Effect of Food Colorants on Color of Denture Base Acrylic Resins.

BACKGROUND: Acrylic resin has been successfully used for complete denture fabrication for many years. Color stability is very crucial clinical properties for dental materials, and color change may be an indicator of aging or damaging of materials. AIM AND
OBJECTIVES: This study has been designed to determine the color stability of heat cure denture base acrylic resins in commonly consumed solutions causing stains.
METHODOLOGY: Four hundred disc samples of four commercially used heat cure denture base resins (Trevalon®, DPI®, Veracril®, and Pyrax®) were fabricated (100 in each group). These were checked for any change in optical density by immersing them in four different staining solutions (tea, coffee, turmeric, and betel leaf, i.e., paan) and synthetic saliva for 1-month synthetic saliva was taken as control. The denture cleansers were also evaluated for their efficacy determined by their ability to remove the stains caused by the staining solutions.
RESULTS: It was observed that Trevalon® showed least change in optical density and coffee illustrated the maximum potential for staining the denture base resins and is the most difficult to be removed using a denture cleanser.
CONCLUSION: It can be concluded that Trevalon® demonstrated maximum color stability. Among the staining solutions, coffee caused maximum stains. Copyright:

INTRODUCTION

Acrylic resin has been successfully used for complete denture fabrication for the past many decades. The advantages of these resins are the ease of manipulation, low cost, adequate physical and mechanical properties, biocompatibility, and satisfactory appearance. The disadvantages over the time are loss of elasticity, abrasion, porosity, and color change.[12345] The most important characteristic of all is color stability. Color change may be an indicator of aging or damaging materials. Furthermore, the aesthetic appearance of a prosthesis is certainly an important feature required by patients and must satisfy their expectations. The reason for color change is intrinsic and extrinsic factors. Intrinsic factors involve resin discoloration itself and matrix changes, occurring during the aging process of the material due to many physical and chemical conditions.[6] It has been suggested that thermocycling and contact with mouthwashes and colored beverages have influence over the color change of resin. Thus, oral hygiene and eating habits must be considered to preserve most of the acrylic resin properties, such as color stability, hardness, and durability, among others.[78910] Therefore, this study has been designed to determine the color stability of heat cure denture base acrylic resins in commonly consumed solutions causing stains.

METHODOLOGY

In this study, 400 discs samples of four different heat cure denture base resins were immersed in four staining solutions. A standardized disc of brass of dimension 50 ± 1 mm in diameter and 1 ± 0.05 mm in thickness was fabricated using precise milling instruments. The specimens were divided into four groups (Group I = Trevalon®, Dentsply, Gurgaon, India, Group II = DPI®, Bombay Burmah Trading Corporation, Mumbai, India, Group III = Veracril®, Surana Enterprises, Karnataka, India, Group IV = Pyrax®, Pyrax Polymars, Roorkee, India,) according to their commercial brand. Each group of sample was divided into five subgroups (S1 = tea, S2 = coffee, S3 = turmeric, S4 = paan, and S5 = synthetic saliva) of the staining solutions. Each subgroup consisted of 80 samples. Synthetic saliva was prepared by dissolving the following constituents in 1000 ml distilled water. Disodium hydrogen phosphate (0.26 gm), sodium chloride (6–70 gm), sodium dihydrogen phosphate (0.20 gm), potassium chloride (1.20 gm), and sodium bicarbonate (1.50 gm) tea solution was prepared by dissolving 17.50 g (three tablespoons) tea powder (Taj Mahal®) in 250 ml of water and then boiling it for 10 min. Coffee solution was also prepared by dissolving 17.50 g (three tablespoons) coffee powder (Nescafe®) in 250 ml of water and then boiling it for 10 min. Turmeric solution was prepared by dissolving 0.5 g turmeric powder in 250 ml of water and then boiling it for 10 min. Paan solution was prepared by dissolving the 25 g paan paste in 250 ml water. The pH of all the solutions was measured using a pH paper (Nualigens®). The samples were then incubated at 37 0C in an incubator and stored in a dark place for 1 month (to simulate oral conditions). These solutions were replaced on alternate days with fresh solutions ones to prevent any microbial colonization and to maintain uniform concentration. After 1 month, ten discs from each solution were evaluated for surface stain using a visible spectrophotometer. The visible spectrophotometer (Systronics 106®) was used to determine the optical density of the samples. For this 30%, H2O2 was used to leach out the stain on the samples and this leached out solution was evaluated in the spectrophotometer. The frequency of the spectrophotometer was set by setting the maximum absorbance in the yellowbrown range (490 m). Now, each disc was leached by H2O2 drop by drop and the collected solution was evaluated in the spectrophotometer. Data were noted down for each specimen. The data obtained from the present study were statistically analyzed using SPSS software version 11.

RESULTS

Results showed that maximum optical density of DPI® (5.01) after immersion in various staining solutions. Trevalon® shows minimum optical density (3.2). Figure 1 compares the optical density of all four groups using the Bonferroni Test. It is seen that Trevalon® showed a significant difference in mean values with DPI® (P = 0.001) and Pyrax® (P = 0.022). Figure 2 depicts that coffee stains were the most difficult to remove as compared to other stains. This was followed by paan stains followed stains caused by tea. Stains caused by turmeric were the most easiest to remove by either of the denture cleansers.

Figure 1

Color stability of resins used in dentures

Figure 2

Difficulty of removing stains from dentures

DISCUSSION

Discoloration of these resins results in aesthetic problems. Hence, maintenance of color stability of these resins is the key to long-term aesthetics of the denture. Thus, this study has been designed to determine the color stability of heat cure denture base acrylic resins in commonly consumed solutions causing stains. There is evidence that beverages and some artificial colorants used in food may increase the staining of acrylic resin.[1] The dark pigment of food and its low pH can cause drastic staining, negatively affecting the surface integrity by softening the matrix.[456] Therefore, this study has four commercially available denture base resins were evaluated for their color stability in six stain-causing solutions. After continuous immersion of the samples under these solutions, their optical density was evaluated using a visible spectrophotometer. In this study coffee was seen to cause maximum staining of the samples, followed by tea. This could be attributed to the fact that coffee and tea are acidic solutions as determined during the study. In a similar study conducted by Hersek et al.,[10] tannic acid present in tea and coffee caused the staining. Um and Ruyter[11] in their study reasoned the discoloration of resins by explaining the process of absorption and penetration of colorants into the organic phase of the resin materials as the compatibility of the polymer phase with the yellow colorants of coffee. The yellow colorants present in coffee were less polar and thereby less hydrophilic, than the yellow colorants of tea. This in vitro study only simulated a clinical condition in which many other factors can affect color; thus, it has its limitations. It is important to realize that other factors, isolated or associated, such as poor cleaning of removable prosthesis components, the oral environment, material porosity associated with the fabrication technique of the denture, surface flaws of the material, and the polishing surface may influence the color stability of acrylic resins. Therefore, additional studies must be performed to evaluate the interactions between coloring agents and acrylic resins.

CONCLUSION

All factors associated or not, influenced the color change of the acrylic resins assessed. Travlon®, out of the tested commercially available heat cure denture base resins, demonstrated maximum color stability after its immersion in different staining solutions coffee, owing to its acidic potential, cause maximum stains which are difficult to remove as compared to stains caused by other test solutions.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.