3Y-TZP Surface Research Articles

The Influence of Alumina Airborne-Particle Abrasion on the Properties of Zirconia-Based Dental Ceramics (3Y-TZP)

The objective of this study was to assess the effect of airborne-particle abrasion with alumina particles of various sizes (50 μm, 110 μm, 250 μm) on the surface properties of 3Y-TZP (3 mol% yttria-stabilized tetragonal zirconia polycrystals). The analysis comprised the Vickers hardness test (HV1kp), a surface roughness evaluation (Ra, Rq, Rz, Rsk, Rsm, Rt, Vo, profile displays), and SEM–EDS microanalysis (scanning electron microscopy–energy-dispersive X-ray spectroscopy). Any statistical relationships were assessed using the Kruskal–Wallis one-way analysis-of-variance-by-rank test (p = 0.05). While airborne-particle abrasion with 50 µm alumina significantly increases the Vickers hardness of 3Y-TZP (1678.8 HV1kp), 110 μm and 250 μm alumina particles do not appear to have any such effect. The surface roughness of 3Y-TZP increases with the size of the alumina particles (Ra, Rq, Rz, Rt, Vo: vertical plane and retention volume assessment); a higher Rsm (horizontal plane assessment) was noted for specimens air-abraded with 250 µm alumina particles; air abrasion with 50 μm alumina particles yielded a symmetrical surface roughness profile (Rsk). The major topographic pattern of the surface of 3Y-TZP is altered by alumina airborne-particle abrasion, with larger alumina particles causing more severe changes. Aluminum traces on the 3Y-TZP surface are observed. The shape of the alumina particles is irregular, with rough edges; the size of the alumina particles plays a significant role in the air abrasion of zirconia-based dental ceramics, affecting their morphology and properties.

Effect of thermocycling on the mechanical properties, inorganic particle release and low temperature degradation of glazed high translucent monolithic 3Y-TZP dental restorations

The influence of thermocycling on the surface deterioration of glazed monolithic high translucent 3Y-TZP dental restorations is still unclear. The purpose of this study therefore was to evaluate low temperature degradation (LTD), elemental release and surface degradation pattern after five years of simulated clinical time. A total of 123 specimens were prepared from second-generation high translucent 3Y-TZP as per ISO 6872:2015 standards (3 mm × 4 mm × 30 mm). They were classified as per glazing and thermocycling protocol; group CPT, DGT and IGT. Glaze materials were applied on one surface of the specimen and subjected to a thermocycling in artificial saliva, four-point bending test, inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD). Flexural strength, characteristic strength and Weibull modulus values were derived from four-point bending test. Descriptive fractographic analysis of surfaces was conducted to observe the surface degradation characteristics and point of failure. Control/no glaze with thermocycling (CPT = 621.5, 1σ = 117.0 MPa) presented higher flexural strength values compared to glaze I with thermocycling (442.4, 1σ = 45.4 MPa) and glaze II with thermocycling (534.3, 1σ = 46.3 MPa). Characteristic strength from Weibull analysis also observed higher values (669.2 MPa) for the control specimens. XRD analysis showed that monoclinic volume fraction (Vm = 11.0, 1σ = 0.7%) was highest in control specimens. Fractographic analysis suggested that there was no correlation between the point of failure initiation and mean flexural strength values. Glazing protected the high translucent 3Y-TZP surface against LTD during thermocycling but negatively impacted on the flexural strength.

Effect of grinding parameters on surface integrity and flexural strength of 3Y-TZP ceramic

Grinding parameter effects on grinding forces, the surface phase transformation of tetragonal to monoclinic (t-m), surface residual stress, surface roughness, and flexural strength of 3 mol% Yttrium stabilized Tetragonal Zirconia Polycrystal (3Y-TZP) were investigated. The results have shown that the grinding force, compressive residual stress, and surface roughness increase with the increase in depth of cut and the feed speed. On the other hand, they decreased as the wheel speed increased. Additionally, grinding improved the 3Y-TZP surface t-m phase transformation. The m-phase content increased with the increase in the depth of cut and decreased as the wheel speed increased. Finally, the flexural strength of ground 3Y-TZP diminished with the increase in the cut depth. The fracture and smear were observed on the dry ground surface since it has a higher surface roughness compared to that of wet grinding.

