ORIGINAL RESEARCH

https://doi.org/10.5005/jp-journals-10019-1412
International Journal of Prosthodontics and Restorative Dentistry
Volume 13 | Issue 2 | Year 2023

Evaluation of Color Stability of Omnichroma, Beautifil-Bulk Restorative, and G-aenial Composites When Exposed to Various Beverages: An In Vitro Study

Samreena Kalander¹, Aravind R Kudva², Prathap M S³ https://orcid.org/0000-0002-2647-9553, Vivian F D’Costa⁴ https://orcid.org/0000-0002-8103-3925, Aboobacker Sidheeque⁵

^1-5Department of Conservative Dentistry & Endodontics, Yenepoya Dental College, Yenepoya University (Deemed to be University), Mangaluru, Karnataka, India

Corresponding Author: Samreena Kalander, Department of Conservative Dentistry & Endodontics, Yenepoya Dental College, Mangaluru, Karnataka, India, Phone: +91 9880899018, e-mail: samreena261@gmail.com

Received on: 27 May 2023; Accepted on: 18 June 2023; Published on: 28 June 2023

ABSTRACT

Purpose: The purpose of this in vitro study was to evaluate the respective color stability of modern composite resins designed for esthetic restorations when continuously exposed to various beverages.

Material and methods: A total of 60 disk-shaped specimens made out of three composite materials (Omnichroma, Beautifil-Bulk restorative, and G-aenial) were used. A total of 20 specimens measuring 10 mm in diameter and 1 mm in thickness were made from each composite resin. After dry storage at 37°C for 24 hours in an incubator, the initial color was assessed by a calibrated spectrophotometer. Test specimens were immersed in four staining solutions, and the control group was dry-stored. All specimens were kept in an incubator at 37°C for 28 days. After 28 days, spectrophotometric measurements were again performed to determine the color changes. One-way analysis of variance (ANOVA) was used for the comparison of each beverage among the three groups to find the significant difference.

Results: Omnichroma material exhibited less color change as compared to Beautifil-Bulk restorative and G-aenial composites. The highest color change measured against a white background was observed for Beautifil-Bulk in coffee (p = 0.001), while the least staining was observed for Omnichroma in tea (p = 0.003). The highest color change measured against a black background was observed for Beautifil-Bulk in coffee (p = 0.001), while the least staining was observed for G-aenial in coffee (p = 0.001).

Conclusion: All three types of composites displayed color changes after immersion in tea, coffee, orange juice, and cola. Omnichroma showed higher color stability than Beautifil-Bulk restorative and G-aenial.

How to cite this article: Kalander S, Kudva AR, S PM, et al. Evaluation of Color Stability of Omnichroma, Beautifil-Bulk Restorative, and G-aenial Composites When Exposed to Various Beverages: An In Vitro Study. Int J Prosthodont Restor Dent 2023;13(2):88-93.

Source of support: Nil

Conflict of interest: None

Keywords: Color stability, Composite resins, Omnichroma, Spectrophotometer, Staining

INTRODUCTION

Composite resins mimic tooth color, implying they are the restorative material of choice due to their physical and mechanical properties and exemplary cosmetic features.¹ In recent years, the adoption of ceramic veneers and crowns has been diminishing due to the ability of composite resins to simulate the appearance of natural teeth.²^,³

Discoloration is one of the widely accepted esthetic concerns with regard to resin composites.⁴ A pivotal optical characteristic to take into contemplation while executing an esthetic restoration is color stability.⁵ Optical characteristics of each individual layer combine to create the final color of the restoration; the observer’s eye, environment, dental restorations, and nearby tooth anatomy all impact how the color is perceived.⁶ Several factors contribute to the discoloration of composites, such as the framework/composition of the composite resin, the character of the fillers, the degree of polymerization, and other inherent elements.⁷^,⁸

Even though composite resins’ composition and properties have improved substantially, they still face a variety of challenging conditions when used in the oral cavity, including pH fluctuations and temperature variations.⁹ Consumption of coffee and tea in adults and frequency of aerated beverages in young people and children may have an impact on the cosmetic and elemental nature of composite resins, which in turn could abate the nature of the restoration.¹⁰ The discoloration of composites in the oral atmosphere could be due to exterior degradation or a slight seepage of staining factors.¹¹

The disadvantages of the layering technique in the clinical application of conventional composites resulted in the voids and/or contaminations between the composite layers and the failure of interlayer bonding, which successively has led to the evolution of bulk-fill resin-based composites.¹² The prepolymerized fillers in the microfilled hybrid composite (made by polymerizing a resin matrix that contains microfiller particles) provide good esthetics and clinically advantageous radiopacity.¹³

