Color and contrast ratio of resin composites for whitenedteeth

Juliana da Costa a,1, Marcos Vargas b,*, Edward J. Swift Jr.c, Eric Anderson d,Stephanie Ritter e

aDepartment of Restorative Dentistry, Oregon Health and Sciences University, 611 SW Campus Drive, Portland, OR 97239-3097, United StatesbDepartment of Family Dentistry, The University of Iowa, 801 Newton Rd, Iowa City, IA 52242, United StatescDepartment of Operative Dentistry, University of North Carolina, 433 Brauer Hall, CB# 7450, Chapel Hill, NC 27599-7450, United StatesdDepartment of Restorative Dentistry, Oregon Health and Sciences University, United StateseMinot, ND, United States

j o u r n a l o f d e n t i s t r y 3 7 s ( 2 0 0 9 ) e 2 7 – e 3 3

a r t i c l e i n f o

Article history:

Received 5 March 2009

Received in revised form

22 April 2009

Accepted 5 May 2009

Keywords:

Resin composite

Composite color

Opacity

Translucency

Lightness

a b s t r a c t

Objectives: The purpose of this study was to determine the optical properties, color and

contrast ratio (CR) of commercially available resin composites marketed for the restoration

of whitened teeth.

Methods: Twenty-six resin composites designed for restoration of whitened teeth and four

shade B1 (control) were evaluated. Five resin composite disks (d = 12 mm, h = 1.54 mm) were

fabricated for each shade of composite and were stored in water at 37 8C for at least 24 h. A

colorimeter was used to measure specimen color over both white and black backgrounds.

CIELAB and CIExyY color spaces were used. The CIELAB color notation system provides

values for L*a*b*. The CIExyY system provides lightness and chromaticity values, where Y

represents lightness and xy chromaticity. The contrast ratio (CR) was assessed using, CIE

xyY, of the specimens against black (Yb) and white (Yw) backgrounds, with CR = Yb/Yw. The

data for L*, a*, b* and CR were analyzed by one-way ANOVA, Tukey’s test, and the correlation

L* and CR was analyzed by Pearson correlation test (a = 0.05).

Results: Significantly different L*, a*, b* values and CR were observed. Premise XL2 had the

highest L* and CR values and Vit-l-escence PS had the lowest. Vit-l-escence PS had the

highest a* value and Point 4XL2 had the lowest, Premise XL1 had the highest b* value and

Supreme WB the lowest. The L* and CR correlation was positive and statistically significant.

Conclusions: Composites designated for whitened teeth have different levels of color and

contrast ratio. Awareness of the optical properties of the composites allows the operator to

choose the appropriate materials to mimic the remaining tooth structure.

Published by Elsevier Ltd.

available at www.sciencedirect.com

journal homepage: www.intl.elsevierhealth.com/journals/jden

1. Introduction

The color and esthetic appearance of natural teeth has become

increasingly important for patients over the last few decades.

* Corresponding author.E-mail addresses: dacostaj@hsu.edu (J. da Costa), marcos-vargas@

1 Tel.: +1 503 494 8943; fax: +1 503 494 8339.0300-5712/$ – see front matter. Published by Elsevier Ltd.doi:10.1016/j.jdent.2009.05.005

New materials are continually introduced to the dental

profession to meet the demand for better esthetics.1 In

1969, Phillips predicted that there would be an adhesive

material to restore the tooth to its original strength and color.

uiowa.edu (M. Vargas).

Table 1 – Resin composites evaluated.

