Level Of Translucency Research Articles

Transparency and translucency indices for 1,525 pictograms from the Aragonese Portal of Augmentative and Alternative Communication

This study investigated the transparency and translucency of 1,525 pictograms from the Aragonese Portal of Augmentative and Alternative Communication (ARASAAC). A total of 521 participants took part in tasks that involved providing the word that best described the meaning of a pictogram or rating the relationship between a pictogram and a verbal label. This process allowed us to obtain indices of transparency (the quality of pictograms that makes their meaning easily “guessable” in the absence of their referent) and translucency (the degree of perceived relationship between the pictogram and its referent when the latter is present) which were further analyzed to assess their reliability and comparability with similar studies. Additionally, the relationship of those indices with various visual and psycholinguistic characteristics was explored, particularly focusing on the match between the original ARASAAC pictogram names and the most frequently provided names by the participants (modal names) for the pictograms. Results showed relatively low levels of transparency, as well as high levels of translucency, with nouns displaying the highest values in both metrics. For transparency and translucency, word imageability and concreteness were the most correlated factors, and, together with age of acquisition, they were the most important features related to the name matching with ARASAAC. The norms derived from this study enhance our understanding of pictogram perception, empowering stakeholders to leverage data-driven insights for the development and implementation of pictographic systems, thus improving cognitive accessibility.

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

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

Translucency and Color Difference of Monolithic Zirconia Restorations: The Effect of Surface Finishing on Background Color

Aim: This study evaluates the effect of different surface finishing procedures on the color and translucency values of monolithic zirconia materials on three different colored composite backgrounds. Materials and Methods: Sixty monolithic zirconia blocks of three different translucency levels were prepared in vitro using computer-aided design/computer-aided manufacturing (CAD/CAM) systems. The correlation between repeat measurements was 0.5, resulting in a sample size of nine samples per group to detect a medium effect size, f = 0.25. Half of the zirconia blocks in each group were subjected to glazing, while the other half were polished ( n = 10). Composite blocks of three different colors were prepared to simulate dental substrates, and the zirconia specimens were placed on these composite backgrounds. The color parameters of the specimens were measured using a spectrophotometer on gray, black, and white backgrounds. Three-way repeated measure ANOVA was used to assess the interaction between the three independent variables (zirconia brand, surface finishing technique, and background color) and the effects of each tested variable on the changes in color and translucency. Results: The surface finishing techniques had a significant effect on the color and translucency of the monolithic zirconia materials. Glazing resulted in higher color differences and lower translucency values compared to polishing. For backgrounds of the same color, no significant differences were detected between the glazed zirconia groups for the same condition ( p &gt; .016). Conclusion: Overall, the study demonstrated the importance of selecting the appropriate surface finishing technique and translucency property of the monolithic zirconia materials to obtain the optimal esthetic results in dental restorations.

Effect of Simulated Gastric Acid on the Interface Between Zirconia and Resin Cement.

To evaluate the effect of simulated gastric acid solution (SGAS) and resin cement composition on the shear bond strength (SBS) of zirconia-based materials with different levels of translucency to composite resin. A total of 40 medium-opacity (MO; 3Y-TZP) and 40 medium-translucency (MT; 4Y-PSZ) zirconia slabs were distributed into four groups according to the composition of the resin luting system (MDP free or with MDP [primer + Panavia V5]) and storage method (distilled water or SGAS [5% hydrochloric acid]). Composite resin cylinders were cemented on the zirconia surface and stored for 91 hours. SBS, failure mode, and surface characterization analyses via scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were performed. SBS data were analyzed using three-way ANOVA and Tukey tests, and failure mode was assessed using one-way ANOVA (P < .05). Storage media (P = .180), resin cement (P = .110), zirconia (P = .404), and their interactions did not affect SBS values. Bond strength ranged from 21.41 to 26.11 MPa. SEM images showed that SGAS modified the surface topography of zirconia and resin cement. The presence of chlorine and silicon (wt%) were higher after SGAS storage than after water storage in both cements used, while barium was higher only for the MDP cement. There was a prevalence of mixed failures for most of the groups. The SBS between both types of zirconia and resin cement was not affected by SGAS, although changes in zirconia topography were observed after SGAS exposure. The presence of MDP in the cement layer had no effect on the SBS challenged by SGAS.

