RESEARCH AND EDUCATION Supported by aProfessor, D bPostgraduat cGraduate stu dPostgraduat eProfessor, D fProfessor, D 430 Effect of different acidic solutions on the optical behavior of lithium disilicate ceramics Daniela Micheline dos Santos, MS, PhD,a Emily Vivianne Freitas da Silva, DDS, MS,b Denis Watanabe, DDS,c Sandro Basso Bitencourt, DDS,d Aimée Maria Guiotti, MS, PhD,e and Marcelo Coelho Goiato, MS, PhDf ABSTRACT Statement of problem. The stability of the optical characteristics of dental ceramics is essential. Degradation of these materials resulting from pH or temperature alterations in the oral cavity can lead to treatment failure. Purpose. The purpose of this in vitro study was to evaluate the color change (DE), the L* coordi- nate, the translucency parameter, and the contrast ratio of lithium disilicate ceramic exposed to commonly used and potentially colorant solutions. Material and methods. Fifty lithium disilicate specimens were prepared and divided into 5 groups according to the immersion solution (artificial saliva, orange juice, cola, coffee, and red wine). Immersions in acidic beverages were alternated in a thermocycler with artificial saliva. The control group was immersed in artificial saliva at 37�C throughout the immersion period. After 168 hours of immersion, the color parameters were assessed with a spectrophotometer and calculated using the because system on 2 backgrounds (black and white) and in 2 time periods, before thermocycling and after thermocycling. Data were submitted to analysis of variance followed by the Tukey honest significant difference test (a=.05). Results. Greater color change (DE) and lower L* coordinate values were observed after immersion in orange juice and cola. Regarding the translucency parameter and contrast ratio, the immersion in coffee resulted in greater opacity and lower translucency of the material. Conclusions. Alterations in the color stainability, the L* coordinate values, the translucency parameter, and the contrast ratio of the lithium disilicate ceramic were observed, according to the acidic solutions tested. (J Prosthet Dent 2017;118:430-436) Dental esthetics have become increasingly important in con- temporary society.1,2 The de- mand for ceramic restorations has increased because of their enhanced esthetics and greater durability than other restor- ative materials.3-5 Development of dental ceramics has been promoted by overcoming clinically undesirable characteristic such as wear of antagonist teeth and restorations and difficulty controlling optical properties.4 Creating restorations that mimic natural tooth appear- ance is one of the major clin- ical challenges.6-8 The ceramic should reproduce natural tooth characteristics, including color, surface texture, and translucency, to achieve esthetic levels that accurately match the natural tooth structure.6,7,9 The fabrication technique, method of application, and number of firing cycles affect ceramic properties.4 The pressing technique promotes lower shrinkage during the manufacturing Scholarships for Initiation into Science (PIBIC)/National Council for Scien epartment of Dental Materials and Prosthodontics, Sao Paulo State Univer e student, Department of Dental Materials and Prosthodontics, Sao Paulo dent, Department of Dental Materials and Prosthodontics, Sao Paulo Stat e student, Department of Dental Materials and Prosthodontics, Sao Paulo epartment of Dental Materials and Prosthodontics, Sao Paulo State Univer epartment of Dental Materials and Prosthodontics, Sao Paulo State Univer process, giving less surface porosity and higher resistance than with conventional ceramics.10 This fabrication method is used for lithium disilicate ceramic, which has a unique crystalline phase (with 70% lithium disilicate crystals), providing a natural reflection of light on the tific and Technological Development (CNPq) scholarship 29651 to D.W. sity (UNESP), School of Dentistry, Aracatuba, Sao Paulo, Brazil. State University (UNESP), School of Dentistry, Aracatuba, Sao Paulo, Brazil. e University (UNESP), School of Dentistry, Aracatuba, Sao Paulo, Brazil. State University (UNESP), School of Dentistry, Aracatuba, Sao Paulo, Brazil. sity (UNESP), School of Dentistry, Aracatuba, Sao Paulo, Brazil. sity (UNESP), School of Dentistry, Aracatuba, Sao Paulo, Brazil. THE JOURNAL OF PROSTHETIC DENTISTRY http://crossmark.crossref.org/dialog/?doi=10.1016/j.prosdent.2016.10.023&domain=pdf Clinical Implications Commonly used acidic beverages influence the optical behavior of lithium disilicate ceramics. Greater color change was observed after immersion in orange juice and cola, and greater opacity and lower translucency were observed after immersion in coffee. September 2017 431 ceramic surface.11,12 Ceramics are exposed to a surface degradation process, which occurs when they are exposed to aqueous solutions and/or pH alterations.13-17 Furthermore, this process can be intensified by differ- ences in temperature13,15 and has undesirable conse- quences for the restoration, such as microbial plaque accumulation and restorations with alterations in color and appearance.14,18 Many in vitro studies have shown that commonly used beverages such as coffee, tea, red wine, cola, and fruit juice can cause significant changes in the color of restorative materials.19-31 Maintenance of ceramic characteristics is essential from an esthetic perspective, because restorations that mimic only the shape and color of adjacent teeth are easily detected and can lead to treatment failure.6,32-34 Color analysis by digital methods allows color