RESEARCH ARTICLE
Color Stability Over Time of Three Resin-Based Restorative Materials Stored Dry and in Artificial Saliva JOANA YUMI TERUYA UCHIMURA, DDS, MS*, FRANCIELLE SATO, PhD†, GISELLY BIANCHI, MSc‡, MAURO LUCIANO BAESSO, PhD†, ROSÂNGELA GERITANA SANTANA, PhD§, RENATA CORRÊA PASCOTTO, PhD¶
ABSTRACT Objective: To evaluate the color match of different composite resins relative to Vitapan Classical shade guide tab and their respective manufacturers’ shade guide tabs as a function of time and storage. Materials and Methods: Three enamel shade A2 composite resins were used to fabricate 36 disk-shaped polymerized specimens (12 each), allocated into 2 groups of 6 and stored dry (GD) and in artificial saliva (GS). CIELAB coordinates from shade tabs and resin specimens immediately after polymerization (t0), and 24 hours (t1), 7 (t7), 14 (t14) and 21 (t21) days after polymerization were captured using a colorimeter. Color difference (ΔE00) between composite specimens and the reference tabs was calculated using the CIEDE2000 formula. The results were analyzed with repeated measures ANOVA, Tukey’s HDS post-hoc test, and Student t test (p ≤ 0.05). Results: Color of the three tested composites relative to Vita and their respective tabs significantly changed as a function of time until t14; however, between t14 and t21, no significant differences were found. No differences in color were found relative to storage at t14 and t21. ΔE00 values of specimens at t14 were significantly higher relative to their respective tabs than to Vitapan tab. Conclusions: For all brands color changed up to day 14, when it stabilized, regardless of whether composite specimens had been stored in artificial saliva or simply in a box. Vitapan tab presented a better color match than the manufacturers’ tabs.
CLINICAL SIGNIFICANCE The results found in this study demonstrated that the Vitapan Classical shade guide tab A2 provided a better color match than the respective shade guide tabs A2 supplied by the composite manufacturers. If custom shade tabs are to be made, however, they could be kept in a box and used as shade references from 14 days after being fabricated, when color stabilizes. (J Esthet Restor Dent 26:279–287, 2014)
INTRODUCTION Because of its natural and pleasing appearance, composite resins have been widely used in the restorative dentistry to provide for the increasing
demand for an esthetic dentition.1,2 However, one of the major sources of patient dissatisfaction with restorative treatments with composite resins concerns the visible differences in color between teeth and restorations.3 Achieving an optimal tooth/composite resin restoration
*Resident, Department of Dentistry, State University of Maringá, Maringá, Paraná, Brazil † Associate Professor, Department of Physics, State University of Maringá, Maringá, Paraná, Brazil ‡ PhD Applicant, Department of Physics, State University of Maringá, Maringá, Paraná, Brazil § Associate Professor, Department of Statistics, State University of Maringá, Maringá, Paraná, Brazil ¶ Associate Professor, Department of Dentistry, State University of Maringá, Maringá, Paraná, Brazil
© 2014 Wiley Periodicals, Inc.
DOI 10.1111/jerd.12106
Journal of Esthetic and Restorative Dentistry
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color match represents a challenge, especially in the anterior teeth, where even small shade discrepancies can represent an esthetical concern for highly demanding patients.4 Composite resin manufacturers generally use Vitapan Classical shade guide tabs (VITA Zahnfabrik, Bad Sackingen, Germany) as color references for their own reference shade tabs and composite resins.5 However, shade tabs from different commercially available systems frequently present poor matching compared with target Vitapan Classical tabs.1,6–13 In addition to that, several studies have also been carried out comparing different resin composite systems of the same shade, finding low or even no color correspondence among them.1,14–16 When in its natural environment in the oral cavity, composite resin restorations are in constant contact with moisture. Thus, several studies have been performed to assess the effect of moisture on color change, both in water and artificial saliva. These studies have demonstrated statistically significant differences between baseline and post immersion color values.4,17–20 In addition to immersion, time has also been shown to have a significant influence on color stability.4,18–20 Composite resin specimens stored in water showed the highest degree of color change in the first 24 hours and at 7 days, but after 1 month only minor changes were observed.4,21 As a result, restorative dentists cannot take manufacturers color designations for granted when selecting the right color shade for restorations.2,18 Although color designations have their importance as an initial reference, dentists should understand and apply esthetic as well as technical principles when choosing color of restorative materials.2 Different strategies have been suggested to help dentists with color shade selection before starting the restorative procedure. A piece of unpolymerized resin material can be placed on, or adjacent to the tooth to be restored and polymerized to confirm the selected shade of the esthetic material.2,18 The disadvantage of this approach is that it does not take into account further changes in color that take place because of moisture and time.
