Low Translucency Research Articles

ВЛИЯНИЕ СКОРОСТНОГО ОБЖИГА КЕРАМИЧЕСКОГО МАТЕРИАЛА НА ОСНОВЕ ДИОКСИДА ЦИРКОНИЯ ZICERAM T ОТЕЧЕСТВЕННОГО ПРОИЗ-ВОДСТВА НА ПОКАЗАТЕЛИ ПРОЧНОСТИ И ЦВЕТА

Zirconia dentures are gradually becoming a widespread type of dental prosthetics. The production of zirconia blanks for dentistry has been launched in our country. In recent years, the possibility of high-speed sintering of zirconia dentures has been well studied, which makes it possible to reduce the manufacturing process of dental restorations by four to five times. Zirconia ceramics compositions and high-speed sintering furnaces are being improved, sintering protocols are being optimized. In this paper, we reported about the influence of high-speed firing protocols on important material`s characteristic, such as three-point bend flexural strength and color parameters at ten different heating modes, differing by heating rates, final temperature and holding time during high-speed heat treatment of ceramic material. Accord-ing to the results of bending strength tests, samples obtained with a total time of high-speed firing from 20 to 60 minutes have similar values, more than 300 MPa. In accordance with the ISO 6872 standard, such flexural strength is sufficient for fabrication of single crowns in both the anterior and posterior groups of teeth. A study on the laboratory spectrophotometer (Spectron M) in the CIELab system, showed a multidirectional change in color characteristics at different heating rates and sintering temperatures. An increase in the value of zirconia sam-ples from domestic blanks "Ziceram T" produced by St. Petersburg firm "Zircon Ceramics" was established with a sufficient confidence grade. The shortened firing time leads to an in-crease in the value of the samples, which associate with a lower translucency.

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.

The Thickness and Opacity of Aesthetic Materials Influence the Restoration of Discolored Teeth.

This study aimed to evaluate the influence of thickness and opacity on the ability of composite resin and ceramic veneer restorations to mask discolored teeth. Ninety veneers were made of lithium disilicate ceramic, shades BL1 and 0 (IPS e.max Press, Ivoclar Vivadent), and 60 were made of composite resin, shade BL-L (IPS Empress Direct, Ivoclar Vivadent). The veneers measured 4 mm in width x 4 mm in length and had a thickness of 0.7, 1.0, or 1.2 mm. One hundred and fifty human premolars were selected to obtain 150 dental fragments with the following dimensions: 4 mm x 4 mm x 3 mm (width x length x thickness). The fragments were discolored, submitted to color measurement and randomly assigned to 15 groups (n=10) according to the type and opacity of the restorative material (IPS e.max Press: high translucency [HT], low translucency [LT], and medium opacity [MO]; IPS Empress Direct: dentin and enamel) and thickness of the veneers (0.7, 1.0, and 1.2 mm). After cementation of the ceramic or composite resin veneers using a translucent resin cement (RelyX veneer, 3M), a final color measurement was taken from each specimen and the total color variation (ΔE) was calculated by subtracting the initial and the final color measurement. The final lightness (L*) of the restored dental fragments was also calculated. The highest ΔE values were observed for the LT and MO ceramic groups, followed by dentin composite resin. Regarding the different thicknesses of ceramic veneers, every 1.2-mm-thick group had higher values of ΔE, considering their respective opacities (p<0.05). The highest lightness values were found for the LT and MO ceramic veneers (thickness of 1.2 mm). Dentin-shade composite resins showed similar lightness values in all groups. The best thickness/opacity combinations for masking discolored dental substrates were LT and MO ceramic veneers with 1.2-mm thickness. Dentin-shade composite resin veneers with a thickness of 0.7-1.0 mm showed good ability to mask discolored dental substrates.

