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Journal of Indian Society of Pedodontics and Preventive Dentistry Official publication of Indian Society of Pedodontics and Preventive Dentistry
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Year : 2021  |  Volume : 39  |  Issue : 3  |  Page : 262-266

Effect of a wear-resistant resin coat on the color stability of a resin-modified glass ionomer restorative material

Department of Pediatric Dentistry, Rutgers School of Dental Medicine, Newark, New Jersey, USA

Date of Submission08-Sep-2020
Date of Decision10-Dec-2020
Date of Acceptance03-Mar-2021
Date of Web Publication22-Nov-2021

Correspondence Address:
Dr. Madhu Mohan
Department of Pediatric Dentistry, Rutgers School of Dental Medicine, 110 Bergen Steet, Newark, New Jersey 07101
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jisppd.jisppd_387_20

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Aim: The purpose of this in vitro study was to evaluate the effect of the Equia Forte Coat on the color stability of Equia Forte Fil. Materials and Methods: Sixty discs of Equia Forte Fil were randomly divided into two groups. One group of 30 samples was treated with Equia Forte Coat according to the manufacturer's directions. The other 30 discs were not coated. All discs were continuously soaked in cola for 7 consecutive days. The color changes in the Equia Forte Fil samples were determined using a colorimeter. The color difference (△E) was calculated using the Commission Internationale de l'Eclairage L*a*b* coordinates. Results: There was a significant difference in ΔE between the two groups (P < 0.0001). The group with Equia Forte Coat had significantly less color change than the group without the Equia Forte Coat. Conclusion: The application of the Equia Forte Coat significantly improved the color stability of Equia Forte Fil.

Keywords: Colorimetry, resin coat, resin-modified glass ionomer

How to cite this article:
Mohan M, Aljohani Y, Rosivack R G. Effect of a wear-resistant resin coat on the color stability of a resin-modified glass ionomer restorative material. J Indian Soc Pedod Prev Dent 2021;39:262-6

How to cite this URL:
Mohan M, Aljohani Y, Rosivack R G. Effect of a wear-resistant resin coat on the color stability of a resin-modified glass ionomer restorative material. J Indian Soc Pedod Prev Dent [serial online] 2021 [cited 2023 Feb 4];39:262-6. Available from: http://www.jisppd.com/text.asp?2021/39/3/262/330709

   Introduction Top

Dental caries is the most common chronic disease of childhood with a prevalence almost five times that of asthma.[1],[2],[3] Early childhood caries (ECC) is a condition defined by the American Academy of Pediatric Dentistry (AAPD) as the presence of one or more decayed (noncavitated or cavitated), missing (as a result of caries), or filled tooth surfaces in any primary tooth in a child 71 months of age or younger.[4] ECC can be painful, debilitating, and significantly increases the likelihood of poor child growth, development, and social outcomes. ECC may also result in a substantial social burden on families and significant costs to the public health system.[5],[6],[7],[8]

There are multiple esthetic restorative materials available to pediatric dentists to restore caries lesions. Options for restoration include glass ionomer cements (GICs), resin-modified GICs (RMGICs), polyacid-modified resin composites (compomers), and composite resins (CRs). Scientific evidence and clinical judgment is needed to determine which material to use depending on the patient's needs and clinical situation. Recently, there has been significant improvement in the technology related to RMGICs. RMGICs contain some of the same components as conventional GICs giving them the benefit of long-term adhesion and fluoride release as well as the advantages of resin in terms of improved strength and esthetics.[9],[10],[11],[12],[13],[14]

In pediatric patients, the dentist must provide quality treatment while managing the patient's experience within the constraints of available restorative options. RMGICs can be ideal for certain indications such as atraumatic restorative treatment which provides a minimally invasive procedure and esthetic results.[15],[16],[17],[18]

Color stability is essential in the selection of an esthetic restoration to mimic the appearance of natural tooth structure. Color stability is affected by intrinsic factors such as the filler particles and resin matrix, and extrinsic factors such as absorption of stains, diet, oral hygiene, and surface smoothness of the restoration.[19],[20],[21] Previous studies have also found that certain shades of RMGICs are more susceptible to staining than others. One study found that the darker C shades of the composite were more susceptible to stain than the lighter composite shades.[26]

Recently, Equia Forte Coat (GC America Inc., IL, USA), a light-cured, self-adhesive wear-resistant resin coat has been introduced. The material is reported to provide higher wear resistance and improve the surface hardness of Equia Forte Fil.[22]

Many studies have evaluated the effects of beverages on the color stability of restorative materials;[21],[23],[24],[25],[26],[27],[28],[29],[30],[31],[32],[33] however, the effects of a resin coat on the color stability of RMGICs have not been reported. This study assessed the role of a resin coat on the color stability of a RMGIC.