Resin composite Manufacturer Bleach shades

4-Seasons Ivoclar Vivadent,

Schaan, Liechtenstein

L, XL, XXL

Durafil Heraeus Kulzer,

South Bend, IN, USA

SL, SSL

Esthet-X Denstply Caulk,

Milford, DE, USA

W, XL, WO, WE

Filtek Supreme 3M ESPE, St. Paul,

MN, USA

XWE, XWB, XWD,

WD, WB, WE

Point 4 Kerr Corporation,

Orange, CA, USA

XL1, XL2, XL3

Premise Kerr Corporation XL1, XL2

Renamel Cosmedent, Chicago,

IL, USA

SB1, SB2, SB3, LO, W

Vit-l-escence Ultradent Products,

South Jordan, UT, USA

OS, PS

j o u r n a l o f d e n t i s t r y 3 7 s ( 2 0 0 9 ) e 2 7 – e 3 3e28

Although direct composites are better able to do so now than

in the past, they not yet become the desired panacea.2

There are several advantages to direct restorations; they

typically require only one treatment visit3 while providing

acceptable results.4 The natural appearance and function can

be restored while conserving tooth structure. They also give

patients the ability to communicate directly with the dentist

regarding the desired characteristics of smile design and allow

the restoration to be placed through freehand craftsmanship,

until both patient and dentist are pleased with the results.4

However, direct restorations are not without their own unique

challenges.

One of the difficulties the clinician faces is selecting the

appropriate resin composite material that simulates the

physical and optical characteristics of enamel and dentin.

The appearance of a tooth is determined the combination of

their optical properties, primarily those of dentin with

modification by enamel. Enamel is much more translucent

and less chromatic than dentin. Dentin provides fluorescence

and enamel provides opalescence. Information about the

optical properties of the resin composites will allow the

operator to relate them to specific optical properties of dentin

and enamel, which can themselves differ from cervical to

incisal.5 Characterizing the optical properties of resin compo-

site materials by will allow the operator to more closely match

a restoration to the natural tooth.

Optical properties vary with different composite resin

materials according to their composition and color modifiers.

Even within the same resin system, different opacities are

available. Moreover, different composite resins render differ-

ent color, translucency and opacity characteristics and this

should be considered when selecting the restorative material.

Several studies have evaluated the different colors6–14 and

opacity/translucency10–12,15 of resin composites. However,

information is lacking on resin composites intended for use

with whitened teeth. To date there are only two articles that

have evaluated composites designed for whiten teeth.16,17

Whitening procedures frequently result in teeth that are

substantially brighter than the lightest shades on standard

guides. Despite the large use of tooth whitening products,

little information is available on the optical properties of

modern resin composite materials manufactured for the

restoration of whitened teeth. Identification and categoriza-

tion of the optical characteristics of these materials is a

necessity.

The purpose of this study was to determine the optical

properties, color and opacity (contrast ratio) of commercially

available resin composites marketed for the restoration of

whitened teeth. The null hypothesis tested was that all resin

composites for whitened teeth would have similar levels of

color and contrast ratio.

2. Materials and methods

Twenty-six resin composites designed for restoration or

augmentation of whitened teeth were evaluated (Table 1).

Four shade B1 composites, designed as enamel replacements,

were used as controls: Point 4 body; Filtek Supreme enamel,

Durafil, and Herculite XRV enamel.

Resin composite disks of 12 mm in diameter and 1.54 mm

in thickness were fabricated using two glass slides and two

spacers. The composite were delivered to the slides using a

hand instrument (Almore International Inc., Portland, OR,

USA). The material was gently pressed between the slides to

prevent inclusion of voids and to ensure uniform thickness

of approximately 1.54 mm. The material was light activated

for 60 s from each side using a Demetron 401 QTH unit

(Demetron/Kerr, Orange, CA, USA) with energy of the

polymerization light of at least 600 mW/cm2. Five specimens

were fabricated for each type and shade of resin composite.

The specimens were stored in water in lightproof containers

at 37 8C for at least 24 h. No polishing was done, so as to

avoid modification of the surfaces that could affect the

results.

A Minolta Chroma Meter (CR 221, Minolta, Ramsey, NJ, USA)

was used to measure specimen color over both white and

black backgrounds. The Chroma Meter measures color and

provides values in various ‘‘color notation systems.’’ The

CIELAB and CIExyY color spaces were used in this study. The

CIELAB color space system provides values for L*a*b*, in which

L* represents lightness, a* the red-green axis, and b* the

yellow-blue axis. The CIExyY system provides lightness and

chromaticity values, where Y represents lightness and xy

represents chromaticity.

