Effect of cement color and tooth‐shaded background on the final color of lithium disilicate and zirconia‐reinforced lithium silicate ceramics: An in vitro study

Validation of the pink esthetic score/white esthetic score at single tooth-supported prostheses in the esthetic zone: A randomized clinical trial

OBJECTIVES

To validate the reproducibility and inter/intra-observer variability of the Pink Esthetic Score/White Esthetic Score (PES/WES) of single tooth-supported prostheses in the maxillary esthetic zone (13-23).

MATERIALS AND METHODS

Forty-five patients were randomly assigned to one of the three treatment options (15 patients per group) receiving each one a different crown type: Porcelain fused to metal (PFM), monolithic zirconia, and lithium disilicate. Eight observers from each of four different specialties (Prosthodontists, Orthodontists, Periodontists, and Oral Surgeons) were recruited and assessed twice and four weeks apart (i.e., T1 and T2) 45 photographs of the single tooth-supported prosthesis using PES/WES and compared them with contralateral teeth.

RESULTS

According to the ANOVA and post hoc tests, the zirconia crown type obtained the highest mean score by all observers, with a mean value of 16.70 ± 2.94. The prosthodontists and oral surgeons assigned the lowest mean score to PFM crowns, 13.03 ± 3.47 and 13.80 ± 3.17, respectively. Notably, the prosthodontists awarded the highest scores, specifically 17.50 ± 2.81 for the zirconia crowns. Intraobserver agreement was calculated utilizing the paired t-test. Pairwise comparisons between observers of different specialties revealed significant intraobserver agreement. Interclass correlation coefficient (ICC) scores were statistically significant among four specialties. No difference was detected concerning the interobserver agreement.

CONCLUSIONS

The PES/WES index remains consistent across various observers from different specializations, yielding uniform results in the overall esthetic evaluation. Consequently, in light of the presented preliminary positive results, its use might also be considered for the esthetic assessment of single-tooth-supported prostheses.

CLINICAL SIGNIFICANCE

The PES/WES index may be employed clinically to evaluate single tooth-supported prostheses as it emerged as a reproducible esthetic scoring system.

Quantitative examination of factors influencing the colour reproduction ability of lithium disilicate glass-ceramics

BACKGROUND

Effects of ceramic translucency, layer thickness, and substrate colour on the shade of lithium disilicate glass-ceramic restorations proved to be significant in several studies, however, quantitative, numerical results on the relationship between the colour difference and these parameters are still lacking. The purpose of this in vitro study was to quantitatively determine how the colour reproduction ability of a lithium disilicate glass-ceramic is affected by its translucency, layer thickness, and substrate colour.

METHODS

Ceramic samples were prepared from A2 shade IPS e.max CAD blocks with high and low translucencies (HT and LT) in a thickness range of 0.5-2.5 mm (+/- 0.05 mm). Layered samples were acquired utilizing composite substrates in 9 shades; transparent try-in paste was used. The spectral reflectance of the specimens was assessed under D65 standard illumination with a Konica Minolta CM-3720d spectrophotometer. The CIEDE2000 colour difference (ΔE00) between two samples was analysed using perceptibility and acceptability thresholds set at 50:50%. Statistical analysis involved linear regression analysis and the Kruskal-Wallis test.

RESULTS

An increase in the thickness of 0.5 mm reduced the ΔE00 of the HT samples to 72.8%, and that of the T samples to 71.1% (p < 0.0001). 7 substrates with HT and LT specimens had significantly different results from the mean (p < 0.05). A thickness of 0.5 mm is not sufficient to achieve an acceptable result at any level of translucency, while the low translucency ceramic at a thickness of 1.5 mm gave acceptable results, except for severely discoloured substrates (ND8 and ND9).

CONCLUSIONS

The colour reproduction ability of lithium disilicate glass-ceramics is significantly affected by their translucency, layer thickness, and 7 substrates out of 9 substrates examined.

Resin composite layering on discolored substrates ensures masking ability for monolithic ceramics

OBJECTIVE

the aim of this study was to evaluate the effect of resin composite layering on discolored substrates to obtain masking ability with monolithic ceramics.

