|Year : 2019 | Volume
| Issue : 1 | Page : 30-34
A digital analysis comparing the surface staining characteristics of two commercially available porcelains on exposure to commonly consumed beverages
Nitasha Gandhi, Surbhi Mehdiratta, Nirmal Kurian, Neethu Roy, Vijay Alageshan, George Abraham
Department of Prosthodontics and Crown and Bridge, Christian Dental College, CMC, Ludhiana, Punjab, India
|Date of Submission||19-Apr-2018|
|Date of Decision||29-Apr-2018|
|Date of Acceptance||24-Jun-2018|
|Date of Web Publication||14-Feb-2019|
Department of Prosthodontics and Crown and Bridge, Christian Dental College, CMC, Ludhiana - 141 008, Punjab
Source of Support: None, Conflict of Interest: None
Aim: This in vitro study aimed to evaluate the color stability of two commercially available porcelain systems (Vita VMK®, VITA Zahnfabrik GmbH and Ceramco-3, Dentsply, India) against discoloration caused by commonly consumed beverages using digital analysis. Materials and Methods: Sixty porcelain samples in disc form were fabricated and divided into two groups (Ceramco-3® and Vita VMK®) consisting of thirty samples each. They were photographed digitally utilizing CIELAB system to obtain the baseline L*, a*, b* values. Samples were then immersed in test solutions for 180 days and the posttreatment images of the test materials were acquired at the 30th, 90th, and 180th day. All L*, a*, and b* values were analyzed by a graphic software, and the total color change (ΔE*) of each specimen was calculated. Statistical Analysis Used: Statistical analysis of the mean ΔE values among the groups was achieved by one-way analysis of variance paired Student t-test, post hoc Tukey's honest significant difference test, and the level of significance was set as 0.05. Results: Statistical analysis did not reveal a significant difference between the groups with the Group II (Vita VMK®) showing slightly more discoloration as compared to Ceramco-3® when immersed in all the test samples. It was also observed that both the feldspathic porcelains exhibited a greater color change when immersed in coffee when compared to tea. Conclusion: Both Ceramco-3® and Vita VMK® after immersion in test solutions showed minimum color change (i.e., maximum color stable) in water units and maximum color change in coffee with Vita VMK® exhibiting more change than Ceramco-3®.
Keywords: Beverages, CIELAB, color analysis, digital analysis, porcelain systems
|How to cite this article:|
Gandhi N, Mehdiratta S, Kurian N, Roy N, Alageshan V, Abraham G. A digital analysis comparing the surface staining characteristics of two commercially available porcelains on exposure to commonly consumed beverages. CHRISMED J Health Res 2019;6:30-4
|How to cite this URL:|
Gandhi N, Mehdiratta S, Kurian N, Roy N, Alageshan V, Abraham G. A digital analysis comparing the surface staining characteristics of two commercially available porcelains on exposure to commonly consumed beverages. CHRISMED J Health Res [serial online] 2019 [cited 2019 Aug 18];6:30-4. Available from: http://www.cjhr.org/text.asp?2019/6/1/30/252290
| Introduction|| |
The revolution in cosmetic dental materials and emerging dental technologies along with improved living standards support the view that esthetic considerations will become a major concern for patients seeking prosthodontics services in the future. A stronger emphasis on esthetics has led to rapid development and use of newer esthetic restorative materials. Restoration of the smile is one of the most challenging and satisfying services a prosthodontist can render to a patient. The past few decades have seen remarkable advancements in the properties and applications of dental ceramics. It has been established as a definitive anterior esthetic restorative material because of its natural appearance, good wear resistance, color stability, and optical properties that make it simulate natural teeth. Even though porcelain restorations are considered to be color stable, discoloration is one of the primary factors which can lead to their failure that may be due to intrinsic or extrinsic factors. Intrinsic factors involve changes within the material itself and extrinsic factors involve adsorption or absorption of stains in the oral cavity. Many studies have been done to evaluate staining characteristics of composites,,, but only a limited number have been carried out for porcelain. Thus, this in vitro study aimed to evaluate the color stability of two commercially available porcelain systems (Vita VMK®, VITA Zahnfabrik GmbH and Ceramco-3®, DENTSPLY India), against discoloration caused by commonly consumed beverages, using digital analysis.
| Materials and Methods|| |
In this study, the staining potentials of common beverages (tea and coffee) and staining characteristics of two commercially available ceramic systems (Ceramco-3® and Vita VMK®) were investigated.