Opacity/translucency was assessed by obtaining the con-

trast ratio (CR) of the lightness or Y value, CIE xyY, of the

specimens against black (Yb) and white (Yw) backgrounds,

with CR = Yb/Yw.

The data for L*, a*, b* and CR were each analyzed using a

one-way ANOVA and Tukey’s HSD post-hoc test at the 0.05

significance level. The correlation between lightness and

opacity was analyzed using Pearson correlation test at the

same significance level.

3. Results

Composite L*, a*, b*, and CR data are shown in Tables 1 and 2,

respectively.

The order of composites ranked according to L*, from the

most to least bright, is shown in Fig. 1. Premise XL2 had

the highest L* value (85.57) and Vit-l-escence PS had the

Fig. 1 – Lightness (L*) of the composites evaluated.

j o u r n a l o f d e n t i s t r y 3 7 s ( 2 0 0 9 ) e 2 7 – e 3 3 e29

lowest (59.23). The order of composites ranked according to

a*, from the lowest to the highest a*, is shown in Fig. 2. Vit-l-

escence PS had the highest a* value (�0.02) and Point 4XL2

had the lowest (�3.39). The order of composites ranked

according to b*, from the most to least yellow, is shown in

Fig. 3. Premise XL1 had the highest b* value (5.50) and

Supreme WB the lowest (�6.23). ANOVA revealed that

several of the composites had significantly different L*, a*,

Fig. 2 – a* values of the co

and b* values; therefore, the null hypothesis was rejected

(Table 2).

The statistical analysis also revealed significant differences

in CR values; again causing rejection of the null hypothesis.

Premise XL2 had the highest opacity value (CR = 0.88) and Vit-

l-escence PS had the lowest (CR = 0.31). The order of

composites ranked according to CR, from the most to least

opaque, is shown in Fig. 4.

mposites evaluated.

Fig. 3 – b* values of the composites evaluated.

j o u r n a l o f d e n t i s t r y 3 7 s ( 2 0 0 9 ) e 2 7 – e 3 3e30

The Pearson correlation test revealed a strong (r = 0.91)

and statistically significant positive correlation between

opacity and lightness, indicating that the more opaque

composites are also lighter.

Table 2 – Lightness (L*), a*, b*, and contrast ratio (CR) of resin

Resin composite/shade Mean L* S.D. L* Mean a*

4-Seasons L 62.14 0.51 �1.05

4-Seasons XL 65.08 0.79 �2.14

4-Seasons XXL 70.29 0.55 �1.98

Durafil SL 73.47 0.31 �2.69

Durafil SSL 73.78 0.53 �1.50

Esthet-X W 74.95 0.27 �2.26

Esthet-X WE 61.06 0.32 �0.28

Esthet-X WO 81.88 0.35 �2.49

Esthet-X XL 65.77 0.3 �1.46

Point 4 XL1 62.10 0.3 �2.58

Point 4 XL2 65.45 0.19 �3.39

Point 4 XL3 74.02 0.28 �2.97

Premise XL1 78.35 0.08 �1.57

Premise XL2 85.57 0.12 �1.94

Renamel LO 70.55 0.15 �0.40

Renamel SB1 75.94 0.22 �2.05

Renamel SB2 74.89 0.2 �1.89

Renamel SB3 73.31 0.11 �1.53

Renamel W 77.33 0.28 �2.91

Supreme WB 67.89 0.4 �2.40

Supreme WD 73.67 0.17 �3.11

Supreme WE 61.71 0.38 �0.22

Supreme XWB 70.43 0.41 �0.27

Supreme XWD 76.23 11.3 �2.36

Vit-l-escence OS 73.99 0.16 �2.00

Vit-l-escence PS 59.23 0.9 �0.02

Herculite XRV B1E 61.74 0.66 �1.62

Durafil B1 62.24 0.45 �2.06

Supreme B1E 61.00 0.43 �1.22

Point 4 B1 body 65.44 0.22 65.44

4. Discussion

Selecting the appropriate restorative resin composite materi-

als that simulate the physical and optical characteristics of

composites tested.

