and distilled water groups (P<0.001), but no statistically difference was observed between the orange juice and distilled water groups (P=0.288).
The α* color parameter (Δa*) : The mean numerical values of α* before and after immersion in the solutions are given in Figure 2. The composite and beverage types, and also their interactions had statistically significant effects (P<0.001) on α* changes. As for P90 composite, no statistically significant difference existed between orange juice and distilled water (P=0.61), orange juice and nonalcoholic beer (P=0.66), and nonalcoholic beer and distilled water (P=0.17). In Z250 composite, orange juice and distilled water showed no statistically significant difference (P=0.06), but significant differences were found between orange juice and nonalcoholic beer (P<0.001), and nonalcoholic beer and distilled water (P=0.003).
Z350 composite revealed significant differences between orange juice and distilled water (P<0.001), orange juice and nonalcoholic beer (P<0.001), and nonalcoholic beer and distilled water (P<0.001).
As for orange juice, significant differences were detected between Z350 and Z250 (P=0.012), and P90 and Z250 (P<0.001), but no significant difference existed between P90 and Z350 (P=0.24).
After immersion in nonalcoholic beer, no significant difference was observed between Z250 and Z350 composites (p=0.83), but statistically significant differences were revealed between P90 and Z350 (P<0.001), and P90 and Z250 (P<0.001). Following immersion in distilled water, significant differences were detected between P90 and Z350 (P<0.001), and P90 and Z250 (P<0.001), in contrast, insignificant difference existed between Z250 and Z350 (P=0.49).
The b* color parameter (Δb*): Figure 3 shows the mean numerical values of b* before and after storage in different solutions. The types of the composite and the beverage and their interactions showed statistically significant effects (P<0.001) on b* changes. In P90 composite there were no significant difference between orange juice and distilled water (P=0.87), orange juice and nonalcoholic beer (P=0.30), and nonalcoholic beer and distilled water (P=0.58). As for Z250 composite, no significant differences were observed between orange juice and nonalcoholic beer (P=0.30), and nonalcoholic beer and distilled water (P=0.53), but significant difference existed between orange juice and distilled water (P=0.36). As for Z350 composite, there were statistically significant difference between orange juice and distilled water (P<0.001), and orange juice and nonalcoholic beer (P=0.001), but nonalcoholic beer and distilled water showed no significant difference (P=0.095).
After immersing in orange juice, there were significant differences between Z350 and Z250 (P<0.001), and P90 and Z350 (P<0.001), but no significant difference was detected between P90 and Z250 (P=0.48).
As for nonalcoholic beer, no significant differences were observed between Z350 and Z250 (P=0.99), P90 and Z350 (P=0.47), and P90 and Z250 (P=0.50). Following storage in distilled water, there were no significant differences between Z350 and Z250 (P=0.85), P90 and Z350 (P=0.28), and P90 and Z250 (P=0.58).
The total color parameter (ΔE): The composite and beverage types and their interactions showed significant effects (P<0.001) on total color changes. In P90 composite a statistically significant difference was observed between nonalcoholic beer and distilled water (P=0.049). In contrast, there was no significant difference between orange juice and nonalcoholic beer (P=0.66), and orange juice and distilled water (P=0.26). Z250 composite showed significant difference between orange juice and distilled water
(P=0.047), and no significant difference between orange juice and nonalcoholic beer (P=0.62), and distilled water and nonalcoholic
beer (P=0.28). As for Z350 composite, there were statistically significant differences between orange juice and distilled water (P<0.001), orange juice and nonalcoholic beer (P<0.001), and nonalcoholic beer and distilled water (P<0.001).
After immersing in orange juice, there was no significant difference between Z250 and P90 (P=0.91), but significant differences were observed between P90 and Z350 (P<0.001), and Z350 and Z250 (P<0.001).
Following storage in nonalcoholic beer, no significant difference was observed between P90 and Z250 (P=0.99), P90 and Z350 (P=0.26), and two methacrylate-based composites (P=0.23). After immersing in distilled water, no significant difference was detected between Z250 and Z350 (P=0.85), but significant differences existed between P90 and Z350 (P<0.001), and P90 and Z250 (P<0.001).
Discussion
The results of the present study indicated that following immersion in all beverages, the total color change (ΔE) was found to be less than 3.3 which might be in non-visible range [28] for all composite types except for that of Z350 in orange juice. Color change in composite is related to chemical type/structure of the monomers, the quality of the polymer, the type/quantity of filler particles, the chemical activator, and water/heat sorption [29]. The main factors of the color change may be oxidation of the superficial pigments, oxidation of amine compounds, which are responsible for color stability of resin composites [30], or the micro-cracks on the composite surface [31]. The micro-cracks are related to the filler particle components of composite resins [32] and can be the reasons of the present or future color changes, and destruction of the external surface of a composite restoration [32].
