Flexural Strength Of Zirconia Research Articles

Effect of Hydrothermal, Chemical, and Mechanical Degradation on Flexural Strength and Phase Transformation of Ground, Glazed, and Polished Zirconia.

Objectives: Evaluation of the effect of grinding on flexural strength of zirconia after low temperature degradation (LTD) and pH-cycling. Materials and Methods: Sixty-four bar-shaped specimens of yttria-stabilized tetragonal polycrystalline zirconia were milled, sintered, wet-polished, and divided into 8 groups (N=8). The four control groups were not aged while artificial aging was performed in the 4 experimental groups in three steps including LTD in steam for 40h, pH-cycling, and tooth brushing for artificial aging. All groups underwent surface preparations as follows: standard polishing without surface treatment (Sp), grinding with a blue-yellow band diamond instrument (Gr); grinding with a diamond rotary instrument (DRI) and then over-glazing (Gl); grinding with a DRI followed by two-step intraoral polishing (Po); standard polishing and aging (Sp-Ag); grinding and aging (Gr-Ag), grinding, over-glazing and aging (Gl-Ag); and grinding, polishing and aging (Po-Ag). Monoclinic content was assessed in one specimen of each group by X-ray diffraction (XRD). The 3-point flexural strength test was performed in a universal testing machine. The results were analyzed with two-way ANOVA and Tukey's test (α=0.05). Results: Mean flexural strength (Mpa) was significantly higher in groups Gr and Po compared to group Sp (both, P<0.0001) and group Gl (both, P<0.0001). In XRD analyses, the highest monoclinic phase before aging was observed in group Gr (12.6%), and after aging in group Gr-Ag (51.2%). Conclusion: Grinding and polishing increased the flexural strength, while glazing did not exhibit any significant effect on this parameter. Furthermore, aging did not adversely affect flexural strength.

Comparative effects of tungsten, diamond burs and laser for residual adhesive removal after orthodontic debonding on flexural strength, surface roughness and phase transformation of high-translucent zirconia: An in vitro study

ObjectivesInformation regarding the effects of orthodontic bracket debonding on zirconia restorations, and the preferred method for residual adhesive removal from the zirconia restoration surface is lacking. Thus, this study aimed to assess the effects of different methods of residual adhesive removal after orthodontic bracket debonding on flexural strength, surface roughness, and phase transformation of high-translucent (HT) zirconia. Materials and methodsThis in vitro study evaluated 72 bar-shaped HT zirconia specimens; 18 specimens were assigned to the control group. Metal brackets were bonded to the remaining specimens by resin cement. After bracket debonding, the residual adhesive on the surface of specimens was removed by three methods (n=18): a 30-flute tungsten-carbide (TC) bur at low speed, an ultrafine diamond bur at high speed, and Er:YAG laser irradiation. The surface roughness (Ra and Rz) was measured. X-ray diffraction (XRD) analysis was carried out, and the flexural strength was measured as well. Data were statistically analyzed (α=0.05). ResultsBefore polishing, all methods increased the Ra and Rz values (P<0.05) except for the diamond bur yielding a Rz value comparable to that of the control group. The Ra values of the test groups were comparable after polishing, and still higher than that of the control group (P<0.05). The flexural strength of all three test groups was comparable (P>0.05), and significantly lower than that of the control group (P<0.001). The monoclinic phase was not observed in any group. ConclusionsOrthodontic bracket debonding adversely affects the surface roughness and flexural strength of zirconia despite polishing.

Effect of sintering condition and low-temperature degradation on the flexural strength and phase transformation of zirconia