measurement of restorative materials without the subjectivity of human analysis.32,35-37 The CIELab system has the advantage of expressing data that can be related to visual perception, which has clinical significance.12,38,39 However, Della Bona et al4 reported that this system is unable to measure the opacity and translucency of the material. These optical phenomena are essential for color perception. Therefore, other methods, such as contrast ratio (CR) and trans- lucency parameter (TP), are used to evaluate the translucency and opacity of esthetic materials.6,40-43 Translucency parameter values are defined by the differ- ence in color values obtained between the light reflected by a material with a defined thickness, positioned on 2 different backgrounds of black and white.6,44,45 The CR values relate to the translucency of the material, ranging from 0.0 (transparent) to 1.0 (totally opaque).6 Studies of the influence of acidic diets on dental ceramics are rare.46 Thus, this in vitro study evaluated the color change (DE), the L* coordinate, the TP value, and the CR of lithium disilicate ceramic exposed to commonly used and potentially colorant solutions. The null hy- pothesis was that the proposed solutions associated with temperature changes are not able to alter the optical properties of the tested ceramic. MATERIAL AND METHODS Fifty highly translucent lithium disilicate specimens (IPS e.max Press Impulse; Ivoclar Vivadent AG) (color O1) dos Santos et al were prepared using the lost-wax technique from auto- polymerized acrylic resin disks (Duralay; Polidental).3 The resin disks were obtained from a metal, circular pattern (10-mm diameter, 3-mm thickness) and polished with metallographic abrasive papers (240, 400, 800, and 1200-grit; Buehler Ltd) in an automated polishing ma- chine (Aropol-2V; Arotec). The acrylic resin disks were placed on a coating ring with the investment (IPS PressVEST; Ivoclar Vivadent AG), and the ceramic was injected through sprues at 915�C to 920�C, after which a ring gauge (IPS Ring Gauge; Ivoclar Vivadent AG) was placed over the ring. After solidification, the gauge and base rings were removed, and irregularities on the inferior part of the ring were removed. The investment ring was then inserted into a preheated furnace (EP 5000; Ivoclar Vivadent AG) for 45 minutes at 850�C to eliminate the acrylic resin. Subsequently, the pressing channel was filled with a ceramic ingot, and the ceramic was injected by using a plunger (IPS e.max Alox Plunger; Ivoclar Vivadent AG). The entire assembly was carried to the furnace to start the injection cycle for 60 minutes. After cooling, the investment material was removed using glass beads at 200 kPa pressure. The lithium disilicate specimens were then airborne-particle abraded with aluminum oxide (Al2O3; Bio-Art) at 200 kPa, and the sprues were removed with a diamond rotary instrument at low speed and with light pressure to avoid overheating. The specimen thickness was measured with calipers (500-171-20B; Mitutoyo) before the cleaning proced- ure.47 Subsequently, the specimens were cleaned in an ultrasonic bath with distilled water to remove surface impurities. The glaze firing was performed afterward, according to the manufacturer’s recommendations. The specimens were divided according to the im- mersion solutions into 5 groups (n=10): group S (artificial saliva), group OJ (orange juice), group CC (cola [Coca- Cola]), group C (coffee), and group RW (red wine) (Table 1). The specimens from group S were stored in artificial saliva in an incubator at 37�C for 168 hours. The specimens from groups OJ, CC, C, and RW were immersed in their respective acidic beverages and also alternated with immersion in artificial saliva in a ther- mocycler (MSCT-3; Convel), because acidic drink con- sumption is not continuous but interspersed with exposure to saliva.49 Specimens were stored in deionized water in a digital incubator (CE-210; CIENLAB) at 37 ±1�C for 24 hours before the initial readings and immersion protocol.19 For the thermocycling process, the acidic beverages were stored in a container positioned inside the incubator. Another container in the incubator had artificial saliva stored at 37�C. The temperature of the beverages was 5�C or 55�C, as listed in Table 1.19 A total of 10 080 cycles of 1 minute each were performed. This cycle scheme THE JOURNAL OF PROSTHETIC DENTISTRY 6 4 5 3 2 1C o lo r C h a n g e ( Δ E ) 0 S OJ A C B C C CC C RW Acidic Solutions Figure 1. Mean values of color change (DE) on black background of ceramic for different immersion solutions used. Different uppercase letters denote statistically significant differences (P<.05; Tukey honest significant difference test). C, coffee; CC, Coca-Cola; OJ, orange juice; RW, red wine; S, artificial saliva. Table 1. Immersion solutions used Immersion Solution Manufacturer Chemical Composition pH Immersion Temperature19,48 Artificial saliva Sigma-Aldrich Brazil Ltda KCl (0.4 g L−1), NaCl (0.4 g L−1), CaCl2_2H2O (0.906 g L−1), NaH2PO4_2H2O (0.690 g L−1), Na2S_9H2O (0.005 g L−1), and urea (1 g L−1) 6.5 37�C Orange juice Coca-Cola Orange juice, water, sugar, orange pulp, natural flavors, antioxidant ascorbic acid, and citric acid 3.52 5�C Cola Coca-Cola Carbonated water, sugar, cola nut extract, yellow dye IV, acidulant INS 338, and natural flavors 2.49 5�C Coffee Sara Lee Cafes do Brazil Ltda Roasted and ground coffee 5.35 55�C Red wine Jose Maria da Fonseca Red grape varieties, conservative INS 220, sulfuric acid, 12.7% 3.58 5�C 8 4 7 6 5 3 2 1C o lo r C h a n g e ( Δ E ) 0 S OJ A C B C BC CC C RW Acidic Solutions Figure 2. Mean values of color change (DE) on white background of ceramic for different immersion solutions used. Different uppercase letters denote statistically significant differences (P<.05; Tukey honest significant difference test). C, coffee; CC, Coca-Cola; OJ, orange juice; RW, red wine; S, artificial saliva. 