Tetragonal Zirconia Polycrystals Research Articles

Effect of Universal Adhesives on Long-term Bond Strength to Zirconia.

To evaluate the effect of universal adhesives on the long-term bond strength to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). Polyethylene tubes filled with composite cement containing 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) were adhesively luted to 60 fully sintered Y-TZP slabs (7 x 7 x 2 mm) with or without (control) previous application of a 10-MDP-based adhesive (All Bond Universal, Bisco) - ABU; Clearfil Universal Bond Quick, Kuraray Noritake - CUB; Scotchbond Universal Adhesive, 3M Oral Care - SUA) on the zirconia surface. The bonded specimens were stored in water for 24 h, 6 months, or 1 year and subjected to microshear bond strength testing. The data were analyzed by one-way ANOVA and Tukey's test (p < 0.05). The contact angle was measured after adhesive application to evaluate surface wettability. The adhesive-treated specimens were analyzed with x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) for chemical characterization. The application of a 10-MDP-based adhesive significantly improved bond strength of composite cement to zirconia when compared to the control group (no adhesive application) (p < 0.05). One-year water storage significantly decreased bond strength for ABU- and CUB-bonded specimens, but not for SUA-bonded specimens. The analysis by XPS and ToF-SIMS showed peaks of carbon, phosphorus, and silicon in all adhesive-treated specimens. One-year water storage affected the bond strength of composite cement to zirconia when All Bond Universal or Clearfil Universal Bond Quick were used.

Wear Properties of Conventional and High-Translucent Zirconia-Based Materials.

This study investigated the two-body wear resistance of a first generation 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), a second generation 3Y-TZP, a third generation 4 mol% yttria partially stabilized zirconia (4Y-PSZ), a 5 mol% yttria partially stabilized zirconia (5Y-PSZ), and a type III gold alloy (Aurocast 8), performed using opposing antagonistic cusps made out of the same material. Eight cylindrical specimens were prepared for each material (n = 8) for a total of forty specimens (N = 40). Conical cusps were fabricated for each material. Each cylinder–cusp pair was arranged inside a two-axis chewing simulator over up to 360,000 loading cycles. The wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm3). The antagonist wear (mm) was recorded before and after the wear test to evaluate the linear difference. Statistical analysis was performed using one-way analysis of variance (ANOVA); multiple comparisons were performed according to Tukey’s method. No statistically significant differences (p > 0.05) among the first generation 3Y-TZP, second generation 3Y-TZP, and 4Y-PSZ wear were found. 5Y-PSZ showed statistically significant higher wear compared to other the zirconias. Aurocast 8 displayed the highest values in terms of vertical wear, antagonist cusp wear, and volumetric loss. Although still not statistically comparable, the wear behavior of the latest 5Y-PSZ was the closest to the widely recognized gold standard represented by the type III gold alloy.

Two-body wear resistance and fatigue survival of new Y-TZP and ATZ ceramics made with a new slip-casting method

BackgroundDental zirconium oxide restorations are milled from pre-sintered blocks or disks which are produced either with high isostatic pressure (HIP) or, simpler, a slurry technique. The objective was to perform a fatigue test and an in vitro wear simulation of two ceramics, yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramic and a hybrid zirconium oxide-aluminum oxide ceramic, (ATZ) both produced either the classical way using high isostatic pressure (HIP, control) or with a slurry technique. Materials and methodsTen discs/group were subjected to a cyclic biaxial fatigue test using a staircase approach under water at 37 °C in a dynamic universal testing machine. The 2-body wear test was performed on eight lapped 12 mm thick cylindrical samples subjected to spherical (ø 6 mm) leucite ceramic antagonists in a CS-4 chewing simulator at 49 N force and 0.7 mm lateral movement for 600 k cycles and 4167 thermal cycles (5–55 °C). Volumetric wear was calculated based on laser-scanned surfaces. Selected samples of both tests were viewed in SEM. ResultsAll the ceramic specimens produced using the HIP method survived up to 1.2 M cycles with the maximum load of the equipment (1000 N) loading the specimens up to 1527 MPa. The fatigue limit stress at 1.2 M cycles for the Slurry ATZ samples was 946 MPa. For the Slurry Y-TZP samples the fatigue limit stress at 1.2 M cycles was 658 MPa. At 600 k cycles, all zirconium oxide ceramics showed no measurable wear and had a highly polished appearance. The leucite ceramic antagonists wear developed in a linear way. There was no difference between the materials produced with the slurry and the HIP process. ATZ ceramic produced significantly more wear than 3Y- TZP ceramic. ConclusionsThe HIP method provided higher fatigue strength than the Slurry manufacturing method. All HIP ceramics surpassed the limit threshold (1527 MPa) of the testing machine. The tested ceramics did not show any measurable wear but had worn the leucite reinforced glass ceramic antagonists for a considerable amount.