Optical properties of new zirconia-based dental ceramics: literature review

The first generation of polycrystalline zirconia-based ceramic used to produce dental prosthesis showed excellent mechanical behavior; however, its low translucency limited the indication for aesthetic monolithic restorations. Thus, various strategies have been tested in order to develop a material that has high strength and good optical properties. The aim of this study was to characterize, through a literature review, the translucency of different types of zirconia-based ceramics indicated for monolithic restorations. The literature search was performed in PubMed/Medline database, from 2010 to 2019, using as keywords: zirconia, translucency, and optical properties. The 3rd (monochromatic) and 4th (multichromatic) generations of zirconia, which have high cubic phase content, showed the highest translucency among the zirconia-based ceramics investigated. Additionally, other strategies, such as the addition of lanthanum oxide and the infiltration of feldspathic glass in the zirconia surface (graded-zirconia), resulted in a good balance of optical and mechanical properties.

Optical properties of a novel glass-ceramic restorative material.

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. 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. 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). 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. 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.

Effect of lithium disilicate ceramic thickness, shade and translucency on transmitted irradiance and knoop microhardness of a light cured luting resin cement

This in vitro study evaluates the influence of pressed lithium disilicate thickness, shade and translucency on the transmitted irradiance and the Knoop microhardness (KHN) of a light-cured resin cement at two depths. One hundred and thirty-five ceramic discs of IPS e.max Press (Ivoclar Vivadent) were fabricated and divided into twenty-seven groups (n = 5) according to the association between translucency: HT (hight translucency), LT (low translucency), and MO (medium opacity); shade: BL2, A1 and A3.5; and thickness: 0.5 mm, 1.5 mm, and 2.0 mm. One side of each ceramic disc was finished, polished and glazed. The irradiance (mW/cm²) of a multiwave LED light curing unit (Valo, Ultradent) was evaluated with a potentiometer (Ophir 10ª-V2-SH, Ophir Optronics) without (control group) or with interposition of ceramic samples. The microhardness of Variolink Esthetic LC resin cement (Ivoclar Vivadent) was evaluated after 24 h at two depths (100 μm and 700 μm). Data were submitted to ANOVA followed by Tukey’s test (α = 0.05). Irradiance and KHN were significantly influenced by ceramic thickness (p < 0.0001), shade (p < 0.001), translucency (p < 0.0001) and depth (p < 0.0001). Conclusions: the interposition of increasing ceramic thicknesses significantly reduced the irradiance and microhardness of resin cement. Increased depth in the resin cement showed significantly reduced microhardness for all studied groups. Increased ceramic opacity reduced the KHN of the resin cement at both depths for all ceramic thicknesses and shades.

Comparison of translucency and opalescence among different dental monolithic ceramics

Statement of problemMonolithic ceramic restorations designed by computer-aided design and computer-aided manufacturing are increasingly being used by clinicians. With the introduction of new materials, their optical characteristics also need to be investigated. PurposeThe purpose of this in vitro study was to compare the translucency and opalescence of lithium disilicate, zirconia-reinforced lithium silicate, presintered zirconia-reinforced lithium silicate, polymer-infiltrated ceramic-network material, and multilayer zirconia. Material and methodsA total of 50 rectangular plates (14×12×1 mm) of 5 monolithic ceramics were prepared in this in vitro study (n=10). Each zirconia specimen was divided into 3 groups of incisal, middle, and gingival thirds. Each group was then evaluated separately. The color parameters of specimens were measured on 3 backgrounds, white, black, and #3 Ivoclar Natural Die Color material, by using a spectrophotometer. The translucency and opalescence of the specimens were determined by the relevant equations, and between-group comparisons were made. One-way ANOVA and Tamhane post hoc tests were used to compare groups (α=.05). ResultsThe difference among the groups was significant in translucency (F=137.346, df=6, P<.001), contrast ratio (F=134.148, df=6, P<.001), and opalescence parameters (F=128.028, df=6, P<.001). The 3 zirconia groups (10.87 ±0.54 to 11.88 ±0.26) had a significantly lower translucency than the other groups, and the zirconia-reinforced lithium silicate group (18.14 ±0.74) showed the highest translucency. Zirconia-reinforced lithium silicate (12.36 ±0.42) had the highest opalescence, and the lowest opalescence was found for polymer-infiltrated ceramic-network (5.43 ±0.28) and the incisal third of zirconia (5.45 ±1.06). ConclusionsThe zirconia-reinforced lithium silicate and presintered zirconia-reinforced lithium silicate specimens had the highest translucency and opalescence. The studied multilayer zirconia, which had different cubic phase values from incisal to gingival blank, showed similar translucency over the entire range, and differences among different regions were related to chromatic variables.