432 Volume 118 Issue 3 corresponded to 168 hours, which simulated 22 years of clinical performance of a ceramic restoration.14,50-52 After thermocycling, the specimens were washed in running water and dried in absorbent paper before the color measurements were made.53 The color parameters were assessed using a spectro- photometer (UV-2450; Shimadzu) on 2 backgrounds (black and white).6 The measurements were made using a D65 illuminant at a 2-degree angle of observation, a wavelength range of 380 to 780 nm, and a 10-mm- diameter aperture. One reading per specimen was made in 2 time periods, before and after thermocycling. The color changes (DE) were calculated using the CIELab system, as established by the Commission Internationale de I’Eclairage (CIE).38,54 This system calculates the color variation between 2 points in a 3-dimensional (3D) color space.38,44,45,54 The L* coordinate values on white and black backgrounds were also evaluated. The translucency of a material can be quantitatively described through the calculation of the CR and TP values, each involving an optical measurement per- formed on a specific thickness.6,41 The specimens were placed on black and white backgrounds, and the values were recorded using CIELab coordinates for the CR and TP calculations.6 Data were submitted to 1-way analysis of variance (ANOVA) for the color change (DE) and THE JOURNAL OF PROSTHETIC DENTISTRY 2-way repeated-measures ANOVA for the L* coordinate, CR, and TP values. The Tukey honest significant differ- ence test (a=.05) was used for all analyses. RESULTS The type of immersion solution influenced the color change (DE) of the lithium disilicate ceramic on black (df=4; F=68.276; P<.001 by ANOVA) and white (df=4; F=74.254; P<.001 by ANOVA) backgrounds. Greater color change (DE) was observed after immersion in orange juice (4.51 on black and 6.58 on white back- grounds), followed by cola (2.67 on black and 2.95 on white backgrounds), with statistically significant differ- ences from the other groups (Figs. 1, 2). The L* coordinate of the lithium disilicate ceramic was affected by the immersion solution on the black back- ground (P<.001) (Table 2) and by the interaction between the type of solution and period of analysis on the white background (P<.001) (Table 3). After thermocycling, statistically lower L* coordinate values were found for cola (47.64 on black and 65.44 on white backgrounds), followed by orange juice (52.71 on black and 70.65 on white backgrounds) (Figs. 3, 4). The interaction between the type of immersion solution and the period of analysis (before and after dos Santos et al Table 2. Two-way repeated-measures ANOVA of ceramic for L* coordinate on black background for different immersion solutions Variation Factor df Sum of Squares Mean of Squares F P Solution 4 1708.911 427.228 52.269 <.001 Between subjects 45 367.813 8.174 Period 1 3.644 3.644 1.236 .272 Solution×period 4 11.687 2.922 0.991 .422 Within subjects 45 132.682 2.948 P<.05 denotes statistically significant difference. Table 3. Two-way repeated-measures ANOVA of ceramic for L* coordinate on white background for different immersion solutions Variation Factor df Sum of Squares Mean of Squares F P Solution 4 637.210 159.303 73.558 <.001 Between subjects 45 97.456 2.166 Period 1 39.464 39.464 27.153 <.001 Solution×period 4 105.781 26.445 18.196 <.001 Within subjects 45 65.402 1.453 P<.05 denotes statistically significant difference. 70 50 40 60 30 20 10 L C o o rd in a te 0 S OJ C AB D A B CC C RW Acidic Solutions Figure 3. Mean values of L coordinate values on black background of ceramic after immersion in different immersion solutions. Different up- percase letters denote statistically significant differences (P<.05; Tukey honest significant difference test). C, coffee; CC, Coca-Cola; OJ, orange juice; RW, red wine; S, artificial saliva. 80 50 40 60 70 30 20 10 L C o o rd in a te 0 S OJ C A D AB B CC C RW Acidic Solutions Figure 4. Mean values of L coordinate values on white background of ceramic after immersion in different immersion solutions. Different uppercase letters denote statistically significant differences (P<.05; Tukey honest significant difference test). C, coffee; CC, Coca-Cola; OJ, orange juice; RW, red wine; S, artificial saliva. Table 4. Two-way repeated-measures ANOVA of ceramic for translucency parameter for different immersion solutions Variation Factor df Sum of Squares Mean of Squares F P Solution 4 461.614 115.403 19.328 <.001 Between subjects 45 268.684 5.971 Period 1 7.415 7.415 3.207 .080 Solution×period 4 78.269 19.567 8.464 <.001 Within subjects 45 104.034 2.312 P<.05 denotes statistically significant difference. 