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Alternatively, custom-made shade guides could be a viable option because of the possibility of superpositioning different thicknesses of enamel and dentin resins in order to obtain the final color outcome.2 In this case, however, defining when to use and how to store custom-made tabs becomes an important issue. The purpose of this study was to evaluate the color match of different composite resins relative to their corresponding Vitapan Classical shade guide tab and the shade guide tabs supplied by the manufacturers as a function of time and storage (dry or in artificial saliva). The null hypotheses were: (1) color difference of specimens relative to Vitapan tab will not be significantly different from that of specimens relative to their respective manufacturer’s shade tab; and (2) color difference of specimens stored in artificial saliva will not be significantly different from those stored dry.
MATERIALS AND METHODS Specimen Preparation A total of 36 disk-shaped composite resin specimens were fabricated using a metal ring mold measuring 10 mm in diameter × 2 mm thick. Three different commercially available composite resin systems (enamel shade A2) were used in this study: Charisma Opal (Heraeus Kulzer, Hanau, Germany), Filtek Z350 XT (3M ESPE, St. Paul, MN, USA), and Opallis (FGM, Joinville, SC, Brazil). The metal ring was placed onto a glass microscope slide and filled with unpolymerized composite resin, which was then covered with a clear polyethylene terephthalate strip. Another glass slide was then placed onto the strip, and the specimen was light-cured for 40 seconds using a light-emitting diode (LED) polymerizing device (Radii—SDI, Victoria, Australia). A total of 12 specimens were made from each material. Specimens had a smooth surface upon removal from the mold and no further polishing was performed. All specimens were produced with resin coming from the same respective syringe. Polymerized specimens were randomly allocated into two experimental groups. Half of the specimens (six
DOI 10.1111/jerd.12106
© 2014 Wiley Periodicals, Inc.
COLOR STABILITY OF COMPOSITE RESINS Uchimura et al.
specimens per material) were separated to be stored in a box (DG), protected from the light at room temperature, whereas the other half was kept immersed into artificial saliva (SG) inside an incubator at 37°C throughout the experimental period.
polymerization. Three independent measurements were made each time and averaged together to establish the CIELAB color coordinate values.
Color Measurement
CIELAB values were converted into units of CIEDE2000 color notation formula (ΔE00), which was used to calculate color difference as follows:
A Minolta CR-400 reflectance colorimeter (Konica Minolta Sensing, Inc., Osaka Japan) was used to capture CIELAB color coordinates. The colorimeter is designed in a diffusion illumination mode, 0° viewing geometry angle, including specular components. This illumination method illuminates the specimen from all directions using a D65 source with almost completely equal brightness and receives the reflected light vertically from the specimen surface. The colorimeter aperture for light irradiation over the sample surface was 10 mm. The illumination and measurement areas have diameters of 11 and 8 mm, respectively. The light source is a pulsed xenon lamp which is diffused into a diffusion chamber and directed to diffusion plates positioned about 6 mm above the specimen surface. Measurements were conducted against a diffuse white background,22 using the International Commission on Illumination (CIELAB) L* a* b* C* H* color scale, where L* refers to lightness, ranging from zero to 100 (higher number being brighter); a* to green–red coordinate; b* to blue–yellow coordinate; C* to chroma (lower number means lower chroma); H* to hue (e-specific color measured from zero to 360°: 0° is red, 90° yellow, 180° green, and 270° blue).7 The colorimeter was calibrated using the white calibration plate provided by the manufacturer. Color measurements were taken from a Vitapan Classical tab A2. While the tab was held by the handle, the probe of the Minolta CR-400 was placed in the middle-third of the tab. The same procedure was conducted for the shade guide tabs supplied by the manufacturer of each tested material by placing the probe in the central area of the tabs. Color of specimens was measured at five different experimental times: immediately after polymerization (t0); 24 hours (t1); 7 days (t7); 14 days (t14); and 21 days (t21) after
© 2014 Wiley Periodicals, Inc.
DOI 10.1111/jerd.12106
Color Difference
(
) ( 2
) ( ) 2
ΔE00 = ⎡ ΔL ′ k L SL + ΔC ′ kC SC + ΔH ′ k H SH ⎣ 12 + RT ΔC ′ kC SC ) (ΔH ′ k H SH ⎤⎦
(
)
2
where ΔL′, ΔC′, and ΔH′ are the differences in lightness, chroma, and hue for a pair of samples in CIEDE2000, and RT is a function (the so-called rotation function) that accounts for the interaction between chroma and hue differences in the blue region. Weighting functions, SL, SC, SH, adjust the total color difference for variation in the location of the color difference pair in L0, a0, b0 coordinates and the parametric factors, KL, KC, KH, are correction terms for experimental conditions.23 To verify color change as a function of time and storage, color difference (ΔE00) was calculated between the Vitapan Classical A2 tab and specimens in both groups (DG and SG) for each experimental time. The same procedure was conducted with each composite resin tab and their corresponding specimens. The 50:50% acceptability threshold adopted in this study was ΔE00 = 2.23.24
Statistical Analysis Shapiro–Wilk test demonstrated that the data was normally distributed. ΔE00 results were evaluated using the repeated measures analysis of variance (ANOVA) to verify the influence of time, storage, and their interactions for each individual brand of resin separately. Tukey HDS post-hoc test was then applied to verify where differences between groups existed. A comparative analysis between mean color difference (ΔE00) of composite resin specimens established at 14 days after polymerization (t14) relative to the Vita tab
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and their respective manufacturers’ tabs was performed using Student t-test for independent samples. All analyses were performed using Statistical Analysis System (SAS), at a level of significance of 5% (p < 0.05).