Influence of the ceramic translucency on the relative degree of conversion of a direct composite and dual-curing resin cement through lithium disilicate onlays and endocrowns

IntroductionThe goal of this study was to investigate the influence of the ceramic translucency, restoration type and polymerization time on the relative degree of conversion of a dual-curing resin cement and a conventional microhybrid resin composite using a high-power light-curing device. Methods and materialsTwo 4.0 mm thick onlay (O) and two 7.5 mm thick endocrown (E) lithium disilicate restorations in high and low translucency (HT/LT) were fabricated on a decapitated molar. The pulp chamber was prepared to accommodate a 2 mm layer of a microhybrid resin composite (MHC) or dual-curing resin cement (DCC). Composite specimens were light-cured (n = 15; 1200 mW/cm2) without or through an onlay or endocrown restoration. Fourier-transform infrared spectroscopy (FTIR) absorbance curves were collected for the same composite specimen after 3 × 20, 3 × 40, 3 × 60 and 3 × 90 s of light-curing. The relative degree of conversion (DC%) was calculated and results analyzed using Kruskal-Wallis test and Friedman's ANOVA. Alpha was set at 0.05. ResultsAfter 3 × 60 s, the DC of MHC was significantly lower (p = 0.03; r = 0.61) under LT/EC restorations (Mdn: 77.8%) than HT/EC restorations (Mdn: 95.2%). DC of the DCC was not significantly affected by the ceramic translucency or restoration type. MHC had a significant higher DC than DCC under the HT/O, LT/O and HT/E restorations. There were no significant differences between MHC and DCC cured through LT/E restorations. ConclusionDC for DCC was not significantly affected by the ceramic translucency or restoration type. DC for MHC was significantly lower for LT/EC than HT/EC restorations after 3 × 60s polymerization, but not different for the high translucent restorations and low translucent onlays. Clinical relevancethe use of light-curing microhybrid composite for bonding high translucent onlays and endocrowns and low translucent onlays seems feasible.

Effects of shade and thickness on the translucency parameter of anatomic-contour zirconia, transmitted light intensity, and degree of conversion of the resin cement

