Μm Al2O3 Research Articles

Enhanced thermal conductivity and rheological performance of epoxy and liquid crystal epoxy composites with filled Al2O3 compound

The heat dissipation capability of electrical insulation materials has been the bottleneck affecting the development of high power density electrical equipment and electronic devices. In this study, we investigated the effect of filler compounding, filler surface treatment and liquid crystal structure on the microscopic morphology, rheological performance, thermal conductivity and dielectric performance of the epoxy resin (EP) and liquid crystal epoxy resin (LCEP) composites. The results show that the composite with 45 μm and 3 μm Al2O3 compound fillers at a ratio of 3:2 showed a reduction in viscosity for about 1/3-1/30 and an enhancement in thermal conductivity for about 10%–40% compared to the other filler compounds with different filler size and ratio. The filler surface treatment by silane coupling agent diminished the viscosity by up to 90% and simultaneously enhanced the thermal conductivity of the composite by about 10%. The composite with LCEP matrix showed a thermal conductivity up to 2.47 W/(m·K) at 80 wt% filler loading, which is about 0.54 W/(m·K) higher than that of EP based composite. Moreover, the filler surface treatment can improve the electrical breakdown strength and volume resistivity of the composites. The results indicate that filler compound optimization, filler surface treatment and LCEP matrix can significantly improve the thermal conductivity, rheological and dielectric properties of the composites.

Fatigue behavior of zirconia with microgrooved surfaces produced using femtosecond laser.

Femtosecond laser is a promising surface treatment tool for zirconia implant. In this study, the fatigue behavior of zirconia specimens with microgrooved surfaces formed by femtosecond laser is reported. One hundred sixty CAD/CAM zirconia bars (20mm × 4mm × 1.4mm) were evenly divided into four groups with different surface: as sintered; sandblasted with 110μm Al2O3; femtosecond laser produced microgrooves having 50μm width, 30μm depth, and 100μm pitch; microgrooves having 30μm width, 20μm depth, and 60μm pitch. The femtosecond laser formed micro/nanostructured microgrooves with precise size on zirconia surfaces. XRD analysis indicated that microgrooved surface showed no obvious tetragonal-to-monoclinic phase transformation. The fatigue strength of sandblasted specimens (728MPa) was significantly higher than that of as sintered specimens (570MPa). However, the fatigue strength of specimens with microgrooved surface decreased to about 360-380MPa. The results suggest femtosecond laser is an effective technique to regulate the surface microtopography of zirconia, while further investigations are needed to improve its fatigue behavior.

Optimization of chemical mechanical polishing of (010) β-Ga2O3

Smooth (< 0.5 nm rms) and subsurface damage-free (010) β-Ga2O3 was achieved with low-pressure chemical mechanical polishing. An applied pressure of 1 kPa along with colloidal silica and poromeric polyurethane polishing pads rotating at 30 rpm was found to be the optimal polishing parameters for (010) β-Ga2O3. Using higher pressures typically employed in the current literature induced subsurface damage in the substrates. Diffuse scatter intensity of triple-axis x-ray rocking curves was used to determine the presence of subsurface lattice damage, which was quantified by measuring peak widths below the half maximum (i.e., FWXM where X < 0.5). The initially rough surfaces of (010) β-Ga2O3 substrates due to wafer slicing and grinding were lapped and polished. A 5 μm Al2O3 slurry followed by a 0.3 μm Al2O3 slurry was used as the primary lap material removal step. The material removal rates were ∼20 and ∼9 μm/h, respectively. Then, chemical mechanical polishing was performed using colloidal alumina followed by colloidal silica. The removal rates were ∼1.3 and ∼0.4 μm/h, respectively. Only colloidal silica showed the complete removal of subsurface damage. The final (020) β-Ga2O3 rocking curve FWHM was ∼13″ and FW(0.001)M was ∼120″, which matches the widths of commercially available pristine (010) β-Ga2O3. A final cleaning step using dilute bleach and dilute citric acid to remove residual silica slurry particles from the surface was demonstrated.