The Commission Internationale de L’Eclairage (CIE) color model and the L*a*b* system was used in spectroscopic analysis to evaluate color variation.¹⁴ The Munsell color scheme and the standard CIE (L*a*b*) color system are typically used to evaluate chromatic variations.¹⁵ A dental material that more nearly resembles the color of the neighboring healthy tooth has been developed as Omnichroma resin composite containing 260 nm silica and zirconia fillers.¹⁶

Though study on restorative materials has been an ongoing process for years, adhesive and new restorative composites still need to have their discoloration process/ability researched further. Additionally, the relationship between the color stability of modern composite resins has received inadequate attention. The purpose of the current in vitro research was to evaluate the staining susceptibility of recent composite resin (Omnichroma, Beautifil-Bulk Restorative, and G-aenial) when submitted to Tea, Coffee, Cola, and orange juice which are prevalent in routine diet. The null hypothesis projected that composite resins, when immersed in various beverages, do not change color.

MATERIALS AND METHODS

This in vitro study was directed in the Department of Conservative Dentistry and Endodontics, Yenepoya Dental College, Manguluru, Karnataka, India, and the Department of Media Technology, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, Karnataka, India, for spectrophotometer analysis. Ethical approval for this in vitro study (protocol no: YEC2/581) was provided by the Yenepoya Ethics Committee 2 (Yenepoya Deemed to be University).

The sample size for the current research was estimated using G*power software. At a 1% level of significance and 80% power by considering the effect size 0.51 from pooled standard deviation (SD) 1.1 (from a related article).²

Specimen Preparation

A total of 60 disk-shaped specimens calibrating 10 mm in diameter and 1 mm in thickness were prepared from three different resin composites (n = 20 each). The specimens were grouped as follows;

Group I: Omnichroma (Tokuyama, Dental Corp, Tokyo, Japan) (Fig. 1A)
Group II: Beautifil-Bulk Restorative (Shofu, Kyoto, Japan) (Fig. 1B)
Group III: G-aenial (GC Corp, Tokyo, Japan) (Fig. 1C)
The composites were placed into preformed wells, and a glass slab was lodged on top to discard surplus material in order to attain a plane/smooth surface (Fig. 2A). Following this, the composites were light cured at a distance of 1 mm for 20 seconds employing a light emitting diode curing equipment (Ivoclar, Vivadent, Glattpark, Switzerland) (Fig. 2B).⁶

Figs 1A to C: Composite materials used; (A) Omnichroma; (B) Beautifil- Bulk; (C) G-aenial

Figs 2A and B: (A) Placement of sample in preformed wells; (B) Curing of composites

The original color of individual specimens was assessed using a spectrophotometer (X-rite i1 Pro 2, X-rite, Grand Rapids, Michigan, United States of America) and the analysis of individual specimens was recorded against both white and black backgrounds (Fig. 3). After recording the preliminary color values of the samples; specimens were stocked in an incubator for 24 hours at 37°C.²

Figs 3A and B: Spectrophotometer X-rite i1 Pro 2; (A) Specimens measured against a white background; (B) Specimens measured against a black background

Immersion of Specimen in Beverages

To examine the color variations in various beverages, the specimens of each composite resin were individually immersed (n = 4 each) in tea, coffee, cola, and orange juice. Each group had a control (n = 4) in which the specimen was stored in a dry environment for 4 weeks (Fig. 4). All specimens were stocked in an incubator at 37°C for 28 days, following which the staining agents were replaced every week to avoid bacteria or yeast contagion. After 28 days of storage, samples were taken off from staining agents, rinsed for 60 seconds with hot water and consequently air dried (Fig. 5). Spectrophotometer measurements were repeated for individual samples in order to determine color variations.²

Fig. 4: Specimens immersed in their respective mediums (group I) Omnichroma; (group II) Beautifil-Bulk; (group III) G-aenial

Figs 5A to C: Posttreated specimens (after 28 days) in storage solutions; (A) Omnichroma; (B) Beautifil-Bulk; (C) G-aenial

Color Evaluation

The color of the restoration was measured using a spectrophotometer with a CIE L*a*b system. Individual samples were placed on the measuring head of the spectrophotometer and capped with a black cover. Prior to each measurement session, the spectrophotometer was calibrated according to the manufacturer’s recommendations adopting the supplied white calibration standard. The spectrophotometer is programmed to compute the mean color measurement of 20 specimens of each material.