Effect of Hydrothermal Degradation on Flexural Fatigue Strength of Various Cubic-Containing Translucent Zirconia.

The aim of this study is to investigate the fatigue and hydrothermal degradation behavior among the cubic-containing translucent yttrium oxide stabilized tetragonal zirconia polycrystal (Y-TZP). Four groups of commercial Y-TZP (T, ST, XT, and P), containing different amount of cubic crystal, were examined. Artificial aging was accomplished by autoclaving at 122°C under 2 bar pressure for 8 hours. Fatigue simulation parameters were set using an axial 50 N load, a total of 240,000 cycles. Flexural fatigue strength was evaluated. Two-way analysis of variance with Tukey's honestly significant difference test was used to determine the difference in fatigue strength values between various type of zirconia materials within control and aging with a significant level of 5%. Weibull analysis was conducted on the fatigue strength data. All groups showed the mean flexural fatigue strength had no significant difference in hydrothermally aged specimens compared with specimens without aging (p = 0.154). Group T showed significantly higher flexural fatigue strength followed by group ST, XT, and P. Group XT and P showed no significant difference in strength value (p > 0.05). Group T demonstrated a lower probability of failure than group ST, XT, and P whether with or without aging. Weibull modulus in group T and ST with aging condition was increased and higher than all the experimental groups. Cubic-containing zirconia materials (group ST, XT, and P) exhibited lower flexural fatigue strength than non-cubic 3Y-TZP zirconia (group T). However, various cubic-containing translucent zirconia was assumed to have high resistance to hydrothermal degradation.

Evaluation of microleakage and push-out bond strength of various composite resins for sealing the screw-access channel in implant-supported restorations

Statement of problemMicroleakage and loss of the composite resin sealing the screw-access channel are frequent complications of screw-retained implant-supported prostheses. How the screw-access channel should be best restored to reduce such complications is unclear. PurposeThe purpose of this in vitro study was to evaluate the microleakage and bond strength of 3 types of composite resins (flowable, packable, and bulk-fill) with or without a bonding agent treatment to seal the screw-access channel of 2 types of restorative materials (zirconia and Co-Cr alloy) with or without thermocycling. Material and methodsIn total, 240 yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) specimens (IPS e.max ZirCAD) and 240 Co-Cr alloy (Vera PDS) specimens were prepared with a Ø3×3-mm cylindrical cavity at the center to simulate the screw-access channel. Three types of composite resins (flowable, packable, and bulk-fill resin) (Filtek Z350 XT Flowable Restorative, Filtek Z350 XT Universal Restorative, and Filtek One Bulk Fill Restorative) were applied to restore the access channel of the zirconia and Co-Cr specimens with or without a bonding agent (Single Bond Universal Adhesive). Microleakage and push-out bond strength were determined and compared by dividing the specimens into experimental groups with or without thermocycling (1000 times with 30 seconds at 5 ±2 °C and 55 ±2 °C). The results were analyzed by using a 1-way ANOVA and 4-way ANOVA. Adjustment for multiple comparisons was made with the Tukey Honestly Significant Difference (HSD) test. ResultsThe specimens subjected to thermocycling showed a lower bond strength (P<.001) and higher microleakage (P<.001) than specimens stored in a constant-temperature water bath. Specimens treated with bonding agents showed a higher bond strength (P<.001) and lower microleakage (P<.001) than specimens not treated with a bonding agent. Higher bond strengths were observed in the order of bulk-fill resin, packable resin, and flowable resin (P<.001). Packable resin showed higher microleakage than flowable resin and bulk-fill resin (P<.05). No significant difference in microleakage was found between the flowable resin and bulk-fill resin (P>.05). ConclusionsHigher bond strengths were observed in the order of bulk-fill resin, packable resin, and flowable resin. Less microleakage was observed in the flowable resin and bulk-fill resin than in the packable composite resin. Bonding agent treatment was effective in increasing bond strength and decreasing microleakage. Zirconia and Co-Cr showed a bond strength similar to that of composite resins, but zirconia showed higher microleakage than Co-Cr. Restoring the screw-access channel with the bulk-fill resin should increase bond strength and reduce microleakage.