Effects of different surface conditioning protocols on shear strength of orthodontic brackets bonded to CAD/CAM materials

The aim of this study was to evaluate the effects of different surface conditioning method combinations on the shear strength of orthodontic brackets bonded various temporary crown materials used in computer aided design and computer aided manufacturing systems. 100 polymethyl methacrylate, 100 bis-acrylic composite and 100 polyetherketoneketone surfaces were prepared from provisional temporary crown blocks. Five different conditioning protocols (etching with 9.6 % hydrofluoric acid, sandblasting with 50 μm Al2O3 particles, roughening with ultrafine diamond bur, Er,Cr:YSGG laser irradiating and priming with methylmethacrylate monomer were applied to the surfaces for each material group. Shear test was performed to half of the bonded samples after 24 hours while the other half 14 days later. The share strengths of the bonded brackets were measured in Newton and Megapascals. In all material groups, the highest share strength values were found in samples sandblasted with Al2O3 particles. For bis-acrylic composite and polymethyl methacrylate groups, the lowest bond strength value were found in samples irradiated with Er,Cr:YSGG laser. The shear bond strengths of the orthodontic brackets bonded to the temporary crown materials produced in CAD/CAM systems vary according to the structure of the material and surface conditioning processes.

Mechanical changes of sandblasted Ti-6al-4v using 100 μm Al2O3 after dynamic pressure treatment: In vitro study

Background: Implant materials have been developed in such a way to fulfill various requirements of mechanical properties, one of the methods to change mechanical properties of implant is the sandblasting method. Purpose: This study aimed to determine the changes in mechanical properties of Titanium 6 Alloy 4 Vanadium (Ti-6Al-4V) sandblasted using 100μm Al2O3 after dynamic stress treatment. Method: 32 Ti-6Al-4V implant samples divided into two groups, 16 samples of treatment group (PI) and 16 samples of control group (PII). The PI group is Ti-6Al-4V sandblasted by Al2O3 100 and the PII group is Ti-6Al-4V machined surface. Both groups of samples were given dynamic treatment as much as 2 million times and then performed a compression test. Results: The results of data analysis showed PII> PI and there was a significant difference (p<0.05) between the PI and PII groups. Conclusion: In conclusion, there's difference in mechanical properties of sandblasted Ti-6Al-4V using 100μm Al2O3 after dynamic pressure treatment.

Mechanical changes of sandblasted Ti-6al-4v using 100 μm Al2O3 after dynamic pressure treatment: In vitro study

Mechanical changes of sandblasted Ti-6al-4v using 100 μm Al2O3 after dynamic pressure treatment: In vitro study

Effect of different surface treatments on resin-matrix CAD/CAM ceramics bonding to dentin: in vitro study

BackgroundEvaluating the effect of different surface treatment methods on the micro-tensile bond strength (µTBS) of two different resin-matrix computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics (RMCs).MethodsA standardized inlay preparations were performed on 100 intact maxillary premolars. According to the type of the restorative material, the teeth were randomly divided into two equally sized groups (n = 50): (polymer-infiltrated ceramic (Vita Enamic) and resin-based composites (Lava Ultimate)). The inlays were fabricated using CAD/CAM technology. In each group, the specimens were randomly assigned to five subgroups (n = 10) according to the surface treatment method: group 1 used was the control group (no surface treatment); group 2, was treated with air abrasion with 50 μm Al2O3 (A) and universal adhesive (UA); group 3, was treated with air abrasion with 50 μm Al2O3 (A) and silane coupling agent (S); group 4, was treated with hydrofluoric acid (HF) and universal adhesive (UA) and group 5, was treated with Hydrofluoric acid (HF) + silane coupling agent (S). The inlays were then cemented to their respective preparations using dual-cure self-adhesive resin cement (RelyX U200, 3 M ESPE) according to the manufacturer’s instructions. The µTBS test was conducted in all groups, and stereomicroscope and scanning electron microscope were used to inspect the failure mode. The data were statistically analyzed using a two-way analysis of variance (ANOVA) and Tukey’s post-hoc multiple comparison tests at a significance level of p < 0.05.ResultsSurface treatments significantly increased the µTBS of the materials compared to the control group (p < 0.05). For CAD/CAM RBCs, the µTBS value highest in group 2 whereas, for PICN, the µTBS value was highest in group 3. Cohesive failure of CAD/CAM restorative material was the most predominant mode of failure in all treated groups, whereas adhesive failure at restoration-cement interface was the most predominant failure mode in the control group.ConclusionSurface treatments increase the µTBS of resin-matrix CAD/CAM ceramics to tooth structure. Air abrasion followed by universal adhesive and hydrofluoric acid followed by silane application appears to be the best strategies for optimizing the bond strength of CAD/CAM RBCs and PICN respectively.