Sixty porcelain samples in disc form (1 cm in diameter and 1 mm in thickness) were fabricated and divided into two groups, that is, Group I (Ceramco-3®) and Group II (Vita VMK®) consisting of thirty samples each. A metallic jig consisting of a base and two templates of standardized dimensions was fabricated to ensure dimensional standardization of all samples [Figure 1]a,[Figure 1]b,[Figure 1]c. Sixty wax patterns were made in the base of a metallic jig and sprued at the center [Figure 1]d. Casting was carried out using phosphate-bonded investment material (Vesto-Fix®, DFS-DIAMON GmbH) strictly following the manufacturer's instructions. An induction casting machine (Fornax®, BEGO GmbH) was used with nickel–chromium alloy (NDN®, DFS_DIAMON GmbH) for fabrication of the disc specimens. Any residual surface investment was removed by sandblasting with 100 μm aluminum oxide particles. The metal discs were finished with the help of carborundum discs and metal trimmers and were sandblasted to achieve a uniform thickness with of 1 cm × 1 mm. The cast specimens prepared then were taken up for ceramic application. Thirty samples were prepared by layering Ceramco-3 feldspathic porcelain over the metal discs. The specimens were placed at the base of the jig and two overlays of paste opaque were applied followed by ceramic firing, according to the manufacturer's instructions. This was followed by placement of first metal template over the base of the jig and application of standardized dentine layer of 1 mm thickness over the specimens. Enamel layer was then veneered using the same technique as for dentine layer following which the samples were fired. Firing was done according to manufacturer's instructions and the samples were finished with a diamond bur to achieve a uniform thickness of 3.5 mm and then glazed. Using the same technique, 30 samples were prepared by veneering of Vita VMK® porcelain on the cast specimens. The samples were then evaluated for color and immersed in different test solutions as given below [Figure 2]a:
|Figure 1: (a) Base of metallic jig (b and c) templates for veneering dentin and enamel layer (d) wax pattern spread at the center|
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|Figure 2: (a) Samples placed in water, coffee, and tea. (b) Bottles kept in incubator|
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- 1.5 g of coffee powder was added in 50 ml of boiling water, simmered for 5 min, and then filtered with a filter paper.
- 1.5 g of tea leaves was added to 50 ml of boiling water, simmered for 5 min, and then filtered with a filter paper.
- 50 mL of distilled water.
Test solutions were then kept at a constant temperature of 50° ± 1°C in an incubator [Figure 2]b and were changed everyday. Baseline readings for color were recorded. At the end of test period (30th, 90th, and 180th day), the samples were removed, dried with tissue paper, and analyzed digitally for color change. All specimens were placed on a black background to acquire a digital image [Figure 3]. A digital single-lens camera (NIKON® D3400) secured on a tripod, with 40 cm. Object–camera distance was oriented perpendicular to the test specimen to acquire the digital image. The image was taken at 11:00 am, under daylight on a clear day at a color temperature of around 5500K; saved in a tagged image file format and was later resolved on a 24-bit resolution screen for further analysis using a commercial graphics software (Adobe Photoshop 6.0®, Adobe Systems USA).
|Figure 3: Ceramic specimens (Ceramco-3®) laid out on a black background before immersion in test solutions|
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It is possible to quantify color using instrumental measurements expressed in the coordinates of a color order system. CIELAB units have been used for color quantification. In CIELAB system, the color space consists of three coordinates L*, a*, and b*. The L* refers to the lightness coordinate, and its value ranges from 0 for perfect black to 100 for perfect white. The a* and b* are the chromaticity coordinates in the red–green axis and yellow–blue axis, respectively. Positive a* values reflect the red color range and negative values indicate green color range. Similarly, positive b* values indicate yellow color range while negative values indicate the blue color range. The differences in the lightness and chromaticity coordinates (ΔL*, Δa*, Δb*) as a result of ultraviolet light exposure are determined first, and the total color change (ΔE*ab) can be calculated using the following relationship.
ΔE*ab = (ΔL*2 + Δa*2 + Δb*2) 1/2.
During the analyzes, fixed circular areas (74 pixels) were selected in the middle-third portion of each sample. The L*, a*, b* values of these areas were measured three times by application of the histogram function of the software, and the mean values were recorded.
Statistical analysis of the mean Δ E values among the groups was achieved by one-way analysis of variance (ANOVA), paired Student t-test, and post hoc Tukey's Honest significant difference (HSD) test. The level of significance was set as 0.05.
| Results|| |
Statistical analysis of the mean Δ E values among the groups was done using one-way ANOVA and the level of significance was set as 0.05 [Table 1]. A statistically significant difference was observed (at the 30th, 90th, and 180th day) in the color change of both Group 1 and Group II when immersed in tea and coffee when compared to water (control), with the Δ E values of coffee greater than tea [Table 1].
|Table 1: Comparison of ΔE (mean values±standard deviation) of each feldspathic porcelain (intragroup) on immersion in each of the beverages (n=10)|
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A paired Student t-test and post hoc Tukey's HSD test were applied to compare the color change between the two groups on exposure to each of the test samples. The difference observed between the two groups at the 30th day, 60th day, and 180th day was not found to be statistically significant [Table 2].