Influence of crown shade, translucency, and scan powder application on the trueness of intraoral scanners

ObjectivesNatural teeth and dental restorations present with various shades and levels of translucency. This study aimed to determine whether these variations in ceramic crowns and scan powder application affect the trueness of intraoral scanners. MethodsEight identical premade resin typodonts, each prepared for a crown on the maxillary right second molar, were used. Eight lithium disilicate crowns, distinguished by two levels of translucency (high and low) and four shades (BL1, A2, A3, and A4), were fabricated to an identical design and cemented onto each typodont, providing eight distinct experimental groups (2 levels of translucency × 4 shades). Reference scans were acquired using a desktop scanner. Test scans were performed ten times for each experimental group using two different intraoral scanners (Medit i700 and CEREC Primescan AC), with and without the application of scan powder (n = 10). Three-dimensional metrology software was used to assess the trueness of the intraoral scan datasets. Statistical analysis involved the Kruskal–Wallis H test, Mann–Whitney U test, and independent t-test (α=0.05). ResultsFor powder-free intraoral scan datasets, the crown shade did not significantly affect trueness within each translucency group (P = 1.000). For both intraoral scanners, compared with low translucency groups, higher marked deviations were exhibited by high translucency groups (P<.001). Scan powder use largely mitigated these differences (P>.05) and enhanced the trueness of the intraoral scan (P<.01). ConclusionsShade did not significantly influence the trueness of intraoral scans. High-translucency crowns were scanned with less accuracy than were low-translucency crowns. Clinical SignificanceUnlike tooth shade, translucency significantly affected the accuracy of intraoral scans. Therefore, considering the use of scan powder when scanning objects with high translucency may be beneficial.

Investigation of Microscopic Structure, Translucency Parameters, and Fracture Toughness of Two Pressable Lithium Disilicate Glass-Ceramic Materials.

To investigate the microscopic structure and fracture toughness of two pressable glass-ceramics comprising GC Initial LiSi Press (LiSi) and IPS e.max Press (e.max) with different levels of translucency. Four groups of LiSi and e.max with medium opacity and high translucency levels were examined. The crystal morphology of acid-etched specimens was observed under a scanning electron microscope (SEM). Six specimens in each group were fabricated in square shape (12 mm '12 mm ' 1.5 mm) to measure translucency parameters (TP) using a spectrophotometer. Ten bar-shaped specimens each group with dimension of 23 mm ' 2 mm ' 4 mm were determined the fracture toughness (KIc) by a surface crack in flexure (SCF) using a universal testing machine. One-way ANOVA and Scheffe post-hoc tests were used for statistical analysis. LiSi showed fine dense crystals 1 - 1.5 µm in size, while e.max showed long rod-shaped crystals 3 - 4 µm in size. The TP values of all specimens were coincided with their translucency levels.There was no statistical difference in the KIc between different translucency for both ceramics (p<0.05). However, the KIc of e.max was significantly higher than that of LiSi at both translucency levels. As a result of larger and longer crystals in e.max, it could provide better crack deviation mechanism to resist the fracture. Within the limitations of this study, the translucency levels of both lithium disilicate ceramics did not affect the fracture toughness of the materials. The fracture toughness of e.max was statistically higher than LiSi.

