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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 9  |  Issue : 2  |  Page : 107-115

Comparative evaluation of effect of three beverages on color stability of two brands of acrylic denture teeth: An In vitro study


1 Department of Prosthodontics, PMS College of Dental Science and Research, Thiruvananthapuram, Kerala, India
2 Department of Prosthodontics, PMS College of Dental Science and Research, Thiruvananthapuram affiliated to The Kerala University of Health Sciences (KUHS), Thrissur, Kerala, India

Date of Submission06-Jul-2021
Date of Decision23-Aug-2021
Date of Acceptance07-Sep-2021
Date of Web Publication30-Nov-2021

Correspondence Address:
Sreelakshmy K S. Kammath
Department of Prosthodontics, PMS College of Dental Science and Research, Golden Hills, Vattapara, Venkode, Thiruvananthapuram - 695 028, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/dmr.dmr_23_21

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  Abstract 


Context: During clinical use, artificial teeth are exposed to saliva, beverages, and cleaning agents and such materials are prone to the absorption and adsorption processes. Certain foods can promote discoloration, surface degradation, and changes in other properties of artificial teeth. Aims: This study evaluated the effect of three different beverages (Dasamoolarishtam an Ayurvedic medicine, tea, grape juice, and distilled water) on color stability of two brands of acrylic resin denture teeth when exposed for four immersion times. Settings and Design: This is an in vitro experimental study. Subjects and Methods: Maxillary right central incisors of two brands of A1 shade were used. The specimens were placed in the center of the measuring head of a spectrophotometer with the aid of a silicone putty jig. Measurements were taken as follows, first (T0), after 1 day (T1), 7 days (T2), 15 days (T3), and 30 days (T4) of immersion in the solutions. Statistics: Comparison of color change among different beverages in each brand at different time interval was carried out using one-way ANOVA test (F test) with Scheffe Multiple Comparisons (post hoc test). Results: The results show that among the three beverages tested, Dasamoolarishtam produced maximum color changes. Conclusions: It was concluded that maximum color change was seen on exposure to Dasamoolarishtam and in Rolex teeth set.

Keywords: Acrylic denture teeth, Acryrock, color stability, Dasamoolarishtam, Rolex, spectrophotometer


How to cite this article:
S. Kammath SK, Bhaskaran S, Saratchandran S, Cherian SK, Babu SC, Joy AM. Comparative evaluation of effect of three beverages on color stability of two brands of acrylic denture teeth: An In vitro study. Dent Med Res 2021;9:107-15

How to cite this URL:
S. Kammath SK, Bhaskaran S, Saratchandran S, Cherian SK, Babu SC, Joy AM. Comparative evaluation of effect of three beverages on color stability of two brands of acrylic denture teeth: An In vitro study. Dent Med Res [serial online] 2021 [cited 2022 Oct 5];9:107-15. Available from: https://www.dmrjournal.org/text.asp?2021/9/2/107/331395




  Introduction Top


Acrylic resin denture teeth have the most extensive track record as a replacement for missing natural teeth. In this era where dental implants are an integral component of oral rehabilitation, acrylic teeth have retained their popularity. Their superior success rate can be attributed to properties such as a stronger chemical bond with the denture base, lightweight, lower risk of fracture, ease of modification, and simplicity in manufacturing. Porcelain has been linked to complications such as fracture and chipping. Against this backdrop, acrylic teeth have emerged as the frontrunners primarily due to reduction in the impact force of occlusal loads and better preservation of remaining structures. In addition, they offer economic and esthetic benefits.

Color stability is the property of a material to retain its color over a period of time and in a specified environment.[1] Change in color may be an indicator of aging or damage of materials.[2],[3],[4],[5],[6],[7] Moreover, the patient's expectation regarding the esthetic appearance of a prosthesis is certainly an important feature that must be satisfied. Intrinsic and extrinsic factors can discolor tooth-colored resin-based materials. Intrinsic factors such as the alteration of the resin matrix and the interface of matrix and fillers are involved in the discoloration.[8] Physicochemical conditions such as temperature and humidity may cause the intrinsic color of esthetic materials to change. Discoloration may be induced by extrinsic factors like adsorption or absorption of stains.[8],[9],[10],[11]

Artificial teeth are prone to absorption and adsorption processes during clinical use, particularly when exposed to saliva, liquids, and cleaning agents. Furthermore, some foods have been shown to cause discoloration, surface deterioration, and changes in the properties of artificial teeth. Color stability must be assessed to ensure the clinical longevity of acrylic teeth, as it is linked to a variety of factors, including stain resistance, microbial adherence, oral tissue health, and patient comfort, directly or indirectly. Moreover, even though reinforced acrylic denture teeth are cross-linked, they are still vulnerable to pigmentation. It has been noted by dentists that the esthetics of prostheses made with such acrylic teeth become undermined gradually in many patients. The dental market offers a large variety of denture teeth. A high-quality analysis of denture teeth properties that are supported by scientific findings is critical to permit the most effective selections by clinicians.