Statement of problemAnatomic-contour zirconia prostheses are usually cemented with resin cement. However, information regarding the effects of the zirconia shade and thicknesses on the translucency of the prosthesis, the intensity of the transmitted light beneath the prosthesis, and the subsequent degree of conversion in the resin cement is sparse. PurposeThe purpose of this in vitro study was to investigate the translucency parameter in 3 anatomic-contour zirconia specimens of 2 shades at 5 different thicknesses and to investigate the transmitted light intensity and degree of conversion of the resin cement beneath the ceramic specimens by using a traditional zirconia and a lithium disilicate glass-ceramic as controls. Material and methodsCeramic specimens from 1 anatomic-contour zirconia in a generic shade (CAP FZ) and 2 anatomic-contour zirconias in A2 shade (Zirlux and Luxisse) were used. Lithium disilicate in HT A2 shade (IPS e.max CAD) and traditional zirconia in a generic shade (CAP QZ) were used as controls. A total of 125 ceramic specimens (n=25) were fabricated to a final specimen dimension of 12×12 mm and in thicknesses of 1.0, 1.25, 1.5, 1.75, and 2.0 mm according to the manufacturers’ recommendations. The CIELab color space for all specimens placed against a white and black background was measured with a spectrophotometer (CM-2600D), and the translucency parameters were calculated for the materials at various thicknesses. A light-polymerizing unit (DEMI LED) was used to polymerize the resin cement (Variolink II) placed beneath the ceramic specimens. Transmitted light intensity from the polymerization unit beneath the ceramic specimens was measured by using a spectrophotometer (MARC Resin Calibrator), and the transmittance of each specimen was calculated. The coefficient of absorption of each material was calculated from the regression analysis between the natural log of transmittance and specimen thickness. The degree of conversion of resin cement was measured by using a Fourier transformation infrared (FTIR) spectrophotometer. The results were analyzed by using 2-way ANOVA (α=.05). The relationship between the transmittance and the translucency parameter was evaluated by plotting the transmittance against the translucency parameter value of each specimen. ResultsThe translucency parameter decreased with increasing thickness in all 5 material groups. All anatomic-contour zirconia had lower translucency parameters than e.max CAD (P<.001). The same results were found for the intensity of the transmitted light (P<.001). Both A2 shade anatomic-contour zirconia (Zirlux and Luxisse) showed significantly lower light transmittance than a generic shade anatomic-contour zirconia (CAP FZ) (P<.001). The coefficients of absorption were found to range from 0.63 to 1.72 mm-1, and reflectance from 0.10 to 0.25. The results from the degree of conversion of resin cement after polymerization through 1 to 2 mm of specimens showed a significantly higher degree of conversion in the e.max group than in all other groups (P<.001). The correlation between translucency parameter and the intensity of the transmitted light suggested that the relationship was shade dependent. ConclusionsThe translucency parameter and the transmitted light intensity of ceramic material were influenced by the type of ceramic and the shade and thickness of the ceramic. The combined effects of layer thickness and the intensity of the transmitted light in the A2 shade anatomic-contour zirconia (Zirlux and Luxisse) resulted in a lower degree of conversion in resin cement than in a generic shade anatomic-contour zirconia (CAP FZ) at layer thicknesses of 1.75 and 2 mm.

Influence of Varying Dentin and Enamel Layer Thicknesses of Nano-Composite Resins on Color Match between Lithium Disilicate Dental Ceramic and Composite Resins.

Objectives: The aim of this study was to evaluate the influence of varying dentin and enamel layer thicknesses of two nano-composite resins on color match of composite resins and lithium disilicate dental ceramic. Materials and Methods: Twenty-six specimens of two types of nano-composite resins, Opallis and Vittra, were fabricated using the two-layered technique with different thickness ratios of enamel and dentin composites (A2 shade) with a total thickness of 1.2mm. Thirteen discs of the same shade and thickness of IPS e.max Press LT (low translucency) lithium disilicate dental ceramic were also fabricated. Specimen color was measured with a spectrophotometer. The difference in color (ΔE00) of composite and ceramic specimens, and the translucency parameter (TP) of all specimens were calculated. Data were analyzed using multi-factor ANOVA (P<0.05). Results: The color difference (ΔE00) values of composites and ceramic were not clinically acceptable in any areas of either of the two composites (ΔE00>2.25). But ΔE00 between the two composite resins was in the clinically acceptable range (ΔE00<2.25). The mean TP value of IPS e.max Press was greater than that of Vittra and lower than that of Opallis. Conclusion: In similar thicknesses, composite resins with any enamel/dentin thickness ratio could not successfully simulate the color and translucency of IPS e.max Press LT ceramic.

Effect of ceramic thicknesses and opacities on water sorption and solubility of a light-curing resin cement by different units

Aim: This study evaluated the water sorption and solubility of a light-cured resin cement, under four thicknesses and four opacities of a lithium disilicate ceramic, also considering three light-emitting diode (LED) units. Methods: A total of 288 specimens of a resin cement (AllCem Veneer Trans – FGM) were prepared, 96 samples were light-cured by each of the three light curing units (Valo – Ultradent / Radii-Cal – SDI / Bluephase II – Ivoclar Vivadent), divided into 16 experimental conditions, according to the opacities of the ceramic: High Opacity (HO), Medium Opacity (MO), Low Translucency (LT), High Translucency (HT), and thicknesses (0.3, 0.8, 1.5, and 2.0 mm) (n = 6). The specimens were weighed at three different times: Mass M1 (after making the specimens), M2 (after 7 days of storage in water), and M3 (after dissection cycle), for calculating water sorption and solubility. Results: The higher thickness of the ceramic (2.0 mm) significantly increased the values of water sorption (44.0± 4.0) and solubility (7.8±0.6), compared to lower thicknesses. Also, the ceramic of higher opacity (HO) generated the highest values of sorption and solubility when compared to the other opacities, regardless of the thickness tested (ANOVA-3 factors / Tukey’s test, α = 0.05). There was no influence of light curing units. Conclusion: Higher thicknesses and opacities of the ceramic increased the water sorption and solubility of the tested light-cured resin cement.