Statement of problemThe traditional sintering of zirconia takes an extended time, and accelerated treatments have been developed to reduce treatment time and manufacturing costs. Studies evaluating the effect of sintering time on the mechanical properties of zirconia are lacking. PurposeThe purpose of this in vitro study was to evaluate the effect of the sintering condition and the low-temperature degradation (LTD) of zirconia on the flexural strength of monolithic zirconia. Material and methodsZirconia specimens (LUXEN Enamel) were sintered at 1500 °C, 1530 °C, and 1560 °C for 4, 5, 6, 7, and 12 hours and subjected to LTD (n=10). Control specimens were assessed in the nontreated condition. The 3-point flexural strength was measured by using a universal testing machine. The crystal phases of the specimens were compared and quantitatively analyzed through X-ray diffraction (XRD) analysis, and the crystal grain size was measured by using a field emission scanning electron microscope (FE-SEM). Two-way ANOVA and the independent sample t test were used to analyze the experimental results (α=.05). ResultsIn the group not subjected to LTD, there was no difference in flexural strength according to the change in sintering temperature and sintering time (P>.05). The group subjected to LTD showed a difference in flexural strength according to sintering time difference (P<.001). The flexural strength of the zirconia with LTD exposure increased compared with that of the zirconia specimen not subjected to LTD (P<.001). With LTD exposure, cubic and monoclinic crystals increased, tetragonal crystals decreased, and the particle size increased. As the sintering temperature increased, the particle size increased, but not according to the sintering time. ConclusionsAt all sintering times, the flexural strength of zirconia was over 800 MPa, which is the minimum flexural strength of a 4-unit or longer prosthesis as specified in the International Organization for Standardization (ISO) 6872. With LTD exposure, the increase in the flexural strength of zirconia was associated with the phase change from tetragonal to monoclinic.

EFFECT OF AIR-BORNE PARTICLE ABRASION/SINTERING SEQUENCE ON THE FLEXURAL STRENGTH OF ZIRCONIA.

Introduction: zirconia represents a valuable material that combines both color acceptance and ability to withstand high loads. It had been reported that sintering of zirconia followed by air-borne particle abrasion affect its strength. The effect of air-borne particle abrasion/sintering sequence on shear bond strength of resin cements to zirconia was found non-significant; however the effect of sequence on the flexural strength has not been reported. The Ivoclare Vivadent manufacturer recommendation is to sinter the zirconia before subjecting it to air-borne particle abrasion. Aim of the study: to evaluate the effect of air-borne particle abrasion/sintering sequence on the flexural strength of zirconia. Materials and Method: forty bars of dimensions (26 × 6 × 1.5 millimeter) were fabricated from IPS e-max zircad. The specimens was divided into two equal groups (A and B). Group A (AS) were subjected to air-borne particle abrasion followed by sintering. However specimens of group B (SA) were sintered before air-borne particle abrasion. Specimens of each group were subjected to X-Ray Diffraction to show monoclinic-tetragonal phases percentage. Three-point loading was applied to all specimens to measure the flexural strength using a Universal Testing Machine. Results: At statistically significant level p ≤ 0.05. Group SA has showed significantly higher flexural strength compared to group AS. Air-borne particle abraded surface of group SA showed the highest amount of monoclinic phase crystals after X-Ray Diffraction analysis. Conclusion: Air-borne particle abrasion/sintering sequence affects zirconia’ flexural strength. And air-borne particle abrasion surface treatment induces tetragonal to monoclinic phase transformation in fully sintered zirconia.

Laser-assisted production of HAp-coated zirconia structured surfaces for biomedical applications

ObjectivesThe aim of this study was to develop a novel design for implants surface functionalization through the production of HAp-coated zirconia structured surfaces by means of hybrid laser technique. The HAp-rich structured surfaces were designed to avoid hydroxyapatite (HAp) coating detachment from the zirconia surface during implant insertion, thus guaranteeing an effective osseointegration. Materials and methodsThe functionalization process of zirconia surface started by creating micro-textures using a Nd:YAG laser and subsequent deposition of a HAp coating on the designated locations by dip-coating process. Afterwards, a CO2 laser was used to sinter the HAp coating. The potential of the HAp-coated zirconia structured surfaces was inspected concerning HAp bioactivity preservation, surface wettability, HAp coating adhesion to the textured surfaces and mechanical resistance of zirconia, as assessed by different approaches. ResultsThe functionalized surfaces exhibited a superhydrophilic behavior (2.30 ± 0.81°) and the remaining results showed that through the hybrid strategy, it is possible to maintain the HAp bioactivity as well as promote a strong adhesion of HAp coating to the textured surfaces even after high energy ultrasonic cavitation tests and friction tests against bovine bone. It was also verified that the flexural strength of zirconia (503 ± 24 MPa) fulfills the strict requirements of the ISO 13356:2008 standard and as such is expectable to be enough for biomedical applications. SignificanceThe promising results of this study indicate that the proposed surface design can open the window for manufacturing zirconia-based implants with improved bioactivity required for an effective osseointegration as it avoids the coating detachment problem during the implant insertion.