RESULTS The CIELAB A2 mean color shade coordinates of Vitapan Classical and Z350, Charisma and Opallis shade guide tabs and their respective composite specimens over time measured with Minolta CR-400 are presented in Table 1.
Mean color difference (ΔE00) between Vitapan Classical A2 tab and specimens, and the composites shade tabs and their respective specimens, as a function of time and storage (DG and SG), are presented in Tables 2 and 3, respectively. Repeated measures ANOVA demonstrated that time had a significant effect over color change of composite specimens of all brands tested (p < 0.0001), regardless of the reference shade tab, with a power of test of 1.00. Storage, on the other hand, proved to have no significant effect over color change for any of the brands tested relative to Vita tab (Z350: p = 0.9251; Charisma: p = 0.066; Opallis: p = 0.0723). Storage, relative to the composites
TABLE 1. CIELAB A2 color shade coordinates of Vitapan Classical tab and Z350, Charisma and Opallis shade guide tabs and their respective composite resins over time measured with Minolta CR-400 L* (SD)
a* (SD)
b* (SD)
C* (SD)
H* (SD)
Vitapan
Tab
77.94 (0.01)
1.65 (0.00)
22.09 (0.00)
22.15 (0.00)
1.49 (0.00)
Z350
Tab
79.72 (0.01)
0.44 (0.01)
14.17 (0.00)
12.76 (0.00)
1.53 (0.00)
t0
78.33 (1.12)
1.01 (0.28)
19.10 (1.49)
19.13 (1.47)
1.51 (0.01)
t1
78.43 (1.21)
1.02 (0.26)
20.69 (1.46)
20.71 (1.46)
1.52 (0.01)
t7
79.79 (1.23)
1.39 (0.11)
22.44 (2.28)
22.48 (2.28)
1.50 (0.00)
t14
81.36 (0.55)
1.96 (0.35)
24.11 (1.02)
24.20 (1.00)
1.48 (0.01)
t21
81.69 (0.44)
2.05 (0.24)
24.22 (0.85)
24.31 (0.83)
1.48 (0.01)
Tab
79.35 (0.03)
-0.13 (0.01)
12.76 (0.05)
17.45 (0.00)
−1.56 (0.00)
t0
77.46 (0.83)
2.26 (0.33)
24.27 (0.68)
24.38 (0.68)
1.47 (0.01)
t1
77.69 (0.87)
2.45 (0.18)
24.72 (0.94)
24.84 (0.93)
1.47 (0.00)
t7
78.39 (1.33)
2.93 (0.55)
26.08 (1.53)
26.24 (1.57)
1.45 (0.01)
t14
79.85 (0.79)
3.86 (0.25)
28.12 (0.45)
28.38 (0.43)
1.43 (0.01)
t21
80.15 (0.68)
3.89 (0.30)
28.68 (0.53)
28.94 (0.52)
1.43 (0.01)
tab
75.36 (0.02)
1.57 (0.01)
17.38 (0.02)
14.17 (0.00)
1.48 (0.00)
t0
76.82 (1.12)
1.50 (0.38)
20.68 (1.20)
20.74 (1.22)
1.49 (0.01)
t1
76.45 (1.33)
1.56 (0.32)
22.00 (1.16)
22.06 (1.17)
1.50 (0.01)
t7
76.72 (0.86)
1.69 (0.12)
23.36 (1.54)
23.42 (1.54)
1.49 (0.00)
t14
78.95 (0.61)
2.43 (0.20)
25.83 (0.84)
25.95 (0.83)
1.47 (0.00)
t21
79.23 (0.53)
2.50 (0.19)
25.95 (0.61)
26.07 (0.61)
1.47 (0.00)
Charisma
Opallis
L* = (lightness); a* = (green–red coordinate); b* = (blue–yellow coordinate); C* = (chroma); H* (hue).