Previous studies have evaluated the effect of various staining solutions on restorative materials.[31] It has been established that cola, a beverage consumed by children, stains pediatric restorative materials and that RMGICs are less stain resistant than other pediatric restorative materials.[26] Since there are advantages to using RMGICs (fluoride release and chemical bonding to tooth structure), it would be beneficial to find a method to enhance their color stability.

The effect of Equia Forte Coat on the color stability of Equia Forte Fil has not been thoroughly investigated. Therefore, the current study assessed the effect of the Equia Forte Coat on the color stability of Equia Forte Fil when stained with cola.

   Materials and Methods Top

In this in vitro study, 60 disc-shaped specimens measuring 6.35 mm (1/4 inch) in diameter and 1.5 mm in thickness were fabricated of EQUIA Forte Fil shade B1 (GC America Inc., IL, USA). Shade B1 was used as it is one of the most prevalent shades used in pediatric dentistry.

For the fabrication of the specimens, a flat metal EverBilt washer, distributed by Home Depot (Atlanta, GA, USA) was used as a mold. It was placed on a glass slab. The washer was filled with Equia Forte Fil following the manufacturer's instructions and a Mylar strip was placed over it and excess material was removed.

The material was cured for 40 s with an Elipar™ DeepCure-S LED Curing Light (3M/ESPE, St. Paul, MN, USA) that has a wavelength range of 430–480 nm in an effort to hasten the setting time. The curing light was calibrated using the light intensity meter of the Elipar™ DeepCure-S LED Curing Light charging station to ensure a consistent cure throughout the fabrication process. The material was then allowed to set for 15 min before removal from the mold. Next, the specimens were randomly divided into two groups. For the first group of 30 discs, the specimens were finished and polished with a fine diamond bur as per the manufacturer's instructions. Then Equia Forte Coat was applied following the manufacturer's instructions and cured with the same curing light for an additional 20 s. As for the second group of 30 discs, the specimens were not finished or polished and were not coated with any material.

Both groups were then stored in distilled water at room temperature for 24 h. Next, an initial color reading was performed for all 60 discs. Both groups were then stored in a cola-based beverage for seven consecutive days (Coca-Cola, Coca-Cola Company, Atlanta, GA, USA) The ingredients in Coca-Cola are high fructose corn syrup, caramel color, phosphoric acid, natural flavors, caffeine. The samples were stored for 7 days at standardized conditions of 37°C in plastic ice cube trays. The ice cube trays were wrapped with a nylon wrap cover to prevent evaporation of the staining solution that could lead to changes in volumes of the beverage.

After 7 days, the specimens were gently washed with distilled water for 5 min and dried with tissue paper and a second color measurement was recorded using the colorimeter.

The color was measured using a colorimeter, model CS-10 (Hangzhou CHNSpec Technology Co., Ltd, Hangzhou City China). This color reader has a probe testing port diameter of 38 mm that facilitates color measurement in small samples. The colorimeter was calibrated as per the manufacturer's instructions once it was turned on. The calibration was performed using a white standard and a black standard (supplied with the instrument) with known color dimensions. The colorimeter was placed flush on all the samples during measurement. The specimens were kept against a white background during all measurements. This ensured that the reader was used with a consistent background for each specimen and prevented variability due to absorption or any other confounding color effects.


Color difference (△E) was evaluated using the Commission Internationale de l'Eclairage (CIE) L * a*b* coordinates. In the CIE-Lab system, all colors in nature are obtained from the mixture of three basic colors: red, blue, and green. L* indicates lightness, a* is the red/green coordinate, and b* is the yellow/blue coordinate. The CIE-LAB system determines color in a three-dimensional space. The following formula was used to calculate △ E for each sample:

△E* = (△L*2 + △a*2 + △b*2)½

The mean ΔE and standard deviation for each group was calculated and is shown in [Figure 1].
Figure 1: Color change with and without resin coat

Click here to view

An independent sample t-test was used to determine if there was a statistically significant difference in ΔE between Group 1 (Equia Forte Fil with Equia Forte Coat) and Group 2 (Equia Forte Fil).[35] IBM SPSS Statistics Version 26 Armonk, NY was used for the data analysis. The significance level was set to P ≤ 0.05 (two-sided).