A Novel Approach for Micro-Antenna Fabrication on ZrO2 Substrate Assisted by Laser Printing for Smart Implants

The use of Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) in medicine has rapidly expanded over the past decade, driven by its advantageous properties, showing potential to overcome titanium alloy in implant fabrication. The release of metal ions and the aesthetic problems of titanium alloy implants are the main reasons for this trend. In addition to meeting expectations regarding its properties, an implant must possess intrinsic capacities such as auto-diagnostic and auto-treatment. Thus, based on the concept of smart implants, this work proposes a hybrid approach for printing a part of the communication system of a zirconia implant by resorting to laser technology, aiming to endow the implant with intrinsic capacities. Therefore, the antenna was designed and then printed on the zirconia surface. The laser was applied as a versatile tool, whether for preparing the surface of the material in a subtractive way, by creating the micro-cavity, or for printing the silver-based antenna in an additive way through laser technology. The silver powder was used as the conductor material of the antenna. The results revealed that the antenna is capable of communicating from inside the body with the outside world without needing to have an exterior antenna attached to the skin.

The Effect of Simulated Chewing on the Surface Roughness of Direct and Indirect Resin-Composites Opposed by Zirconia: An In Vitro Study.

Purpose To assess the surface roughness of two different light-cured resin-composites when opposed by monolithic zirconia after simulated mastication. Materials and Methods Materials included a direct restorative nanohybrid (n = 10) and an indirect microhybrid (n = 10) resin-composite (Tetric EvoCeram and Sinfony, respectively). The antagonist material was 3 mol% yttria-stabilized tetragonal zirconia polycrystalline ceramic. Each material was subjected to in vitro chewing against zirconia using a chewing simulator for 250,000 cycles. A 3D profilometer was used to assess the surface roughness parameters of each resin-composite before and after the simulated chewing. Independent t-test and paired sample t-test were performed to compare roughness values for both materials and to compare baseline and after chewing simulation values (p = 0.05). Results Sinfony showed significantly greater roughness values compared to Tetric EvoCeram (p ≤ 0.025) before and after simulated chewing, except for Sa and Sv parameters after simulated chewing where the difference between the two materials was insignificant (p = 0.06 and 0.89, respectively). Surface roughness increased for both materials after simulated chewing compared to baseline values, but the difference was insignificant (p ≥ 0.065). However, Sa (p = 0.04) and Sv (p = 0.012) for Tetric EvoCeram were significantly higher after compared to before chewing simulation. Conclusion Tetric EvoCeram had a smoother surface than Sinfony before and after simulated chewing. Surface roughness for both materials was higher after simulated chewing compared to baseline values which represent surface damage that was significant for Tetric EvoCeram while Sinfony showed better resistance.

Strength and reliability of zirconia fabricated by additive manufacturing technology

ObjectivesTo test strength and reliability of 3D printed compared to milled zirconia. MethodsCylindrical specimens were fabricated from milled (group G1; e.max ZirCAD LT) and from 3D printed (group G2; LithaCon 3Y 230) 3-mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP). While G1 and G2 were sintered in one step, a further series (G3) of 3D printed 3Y-TZP was sintered in two steps including intermediate color infiltration. In each group, two different conditioning strategies were applied (n ≥ 20 samples/subgroup): (1) final polishing with #1200 diamond discs according to ISO 6872, and (2) final polishing with #220 diamond discs resulting in imperfectly polished surfaces. All samples were tested to fracture with a universal testing device (cross-head speed: 1 mm/min). Characteristic strengths and Weibull moduli were calculated. Effects were analyzed by means of either ANOVA (homocedastic data) or Welch ANOVA (heterocedastic data). ResultsFor samples conditioned according to ISO 6872, mean flexural strengths were 1462 ± 105 MPa (G1), 1369 ± 280 MPa (G2), and 1197 ± 317 MPa (G3). For the imperfectly polished subgroups, strength values were 1461 ± 121 MPa (G1), 1349 ± 332 MPa (G2), and 1271 ± 272 MPa (G3). Although all groups showed high mean strength values, the reliability of milled zirconia (Weibull moduli 14 < m <16) outperformed that of the 3D-printed material (3 < m <6). SignificanceEven after color infiltration in a partially sintered state, the tested 3D printed zirconia exceeded the ISO flexural strength criteria for all types of fixed ceramic restorations by far (800 MPa for class 6, ISO 6872), indicating its high potential for clinical use. Further optimization of the internal material structure after sintering might improve the reliability of 3D printed zirconia which is currently inferior to that of milled zirconia.

