Relevant optical properties for direct restorative materials
Introduction
Traditionally, composites are designed to support masticatory load (posterior teeth) or to produce esthetically beautiful (anterior teeth) restorations [1]. Manufacturers of restorative resin-based composites may manipulate the resin matrix and, mainly, the particle size and shape to improve material properties [1], [2], [3], [4], [5], [6].
With the development of nanotechnology, dental nanocomposites have become available, allowing for significant improvements [2]. Nanofillers range from 1 to 100 nm2, which is below the wavelength of visible light (380–780 nm). This characteristic allows the fabrication of materials unable to scatter or absorb the visible light, named highly translucent materials [2], [7]. To obtain these nanocomposites, two types of nanofillers have been synthesized: nanometric particles (nanomers) and nanoclusters. The former are mainly monodisperse, non-aggregated and non-agglomerated zirconia (2–20 nm) or silica particles (2–75 nm) [2], [7]. Due to reduced particle size, dental nanocomposites exhibit very good resistance to wear and fracture, along with good sculptability [2]. Nanofillers also offer advantages in optical properties. They can provide low opacity in low staining dental composites, allowing for a wide range of shades and opacities [2].
When light strikes a semi-translucent object, four phenomena can result from this interaction: (1) specular light reflection and (2) diffuse light reflection at the object surface, (3) absorption and scattering of light within the object structure, and (4) transmission of the light flux through object structure [6], [8], [9]. The light resulting from the interaction of these phenomena will reach the observer eyes with the object color information [6].
Previous studies reported that background color affects the perceived color of dental composites [10], [11], suggesting that translucency should not be ignore in esthetic dentistry. Highly translucent and low staining composites, which usually have nanoparticles, allow the perception of the background color through the material [2].
Scattering changes with the wavelength of incident light and it is mostly determined by particle size. Absorption and reflectance also vary with the wavelength of incident light and the nature of colorant pigments [8]. Different esthetic restorative resin systems work with different color and translucency effects and these characteristics should be considered when selecting the restorative material.
Actually, most direct restorative materials offer whitened shades, suggesting they are brighter and more opaque than the classic dental shades [11]. Opalescent materials, such as dental enamel, are able to scatter shorter wavelengths of light. Under reflected light, they appear blue, whereas under transmitted light, they appear brown/yellow [2], [12], [13].
CIELAB color space is mostly used in dental color research. This space consists of three axes: L* (lightness), a* (red-green axis) and b* (yellow-blue axis). Chromatic attributes related to visual perception, such as chroma (C*) and hue (h°), are obtained from a* and b* coordinates [14]. Therefore, managing the optical properties of esthetic restorative materials is essential to fabricate natural-looking esthetic restorations. Thus, the purpose of this study was to evaluate the color and optical properties of translucent and whitened shades in relation to their original E and B shades. The study tested the hypotheses that (1) direct restorative composite shades present the optical properties suggested by the manufacturer, and (2) there is a significant difference in color and optical properties between the whitened shades and the corresponding original (E and B) shades from a direct restorative composite system.
Section snippets
Samples
An esthetic resin composite restorative system (FS-Filtek™ Supreme XTE, 3M ESPE, St. Paul, MN, USA), based on layering technique [15], [16], was evaluated (Table 1).
Specimens (10 mm in diameter and 1 mm in thickness) were fabricated (n = 3) with all composite shades. Composite material was packed into an adaptable micrometer metal mold (Smile Line, St-Imier, Switzerland) pressed with a mylar strip and a glass slide. All samples were light activated (Bluephase®, Ivoclar Vivadent, Schaan,
Spectral reflectance and color
Fig. 1 shows spectral distribution of reflectance for a single shade (A2) of different translucency (E, B and D shades) and one representative shade from WhE, WhB and T shades. All shades were not included because they showed overlapped values. T shades showed different spectral behavior from other shades (84.41% ≤ VAF ≤ 93.95%). The remaining shades showed similar spectral behavior (VAF values from 97.46% to 99.92%).
