OBJECTIVE: To evaluate if the firing cycles and etching conditions have an effect on the tensile bonding strength (TBS) of IPS e.max-CAD and CeltraDUO. METHODS: Lithium-disilicate (IPS e.max-CAD) ceramic blocks and zirconia reinforced lithium-disilicate (CeltraDUO) were sectioned into rectangular tiles. The tiles were randomly assigned to various treatment groups and heat treated (1, 5, or 9 firing cycles) or (0, 1 or 5 firing cycle) respectively. e.max-CAD and CeltraDUO tiles were etched for different times (20,160, 300 seconds) and (20, 50, 80 seconds) respectively with hydrofluoric-acid gel (9.6% or 5%). Titanium-pins were sand-blasted on the flat end and cemented on the etched tiles using self-adhesive resin cement (TheraCem). A vertical load of 12N was placed for 40 minutes. All the cemented specimens were stored in incubator at 37°C for 48 hours. A tensile test was performed using a mechanical testing machine (Instron-5566A). The load at failure was recorded and the TBS was calculated. The same procedure was followed on another set of 18 e.max-CAD (fired for 5 firing cycles) and 21 CeltraDUO tiles (fired for 1 firing cycle). The same cementation procedure was followed and TBS was calculated. RESULTS: The TBS of both CeltraDUO and e.max-CAD was significantly affected by etching duration and firing cycles (p<0.001), but not significantly affected by etchant concentration (p=0.31). The highest load to failure was observed around 50 and 60 seconds of etching respectively. CONCLUSION: The etching time and firing cycle directly affect the TBS of both materials whereas the etchant concentration does not. / 2021-07-15T00:00:00Z

This study’s objective was to evaluate repetitive firing cycles’ effects on the translucency, light’s absorption coefficient, and flexural strength of zirconia-reinforced lithium silicate ceramics. Two zirconia-reinforced lithium silicate ceramics and one lithium disilicate glass-ceramic were tested. Blocks of all materials were sectioned into tiles with different thicknesses and subjected to up to five firing cycles using the firing schedule indicated in the manufacturer’s user instructions. Light transmission ratio (T) and absorption coefficients were determined using a spectrophotometer. Further, bars were sectioned from blocks of all materials and tested for three-point-bend flexural strength using a Universal Testing Machine (Instron), and flexural strength was calculated from load at failure. Factorial ANOVA and Tukey’s HSD tests were conducted to analyze light transmission and flexural strength, while regression was used to analyze the absorption coefficient. Weibull parameters and fractographic analysis also were investigated. The results showed that repetitive firing cycles reduced e.max® and Vita Suprinity’s® translucency, but not that of Celtra® Duo, which showed no significant difference. All materials of greater thickness exhibited less translucency, and e.max® CAD had the highest mean light transmission; however, it was not significantly different than Celtra® Duo. Repetitive firing cycles showed more absorption coefficient of light with Vita Suprinity® and e.max®, except for Celtra® Duo, which showed no difference. Vita Suprinity® showed the highest absorption coefficient; however, it was not significantly different than e.max® CAD. Repetitive firing cycles had no significant effect on flexural strength. High and low flexural strength samples for all materials showed similar characteristics with respect to crack propagation patterns, and fracture origins. In conclusion, repetitive firing cycles decreased both e.max® and Vita Suprinity’s® translucency significantly. Repetitive firing cycles increased e.max® and Vita Suprinity’s® absorption coefficient significantly, particularly at shorter wavelengths. Repetitive firing cycles did not increase flexural strength statistically significantly. Vita Suprinity® showed an inherent and more homogeneous flaw-distribution in the first two firing cycles compared to the distribution of flaws in the other two materials.