Color values were expressed in the CIEL*a*b* color system, L* for lightness from white (L*= 100) to black (L*= 0), a* for green (−a*) and red (+a*), and b* for blue (−b*) and yellow (+b*) color components. Color variations ∆E between baseline and after storage measurements were computed employing the following formulae⁶:

Statistical Analysis

Individually obtained data were compiled and analyzed using Statistical Package for the Social Sciences (SPSS) (IBM Corp. Released 2020. IBM SPSS Statistics for Windows, Version 27.0. Armonk, New York, United States of America: IBM Corp). The level of significance was fixed at p < 0.05. One-way analysis of variance (ANOVA) was adopted for correlating the findings of each beverage among three groups in order to find the significant difference.

RESULTS

The mean color variation for each composite against different beverages against white background was presented in Table 1. There was a substantial difference in color variations of different composite resins with tea (p = 0.003) and coffee (p = 0.001), while cola (p = 0.106), orange juice (p = 0.33), and control group (p = 0.81) showed an insignificant difference. The maximum color variation measured against a white background was noticed for Beautifil-Bulk in coffee (15 ± 1.01), while the least staining was detected for Omnichroma in tea (1.03 ± 0.426).

**Table 1:** One-way ANOVA for comparison of color changes with beverages in different groups against a white background
Beverages	Mean ± SD			p-value
Beverages	Omnichroma	Beautifil-Bulk restorative	G-aenial	p-value
Tea	1.03 ± 0.426	11.275 ± 2.599	7.45 ± 3.584	0.003*
Coffee	5.6 ± 1.644	15 ± 1.0124	6.125 ± 3.028	0.001*
Cola	1.15 ± 0.217	4.875 ± 1.239	3.05 ± 3.036	0.106
Orange juice	2.1 ± 1.212	4.875 ± 1.239	3.85 ± 3.036	0.33
Control	1.4 ± 0.324	1.35 ± 1.445	1.875 ± 1.194	0.81

*p < 0.05 is considered significant

The mean color transition for individual composite against different beverages against a black background was presented in Table 2. There was a substantial difference in color changes of different composite resins with tea (p = 0.001), coffee (p = 0.001), and control group (p = 0.010), while cola (p = 0.79) and orange juice (p = 0.32) showed an insignificant difference. The maximum color variation measured against a black background was noticed for Beautifil-Bulk in coffee (22.92 ± 0.99), while the least staining was detected for G-aenial in coffee (3.57 ± 2.52).

**Table 2:** One-way ANOVA for comparison of color changes with beverages in different groups against a black background
Beverages	Mean ± SD			p-value
Beverages	Omnichroma	Beautifil-Bulk restorative	G-aenial	p-value
Tea	7.3 ± 0.886	19.825 ± 2.147	11.75 ± 3.586	0.001*
Coffee	5.375 ± 1.508	22.925 ± 0.994	3.575 ± 2.529	0.001*
Cola	8.925 ± 1.342	9.85 ± 2.865	10.45 ± 3.591	0.79
Orange juice	9.607 ± 1.481	9.725 ± 1.293	6.825 ± 3.895	0.32
Control	3.575 ± 1.296	0.8 ± 0.308	4.15 ± 1.523	0.010*

*p < 0.05 is considered significant

DISCUSSION

Growing esthetic needs and the rapid development of new restorative materials has produced an extensive surge in the incorporation of resin composites in routine dental practice.¹ The primary speculation for the replacement of dental cosmetic restorations in the esthetic zone is discoloration. The contributing factor towards the replacement of composite resins is their color instability.¹⁷ According to Satou et al.,¹⁸ the most likely sites for the stain to penetrate are the microcracks and microvoids at the filler-matrix interphase.

The degree of discoloration from external agents differs according to oral health, eating and/or drinking pattern, and habits like smoking.¹⁹ In this study, it was attempted to mimic a condition that is still clinically applicable. So, it was determined not to polish the specimens but rather stain the external surface of the composite. This is an effort to mimic the most extreme clinical scenario in which the composites are polymerized against a mylar strip imbibing a plush resin matrix, as it can happen particularly in the proximal aspects of the teeth.² Tea, coffee, cola, and orange juice were utilized as staining solutions in this study based on the various types of beverages consumed by adults and younger generations. As these elements are frequently found in modern diets, and some are recognized to possess the potential to stain tooth-colored restorations.¹⁷

The control group used in this investigation was dry storage. Postpolymerization could be the mainstay of all the composites in the control group exhibiting minor color variations.²⁰ The decision to choose a 28-day immersion period was in accordance with two previous elaborative pieces of research, which indicated that a 30-days immersion period was the maximum that could be adopted.¹⁷^,²¹ This is consistent with Ertas et al.¹¹ assessment that 28 days is equivalent to approximately 2 years and 6 months of clinical ageing (24 hours in vitro staining complies with approximately 1 month in vivo).

