Masking ability of indirect restorative systems on tooth-colored resin substrates
Introduction
Considering dental color appearance, natural-looking restorations require adequate shade matching and blending optical properties from adjacent natural teeth [1,2]. The final appearance of esthetic indirect restorations is influenced by factors such as composition and microstructure [2,3] optical properties [4] and layering of the ceramic systems [5], surface texture and material thickness [6,7], and color and opacity of luting agents [6,7]. In addition, the tooth preparation (substrate) color is major factor influencing on final color and appearance of indirect restorations [1,8].
In clinical situations requiring restoration of non-vital discolored teeth or metal abutment structures, dentists are confronted to choose materials to mask the underlying color producing an adequate esthetic restoration. That is one of the greatest challenges in esthetic dentistry [8,9]. Additionally, the ceramic framework translucency was recognized as a key factor determining the optical characteristics of all-ceramic restorations [10].
There are many CAD–CAM ceramic systems combining strength and esthetics to cover different clinical situations. Lithium disilicate-based glass-ceramic has generated considerable interest for restorative dentistry mostly because of adequate strength (350–450 MPa) [8] and optical properties [4]. Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is still the strongest and toughness ceramic ever used in dentistry [8,11] but its limited translucency [12] and the veneer porcelain chipping [11] are major disadvantages for veneered Y-TZP systems [13]. To avoid such problems, monolithic zirconia restorations using highly-translucent Y-TZP were introduced to dentistry as an alternative to porcelain-fused-to-zirconia restorations [[14], [15], [16]]. In addition, in 2011, a new technique was developed (CAD-on) to produce multilayered all-ceramic restorations (zirconia framework and lithium disilicate-based veneer fused together using a glass-ceramic) manufactured using the CAD–CAM technology [17,18]. A polymer-infiltrated ceramic-network (PICN) material with a dominant ceramic-network interconnected to a polymer-based matrix was introduced as an attempt to combine good material properties from polymers and ceramics [19,20].
Different parameters have been used to evaluate the masking ability of restorative materials, such as: contrast ratio (CR) [21,22] and translucency parameter (TP) [9,10,[21], [22], [23], [24], [25]]. In addition, CIELAB color space and its associated CIELAB () and CIEDE2000 () total color difference formulas have been extensively used for color research in dentistry and, as a consequence, [7,9,10,24,[26], [27], [28], [29]] or [23,25] have been also used to evaluate the masking ability of restorative materials cemented on colored substrates. Yet, the International Organization for Standardization (ISO/TR 28642:2016) [30] states that color differences should be assessed on the basis of 50:50% acceptability (AT: = 2.66 and = 1.77) and 50:50% perceptibility (PT: = 1.22 and = 0.81) thresholds [31]. Thus, if the color difference between two specimens is at or below PT, it represents an excellent match; if the difference is between PT and AT, it represents an acceptable match; and if the difference is above AT, it represents an unacceptable match.
As the masking ability of indirect restorative systems (IRS) is critical for acceptable esthetic restorations on discolored substrates, the objective of this study was to evaluate the masking ability of IRS on different tooth-colored resin substrates using CIELAB () and CIEDE2000 () metrics for color differences and the translucency parameters (CIELAB-based and CIEDE2000-based ) for measuring the translucency of non-cemented IRS specimens. The hypotheses tested were that (1) color differences from same IRS cemented on different color of substrate are not acceptable (above AT), and (2) translucency varies with structural characteristics.
Section snippets
Material and methods
This in-vitro study used five indirect restorative systems (Table 1) being three monolithic structures (LDC, YZW and PICN), one bilayer structure (YLD-T) and one trilayer structure (CAD-on).
Results
CIELAB color coordinates of IRS are shown in Fig. 1. Fig. 2(a and b) show mean and standard deviation values of translucency parameter (TP and ) for different indirect restorative systems. The behavior of all systems was similar for both translucency parameters. PICN and YLD-T showed, respectively, the greatest and the lowest TP values (p ≤ 0.05). In addition, LDC and CAD-on showed similar TP values (p > 0.05) (Fig. 2(a and b)).