The effect of beverages on the color stability of direct and indirect restorative materials, as well as acrylic resin denture bases, has been demonstrated by several authors, but there have been few studies on the color stability of acrylic denture teeth. As a result, in this in vitro study, a spectrophotometer was used to examine color changes in acrylic teeth exposed to commonly consumed beverages. This study aimed to compare and evaluate the effect of three different beverages (tea, grape juice, Dasamoolarishtam an Ayurvedic medicine, and distilled water) on the color stability of two brands of acrylic resin denture teeth when exposed for four immersion times (1, 7, 15, and 30 days).


  Subjects and Methods Top


Institutional ethical clearance was obtained. One hundred and twenty-eight maxillary right central incisors of two brands [Table 1] of A1 shade were used for the study [Figure 1] and [Figure 2].
Table 1: The trade names, manufacturers, shades, and codes of the denture teeth used

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Figure 1: Acryrock teeth set

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Figure 2: Rolex teeth set

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  • Dasamoolarishtam is a liquid Ayurveda medicine used very commonly in the South Indian geriatric population as a general health tonic. This was obtained commercially (1000 ml/8 samples) [Table 2]
  • Commercially obtained grape juice with preservative (1000 ml/8 samples) [Table 2]
  • Tea solution was prepared with 10 preweighed teabags in boiling distilled water (1000 ml/8 samples). The solution was stirred for 10 s every 30 min until it cooled down to 37°C and then filtered through a filter paper [Table 2]
  • Distilled water was used as a control group using the same ratio [Table 2].
Table 2: The trade names, manufacturers, shades, and codes of the beverages used

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The teeth specimens were divided into two groups according to the brand specified, kept in individual vials, and labeled [Figure 3] and [Figure 4]. Before immersion in beverages, spectrophotometric measurements of all specimens were recorded. Individual vials were filled with three beverages and distilled water, 1000 ml/8 samples with each specimen being completely immersed and maintained at 37°C ± 1°C. The solutions were agitated every day to reduce particle precipitation and changed every 3 days. The specimen was removed, washed and the excess water was removed with a soft paper tissue, before each measurement.
Figure 3: Labelled specimens

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Figure 4: Teeth specimens labelled and divided

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The specimens were placed in the center of the measuring head of a spectrophotometer (X-Rite GretagMacbeth ColorEye 7000A CE7000A Color Eye Spectrophotometer System) [Figure 5] with the aid of a wooden frame and silicone putty jig using GC Flexceed Vinyl Polysiloxane impression material – putty type [Figure 6] and [Figure 7]. The silicone mold was prepared so that repetitive measurements for each tooth could be taken from the same tooth region. Furthermore, this mold enabled all teeth of each brand to seat exactly on the head of the spectrophotometer through which the light was passed. In addition, this setup prevented any external light source from entering the system. The silicone mold was mounted on a wooden frame. The frame was fabricated according to the dimensions of the measuring head of the spectrophotometer. This ensured that repeated measurements were taken in the same position. Moreover, all teeth of each brand could be seated identically. The mold was processed such that the labial surfaces of the teeth were at the same level as that of the silicone.
Figure 5: X-Rite Gretag Macbeth ColorEye 7000A CE7000A Color Eye Spectrophotometer System

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Figure 6: Wooden frame and silicone putty jig Acryrock

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Figure 7: Wooden frame and silicone putty jig Rolex

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Before measurement taking, the spectrophotometer was calibrated according to the manufacturer's instructions by using the supplied white calibration standard. The device was adjusted to a small area view, and the observer angle was set at 2°. The D65 standard light source with the reflectance mode was included. At a time, from the central region of the labial surface of each tooth, three measurements were taken. The average value of these three readings was calculated by the spectrophotometer and recorded. Measurements were taken as follows, first measurement (T0), after 1 day (T1), 7 days (T2), 15 days (T3), and 30 days (T4) of immersion in the solutions. Color changes were characterized using the Commission Internationale d'Eclairage L*a*b* color space (CIE L*a*b*).[12]

The color systems are quantitative systems with rectangular coordinates, and they have a meaningful relation to the visual perception of color differences. Total color differences are expressed by the formula,

ΔE = [(ΔL)2 + (Δa)2 + (Δb) 2]1/2,

where ΔL, Δa, Δb are differences in L*a* and b* values before (To) and after immersion at each time interval (T1, T2, T3, T4).