Inledning:För dentala ändamål finns idag en rad helkeramiska alternativ på marknaden. Ett vanligt förekommande material är det litiumdisilikatbaserade IPS e.max® Press, en glaskeram som används på de tandtekniska laboratorierna för framställning av protetiska konstruktioner genom pressteknik. Ett problem är att materialet ibland inte fyller ut formen, vilket ger en misslyckad pressning och objekten går förlorade. En idé finns att detta kan undvikas genom förvärmning av främst presskolv men även presspuck. Detta förfarande rekommenderas dock inte av fabrikanten. Syftet med föreliggande studie är att undersöka huruvida förvärmning av presskolv och presspuck påverkar böjhållfastheten i pressade litiumdisilikatkroppar, samt huruvida förvärmning av presskolv och presspuck påverkar kristallstrukturen i materialet.Material och metod:Sextio cylindriska provkroppar, med en konnektor med radien 1,5mm, framställdes i det litiumdisilikatbaserade materialet. Provkropparna delades in i tre grupper (n=20), där variablerna var förvärmning av presskolv (FK), förvärmning av presskolv och presspuck (FKP) samt en kontrollgrupp som följde fabrikantens anvisningar. Ett trepunkts böjprov utfördes på samtliga provkroppar. Brottytan SEM-analyserades för att upptäcka eventuella skillnader i ytans kristallstruktur.Resultat:Medelvärdet i Newton och standardavvikelsen (±SD) avseende böjhållfasthet var följande: Kontrollgrupp 255N (±26), FK 253N (±22) och FKP 252N (±29). Resultatet visade inga signifikanta skillnader mellan grupperna. Inga skillnader i ytans kristallstruktur kunde ses i SEM-analysen.Slutsats:Inom ramen för föreliggande studies begränsningar kan följande slutsats dras:•Den litiumdisilikatbaserade keramen IPS e.max® Press påverkas inte vad gäller böjhållfasthet eller avseende materialstruktur av förlängd värmebehandling av presskolv och presspuck.

OBJECTIVES: Objectives of this study were to evaluate and compare the failure load and mode of failure of aged (4 years) monolithic and veneered Y-TZP and glass ceramic subjected to static loading, cyclic loading, and thermo-cycling. MATERIALS AND METHODS: 2 ceramic materials were used: Vita In-Ceram YZ and IPS e. max CAD. Each material was designed into 60 veneered copings and 30 monolithic crowns (180 specimens). 10 specimens per group were loaded under compression using an Instron universal testing machine at a rate of 0.5 mm/minute until fracture. Another 10 specimens were subjected to cyclic loading (chewing simulation) in a water bath for 50,000 cycles at a frequency of 1 Hz at 30% of the mean failure load, and then were loaded under compression to fracture. Another 10 specimens were subjected to a thermo-cycling test, then loaded under compression to fracture. Data were analyzed using the ANOVA test at α=0.05. RESULTS: The mean failure load (standard deviation) values for veneered zirconia and e.max CAD copings and monolithic zirconia and e.max CAD crowns under static loading were: In-Ceram YZ 14830 N (2494), VM9 2491 N (1047), PM9 3909 N (783), IPS e.max CAD 4197 N (1011), IPS e. max Ceram 1206 N (296), IPS e.max press 2949 N (710). The values for veneered standard zirconia and e.max CAD copings and monolithic zirconia and e.max CAD crowns after cyclic fatigue were: In-Ceram YZ 11039 N (2720), VM9 2849 N (840), PM9 3170 N (1156), IPS e.max CAD 3539 N (526), IPS e. max Ceram 1291 N (1051), IPS e.max press 3093 N (742). For veneered standard zirconia and e.max CAD copings and monolithic zirconia and e.max CAD crowns after thermo- cycling: In-Ceram YZ 15695 N (1517), VM9 3177 N (816), PM9 2860 N (783), IPS e.max CAD 4265 N (681), IPS e. max Ceram 1149 N (375), IPS e.max press 2832 N (717). There was a significant difference in failure load between veneered and monolithic ceramic crowns subjected to static loading, cyclic loading, and thermo-cycling, and a significant difference in the mode of failure between veneered or monolithic crowns. CONCLUSIONS: 1. There was a significant difference in the static failure load of different veneered (Hand layered and pressed-on) YTZP zirconia and e.max CAD copings, monolithic YTZP zirconia, and e.max CAD Crowns, (p < 0.05). 2. The highest static failure loads were shown by high strength monolithic (In-Ceram YZ) material, which were more resistant to cyclic loading compared to other veneered and monolithic systems. 3. The failure load of IPS e.max ceram group was significantly the lowest compared to all other groups. 4. The failure load data for IPS e.max CAD and Vita In-Ceram YZ structures revealed a significant difference in the effect of these structures on the failure loads (p < 0.05). Comparing structures, monolithic Vita In-Ceram YZ crowns showed the highest failure load. 5. There was a significant difference in failure mode among various veneered and monolithic systems (p < 0.05). Only the variable treatment had no impact on the mode of failure of various veneered and monolithic systems (p > 0.05). / 2020-10-24T00:00:00Z