25 15 20 10 5 T ra n sl u ce n c y P a ra m e te r 0 S OJ A B A C AB CC C RW Acidic Solutions Figure 5. Mean values of translucency parameter of ceramic after immersion in different solutions. Different uppercase letters denote statistically significant differences (P<.05; Tukey honest significant difference test). C, coffee; CC, Coca-Cola; OJ, orange juice; RW, red wine; S, artificial saliva. Table 5. Two-way repeated-measures ANOVA of ceramic for contrast ratio for different immersion solutions Variation Factor df Sum of Squares Mean of Squares F P Solution 4 0.375 0.094 24.103 <.001 Between subjects 45 0.175 0.004 Period 1 0.000064 0.000064 0.044 .834 Solution×period 4 0.22 0.006 3.832 .009 Within subjects 45 0.065 0.001 P<.05 denotes statistically significant difference. September 2017 433 thermocycling) significantly affected the results (P<.001) (Table 4) in regard to the ceramic TP. The TP value was lower for specimens immersed in coffee, with a statisti- cally significant difference from those values of the other solutions (Fig. 5). The interaction between the type of immersion solution and the period of analysis significantly affected the results (P=.009) (Table 5) in regard to the CR of the ceramic. The immersion in coffee resulted in greater opacity of the material (Fig. 6). DISCUSSION The null hypothesis that the tested solutions were not able to promote alterations in the optical properties of the tested ceramic was rejected. Color changes and alter- ations of the TP and CR values were observed. The dos Santos et al THE JOURNAL OF PROSTHETIC DENTISTRY 0.7 0.4 0.3 0.5 0.6 0.2 0.1 C o n tr a st R a ti o 0 S OJ C B C A B CC C RW Acidic Solutions Figure 6. Mean values of contrast ratio of ceramic after immersion in different solutions. Different uppercase letters denote statistically significant differences (P<.05; Tukey honest significant difference test). C, coffee; CC, Coca-Cola; OJ, orange juice; RW, red wine; S, artificial saliva. 434 Volume 118 Issue 3 immersions in orange juice and cola were responsible for greater color change (DE) and lower L* coordinate values on the black and white backgrounds. The immersion in coffee resulted in greater opacity and lower translucency of the material in regard to the TP and CR. The CIELab system, used for the analysis of color change (DE), quantifies color changes through 3D co- ordinates. The L* parameter evaluates the luminosity (scale, 0-100, where 0 represents black and 100 represents white), the a* coordinate measures the amount of redness (positive values) and greenness (negative values), and the b* coordinate measures the amount of yellowness (posi- tive values) and blueness (negative values).6,38,54 This system was chosen because it identifies small color dif- ferences among specimens and has been widely used.27,39 Two backgrounds (black and white) were used to analyze the optical properties. Because the black background is more absorbent, it is used to simulate the clinical situation of anterior teeth, whereas the white background is used for posterior teeth.27 Although statistically significant differences were observed for orange juice and cola when they were compared with other groups, only the immersion in orange juice resulted in DE values greater than 3.3 (4.51 on black and 6.58 on white backgrounds); a color change perceptible to the human eye and clinically unaccept- able.5,27,31 According to Hipólito et al,38 the pH of the solution in which the specimen is immersed influences its color change. Although the cola drink presented the lowest pH among the tested solutions, which may damage the surface integrity of the material, a color change perceptible to the human eye was not observed, possibly because of the low amount of yellow colorant in its composition.26,30 Furthermore, while the cola drink contains carbonic and phosphoric acids in its composi- tion, the orange juice contains citric acid, which may explain the differences found according to Catelan et al.26 Damage to the surface integrity of the ceramic is associated with exposure to a low pH condition, which THE JOURNAL OF PROSTHETIC DENTISTRY results in the dissolution of the silica in its composition and in the loss of alkaline ions.17 As a result, a surface degradation occurs and may result in a higher penetra- tion of colorants and, consequently, greater discoloration of the material.30 Therefore, the optical change observed is not an intrinsic color change of the ceramic but a result of its surface degradation and extrinsic color additions. The value of the color change (DE) is considered the gold standard for measurement analysis, but only the CIELab coordinates are considered without other criteria such as translucency, opalescence, fluorescence, bright- ness, surface texture, and shape6,12 being evaluated. The present study included the evaluation of the TP and the contrast ratio for a more complete chromatic analysis of the material; the greater the value of the TP, the greater the translucency of the material. Lithium disilicate ceramic has excellent translucency because of a high content of lithium disilicate crystals11,12 This advantage must be preserved for the longevity of the rehabilitation. In the present in vitro study, immersion in coffee resulted in lowering the TP of the material. Concerning the CR values, the greatest opacity of the ceramic was found after thermocycling with immersion in coffee. Coffee contains yellow colorants with lower polarity, which result in a discoloration of the material caused by adsorption and absorption of colorants.22,30 This beverage was the only one submitted to higher temperatures (55�C) to simulate its daily use, a factor that may have influenced the greater opacity and lower translucency of the ceramic. Bagis and Turgut39 evaluated the optical properties of different ceramic systems, including lithium disilicate ceramics before and after accelerated aging. The authors observed that the specimens became more opaque, darker, reddish, and yellowish after accelerated aging, using ultraviolet light and water spray. It was performed for 300 hours, which simulated 1 year of clinical use. However, this alteration was not