Differential analyses of ginger extract implant coating material

Background: Different types of material were used as implants; the most common is titanium and its alloy, and recently zirconia acquired robust interest due to many desirable properties, Natural biocomposites recently received widespread attention as an active coating covering metallic implants due to their bioactivity, availability, and affordability. Aim: This study aims to present the evolvement and characterization of ginger extract materials overlying Yttria-stabilized tetragonal zirconia and PEEK substrate. Material and method: The methodology of the present study involved preparation of ginger extract powder twenty disc-shaped specimens with a dimension of 10 mm, from partially sintered Yttria-stabilized tetragonal zirconia polycrystal and PEEK . The naturally prepared ginger extract powder was deposited via cold spraying device. The prepared ginger extract characterized by particle size analyzer and ginger extract while The experimental specimens were characterized by, field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDX). Conclusion :naturally prepared ginger extract exhibit uniform distribution and good adherence to the samples Therefore, it can be used as a coating material for zirconia and PEEK implants with promising biological and mechanical properties.

Mechanical, electrochemical, and biological properties of YSZ-Mo: A new class of bio-composites

Polycrystalline tetragonal zirconia (3YTZP) has high strength and fracture toughness (K1C) among the other ceramics. However, this amount is still low compared to metals, limiting the use of these monolithic- parts. This study explores the effect of molybdenum on the mechanical, electrochemical, biological, and antibacterial properties of 3Y-TZP-based composites. Three samples of YSZ, YSZ-10wt.%Mo, and YSZ-20wt.%Mo were fabricated by the SPS method at 1450 °C. The microstructure of the mentioned bio-composites was examined by FESEM and XRD analysis. Three-point flexural strength, fracture toughness test, and Vickers microhardness test were also performed. YSZ-10Mo and YSZ-20Mo samples were subjected to Tafel polarization and electrochemical impedance spectroscopy (EIS) analysis. MTT assay was also used to assess the compatibility of the samples with G-292 cells. The antibacterial behavior of the specimens was assessed by the shake flask test. Microstructural results proved the complete densification of the samples. A rise in the molybdenum content slightly decreased the flexural strength (from 1185 ± 52 MPa for YSZ to 841 ± 63 for YSZ-20Mo) and hardness (from 13.35 ± 0.41 GPa for YSZ to 8.10 ± 0.24 GPa for YSZ-20Mo). However, the opposite behavior was observed for the fracture toughness of the samples (from 7.25 ± 0.67 MPa.m1/2 for YSZ to 14.90 ± 0.32 MPa.m1/2 for YSZ-20Mo). The corrosion test indicated the excellent corrosion resistance of the YSZ-10Mo composite. Enhancement of the molybdenum content had a destructive effect on the corrosion resistance of the composites. The results of the MTT test proved the excellent biocompatibility of the samples. An increment in Mo content also remarkably improved the biocompatibility and antimicrobial activity of the YSZ-20Mo sample.

Self-Lubricating Effect of WC/Y–TZP–Al2O3 Hybrid Ceramic–Matrix Composites with Dispersed Hadfield Steel Particles during High-Speed Sliding against an HSS Disk

WC/Y–TZP–Al2O3 hybrid ceramic–matrix composites (CMCs) with dispersed Hadfield steel particles were sintered and then tested at sliding speeds in the range of 7–37 m/s and contact pressure 5 MPa. Fast and low-temperature sinter-forging allowed obtaining micron-sized WC grains, submicron-sized alumina-reinforced yttria partially stabilized polycrystalline tetragonal zirconia (Y–TZP–Al2O3), and evenly distributed Hadfield steel grains. Such a microstructure provided new hybrid characteristics combining high hardness with high fracture toughness and tribological adaptation. The CMCs demonstrated low friction and high wear resistance that were better than those demonstrated by other composite materials such as, for example, MAX-phase composites, zirconia-base ceramics, ZrB2-SiC ceramics, and metal matrix WC–(Fe–Mn–C) composites. These good tribological characteristics were obtained due to the in situ mechanochemical formation of iron tungstates FeWO4 and Fe2WO6 on the worn surfaces of composite samples. These mixed oxides were included in multilayer subsurface structures that provided the self-lubricating and self-healing effects in high-speed sliding because of their easy shear and quasi-viscous behavior.