The Reaction Products of the Al-Nb-B2O3-CuO System in an Al 6063 Alloy Melt and Their Influence on the Alloy's Structure and Characteristics.

To meet aero-engine aluminum skirt requirements, an experiment was carried out using Al-Nb-B2O3-CuO as the reaction system and a 6063 aluminum alloy melt as the reaction medium for a contact reaction, and 6063 aluminum matrix composites containing in situ particles were prepared with the near-liquid-phase line-casting method after the reaction was completed. The effects of the reactant molar ratio and the preheating temperature on the in situ reaction process and products were explored in order to determine the influence of in situ-reaction-product features on the organization and the qualities of the composites. Thermodynamic calculations, DSC analysis, and experiments revealed that the reaction could continue when the molar ratio of the reactants of Al-Nb-B2O3-CuO was 6:1:1:1.5. A kinetic study revealed that the Al thermal reaction in the system produced Al2O3 and [B], and the [B] atoms interacted with Nb to generate NbB2. With increasing temperature, the interaction between the Nb and the AlB2 produced hexagonal NbB2 particles with an average longitudinal size of 1 μm and subspherical Al2O3 particles with an average longitudinal size of 0.2 μm. The microstructure of the composites was reasonably fine, with an estimated equiaxed crystal size of around 22 μm, a tensile strength of 170 MPa, a yield strength of 135 MPa, an elongation of 13.4%, and a fracture energy of 17.05 × 105 KJ/m3, with a content of 2.3 wt% complex-phase particles. When compared to the matrix alloy without addition, the NbB2 and Al2O3 particles produced by the in situ reaction had a significant refinement effect on the microstructure of the alloy, and the plasticity of the composite in the as-cast state was improved while maintaining higher strength and better overall mechanical properties, allowing for industrial mass production.

Effect of Surface Treatments of Polyetherketoneketone as a Post Material on Shear Bond Strength to Root Dentin using Two Types of Resin Cement.

This study investigated the effects of mechanical and chemical pretreatment of polyetherketoneketone (PEKK) on shear bond strength (SBS) to root dentin using two types of resin cement. A total of 100 PEKK specimens were prepared and polished. Sixty specimens were mechanically treated by sandblasting (50-µm Al2O3 for 10 s at 0.2-0.25 MPa), and the remaining 40 were untreated. Self-adhesive resin cement and conventional resin cement were used. PEKK specimens bonded to root dentin using self-adhesive resin cement were classified into three groups by pretreatment method: (1) untreated PEKK, (2) mechanical pretreatment (sandblasted PEKK), and (3) both mechanical and chemical pretreatment (PEKK sandblasting as well as application of Scotchbond Universal; 3M Oral Care). Conventional resin cement was pretreated following the same steps (1-3) as those followed for self-adhesive specimens. Each group included 10 specimens. PEKK specimens after surface treatments were examined using SEM. SBS tests were performed using a universal testing machine, and data were statistically analyzed using one-way ANOVA and Tukey's multiple comparison test (p < 0.05). No significant difference was observed between cements with and without sandblasting. However, self-adhesive specimens with both mechanical and chemical pretreatments demonstrated higher SBS than other cements with or without pretreatment. Mechanical pretreatment by sandblasting did not improve the PEKK-root dentin SBS. However, combined mechanical (sandblasting) and chemical pretreatment (ScotchBond Universal) significantly improved the SBS between the PEKK and root dentin.