clinically perceptible. Similarly, Dikicier et al34 found darkening of the lithium disilicate ceramics after aging for 200 hours also clinically undetectable. Most of the studies evaluating the optical properties of restorative materials continuously immersed the specimens in colorant beverages, complicating the cor- relation between the study and what is found clinically, because exposure of the restoration to such beverages is alternated with periods of exposure to saliva. Addition- ally, studies should include cycling of the materials in solutions at different temperatures, simulating the labo- ratory conditions of the oral environment more faith- fully.18,19 Furthermore, in the present study, the temperature usually used for the intake of the beverage was replicated, with a higher temperature for the coffee and lower temperatures for the cola, orange juice, and red wine. This is because temperature differences can dos Santos et al September 2017 435 interfere with color change because they influence the surface porosity of the material.3 The present study has some limitations, and other methodologies have been reported for optical property analysis. An alternative method of measuring the color of the specimens is the Kubelka-Munk theory.55 This methodology is a reflectance theory for layers on a backing and is a mathematical model which describes the reflectance resulting from 2-flux radiation transfer in a homogenous and uniform medium on an opaque backing. Through this method, the reflectance and transmittance of the specimen can be evaluated.55-57 The results of the present in vitro study are of clinical relevance because they provide information related to the effect of acidic solutions on the optical properties of lithium disilicate ceramics. Patients using these restora- tions should avoid regular consumption of orange juice, cola, and coffee, aiming for less stainability of the optical properties of this material. However, because it is an in vitro study, randomized clinical trials are necessary for long-term evaluation of the optical properties of lithium disilicate ceramic. CONCLUSIONS From the findings of this in vitro study, the following conclusions were drawn: 1. Immersion in orange juice and cola resulted in greater color changes (DE) and lower L* coordinate values. 2. Immersion in coffee resulted in greater opacity and lower translucency of the material. REFERENCES 1. Motro PF, Kursoglu P, Kazazoglu E. Effects of different surface treatments on stainability of ceramics. J Prosthet Dent 2012;108:231-7. 2. Wright MD, Masri R, Driscoll CF, Romberg E, Thompson GA, Runyan DA. Comparison of three systems for the polishing of an ultra-low fusing dental porcelain. J Prosthet Dent 2004;92:486-90. 3. dos Santos DM, da Silva EV, Vechiato-Filho AJ, Cesar PF, Rangel EC, da Cruz NC, et al. Aging effect of atmospheric air on lithium disilicate ceramic after nonthermal plasma treatment. J Prosthet Dent 2016;115:780-7. 4. Della Bona A. Bonding to ceramics: scientific evidences for clinical dentistry. 1st ed. Sao Paulo: Artes Médicas; 2009. p. 91-132. 5. Sarac D, Sarac YS, Yuzbasioglu E, Bal S. The effects of porcelain polishing systems on the color and surface texture of feldspathic porcelain. J Prosthet Dent 2006;96:122-8. 6. Nogueira AD, Della Bona A. The effect of a coupling medium on color and translucency of CAD-CAM ceramics. J Dent 2013;41:e18-23. 7. Son HJ, Kim WC, Jun SH, Kim YS, Ju SW, Ahn JS. Influence of dentin porcelain thickness on layered all-ceramic restoration color. J Dent 2010;38: e71-7. 8. Brewer JD, Wee A, Seghi R. Advances in color matching. Dent Clin North Am 2004;48:341-58. 9. Harianawala HH, Kheur MG, Apte SK, Kale BB, Sethi TS, Kheur SM. Comparative analysis of transmittance for different types of commercially available zirconia and lithium disilicate materials. J Adv Prosthodont 2014;6: 456-61. 10. Albakry M, Guazzato M, Swain MV. Fracture toughness and hardness evalu- ation on three pressable all-ceramic dental materials. J Dent 2003;31:181-8. 11. Culp L, McLaren EA. Lithium disilicate: the restorative material of multiple options. Compend Contin Educ Dent 2010;31. 716-20;722,724-5. dos Santos et al 12. Ozturk O, Uludag B, Usumez A, Sahin V, Celik G. The effect of ceramic thickness and number of firings on the color of two all-ceramic systems. J Prosthet Dent 2008;100:99-106. 13. Esquivel-Upshaw JF, Dieng FY, Clark AE, Neal D, Anusavice KJ. Surface degradation of dental ceramics as a function of environmental pH. J Dent Res 2013;92:467-71. 14. Kukiattrakoon B, Hengtrakool C, Kedjarune-Leggat U. The effect of acidic agents on surface ion leaching and surface characteristics of dental porcelains. J Prosthet Dent 2010;103:148-62. 15. Kukiattrakoon B, Junpoom P, Hengtrakool C. Vicker’s microhardness and energy dispersive x-ray analysis of fluoride-leucite and fluorapatite ceramics cyclically immersed in acid agents. J Oral Sci 2009;51:443-50. 16. Swain MV. Impact of oral fluids on dental ceramics: what is the clinical relevance. Dent Mater 2014;30:33-42. 17. Ccahuana VZ, Ozcan M, Mesquita AM, Nishioka RS, Kimpara ET, Bottino MA. Surface degradation of glass ceramics after exposure to acidu- lated phosphate fluoride. J Appl Oral Sci 2010;18:155-65. 18. Minami H, Hori S, Kurashige H, Murahara S, Muraguchi K, Minesaki Y, et al. Effects of thermal cycling on surface texture of restorative composite mate- rials. Dent Mater J 2007;26:316-22. 19. Ren YF, Feng L, Serban D, Malmstrom HS. Effects of common beverage colorants on color stability of dental composite resins: the utility of a ther- mocycling stain challenge model in vitro. J Dent 2012;40:48-56. 