Effects of sintering time on translucency and color of translucent zirconia ceramics.

To investigate the effect of sintering time on translucency and color of translucent zirconia ceramics. Sixty translucent zirconia (5Y-TZP) specimens (12 × 1.6 mm, Katana (KAT) and NexxZr (NEX)) were divided into six groups (n=10) according to sintering time; 1, 2 (specified by manufacturer-control), and 3 hs. Color differences (ΔEab) within same material when sintered using different times and between materials when same sintering time was used were calculated, as well as translucency parameters (TP) after the use of each sintering time. Data for ΔEab and TP were analyzed with two-way ANOVAs, pairwise comparisons, and Fisher's LSD Test (Post-hoc). When 1 or 3 h were used, color difference from the color of specimens when manufacturer-specified time (2 h) was used was similar for both KAT and NEX. ΔEab values of NEX were significantly higher than KAT when sintered for 1 or 3 h (P < 0.001). TP increased for KAT when sintered for 1 h, and was higher than NEX. TP for NEX increased when sintered for 3 h (P < 0.001), but was not significantly different than that of KAT. Effect of 1 or 3-h sintering on color was similar for both zirconias. For NEX, this effect resulted in greater differences from the color of specimens when manufacturer-specified time was used. Sintering for 1 h increased the translucency of KAT. When high translucency is desired, clinicians may prefer 1-h sintering for KAT zirconia. When lower translucency is desired, 3-h sintering for NEX can be used. However, for NEX, the color after 1- or 3-h sintering was different than the color obtained with manufacturer-specified time, and this difference may affect the final color of restoration compared to the final color when manufacturer-specified time is used.

Assessment of Capability of Lithium Disilicate Glass Ceramics to Reproduce the A2 Shade and to Mask A4 Substrates

Aim: Capability of lithium disilicate glass ceramics to reproduce the A2 shade and to mask A4 substrates.Materials and Method: 32 lithium disilicate ceramic specimens were classified materials into 8 groupsof 4 each. Group I- III high translucency (HT) monolayer discs, group IV- VI had low translucency (LT)monolayer discs, group VII- VIII had medium translucency (MO) bilayer discs. A2 shade tab shade guide(VITA classical A1-D4) was used for CIE L*a*b* measurements of control. Color differences using thresholdswas as follows: for imperceptible (?E &lt; 1.0), perceptible (1.0 &lt; ?E &lt; 3.3), and clinically unacceptable (?E&gt; 3.3) differences.Results: ?E in group IV exhibited highest (9.92±0.21) and group III lowest (8.08± 0.25) value. When thecomplex was compared to the A4 substrate, significant difference among all groups (p &lt; 0.05) was found.?E values when the complex was compared to the A2 shade tab, group III exhibited highest (4.82±0.16)and group V lowest (0.72±0.06) value. In groups I specimens had acceptable differences, group II hadperceptible differences, group III had perceptible differences, group IV had acceptable differences, group Vhad imperceptible differences, group VI and VII had acceptable differences and group VIII had imperceptibledifferences.Conclusion: Authors suggested to use LT ceramics with less thickness in the range of 0.5 mm- 0.7 mm tomask discoloration.