Effect of Aging Treatments on Properties of Zirconia with Different Levels of Translucency

Purpose: The aim of this study was to evaluate the effect of low-temperature degradation(L-TD), and weathering process on translucency, surface roughness, biaxial-flexural strength, and crystalline phase identification of zirconia with different levels of translucency. Materials and methods: A total of ninety-six (N= 96) zirconia discs were fabricated in this study. Samples were divided into three groups (n=32 each) according to type of zirconia: IPS EmaxZirCAD of low, medium translucency and Incoris translucent Zirconia of high translucency. Translucency measurements, surface roughness, biaxial flexural strength determination and phase identification were carried out before and after aging. Each group was then sub-divided into 2 subgroups (n=16); (subgroup A): Low-temperature degradation(L-TD) at 134ºC, (subgroup B): Accelerated aging by means of a weathering process (WP). Results: Statistical analysis using two-way ANOVA test revealed that there was a significant effect on translucency parameter (TP), and L-TD showed statistically significantly higher mean TP than WP. L-TD showed significantly lower mean roughness than WP. There was no significant difference between biaxial flexural strength values before aging and after L-TD and WP. There was no phase transformation identified before and after aging indicating resistance to different types of artificial aging. Conclusions: Low-temperature degradation and weathering process affect translucency parameter and surface roughness of zirconiabased materials. Artificial aging doesn’t affect the biaxial flexural strength, and phase identification of different zirconia translucencies.

Effect of Aging Treatments on Properties of Zirconia with Different Levels of Translucency

Purpose: The aim of this study was to evaluate the effect of low-temperature degradation(L-TD), and weathering process on translucency, surface roughness, biaxial-flexural strength, and crystalline phase identification of zirconia with different levels of translucency. Materials and methods: A total of ninety-six (N= 96) zirconia discs were fabricated in this study. Samples were divided into three groups (n=32 each) according to type of zirconia: IPS EmaxZirCAD of low, medium translucency and Incoris translucent Zirconia of high translucency. Translucency measurements, surface roughness, biaxial flexural strength determination and phase identification were carried out before and after aging. Each group was then sub-divided into 2 subgroups (n=16); (subgroup A): Low-temperature degradation(L-TD) at 134ºC, (subgroup B): Accelerated aging by means of a weathering process (WP). Results: Statistical analysis using two-way ANOVA test revealed that there was a significant effect on translucency parameter (TP), and L-TD showed statistically significantly higher mean TP than WP. L-TD showed significantly lower mean roughness than WP. There was no significant difference between biaxial flexural strength values before aging and after L-TD and WP. There was no phase transformation identified before and after aging indicating resistance to different types of artificial aging. Conclusions: Low-temperature degradation and weathering process affect translucency parameter and surface roughness of zirconiabased materials. Artificial aging doesn’t affect the biaxial flexural strength, and phase identification of different zirconia translucencies.

MAKE IT YOUR OWN - NEW APPROACH TO THE ESTHETICS

Aim: This paper aimed to represent new approach in esthetics. Introduction: MiYO Liquid Ceramic System gives the ability to easily create esthetic restorations that rival natural teeth in an ultra-thin layer. MiYO currently works with all zirconia and lithium disilicate materials and is easy to integrate with these materials. simple and easy way to match shades and get the depth and translucency needed on monolithic or cut back crowns all in one firing. quick and easy way to change a shade, raise or lower the brightness of crowns. Alternative to Costly Hand-layered Ceramics. Review: Two MiYO Esthetic System Kits: MiYO Liquid Ceramic for teeth and MiYO Pink Liquid Ceramic gingival system for tissue. Both systems are comprised of MiYO Color; different types of self-glazing colors with varying levels of translucency, each uniquely formulated to replicate natural apperence, such as incisal translucency, mamelons, crack lines, halos, and gingival tissue, and MiYO Structure, used to create depth, vitality, and texture found in natural enamel and tissue, in unprecedented thicknesses of 0.1mm-0.2mm. Achieve highly esthetic monolithic restoration easier and faster. Because traditional stains and glaze cannot achieve depth and translucency. Conclusion: Completely new and revolutionary coloring/staining system for zirconia or Lithium Disilcate restorations. Uniquely designed to create beautiful &amp; detailed esthetic effects for monolithic restorations.

Effects of core build-up resin composite translucency on IOS accuracy: an in-vitro study.