20. Stober T, Gilde H, Lenz P. Color stability of highly filled composite resin materials for facings. Dent Mater 2001;17:87-94. 21. Guler AU, Yilmaz F, Kulunk T, Guler E, Kurt S. Effects of different drinks on stainability of resin composite provisional restorative materials. J Prosthet Dent 2005;94:118-24. 22. Fujita M, Kawakami S, Noda M, Sano H. Color change of newly developed esthetic restorative material immersed in food-simulating solutions. Dent Mater J 2006;25:352-9. 23. Ashcroft AT, Cox TF, Joiner A, Laucello M, Philpotts CJ, Spradbery PS, et al. Evaluation of a new silica whitening toothpaste containing blue covarine on the colour of anterior restoration materials in vitro. J Dent 2008;36:26-31. 24. Tunc ES, Bayrak S, Guler AU, Tuloglu N. The effects of children’s drinks on the color stability of various restorative materials. J Clin Pediatr Dent 2009;34: 147-50. 25. Fontes ST, Fernandez MR, de Moura CM, Meireles SS. Color stability of a nanofill composite: effect of different immersion media. J Appl Oral Sci 2009;17:388-91. 26. Catelan A, Briso AL, Sundfeld RH, Goiato MC, dos Santos PH. Color stability of sealed composite resin restorative materials after ultraviolet artificial aging and immersion in staining solutions. J Prosthet Dent 2011;105:236-41. 27. Ardu S, Braut V, Gutemberg D, Krejci I, Dietschi D, Feilzer AJ. A long-term laboratory test on staining susceptibility of esthetic composite resin materials. Quintessence Int 2010;41:695-702. 28. Mohan M, Shey Z, Vaidyanathan J, Vaidyanathan TK, Munisamy S, Janal M. Color changes of restorative materials exposed in vitro to cola beverage. Pediatr Dent 2008;30:309-16. 29. Domingos PA, Garcia PP, Oliveira AL, Palma-Dibb RG. Composite resin color stability: influence of light sources and immersion media. J Appl Oral Sci 2011;19:204-11. 30. Bagheri R, Burrow MF, Tyas M. Influence of food-simulating solutions and surface finish on susceptibility to staining of aesthetic restorative materials. J Dent 2005;33:389-98. 31. Villalta P, Lu H, Okte Z, Garcia-Godoy F, Powers JM. Effects of staining and bleaching on color change of dental composite resins. J Prosthet Dent 2006;95:137-42. 32. Assunção WG, Barão VA, Pita MS, Goiato MC. Effect of polymerization methods and thermal cycling on color stability of acrylic resin denture teeth. J Prosthet Dent 2009;102:385-92. 33. ten Bosch JJ, Coops JC. Tooth color and reflectance as related to light scat- tering and enamel hardness. J Dent Res 1995;74:374-80. 34. Dikicier S, Ayyildiz S, Ozen J, Sipahi C. Effect of varying core thicknesses and artificial aging on the color difference of different all-ceramic materials. Acta Odontol Scand 2014;72:623-9. 35. Anusavice KJ, Shen C, Rawls HR. Phillips’ science of dental materials. 12th ed. St. Louis: Elsevier; 2012. p. 38. 36. Ergun G, Mutlu-Sagesen L, Ozkan Y, Demirel E. In vitro color stability of provisional crown and bridge restoration materials. Dent Mater J 2005;24: 342-50. 37. Turgut S, Bagis B. Colour stability of laminate veneers: an in vitro study. J Dent 2011;39:e57-64. 38. Hipólito AC, Barão VA, Faverani LP, Ferreira MB, Assunção WG. Color degradation of acrylic resin denture teeth as a function of liquid diet: ultraviolet-visible reflection analysis. J Biomed Opt 2013;18:105005. 39. Bagis B, Turgut S. Optical properties of current ceramics systems for laminate veneers. J Dent 2013;41:e24-30. 40. Li Q, Yu H, Wang YN. Spectrophotometric evaluation of the optical influence of core build-up composites on all-ceramic materials. Dent Mater 2009;25: 158-65. THE JOURNAL OF PROSTHETIC DENTISTRY http://refhub.elsevier.com/S0022-3913(16)30604-7/sref1 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref1 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref2 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref2 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref2 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref3 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref3 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref3 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref4 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref4 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref5 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref5 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref5 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref6 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref6 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref7 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref7 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref7 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref8 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref8 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref9 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref9 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref9 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref9 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref10 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref10 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref11 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref11 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref12 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref12 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref12 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref13 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref13 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref13 