Stain deposition modifies the transmission

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1 Tooth Whitening/Bleaching Toothpastes containing abrasive and chemical whitening agents: efficacy in reducing extrinsic dental staining Cristina Neves Girao Salgado Soares, DDS n Flavia Lucisano Botelho do Amaral, DDS, MS, PhD n Marcelo Ferraz Mesquita, DDS, MS, PhD Fabiana Mantovani Gomes Franca, DDS, MS, PhD n Roberta Tarkany Basting, DDS, MS, PhD n Cecilia Pedroso Turssi, DDS, MS, PhD This in vitro study evaluated the efficacy of toothpastes containing abrasive and chemical whitening agents in reducing the extrinsic discoloration of dental enamel. Sixty slabs of dentin from human teeth were sealed so that only the enamel surface was exposed. The enamel surfaces were photographed for initial color assessment. Staining was performed by immersing the dental slabs in 0.2% chlorhexidine solution for 2 minutes and then in black tea for 60 minutes. This process was repeated 15 times. Photographs were taken at the end of the staining process, and the slabs were divided into 5 groups (n = 12), 3 to be brushed with toothpastes containing chemical whitening agents (2 containing phosphate salts and 1 containing phosphate salts plus hydrogen peroxide) and 2 to represent control groups (ordinary/nonwhitening toothpaste and distilled water). The dental slabs were subjected to mechanical toothbrushing with toothpaste slurry or distilled water, according to each group s specifications. After brushing, more photographs were taken for color analysis. The results showed a significant reduction in luminosity after the staining process in addition to an increase in the colors red and yellow (P < 0.001). After brushing, there was a significant increase in luminosity and a reduction in both red and yellow (P < 0.001). However, there was no observed difference between the changes in color values in dental enamel slabs brushed with whitening toothpastes and the changes found in slabs brushed with ordinary toothpaste. The whitening toothpastes did not outperform an ordinary toothpaste in the removal of extrinsic staining. Received: March 14, 2014 Revised: July 14, 2014 Accepted: August 5, 2014 Key words: enamel, staining, toothbrushing, toothpaste, whitening Stain deposition modifies the transmission of light and optical properties of tooth structure. 1 Extrinsic stains, localized to exposed enamel and dentin in the mouth, could originate from chromogens that either chemically interact with the tooth or are deposited in the biofilm. 1 Oral rinses and nonmetallic stains from the diet are major causes of dental staining. 1-3 Whitening toothpastes are highlighted among the alternatives available for the prevention and/or removal of tooth stains. 4 These products act via the presence of abrasive, chemical, or optical agents. 4 Abrasive agents work during the brushing process, when particles such as silica, carbonate, and bicarbonate remove extrinsic stains. 4 Although whitening toothpastes generally present abrasiveness superior to that of ordinary (nonwhitening) toothpastes, and the whitening effects of whitening toothpastes correlate positively with their radioactive dentin abrasivity (RDA) values, both whitening and ordinary toothpastes may possess the equivalent capacity to remove stains. 5-7 To obtain greater efficacy in the removal of stains, toothpastes may incorporate chemical whitening agents, such as hydrogen peroxide, sodium citrate, and phosphate salts, which react with the chromogen molecules or dissolve stains on the tooth surface. 4 Some studies have demonstrated the efficacy of whitening toothpastes that contain chemical agents such as sodium tripolyphosphate and hydrogen peroxide In fact, toothpastes with chemical whitening agents have been indicated for both the removal and prevention of stain formation. 12 However, currently little is known regarding the whitening capacity of toothpastes that contain phosphate salts and/or hydrogen peroxide in combination with abrasive agents. Therefore, this study evaluated the ability of toothpastes containing both abrasive and chemical whitening agents to reduce extrinsic staining on dental enamel. Materials and methods Experimental design This study was arranged as a completely randomized design with a unifactorial scheme. Dental slabs were divided into 5 groups (n = 12), 3 of which were to be brushed with toothpastes containing abrasive and chemical whitening agents 2 containing phosphate salts and 1 containing phosphate salts plus hydrogen peroxide (Table 1). In addition, 2 control groups were established: in 1 group, slabs were brushed with an ordinary toothpaste (nonwhitening, containing abrasive agents only) and, in the other, slabs were brushed with distilled water. The response variable was color alteration, measured in the 3-dimensional color space with the Commission Internationale de l Eclairage (CIE) L*a*b* system. 