Comparison of optical and crystal properties of three translucent yttria-stabilized tetragonal zirconia polycrystals with those of lithium disilicate glass-ceramic material

Background/purposeAmong the ceramic materials used for all-ceramic crowns, zirconia has high biocompatibility and favorable mechanical properties, but its main drawbacks include low translucency and stress-induced phase transformation. To stabilize high-strength tetragonal zirconia polycrystal (TZP), 3–5 mol% yttria is usually added to prepare yttria-stabilized TZP (Y-TZP). In this study, the optical properties of three commercial Y-TZP ceramics were compared with those of the clinically available glass-ceramic material of lithium disilicate, and the relationship between translucency and crystal properties was analyzed in vitro. Materials and methodsTwelve 5-mm-thick standardized disks were prepared from three Y-TZP ceramics and one lithium disilicate block. Absolute translucency was measured using a spectrophotometer with an integrating sphere. X-ray diffraction was used to quantify the main structural parameters (i.e., preferred plane, quantitative phase, and grain size) of Y-TZP crystals. ResultsThe product-dominated phase of Y-TZP exhibited a tetragonal lattice pattern, and the preferred planes had minor variations. The diffraction patterns of the three Y-TZP ceramics demonstrated minor effects on translucency, without significant differences (p > 0.05). The grain size of 54–70 nm was negatively related to translucency in Y-TZP. Lithium disilicate specimens had significantly higher translucency than the three Y-TZP specimens (p < 0.001). ConclusionGrain size reduction played an essential role in developing highly translucent Y-TZP ceramics. The three Y-TZP ceramics were essentially opaque but exhibited poorer translucency than lithium disilicate in terms of esthetics.

Bonding to zirconia: Effects of translucency and cusp inclinations using an experimental methodology.

Purpose To investigate the effects of translucency and cusp inclination on the micro-shear bond strength (µSBS) of zirconia to self-adhesive resin cement (SARC).Methods Sixty U-shaped zirconia specimens with 1.0 mm thickness consisting of three planes (0°, 20°, and 30°) simulating different cusp inclinations were fabricated from zirconia blocks of high, moderate, and low translucency (n=20). SARC was bonded to the specimen and light-cured for 40 s. The µSBS was tested using a universal testing machine with a cross-head at a speed of 0.5 mm/min and fracture mode was observed using a stereomicroscope (×50). Two-way analysis of variance followed by a post hoc Tukey's honest significant difference test was used for the statistical analyses (α=0.05).Results Varied µSBS values were found in the test groups (7.1-14.9 MPa). Within the zirconia of the same translucency, the µSBS value of the plane 0° specimen was significantly higher than that of the 20° and 30° planes (all p<0.05). Within the zirconia of the same cusp inclination, the µSBS value of highly translucent zirconia was significantly higher than that of moderate and low translucent zirconia (all p<0.05). There was no significant interaction between cusp inclination and translucency (p=0.525). Among the fracture modes, 83.33% were adhesive failure, 11.11% mixed failure, and 5.56% were cohesive failure.Conclusions Translucency and cusp inclination significantly affect the µSBS of zirconia to SARC. The higher the translucency, the greater are the µSBS values; the higher the cusp inclination, the lower are the µSBS values.

Marginal and internal fit of three-unit fixed dental prostheses fabricated from translucent multicolored zirconia: Framework versus complete contour design