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref14 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref14 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref14 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref15 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref15 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref15 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref16 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref16 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref17 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref17 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref17 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref18 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref18 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref18 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref19 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref19 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref19 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref20 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref20 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref20 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref21 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref21 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref21 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref22 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref22 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref22 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref23 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref23 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref23 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref24 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref24 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref24 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref25 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref25 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref25 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref25 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref26 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref26 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref26 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref27 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref27 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref27 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref28 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref28 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref28 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref29 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref29 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref29 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref30 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref30 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref30 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref31 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref31 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref31 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref32 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref32 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref32 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref33 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref33 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref34 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref34 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref34 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref35 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref35 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref36 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref36 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref36 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref37 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref37 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref38 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref38 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref38 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref39 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref39 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref40 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref40 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref40 436 Volume 118 Issue 3 41. Miyagawa Y, Powers JM, O’Brien WJ. Optical properties of direct restorative materials. J Dent Res 1981;60:890-4. 42. Yu B, Ahn J-S, Lee Y-K. Measurement of translucency of tooth enamel and dentin. Acta Odontol Scand 2009;67:57-64. 43. Jeong ID, Bae SY, Kim DY, Kim JH, Kim WC. Translucency of zirconia-based pressable ceramics with different core and veneer thicknesses. J Prosthet Dent 2016;115:768-72. 44. Johnston WM, Ma T, Kienle BH. Translucency parameter of colorants for maxillofacial prostheses. Int J Prosthodont 1995;8:79-86. 45. Hu X, Johnston WM. Translucency estimation for thick pigmented maxillo- facial elastomer. J Dent 2011;39:e2-8. 46. Attin T, Wegehaupt FJ. Impact of erosive conditions on tooth-colored restorative materials. Dent Mater 2014;30:43-9. 47. Hernandes DK, Arrais CA, Lima Ed, Cesar PF, Rodrigues JA. Influence of resin cement shade on the color and translucency of ceramic veneers. J Appl Oral Sci 2016;24:391-6. 