S.D. a* Mean b* S.D. b* Mean CR S.D. CR

0.06 2.31 0.30 0.40 0.00

0.08 1.66 0.41 0.54 0.02

0.06 1.39 0.50 0.63 0.01

0.06 3.26 0.15 0.65 0.00

0.01 1.29 0.68 0.68 0.03

0.1 �3.35 0.24 0.66 0.01

0.14 �3.11 0.16 0.36 0.01

0.08 0.18 0.43 0.64 0.32

0.06 �2.28 0.14 0.53 0.01

0.18 0.32 0.37 0.48 0.01

0.4 3.12 1.36 0.57 0.01

0.15 3.27 0.36 0.72 0.00

0.08 5.50 0.17 0.79 0.00

0.06 4.91 0.13 0.88 0.00

0.07 0.55 0.30 0.64 0.10

0.18 �0.12 0.36 0.68 0.08

0.15 0.77 0.52 0.66 0.07

0.02 0.53 0.12 0.64 0.00

0.08 0.17 0.30 0.68 0.00

0.08 �6.41 0.20 0.58 0.01

0.14 �6.23 0.25 0.72 0.01

0.05 �1.78 0.28 0.40 0.00

0.13 �2.97 0.21 0.68 0.00

0.04 �3.17 0.09 0.74 0.00

0.03 �0.29 0.20 0.64 0.00

0.1 1.44 0.31 0.31 0.01

0.08 3.26 0.31 0.49 0.00

0.01 3.08 0.28 0.51 0.00

0.17 5.32 0.67 0.48 0.07

0.22 �3.00 0.23 0.55 0.01

Fig. 4 – Contrast ratio of the composites evaluated.

j o u r n a l o f d e n t i s t r y 3 7 s ( 2 0 0 9 ) e 2 7 – e 3 3 e31

enamel and dentin can provide functional and esthetic

restorations. Color and contrast ratio are very important

optical characteristics of every tooth-colored restorative

material intended to simulate enamel or dentin.

In this study, the color and contrast ratio of various enamel

shade composites for whitened teeth were evaluated. The

lightness,orL* intheCIELABcolornotationsystem, iscommonly

known in dentistry as ‘‘Value’’ from the Munsell color space.

Value is a visual perception according to which a specimen

appears to reflect a greater or smaller fraction of the incident

light.18 It also has been described as the amount of white present

in a specimen. The a* measures the color along the red-green

axis and b* measures color along the yellow-blue axis.18

Opacity is commonly defined by as the ratio of the

reflectance of a specimen disk when backed by a black

standard to that when backed by a white standard.19 Opacity

can be considered the inverse of translucency; the more

opaque the material, the less light is transmitted.

The results of this study indicate that the more opaque

composites are lighter, and the less opaque or more

translucent composites are darker. This is in agreement with

a previous study in which evaluated opaque shades compared

to non opaque shades by material brand.11 This information is

important to the clinician when selecting a composite to

restore whitened teeth.

Despite the fact that the composites evaluated (except for

the control groups) were designed for use in bleached teeth,

they displayed a wide range of color and CR. The least opaque

or more translucent enamel-replacement composites such as

Vit-l-escence PS, Esthet-X WE, and Supreme WE, will allow

more of the underlying tooth structure. To minimize the

background color, a more opaque composite such as a dentin-

opacity composite should be used as a backing in a layering

technique. When there is not enough space for placing various

layers of composite and there is a need to mask the

background, the more opaque shades such as Premise XL2

and Premise XL1 should be selected. Shades denominated as

dentin also can also be used for this purpose, like Filtek

Supreme XWD and WD. However, it is important to notice that

these composites are very opaque and, if not covered by a

more translucent layer, might not match natural tooth

structure. Thus, the thickness of the composite will greatly

influence the final composite color. Kamishira et al. evaluated

the translucency of composites at various thicknesses and

found that translucency increased exponentially as the

thickness was reduced; no matter what shade was used.12

The composites evaluated showed a wide range in a* (color

along the red-green axis) and b* (color along the yellow-blue

axis). The a* values were negative, therefore the composites

showed to be more green in color. The b* values varied from

yellow (+b*) to blue (�b*). Wherever these findings have any

effect on the appearance of bleached shades is unknown.