Editorial: Is Zirconia the Holy Grail of All-Ceramic Restorations?

Editorial: Is Zirconia the Holy Grail of All-Ceramic Restorations?

Effects of glass-ceramic spray deposition manipulation on the surface characteristics of zirconia dental restorations

A novel glass-ceramic spray deposition (GCSD) method was developed to modify the yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) surface and to enhance the bond strength between Y-TZP and resin cement. Five different experimental groups were characterized, non-treatment (NT), airborne particle abrasion (AB), GCSD without etching (GS), GCSD with 5% HF etching (GSE5), and GCSD with 9.5% HF etching (GSE9), to determine the optimal method for improving the bond strength. Scanning electron microscopy and an argon ion milling system were used to investigate the surface and cross-sectional microstructures. The changes in the surface characteristics of Y-TZP were analyzed via contact angle analysis, atomic force microscopy, X-ray diffraction, and energy-dispersive X-ray spectrometry. The bond strengths were determined using shear bond strength test. The results revealed that GCSD could produce a dense and uniform lithium disilicate glass-ceramic coating layer and infiltrate the Y-TZP surface. This coating resulted in superior micromechanical interlocking and increased hydrophilicity, thereby enhancing the bond strength between Y-TZP and resin cement (P < 0.05). The study findings indicated that GCSD accompanied by 5% HF etching for 100 s is optimal for strengthening the Y-TZP/resin cement bond, thereby providing a novel solution for dental bonding systems.

Optimization of particle size, dispersity, and conductivity of 8 mol% Y2O3 doped tetragonal zirconia polycrystalline nanopowder prepared by modified sol-gel method via activated carbon absorption

8 mol% Y2O3 doped tetragonal zirconia polycrystalline (8Y-TZP) ceramic nanopowders were synthesized via a novel modified sol-gel method employing zirconium carbonate basic as zirconium resources. The activated carbon as a dispersant was added to the precursor solution during the formation of the sol. The phase behavior, thermal decomposition, microstructure morphology, and electrochemical performance of nanopowders with the addition of activated carbons were investigated by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM), particles size distribution, and electrochemical impedance spectroscopy analysis (EIS). After adding the activated carbon, the average crystallite size of 8Y-TZP nanopowders decreased from about 53.16–33.51 nm when calcined at 900 ℃, and the 8Y-TZP nanopowders were produced loosely agglomerated. Meanwhile, compacts prepared by pressing the as-obtained 8Y-TZP nanopowders sintered to 98.8% relative density at 1600 ℃ and exhibited an average grain size of 0.89 µm, which brought a positive effect on ionic conductivity (0.079 S·cm−1).

Fabrication of highly bioactive zirconia ceramics via grain‐boundary activation for dental implants

AbstractYttria‐stabilized tetragonal zirconia polycrystal (Y‐TZP) ceramics with outstanding mechanical properties and aesthetic origins are expected to be used in dental implant applications. However, tetragonal zirconia ceramics are not bioactive, which affect the osseointegration and reliability as dental implant materials. Herein, in this study, Y‐TZP ceramics were modified by grain‐boundary activation via coating a bioactive glass (BG) sol with different content on the crystal surfaces of zirconia powder and followed by being gelled, dried, granulated, low‐temperature treated, molded and sintered at 1450°C for 3 h in air. The effects of BG content on the morphology, phase compositions, mechanical properties, in vitro mineralization ability and cell biological properties of the bioactivity modified Y‐TZP ceramics were evaluated. The BG additive did not affect the tetragonal–monoclinic phase transformation of ZrO2. However, the addition of BG decreased the flexural strength of the modified Y‐TZP ceramics compared to that of Y‐TZP. The in vitro mineralization results showed that a homogeneous apatite layer was produced on the surface of the Y‐TZP ceramics when they were immersed in the simulated body fluid for 21 days. The cell response results indicated that the bioactive surface modification of Y‐TZP ceramics could promote cell adhesion, propagation and osteogenic differentiation performance. Thus, our research results suggest that the highly bioactive Y‐TZP ceramics could be a potential candidate for dental implant material.