The effects of HAp coating layer on mechanical and optical properties at bonding interface of high-performance polymers

PurposeThe effect of hydroxyapatite (HAp) coating layer on mechanical and optical properties at bonding interface of high-performance polymers (HPPs) used in computer-aided design (CAD)/computer-aided manufacture (CAM) technology was investigated in this in vitro study. Materials and methodsTwo hundred-twenty specimens were divided into two material groups (n = 110): polyetheretherketone (PEEK, KERA® starPEEK) and polyetherketoneketone (PEKK, Pekkton® ivory). For mechanical testing, each group was divided into five surface pretreatment subgroups and a control group (n = 10): HAp coating (1%,3%, 5%, and 10% concentrations) and sandblasting with 110-μm Al2O3 particles. For optical testing, each group was divided into five subgroups (n = 10): HAp coating (1%, 3%, 5%, and 10% concentrations) and control. The effects of the HAp coating on the optical changes and shear bond strength (SBS) of the specimens were investigated. Data was statistically analyzed by one-way ANOVA and Tukey's post-hoc test. Failure modes and surface properties of the specimens were examined by scanning electron microscopy (SEM) and coupled electron dispersive spectroscopy (EDS). ResultsAverage translucency and color change values increased with increasing HAp coating concentration in HPPs. As a result of the data, statistically significant differences were observed in terms of the effect of the HAp coating on SBS of HPPs (p < 0.05). Failure modes were examined, and mixed failure mode was observed. ConclusionHAp coating can contribute to the improvement of both the optical properties and bond strength of the HPPs to resin composite. Clinical significanceAdhesion and color problems of high performance polymers are still under discussion. In order to solve these problems, generally focused on surface modifications of these polymers, but the effect of the HAp coating has not been investigated.

Effect of 9% Hydrofluoric Acid Gel Hot-Etching Surface Treatment on Shear Bond Strength of Resin Cements to Zirconia Ceramics.

Background and Objectives: There is no consensus regarding the surface treatment method for achieving optimal bonding strength between zirconia and resin cements. We evaluated the effect of hot-etching with 9% hydrofluoric acid (HF) gel using the Zirconia Etchant Cloud System on zirconia surfaces and the consequent shear bond strength (SBS) of different resin cements to such surface-treated zirconia ceramics. Materials and Methods: Forty-five zirconia specimens were randomly assigned to surface-treatment groups (n = 15/group): no treatment (control, CT); sandblasting with 110-μm Al2O3 at an air pressure of 1 bar for 10 s (SB); hot-etching with 9% HF gel (HE). Post-treatment, specimens were examined using scanning electron microscopy (SEM) and surface roughness (SR) analysis. After treatment, self-adhesive resin cements (Maxcem Elite, MAZIC Cem, RelyX U200, 3M ESPE: Maplewood, MN, USA) were bonded to zirconia specimens, which were stored in distilled water at 37 °C for 24 h. All specimens were then subjected to SBS testing, using a universal testing machine, until failure. Data were analyzed using one-way analysis of variance and Tukey’s post hoc test (α = 0.05). Results: In the SEM images, roughness was greater in SB than in HE specimens. Ra and Rt values were highest in SB, followed by HE, and CT specimens. HE specimens showed significantly higher SBS values than CT or SB specimens (p < 0.05). MAZIC Cem cement, with 10-methacryloyloxydcyl dihydrogen phosphate yielded the highest SBS values. Conclusions: Hot-etching with 9% HF gel in a safe shell formed uniformly small, defined holes on the zirconia surface and achieved significantly higher SBS values than sandblasting (p < 0.05). Zirconia prostheses can be bonded micromechanically with resin cement, without the deterioration of properties due to t-m transformation, using chemical acid etching with the Zirconia Etchant Cloud System.