These differences in a* and b* could be the difference in

concentration of pigments using by manufacturers. Further

investigation of the effect of these values in the appearance of

bleached shades and bleached teeth is necessary.

Within a specific brand of composite, it was expected that

the bleach shades would be brighter and more opaque than

the light Vita shades. Surprisingly, however, some composites

designed to match whitened teeth had similar lightness than

their Vita B1 counterparts. For example, Filtek Supreme WE

and B1 Enamel had similar lightness. The same was true for

Point 4 XL1 and B1 Body. Because their lightness is similar to

the one of B1, these particular bleach shades might not match

j o u r n a l o f d e n t i s t r y 3 7 s ( 2 0 0 9 ) e 2 7 – e 3 3e32

the lightness of whitened teeth well. Clinicians should be

aware of this information when selecting shades to restore

whitened teeth. This problem could be solved if clinicians will

fabricate customized shade guides of their materials to use for

shade selection with whitened teeth.

The Vitapan Classical shade guide has become the standard

for selecting shades of resin composites; consequently, resin

composite manufacturers have tried to match Vita shades in

their materials. Unfortunately, keying different brands of

composite to one universal guide is difficult. Regardless, the

Vitapan Classical serves as a useful starting point for determin-

ing composite shades.13 The clinician can initiate the shade

selection process using the Vitapan guide. If the shade of the

tooth is too bright and not found in the Vitapan shade guide, the

clinician then uses one of the bleach shades.

This study revealed a significantly different color and

contrast ratio among the various composites evaluated, but

statistical differences do not necessarily translate to clinical

differences. For example, some differences are small enough

to be measured electronically but too small to be detected

visually. No studies have evaluated what is clinically sig-

nificant or detectable for differences for contrast ratio.

Moreover, it has been shown that different groups of observers

have different levels of color difference perception, which

might influence the ability to discriminate opacity.20

The correlation of opacity and lightness of resin compo-

sites observed in this study correlates well with an in vitro

study that demonstrated that whitening with 10% carbamide

peroxide increases the opacity of enamel.21 In this regard,

resin composite materials designed for whitened teeth follow

a similar pattern as natural enamel.

Whitening of teeth can result in a wide range of shades

often lighter and less yellow than the Vitapan shade guide

spectrum. As a result, it would be beneficial for dental

manufacturers to have a wide spectrum of shades for

whitened teeth. Unfortunately, our data shows that most

manufacturers tent to cluster their shades and not space them

evenly over the wide potential range of whitened shades.

In this study the composites were not polished. Some

studies found significant differences in lightness due to

polishing. This could be a drawback of this study since

polishing is a common procedure followed by composite

placement. However, the purpose of the study was not to find

absolute values for various systems but to explore their values

and categorize them according to their lightness to help the

clinicians in making shade selection decisions and because all

materials were treated equally, the results are still valid.

It would be interesting to compare the study data with the

opacity and translucency of enamel and dentin. Unfortu-

nately, few studies have evaluated the contrast ratio of enamel

and dentin, primarily because of the difficulty of obtaining

intact dentin and enamel for measurement. A recent study

found that enamel is more translucent, darker, reddish and

yellowish in color when compared to dentin.22 Another study

found that enamel is, as expected, substantially more

translucent than dentin.23

Future research might involve testing different thicknesses

of composites for whitened teeth or evaluating the effect of

layering various thicknesses of enamel and dentin on the

overall appearance, color and contrast ratio.

5. Conclusion

The esthetic success of composite restorations in anterior

teeth is determined largely by the clinician’s ability to

replace the missing tooth structure with a material that

matches not only its color, but also its light transmission

and opacity. This study found that even though the

composites evaluated were designed for whitened teeth

they largely differed in lightness, red-green, yellow-blue and

contrast ratio. Furthermore, the lighter the composites,

the higher the contrast ratio. Awareness of the optical

properties of resin composites allows the operator to choose

the appropriate materials to mimic the remaining tooth

structure.

Conflict of interest statement

None declared.

Source of funding

Funding was provided by the College of Dentistry Dental

Student Research Program, The University of Iowa. Materials

were donated by the dental companies.