It has been stated that there could be ambiguity in visual color assessment due to interobserver differences towards the perception of color. Discoloration can be assessed using instrumental or visual methods.²² Spectrophotometry, colorimetry, and digital image analysis are instrumental methods for measuring color; spectrophotometry is proclaimed to be a decisive method for evaluating dental materials. Hence spectrophotometer was employed in this study.²³ The CIE L*a*b* color system, which was adopted pertaining to this research, is a recommended technique for dental applications that illustrates color based on individual perception. L*, a*, and b* are the three spatial coordinates used to specify color, where L* displays the shade luminosity (value), and a* and b* display the measure of red-green color and yellow-blue color, respectively.¹⁷

In accordance with previous study, spectrophotometer analysis was adopted to avoid any bias due to an individual’s visual examination and to permit a double assessment over white and black backgrounds, respectively. This double assessment can simulate two different clinical scenarios, that is, the black background (where no tooth structure prevails on the backside) mimicking class IV composite restorations and the white background (prevalence of one or more walls) mimicking classes I, II, III, and veneers. Therefore, it became conclusive to execute these readings against backgrounds of black and white, respectively.³

Color variations that were higher than the control group have been demonstrated with all staining solutions. Consequently, the null hypothesis that composite resins are not changing color after immersion in various beverages has been rejected. Among the three composites used in this study, Omnichroma expressed the least color change, and Beautifil-Bulk Restorative displayed the highest color variation. The composition of Omnichroma has urethane di methacrylate (UDMA), proving that UDMA is more stain-resistant compared to bisphenol A-glycidyl methacrylate (bis-GMA) owing to its meager water solubility and absorption.¹¹ The conclusive data may be attributed to the incorporation of nanoparticles that conform and blend to the surrounding tooth structure (bringing about a chameleon effect) and its wavelength being lesser than that of visible light.²⁴ The presence of bis-GMA in the resin matrix of Beautifil-Bulk draws our attention to it exhibiting greater discolorations than other materials.²⁰

This study displayed that all tested composites exhibited discoloration after a 28-day period of immersion in all tested beverages. The immersion time was directly proportional to the color change; that is, an increase in immersion time intensified the color intensity, which was in coherence with previous literature too.¹⁸ With the passage of time, aqueous environments can meddle with the properties of composite resins, thereby compelling hydrolytic degradation.²⁵ Daily consumption of coffee has been proven to have a strong staining affinity towards teeth and composite restorations.²⁶ In the present research, too, coffee generated drastic discolorations among all the tested beverages, attributed to the fact that the ingestion of polar yellow colorants in coffee into the organic phase of composite resins may be liable for these severe color variations.²⁶ According to the study done by Um and Ruyter,²⁷ the coloring agents in the coffee were hooked onto the external surface in comparison to tea, consequently pronouncing the staining effects of coffee. According to Ozkanoglu and Akin,²⁸ composites immersed in coffee exhibited higher staining than those in tea or cola; over a 6-week staining period and no difference was perceived between the composite materials.

This study has limitations, such as it’s an in vitro study and lacks proper simulation of the oral cavity, although the quest for ideal esthetic and functional restoratives culminated in significant progress and developments in restorative materials and techniques over time. Further, more trials that are clinical are required to confirm the data obtained from this laboratory study and to evaluate the new composite resin materials under various clinical situations.

CONCLUSION

Within the limitations of the study, it can be concluded that, all three types of composites displayed color changes after immersion in different beverages. Omnichroma exhibited higher color stability in comparison to BeautifIl-Bulk and G-aenial composites. The circumstantial evidence gathered from the present study provides clinicians with information pertaining to individuals’ dietary habits and the staining susceptibility of restorative materials. The longevity of maintaining the color of esthetic restorations within the oral cavity may be enhanced either by incorporating dietary restrictions or by carefully choosing a compatible restorative material that correlates with one’s dietary lifestyle.

ORCID

Prathap M S https://orcid.org/0000-0002-2647-9553

Vivian F D’Costa https://orcid.org/0000-0002-8103-3925

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