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

Translucency and colour masking ability of hybrid CAD/CAM materials with different thicknesses: in vitro study

OBJECTIVE

To evaluate effect of material thickness and translucency of two different hybrid CAD/CAM materials on their masking ability.

MATERIALS AND METHODS

40 rectangular-shaped specimens (12 × 14 mm) were obtained from Vita Enamic and Grandio blocks at 0.5 and 1 mm-thick (n = 10/group). Colour parameters of specimens were measured on PMMA tooth-coloured replica backgrounds (A2, C4) and black, white backings using dental spectrophotometer. Translucency parameter (TP) and masking ability (∆E00) values of tested materials with 0.5, and 1 mm thicknesses were calculated. Quantitative variables were compared between groups using student t-test.

RESULTS

TP and ∆E00 significantly decreased as thickness of tested materials increased. Grandio showed significantly higher TP values. There were significantly lower ΔE00 values for Vita Enamic compared to Grandio at 1 mm thickness and inversely insignificant at 0.5 mm. The 0.5 mm-thick ∆E00 of tested materials was above clinical acceptability threshold, whereas, 1 mm-thick did not exceed showing better masking properties.

CONCLUSIONS

Thickness is more effective for colour masking than translucency. In thin thickness, the masking ability is less effective, irrespective of tested materials. Translucency of tested materials was affected by their composition. Both hybrid CAD/CAM materials are promising alternatives for masking dark discolouration at 1 mm-thick.

A Scoping Review on the Polymerization of Resin-Matrix Cements Used in Restorative Dentistry

In dentistry, clinicians mainly use dual-cured or light-cured resin-matrix cements to achieve a proper polymerization of the organic matrix leading to enhanced physical properties of the cement. However, several parameters can affect the polymerization of resin-matrix cements. The main aim of the present study was to perform a scoping review on the degree of conversion (DC) of the organic matrix, the polymerization, and the light transmittance of different resin-matrix cements used in dentistry. A search was performed on PubMed using a combination of the following key terms: degree of conversion, resin cements, light transmittance, polymerization, light curing, and thickness. Articles in the English language published up to November 2022 were selected. The selected studies' results demonstrated that restorative structures with a thickness higher than 1.5 mm decrease the light irradiance towards the resin-matrix cement. A decrease in light transmission provides a low energy absorption through the resin cement leading to a low DC percentage. On the other hand, the highest DC percentages, ranging between 55 and 75%, have been reported for dual-cured resin-matrix cements, although the polymerization mode and exposure time also influence the DC of monomers. Thus, the polymerization of resin-matrix cements can be optimized taking into account different parameters of light-curing, such as adequate light distance, irradiance, exposure time, equipment, and wavelength. Then, optimum physical properties are achieved that provide a long-term clinical performance of the cemented restorative materials.

Comparing the color match of monolithic CAD-CAM dental ceramics with the VITA Classical shade guide

STATEMENT OF PROBLEM

Matching the shade selected and the final color of a ceramic restoration is challenging, and studies on matching monolithic ceramics to the shade selected are lacking.

PURPOSE

The purpose of this in vitro study was to compare the color match of monolithic lithium disilicate (LDS), zirconia-reinforced lithium silicate (ZLS), presintered zirconia-reinforced lithium silicate (PS-ZLS), polymer-infiltrated ceramic network (PICN), and multilayer zirconia with the 3 modes of the VITA Classical shade guide.

MATERIAL AND METHODS

This study was performed on 50 rectangular plates (14×12×1 mm) of 5 types of ceramics with A2 shade (n=10). Zirconia specimens were evaluated in 3 locations: incisal, medial, and cervical thirds. The color coordinates of the specimens of all 7 groups were measured on #3 and #8 Ivoclar Natural Die Color material by using a reflective spectrophotometer. The color coordinates of A2 VITA shade were measured in 5 modes: without backing placed in specimen holder, shade tab on the backgrounds #3 and #8, and 1-mm-thick shade tab on the backgrounds #3 and #8. The color difference of each specimen with 3 modes of A2 shade (without backing and on similar backgrounds) was calculated by using the ΔE00 formula, and comparison among groups was performed by using 2-way ANOVA and Tamhane post hoc tests. The comparison of ΔE00 between the values obtained from backgrounds #3 and #8 was performed by using the independent t test (α=.05).

RESULTS

In both backgrounds, statistically significant differences were found between the studied groups and VITA shade (P<.001). In most situations, the amount of color difference was lowest for the "shade tab on the backgrounds" mode. On background #3, the highest color difference was related to ZLS (6.48 ±0.23), and the lowest values were observed in the PICN group (1.02 ±0.31). On background #8, the highest color difference was related to ZLS compared with the "without backing" mode (8.62 ±0.27), and the lowest values were reported for ZLS compared with the "shade tab on the backgrounds" mode (1.27 ±0.44). The independent t test showed a statistically significant color difference on the 2 different backgrounds for all situations (P<.001).

CONCLUSIONS

Color selection of monolithic ceramics with the VITA Classical shade guide is improved by placing the VITA tabs on a similar background. Background color has a significant effect on the final shade of the monolithic ceramics. Choosing the correct color for LDS, ZLS, and PS-ZLS requires more care than for PICN and zirconia.

Effects of background color and thickness on the optical properties of CAD-CAM resin-matrix ceramics

STATEMENT OF PROBLEM

Information regarding the masking ability of computer-aided design and computer-aided manufacture (CAD-CAM) resin-matrix ceramic materials with different compositions is scarce.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of background color and thickness on the optical properties (color and translucency) of CAD-CAM resin-matrix ceramics.

MATERIAL AND METHODS

Twelve rectangular specimens were fabricated at a different thickness (1, 1.5, and 2 mm) (n=12) from each of the resin-matrix ceramic materials: Shofu block (SB), Lava Ultimate (LU), CERASMART (CS), VITA ENAMIC (VE), Crystal Ultra (CU), and the VITABLOCS Mark II feldspathic ceramic (VB). The color of the specimens over amalgam, titanium, enamel, and dentin backgrounds was measured with a spectrophotometer, and the color differences (ΔE∗ab) were calculated by using the Commission Internationale de l'Eclairage (CIE) 76 formula. The difference in color of the specimen over the black and white backgrounds was used to calculate the translucency parameter (TP). ANOVA was used to statistically test whether material, background, and thicknesses influenced ΔE∗ab and TP values. Post hoc comparisons were performed to determine the significant difference among the groups (α=.05).

RESULTS

The interaction with 2 between factors demonstrated that the material was a factor that significantly influenced ΔE∗ab (P<.001). The highest mean ±standard deviation of ΔE∗ab was recorded in the combination of VB material and 2-mm thickness (1.84 ±0.37), and the lowest with CS material with 1.5-mm thickness (0.47 ±0.24). The type of material and specimen thickness significantly influenced TP (P<.001). The highest and lowest mean ±standard deviation of TP were recorded for the 1-mm-thick CS (14.20 ±0.90) and 2-mm-thick SB (4.91 ±0.42) specimens, respectively.

CONCLUSIONS

CERASMART resin-matrix ceramic and VITABLOCS Mark II feldspathic ceramic exhibited high and low masking abilities over the investigated background substrates, respectively. However, irrespective of the thickness, all study materials exhibited acceptable masking abilities.