The accuracy of 3-dimensional images produced by intraoral-scanner (IOS) is affected by the optical characteristic of restorative materials such as metal, ceramic, and resin. This in-vitro study aimed to investigate the impact of core build-up resin composite translucency on IOS's accuracy. A core build-up procedure was performed on a proprietary 3D-printed model using injectable composites with 4 levels of translucency (highest to lowest: GC AE, A3, AO3, and EX). Ten experimental scans/group were operated using IOS Medit i700 on the phantom head-mounted model. Reference scans were obtained by an industrial scanner (Solutionix C500). Values of accuracy (trueness and precision) for the respective groups were evaluated using mean deviation values following 3D superimposition. Composite translucency caused scale reduction of optical impression. Values of trueness showed the highest scale reduction in the AE group significantly, followed by A3, AO3, and EX. Considering the cut-off value of deviations as 50μm for clinical acceptability, the analysis elucidated the most deviations in AE and A3. Similar results were found in precision where AE showed the highest deviation value statistically, then A3, AO3, and EX. Composite translucency affects the accuracy of optical impression, causing the fitting error of CAD/CAM prosthesis. The more translucent the composite, the less accurate the optical impression. This suggests the proper compensation during prosthesis designing for an optimal clinical result. Besides, practitioners should indicate the proper restorative materials regarding not only the aesthetics and mechanical properties but also the optical characteristics in the digital workflow.

Evaluation of Color Difference and Translucency of Modified PEEK Restorations Veneered with Different Veneering Materials Before and After Thermal Cycling

The aim of this study was to investigate the effect of different PEEK veneering materials, as well as thermocycling on the color difference (ΔE) and the translucency parameter (TP) of modified PEEK veneered restorations. Materials and Methods: Thirty-disc shaped specimens of veneered BioHPP (1.5 mm X 12 mm) were randomly divided into three groups (n=10) based on the type of the veneering material. Group (A): Discs veneered with CAD milled Lithium Disilicate, group (B): Discs veneered with pre-cured milled composite, and group (C): Discs veneered with conventional light cured composite. CIELab values were calculated for all specimens over white and black backgrounds using a laboratory spectrophotometer and then (ΔE) and (TP) were calculated. Specimens were subjected to thermal cycling, after which the same procedure for calculating (ΔE) and (TP) was repeated. Results: Repeated measures ANOVA showed that both the veneering material, and thermocycling had a statistically significant effect on mean ΔE, and on (TP) (P-value). Conclusions: All veneering techniques rendered an amount of color difference that was clinically unacceptable, as well as displaying much lower translucency levels than that of natural enamel and dentine

Grain size, crystalline phase and fracture toughness of the monolithic zirconia.

This study evaluated the relationship among translucency, crystalline phase, grain size, and fracture toughness of zirconia. Four commercial zirconia - Prettau®Anterior® (PA), Prettau® (P), InCorisZI (ZI), and InCorisTZI (TZI)- were selected for this study. The bar specimens were prepared to determine fracture toughness by using chevron notched beam method with four-point bending test. The grain size was evaluated by a mean linear intercept method using a scanning electron microscope. X-ray diffraction and Rietveld refinement were performed to evaluate the amount of tetragonal and cubic phases of zirconia. Contrast ratio (CR) was measured to investigate the level of translucency. PA had the lowest fracture toughness among other groups (P < .05). In addition, the mean fracture toughness of P was significantly less than that of ZI, but there was no difference compared with TZI. Regarding grain size measurement, PA had the largest average grain size among the groups. P obtained larger grain size than ZI and TZI (P < .05). However, there was no significant difference between ZI and TZI. Moreover, PA had the lowest CR value compared with the other groups (P < .05). This means PA was the most translucent material in this study. Rietveld refinement found that PA presented the greatest percentage of cubic phase, followed by TZI, ZI, and P, respectively. The different approaches are used by manufacturers to fabricate various types of translucent zirconia with different levels of translucency and mechanical properties, which should be concerned for material selection for successful clinical outcome.