Statement of problemTranslucent multicolored zirconia materials enable more esthetic complete contour zirconia fixed dental prostheses (FDPs) than conventional zirconia, which exhibits low translucency and high opacity and is monochromatic. However, how the marginal and internal fit of translucent multicolored zirconia FDPs compare with those of traditional frameworks that require veneering is unclear. PurposeThe purpose of this in vitro study was to compare the marginal and internal fit of frameworks and complete contour 3-unit FDPs fabricated from translucent multicolored zirconia. Material and methodsFrameworks with a thickness of 0.5 mm and complete contour FDPs with a thickness of 0.8 to 1.5 mm were manufactured by using a workflow similar to one from a zirconia master model (mandibular left second premolar-mandibular left second molar). Two polyvinyl siloxane replicas were made for each specimen to measure the marginal and internal fit. Measurement locations were mesial, lingual, buccal, and distal for each abutment. In these locations, the marginal opening (MO), chamfer area (CA), axial wall (AW), and occlusal area (OC) were measured. The data were analyzed with 2-way ANOVA and the Bonferroni post hoc test (α=.05). ResultsFrameworks showed significantly better mean ±standard deviation fit values than complete contour 3-unit FDPs at measurement areas MO (frameworks: 112 ±22 μm, complete contour FDPs: 144 ±37 μm) (P=.013), CA (frameworks: 89 ±12 μm, complete contour FDPs: 110 ±22 μm) (P=.006), and OC (frameworks: 182 ±36 μm, complete contour FDPs: 244 ±64 μm) (P=.008). At the measurement area AW (frameworks: 47 ±7 μm, complete contour FDPs: 50 ±9 μm of each location, no significant difference was observed between frameworks and complete contour FDPs (P=.361). ConclusionsDesign differences in 3-unit FDPs fabricated from translucent multicolored zirconia influenced the marginal and internal fit. Frameworks had smaller marginal fit than complete contour FDPs for translucent multicolored zirconia.

Comparison of mechanical properties of different reinforced glass-ceramics

Statement of problemData concerning the mechanical properties of the newly developed lithium disilicate ceramic HS10PC are lacking. PurposeThe purpose of this in vitro study was to investigate the flexural strength (FS), Martens hardness (HM), indentation modulus (EIT), fracture load (FL), and wear resistance (WR) of HS10PC compared with those of the established glass-ceramics IPS e.max Press and IPS Empress Esthetic. Material and methodsFour pressable glass-ceramics were examined: HS10PC (estetic ceram ag), IPS e.max Press low translucency (LT) and high translucency (HT; Ivoclar Vivadent AG), and IPS Empress Esthetic (ES; Ivoclar Vivadent AG). For each material, a total of 85 specimens were fabricated. Specimens were subdivided into 4 groups for FS (n=30), HM, EIT (n=10), and FL measurement according to the Voss test after artificial aging in an autoclave (n=15), artificial aging in a mastication simulator (n=15), and no artificial aging (n=15). In addition, WR (n=10) was measured after 240 000, 600 000, and 1 200 000 masticatory cycles. Data were statistically analyzed using the global univariate ANOVA, the Scheffé post hoc and paired t tests, and Weibull distribution (α=.05). ResultsHT showed the highest FS, while ES presented the lowest FS of all groups (P<.001). ES showed lower values for HM (P<.001), EIT (P<.001), and FL for specimens treated in an autoclave and mastication simulator (P<.001) compared with all other groups. An increase in the wear of the ceramic and enamel antagonist between 240 000 and 1 200 000 masticatory cycles was observed for all groups (P<.001). After 1 200 000 masticatory cycles, HS10PC presented less wear of the ceramic than the other 3 materials (P=.003). ConclusionsThe newly developed lithium disilicate ceramic HS10PC showed comparable results with the established IPS e.max Press for FS, HM, EIT, FL, and WR. Lithium disilicate ceramics presented higher mechanical results than the leucite-reinforced ES, with all the ceramics showing similar results for the WR of the enamel antagonist.

Managing Rhizoctonia Damping-Off of Rocket (Eruca sativa) Seedlings by Drench Application of Bioactive Potato Leaf Phytochemical Extracts.

Plants produce a huge array of secondary metabolites that play a key role in defense mechanisms against detrimental microorganisms and herbivores, and represent a suitable alternative to synthetic fungicides in sustainable agriculture. In this work, twelve crude hydroethanolic extracts derived from leaves of different potato cultivars were chemically characterized by LC/MS and their antioxidant properties were investigated in vitro. Furthermore, the biological activity against the fungal pathogen Rhizoctonia solani was evaluated both in vitro and in vivo. Extracts showed the ability to inhibit R. solani growth in vitro and significantly reduced damping-off incidence in in vivo experiments. Furthermore, R. solani mycelia exposed to the extracts showed an altered morphology (low translucency, irregular silhouette, and cytoplasmatic content coagulation) compared to the untreated control in light microscopy examination. Principal component analysis conducted on identified chemical compounds highlighted significant metabolic variations across the different extracts. In particular, those that inhibited most of the growth of the pathogen were found to be enriched in α-chaconine or α-solanine content, indicating that their biological activity is affected by the abundance of these metabolites. These results clearly indicated that plant-derived compounds represent a suitable alternative to chemicals and could lead to the development of new formulates for sustainable control of plant diseases.