MATERIALS AND METHODS

Four groups (n = 8) of computer-aided design/computer aided manufacturing (CAD/CAM) monolithic ceramics, shade A1, with thicknesses of 1.0 and 1.5 mm, were tested: feldspathic (FC), leucite-reinforced (LC), lithium disilicate-reinforced (LD), and translucent zirconia (5YSZ). Five substrates were used: A1 (used as reference), A3.5, C4, and coppery and silvery metals. The substrates were separated as non-layered or layered (with flowable opaque resin composite (FL), white opaque restorative resin composite (WD), and A1-shaded opaque restorative resin composite (A1D)). Resin composite layers of 0.5 and 1.0 mm were tested. The try-in paste, shade A1, was used as a luting agent. Translucency parameter (TP00 ) was assessed for the ceramics. Color differences (∆E00 ) were assessed for the restorative ceramics and resin composite layers over discolored substrates with the CIEDE2000 formula. The results were compared statistically, and descriptively with acceptability (AT, 1.77) and perceptibility (PT, 0.81) thresholds.

RESULTS

Feldspathic showed the highest TP00 (for both ceramic thicknesses) and LD the lowest (for 1.5 mm of ceramic thickness) (P < 0.001). For substrate A3.5, layering with 1.0 mm of A1D or WD ensured ∆E00 below PT for all ceramics tested (P < 0.001). The use of 0.5 mm of FL or 1.0 mm of A1D associated with ceramics LC, LD, and 5YSZ ensured ∆E00 below AT for substrates C4 and coppery metal (P < 0.001). Silvery background layered with 0.5 mm of FL presented ∆E00 below AT for all ceramics and ∆E00 below PT for lithium disilicate of 1.0 mm of thickness (∆E00  = 0.72).

CONCLUSIONS

Layering severely discolored substrates with selected opaque resin composites ensures masking ability for restoration with CAD/CAM monolithic ceramics.

CLINICAL SIGNIFICANCE

Severely discolored substrates are predictably restored with monolithic CAD/CAM ceramics by performing a previous layering of the substrate with opaque resin composite.

The effects of cement thickness and cement shade on the final color of lithium disilicate crowns

PURPOSE

The aim of this study is to evaluate the effect of resin cement color, cement thickness, and thermocycling on the final color of monolithic lithium disilicate crowns.

MATERIALS AND METHODS

A total of ninety prepared central incisors of typodont teeth were restored with lithium disilicate crowns which have different cement thicknesses (40 µm, 80 µm, and 120 µm) and cement shades (clear, yellow, and white). Color parameters of restorations were measured with a spectrophotometer in three different steps 1) before cementing 2) after cementing and 3) after thermocycling with 10000 cycles. Color differences (ΔE₀₀) were calculated with the CIEDE2000 formula and evaluated according to perceptibility (0.8) and acceptability (1.8) thresholds. The ΔE₀₀ data were analyzed by using two-way ANOVA before and after thermocycling (α = .05).

RESULTS

There was no interaction between the cement shade and the cement thickness factors. After cementation, the mean ΔE₀₀ was under the perceptibility threshold in the group of 40 µm cement thickness and clear cement while it was between the perceptibility and acceptability thresholds (0.8 < ΔE₀₀ < 1.8) for all other groups. After thermocycling, the ΔE₀₀ values were between the perceptibility and acceptability thresholds for all experimental groups. Although there were no significant differences among the groups, thermocycling increased the color difference values.

CONCLUSION

The cementation of restorations with clear, yellow, and white resin cements resulted in color differences with uncemented restorations except for the group cemented with clear cement in 40 µm cement thickness. All study groups revealed perceptible color change after thermocycling.

Comparison of the Color Change of Porcelain Laminate Veneers Produced by Different Materials After Luting with Three Resin Cements

OBJECTIVES

This study aimed to compare color change of porcelain laminate veneers fabricated with two lithium disilicate ceramics and a zirconia-reinforced lithium silicate ceramic material after luting with conventional dual-cure, amine-free dual-cure, or light-cure resin cements using artificial accelerated aging (AAA).