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TABLE 2. Composite resin specimen color difference (ΔE) over time in comparison with Vitapan Classical shade tab for specimens stored dry (GD) and in artificial saliva (GS) Time
Color change (ΔE00)–Mean (SD) Z350 GD
Charisma GS
Mean of GD and GS
GD
Opallis GS
Mean of GD and GS
GD
GS
Mean of GD and GS
t0
1.64 (0.56)
2.21 (0.28)
1.92β (0.51)
1.27 (0.18)
1.48 (0.14)
1.37α (0.19)
1.17 (0.59)
1.50 (0.72)
1.34α (0.65)
t1
1.09 (0.57)
1.66 (0.34)
1.37α (0.53)
1.41 (0.26)
1.72 (0.24)
1.57α (0.29)
1.14 (0.23)
1.74 (0.58)
1.44α (0.52)
t7
2.32b (0.65)
1.18a (0.21)
1.75αβ (0.75)
2.98b (0.81)
1.59a (0.11)
2.28β (0.91)
1.24 (0.45)
1.43 (0.49)
1.34α (0.46)
t14
2.70 (0.40)
2.60 (0.27)
2.65γ* (0.33)
3.69 (0.24)
3.45 (0.28)
3.57γ* (0.28)
2.13 (0.17)
1.98 (0.40)
2.06β (0.30)
t21
2.84 (0.30)
2.87 (0.15)
2.85γ* (0.23)
3.76 (0.25)
3.89 (0.31)
3.83γ* (0.28)
2.16 (0.13)
2.18 (0.30)
2.17β (0.22)
Tukey post-hoc test, different letters indicate statistical differences between measures of the same brand as a function of storage (p < 0.05). Tukey post-hoc test, different letters indicate statistical differences between measures of the same brand as a function of time (p < 0.05). t0, immediately after polymerization; t1, 24 hours; t7, 7 days; t14, 14 days; and t21, 21 days after polymerization. *Beyond the threshold of acceptability (ΔE00< = 2.23).
a,b
α,β,γ
TABLE 3. Composite resin specimens color difference (ΔE) over time in comparison with their respective manufacturer’s shade guide tab for specimens stored dry (GD) and in artificial saliva (GS) Time
Color change (ΔE00)–Mean (SD) Z350 GD
Charisma GS
Mean of GD and GS
GD
Opallis GS
Mean of GD and GS
GD
GS
Mean of GD and GS
t0
3.41 (0.73)
2.92 (0.22)
3.16α (0.57)
6.71 (0.36)
6.98 (0.14)
6.84α (0.29)
2.50 (1.00)
1.81(0.54)
2.16α (0.84)
t1
4.43b (0.14)
3.37a (0.41)
3.90β (0.63)
6.82 (0.27)
7.28 (0.29)
7.05α (0.36)
2.46 (0.16)
2.92 (1.12)
2.69αβ (0.80)
t7
5.56c (0.75)
3.74b (0.26)
4.65γ (1.09)
8.14b (0.62)
7.15a (0.10)
7.64β (0.67)
3.39 (0.74)
3.32 (0.98)
3.29β (0.83)
t14
5.88 (0.38)
5.37 (0.10)
5.62δ* (0.38)
8.68 (0.13)
8.55 (0.13)
8.62γ* (0.14)
5.14 (0.21)
4.92 (0.48)
5.03δ* (0.37)
t21
5.88 (0.36)
5.55 (0.11)
5.72δ* (0.31)
8.75 (0.17)
8.89 (0.21)
8.82γ* (0.19)
5.16 (0.18)
5.18 (0.31)
5.17δ* (0.24)
Tukey post-hoc test, different letters indicate statistical differences between measures of the same brand as a function of storage (p < 0.05). Tukey post-hoc test, different letters indicate statistical differences between measures of the same brand as a function of time (p < 0.05). t0 = immediately after polymerization; t1 = 24 hours; t7 = 7 days; t14 = 14 days; and t21 = 21 days after polymerization. *Beyond the threshold of acceptability (ΔE00< = 2.23). a,b,c
α,β,γ,δ
respective tabs, had no significant effect over color change for Charisma (p = 0.4515), or Opallis (p = 0.6281) specimens; however, for Z350 a significant effect was found (p = 0.0013). Tukey post-hoc test showed significant differences as a function of time until t14 relative to all tabs. However, no significant color differences between t14 and t21 was found for any of the specimens relative to Vita tab (Z350: p = 0.5930; Charisma: p = 0.3590; Opallis p = 0.9766), or their respective manufacturers’ tabs
© 2014 Wiley Periodicals, Inc.
DOI 10.1111/jerd.12106
(Z350: p = 0.9147; Charisma: p = 0.4291; Opallis p = 0.9716). Concerning storage, although some significant differences were observed at different times, at t14 and t21, no significant differences between the DG and SG were found for any of the tested materials relative to any of the tabs (Tables 2 and 3). Student t-test showed that for all brands, composite resin specimens mean ΔE00 at t14 was significantly higher relative to their respective manufacturers’ tabs than to Vita tab (p < 0.0001) (Table 4).