13 Preparation and sealing of tooth slabs This study was approved by the Research Ethics Committee of the Sao Leopoldo Mandic School of Dentistry (protocol No. CAAE ). Thirty extracted impacted third molars, donated by the local tooth bank, were cleaned with a scalpel blade, polished with pumice stone and a Robinson brush used at low speed, and then placed in 0.1% thymol solution. A precision saw (IsoMet 1000 Precision Saw, Buehler) was used to section the teeth at the cementoenamel junction. The coronal portions were sectioned to obtain 60 slabs of enamel (3.0 mm wide 3.0 mm long 2.5 mm thick). e24 November/December 2015 General Dentistry

2 Table 1. Composition of the toothpastes used in the study. Product name Chemical whitening agents Other ingredients Batch No. Colgate Optic White 2048MX1124 Colgate Luminous White Crest 3D White (Procter & Gamble) Colgate Max Fresh (ordinary toothpaste) Calcium pyrophosphate, tetrapotassium pyrophosphate, hydrogen peroxide Pentasodium triphosphate, tetrapotassium pyrophosphate Disodium pyrophosphate NA Sodium monofluorophosphate, propylene glycol, PEG/PPG 116/66 copolymer, PEG-12, glycerin, PVP, flavor, sodium lauryl sulfate, silica, sodium saccharin, phosphoric acid, sucralose, water, butylated hydroxytoluene Sodium fluoride, water, hydrated silica, sorbitol, glycerin, PEG-12, sodium lauryl sulfate, cellulose gum, polyethylene, cocamidopropyl betaine, xanthan gum, sodium saccharin, sodium hydroxide, titanium dioxide (CI 77891), Blue 1 Lake (CI 4290) Sodium fluoride, water, hydrated silica, sorbitol, sodium lauryl sulfate, sodium hydroxide, cellulose gum, mica (CI 77891), polyethylene/blue 1 Lake (CI 42090), sodium saccharin, xanthan gum, carbomer, limonene Sorbitol, water, hydrated silica, sodium lauryl sulfate, cocamidopropyl betaine, PEG-12, cellulose gum, sodium saccharin, sodium fluoride, hydroxypropyl methylcellulose, Blue No. 15 (CI 74160), Yellow No. 10 (CI 47005) Abbreviations: CI, Color Index; NA, not applicable; PEG, polyethylene glycol; PPG, polypropylene glycol; PVP, polyvinylpyrrolidone. 1314BR123B 03/ MX111F An electric wax carving pen (Plaster Industria e Comercio, Ltda.) was used to seal the dental slabs with sculpture wax (Kota), except for the external surface of the enamel. Color at the baseline timepoint The dental slabs were photographed with a digital camera (Sony α200, Sony Corporation of America) and a Sigma photographic lens (Sigma DGMACRO 105 mm, Sigma Corporation of America) held in a stabilizing device to standardize the height of the captured image. The camera function was set to A, 1/125, F16, ISO 200, with flash and a 2-second timer. Lighting, aperture, and height were also standardized. An external incandescent lamp light source, positioned at 9 o clock, was also used. The photographs were cropped and analyzed with image processing software (Photoshop 7.02, Adobe Systems, Inc.), following the methodology proposed by Lee et al. 14 The images were cropped to standardize the area for color analysis. A grid was established, in which the 3-dimensional CIE parameters, L*, a*, and b*, were measured at 9 equidistant points in all images. In the CIE L*a*b* system, the L* axis presents the measure of lightness of an object; a*, the variation of color along the green-red axis; and b*, the color variation along the blue-yellow axis. The L* parameter is measured on a scale from 0 (black) to 100 (white). The values of a* and b* vary between 80 and +80. For a*, positive values represent red and negative values represent green; for b*, positive values represent yellow and negative values represent blue. Staining protocol The dental slabs were darkened, as per the method used by Sheen et al, with 0.2% chlorhexidine (CHX) solution and black tea. 15 Each specimen was initially exposed to 1 ml of 0.2% CHX solution (RiohexDermo Suave, Rioquimica Industria Farmaceutica) for 2 minutes. The slabs were rinsed with distilled water for 5 seconds. Each specimen was then immersed in 1 ml of black tea (prepared using 5 g of tea to 500 ml of water), for 60 minutes at room temperature. The slabs were rinsed with distilled water for 5 seconds. The aforementioned sequence was performed 15 times in