Impact of background on color, transmittance, and fluorescence of leucite based ceramics

Digital image analysis of fluorescence of ceramic veneers with different ceramic materials and resin cements

The objective of this study was to analyze the effect of the type of ceramics and resin cements on the fluorescence of ceramic veneers under the 405 nm UV-light by digital imaging. One hundred and ninety-two veneers were fabricated using three types of ceramics (IPS e.max CAD, IPS Empress CAD, and Zenostar). Eight pieces of substrates were made of resin-nano-ceramic (Lava Ultimate). The level of fluorescence for each sample cemented with the substrate using three kinds of resin cements (RelyX U200, Variolink N, and Choice 2) was analyzed by using histogram data of luminosity from Adobe Photoshop software. Furthermore, the fluorescence values were evaluated by two-way ANOVA and Tukey's test. The highest fluorescence values were observed for the IPS e.max CAD cemented with Choice 2 cement, followed by IPS Empress CAD, and Zenostar the lowest. The final fluorescence intensity of ceramic veneer is affected by ceramic materials and resin cements.

The Effect of Feldspathic Thickness on Fluorescence of a Variety of Resin Cements and Flowable Composites

(1) Background: The shade of resin-based materials and ceramic thickness influence the optical color of laminate restorations. The purpose of this study is to evaluate—in vitro—the effect of resin-based cement shade and ceramic thickness on fluorescence of feldspathic laminate veneers; (2) Methods: 180 samples of feldspathic ceramic A2 shade with two different thicknesses (0.5 and 0.8 mm) were obtained. The samples were cemented to composite resin substrates with one of the following materials in different shades (n = 10): resin cement (Variolink Esthetic in Light, Neutral and Warm shades; or RelyX Veneer in B0.5 /white, Translucent and A3 Opaque/yellow opaque shades); flowable composite resin (G-aenial Flo in A2 and A3 shades) or a pre-heated composite resin (Filtek Supreme XTE, A3 body shade). The fluorescence spectra were obtained by means of a spectrofluorometer. Two-way ANOVA, Tukey, and Student’s t-tests were performed (α = 0.05); (3) Results: Fluorescence values were significantly influenced by the resin-based agent tested (p < 0.001), the thickness of ceramic (p < 0.001), and their interaction (p < 0.001). The lowest fluorescence values were achieved by RelyX Veneer resin cement regardless its shade and the ceramic thickness; (4) Conclusions: both the shade of resin-based agent and the feldspathic ceramic thickness influenced the fluorescence of laminate restorations.

Translucency of a Dental Porcelain Mixed by Two Ceramic Slurry Methods: A Bayesian Comparison

Background

The ceramics industry produces porcelain pastes using a controlled ratio of water and porcelain powder. Two methods are used to produce a dental porcelain paste: one-step mixing or incremental mixing.

Objective

To evaluate the optical properties of a feldspathic dental ceramic using two different ceramic paste preparation methods using a Bayesian approach.

Materials and Methods

Two groups of feldspathic porcelain discs, an incremental mixing group (n = 40) and a one-step mixing group (n = 40), were assessed. Groups were evaluated using spectrophotometry, and the translucency parameter (TP) of each sample was calculated. Surfaces were characterized by AFM and SEM. Statistical analysis was performed using a Bayesian approach.

Results

Translucency parameter values of the incremental mixing group ranged from 1.65 to 3.41, while values for the one-step mixing group ranged from 3.62 to 5.74, this difference being statistically significant. The lowest roughness was obtained on the surface of discs in the one-step mixing group.

Conclusions

Feldspathic porcelain with lower translucency and higher roughness was obtained using the incremental mixture method.

Influence of zirconia/glass veneer thickness and implant abutment material on the final shade of implant restorations

Aim

The aim of this study was to investigate the combined effect of ceramic material, ceramic thickness, and implant abutment background to the final color of restorations.

Settings and Design

This was a comparative in vitro study.

Materials and Methods

Three different types of monolithic and porcelain-veneered zirconia disc-shaped specimens (Prettau Anterior, VITA YZ ST, and VITA YZ HT) were prepared in A3 shade with two different thicknesses (1 mm and 1.5 mm) (n = 10). Each zirconia material was made of 4-mm thickness as a control specimen of each monolithic zirconia type, and 4-mm thick veneering ceramic (VITA VM9 Base Dentine) was made as a control for veneered zirconia groups. Three simulated implant abutments were fabricated from titanium, white-shaded and yellow-shaded zirconia. The zirconia specimens were placed on different abutment backgrounds, and the color difference (ΔE) between experimental and control specimens was measured.

Statistical Analysis Used

The three-way ANOVA and the Scheffé test were used for data analysis (α = 0.05).

Results

The mean ΔE values between two thicknesses were significantly different in every background for all zirconia materials. The ΔE values of zirconia specimens on yellow zirconia were lower than those of other abutments. The clinically acceptable ΔE value (ΔE <3) was found in some monolithic zirconia specimens on white-shaded and yellow-shaded abutments, while the ΔE value is approximately 3 or less in all 1.5-mm thick porcelain-veneered zirconia groups.

Conclusions

Different zirconia materials on implant abutments affected the final color of restorations. To achieve satisfactory color, the minimum thickness of zirconia restorations should be at least 1.5 mm on yellow zirconia abutment.

[Fluorescence of zirconia-based dental ceramic materials]

The review contains information about the fluorescent properties of natural teeth, fluorescent additives, fluorescent liquids for staining zirconium dioxide, fluorescent powders, pastes, glazes, and cements for zirconia, methods for measuring fluorescence. Factors affecting the fluorescent properties of ceramics are also reported.