Metal-Seramik Diş Restorasyonlarının Üretiminde Farklı Yüzey İşlemlerinin Makaslama Bağlanma Dayanımına Etkilerinin Araştırılması

Aim: The bond strength between metal and porcelain is an essential factor for the success of metal-ceramic restorations. Therefore, this study evaluated the shear bond strength (SBS) between ceramic and cobalt-chromium (Co-Cr) alloys after oxidation treatment.&#x0D; Material and Methods: A total of 150 Co-Cr samples, 50 samples each, were produced from casting, laser sintering, and milling techniques. The primary group samples produced were divided into five subgroups. One of the subgroups is sandblasted with 110 µm Al2O3, and the others are ground with carbon separator disc, sintered diamond bur, tungsten carbide bur, and pink stone in one direction. SBS test was applied after the oxidation and veneering process. After debonding, digital microscopy investigated the surface characterizations of Co-Cr alloys. For the normality distribution of SBS measurements, the Kolmogorov-Smirnov test was used. According to the results, non-parametric tests were used in the study because the distribution was not suitable for the normal distribution, and the number of samples within the group was low in the subgroups. Kruskal Wallis and All pair-wise post hoc test (α = 0.05) were used for analysis.&#x0D; Results: There was a statistical difference between the laser sintering and milling groups according to the fabrication techniques. The highest SBS value was found in the Al2O3 laser group (34.35) and the lowest in the Al2O3 casting group (17.68). Surface treatments significantly altered ceramic adhesion. Almost all subgroups exhibited mixed failure. All of the SBS values found in this study were almost clinically acceptable.&#x0D; Conclusion: As different abrasives in the leveling and finishing of metal substructures may affect the metal-ceramic bonding, care should be taken in their use as much as possible.

The 3D Printing Behavior of Photocurable Ceramic/Polymer Composite Slurries Prepared with Different Particle Sizes.

Ceramic polymer composite slurries were prepared using nano- and micro-sized Al2O3 in order to analyze rheological properties, sedimentation, and curing behavior. Slurries with different Al2O3 particle sizes were prepared with varying concentrations of photoinitiator, and subjected to different exposure times to prepare a printing object. All slurries exhibit shear-thinning behavior, and the viscosity increases with decreasing Al2O3 particle size. The 100 nm Al2O3 slurry is confirmed to be more sol-like, while the 500 nm and 2 μm Al2O3 slurries have a gel-like structure. As the Al2O3 particle size increases, a thick sedimentation layer forms due to rapid settling, but as the distance between particles increases, the UV light scattering reduces, and the curing rate increases. The exposure time range viable for printing, and the dimension conformity of the printed specimen with the design file, is improved by increasing the Al2O3 particle size. In the case of 500 nm and 2 μm Al2O3 slurries, the maximum heat flow, curing enthalpy, and conversion rate are high with respect to photoinitiator concentration, in the order of 1.0 > 0.1 > 3.0 wt.%. When the photoinitiator concentration exceeds 1 wt.%, it appears to affect the reactivity of the slurry.

Effect of Porcelain-to-Zirconia Ratio and Bonding Strategy on the Biaxial Flexural Strength and Weibull Characteristics of a Stress-Free Bilayer CAD/CAM Ceramic System.