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / The objectives: 1. To compare the flexural strength, flexural modulus, and fracture toughness of specimens fabricated from recently marketed translucent full-contour zirconia, traditional zirconia, and lithium disilicate glass ceramic. 2. To compare the load-to-failure of crowns fabricated from recently marketed translucent full-contour zirconia, traditional zirconia, and lithium disilicate glass ceramic at their recommended tooth-reduction thickness. Methodology: Four groups of translucent zirconia (BruxZir, KDZ Bruxer, CAP FZ, Suntech zirconia), one group of traditional zirconia (CAP QZ) and IPS e.maxCAD) were tested. Twelve bars of each material were made and tested for flexural strength, and fracture toughness. Fracture patterns were imaged under SEM. Forty-eight crowns (8 from each group) were fabricated with CAD/CAM technique following manufacturers’ recommendations for the amount of tooth reduction. All the crowns were cemented to prepared epoxy resin dies with RelyX Unicem and tested for static load to failure in a universal machine. Result: In bar-shape samples, CAP QZ (traditional zirconia) showed the highest flexural strength (788.12 MPa), fracture toughness (6.85 MPa.m1/2), and fracture resistance (2489.8 N). All translucent zirconia groups show lower mechanical properties than QZ. However, there were no differences between translucent and traditional zirconia in the fracture resistance of the crown-shape samples. There was no significant difference in fracture resistance between IPS e.max crowns at recommended thickness and other zirconia crowns at recommended thickness. Conclusion: With less reduction of tooth structure, a high inherent strength and chip resistance make full-zirconia crowns a good alternative to porcelain-fused-to-metal crowns and all other ceramic crowns.

Indiana University-Purdue University Indianapolis (IUPUI) / Background: Elucidating the lithium disilicate system like the popular IPS e.max® CAD (LS2), made specifically for Computer-Aided Design and Computer-Aided Manufacturing (CAD-CAM), as a function of temperature unravels new ways to enhance material properties and performance. Objective: To study the effect of various thermal processing on the crystallization kinetics, crystallite microstructure, and strength of LS2. Methods: The control group of the LS2 samples was heated using the standard manufacturer heating-schedule. Two experimental groups were tested: (1) an extended temperature range (750-840 °C vs. 820-840 °C) at the segment of 30 °C/min heating rate, and (2) a protracted holding time (14 min vs. 7 min) at the isothermal temperature of 840 °C. Five other groups of different heating schedules with lower-targeted temperatures were evaluated to investigate the microstructural changes. For each group, the crystalline phases and morphologies were measured by X-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. Differential scanning calorimeter (DSC) was used to determine the activation energy of LS2 under non-isothermal conditions. A MTS universal testing machine was used to measure 3-point flexural strength and fracture toughness, and elastic modulus and hardness were measured by the MTS Nanoindenter® XP. A one-way ANOVA/Tukey was performed per property (alpha = 0.05). Results: DSC, XRD, and SEM revealed three distinct microstructures during LS2 crystallization. Significant differences were found between the control group, the two aforementioned experimental groups, and the five lower-targeted-temperature groups per property (p<0.05). The activation energy for lithium disilicate growth was 667.45 (± 28.97) KJ/mole. Conclusions: Groups with the extended temperature range (750-840 °C) and protracted holding time (820-840 °C H14) produced significantly higher elastic-modulus and hardness properties than the control group but showed similar significant flexural-strength and fracture-toughness properties with the control group. In general, explosive growth of lithium disilicates occurred only when maximum formation of lithium metasilicates had ended.