succession, and the specimens were kept in relative humidity at 4 C between each cycle. Color at the poststaining timepoint The specimens were photographed once again, as per the aforementioned specifications, in order to evaluate the variations in color shown on the prestaining and poststaining photographs. The data were again obtained via evaluation of CIE L*a*b* color. Brushing with whitening toothpastes The stained slabs were positioned in the slots of an automatic brushing machine (MSE, Elquip). Soft-bristle toothbrushes (Oral-B 40 Indicator, Procter & Gamble) were mounted, and a standardized force of 0.3 N was applied to the surface of each slab. In the toothpaste groups, 1350 brushing strokes (which correspond clinically to brushing 3 times daily for 30 days) were performed in the presence of 3 ml of a slurry prepared from the corresponding toothpaste. To obtain the slurry, each toothpaste was suspended in deionized water at a 1:3 toothpaste-water ratio, in weight. The brushing heads travelled horizontally at a speed of 4.5 strokes per second in a thermostatically controlled environment at 37 C (± 5 C). After testing, the slabs were removed from the brushing machine and rinsed with tap water. In the distilled water control group, the same steps were performed, but the toothpaste slurry was replaced with distilled water. Color at the postbrushing timepoint Photographs were taken following the brushing stage, using the same specifications as previously described. Likewise, color was assessed using CIE L*a*b* color space. General Dentistry November/December 2015 e25

3 Tooth Whitening/Bleaching Toothpastes containing abrasive and chemical whitening agents The total difference between color (ΔE*) of the slabs in the poststaining and postbrushing conditions was calculated using the following formula: ΔE* = (ΔL*) 2 + (Δa*) 2 + (Δb*) 2 Statistical analysis The changes in L* values from the baseline to poststaining timepoints and from the poststaining to postbrushing timepoints were compared with Student t tests. The same statistical approach was used for the a* and b* parameters. ΔE*, calculated between the poststaining and postbrushing conditions, underwent 1-way analysis of variance and Tukey multiple comparisons test. A significance level of 5% was adopted. The calculations were performed with SPSS statistical software, version 20 (IBM Corporation). Results The Student t test indicated that, compared to baseline, the poststaining slabs exhibited a significant reduction in lightness of color (L*; P < 0.001) and an increase in the colors red (a*; P < 0.001) and yellow (b*; P < 0.001). When the postbrushing conditions were compared to the poststaining conditions, a significant increase in lightness (L*; P < 0.001) and a reduction in the red (a*; P < 0.001) and yellow (b*; P < 0.001) were observed. One-way analysis of variance applied to the change in color (ΔE*) from the poststaining to postbrushing timepoints demonstrated that there was a significant difference between the groups tested (P < 0.001). A Tukey test indicated that significantly higher values of ΔE* were measured when both whitening and ordinary toothpastes were used (distilled water vs Colgate Optic White, P < 0.001; distilled water vs Colgate Luminous White, P < 0.001; distilled water vs Crest 3D White, P < 0.001; distilled water vs Colgate Max Fresh, P < 0.001) and that there were no statistically significant differences between toothpastes (Colgate Optic White vs Colgate Luminous White, P = 0.817; Colgate Optic White vs Crest 3D White, P = 0.557; Colgate Optic White vs Colgate Max Fresh, P = 0.849; Colgate Luminous White vs Crest 3D White, P = 0.994; Colgate Luminous White vs Colgate Max Fresh, P = 1.000; Table 2. Mean (SD) changes in color (ΔE*) from poststaining to postbrushing conditions. Chemical whitening agents Pentasodium triphosphate and tetrapotassium pyrophosphate Calcium pyrophosphate, tetrapotassium phosphate, and hydrogen peroxide Disodium pyrophosphate None (ordinary toothpaste) None (distilled water) Means with different superscript lowercase letters are significantly different (P < 0.001). Crest 3D White vs Colgate Max Fresh, P = 0.985; Table 2). The lowest ΔE* values were encountered in the distilled water control group. Discussion To widen the available knowledge on the efficacy of whitening toothpastes in extrinsic stain removal, this in vitro study focused on the action of products containing combinations of abrasive and chemical whitening agents, such as hydrogen peroxide, sodium citrate, and phosphate salts. 