To relate the amount of color change (ΔE) recorded by the spectrophotometer to a clinical environment, the data were converted to the National Bureau of Standards units (NBS units) through the equation,

NBS units = ΔE × 0.92, where critical remarks of color difference are expressed in terms of NBS units.[13] These values are shown in [Table 3].
Table 3: National bureau of standards ratings*

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  Results Top


Categorical and quantitative variables were expressed as frequency (percentage) and mean ± standard deviation, respectively. Comparison of color change among different beverages in each brand at different time intervals was carried out using one-way ANOVA test (F test) with Scheffe Multiple Comparisons (post hoc test). Comparison of color change between brands for each beverage at different times was carried out by independent t-test. P < 0.05 was considered the threshold for statistical significance. Statistical analyses were performed by using a statistical software package SPSS, version 20.0. (IBM Corp. Released 2011. IBM SPSS Statistics for Windows, Armonk, NY).

When NBS values were evaluated for Dasamoolarishtam, both Acryrock and Rolex acrylic teeth set were observed to cause “noticeable” color difference at the end of day 30 [Graph 1]. Evaluating NBS value for grape juice and tea, Acryrock was observed to cause a “slight” color difference throughout the study. On the other hand, although the Rolex showed a “slight” color difference after 7 days of exposure, it gradually increased to a “noticeable” by day 30 [Graph 2]. It also showed a “noticeable” difference after 15 days of exposure to Tea [Graph 3]. On exposure to distilled water, there was not any significant change in color for both the Acryrock and Rolex acrylic resin teeth set [Graph 4].



In the comparison of the color difference of the two brands of acrylic resin teeth on exposure to Dasamoolarishtam, Acryrock teeth showed the most change in color on day 7 of exposure and Rolex teeth showed the most change in color on the 30th day of exposure. On exposure to grape juice, both the brands of teeth set showed a gradual increase in color change, the maximum of which was seen on the 30th day of exposure. On exposure to tea, Acryrock teeth showed the most change in color on day 1 of exposure and Rolex teeth showed the most change in color on day 30 of exposure [Graph 5] and [Graph 6].



Acryrock

In the comparison of the change in color when exposed to three different beverages in Acryrock at day 1, there was a significant change in color recorded on comparing grape juice with tea [Table 4]. A significant change in color was also noted on day 7 between Dasamoolarishtam and Grape juice, Dasamoolarishtam and Tea, and Dasamoolarishtam and Distilled water with Dasamoolarishtam showing the greatest amount of change in color [Table 5]. On day 15, a significant change in color was observed between Dasamoolarishtam and Grape Juice, Dasamoolarishtam and Distilled Water, Grape Juice and Tea, Tea and Distilled Water [Table 6] Day 30 showed a significant change in color between Dasamoolarishtam and Tea, Grape Juice and Tea, Tea and Distilled Water [Table 7].
Table 4: Comparison of change in color when exposed to three beverages in Acryrock at day 1

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Table 5: Comparison of change in color when exposed to three beverages in Acryrock at day 7

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Table 6: Comparison of change in color when exposed to three beverages in Acryrock at day 15

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Table 7: Comparison of change in color when exposed to three beverages in Acryrock at day 30

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Rolex

A significant change in color was observed on day 7 when comparing with Dasamoolarishtam [Table 8], [Table 9], [Table 10], [Table 11].
Table 8: Comparison of change in color when exposed to three beverages in Rolex at day 1

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Table 9: Comparison of change in color when exposed to three beverages in Rolex at day 7

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Table 10: Comparison of change in color when exposed to three beverages in Rolex at day 15

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Table 11: Comparison of color stability when exposed to three beverages in Rolex at day 30

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  Discussion Top


Clinical discoloration of esthetic materials may be caused by intrinsic and extrinsic factors. Extrinsic factors producing discoloration include staining by adsorption or absorption of stains or colorants.[8],[14],[15],[16],[17] Previous studies have shown that some dietary foods and beverages that are chemically acidic can cause surface degradation of restorative materials.[18],[19]

Colored solutions, coffee, tea, beverages, chlorhexidine, cola, and nicotine, are known to cause staining of oral tissues and dental restorations.[20] Dasamoolarishtam is a polyherbal formulation included in this study because of its popular use among the elderly. Bilva (Bael), Aegle Marmelos, Shyonaka (Oroxylum Indicum), Gambhari (Gmelina Arborea), Patala (Stereospermum Suaveolens), Agnimantha (Premna Mucronate), Shalaparni (Desmodium Gangeticum), Prishnaparni (Uraria Picta), Brihati (Solanum Indicum), Kantakari (Solanum Xanthocarpum), Gokshura (Tribulus) – (Tribulus Terrestris) are the main ingredients of Dasamoolarishtam.[21],[22] Further studies are required to identify the pigment-producing agent.