Acknowledgement

The materials evaluated were generously donated by the

manufacturers.

r e f e r e n c e s

1. Sadowsky SJ. An overview of treatment considerations foresthetic restorations: a review of the literature. JournalProsthetic Dentistry 2006;96:433–42.

2. Puckett AD, Fitchie JG, Kirk PC, Gamblin J. Direct compositerestorative materials. Dental Clinics of North America2007;51:659–75.

3. Croll TP. Primary incisor restoration using resin-veneeredstainless steel crowns. ASDC Journal of Dentistry for Children1998;65:89–95.

4. Portalier L. Composite smile designs: the key to dentalartistry. Current Opinion in Cosmetic Dentistry 1997;4:81–5.

5. Poole DFG, Newman HN, Dibdin GH. Structure and porosityof human cervical enamel studied by polarizing microscopyand transmission electron microscopy. Archives of OralBiology 1981;26:977–82.

6. Wozniak WT, Fan PL, McGill S, Moser JB, Stanford JW. Colorcomparisons of composite resins of various shadedesignations. Dental Materials 1985;1:121–3.

7. Swift EJ, Hammel SA, Lund PS. Colorimetric evaluation ofVita shade resin composites. International Journal ofProsthodontics 1994;7:356–61.

8. Yap AU, Bhole S, Tan KB. Shade match of tooth coloredrestorative materials based on a commercial shade guide.Quintessence International 1995;26:697–702.

9. Yap AU, Tan KB, Bhole S. Comparison of aesthetic propertiesof tooth-colored restorative materials. Operative Dentistry1997;22:167–72.

j o u r n a l o f d e n t i s t r y 3 7 s ( 2 0 0 9 ) e 2 7 – e 3 3 e33

10. Vichi A, Ferrari M, Davidson CL. Color and opacity variationsin three different resin-based composite products afterwater aging. Dental Materials 2004;20:530–4.

11. Ikeda T, Sidhu SK, Omata Y, Fujita M, Sano H. Color andtranslucency of opaque-shades and body-shades ofresin composites. European Journal of Oral Sciences2005;113:170–3.

12. Kamishima N, Ikeda T, Sano H. Color and translucency ofresin composites. Dental Materials 2005;24:428–32.

13. Paravina RD, Kimura M, Powers JM. Color compatibility ofresin composites of identical shade designation.Quintessence International 2006;37:713–8.

14. Park S, Lee Y. Shade distribution of commercial resincomposites and color difference with shade guide tabs.American Journal of Dentistry 2007;20:335–9.

15. Lee YK, Lu H, Powers JM. Measurements of opalescence ofresin composites. Dental Materials 2005;21:1068–74.

16. Paravina RD, Ontiveros JC, Powers JM. Curing-dependentchanges in color and translucency parameter of compositebleach shades. Journal of Esthetic and Restorative Dentistry2002;14:158–66.

17. Paravina RD, Ontiveros JC, Powers JM. Accelerated agingeffects on color and translucency of bleaching-shadecomposites. Journal of Esthetic and Restorative Dentistry2004;16:117–26.

18. Paravina RD, Powers JM. Esthetic color training in dentistry.1st ed. St Louis: Mosby; 2004. p. 19.

19. Inokoshi S, Burrow MF, Kataumi M, Yamada T, Takatsu T.Opacity and color changes of tooth-colored restorativematerials. Operative Dentistry 1996:73–80.

20. Ragain Jr JC, Johnston WM. Color acceptance of direct dentalrestorative materials by human observers. Color Research &Application 2000;25:278–85.

21. Vieira GF, Arakaki Y, Caneppele TMF. Spectrophotometricassessment of the effects of 10% carbamide peroxide onenamel translucency. Brazilian Oral Research 2008;22:90–5.

22. Yu B, Ahn J-S, Lee Y-K. Measurement of translucency oftooth enamel and dentin. Acta Odontologica Scandinavica2009;67:57–64.

23. Vargas MA, Lund P, Fortin JD. Opacity and translucency ofenamel and dentin. Journal of Dental Research 1994;73:320.[abstract #1747].