Surface and bulk properties of zirconia as a function of composition and aging

Yttria-stabilized zirconia (Y-SZ) materials with different levels of translucency have been used for indirect dental restorations. Y-SZ composition and microstructure are modified to improve translucency, and it is not clear how these materials respond to aging. This study evaluated the effect of hydrothermal aging (HA) performed in an autoclave on the properties of four dental Y-SZ materials with different compositions. Sintered bar-shaped specimens (14 x 4 x 2 mm) were prepared from four different zirconia-based materials (n = 40): low translucency 3 mol % Y-SZ (3Y-LT; Ceramill ZI, Amann Girrbach); high translucency 4 mol % Y-SZ (4Y-HT; Ceramill Zolid); and two high translucency 5 mol % Y-SZ (5Y-HT – Lava Esthetic, 3M; 5Y-SHT - Ceramill Zolid FX). Fully sintered specimens were exposed to HA for different times (control - 0 h, 5 h, 10 h, or 15 h at 134 °C, 2 bar pressure) and characterized for surface roughness, flexural strength (three-point bending), hardness and elastic modulus (nanoindentation), surface wettability (sessile drop technique) and crystalline content (x-ray diffraction, XRD). Data was analyzed by two-way ANOVA and Tukey HSD (p < 0.05). Zirconia composition significantly affected roughness (p = 0.016). Zirconia*aging interaction affected flexural strength (p = 0.012), surface wettability (p < 0.001), and hardness (p = 0.002). Zirconia composition (p = 0.011) and aging (p = 0.001) affected elastic modulus, while the interaction effect was not significant (p = 0.94). HA affects zirconia-based materials in different degrees. For 3Y-LT and 4Y-HT, surface and bulk properties were affected by aging to a similar extent. However, surface and bulk properties may change during clinical use as a result of prolonged degradation of Y-SZ.

Effect of CAD-CAM ceramic materials on the color match of veneer restorations

Statement of problemWith the different translucency levels and types of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic materials, choosing the most appropriate CAD-CAM ceramic materials to better reproduce the color appearance of natural teeth can be challenging. PurposeThe purpose of this in vitro study was to analyze the color differences between natural teeth and milled veneers fabricated with the different types of CAD-CAM ceramic materials. Material and methodsTen extracted maxillary central incisor teeth with the A2 shade in the body region were prepared for ceramic veneers. The veneer restorations were designed by using the duplicating method and fabricated from 9 milling blocks (IPS e.max CAD HT/LT, Lava Ultimate CAD HT/LT, VITA SUPRINITY HT/T, IPS Empress CAD HT/LT/Multi) in a dental milling unit (n=10). The bonding surface of the abutment tooth was coated with a thin layer of a separating agent, and the veneer specimen with resin cement was then bonded to the corresponding abutment tooth. A clinical spectrophotometer was used to measure the Commission Internationale de l’Eclairage Lab values of natural teeth, abutment teeth, and milled veneers in the cervical, body, and incisal regions. Color differences between the natural tooth and A2 shade tab (ΔE1) and between the milled veneer and natural tooth (ΔE2) were calculated. The ΔE2 values were compared with the perceptibility threshold (ΔE=2.6) and acceptability threshold (ΔE=5.5). The paired-samples t test, 1-way analysis of covariance, and 2-way ANOVA were used to analyze data (α=.05). ResultsThe results of 1-way analysis of covariance showed that ceramic materials significantly affected the a∗ and b∗ values of the milled veneers (P<.001) but did not affect the L∗ values of the milled veneers (P>.05). The results of 2-way ANOVA indicated that the ΔE2 values were not significantly affected by different CAD-CAM ceramic materials (F=1.560, P=.138), while statistically significant differences were found in the veneer regions (F=6.588, P=.002). The ΔE2 values ranged from 2.41 to 5.36, less than the clinically acceptable color threshold of 5.5. ConclusionsThe color parameters of milled veneers were affected by the different types of CAD-CAM ceramic materials. The color of the veneer restoration was able to match that of the natural tooth.

Impact of resin composite cement on color of computer-aided design/computer-aided manufacturing ceramics.