According to the FAO (Food and Agriculture Organization) of the total world grape production, 71% is used for wine, 27% is consumed as fresh fruit while 2% is used as a dried fruit. This is in complete contrast to India where close to 90% of the grapes produced are consumed fresh.[23] The color of red grapefruit juices was reported to be dominated by lycopene. A highly significant correlation between CIE A* value and lycopene content has been indicated.[24]

Tea leaves contain a considerable amount of flavonoid, which gives the tea its functional properties and flavor; however, flavins in tea leaves are reported to be the cause of discoloration. Um and Ruyter reported that tea caused more discoloration than coffee after 48 h of storage of five resin-based materials in coffee and tea solutions.[16]

Change in color can be evaluated visually or by instrumental techniques. In dental literature, the “perceptibility” of color differences is assessed by ΔE values. Each author adopted different criteria of perceptibility. The NBS rating system is a popular method for determining the degree of a color difference because it provides an absolute criterion, compensates for differences and disagreements in the criteria used and provides a system for converting E values to clinically significant remarks. As a result, corresponding NBS units were calculated in this study to assess the color difference caused by immersion time and/or solution type. It was found that the NBS values for both brands when immersed in Dasamoolarishtam were >1.5 meaning that color change was noticeable [Graph 1].

In this study, the instrumental method was preferred for evaluation because it is a sensitive and objective method for investigating color change. This method achieves a reproducible means for determining when the change in color occurs below visual perception levels. Investigators have evaluated the performance of devices used for color analysis. These authors concluded that all the instruments were able to assess color with precision, although the measurements varied somewhat depending on the instrument used and the type of material surface being measured.[25],[26],[27] Since instrumental measurements eliminate the subjective interpretation of visual color comparison, spectrophotometers are used instead of visual evaluation. Color difference (ΔE) was calculated from a formula previously mentioned.

In dentistry, a discoloration that is more than perceptible (ΔE* <1.0) will be referred to as acceptable up to value ΔE* =3.3. This is considered to be the upper limit of acceptability in subjective visual evaluations. In this study, the ΔE values exceeded 3.3 in the Dasamoolarishtam group of Rolex teeth set upon 30-day immersion [Table 7].

It is known that obtaining conditions of the oral environment in vitro is not easy. To simulate in vivo conditions in this study, 3 different beverages (Dasamoolarishtam, tea, grape juice) and the distilled water were used at a constant temperature of 37°C ± 1°C. Many investigators evaluated the coloration effect of tea, coffee, nicotine, erythrosine, and other drinks and of time-lapsed artificial aging method either on natural teeth or on aesthetic dental materials.[28] However, limited research has been conducted under in vivo conditions in their studies.

It was pointed out that there is a correlation between color and discoloration in provisional restorative materials and dental composites and was confirmed that lighter materials discolor more markedly than darker ones.[28],[29] On this basis, teeth of shade A1 were selected for this study because the exhibited staining effect is more distinct. Nonetheless, the effect of staining solutions on darker teeth should be further evaluated. Representative teeth brands were taken for this study and though both Acryrock and Rolex consist of high-molecular-weight resin (polymethylmethacrylate cross-linked), in double chromatic layers, the difference in the quantity of cross-linking, plasticizing agents and pigments, may account for the differences in color change for each brand of artificial teeth.

The present study demonstrated that the effect of beverages resulted in differences in color stability. In in vitro color stability studies, a period of 4 weeks of immersion may be considered to be too long. However, to reach the cumulative staining results of these solutions, it was decided to continue testing until day 30. Although proportional increase in staining with time has been reported in previous studies, in the present study, time was not found to be a significant factor.[30],[31]

Tooth brushing and cleaning can have a profound effect on the staining but in this study, the experimental tooth specimens were not subjected to any cleaning procedure between the different immersion intervals. Hence, the clinical conditions might not be accurately reflected. Thus, the results obtained herein might serve to reveal the consequences of low-quality denture care. It can be stated that this kind of in vitro experiments should be supported by planned in vivo observations taking dietary and hygiene habits of the patients into consideration to increase the longevity of acrylic denture resin teeth.


  Conclusions Top


Two commercially available denture teeth were evaluated after day 1, day 7, day 15, and day 30 of immersion in various beverages. Within the limitations of this in vitro study, these conclusions can be drawn:

  • Measurements of exposure to Dasamoolarishtam showed the maximum color change
  • The highest color difference mean was obtained in the Dasamoolarishtam on day 30 of measurement of the Rolex teeth set
  • Further research in the identification of the pigment-producing substance in Dasamoolarishtam is required
  • In vitro experiments supported by planned in vivo observations taking dietary and hygiene habits of the patients into consideration can be designed
  • Methods of educating patients about the possibility of staining, instructions in proper hygiene, and options for removing dentures while taking Ayurvedic medicine to avoid staining must be implemented.


Ethical clearance

The study was approved by the Institutional Ethics Committee of PMS College of Dental Science & Research on 30-Dec-2016 (Approval No. PMS/IEC/2016/29 ).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10], [Table 11]



 

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