Biofilm formation and cell viability on monolithic zirconia with silver-doped sodalime glass

The present study evaluated the effect of glass application with and without silver-doped soda-lime glass on roughness, biofilm formation, cell viability and flexural strength of a zirconia. Samples of 3-YTZP (3 mol% yttria stabilized tetragonal zirconia polycrystals) were divided into: polished (P); glaze (G); glass infiltration (INF); 4% silver-doped soda-lime glass (Ag4); glass infiltration + 4% silver-doped soda-lime glass (INF–Ag4); 5% silver-doped soda-lime glass (Ag5); glass infiltration + 5% silver-doped soda-lime glass (INF–Ag5). Samples were submitted to the following analyses: roughness (Ra); free surface energy (FSE); colony-forming units count (log CFU/mL); scanning electron microscopy (SEM); cytotoxicity (MTT assay) and flexural strength. Ag5 had greater roughness and FSE, but less biofilm adherence. In the CFU, silver-doped soda-lime glass groups inhibited the growth of Candida albicans, while the Ag5 inhibited Streptococcus mutans and none of the groups was effective against Streptococcus sanguinis. In the qualitative evaluation, lower number of colonies in the Ag5 grew up, compared to the control groups (P; G and INF) for both C. albicans and S. mutans. Regarding the MTT assay, the Ag4, INF–Ag4 and INF–Ag5 obtained percentage of cell viability greater than 50%. Ag5 showed lower flexural strength when compared to the control groups, while the application of glass infiltration increased the flexural strength by formation of a graded region between zirconia-glass. In conclusion, Ag5 had the greatest antimicrobial effect, Ag4 and INF–Ag4 were the less cytotoxic and the INF was the most resistant to fracture. Therefore, INF–Ag4 conciliates the best performance in terms of antimicrobial and mechanical properties for a 3-YTZP.

Effects of di-ammonium citrate: polyvinylpyrrolidone as a complexion dispersants on 3Y-TZP slurries and sintered body properties

A wide application of 3 mol% Yttria-stabilized Tetragonal Zirconia Poly-crystalline (3Y-TZP) makes the concern of ceramic processing required to produce strong and reliable engineering ceramic products. In this study, we successfully improved the 3Y-TZP mechanical properties by paying great concern to the early processing of 3Y-TZP powder. Here, we used the concept of colloidal processing by manipulating the 3Y-TZP inter-particle force as a combination of steric and depletion stabilization. Di-ammonium citrate (DAC) was used to induce steric stabilization utilizing the DAC’s carboxyl group to strongly bond with the OH group of the 3Y-TZP. While Polyvinylpyrrolidone (PVP) which could not bond with 3Y-TZP, leaves it freely as an un-attached polymer in slurries and induces a depletion stabilization mechanism. Using the combination of steric and depletion stabilization, the YSZ slurries stability is improved, and a uniform and smaller particle size can be obtained. As the result, better microstructure and high mechanical properties of the sintered body, such as higher density and Vickers hardness, can be achieved. By comparing to the sintered body of 3Y-TZP containing just DAC and 3Y-TZP containing a combination of DAC and PVP, better-sintered body properties can be found for the 3Y-TZP containing the combination of DAC and PVP, and the results can be listed as follows: grain size reduced from 0.420 to 0.281 um, density is increased from 94.5 to 99.3%, and Vickers hardness increases from 1190 to 1305 HV.

Natural preparation of rice husk-derived silica and eggshell-derived calcium carbonate composite as a coating material for dental implant