3Y-TZP dip-coated with Zn-containing calcium silicate layers: development and characterization

Coating layers based on Ca3Si3O9, Ca2ZnSi2O7, and ZnSiO4 on 3Y-TZP ceramics were obtained by the dip coating process, using SiO2-CaO-P2O5-ZnO glass suspensions with Zn contents in the range of 0-20 mol%. The influence of the Zn content in the dip coating slips, the slip solid loading, and the 3Y-TZP surface porosity on the layer formation rate was studied. The Zn content of the dip coating slips as well as the slip solid loading greatly affected the slip viscosity, and consequently the liquid entrainment mechanism at the initial stage. The low dissolution rate of 20 mol% Zn-containing slips decreased the dip coating slip viscosity, whereas the lower stability of 10 mol% Zn-containing slips increased the slip viscosity. A significant increase in the initial layer thickness was produced either by using 10 mol% Zn-containing slips or by increasing the slip solid loading. The casting rate for longer immersion times was markedly accelerated by increasing the 3Y-TZP surface porosity. Sintered layers based on ZnSiO4 having the lowest thickness values were produced using the glass containing 20 mol% Zn. On the other hand, the 0 and 10 mol% Zn-containing glass produced thicker sintered layers mainly composed of Ca3Si3O9 and Ca2ZnSi2O7, respectively.

Effect of cementation delay on bonding of self-adhesive resin cement to yttria-stabilized tetragonal zirconia polycrystal ceramic treated with nonthermal argon plasma

Statement of problemNonthermal argon plasma (NTAP) has been reported to improve the bond strength of resin cements to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics. However, the effect of the inevitable delay before cementation and after treating Y-TZP ceramics with NTAP is unclear. PurposeThe purpose of this in vitro study was to investigate whether delays of 8, 12, and 24 hours between the Y-TZP ceramic treatment with NTAP and the cementation would affect the surface energy and the bond strength of a self-adhesive resin cement to Y-TZP ceramic. Material and methodsSixty plates and 50 blocks of 3Y-TZP ceramic were divided into 2 groups (n=30 and n=25): as-sintered (AS) and airborne-particle abraded with 50-μm Al2O3 (APA). These groups were further divided into 5 subgroups (n=6 and n=5) according to the delay between the NTAP treatment and the measurement of surface energy and microtensile bond strength (μTBS) evaluation: (0, 8, 12, and 24 hours). For both 3Y-TZP surface conditions (AS and APA), a control group without NTAP treatment was used (ASC and APAC). The surface energy (SE) was evaluated with a goniometer and the 3Y-TZP elemental composition with X-ray photoelectron spectroscopy (XPS). For the μTBS test, the 3Y-TZP ceramic blocks were cemented to composite resin blocks with a self-adhesive resin cement. After storage in distilled water at 37 °C for 24 hours, the 3Y-TZP-composite resin blocks were sectioned into beams and submitted to a μTBS test. Data were submitted to 2-way ANOVA and the Tukey HSD test (α=.05). ResultsFor the AS group, NTAP increased the SE irrespective of the delay before measurement: ASC<0 hour=8 hours=12 hours=24 hours (P<.05). For the APA group, except after 12 hours, NTAP also increased the surface energy (P<.05). XPS analysis showed an increase in the oxygen/carbon ratio after NTAP treatment for both groups. For the AS group, NTAP increased the μTBS after 0, 8, and 12 hours (P<.05), whereas for the APA group this occurred only after 8 hours (P<.05). For the AS and APA groups, the highest μTBS was reached after 8 hours (P<.05). ConclusionsTreatment of 3Y-TZP ceramic with NTAP improved the SE and increased the μTBS of self-adhesive resin cement to 3Y-TZP ceramic. These effects were time dependent, with better results at 8 hours after NTAP treatment.