4 To simulate the clinical situation in which enamel undergoes whitening, a staining protocol based on extrinsic pigment deposition on the enamel was adopted. In other studies, different staining protocols have been used, such as coffee, coffee combined with cigarette smoke, food coloring, black tea, and black tea combined with CHX solution. 1,11,15-22 In the present study, the staining protocol adopted used 0.2% CHX and black tea. Despite theories that attribute CHXrelated staining to the presence of pellicle formation, it has been demonstrated that, even in the absence of accumulated film, both teeth and acrylic resin specimens become stained when exposed to CHX solution. 1,23 Such staining is enhanced by exposure to black tea, which promotes the deposition of brownish or blackish chromogens. The use of CHX followed by black tea to induce tooth staining has been adopted by many authors. 8-10,24 It is worth noting that the number of cycles used in the present study (15) was based on a previous investigation, which showed that the chromogenic potential of black teas was ΔE* 21 (8) a 18 (8) a 21 (7) a 19 (7) a 4 (1) b 3- to 7-fold higher when the number of staining cycles in CHX followed by black tea increased between 5 and 15 cycles. 25 The significant reduction in lightness and the increase in red and yellow at the poststaining timepoint, in relation to prestaining conditions, validates the staining method, which was able to modify light transmission and the optical properties of the tooth structure, as measured by the methodology used. 1 In the present study, when the stained enamel underwent toothbrushing, there was no difference in color changes achieved with either whitening or ordinary toothpaste. This finding corroborates previous studies that reported no superior performance of whitening over ordinary toothpastes in removing extrinsic stains. 5,7,9 In fact, it has been demonstrated that whitening of stained enamel is the result of the abrasivity of the toothpaste. 4,5,7 However, the ability to remove stains does not necessarily have a direct relationship to toothpaste abrasivity. 26 This statement finds support in the fact that although 1 toothpaste (Colgate Optic White) had an RDA value of 98, and others were reported to have RDA values of 175 (Colgate Max Fresh) and more than 200 (Crest 3D White), the products did not differ from each other in the resulting enamel ΔE* values. 27 It is recognized that certain types of chemical agents present in toothpaste may help to reduce stains by inhibiting their formation or by removing them. 8 The whitening toothpastes tested in the present study contained chemical whitening agents (in the form of pyrophosphates with or without triphosphates), which e26 November/December 2015 General Dentistry

4 have been proven to remove stains via dislocation of anions and negatively charged macromolecules present in the enamel. 28 Nevertheless, in the present study, these agents did not appear to influence the ability to remove stains during toothbrushing. However, despite the fact that the staining protocol in the present study was chosen for its notorious staining potential, it is possible that the lack of difference between results achieved by whitening and ordinary toothpastes may have been the result of weak absorption of stains on the enamel surface. Some authors have achieved effective removal and prevention of extrinsic stains by using whitening toothpastes with abrasive particles, while others have reported satisfactory whitening results with toothpastes containing abrasive and chemical components, such as sodium tripolyphosphate and pentasodium triphosphate. 8-10,29 In the present study, chemical whitening agents did not seem to provide an additional benefit to the abrasive effect in the evaluated toothpastes, because the color changes in those groups were no different from those achieved by ordinary toothpaste. Because 1 of the tested whitening toothpastes contains both polyphosphates and hydrogen peroxide in its formula (Colgate Optic White), it was expected that it would be superior to the others. However, even in that toothpaste, the abrasive action may have outperformed its chemical action. This finding corroborates those obtained in a previous study and may reflect any or all of the following factors: Hydrogen peroxide is unstable in such formulas; this compound is in low concentration in the toothpaste (approximately 1% by weight); and the action time is inherently low during brushing. 