The effect of short and long duration sintering method on microstructure and flexural strength of zirconia

The effect of short and long duration sintering method on microstructure and flexural strength of zirconia

MECHANICAL EVALUATION OF POLYETHERETHERKETONE COMPARED WITH ZIRCONIA AS A DENTAL IMPLANT MATERIAL

INTRODUCTION: Dental implants are currently one of the main pillars of restorative dentistry. Titanium and its alloys were and still are the gold standard for dental implant materials. However, Titanium is not a perfect material and has many drawbacks thus the search for a more ideal material is ongoing. Zirconia and Polyetheretherketone are two viable alternatives to titanium as dental implant materials. They show different mechanical behavior invitro and invivo, so they are investigated and compared to each other. OBJECTIVES: Evaluate and compare the different material properties of Polyetheretherketone and yttrium-stabilized tetragonal polycrystalline zirconia when used as dental implant material. MATERIALS AND METHODS: Microbars of zirconia and Polyetheretherketone were prepared using precision cutter and low speed micro motor under water cooling and used to assess the following properties for the two materials: 1) Vickers Microhardness 2) Flexural strength before and after cyclic loading RESULTS: There was a highly significant difference between hardness of zirconia and Polyetheretherketone. There was also a highly significant difference between flexural strength of zirconia and Polyetheretherketone (both before and after cyclic loading). There was significant decrease in flexural strength of zirconia after cyclic loading. No significant difference was found for Polyetheretherketone after cyclic loading. CONCLUSIONS: Polyetheretherketone is a promising alternative to titanium and zirconium as a dental implant material.

Investigating the Effect of Different Surface Treatments on Vickers Hardness and Flexural Strength of Zirconium and Lithium Disilicate Ceramics.

To investigate the effect of different surface treatments on Vickers hardness and flexural strength of zirconia and lithium disilicate ceramics. 50 zirconia and 50 lithium disilicate ceramic specimens were used. After identifying one group as the control, grinding, sandblasting, CoJet, and Er:YAG laser were applied on the surface of specimens (n = 10). After applying Vickers hardness test to specimens, flexural strength test was performed. The data were analyzed with two-way ANOVA and Duncan's multiple comparisons tests. There were statistically significant differences found between surface treatment groups in terms of Vickers hardness of zirconia and lithium disilicate ceramics (p<0.001), but there were no statistically significant differences found between surface treatment groups in terms of flexural strength (p>0.05). Surface treatments could affect the hardness of ceramics. Therefore, was zirconia found to be harder and more durable than lithium disilicate ceramics.

Effect of electrical discharge machining on dental Y-TZP ceramic-resin bonding

PurposeThe study determined (i) the effects of electrical discharge machining (EDM) on the shear-bond strength (SBS) of the bond between luting resin and zirconia ceramic and (ii) zirconia ceramic's flexural strength with the three-point bending (TPB) test. MethodsSixty 4.8mm×4.8mm×3.2mm zirconia specimens were fabricated and divided into four groups (n=15): SBG: sandblasted+silane, TSCG: tribochemical silica coated+silane, LTG: Er:YAG laser treated+silane, EDMG: EDM+silane. The specimens were then bonded to a composite block with a dual-cure resin cement and thermal cycled (6000 times) prior to SBS testing. The SBS tests were performed in a universal testing machine. The SBS values were statistically analyzed using ANOVA and Tukey's test. To determine flexural strength, sixty zirconia specimens were prepared and assigned to the same groups (n=15) mentioned earlier. After surface treatment TPB tests were performed in a universal testing machine (ISO 6872). The flexural strength values were statistically analyzed using ANOVA and Tukey's test (α=0.05). ResultsThe bond strengths for the four test groups (mean±SD; MPa) were as follows: SBG (Control), 12.73±3.41, TSCG, 14.99±3.14, LTG, 7.93±2.07, EDMG, 17.05±2.71. The bond strength of the EDMG was significantly higher than those of the SBG and LTG (p<0.01). The average flexural strength values for the groups SBG (Control), TSCG, LTG and EDMG were 809.47, 800.47, 679.19 and 695.71MPa, respectively (p>0.05). ConclusionsThe EDM process improved the SBS. In addition, there was no significant adverse effect of EDM on the flexural strength of zirconia.