To evaluate the biaxial flexural strength of different porcelain-to-zirconia thickness ratios and bonding strategies of a stress-free bilayer CAD/CAM ceramic system. A total of 60 zirconia discs (diameter: 15 mm; thickness: 0.3 or 0.5 mm; n = 30 for each thickness) were divided into six groups (n = 10 each) according to porcelain-to-zirconia ratio and bonding strategy: VM/Zr (control): zirconia discs veneered with a feldspathic ceramic (VM 9, Vita) in 0.9-mm and 0.7-mm thicknesses using a conventional hand-layering technique; VB/Zr-SBU: zirconia discs airborne particle-abraded with 50-μm Al2O3 particles followed by an MDP primer application (Single Bond Universal, 3M) and bonded to the porcelain with a resin cement (Panavia F 2.0, Kuraray); and VB/Zr-RC: zirconia discs airborne particle-abraded with 30-μm silica-coated Al2O3 particles and silanized and bonded to the porcelain with the same resin cement. Before cementation, the VB (Vitablocs II) discs were etched with 5% hydrofluoric acid (60 seconds), followed by silane application. The bilayers (thickness = 1.2 mm) were loaded with 750 g while light curing the resin cement. Two porcelain-to-zirconia thickness ratios were evaluated: 0.9: 0.3 mm and 0.7: 0.5 mm. All groups were subjected to 106 mechanical cycles, followed by a biaxial flexural test. Data (MPa) were subjected to two-way analysis of variance (ANOVA), Tukey test (5%), and Weibull analyses. Two-way ANOVA revealed that the factor porcelain-to-zirconia ratio (P = .0556) was not significant; however, the bonding strategy factor was statistically significant. Among the 0.5-mm zirconia groups, the VB/Zr-SBU group presented higher flexural strength (s) than the VM/Zr or VB/Zr-RC groups. Similar results were also found for the 0.3-mm zirconia groups, in which the VB/Zr-SBU group also presented higher strength than the others, which were similar in comparison (Tukey). The Weibull modulus was similar among the groups; however, the characteristic strength was significantly different (P = .000). The zirconia bonding strategy with 50-μm Al2O3 airborne-particle abrasion, followed by a primer application, increases the flexural strength of a stress-free bilayer CAD/CAM ceramic system.

Silica deposition on zirconia via Room-Temperature Atomic Layer Deposition and bond strength to resin-based luting agent

To evaluate the effect of the controlled growth of yttria-stabilized zirconia (Y-PSZ) transformed layer and silica deposition via Room-Temperature Atomic Layer Deposition (RT-ALD) on the shear bond strength (SBS) between Y-PSZ and luting agent. Y-PSZ specimens (IPS e.max ZirCAD) with different translucencies (MO, MT, LT) were exposed to surface treatments (n = 10): control (C - no treatment), aged (A - 15 h, 134 °C, 2 bar in autoclave), blasted (B - 50 μm Al2O3), silica deposition via RT-ALD (R - 40 cycles of sequential exposure to tetramethoxysilane orthosilicate and ammonium hydroxide vapors) and aged followed by silica deposition (AR). Specimens were bonded to resin composite cylinders with a luting agent (Multilink Automix) and SBS test was performed. Failure mode and surface chemical and topographical characterization (energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy) were performed. SBS data was analyzed by two-way ANOVA and Tukey test (α = 0.05). Silica deposition resulted in SBS values similar to alumina blasting (p > .848), with no significant effect of aging (p > .664). Higher incidence of composite resin cohesive failures was observed in the R-treated specimens (MT, LT), with and without aging. SEM images showed a rougher surface for B-treated specimens, while no changes were observed for the other treatments. XPS analysis showed a nanofilm of silica deposited over the zirconia surface after silica deposition. RT-ALD was an effective technique to deposit silica on the surface of zirconia, generating bond strength results similar to alumina-blasted specimens.

Adhesion to a new CAD/CAM resin composite: Effects of the machining roughness simulation, surface treatments, and long-term aging

ObjectivesTo evaluate the effect of surface treatments, finishing condition (polished vs. ground) and aging on the microtensile bond strength of a CAD/CAM resin composite to resin cement. Materials and methodsCAD/CAM resin composite blocks (Tetric CAD HT) were sectioned (7 × 12 × 4 mm), randomly divided according to finishing condition (polished or ground) and surface treatment groups (Ctrl: no treatment; AA: air-abrasion with 110 μm Al2O3 powder; TBS: tribochemical silica coating). A coupling agent corresponding to each surface treatment was applied for cementation (Ctrl and AA groups: ExciTE F DSC; TBS group: RelyX Ceramic Primer) and each block was adhesively cemented (Variolink N) with another one from the same conditioning. Next, 1 mm2 cross-section beams were produced after sectioning, with half being tested under microtensile test after 24 h, while the other half was aged (25,000 cycles of thermocycling + 90 days of storage) (n = 50). Contact angle and Scanning Electron Microscopy (SEM) analysis were performed. Bond strength data (MPa) were statistically analyzed using Three-way ANOVA and Tukey tests (α = 0.05). The failure types were examined and classified as predominantly adhesive, cohesive or mixed under stereomicroscopy. ResultsThe surface treatments (AA and TBS) promoted higher bond strength than the Ctrl group. Grinding finishing improved the bond strength only when no treatment was performed (Ctrl group), having a negative effect for the TBS treatment. The long-term aging damaged the resin bond, independent of the condition. The failure analysis showed that 92% of the failures were classified as adhesive in the baseline conditions, and 94.7% in aged specimens. TBS showed the lowest contact angle among the tested groups for both conditions (baseline and aged). ConclusionSurface conditioning with alumina particle air-abrasion or tribochemical silica coating improves the bond strength. CAD/CAM milling roughness induces better surface condition for adhesion, in particular when no treatment is performed. Bond degradation occurs after long-term aging for all the test conditions. Clinical relevanceWhen luting CAD/CAM resin composite restorations, the surface treatment and roughness due to the grinding by burs in the manufacturing process influence the adhesion of restoration to resin cement.