Masking ability of bleach-shade resin composites using the multilayering technique

OBJECTIVE

Evaluate the masking ability of bleach-shade resin composites applied by multilayering techniques over colored substrates.

MATERIALS AND METHODS

Disc-shaped specimens were fabricated from bleach-shade resin composites using different multilayering techniques. Substrates were produced in opaque ceramic discs simulating colored substrates (A2, A3, A3.5, C2, C3, C4) and a bleached tooth (0M1). Color coordinates were obtained using a reflectance spectrophotometer. Color difference was calculated by CIEDE2000 using coordinates of 0 M1 ceramic as standard reference. Data were analyzed by one-way ANOVA and Tukey's post-hoc test (p ≤ 0.05). Masking ability interpretation was based on perceptibility and acceptability thresholds.

RESULTS

All combinations presented ΔE₀₀ above the acceptable threshold (ΔE₀₀ >1.8), ranging from 2.49 to 7.42, regardless of the restorative system, multilayering strategy or substrate color. Multilayering combinations placed over A2, A3 and A3.5 were moderately (1.8<ΔE₀₀ ≤3.6) and clearly unacceptable (3.6<ΔE₀₀ ≤5.4), combinations associated with C2, C3 and C4 were clearly unacceptable and, extremely unacceptable (ΔE₀₀ >5.4). Lower ΔE₀₀ was observed for combinations with 0.5 mm extra white enamel layer (2.49), or 1.0 mm white dentin layer (2.69), over A2 and A3.5 substrates. Lightness difference showed the greatest contribution to ΔE₀₀ .

CONCLUSIONS

Bleach-shade resin composite systems applied by the multilayering technique were not able to ensure effective masking ability.

CLINICAL SIGNIFICANCE

Bleach-shade resin composites applied with different combinations of the multilayering technique were not effective in masking colored substrates. Alternative strategies, techniques and dental materials should be explored to obtain acceptable masking.

Evaluation of shade correspondence between current monolithic CAD/CAM blocks and target shade tab by considering the influence of cement shade and restorative material thickness

It was aimed to evaluate shade matching between novel CAD/CAM blocks and the A2 target shade tab by considering the influence of cement shade and restorative material thickness on the chromatic background. A total number of 120 rectangular-shaped specimens were subtracted from four different prefabricated CAD/CAM blocks [Vita Enamic (VE), Lava Ultimate (LU), GC Cerasmart (GC), and Vita Mark II (VMII)]. These specimens had thicknesses of 0.5 mm and 1.0 mm. Three different shades (A2, opaque, and translucent) of dual-polymerized resin cement were chosen. The dentin shade (A3.5) restorative composite foundation was incrementally fabricated in a silicon mold. For control group, the A2 shade tab of the Vitapan classical shade guide was used. Different restorative material-cement-foundation assemblies were generated with optic gel. Color readings were performed by using a clinical spectrophotometer, and CIEDE2000 (ΔE₀₀) formula was used to assess color differences. Data were statistically analyzed (α = 0.05). With increasing thickness, color difference values decreased. Higher mean ΔE₀₀ units were observed in all restorative material sub-groups for 0.5 mm thickness. In TR shade, no statistically significant difference was detected among the mean ΔE₀₀ values of 0.5 mm-thick restorative materials. Color differences in groups 1.0 mm-opaque-LU and 1.0 mm-opaque-GC indicated perceptible but clinically acceptable values (0.8˂ΔE₀₀ ≤ 1.8). The highest and lowest ΔE₀₀ units were observed in the 0.5 mm-A2-VE group (ΔE₀₀ = 7.07) and 1 mm-opaque-GC group (ΔE₀₀ = 1.46), respectively. Luting cement shade, restorative material type, and thickness significantly influenced the resultant color of restoration. Opaque cement on dentin foundation exhibited lower color differences.

Optical properties and colorimetric evaluation of resin cements formulated with thio-urethane oligomers

OBJECTIVE

The aim of this study was to evaluate the color parameters and optical properties of resin cements (RCs) formulated with thio-urethanes (TUs).

MATERIALS AND METHODS

Six TUs were synthesized by combining thiols (pentaerythritol tetra-3-mercaptopropionate [PETMP] or trimethylol-tris-3-mercaptopropionate [TMP]) with di-functional isocyanates (1,6-Hexanediol-diissocyante [HDDI] [aliphatic-AL] or 1,3-bis(1-isocyanato-1-methylethyl) benzene [BDI] [aromatic-AR] or Dicyclohexylmethane 4,4'-Diisocyanate [HMDI] [cyclic-CC]). TUs (20 wt%) were added to a BisGMA/UDMA/TEGDMA matrix. Filler was introduced at 60 wt%. Fluorescence was evaluated through an UV-light emitting equipment. Coordinates L*, a*, and b* were obtained in the black and white reflectance to evaluate the contrast ratio (CR) and translucency parameter (TP₀₀ ). The coordinates obtained from transmittance were used to evaluate lightness (L*), chroma (C*), color difference (ΔE₀₀ ) after 6 month, and whiteness index for Dentistry (WI_D ).

RESULTS

RCs formulated with TUs presented significantly higher CR, and fluorescence (with T_AR). Significantly lower C*, L*, and TP₀₀ (except for P_AR and T_AL) were also observed in RCs containing TUs. ΔE₀₀ were not significant among the materials. WI_D was not influenced.

CONCLUSION

RCs composed by TU oligomers present higher CR and lower translucency. The material also present higher fluorescence depending on the oligomer used.

CLINICAL SIGNIFICANCE

The use of thio-urethanes to formulate resin cements can ensure a luting material with improved potential to mask colored substrates due to the higher contrast ratio and lower translucency obtained. A final higher fluorescence of restoration is also expected with the use of specific oligomer.