48. Faverani LP, Barão VA, Ramalho-Ferreira G, Ferreira MB, Garcia-Júnior IR, Assunção WG. Effect of bleaching agents and soft drink on titanium surface topography. J Biomed Mater Res B Appl Biomater 2014;102:22-30. 49. Turssi CP, Hara AT, de Magalhães CS, Serra MC, Rodrigues AL Jr. Influence of storage regime prior to abrasion on surface topography of restorative materials. J Biomed Mater Res B Appl Biomater 2003;65:227-32. 50. Milleding P, Wennerberg A, Alaeddin S, Karlsson S, Simon E. Surface corrosion of dental ceramics in vitro. Biomaterials 1999;20:733-46. 51. De Backer H, Van Maele G, De Moor N, Van den Berghe L, De Boever J. A 20-year retrospective survival study of fixed partial dentures. Int J Pros- thodont 2006;19:143-53. Access to The Journal of Prosthetic Dentistry This is your subscription account number Full-text access to The Journal of Prosthetic Dentistry Online individual online subscription, please visit The Journal of Pro http://www.journals.elsevierhealth.com/periodicals/ympr/ho and follow the instructions. To activate your account, you wil find on your mailing label (note: the number of digits in your example below in which the subscriber account number has Personal subscriptions to The Journal of Prosthetic Dentistry ferred. Use of The Journal of Prosthetic Dentistry Online is su indicated online. THE JOURNAL OF PROSTHETIC DENTISTRY 52. Näpänkangas R, Raustia A. Twenty-year follow-up of metal-ceramic single crowns: a retrospective study. Int J Prosthodont 2008;21:307-11. 53. Kursoglu P, Karagoz Motro PF, Kazazoglu E. Correlation of surface texture with the stainability of ceramics. J Prosthet Dent 2014;112: 306-13. 54. Commission Internationale de l’Eclairage. Colorimetry. 3rd ed. Vienna: Bureau Central de la CIE; 2004. p. 15. 55. Kubelka P. New contributions to the optics of intensely light scattering materials: Part 1. J Opt Soc Am 1948;38:448-57. 56. Pecho OE, Ghinea R, Ionescu AM, Cardona JC, Della Bona A, Pérez Mdel M. Optical behavior of dental zirconia and dentin analyzed by Kubelka-Munk theory. Dent Mater 2015;31:60-7. 57. Mikhail SS, Azer SS, Johnston WM. Accuracy of Kubelka-Munk reflectance theory for dental resin composite material. Dent Mater 2012;28: 729-35. Corresponding author: Dr Daniela Micheline dos Santos Aracatuba Dental School (UNESP) Department of Dental Materials and Prosthodontics José Bonifácio, 1193 e Vila Mendonca e 16015-050 Aracatuba, Sao Paulo BRAZIL Email: danielamicheline@foa.unesp.br Copyright © 2016 by the Editorial Council for The Journal of Prosthetic Dentistry. Online is reserved for print subscribers! Sample mailing label is available for all print subscribers. To activate your sthetic Dentistry Online. Point your browser to me, follow the prompts to activate online access here, l need your subscriber account number, which you can subscriber account number varies from 6 to 10). See the been circled. Online are for individual use only and may not be trans- bject to agreement to the terms and conditions as dos Santos et al http://refhub.elsevier.com/S0022-3913(16)30604-7/sref41 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref41 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref42 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref42 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref43 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref43 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref43 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref44 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref44 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref45 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref45 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref46 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref46 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref47 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref47 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref47 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref48 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref48 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref48 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref49 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref49 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref49 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref50 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref50 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref51 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref51 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref51 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref52 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref52 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref53 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref53 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref53 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref54 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref54 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref55 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref55 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref56 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref56 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref56 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref57 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref57 http://refhub.elsevier.com/S0022-3913(16)30604-7/sref57 mailto:danielamicheline@foa.unesp.br Effect of different acidic solutions on the optical behavior of lithium disilicate ceramics Material and Methods Results Discussion Conclusions References