Effect of Different Surface Treatments on the Micro-Shear Bond Strength and Surface Characteristics of Zirconia: An In Vitro Study.

Purpose To study the effect of different surface treatments on the micro-shear bond strength and surface characteristics of zirconia. Methods Two types of zirconia ceramics were tested: opaque (O) and translucent (T). Each type of zirconia was further allotted into four groups based on the type of surface treatment method. The four groups were: control (C), air abrasion with 110 µm Al2O3 particles (A), etching with Zircos–E Etching solution for 2 hours (E), and a combination of air abrasion and etching (AE). After the surface treatment, all specimens were ultrasonically cleaned and 10 resin cement cylinders were attached to the zirconia discs in each group. A micro-shear bond strength test was performed in a universal testing machine at a crosshead speed of 0.5 mm/min. The fracture surfaces were assessed under a compound microscope. SEM, EDAX, and AFM analyses were done for the zirconia specimens after being subjected to surface treatment. Statistical analysis for the bond strength test was done using the Shapiro–Wilk test, one-way analysis of variance (ANOVA), and Post hoc Tukey test. Results The micro-shear bond strength values for the groups were as follows in megapascals (MPa): OC 18.96 (5.54), OA 22.66 (2.51), OE 28.48 (4.50), OAE 28.63 (4.53), TC 22.82 (5.46), TA 25.36 (5.17), TE 28.12 (4.76), and TAE 32.00 (3.47). The one-way analysis of variance (ANOVA) and post hoc Tukey HSD tests were done which showed significant results in the groups. In opaque zirconia, significant differences were seen in the etching and air abrasion with etching groups when compared with the control and air abrasion groups. There was no difference between the etching and air abrasion with etching groups. For translucent zirconia, the only significant difference was seen in the air abrasion with etching group in comparison with the control and air abrasion groups. The mode of failure was majorly adhesive. The surface topography and surface roughness showed significant differences between the groups. The EDAX results showed material loss that occurred due to sandblasting in the air abrasion groups. Conclusions Etching with Zircos–E Etching solution significantly increased the bond strength of zirconia to resin cement when compared with other surface treatment methods. In translucent zirconia, the best results can be achieved by combining etching with air abrasion.

Surface Characteristics and Adhesion of Veneering Composite Resin to PAEK-Based Substructure Restorative Materials.

To evaluate and compare the shear bond strength (SBS) of composite veneering material to polyetherketoneketone (PEKK), polyetheretherketone (PEEK), zirconia (YZ), and nickel-chromium alloy (NiCr) substructure restorative materials. Forty samples (12 × 2 mm) were prepared from four materials: PEKK, PEEK, zirconia, and NiCr alloy (n = 10). The Vickers hardness was evaluated before preparing the surface for bonding by shot-blasting using 110 μm Al2 O3 particles. The surface roughness (Ra) of each sample was determined using a noncontact optical profilometer. The veneering resin was bonded onto each sample following primer application. The prepared samples were then subjected to an SBS test using a universal testing machine at 0.5 mm/min crosshead speed. Failure modes and surface topography following debonding were assessed. The data were statistically analyzed using ANOVA and Tukey'spost-hoccomparison test (p < 0.05). RESULTS: The highest and lowest mean surface roughness was observed in PEEK (3.45 ±0.13 μm) and NiCr (1.87 ±0.07 μm) materials, respectively. A significant difference in roughness values was observed between the materials except for NiCr and YZ (p = 0.547). Concerning SBS, PEEK and NiCr exhibited the highest (16.23 ±0.96 MPa) and lowest (10.1 ±0.63 MPa) values. The mean difference in SBS indicated a statistically significant difference between the material groups (p < 0.01). PEKK materials demonstrated significantly lower SBS than PEEK and significantly higher SBS values than conventional zirconia and alloy materials. A positive and significant correlation between mean roughness and SBS was observed, but the causality could be either intrinsic to the material or the roughness.