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TABLE 4. Comparative analysis between mean color difference (ΔE00) of composite resin specimens established at 14 days after polymerization (t14) in relation to the Vitapan tab and their respective manufacturers’ tabs Composite Brand
Mean color difference ΔE00 at t14 (SD) Vitapan tab
Manufacturers’ tab
p value*
Z350
2.65 (0.33)
5.62 (0.38)
Color Stability Over Time of Three Resin-Based Restorative Materials Stored Dry and in Artificial Saliva JOANA YUMI TERUYA UCHIMURA, DDS, MS*, FRANCIELLE SATO, PhD†, GISELLY BIANCHI, MSc‡, MAURO LUCIANO BAESSO, PhD†, ROSÂNGELA GERITANA SANTANA, PhD§, RENATA CORRÊA PASCOTTO, PhD¶
ABSTRACT Objective: To evaluate the color match of different composite resins relative to Vitapan Classical shade guide tab and their respective manufacturers’ shade guide tabs as a function of time and storage. Materials and Methods: Three enamel shade A2 composite resins were used to fabricate 36 disk-shaped polymerized specimens (12 each), allocated into 2 groups of 6 and stored dry (GD) and in artificial saliva (GS). CIELAB coordinates from shade tabs and resin specimens immediately after polymerization (t0), and 24 hours (t1), 7 (t7), 14 (t14) and 21 (t21) days after polymerization were captured using a colorimeter. Color difference (ΔE00) between composite specimens and the reference tabs was calculated using the CIEDE2000 formula. The results were analyzed with repeated measures ANOVA, Tukey’s HDS post-hoc test, and Student t test (p ≤ 0.05). Results: Color of the three tested composites relative to Vita and their respective tabs significantly changed as a function of time until t14; however, between t14 and t21, no significant differences were found. No differences in color were found relative to storage at t14 and t21. ΔE00 values of specimens at t14 were significantly higher relative to their respective tabs than to Vitapan tab. Conclusions: For all brands color changed up to day 14, when it stabilized, regardless of whether composite specimens had been stored in artificial saliva or simply in a box. Vitapan tab presented a better color match than the manufacturers’ tabs.
CLINICAL SIGNIFICANCE The results found in this study demonstrated that the Vitapan Classical shade guide tab A2 provided a better color match than the respective shade guide tabs A2 supplied by the composite manufacturers. If custom shade tabs are to be made, however, they could be kept in a box and used as shade references from 14 days after being fabricated, when color stabilizes. (J Esthet Restor Dent 26:279–287, 2014)
INTRODUCTION Because of its natural and pleasing appearance, composite resins have been widely used in the restorative dentistry to provide for the increasing
demand for an esthetic dentition.1,2 However, one of the major sources of patient dissatisfaction with restorative treatments with composite resins concerns the visible differences in color between teeth and restorations.3 Achieving an optimal tooth/composite resin restoration
*Resident, Department of Dentistry, State University of Maringá, Maringá, Paraná, Brazil † Associate Professor, Department of Physics, State University of Maringá, Maringá, Paraná, Brazil ‡ PhD Applicant, Department of Physics, State University of Maringá, Maringá, Paraná, Brazil § Associate Professor, Department of Statistics, State University of Maringá, Maringá, Paraná, Brazil ¶ Associate Professor, Department of Dentistry, State University of Maringá, Maringá, Paraná, Brazil
© 2014 Wiley Periodicals, Inc.
DOI 10.1111/jerd.12106
Journal of Esthetic and Restorative Dentistry
Vol 26 • No 4 • 279–287 • 2014
279
COLOR STABILITY OF COMPOSITE RESINS Uchimura et al.
color match represents a challenge, especially in the anterior teeth, where even small shade discrepancies can represent an esthetical concern for highly demanding patients.4 Composite resin manufacturers generally use Vitapan Classical shade guide tabs (VITA Zahnfabrik, Bad Sackingen, Germany) as color references for their own reference shade tabs and composite resins.5 However, shade tabs from different commercially available systems frequently present poor matching compared with target Vitapan Classical tabs.1,6–13 In addition to that, several studies have also been carried out comparing different resin composite systems of the same shade, finding low or even no color correspondence among them.1,14–16 When in its natural environment in the oral cavity, composite resin restorations are in constant contact with moisture. Thus, several studies have been performed to assess the effect of moisture on color change, both in water and artificial saliva. These studies have demonstrated statistically significant differences between baseline and post immersion color values.4,17–20 In addition to immersion, time has also been shown to have a significant influence on color stability.4,18–20 Composite resin specimens stored in water showed the highest degree of color change in the first 24 hours and at 7 days, but after 1 month only minor changes were observed.4,21 As a result, restorative dentists cannot take manufacturers color designations for granted when selecting the right color shade for restorations.2,18 Although color designations have their importance as an initial reference, dentists should understand and apply esthetic as well as technical principles when choosing color of restorative materials.2 Different strategies have been suggested to help dentists with color shade selection before starting the restorative procedure. A piece of unpolymerized resin material can be placed on, or adjacent to the tooth to be restored and polymerized to confirm the selected shade of the esthetic material.2,18 The disadvantage of this approach is that it does not take into account further changes in color that take place because of moisture and time.