Factors affecting the mechanical behavior of Y-TZP

AimThe aim was to evaluate the influence of sandblasting with various propulsion pressures on the phase transformation, flexural strength and Weibull modulus of a yttria stabilized tetragonal zirconia polycrystalline ceramic (Y-TPZ). In addition, the susceptibility of cyclic loading and low-temperature degradation under two different conditions (chemical and thermal aging) was investigated. Materials and methodsThe specimens [105bar-shaped specimens (19.3×14.5×1.3mm3)] were equally divided into seven groups (n=15) according to the test protocols. The specimens in control group received no surface treatment (Group A). Groups B1, B2 and B3 were airborne-particle abraded with 110μm Al2O3 particles at 200kPa, 400kPa and 600kPa (2bar, 4bar and 6bar) pressure, respectively. Group C was submitted to mechanical cyclic loading under 200N 20,000 times sinusoidal loading/unloading at a frequency of 10Hz between 10% and 100% load in distilled water at 37°C. Group D was submitted to thermal degradation in an autoclave at 134°C under additional 200kPa pressure for 5h. Group E was immersed in 4% acetic acid at 80±5°C for 168h as chemical degradation testing. Following each treatment protocols, the three-point flexure test was used to calculate the flexural strength. Additionally, X-ray diffraction analysis was used to estimate the relative amount of monoclinic phase. The reliability of strength was assessed through the Weibull distribution. Statistical analysis was conducted with one-way ANOVA and Tukey׳s pairwise multiple comparisons. The treated and fractured surfaces were observed with SEM. ResultsStatistical analysis revealed that there were significant differences among the flexural strength results of all tested groups (F=4.510, p<0.05). Group B2 demonstrated the highest strength values, whereas Group E showed the lowest (625.86±123.57; 466.56±91.50, respectively). Weibull moduli of all tested groups were statistically significant and ranging from 4.3 to 8.3. A greater amount of monoclinic phase was determined in the specimens of D, E and B3 groups (25.43%, 20.89% and 19.71%, respectively). However, lower amount was observed in groups A, B1 and B2 (10.02%, 13.35% and 15.19%, respectively). ConclusionsThe present study suggested that flexural strength of zirconia was significantly decreased by chemical degradation. In addition, surface conditioning, cyclic fatigue and thermal, chemical degradation conditions significantly changed the structural reliability of the material's strength.

Influence of Different Thickness of Zirconia Core on the Flexural Strength of Bilayered Ceramics in Artificial Saliva

To study the effect of different core thickness on the flexural strength of zirconia and feldspathic ceramics. Bilayered zirconia-feldspathic samples of three commercial brands were made in three different thickness(n=10): 0.5 mm, 0.8 mm and 1.0 mm respectively. On zirconia core specimens of each thickness, feldspathic dentin porcelain was added to reach a total crown thickness of 2 mm. Samples were stored in artificial saliva with neutral pH for 10 days at 37°C. Flexural strength was conducted with 3-point bending test. Data were analyzed by one-way ANOVA, and multiple comparisons were performed using Student-Newman-Keuls test(α=0.05). The measurement of 1.0 mm group was higher than the other groups, and 0.5 mm group was the lowest(P＜0.05), regardless of any commercial brand. Commercial dental zirconia blocks had varied flexural strength, Zirkonzahn expressed highest value in any thickness group compared with the other materials. Moreover, the fracture mode of zirconia bilayered composites was different in this study, 0.5 mm and 0.8 mm groups exhibited higher number of fragments and appeared to delamination compared with 1.0 mm group. So we infer that the thickness of core can have an effect on the flexural strength of bilayered zirconia-feldspathic crown, as well as different kinds of materials.