Role of Magnesium and the Effect of Surface Roughness on the Hydroxyapatite-Forming Ability of Zirconia Induced by Biomimetic Aqueous Solution Treatment.

Zirconia is a well-known bioceramic for dental and orthopedic applications due to its mechanical and aesthetic properties. However, it lacks sufficient bioactivity to bond with the living bone. This study was aimed to induce bioactivity to tetragonal zirconia polycrystal (3Y-TZP) by simple biomimetic aqueous solution treatment. First, hydrofluoric acid (HF) etching was performed to enhance the surface roughness of the 3Y-TZP surface. Then, the samples were treated with two types of aqueous solutions containing calcium and phosphate ions (Ca-P solutions); one solution additionally contained magnesium (Mg) ions and the other without Mg ions. Finally, hydroxyapatite (HAp)-forming ability was evaluated by the conventional simulated body fluid (SBF) test, and the effect of Mg ions on the adhesive strength of the HAp layer to the roughened 3Y-TZP surface was also investigated. The results concluded that there were no noticeable differences in the effect of Mg ions on the HAp-forming ability, and both types of solution treatments resulted in dense HAp formation in 1 day SBF immersion. However, incorporation of Mg ions in one of the Ca-P solutions significantly improved the adhesive strength of the HAp layer to the HF-etched 3Y-TZP substrate compared to the Ca-P solution with no Mg ions.

Nanoroughening of sandblasted 3Y-TZP surface by alumina coating deposition for improved osseointegration and bacteria reduction

Zirconia-based (3Y-TZP) dental implants are being introduced as an alternative to established titanium counterparts. As 3Y-TZP’s bioinertness poses a challenge to osseointegration, modifications of the implants’ surface are necessary. Roughening is a common method to improve the cell response and should ideally combine micro- and nano-scale features. Here we show a simple synthesis procedure for the nano-roughening of sandblasted 3Y-TZP by precipitation of a nanostructured alumina coating. As-modified surfaces were characterised regarding their morphology and phase composition, roughness, wetting behaviour and zeta potential, and correlated to the behaviour of human osteoblasts and Staphylococcus aureus bacteria. Osteoblasts were successfully cultured on all surfaces regardless of their modification. Surfaces exhibiting a combination of micro- and nano-roughening performed best regarding initial attachment and proliferation of osteoblasts. Alumina-coated surfaces also limited the bacterial adhesion.

Surface properties of dental zirconia ceramics affected by ultrasonic scaling and low-temperature degradation.

Zirconia (3Y-TZP) dental prostheses are widely used in clinical dentistry. However, the effect of ultrasonic scaling performed as a part of professional tooth cleaning on 3Y-TZP dental prostheses, especially in conjunction with low-temperature degradation (LTD), has not been fully investigated. The present study aimed to evaluate the influence of ultrasonic scaling and LTD on the surface properties of 3Y-TZP in relation to bacterial adhesion on the treated surface. 3Y-TZP specimens (4 × 4 × 2 mm) were polished and then subjected to autoclaving at 134°C for 100 h to induce LTD, followed by 10 rounds of ultrasonic scaling using a steel scaler tip for 1 min each. Surface roughness, crystalline structure, wettability, and hardness were analyzed by optical interferometry, X-ray diffraction analysis, contact angle measurement, and nano-indentation technique, respectively. Subsequently, bacterial adhesion onto the treated 3Y-TZP surface was evaluated using Streptococcus mitis and S. oralis. The results demonstrated that the combination of ultrasonic scaling and LTD significantly increased the Sa value (surface roughness parameter) of the polished 3Y-TZP surface from 1.6 nm to 117 nm. LTD affected the crystalline structure, causing phase transformation from the tetragonal to the monoclinic phase, and decreased both the contact angle and surface hardness. However, bacterial adhesion was not influenced by these changes in surface properties. The present study suggests that ultrasonic scaling may be acceptable for debridement of 3Y-TZP dental prostheses because it did not facilitate bacterial adhesion even in the combination with LTD, although it did cause slight roughening of the surface.