7,12 The increase in lightness of color and reduction in the colors red and yellow in the samples after brushing may have occurred because the toothpastes removed extrinsic stains deposited on the enamel surface. 4 Additionally, the ΔE* showed a significant difference between the poststaining and postbrushing conditions, probably because at the poststaining timepoint there was stain deposition on the teeth that induced a color change, while at the postbrushing stage the extrinsic stain was removed. 4,15 Although there was no significant difference between whitening and ordinary toothpastes, a lower ΔE* was observed in the distilled water control group. This may be ascribed to the fact that efficacy of toothpaste depends not only on its components but also on the mechanical action of brushing, which promotes abrasion. 7 Such an observation indicates that toothbrushing without toothpaste promotes less effective stain removal. 30 By revealing that extrinsic stain removal achieved by whitening toothpastes was equivalent to that realized by an ordinary toothpaste, this study provides grounds for the selection of oral hygiene products. However, further studies are necessary to verify the effectiveness of such products in the removal of stains from other sources, to investigate their ability to prevent stain deposition, and to determine their efficacy in removing preexisting stains. Conclusion Toothpastes containing chemical whitening agents did not outperform an ordinary toothpaste in removing extrinsic stains in vitro. Author information Dr. Soares is a student, Sao Leopoldo Mandic School of Dentistry, Campinas, Brazil. Drs. Amaral, Franca, Basting, and Turssi are professors, Department of Restorative Dentistry, Sao Leopoldo Mandic Institute and Dental Research Center, Campinas, Brazil. Dr. Mesquita is a professor, Department of Prosthodontics and Periodontics, Piracicaba School of Dentistry, State University of Campinas, Piracicaba, Brazil. Disclaimer The authors have no financial, economic, commercial, or professional interests related to topics presented in this article. References 1. Watts A, Addy M. Tooth discolouration and staining: a review of the literature. Br Dent J. 2001;190(6): Addy M, Moran J. Mechanisms of stain formation on teeth, in particular associated with metal ions and antiseptics. Adv Dent Res. 1995;9(4): Moreira AD, Mattos CT, de Araujo MV, Ruellas AC, Sant anna EF. Chromatic analysis of teeth exposed to different mouthrinses. J Dent. 2013;41(Suppl 5):e24- e Joiner A. Whitening toothpastes: a review of the literature. 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5 Published with permission of the Academy of General Dentistry. Copyright 2015 by the Academy of General Dentistry. All rights reserved. For printed and electronic reprints of this article for distribution, please contact 23. Addy M, Moran J. Extrinsic tooth discoloration by metals and chlorhexidine, II: clinical staining produced by chlorhexidine, iron and tea. Br Dent J. 1985;159(10): Adeyemi A, Pender N, Higham SM. The susceptibility of bleached enamel to staining as measured by quantitative light-induced fluorescence (QLF). Int Dent J. 2008; 58(4): Leard A, Addy M. The propensity of different brands of tea and coffee to cause staining associated with chlorhexidine. J Clin Periodontol. 1997;24(2): Schemehorn BR, Moore MH, Putt MS. Abrasion, polishing, and stain removal characteristics of various commercial dentifrices in vitro. J Clin Dent. 2011; 22(1): Sabrah AHA, Lippert F, Kelly AB, Hara AT. Comparison between radiotracer and surface profile methods for the determination of dentifrice abrasivity. Wear. 2013; 306(1): van Loveren C, Duckworth RM. Anti-calculus and whitening toothpastes. Monogr Oral Sci. 2013;23: Joiner A, Pickles MJ, Matheson JR, Weader E, Noblet L, Huntington E. Whitening toothpastes: effects on tooth stain and enamel. Int Dent J. 2002;52(S5): Lima JP, Melo MA, Passos VF, Braga CL, Rodrigues LK, Santiago SL. Dentin erosion by whitening mouthwash associated to toothbrushing abrasion: a focus variation 3D scanning microscopy study. Microsc Res Tech. 2013;76(9): Manufacturers Adobe Systems, Inc., San Jose, CA , Buehler, Lake Bluff, IL , Colgate-Palmolive Company, New York, NY , Elquip, Sao Carlos, Brazil , IBM Corporation, Armonk, NY , Kota, Sao Paulo, Brazil , Plaster Industria e Comercio, Ltda., Caxias do Sul, Brazil , Procter & Gamble, Cincinnati, OH , Rioquimica Industria Farmaceutica, Sao Jose do Rio Preto, Brazil , Sigma Corporation of America, Ronkonkoma, NY , Sony Corporation of America, New York, NY , e28 November/December 2015 General Dentistry