Mean values and standard deviation for the color coordinates L*, a*, b*, C* and h°
Discussion
This study evaluated color and optical properties of different shade classes used for direct restorative resin-based composites. It has been reported that the majority of teeth matches to shade A from Vita Classical shade system [28], therefore the present study evaluate this group of shade from the composite system (FS).
Optical properties such as reflectance, transmittance, scattering and absorption coefficients depend on the wavelength of light [20]. Previous studies performed on dental
Conclusions
Within the limitations of the present study, results suggest that the optical behavior of T shades is different from other shades. Considering the whitened shades, WhB shades showed different color and optical properties (including TP and W*) than their corresponding B shades. WhE shades showed similar mean W* values but higher mean T% and TP values than E shades.
Acknowledgments
The authors acknowledge funding support from research projects JA TEP-1136 from “Junta de Andalucía”, Spain, MAT2013-43946R from the Spanish Ministry of Economy and Competitiveness, CNPq do Brasil (304995/2013-4) and CAPES do Brasil (PNPD 42009014007P4). The authors also acknowledge 3M ESPE for providing the resin-based composite used in this study.
References (38)
Resin composite-state of the art
Dent Mater
(2011)- et al.
Characterization of nanofilled compared to universal and microfilled composites
Dent Mater
(2007) Influence of scattering/absorption characteristics on the color of resin composites
Dent Mater
(2007)- et al.
Color and contrast ratio of resin composites for whitened teeth
J Dent
(2009) - et al.
Measurement of opalescence of resin composites
Dent Mater
(2005) - et al.
Opalescence of all-ceramic core and veneer materials
Dent Mater
(2009) - et al.
Accuracy of Kubelka-Munk reflectance theory for dental resin composite material
Dent Mater
(2012) - et al.
Color and translucency of zirconia ceramics, human dentine and bovine dentine
J Dent
(2012) - et al.
The effect of a coupling medium on color and translucency of CAD-CAM ceramics
J Dent
(2013) - et al.
Color and translucency in silorane-based resin composite compared to universal and nanofilled composites
J Dent
(2010)
Optical behavior of dental zirconia and dentin analyzed by Kubelka-Munk theory
Dent Mater
Optical properties of base dentin ceramics for all-ceramic restorations
Dent Mater
Optical properties of CAD-CAM ceramic systems
J Dent
Influence of filler on the difference between the transmitted and reflected colors of experimental resin composites
Dent Mater
Influence of filler distribution on the color parameters of experimental resin composites
Dent Mater
Double layer effect and other optical phenomena related to esthetics
Dent Clin North Am
Restorative materials – composites and polymers
Effect of filler content and size on properties of composites
J Dent Res
Resin composite restorative materials
Aust Dent J
Cited by (39)
Relevant optical properties for gingiva-colored resin-based composites
2022, Journal of DentistryCitation Excerpt :Translucency depends on the relative ratio between the light scattering and light absorption phenomena occurring within the material. For tooth colored resin based composites the scattering is mainly determined by the filler particles' size [26] and shape [45], while absorption is linked to the resin matrix and the presence and nature of colorant pigments [39]. These factors determine the difference between the refractive indices of the organic matrix and the filler.
Color prediction of layered dental resin composites with varying thickness
2022, Dental MaterialsReflectance and color prediction of dental material monolithic samples with varying thickness
2022, Dental MaterialsCitation Excerpt :All the samples used are translucent at clinically relevant thicknesses, therefore a black background was used in order to simulate the darkness in the oral cavity. A spectroradiometer was used to measure all the specimens, since it is considered the gold standard device for the evaluation of the colorimetric and optical properties of dental materials [37–40,41,42], which ensures the precision of our measurements against other commercial dental devices used in clinical scenarios and other studies, such as colorimeters, spectrometers and spectrophotometers [2,3,29]. Complementary, for the evaluation of the color differences, the CIEDE2000 formula was used since it is widely implemented in color dental research [43,26,19] and it has proven to fit more accurately with visual perception [35].