In a study, Arocha et al. [26] compared the color stability of a silorane-based composite with Z530, Tetric Evoceram, Venus Diamond, and Grandio following immersion in tea, coffee, red wine, orange juice, Coca Cola, and distilled water. They demonstrated that the silorane-based composite had the highest color stability and red wine caused the highest color change (ΔE). The results of this study were in line with our study as for the silorane-based composite following immersion in orange juice.
Barutcigil et al. [27] evaluated the effect of Coca-Cola, coffee, tea, and red wine on color change of a silorane-based composite compared to that of four types of methacrylate-based composites and showed that staining was occurred in all composite types.
These results were in contrast to the results of the present study. In that study, immersion was performed 24 hours a day for one month while in the present study, it was performed for three hours a day. In that study [27] the silorane-based composite got gradually lighter after immersion in distilled water which was in line with the present study.
In our study, according to Figures 2 and 3, a* and b* values increased (in + direction) after immersion of the siloranebased composite in all beverage types, which indicated that this composite became more chromatic [33]. However, according to Figure 1, L* values increased (in + direction) which showed that the silorane-based composite got lighter. The total color change of the silorane-based composite was invisible and it got even lighter after storage in distilled water.
Hydrophilic properties and water sorption rate of the resin matrix can influence the composite tonality [27]. If a resin composite is able to absorb the water, it can absorb other liquids and accept the staining process [7,27]. Water sorption is mostly due to direct absorption in the resin matrix and glass filler particles can absorb water to the surface of the composite not into the bulk of it [27]. Water sorption can reduce the composite lifetime through expanding, resin component plasticizing, silane hydrolysis, and micro-crack formation [27]. The micro-cracks or the interfacial gaps at the interface between the filler and the matrix allow stain penetration and cause the color change [34].
It has been demonstrated that the hydrophilic materials which show more water sorption, could be highly affected by dye solutions as compared to the hydrophobic materials [35]. Color changes occurred after immersing the composite in orange juice and nonalcoholic beer could be related to extrinsic discoloration and those occurred following immersion in distilled water could
be results of intrinsic discoloration [27]. The predominating organic acid in orange juice is citric acid and nonalcoholic beer contains ascorbic acid and citric acid. Citric acid is a weak organic acid which can be found in citrus fruit. It is a carboxylic acid with three COOH agents and a structural formula of C5H6O7. In the present study, pH of orange juice and nonalcoholic beer were determined to be 3.7 and 3.3 respectively. pH is an important factor in destructive effects of each acidic solution, however, this effect was not observed in the present study, which could be a result of the limited period of immersion. Orange juice caused a visible color change in Z350 which could be due to penetration of its yellow pigments into the composite superficial microcracks.
In this regard, b* value significantly increased in Z350 composite after immersing in orange juice (Figure 3). Filtek Z350 is a nanofilled composite contains silica nanoparticles with the size of 20 nm and zirconia-silica nanoclasters with the size of 0.4-0.6 m [36]. Although some studies demonstrated that Z350 has mechanical properties similar to those of hybrid and midifilled composites [37,38], the high surface/ volume ratio due to the presence of silica particles may increase its water sorption and lead to the destruction of polymer matrix-filler interface [39]. This could deteriorate some of its mechanical properties [40] and develop micro-cracks which finally increase color changes. Real color acceptability in oral cavity requires a longer period of time since exposure to colored beverages is inconstant, the saliva dilutes dye solutions, and the restoration surfaces are cleaned up while brushing. Many other internal and external factors influence composite color change such as the polymerization rate, water sorption, the nutrition, oral hygiene status, and restoration surface smoothness [27], which necessitates more investigations on this issue.
Conclusion
In total, the color change (ΔE) of nanofilled, microhybridmethacrylate based and the silorane-based composite were less than 3  which might be clinically in nonvisible range following exposure to orange juice and nonalcoholic beer except for that of Z350 after immersion in orange juice.
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Tables & Figures

Figure 1: The mean error bar and 95% confidence interval on the mean of L* before and after immersing the composite in different beverages


Figure 2: The mean error bar and 95% confidence interval on the mean of b* before and after immersing the composites in different beverages


Figure 3: The mean error bar and 95% confidence interval on the mean of a* before and after immersing the composites in different beverages


Table 1: Materials and their compositions used in the study


Table 2: Central distribution indicators of color changes before and after composite exposure to various beverages
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