Does ceramic translucency affect the degree of conversion of luting agents?

ObjectivesSolely light-activated luting agents have been suggested for cementing procedures with aesthetic rehabilitations, but questions remain regarding their curing potential under more opaque prosthesis. To determine the degree of carbon double bond (C=C) conversion (DC) of four categories of luting strategies when considering the interposition of lithium-disilicate ceramic laminates with different translucencies during the photo-activation procedures.Materials and methodsFour different luting strategies were considered: a dual-activated resin-based cement (control, RelyX ARC, 3M ESPE), a solely light-activated resin-based cement (RelyX Veneer, 3M ESPE), a flowable resin-based composite (Filtek Z350 XT Flow, 3M ESPE), and a pre-heated (68 °C for 30 min) regular resin-based composite (Filtek Z350 XT, 3M ESPE). The DC was determined by Fourier-transformed infrared spectroscopy (n = 6), 1 min after light-activation in two conditions: (a) with direct light exposure and (b) with light exposure with the interposition of lithium-disilicate disks (e.max Press, Ivoclar Vivadent) with 1.5 mm thickness with three translucent degrees: high translucency (HT), low translucency (LT), and medium opacity (MO). The translucency parameter (TP) formula was performed to quantitatively evaluate the ceramics’ translucencies using white (L* = 93.7, a* = 1.2, and b* = 0.8) and black (L* = 8.6, a* = − 0.7, and b* = − 1.5) backgrounds. The irradiance from the light curing unit (Bluephase G2, Ivoclar Vivadent) was calculated with a power meter (Ophir Optronics) with direct light exposure to the sensor and also with the interposition of the light ceramic discs. Degree of conversion data was submitted to two-way ANOVA and Tukey’s test (α = 0.05).ResultsTranslucency parameters values were 16.4, 13.4 and 12.6 for HT, LT and MO ceramics—respectively—and affected the percentage of light transmission. For all ceramic translucencies the highest DC values were observed for the dual-activated resin-based cement followed by the solely light-activated resin-based cement, the flowable composite and then by pre-heated regular composite. The ceramic’s translucency influenced the DC only for the pre-heated composite.ConclusionsThe effect of the ceramic translucency on the curing behavior was dependent on the luting strategy. The DC was only affected for the pre-heated composite, which demonstrates lower conversion with the increased ceramic opacity.

Structural, chemical and optical characterizations of an experimental SiO2–Y-TZP ceramic produced by the uniaxial/isostatic pressing technique

This study aimed to produce a new SiO2+Y-TZP ceramic via uniaxial/isostatic compression that was structurally and chemically characterized relating to its translucency and flexural strength. SiO2 and Y-TZP were mixed using a ball mill, pressed and sintered at 1150 °C. The optical and mechanical properties of the specimens were compared to lithium disilicate (LD) and zirconia-reinforced lithium silicate (ZLS) (Kruskal-Wallis, α = 0.05). The Fourier Transform Infrared Spectroscopy bands suggested an interaction between Si, O and Zr. Contrast ratio and translucency parameter of the experimental ceramic were higher and lower, (p = 0.000001) respectively, than those of the LD and ZLS. The experimental ceramic presented similar flexural strength to ZLS, but lower than LD (p < 0.0001). It can be concluded that this processing method is efficient to obtain a SiO2+Y-TZP ceramic and 1150 °C crystallizes SiO2 without inducing t-m transformation. The SiO2+Y-TZP ceramic presented lower translucency and higher masking ability than the commercially available glass-ceramics, but similar flexural strength to one glass-ceramics.