To analyze the impact of the color of a resin composite cement (RCC) on the optical properties of different computer-aided design and computer-aided manufacturing (CAD/CAM) ceramics. Specimens (N=220, thickness: 0.9 ± 0.03 mm) were fabricated from: leucite (Initial LRF Block/IPS Empress CAD), lithium disilicate (Amber Mill/IPS e.max CAD), lithium metasilicate (Celtra Duo), and lithium alumina silicate ceramic (n!ce) in translucency levels HT and LT. All specimens were bonded with an RCC (Light+/Warm+). Color was analyzed (spectrophotometer) initially as well as after bonding of RCC with CAD/CAM ceramics using CIELab and CIEDE2000. Kolmogorov-Smirnov test, one-way ANOVA and t test served for analyzing (α=0.05). Highest impact on ΔE presented the choice of ceramic (ηp2 =0.155/p < 0.001), followed by translucency level (HT/LT; ηp2 =0.050/p=0.001) as well as interaction between ceramic and translucency level (ηp2 =0.175/p < 0.001). ΔE00 was mainly influenced by the choice of ceramic (ηp2 =0.490/p < 0.001), the shade of resin composite (ηp2 =0.031/p=0.012) as well as the interaction between ceramic and resin composite (ηp2 =0.258/p < 0.001). RCC shades presented differential impacts on color change of CAD/CAM ceramics. Knowledge of the impact of available RCC shades on different CAD/CAM ceramics is crucial for an esthetic outcome and proper selection of ceramic restorations.

Bulk-Fill Direct Restorative Materials: An In Vitro Assessment of Their Physio-Mechanical Properties

Bulk-fill restorative material has gained popularity in clinical practice, due to their perceived timesaving aspect. Objective was to compare the properties of bulk-fill direct restorative materials. Filtek Z350 (CR), Filtek One Bulk Fill Restorative (BF), Fuji IX and EQUIA Forte (EF) were compared. Thirty specimens from each material were prepared according to ISO 4049 for three-point flexural strength. Elastic moduli and hardness (n = 20) were evaluated using nanoindentation. Depth of cure (DC) (n = 20) was measured for BF at three different depths (2, 3, 4 mm) and at two irradiation times (20 and 40 s). Wear testing was carried out for three different periods (3, 6, 12 month(s)). All specimens were stored in 37 °C water for 24 h prior to testing. Results were evaluated using one-way ANOVA followed by a post hoc Bonferroni test (p &lt; 0.05). BF and CR showed a significantly higher flexural strength than other groups (p &lt; 0.05), and the highest Weibull modulus was found in CR. BF showed sufficient DC with at least 85%, at all thicknesses. CR and BF also had a high level of translucency than EF and Fuji IX. Significant differences in flexural strength were found among all materials except between Fuji IX and EF. While all material tested are suitable for use clinically, BF and CR have superior properties than GIC based bulk-fill.

Translucency of HT lithium disilicate specimens with different thicknesses – preliminary study

Introduction The main advantage of using an all-ceramic system is to achieve a superior aesthetic result by increasing the translucency [1]. When dealing with darkened substrates, it is important to understand the level of translucency of the restorative materials according to their thickness, in order to adapt their application to specific clinical situations. Studies evaluating the translucency of different thicknesses of lithium disilicate, for CAD/CAM technology, are limited. This study aims to evaluate and compare the translucency of high translucency (HT) lithium disilicate with different thicknesses. Materials and methods Lithium disilicate blocks IPS e.max® CAD HT (Ivoclar Vivadent®), shade A3, were sintered in a furnace (Vita Vacumat 6000 MP). The sintered blocks were cut, with a hard tissue microtome (Accutom-50; Struers Inc), in quadrangular specimens (n = 20). Four subgroups (n = 5) were defined, according to thickness (0.5, 1.0, 1.5, and 2.0 mm). The translucency of the specimens was measured using the spectrophotometer SpectroShade Micro (MHT S.p.A., Arbizzano di Negar, Italy) (λ = 410–680 nm). All measurements were made from 6 different areas of each specimen against a white background (Comission Internationale de L’Eclairage (CIE) L*=94.5, a*=–0.3, b*=–1.5) and against a black background (CIE: L*=6.1, a*=1.4, b*=–4.0), in order to obtain their L* (value coordinate), a* (red-green coordinate) and b* (yellow-blue coordinate) values under natural light (D65) [2,3]. Based on the obtained values, the translucency was calculated using the translucency parameter (TP) and the contrast ratio (CR) formulas [4]. Resulting TP and CR data were submitted to descriptive statistical analysis. Results Mean TP values ranged from 15.5 (±0.4) to 31.6 (±2.3) and mean CR values ranged from 0.65 (±0.03) to 0.84 (±0.01). Thinner thicknesses showed higher translucency. Discussion and conclusions Translucency is a fundamental optical property and a determinant factor when it comes to selecting the restorative material for highly aesthetical areas. This study had, therefore, the purpose of understanding which data may or may not be useful in clinical practice. The dentist should be familiar with the properties and characteristics of new and innovative materials in order to pick the one that better adapts to a certain clinical situation [3]. HT Lithium disilicate specimens showed that as thickness decreases, translucency values increase.