METHODS AND MATERIALS

Ninety noncarious human maxillary central incisors were embedded in autopolymerizing acrylic resin blocks to prepare conventional laminate veneers with incisal coverage. Prepared teeth were randomly divided into 3 groups (n=30) to fabricate laminate veneer restorations using: (1) lithium disilicate ceramic, (2) lithium disilicate ceramic with high-density micronization, and (3) zirconia-reinforced lithium silicate ceramic. Impressions of the preparations were taken with a laboratory scanner. Acquired 3D images were processed into a surface tessellation language file. Data were exported for 3D printing on a printer, and laminate veneers were printed in castable wax resin. Ceramic veneers were heat-pressed after investment according to the manufacturer's recommendations and further divided into three groups (n=10) according to luting cement type: (1) light-cure resin cement, (2) amine-free dual-cure resin cement, and (3) conventional dual-cure resin cement. Color measurements were performed from the middle of each specimen with a spectrophotometer before and after AAA for 300 hours with a total energy of 150 kJ/m2. Color changes were calculated with the CIEDE 2000 (ΔE00) formula. Color differences were assessed using two-way analysis of variance (ANOVA) (α=0.05), and the paired t-test was used to compare the L*, a*, and b* parameters in each group before and after aging.

RESULTS

There were no significant differences between the ceramic groups (p>0.05). The color changes of the materials ranged from 2.26 to 3.13. All materials were above the clinically acceptable limit (ΔE00>1.8). The conventional dual-cure resin cement group showed more color change (p>0.05).

CONCLUSIONS

Color changes were observed in all porcelain laminate veneers after artificial accelerated aging. The zirconia-reinforced lithium silicate veneers showed similar color changes as lithium disilicate veneers; the amine-free dual-cure resin cement showed a similar color change as light-cure resin cement after aging.

Shade matching potential of one-shade resin composites used for restoration repair

To evaluate shade matching ability of one-shade composites used for repair of different resin-based restorative materials. Two one-shade composites or one layering composite of 1 mm thickness were placed over non-aged or aged 3 different base materials of 1 mm thickness to simulate repair. Two millimeters thick base samples were prepared and used for reference (n=12). Shade measurements of reference and repair groups were performed with dental spectrophotometer and color difference (ΔE₀₀) were calculated according to CIEDE2000. Data were analyzed using three-way ANOVA followed by Tukey's test (α=0.05). Regardless of aging and base materials, repairing with layering composite yielded lower ΔE₀₀ than repair of one-shade composites (p<0.05). Repair of non-aged and aged GrandioDisc with any repair composite led to higher ΔE₀₀ values than repair of other base materials (p<0.05). Shade matching performance of one-shade composites for repair of different non-aged or aged resin-based material was not clinically acceptable.

Effect of ceramic and resin cement type on color stability and translucency of ceramic laminate veneers for diastema closure: an in vitro study

To investigate the effect of resin cements on the color stability and translucency of ceramic laminate veneers used for diastema closure. Sixty resin abutments were prepared for ceramic laminate veneers and divided into six groups according to the ceramic type (lithium disilicate, zirconia-reinforced lithium silicate, and translucent zirconia) and the cement type (Variolink Esthetic LC and RelyX Veneer). Color coordinates and translucency were analyzed after cementation and after soaking in the coffee solution. Differences in color and translucency were estimated, and results were statistically assessed (α = 0.05). Ceramic materials showed a significant impact on color changes after soaking in coffee within Variolink Esthetic groups. Translucent zirconia showed the highest color change, followed by zirconia reinforced lithium silicate and lithium disilicate. Ceramic materials showed a significant impact among the RelyX Veneer groups. A significant interaction in color changes was found between ceramic types and cement types after cementation, and after soaking in coffee was found. All groups showed a clinically acceptable difference in translucency parameters after soaking in coffee. The resin cement affects the color and translucency of ceramic laminate veneers used for diastema closure, and ceramic laminate veneers bonded with Variolink Esthetic LC resin cement are more translucent, while ceramic laminate veneers bonded with RelyX Veneer resin are more resistant to coffee staining. The lithium disilicate laminate veneer is more resistant to coffee staining than zirconia reinforced lithium silicate and translucent zirconia laminate veneers used for diastema closure.