Influence of different Thickness of Zirconia Core on the Flexural Strength in Article Saliva

To Study the Effect of Different Core Thickness on the Flexural Strength of Zirconia and Feldspathic Ceramics. Bilayered Zirconia-Feldspathic Samples of Three Commercial Brands were Made in Three Different Thickness(n=10): 0.5 Mm, 0.8 Mm and 1.0 Mm Respectively. on Zirconia Core Specimens of each Thickness, Feldspathic Dentin Porcelain was Added to Reach a Total Crown Thickness of 2 Mm. Samples were Stored in Artificial Saliva with Neutral Ph for 10 Days at 37°C. Flexural Strength was Conducted with 3-Point Bending Test. Data were Analyzed by One-way ANOVA, and Multiple Comparisons were Performed Using Student-Newman-Keuls Test(α=0.05). the Measurement of 1.0 Mm Group was Higher than the other Groups, and 0.5 Mm Group was the Lowest(P＜0.05), Regardless of any Commercial Brand. Commercial Dental Zirconia Blocks had Varied Flexural Strength, Zirkonzahn Expressed Highest Value in any Thickness Group Compared with the other Materials. Moreover, the Fracture Mode of Zirconia Bilayered Composites was Different in this Study, 0.5 Mm and 0.8 Mm Groups Exhibited Higher Number of Fragments and Appeared to Delamination Compared with 1.0 Mm Group. so we Infer that the Thickness of Core can have an Effect on the Flexural Strength of Bilayered Zirconia-Feldspathic Crown, as well as Different Kinds of Materials.

Influence of pre-treatments on flexural strength of zirconia and debonding crack-initiation strength of veneered zirconia.

The aim of the present study was to assess the influence of pre-treatments of zirconia by sandblasting and/or heat treatment on the flexural strength of zirconia and debonding/crack-initiation strength of porcelain-veneered zirconia ceramic. Zirconia ceramic specimens were divided into four groups according to treatment (grinding as controls, sandblasting, heat treatment at 1000°C for 10 min, and heat treatment after sandblasting). The porcelain- veneered zirconia specimens were also prepared. The zirconia specimens were subjected to three-point bending tests, and flexural strength was calculated. The debonding/crack-initiation strength of porcelain-veneered zirconia ceramic was measured according to ISO 9693. X-ray diffractometry (XRD) was used to estimate the relative amount of monoclinic phase. There was no significant difference in flexural strength between the four treatments (p > 0.05). The highest amount of monoclinic phase was found after sandblasting. No monoclinic phase was obtained from heat treatment and heat treatment after sandblasting groups, and these two groups showed significantly higher debonding/crack-initiation strength than other two groups (p < 0.05). All specimens failed within the veneering porcelain. No elements of veneering porcelain were detected on the zirconia side at the interface using EPMA (electron probe microanalyzer). The present study suggests that the pre-treatment of zirconia with heat treatment after sandblasting prior to firing porcelain does not affect the debonding/crack-initiation strength of porcelain-veneered zirconia ceramic.

Surface Microhardness and Flexural Strength of Colored Zirconia

The surface microhardness and flexural strength of colored zirconia were examined. Two groups of zirconia disks (1mm thick, 20mm in diameter) within 5 disks each were shading with the same coloring liquids IL2 (Vita Classic-scale) when another group of 5 disks measured in no color. The shading time of one group was 3s and that of the other group was prolonged to 30s. The mechanical properties were tested after sintering at 1500°C. Data were evaluated using ANOVA analysis. Disks of shading 30s showed a lower strength 712  53 MPa. The value of 3s was 853  46 MPa. There were no significant difference on microhardness between the two shading time. Prolonged the shading time lowered the biaxial flexural strength of zirconia ceramic, but shading time did no effect on surface microhardness.

Effect of particle deposition protocols on flexural strength of zirconia after cyclic loading

Effect of particle deposition protocols on flexural strength of zirconia after cyclic loading