A comparison of ceramic crown color difference between different shade selection methods: Visual, digital camera, and smartphone

Statement of problemThe light source stability of digital cameras and smartphones is important in shade matching in restorative and prosthetic dentistry to communicate objectively with the dental laboratory. Techniques that standardize the light source of such devices are lacking, and this limitation can lead to color mismatches, difficulties in color communication, and treatment documentation. PurposeThe purpose of this clinical study was to compare the magnitude of color difference (ΔE) among 3 shade selection methods during the fabrication of ceramic crowns: visual shade selection with a shade guide, digital shade selection with a digital camera and cross-polarizing filter, and digital shade selection with a smartphone and a light-correcting device. Material and methodsForty-five patients in need of ceramic crowns were enrolled, and shade selection was evaluated according to different protocols: visual shade selection (A-D shade guide and IPS Natural Die Material Shade Guide, sent to the dental laboratory technician via a laboratory prescription); digital shade selection with a digital camera (D7000; Nikon Corp) with an 85-mm lens and wireless close-up flash, with and without a cross-polarizing filter (Polar eyes); and digital shade selection with a smartphone and a light-correcting device (iPhone XS attached to Smile Lite MDP, with and without its cross-polarizing filter accessory). Information from the smartphone was imported to an app (IPS e.max Shade Navigation App; Ivoclar AG) that converted the reading to a shade and level of translucency for the ceramic restoration. For all photographs, a gray reference card with known color values was positioned by the mandibular teeth and was used for white balancing of the digital photographs with a software program. All photographs were edited and sent to the dental laboratory: white-balanced with the shade guide; white-balanced with the substrate shade guide; black and white; saturated; and cross-polarized. Ceramic crowns were made with the same lithium disilicate material (IPS e.max CAD; Ivoclar AG) and cemented with the same resin cement (RelyX Ultimate Clicker, A3 shade; 3M). The ΔE values between the crown and the adjacent tooth were determined. The data were analyzed by using a 1-way analysis of variance (ANOVA) and Tukey post hoc tests (α=.05). ResultsThe mean ΔE between a cemented ceramic crown and the adjacent tooth in the visual shade selection group was 5.32, significantly different than both digital camera (ΔE=2.75; P=.002) and smartphone (ΔE=2.34; P=.001), which were not different from each other (P=.857). ConclusionsThe digital shade selection with photographs acquired with both a digital camera and a smartphone with a light-correcting device showed a threshold within the acceptable values (ΔE<3.7), whereas the visual shade selection showed an average ΔE above the threshold for acceptable values (ΔE>3.7). The use of a gray reference card helped standardize the white balance from the digital images.

Modern CAD/CAM silicate ceramics, their translucency level and impact of hydrothermal aging on translucency, Martens hardness, biaxial flexural strength and their reliability