Bonding strategies to full-contour zirconia: Zirconia pretreatment with piranha solution, glaze and airborne-particle abrasion

This study aimed to evaluate the effect of various zirconia surface pretreatments on the adhesion between full contour 3Y-TZP zirconia and glaze, and the shear bond strength (SBS) between glazed/3Y-TZP and resin cement. Specimens were allocated into groups: GL-glaze; AL+GL-sandblasting with Al2O3+GL; CJ+GL-tribochemical silica coating (Cojet®/CJ)+GL; PS+GL-piranha solution+GL; and CJ. Adhesion between 3Y-TZP and GL was evaluated using the scratch test. Surface topography and glaze thickness were evaluated by using a scanning electron microscope (SEM). For SBS, glazed/3Y-TZP surface was etched with hydrofluoric acid and a silane was applied. For CJ only the silane was applied. Samples were tested after 24h (24h wet) or after 15,000 thermal cycles and 90 days storage (thermocycled). After SBS, the type of failure was classified as: adhesive, mixed or cohesive. The data were analyzed using two-way ANOVA and Tukey's test. SEM analysis after scratch test revealed circular cracks in the GL group and conformal cracks in the others groups. SEM micrographs suggested that zirconia specimens submitted to airborne-particle abrasion presents rougher and porous surface when compared to surfaces treated with GL and PS. The glaze layer was approximately 1.86µm thick in all groups. After 24h, SBS test showed highest values for AL+GL and CJ+GL and were significantly higher when compared to the GL group. Differences were not significant between PS+GL and the other groups. After aging (thermocycling+storage), groups GL and CJ presented no statistically significant difference compared to 24h and aged AL+GL, CJ+GL and PS+GL groups. The predominant type of failure was mixed. 3Y-TZP surface treatment with glaze application could be considered as an alternative treatment, since it yielded a similar resin bond strength without the need for airborne-particle abrasion.

Enhancing the bioactivity of yttria-stabilized zirconia immobilized with adhesive peptide using l-dopa as cross-linker

To resolve the disadvantages of the bio-inert nature of zirconia ceramics and their poor bonding to bone tissue, surface modification to enhance tissue integration usually has to be performed. In this study, we developed a simple, efficient, and organic solvent-free biomimetic modified strategy through the use of l-dopa, which is known to have strong adhesive behavior, as a cross-linker for immobilization with adhesive peptide. 3Y-TZP was first immersed into l-dopa solution to form a strongly adhesive coating. RGD peptides were then immobilized onto the l-dopa-grafted surface. Several characterization analyses, including static contact angle measurement, FTIR spectroscopy, and Bradford staining, showed that RGD peptides were successfully immobilized onto the 3Y-TZP surface through the l-dopa linker. In vitro assay revealed that a significant increase in MG-63 osteoblast cell attachment, proliferation, and differentiation was observed from SEM, WST-1, and ALP activity on the l-dopa-grafted 3Y-TZP surface with the immobilized adhesive peptide. Thus, the results of this study suggest that l-dopa can be used as a cross-linker to immobilize adhesive peptides onto a 3Y-TZP surface and further enhance bioactivity.

Improvement in the Tensile Bond Strength between 3Y-TZP Ceramic and Enamel by Surface Treatments

This study examined the effects of 3 mol % yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramic surface treatments on the tensile bond strength and surface characteristics of enamel. To measure the tensile bond strength, the 3Y-TZP and tooth specimens were manufactured in a mini-dumbbell shape and divided into four groups based on the type of 3Y-TZP surface treatment: polishing (P), 110 µm alumina sandblasting (S), 110 µm alumina sandblasting combined with selective infiltration etching (SS), and 110 µm alumina sandblasting combined with MDP (10-methacryloyloxydecyl dihydrogen phosphate)-containing silane primer (SP). After surface treatment, the surface roughness, wettability, and surface changes were examined, and the tensile bond strength was measured. The mean values (from lowest to highest) for tensile bond strength (MPa) were as follows: P, 8.94 ± 2.30; S, 21.33 ± 2.00; SS, 26.67 ± 4.76; and SP, 31.74 ± 2.66. Compared to the P group, the mean surface roughness was significantly increased, and the mean contact angle was significantly decreased, while wettability was increased in the other groups. Therefore, surface treatment with 110 µm alumina sandblasting and MDP-containing silane primer is suitable for clinical applications, as it considerably improves the bond strength between 3Y-TZP and enamel.