Final esthetic result of ceramic restorations cemented with different colors of cement

OBJECTIVE

The purpose of this study is to evaluate the color changes of lithium disilicate ceramics when cemented with different brands of cement by varying the thickness of the ceramic.

MATERIALS AND METHODS

Forty ceramic discs, shade A2, were fabricated with 0.5 and 0.8 mm thickness. Forty composite resin discs, shade A3, were also produced. The ceramic samples were cemented to the composite resin discs, with two colors of resin cement, Neutral and Warm. A spectrophotometer evaluation was made. Translucency and color change analysis was performed by calculating the ΔE. A two-way analysis of variance test and multiple comparisons were performed using the Bonferroni method with a 95% confidence interval.

RESULTS

There are statistically significant differences between the two ceramic thicknesses with different brands of cement (p < .001). In addition, using the translucency analysis it was found that there are statistically significant differences between the two ceramic thicknesses in both types of cement (p < .001).

CONCLUSIONS

The use of different cementation materials on lithium disilicate ceramics appears to have little visible influence at the clinical level. Different ceramic thicknesses have a clinically visible influence on the final restoration color.

Microstructural considerations for novel lithium disilicate glass ceramics: A review

OBJECTIVE

To review the ultrastructural characteristics of novel lithium disilicate based glass ceramics (LDC), how their manufacturing process influences their structure and their clinical use.

OVERVIEW

Lithium disilicate based glass ceramic has been successfully used for indirect restorations ranging from partial tooth coverage up to tooth replacement for over 20 years. It combines esthetic and mechanical properties, unlike any other indirect material which makes it an indispensable part of esthetic and restorative dentistry. Recently, novel LDCs have been introduced to the market. Parameters for their use and their microstructure are still not been widely known. This article will review these materials and highlight with high-resolution scanning electron microscopic images their structural aspects and their resulting clinical relevance.

CONCLUSION

Restorations made from LDCs are reliable and can be predictably used only when proper guidelines and protocols during manufacturing and clinical use are followed. For novel LDCs manufacturing and long-term bonding protocols still must be established. Moreover, novel LDCs machinable blocks should be crystallized or heat-treated after milling for superior performance.

CLINICAL SIGNIFICANCE

With more and newer etchable LDC materials entering the market, clinicians and technicians need to be aware of the differences in manufacturing and the resulting microstructure to ensure a successful treatment outcome that will last.

Optical properties of a novel glass-ceramic restorative material

OBJECTIVE

To examine the optical properties of a dental restorative material manufactured from lithium aluminosilicate ceramic and reinforced with lithium disilicate. Translucency and the optical effects of various supporting materials on color were the primary focus.

METHODS

Five 10 × 10 mm samples were prepared in thicknesses of 0.5, 1.0, 1.5, and 2.0 mm of both high translucency (HT) and low translucency (LT) versions of the material in shade A3. A spectrophotometer was used to measure the illuminance of the samples with black and white backings in order to calculate contrast ratio (CR) and relative translucency parameter (RTP). A baseline relationship between translucency and material thickness was examined and the effects of composite, titanium, and zirconia abutments on color change were studied.

RESULTS

No significant findings were identified for RTP or CR between the HT and LT material, regardless of the material thickness (p = 0.39, p = 0.14, respectively). Regardless of material thickness (HT vs. LT), translucencies (RTP and CR) were significantly different with composite, titanium, and zirconia backings compared to baseline values (p < 0.0001). Titanium had the most significant decrease in translucency compared to composite and zirconia. There was no difference in ΔE00 between the HT and LT materials (p > 0.05) regardless of the backing. Titanium had the most significant effect on color of both materials followed by composite then zirconia (p < 0.0001).

CONCLUSIONS

There is not a clinically significant difference in translucency between the high translucency and low translucency materials. Only zirconia supporting structures produced changes in color that are clinically acceptable.

CLINICAL SIGNIFICANCE

Understanding the optical properties of glass-ceramic restorative materials aids providers in selecting appropriate materials for optimum esthetic outcomes. The lithium-aluminosilicate reinforced with lithium disilicate material does a poor job masking supporting structures and resisting color change.