Gultekin Goller

Sintering effects on mechanical properties of biologically derived dentine hydroxyapatite

In this study, the change in the mechanical properties of hydroxyapatite (HA), which is the main mineral content of bone and teeth, commonly used as an implant material, is tested for different sintering temperatures. Although HA shows great biocompatibility with the human body, its applications are limited to non-load-bearing areas and coatings due to its low mechanical properties. These mechanical properties can be improved substantially by sintering. In this study, naturally produced HA from human teeth is sintered, and density, microhardness measurements and compression tests are performed in order to find the optimum sintering temperature. The results are compared with the synthetically derived HA properties from the literature.

The effect of bond coat on mechanical properties of plasma sprayed bioglass-titanium coatings

Abstract Bioglass, known as 45S5 (45% SiO 2 , 6% P 2 O 5 , 24.5% CaO and 24.5% Na 2 O all in weight percent), was plasma sprayed onto a titanium substrate with and without Amdry 6250 (60% Al 2 O 3 40% TiO 2 ) as bond coating layer. Mechanical properties were evaluated in accordance with the ASTM C633 method and scanning electron microscopy was used for the microstructural characterization. Results indicated that it is possible to coat bioglass on titanium substrate by utilizing similar conditions used for hydroxyapatite. Application of bond coat layer in the plasma spraying of (45S5) bioglass on titanium substrate has increased the bonding strength about three times. The adhesive bonding observed at the bioglass metal interface turned into cohesive bonding by application of the bond coating layer. It has been observed that there is a uniform coating layer with a thickness of 110 and 80 μm depending on coating type with a little amount of porosity.

Shear bond strength of resin luting cement to glass-infiltrated porous aluminum oxide cores

STATEMENT OF PROBLEM Resin bonding surface treatment methods for conventional silica-based dental ceramics are not reliable for glass infiltrated high alumina content In-Ceram ceramics. PURPOSE This study developed an alternative surface treatment to improve resin bonding of glass-infiltrated aluminum oxide ceramic blasting with diamond particles and then observed the efficiency of this treatment. Material and methods. In-Ceram test specimens were prepared and divided into 2 groups. All specimens were sandblasted with Al(2)O(3), and blasted with diamond particles and 2 adhesive resins were applied. After bonding and storage in humid conditions, shear bond strength values were measured with a universal testing machine. Surface roughness and fracture interfaces were determined with a perthometer and a SEM. RESULTS The highest bond strength was obtained on the samples blasted with diamond particles (group II). The differences between the 2 groups and the 2 adhesive resin cements were both statistically significant. CONCLUSION Panavia-Ex cement exhibited higher bond strength than Super-Bond cement. This higher bond strength was attributed to ceramic oxide and ester bond and the mechanical properties of Panavia-Ex cement.

Effect of Al2O3 additions on the acid durability of a Li2O–ZnO–SiO2 glass and its glass-ceramic

Abstract The effect of Al2O3 substitution on the acid durability of a Li2O–ZnO–SiO2 glass and its glass-ceramic was investigated depending on the applied heat treatments, the type and concentrations of acid solutions, and leaching time. Satisfactory acid durability was obtained by using 6 wt.% Al2O3 for the glass and 11 wt.% for the glass-ceramic. The acid resistance of both glasses and glass-ceramics was found to be affected markedly by the presence of P2O5 or TiO2 used as nucleating agent.

Evaluation of air-particle abrasion of Y-TZP with different particles using microstructural analysis

BACKGROUND This study evaluated the effect of air-particle abrasion with different particle sizes on the surface roughness and phase transformation of yttria-stabilized tetragonal zirconia ceramics (Y-TZP). METHODS Eighty-four Y-TZP discs of 15 mm diameter and 1.0 mm thickness were fabricated. The samples were divided into four groups (n = 21): (1) air-particle abrasion with 30 μm CoJet sand blast coating agent (CoJet, 3M ESPE); (2) 50 μm Al2O3 particles; (3) 110 μm Al2O3 particles; and (4) 250 μm Al2O3 particles. Each group was further divided into three subgroups each (n = 7) and treated for 5 seconds, 15 seconds and 30 seconds. Mean surface roughness was determined using a profilometer. The surfaces were analysed with a scanning electron microscope. XRD analysis was employed and the relative amount of the monoclinic phase was calculated. The results were statistically analysed by two-way analysis of variance (ANOVA, p < 0.05). RESULTS Air-particle abrasion with 250 μm Al2O3 particles for 30 seconds had the highest surface roughness (p < 0.001) and a significantly higher amount of monoclinic phase compared to air-particle abrasion with 30 μm, 50 μm and 110 μm particles (p < 0.001). CONCLUSIONS Duration and particle size of air-particle abrasion affects the roughness and phase transformation of Y-TZP. Longer treatment times with larger particles may result in degradation of material.