Background: The world is in front of two emerging problems being scarceness of virgin re-sources for bioactive materials and the gathering of waste production. Employment of the surplus waste in the mainstream production can resolve these problems. The current study aimed to prepare and characterize a natural composite CaO-SiO2 based bioactive material derived from naturally sustained raw materials. Then deposit this innovative novel bioactive coating composite materials overlying Yttria-stabilized tetragonal zirconia substrate. Mate-rials and method; Hen eggshell-derived calcium carbonate and rice husk-derived silica were extracted from natural resources to prepare the composite coating material. The manufac-tured powder was characterized via Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), X-ray fluorescence (XRF), X-ray diffraction (XRD) and particle size analyzer. The bioactive composite was deposited through radiofre-quency (Rf) reactive magnetron sputtering overlying disc-shaped samples with a dimension of 10 mm diameter were prepared from partially sintered Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). Results: The particle size of the rice husk-derived ranged between (480.4 – 606.1) nm with a mean particle diameter of 541 nm. The eggshell derived calcium carbonate powder presented a particle size between (266.4-336) nm and a mean particle diameter of 299.9 nm. The XRD data revealed the crystalline nature and phase composition of the natural prepared calcium carbonate powder and demonstrate the monocrystalline nature of natural SiO2. FTIR spectrometer showed the emergence of novel spectra separated from the two innovative components. XRF analysis revealed that 99.4% of the rice husk is SiO2 while eggshell-derived powder is mainly composed of calcium oxide. Fe-SEM images of the coated zirconia exhibited average thickness of the natural CaCO3/SiO2 coat layer may reach to12.84 µ. Conclusion: The prepared composite derived from natural resource waste is suitable to be utilized as a coating material for ceramic dental implants with promising biological and mechanical properties.

Effect of bioactivation through acid/alkali process on the flexure strength of zirconia-based ceramics and composites

Zirconia-based ceramics such as tetragonal zirconia polycrystals (TZP) and alumina toughened zirconia (ATZ) are attractive as biomaterials because of their high strength, high fracture toughness, and excellent biocompatibility. However, their application has been limited by their bio-inertness, which prevents them from directly bonding to the living bone. Therefore, the bioactivation of zirconia materials through the acid/alkali process has been studied. Currently, there is little information on the low-temperature degradation (LTD) behavior associated with this treatment. In this study, we investigated the degradation behavior of TZP or ATZ by examining the monoclinic fraction and biaxial flexure strength after immersion in sodium hydroxide or phosphoric acid aqueous solutions. The results showed that the monoclinic fraction increased significantly, indicating LTD at the surface, whereas the strength was not affected. In addition, more apatite formation was observed on TZP than on ATZ after immersion in SBF for 7 days. In particular, under the phosphoric acid treatment condition, almost the entire surface was covered with apatite. The contact angle measurement showed the possibility of predicting the apatite formation ability during immersion in SBF.

Effect of ethyl cellulose coating as an evaluation agent against contamination on the bond strength of zirconia restorations: An in vitro study

Statement of problemDuring the trial placement of zirconia restorations, contamination of the bonding surface is inevitable. Although cleaning methods for contaminated surfaces have been described, a method of preventing saliva contamination of the bonding surface of zirconia restorations is lacking. PurposeThe purpose of this in vitro study was to investigate an ethyl cellulose coating as an evaluation agent to mitigate the effects of saliva contamination on the bond strength of zirconia restorations. Material and methodsExperimental groups representing different cleaning methods of tetragonal yttria-stabilized tetragonal zirconia polycrystal (4Y-TZP) surfaces were investigated for shear bond strength with a resin luting agent, and the failure mode was analyzed. The 9.0×7.0×5.0-mm zirconia blocks (n=72) were assigned as follows: Group N: uncontaminated control; Group CU: contaminated with saliva, followed by ultrasonic cleaning with ethanol; Group CI: contaminated with saliva, followed by application of a zirconia cleaner; Group PCW: preapplication of a zirconia primer, contaminated with saliva, followed by cleaning with water spray; Group ECU: precoating with the ethyl cellulose agent, contaminated with saliva, followed by removal of the agent in an ultrasonic bath with ethanol. Each group was divided into 3 subgroups (immediate, short-term aging, and long-term aging), and the shear bond strength was measured (n=24). To analyze the bonding surface characteristics, the contact angle was measured (n=5). The surfaces of the zirconia specimens in each experimental group were evaluated by using a field emission scanning electron microscope (n=5). Time-of-flight secondary ion mass spectroscopy was used for the chemical analysis of the conditioned surfaces (n=3). A 2-way analysis of variance (ANOVA) with main effect model for shear bond strength results and a 1-way ANOVA for contact angle data were performed as statistical analysis, followed by the Bonferroni post hoc test (α=.05). ResultsThe shear bond strength was significantly higher in the ECU group than in the groups with the other cleaning methods (P<.05). After the removal of ethyl cellulose with ethanol, the contact angle and surface topography were found to be similar to those of the control group, and no saliva contaminants were identified in the spectroscopy analysis. ConclusionsCoating with ethyl cellulose may protect the bonding surface of zirconia restorations from salivary contamination better than cleaning a contaminated surface.