Table 2 shows mean and standard deviation values of color
Discussion
The present study was designed to evaluate the masking ability of indirect restorative systems manufactured by CAD–CAM technology, except for the veneer layer of YLD-T structure. Therefore, monolithic (LDC — lithium disilicate-based glass-ceramics, YZW — zirconia, and PICN — polymer-infiltrated ceramic-network), bilayer (YLD-T — zirconia framework veneered with feldspathic ceramic) and trilayer (CAD-on — zirconia framework and lithium disilicate-based veneer fused with a glass-ceramic)
Conclusions
Within the above mentioned limitations of the present in-vitro study, it can be stated that resin-cemented YLD-T on different tooth-colored substrates showed less translucency and color differences below acceptability threshold, indicating the best masking ability among the evaluated systems.
Acknowledgments
This work was partially supported by CNPq do Brasil [grant #302587/2017-9]; CAPES do Brasil [grants PNPD 42009014007P4 and PROSUC 88887.147565/2017-00]; “Junta de Andalucía” (Spain) [grant number JA TEP-1136] and Spanish Ministry of Economy and Competitiveness and European Regional Development Fund (ERDF) [grant number MAT2013-43946R]. The authors thank Dr. Dileta Cecchetti for the support in the statistical analysis and the dental laboratory “Coral”.
References (51)
- et al.
Colour parameters and shade correspondence of CAD/CAM ceramic systems
J Dent
(2015) - et al.
Optical properties of CAD–CAM ceramic systems
J Dent
(2014) - et al.
Porcelain thickness and cement shade effects on the colour and translucency of porcelain veneering materials
J Dent
(2013) - et al.
Translucency and biaxial flexural strength of four ceramic core materials
Dent Mater
(2008) - et al.
In vitro performance of full-contour zirconia single crowns
Dent Mater
(2012) - et al.
Edge chipping resistance of ceramics bonded to a dentine analogue
J Mech Behav Biomed Mater
(2019) Making yttria-stabilized tetragonal zirconia translucent
Dent Mater
(2014)- et al.
Reliability and failure behavior of CAD-on fixed partial dentures
Dent Mater
(2016) - et al.
Reliability and mode of failure of bonded monolithic and multilayer ceramics
Dent Mater
(2017) - et al.
Characterization of a polymer-infiltrated ceramic-network material
Dent Mater
(2014)
Effect of abutment tooth color, cement color, and ceramic thickness on the resulting optical color of a CAD/CAM glass-ceramic lithium disilicate-reinforced crown
J Prosthet Dent
Effect of coping thickness and background type on the masking ability of a zirconia ceramic
J Prosthet Dent
Translucency thresholds for dental materials
Dent Mater
Color measurement in dentistry
J Dent
Visual and instrumental shade matching using CIELAB and CIEDE2000 color difference formulas
Dent Mater
Color difference thresholds in dental ceramics
J Dent
Dental ceramics: a CIEDE2000 acceptability thresholds for lightness, chroma and hue differences
J Dent
Lightness, chroma and hue differences on visual shade matching
Dent Mater
Optical behavior of dental zirconia and dentin analyzed by Kubelka-Munk theory
Dent Mater
Color and translucency of zirconia ceramics, human dentine and bovine dentine
J Dent
Relative translucency of six all-ceramic systems. Part I: core materials
J Prosthet Dent
Visual and instrumental agreement in dental shade selection: three distinct observer populations and shade matching protocols
Dent Mater
Optical behavior of current ceramic systems
Int J Periodontics Restor Dent
Opacity control using pressed ceramic: part 1. Material selection
Quintessence Dent Technol
Opacity control using pressed ceramic: part 2. Layering guidelines
Quintessence Dent Technol
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