Influence of zirconia base and shade difference on polymerization efficiency of dual-cure resin cement.

PURPOSE The aim of this study was to investigate the polymerization efficiency of dual-cured resin cement beneath different shades of zirconia-based feldsphathic ceramic restorations. MATERIALS AND METHODS Five translucent zirconia (Zirkonzahn) discs (4.0-mm diameter, 1.2-mm height) were prepared. Feldsphathic ceramic (1.2 mm) (Noritake Cerabien Zr) in 5 shades (1M2, 2M2, 3M2, 4M2, 5M2) was applied on the zirconia discs. Twelve dual-cure resin cement specimens were prepared for each shade, using Panavia F 2.0 (Kuraray) in Teflon molds (4.0-mm diameter, 6.0-mm height), following the manufacturers instructions. Light activation was performed through the zirconia-based ceramic discs for 20 seconds, using a quartz tungsten halogen curing device (Hilux 200) with irradiance of 600 mW/cm(2) . Immediately following light curing, specimens were stored for 24 hours in dry, light-proof containers. Vickers hardness measurements were conducted using a microhardness tester with a 50-g load applied for 15 seconds. The indentations were made in the cross sectional area at four depths, and the mean values were recorded as Vickers hardness number (VHN). Results were statistically analyzed with one-way ANOVA and Tukey HSD test (p < 0.05). RESULTS A statistically significant decrease in VHN of the resin cement was noted with increasing depth and darkness of the shade (p < 0.05). CONCLUSION Curing efficiency of dual-cure resin cement is mainly influenced by the lightness of the shades selected.

Biocompatibility Evaluation of Three Different Titanium-Hydroxyapatite Composites

Titanium reinforced with hydroxyapatite (TiHA) prepared using 15% of titanium and 3 different sinterizing temperatures 1100, 1200 and 1300 oC showed a significant increase in cell proliferation, when compared to the control.

Sintering of Synthetic Hydroxyapatite Compacts

Hydroxyapatite (HA) is a particularly attractive material for bone and tooth implants because of its chemical and crystallographic properties, which closely resemble those of bone and tooth minerals. Moreover, sintered HA material has superior biocompatibility. In this study, the compacts made of pure HA (Merck) were sintered at 1000, 1100, 1200 and 1300°C. The density, microhardness and compression strength tests were performed, in order to find out the optimum sintering temperature. As a result, average density was 2.554± 0.37 g/cm, average compression strength value was 25.22 ± 12 MPa and average value of Vickers microhardness was found as 250 ± 120 HV (kg/mm).

The Improvement of Titanium Reinforced Hydroxyapatite for Biomedical Applications

Abstract The addition of different amounts of inclusions to brittle hydroxya patite (HA) gives the advantage of tailoring and predicting the possible mechanical proper ties of the biocomposite. Biocomposite materials have been developed in order to combine the propert ies of bioactive material with the better mechanical properties of a second phase. Titanium, having superior biocompatibility, mechanical properties and corrosion resistance, is suitable as a reinforcement phase for biomedical applications. This study focuses on the effect s of sintering temperature and the amount of reinforcement phase on the mechanical properties of HA-Ti composites. The HA material used was derived from freshly-extracted human teeth wi th calcination at 850°C. Titanium powders were mixed by 5 and 10 wt % with HA and have been subjected to sintering at 1200 and 1300C for three hours. Density, microhardness, and compressive strength m easurements have been carried out. Microstructures have been investigated by SEM and the phas an lysis has been determined by the x-ray diffraction analysis . The best mechanical properties have been obtained by sintering at 1300°C for three hours with the addition of 10 wt % Ti to HA.

The Influence of Sintering Temperature on Mechanical and Microstructural Properties of Bovine Hydroxyapatite

The influence of sintering temperature on densification, microstructure and the mechanical properties of bovine hydroxyapatite (BHA), produced by a calcination method, was investigated. Densification and mechanical properties increased over increasing sintering temperature in the range between 1000°C and 1300°C, and there are evidences of optimum sintering temperature at 1200°C. The measured mechanical properties indicate sintered BHA-bodies as interesting biomaterials for further investigation in biomedical applications.