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Alternatively, custom-made shade guides could be a viable option because of the possibility of superpositioning different thicknesses of enamel and dentin resins in order to obtain the final color outcome.2 In this case, however, defining when to use and how to store custom-made tabs becomes an important issue. The purpose of this study was to evaluate the color match of different composite resins relative to their corresponding Vitapan Classical shade guide tab and the shade guide tabs supplied by the manufacturers as a function of time and storage (dry or in artificial saliva). The null hypotheses were: (1) color difference of specimens relative to Vitapan tab will not be significantly different from that of specimens relative to their respective manufacturer’s shade tab; and (2) color difference of specimens stored in artificial saliva will not be significantly different from those stored dry.
MATERIALS AND METHODS Specimen Preparation A total of 36 disk-shaped composite resin specimens were fabricated using a metal ring mold measuring 10 mm in diameter × 2 mm thick. Three different commercially available composite resin systems (enamel shade A2) were used in this study: Charisma Opal (Heraeus Kulzer, Hanau, Germany), Filtek Z350 XT (3M ESPE, St. Paul, MN, USA), and Opallis (FGM, Joinville, SC, Brazil). The metal ring was placed onto a glass microscope slide and filled with unpolymerized composite resin, which was then covered with a clear polyethylene terephthalate strip. Another glass slide was then placed onto the strip, and the specimen was light-cured for 40 seconds using a light-emitting diode (LED) polymerizing device (Radii—SDI, Victoria, Australia). A total of 12 specimens were made from each material. Specimens had a smooth surface upon removal from the mold and no further polishing was performed. All specimens were produced with resin coming from the same respective syringe. Polymerized specimens were randomly allocated into two experimental groups. Half of the specimens (six
DOI 10.1111/jerd.12106
© 2014 Wiley Periodicals, Inc.
COLOR STABILITY OF COMPOSITE RESINS Uchimura et al.
specimens per material) were separated to be stored in a box (DG), protected from the light at room temperature, whereas the other half was kept immersed into artificial saliva (SG) inside an incubator at 37°C throughout the experimental period.
polymerization. Three independent measurements were made each time and averaged together to establish the CIELAB color coordinate values.
Color Measurement
CIELAB values were converted into units of CIEDE2000 color notation formula (ΔE00), which was used to calculate color difference as follows:
A Minolta CR-400 reflectance colorimeter (Konica Minolta Sensing, Inc., Osaka Japan) was used to capture CIELAB color coordinates. The colorimeter is designed in a diffusion illumination mode, 0° viewing geometry angle, including specular components. This illumination method illuminates the specimen from all directions using a D65 source with almost completely equal brightness and receives the reflected light vertically from the specimen surface. The colorimeter aperture for light irradiation over the sample surface was 10 mm. The illumination and measurement areas have diameters of 11 and 8 mm, respectively. The light source is a pulsed xenon lamp which is diffused into a diffusion chamber and directed to diffusion plates positioned about 6 mm above the specimen surface. Measurements were conducted against a diffuse white background,22 using the International Commission on Illumination (CIELAB) L* a* b* C* H* color scale, where L* refers to lightness, ranging from zero to 100 (higher number being brighter); a* to green–red coordinate; b* to blue–yellow coordinate; C* to chroma (lower number means lower chroma); H* to hue (e-specific color measured from zero to 360°: 0° is red, 90° yellow, 180° green, and 270° blue).7 The colorimeter was calibrated using the white calibration plate provided by the manufacturer. Color measurements were taken from a Vitapan Classical tab A2. While the tab was held by the handle, the probe of the Minolta CR-400 was placed in the middle-third of the tab. The same procedure was conducted for the shade guide tabs supplied by the manufacturer of each tested material by placing the probe in the central area of the tabs. Color of specimens was measured at five different experimental times: immediately after polymerization (t0); 24 hours (t1); 7 days (t7); 14 days (t14); and 21 days (t21) after
© 2014 Wiley Periodicals, Inc.
DOI 10.1111/jerd.12106
Color Difference
(
) ( 2
) ( ) 2
ΔE00 = ⎡ ΔL ′ k L SL + ΔC ′ kC SC + ΔH ′ k H SH ⎣ 12 + RT ΔC ′ kC SC ) (ΔH ′ k H SH ⎤⎦
(
)
2
where ΔL′, ΔC′, and ΔH′ are the differences in lightness, chroma, and hue for a pair of samples in CIEDE2000, and RT is a function (the so-called rotation function) that accounts for the interaction between chroma and hue differences in the blue region. Weighting functions, SL, SC, SH, adjust the total color difference for variation in the location of the color difference pair in L0, a0, b0 coordinates and the parametric factors, KL, KC, KH, are correction terms for experimental conditions.23 To verify color change as a function of time and storage, color difference (ΔE00) was calculated between the Vitapan Classical A2 tab and specimens in both groups (DG and SG) for each experimental time. The same procedure was conducted with each composite resin tab and their corresponding specimens. The 50:50% acceptability threshold adopted in this study was ΔE00 = 2.23.24
Statistical Analysis Shapiro–Wilk test demonstrated that the data was normally distributed. ΔE00 results were evaluated using the repeated measures analysis of variance (ANOVA) to verify the influence of time, storage, and their interactions for each individual brand of resin separately. Tukey HDS post-hoc test was then applied to verify where differences between groups existed. A comparative analysis between mean color difference (ΔE00) of composite resin specimens established at 14 days after polymerization (t14) relative to the Vita tab
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and their respective manufacturers’ tabs was performed using Student t-test for independent samples. All analyses were performed using Statistical Analysis System (SAS), at a level of significance of 5% (p < 0.05).