ObjectivesTo investigate the impact of hydrothermal aging on Martens parameter (Martens hardness: HM/elastic indentation modulus: EIT) and biaxial flexural strength (BFS) of recently available CAD/CAM silicate ceramics. Methods220 specimens (diameter: 12 mm, thickness: 0.95 mm) were fabricated from six CAD/CAM ceramics in two translucency levels (LT/HT): (a) two lithium disilicate (Amber Mill, ABM; IPS e.max CAD, IEM), (b) one lithium metasilicate (Cetra Duo, CEL), (c) one lithium alumina silicate (n!ce, NIC), and (d) two leucite ceramics (Initial LRF Block, LRF; IPS Empress CAD, IPR). HM/EIT and BFS were measured initially and after hydrothermal aging (134 °C/0.2 MPa/100 h) in an autoclave. The Kolmogorov-Smirnov-test, t-test, one-way ANOVA with post-hoc Scheffé test, Kruskal-Wallis-test, Mann-Whitney-U-test with Bonferroni correction and Weibull statistics were performed (α = 0.05). ResultsCEL and IEM showed the highest and the leucite ceramics the lowest Martens parameter. Within HT, ABM and NIC were in same initial HM value range with CEL and IEM. ABM and NIC showed lower initial EIT values than CEL and IEM, however higher than IPR. The lowest aged values were analyzed for ABM. After aging, Martens parameter decreased for LRF, ABM, and CEL. IEM showed the initial highest BFS, followed by ABM. NIC and LRF showed the lowest BFS. IEM and ABM presented the highest aged BFS. Hydrothermal aging increased BFS values for LRF (HT), IPR, CEL (HT), and NIC (HT) compared to the initial values. CAD/CAM leucite ceramics showed higher Weibull modul values compared to lithium silicate ceramics. SignificanceThe well-considered selection of ceramics in relation to the areas of indication has the highest influence on the long-term stability of restorations: CAD/CAM lithium disilicate ceramics presented the highest and leucite ceramics the lowest mechanical properties, whereas the reliability was better for leucite than for lithium silicate ceramics.

Color compatibility between dental structures and three different types of ceramic systems

BackgroundTo assess color compatibility between dental structures (human enamel and dentine) and three different types of ceramic systems.MethodsSamples (1 and 2 mm-thick) of extracted tooth (containing dentine and enamel areas) and three ceramic systems with different shades and opacities (HT–High Translucent, T–Translucent) were prepared for this study: Vita Suprinity—VS (HT, T; A1, A2, A3, A3.5, B2, C2, D2) (Vita Zahnfabrik); Vita Enamic—VE (HT, T; 1M1, 1M2, 2M2, 3M2) (Vita Zahnfabrik) and Noritake Super Porcelain EX-3—NKT (A1, A2, A3, A3.5, B2, C2, D2) (Kuraray Noritake Dental). Reflectance measurements of all samples were performed over black backgrounds using a non-contact spectroradiometer (SpectraScan PR-670, Photo Research) under a CIE 45°/0° geometry. CIE L*a*b* color parameters were measured and CIELAB/CIEDE2000 color differences (ΔE00/ΔE*ab) and corresponding Coverage Error (CE) of ceramic system for dentine or enamel samples were calculated. Color data was analyzed using one-way ANOVA and post-hoc multiple comparisons tests. CE values were interpreted by comparisons with available 50:50% acceptability color threshold (AT) for dentistry.ResultsStatistically significant differences in lightness were found among all ceramic systems and human dentine (p < 0.001), while no significant differences were registered between enamel and VSHT, T and VEHT. 1 mm dentine showed no statistical differences with VST and VSHT for a* coordinate, while 2 mm dentine showed no significant differences (p > 0.05) with VEHT. Thin samples (1 mm) of dentine and enamel showed significant statistical differences (p < 0.05) for b* coordinate with less translucent materials (NKT, VET and VST). For dentine samples, none of the ceramic materials provided a CE lower than AT. VSHT provided the best CE for 1 mm-thick (CE00 = 1.7, CEab = 1.9) and for 2 mm-thick (CE00 = 2.3; CEab = 2.5) enamel samples.ConclusionsColor coordinates of evaluated esthetic ceramic systems were statistically different from those of human dentine in almost all cases. The evaluated ZrO2 lithium silicate glass–ceramic (VS), with its two levels of translucency, provided lower CE values with human enamel samples while conventional feldspathic ceramic (NKT) and hybrid ceramic systems (VE) demonstrated a better color compatibility with dentin samples.