Ali Özer

Investigations on the effects of mouthrinses on the colour stability and surface roughness of different dental bioceramics

PURPOSE In this study, three bioceramic materials, [IPS Empress CAD (Ivoclar), IPS e.max CAD (Ivoclar), and Lava Ultimate CAD (3M ESPE)] were treated with three commercial mouthrinses [Listerine, Tantum Verde, and Klorhex]; and changes in colour reflectance and surface roughness values were then quantitatively assessed. MATERIALS AND METHODS One hundred and twenty ceramic samples, with dimensions of 2 × 12 × 14 mm, were prepared and divided into nine sample groups, except three control samples. The samples were immersed in the mouthrinse solutions for 120 hrs, and changes in colour reflectance and surface roughness values were measured by UV light spectrophotometry (Vita Easyshade; VITA Zahnfabrik) and by profilometer device (MitutoyoSurftest SJ-301), respectively. The change of surface roughness was inspected by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). RESULTS There was a positive correlation between the ΔE and increase in the surface roughness. Two of the ceramic materials, IPS Empress and Lava Ultimate, were affected significantly by the treatment of the mouthrinse solutions (P<.05). The most affecting solution was Tantum Verde and the most affected material was Lava Ultimate. As expected, the most resistant material to ΔE and chemical corrosion was IPS e max CAD among the materials used. CONCLUSION This work implied that mouthrinse with lower alcohol content had less deteriorating effect on colour and on the surface morphology of the bioceramic materials.

Synthesis and Characterization of CeO 2 Doped ZrO 2 Ceramics by a Simple Sol-Gel Route

It is well known that sol-gel technique is a simple method to produce nano sized ceramic powders. In this study, cerium oxide doped zirconia samples, with 10 mol%-12mol% and14mol% CeO2, were synthesized by sol-gel technique and characterized. The surface morphology, elemental composition, microstructure, and phase analysis, of the sintered CeO2 doped ZrO2 ceramics were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDS) analysis, and X-ray diffraction (XRD) respectively. X-ray diffraction for samples sintered at 1550 °C for 4h revealed that the zirconia ceramics have a tetragonal phase structure. The addition of CeO2 can raise the content of the tetragonal phase, but the minor monoclinic phase exists even at the CeO2 content of 10 mol%. The effect of dopant concentration on the lattice parameter, average primary crystallite size and micro-strain was studied. Relative densities for CeO2 doped ZrO2 bulk ceramics varied between 95% and 99 %, depending on the CeO2 addition.

Formation of Al-Ti-B Phases for Grain Refinement of Al Alloys Produced by High Energy Ball Milling

In this experimental study, Al-Ti-B powders were ground in planetary ball mill to produce AlxTiyBz where x, y and z stands for the relative molar ratios of elements for the compilation of grain refiner compound. Powder size distribution, phase formation (XRD) and particle morphology was investigated by means of SEM and XRD. The fabrication of AlTiB phases and the grain refinement of Al alloys by adding this phase were aimed. For this purpose, the powders were fed to planetary ball mill to be milled at a speed of 600 rpm. The powders were also milled at different milling times as 30 min and 150 min either in metallic form or compound form of Al, Ti and B powders. The powders were dried after each milling to be characterized by SEM and XRD. The phases and morphology-elemental analysis were also conducted by XRD and SEM, respectively. Moreover, the powders were added to Al alloy castings avoiding the breaking through alloy series which are mainly used in aluminum industry. The Al alloy series were examined for grain refinement by Brinell hardness and optical microscopy for mechanical properties and grain formation as well as by SEM (EDS) for grain formation, morphology and elemental distribution analysis.

Effect of Yttria on the Phase Formation and Sintering of HA-Al2O3 Biocomposites

Hydroxyapatite is very-well known as the main component of hard tissues and, as such, it has attracted much attention by researchers in the recent decades. This study was aimed to present the characterization of Y2O3 doped 50 wt.% hydroxyapatite – 50 wt.% Al2O3 composite materials fabricated at relatively high temperature of 1600 ◦C. Hydroxyapatite powder was obtained from bovine bones via calcination and ball milling technique. Fine powders (≤ 1 μm) of hydroxyapatite/Al2O3 were admixed with 0.5 and 1 wt.% Y2O3 powders. Powder compacts were sintered at 1600 ◦C for 4 h in air atmosphere. The field emission scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction studies following the relative density measurements were conducted. Moreover, the microhardness was studied as the mechanical property of sintered samples. The effect of increasing Y2O3 content on surface morphology, elemental distribution and phase evaluation was investigated in hydroxyapatite/Al2O3 biocomposite materials. It was found that by increasing Y2O3 content, the relative density increased up to 98.8%, while the hardness increased to 863 HV(0.2). The main phases, which were found, are Hibonite – CaO(Al2O3)6 and beta-tricalcium phosphate – Ca3(PO4)2, according to X-ray diffraction pattern.

Investigation on the machinability of steel/steel laminates by CO2 laser

In this study, an experimental investigation of machinability of steel/steel laminates using CO2 laser was presented. O2 assist gas was used for cutting of laminates. Laser power and feed rate were changed gradually as cutting parameters. Heat affected zone (HAZ) size and kerf width were measured. Effect of linear energy density (ratio of power to feed rate) was determined on the kerf width, the HAZ size, and the cutting surface quality. Also, the quality of surface was examined under optical microscopy, and scanning electron microscopy. It is concluded that when linear energy density is increased, the kerf width and the HAZ size increase. Dross formation and surface irregularities increase with increasing laser power and decreasing feed rate.

Farklı Akışkan Bulk Fill Kompozitlerin Mikrosertliklerinin Araştırılması

Objectives: This study was examined thesurface microhardness of three kind of bulk fillcomposites Surefil SDR flow, Tetric, EvoCeram,X-tra base)Materials and Methods: Ten specimens of2mm, 4mm thickness and 4mm diameter of eachbulk fill composite were polymerized using ahalogen light and a blue light-emitted diode.Microhardness evaluation was performed at the topand bottom surfaces for each specimen using aVickers microhardness tester.Results: All of the materials were cured withthe light sources and the values obtained for thebottom surfaces were found to be lower than thevalues of top surfaces. Highest microhardness level(40.02±4.06)among all composite materialsbelonged to Xtra base composite group, whereaslowest microhardness level (5.80±0.83) was ofSDR composite specimens.Conclusions: Hardness ratio range was between0.19±0.3 and 0.72±0.06. Hardness ratio value wasfound to be lower than 0.80 for all compositegroups.

Effect of Polymorphic Zirconia Phases on the Mechanical and Wear Properties of Cr3C2-NiCr Cermets

Cr3C2-NiCr type cermets are used in cutting technology for their low sintering temperatures and relatively low densities. Their high corrosion resistance at high cutting speeds and high temperatures increases the interest to these materials. In this study, a powder mixture of 75wt% Cr3C2 and 25wt% NiCr with a Ni-Cr ratio of 4/1 by weight was sintered at 1350°C as the master composite. 3 mol % Y2O3 stabilized tetragonal ZrO2 and 8 mol % Y2O3 stabilized cubic ZrO2 powders were added to study the effect of ZrO2 content on the mechanical and wear properties of Cr3C2-NiCr cermets at the same sintering temperature. SEM and EDX analysis were performed for identifying microstructures. Elastic modulus and microhardness of master and doped cermets were measured by impulse excitation technique and Vickers (HV10), respectively. Wear tests were conducted by ball on reciprocating flat method to characterize the wear properties.