There was a statistically significant difference in ΔE between group 1 and group 2 (P < 0.0001). The group with Equia Forte Coat had significantly less color change than the group without Equia Forte Coat, as shown in [Table 1].
Table 1: Descriptive statistics of ΔE by groups and the result of independent sample t-test

Click here to view

   Discussion Top

This in vitro study of color stability of Equia Forte Fil with or without the Equia Forte Coat presents data based on exposure to cola, a drink consumed by many children and known to stain pediatric restorative materials.[19],[20],[21],[26]

In pediatric dentistry, many parents opt for esthetic restorations for their children, especially in anterior teeth.[36],[37] Children affected by ECC would benefit from the RMGICs until the primary teeth are replaced with permanent teeth or the patient is cooperative enough to receive a more esthetic restoration.

In the current study Equia Forte Coat, a hydrophilic low-viscosity nanofilled surface coating, sealed Equia Forte Fil and significantly reduced staining in the specimens after continuous immersion in cola for 7 days. Previous studies attributed the hydrophobic properties of materials such as CRs to their resistance to staining. They suggested that the hydrophilic particles in RMGICs may adversely affect their color stability.[26],[38] RMGICs are vulnerable to color change in the first hours of application and in the current study, it is postulated that Equia Forte Coat sealed and protected Equia Forte Fil from staining. In this study, the Equia Forte Coat, in spite of being hydrophilic itself, prevented the hydrophilic particles from significant discoloration. Rajic et al. reported that Equia Forte Coat seals GIC effectively leading to the reduced initial release of fluoride. In their study, they reported a significant reduction in the initial fluoride release, however fluoride release after setting continued to follow the same pattern regardless of being coated with Equia Forte Coat or not. This has also been reported in previous studies.[34],[39]

RMGICs are more vulnerable to discoloration in the first hours of application and in that period, they release the most fluoride.[34],[40],[41] The application of Equia Forte Coat might reduce the initial fluoride release, however in the current study, it significantly improved the color stability of Equia Forte Fil.

Both colorimeters and spectrophotometers have been used in similar studies to evaluate the staining of dental materials. In the current study, a colorimeter was used to measure the color change ΔE* values digitally. A standard illuminant against a consistent white background was used for each sample in order to prevent variability due to absorption or any other confounding color effects.[26]

Limitations of this in vitro study included the inability to measure marginal discoloration. Clinically, the margins tend to show more discoloration. Furthermore, the influence of saliva and the effects of salivary clearance on the color stability were not performed in this study. pH cycling could simulate the oral environment, however it was not used in this study. pH cycling typically reduces the color stability of RMGICs as they have a greater ion release when subjected to pH variations than when stored in artificial saliva or saline.[42] Moreover, the effect of thermocycling was not assessed in this study. According to Ren et al., a thermocycling stain challenge model can better represent the complex nature of the interactions between dietary colorants and CRs. Thermocycling may affect the surface integrity of the CRs and render them susceptible to discoloration.[42],[43] Finally, future studies are needed to assess the effect of Equia Forte Coat on the color stability of Equia Forte Fil in vivo.

The current study assessed the effect of the Equia Forte Coat on the color stability of Equia Forte Fil when stained with cola. Sixty disc-shaped specimens measuring 0.63 mm (1/4 inch) in diameter and 1.5 mm in thickness were fabricated of Equia Forte Fil shade B1. Half of the specimens were randomly coated with Equia Forte Coat. A colorimeter was used to assess the color of the material before and after immersion in cola for 7 consecutive days and color difference (△E) was identified using the Commission Internationale de l'Eclairage (CIE) L*a*b* coordinates. The application of the Equia Forte Coat significantly improved the color stability of Equia Forte Fil.

   Conclusion Top

The application of the Equia Forte Coat significantly improved the color stability of Equia Forte Fil.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

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