|Table 2: Comparison of ΔE (mean values±standard deviation) between the two groups of feldspathic porcelains (intergroup) on immersion in tea, coffee as compared to the control (water)|
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| Discussion|| |
The goal of esthetic restorations is to achieve morphologic, optical, and biologic acceptance. Of all the esthetic restorative materials known today, ceramics have proven to be the most natural in appearance, texture, color, reflectance, and translucency. Color deterioration has been one of the main causes (38%) of the replacement of a dental prosthesis. Recently, clinicians have reported the difficulties encountered with discoloration of dental porcelain. With the help of this study, an attempt was made to compare staining characteristics of two commonly used porcelains on exposure to different beverages. The samples, immersed in tea, coffee, and distilled water, were stored at 50°C ± 1°C to simulate the clinical discoloration potential. As shown by previous studies, changes produced in samples stored for 1 month at an increased temperature of 50–60°C could be well correlated with color change obtained after storing for 12 months at 37°C.
To date, the staining properties of beverages have been established using spectrophotometric analyzes. Digital shade analysis systems have been administered as an alternative method for color analysis. Studies have shown that color measurements obtained with digital analysis method were in accordance with those of spectrophotometric evaluation and utilize the CIELAB color space for color characterization.,
Recent advances in photography and computing have resulted in the widespread use of the digital single-lens reflex (SLR) camera for color imaging. This new device is capable of recording digital data from an object, which may subsequently be used to produce an image when viewed on a computer and may be transmitted through the internet. Images produced through a digital SLR camera may be analyzed using appropriate imaging software enabling the collection of color values from the whole or parts of such images. This is a much cheaper process than the use of traditional color measurement devices such as spectrophotometers or colorimeters.
In digital imaging, using a black cardboard background is recommended as this would eliminate the effect of scattering light on the images, which may, in turn, interfere with the color measurements.
Technological advances have allowed digital images to be archived and morphed with computer imaging software, which has led to the advanced capability for photographic analysis using imaging software.
According to CIELAB system principle, if a material is completely color stable, no color difference will be detected after its exposure to the testing environment (ΔE = 0). The clinical relevance of the present study depends on how much color change (ΔE) is considered perceptible.
It is shown that a ΔE <1 is not considered perceptible to most patients with normal color vision. However, presuming that an acceptable color difference can be 2 or 3 times of the detectable limits, color differences <3.7 CIELAB units are generally stated as clinically acceptable. Considering the mean staining intensity of all the solutions used for the present study, coffee was found to cause more discoloration than tea and water. This is also in general concurrence with the results of some previous studies.,, Douglas in 2000 evaluated the color stability of various indirect resins (Artglass®, Zeta®, Targis®, and Belleglass®), one direct resin (Herculite XRV®) and porcelain system (Omega 900®) after accelerated aging for 300 h. Porcelain was reported to discolor the least and was not significantly different from Zeta and Art glass that showed a color change in the range of 0.62–3.4 Δ E units. Coffee was found to cause more discoloration than tea, Coca-Cola, and water. The reason for this color change can be explained on the basis of basic components of the porcelain, that is, glass, which has been reported to discolor with test solutions used in the present study. This was supported by Gross and Moser who reported that materials containing glass beads as filler were stained with beverages such as coffee and tea.
The two porcelains used in the study showed a mean color change ranging from 0.74–3.68 ΔE units after 90 days. The overall color change was low as compared to that reported by Jain C et al., in which they compared three porcelain systems, namely Vita (VMK 95®), Ceramco-3®, and Duceram Kiss® and concluded that there was a color change in the range of 0.72–20.92 ΔE units after 90 days. The color changes were in a range similar to that reported in a study by Razzoog et al., in which two porcelain systems, namely Ceramco® and Procera®, showed a color change in the range of 0.5–1.5 ΔE units after an accelerated aging process for 900 h in a weathering chamber.
The maximum color change seen in this study was 5.01 ΔE at the end of a test period of 180 days. Although both the porcelains used in the present study are feldspathic and more or less have same composition and firing cycles, but they have shown slightly different amount of color change over a period of 180 days. This variation may be attributed to the difference in percentage of basic individual composition. Also it is not known, whether it is the glaze layer which undergoes disruption due to acidic solutions and cause retention of stains or these are absorbed within the body of the porcelain. The temperature, pH changes, role of saliva in oral cavity, and polishing methods used might also subject porcelain to differential staining. This being the limitation necessitates the need for future studies.
| Conclusion|| |
Within the limitations of the study, it can be concluded that both Ceramco-3® and Vita VMK® after immersion in test solutions showed minimum color change (i.e., maximum color stable) in water units and maximum color change in coffee. The difference in staining between both the porcelain groups used for the study (Ceramco-3® and Vita VMK®) was not found to be significant with Group II (Vita VMK®) showing slight more discoloration as compared to Ceramco-3 when immersed in all the test samples.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]