RESULTS The CIELAB A2 mean color shade coordinates of Vitapan Classical and Z350, Charisma and Opallis shade guide tabs and their respective composite specimens over time measured with Minolta CR-400 are presented in Table 1.
Mean color difference (ΔE00) between Vitapan Classical A2 tab and specimens, and the composites shade tabs and their respective specimens, as a function of time and storage (DG and SG), are presented in Tables 2 and 3, respectively. Repeated measures ANOVA demonstrated that time had a significant effect over color change of composite specimens of all brands tested (p < 0.0001), regardless of the reference shade tab, with a power of test of 1.00. Storage, on the other hand, proved to have no significant effect over color change for any of the brands tested relative to Vita tab (Z350: p = 0.9251; Charisma: p = 0.066; Opallis: p = 0.0723). Storage, relative to the composites
TABLE 1. CIELAB A2 color shade coordinates of Vitapan Classical tab and Z350, Charisma and Opallis shade guide tabs and their respective composite resins over time measured with Minolta CR-400 L* (SD)
a* (SD)
b* (SD)
C* (SD)
H* (SD)
Vitapan
Tab
77.94 (0.01)
1.65 (0.00)
22.09 (0.00)
22.15 (0.00)
1.49 (0.00)
Z350
Tab
79.72 (0.01)
0.44 (0.01)
14.17 (0.00)
12.76 (0.00)
1.53 (0.00)
t0
78.33 (1.12)
1.01 (0.28)
19.10 (1.49)
19.13 (1.47)
1.51 (0.01)
t1
78.43 (1.21)
1.02 (0.26)
20.69 (1.46)
20.71 (1.46)
1.52 (0.01)
t7
79.79 (1.23)
1.39 (0.11)
22.44 (2.28)
22.48 (2.28)
1.50 (0.00)
t14
81.36 (0.55)
1.96 (0.35)
24.11 (1.02)
24.20 (1.00)
1.48 (0.01)
t21
81.69 (0.44)
2.05 (0.24)
24.22 (0.85)
24.31 (0.83)
1.48 (0.01)
Tab
79.35 (0.03)
-0.13 (0.01)
12.76 (0.05)
17.45 (0.00)
−1.56 (0.00)
t0
77.46 (0.83)
2.26 (0.33)
24.27 (0.68)
24.38 (0.68)
1.47 (0.01)
t1
77.69 (0.87)
2.45 (0.18)
24.72 (0.94)
24.84 (0.93)
1.47 (0.00)
t7
78.39 (1.33)
2.93 (0.55)
26.08 (1.53)
26.24 (1.57)
1.45 (0.01)
t14
79.85 (0.79)
3.86 (0.25)
28.12 (0.45)
28.38 (0.43)
1.43 (0.01)
t21
80.15 (0.68)
3.89 (0.30)
28.68 (0.53)
28.94 (0.52)
1.43 (0.01)
tab
75.36 (0.02)
1.57 (0.01)
17.38 (0.02)
14.17 (0.00)
1.48 (0.00)
t0
76.82 (1.12)
1.50 (0.38)
20.68 (1.20)
20.74 (1.22)
1.49 (0.01)
t1
76.45 (1.33)
1.56 (0.32)
22.00 (1.16)
22.06 (1.17)
1.50 (0.01)
t7
76.72 (0.86)
1.69 (0.12)
23.36 (1.54)
23.42 (1.54)
1.49 (0.00)
t14
78.95 (0.61)
2.43 (0.20)
25.83 (0.84)
25.95 (0.83)
1.47 (0.00)
t21
79.23 (0.53)
2.50 (0.19)
25.95 (0.61)
26.07 (0.61)
1.47 (0.00)
Charisma
Opallis
L* = (lightness); a* = (green–red coordinate); b* = (blue–yellow coordinate); C* = (chroma); H* (hue).
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COLOR STABILITY OF COMPOSITE RESINS Uchimura et al.