Osteogenesis ability of biomimetic modified 3Y-TZP ceramic using chemical treatment

In this study, RGD peptide derived from extracellular matrix proteins was employed to modify the surface of yttria-tetragonal zirconia polycrystal (3Y-TZP) to promote cell adhesion. The surface of 3Y-TZP ceramic specimens was first modified using chemical treatment with aqueous solutions of H3PO4, CH3COOH, and NaOH, for the formation of Zr–OH surface functional groups. Then, the RGD peptide was immobilized on the surface of the 3Y-TZP through silanization method, with covalent bonding via the Zr–OH surface functional groups. From this study, the RGD peptide can successfully be grafted onto the chemical modified 3Y-TZP surface. The –OH functional groups formed on the surface of 3Y-TZP after acid/alkaline chemical treatment contribute to the grafting reaction of RGD peptides. The use of phosphoric acid solution in 3Y-TZP surface treatment before RGD peptide grafting for biomimetic modification can significantly enhance cell adhesion, proliferation, and differentiation.

Relationship between Surface Residual Stress Fields and Hydrothermal Environment on Low Temperature Aging of 3Y-TZP

Phase stability of 3 mol% yttria stabilized polycrystalline zirconia ceramics (3Y-TZP) was evaluated by aging test in water vapor environment and Raman spectroscopic technique. In our previous study, it has been confirmed that phase stability was improved by controlling sintering temperature. In this study, we pointed our attention and evaluated the influence of surface conditions related to machining and to heat treatment, thus monitoring the changes in phase transformation fraction and residual stress on the material surface. From the results of aging test, an increase in monoclinic fraction was observed for grinded surfaces as compared with polished surfaces. Samples subjected to heat treatment after machining showed improved phase stability. A Vickers indentation print was also introduced on a 3Y-TZP surface, and the relationship between surface condition and low temperature aging was evaluated in the neighborhood of the print. We found that the residual stress fields induced in phase-transformed areas were enhanced during low temperature aging, and that phase stability was improved by heat treatment.

Effects of surface-finishing condition and annealing on transformation sensitivity of a 3 mol.% Y 2O 3 stabilized tetragonal zirconia surface under interaction of lubricant

Transformation behavior of a 3 mol.% Y 2O 3 stabilized tetragonal zirconia (3Y-TZP) surface is affected by not only stresses but also environmental conditions. In this paper, effects of surface-finishing conditions such as grinding and lapping and annealing after them on transformation sensitivity of a 3Y-TZP surface in hot oil are evaluated by tetragonal phase content, calculated from X-ray diffraction patterns. The depth of transformed layer of the specimens, which have been held in oil at 473 K, is also measured by a microscopic examination of cross-sections. The work-affected layer of the worked surface is evaluated by the value of IP T(002)/IP T(200) where IP T(002) and IP T(200) are the intensities of the tetragonal phase peaks T(002) and T(200) at 2θ≅35° in an X-ray diffraction pattern, respectively. When the value of IP T(002)/IP T(200) of the worked surface is larger than that of the sintered one, as in the surfaces ground by #200 and #400 diamond wheels, the following annealing at ∗ about 1473 K is effective at improving resistibility of surfaces to phase transformation in hot oil. The annealed specimen, however, whose work-affected layer is removed by lapping prior to the annealing treatment, shows the same transformation sensitivity as the sintered one. It is also shown that the compressive residual stress has a significant effect towards increasing the resistibility of surfaces to phase transformation.