Effect of femtosecond laser and sllica-coating on zirconia framework-veneering ceramic bonding, surface chemistry and crystallographic changes

The aim of this study was the assessment of various surface conditioning methods upon zirconia framework veneering ceramic bonding, crystallographic changes, and surface chemistry. 91 prepared zirconia specimens were randomly assigned to 4 groups (n = 18) according to conditioning method: Group SB: Air-borne-particle abrasion with 50 µm Al2O3; Group R: Tribochemical silica coating; Group FL: Femtosecond-laser application; Group Si25: argon/oxygen plasma (8:1 in flux) film deposition on the zirconia surface for 25 min and Group Si49: as in Si25 but only 49 min. The veneering ceramic was fired upon the zirconia surface and the interface of the framework-veneer assemblies were subjected to shear force using a Universal Testing Machine (1 mm/min). Three specimens from every group were analyzed with profilometry and SEM. Data were statistically analyzed using a One-way ANOVA and Tukey’s test for multiple comparisons (α = 0.05). Failure modes were obtained and SEM-EDX was used to identify tetragonal to monoclinic transformation phase change. Group Si49 (32 ± 3) presented the highest mean bond strength values (MPa) followed by Group Si25 (28 ± 6) being not significant from one another (p > 0.05). Groups SB (15 ± 5) and R (16 ± 5) did not show significant difference (p > 0.05), being significantly less than that of Group FL (22 ± 6) (p < 0.05). All groups presented predominantly mixed failures. Silica-based coating was most effective in terms of bond strength, minimal flaws and transformation in the zirconia tested.

Effect of Er,Cr: YSGG Laser on Bonding of Laminate Veneers using CAD/CAM (In Vitro Study)

AIM: This in vitro study was designed to evaluate the shear bond strength after bonding between porcelain laminate veneers and the tooth surface using different etching methods METHODS: Thirty freshly extracted maxillary premolars were used and prepared for receiving Enamic laminate veneers. Specimens were divided into two groups (n = 15), according to the surface treatment protocol. The specimens were sandblasted with 50 μm Al2O3 for 20 s; 2 bar pressure was maintained for air abrasion. Distribution of groups was as follow G1: Prepared enamel surface treatment of each tooth was according to the manufacturer’s instructions. G2: The prepared enamel surface of each tooth was subjected to Erbium,Chromium-Doped: Yttrium, Scandium, Gallium, and Garnet laser application. Light cured adhesive resin cement was applied to fitting surface of each ceramic specimen. To simulate thermal aging, the samples were subjected to 5000 thermal cycling in a thermocycler. By dividing the failure load (N) by the bonding area (mm2), debonding loads were calculated as shear stress (MPa). Numerical data were presented as mean and standard deviation values. They were explored for normality by checking the data distribution using Shapiro–Wilk test. Data showed parametric distribution and were analyzed using independent t-test. The significance level was set at p ≤ 0.05 within all tests. Statistical analysis was performed with R statistical analysis software version 4.1.2 for Windows. RESULTS: Group (II) (15.84 ± 3.09) had significantly higher mean value than group (I) (13.69 ± 2.36) (t = 2.15, p = 0.041). CONCLUSION: Within the limitation of this study, it was revealed that the laser surface treatment for tooth substrate plays a significant role in increasing the shear bond strength of laminate veneers.