TABLE 2. Composite resin specimen color difference (ΔE) over time in comparison with Vitapan Classical shade tab for specimens stored dry (GD) and in artificial saliva (GS) Time
Color change (ΔE00)–Mean (SD) Z350 GD
Charisma GS
Mean of GD and GS
GD
Opallis GS
Mean of GD and GS
GD
GS
Mean of GD and GS
t0
1.64 (0.56)
2.21 (0.28)
1.92β (0.51)
1.27 (0.18)
1.48 (0.14)
1.37α (0.19)
1.17 (0.59)
1.50 (0.72)
1.34α (0.65)
t1
1.09 (0.57)
1.66 (0.34)
1.37α (0.53)
1.41 (0.26)
1.72 (0.24)
1.57α (0.29)
1.14 (0.23)
1.74 (0.58)
1.44α (0.52)
t7
2.32b (0.65)
1.18a (0.21)
1.75αβ (0.75)
2.98b (0.81)
1.59a (0.11)
2.28β (0.91)
1.24 (0.45)
1.43 (0.49)
1.34α (0.46)
t14
2.70 (0.40)
2.60 (0.27)
2.65γ* (0.33)
3.69 (0.24)
3.45 (0.28)
3.57γ* (0.28)
2.13 (0.17)
1.98 (0.40)
2.06β (0.30)
t21
2.84 (0.30)
2.87 (0.15)
2.85γ* (0.23)
3.76 (0.25)
3.89 (0.31)
3.83γ* (0.28)
2.16 (0.13)
2.18 (0.30)
2.17β (0.22)
Tukey post-hoc test, different letters indicate statistical differences between measures of the same brand as a function of storage (p < 0.05). Tukey post-hoc test, different letters indicate statistical differences between measures of the same brand as a function of time (p < 0.05). t0, immediately after polymerization; t1, 24 hours; t7, 7 days; t14, 14 days; and t21, 21 days after polymerization. *Beyond the threshold of acceptability (ΔE00< = 2.23).
a,b
α,β,γ
TABLE 3. Composite resin specimens color difference (ΔE) over time in comparison with their respective manufacturer’s shade guide tab for specimens stored dry (GD) and in artificial saliva (GS) Time
Color change (ΔE00)–Mean (SD) Z350 GD
Charisma GS
Mean of GD and GS
GD
Opallis GS
Mean of GD and GS
GD
GS
Mean of GD and GS
t0
3.41 (0.73)
2.92 (0.22)
3.16α (0.57)
6.71 (0.36)
6.98 (0.14)
6.84α (0.29)
2.50 (1.00)
1.81(0.54)
2.16α (0.84)
t1
4.43b (0.14)
3.37a (0.41)
3.90β (0.63)
6.82 (0.27)
7.28 (0.29)
7.05α (0.36)
2.46 (0.16)
2.92 (1.12)
2.69αβ (0.80)
t7
5.56c (0.75)
3.74b (0.26)
4.65γ (1.09)
8.14b (0.62)
7.15a (0.10)
7.64β (0.67)
3.39 (0.74)
3.32 (0.98)
3.29β (0.83)
t14
5.88 (0.38)
5.37 (0.10)
5.62δ* (0.38)
8.68 (0.13)
8.55 (0.13)
8.62γ* (0.14)
5.14 (0.21)
4.92 (0.48)
5.03δ* (0.37)
t21
5.88 (0.36)
5.55 (0.11)
5.72δ* (0.31)
8.75 (0.17)
8.89 (0.21)
8.82γ* (0.19)
5.16 (0.18)
5.18 (0.31)
5.17δ* (0.24)
Tukey post-hoc test, different letters indicate statistical differences between measures of the same brand as a function of storage (p < 0.05). Tukey post-hoc test, different letters indicate statistical differences between measures of the same brand as a function of time (p < 0.05). t0 = immediately after polymerization; t1 = 24 hours; t7 = 7 days; t14 = 14 days; and t21 = 21 days after polymerization. *Beyond the threshold of acceptability (ΔE00< = 2.23). a,b,c
α,β,γ,δ
respective tabs, had no significant effect over color change for Charisma (p = 0.4515), or Opallis (p = 0.6281) specimens; however, for Z350 a significant effect was found (p = 0.0013). Tukey post-hoc test showed significant differences as a function of time until t14 relative to all tabs. However, no significant color differences between t14 and t21 was found for any of the specimens relative to Vita tab (Z350: p = 0.5930; Charisma: p = 0.3590; Opallis p = 0.9766), or their respective manufacturers’ tabs
© 2014 Wiley Periodicals, Inc.
DOI 10.1111/jerd.12106
(Z350: p = 0.9147; Charisma: p = 0.4291; Opallis p = 0.9716). Concerning storage, although some significant differences were observed at different times, at t14 and t21, no significant differences between the DG and SG were found for any of the tested materials relative to any of the tabs (Tables 2 and 3). Student t-test showed that for all brands, composite resin specimens mean ΔE00 at t14 was significantly higher relative to their respective manufacturers’ tabs than to Vita tab (p < 0.0001) (Table 4).
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TABLE 4. Comparative analysis between mean color difference (ΔE00) of composite resin specimens established at 14 days after polymerization (t14) in relation to the Vitapan tab and their respective manufacturers’ tabs Composite Brand
Mean color difference ΔE00 at t14 (SD) Vitapan tab
Manufacturers’ tab
p value*
Z350
2.65 (0.33)
5.62 (0.38)
