Effect of Heat Treatment on Structural and Mechanical Properties of Alloyed Fused Alumina

Heat treatment of ceramic-bond grinding tools during manufacture takes place at temperature of abrasive grains up to 1250 °C, which results in variation of their phase composition, structure, and strength. Similar phenomena may take place during grinding caused by the occurring high-temperature processes. It primarily pertains to alloyed fused alumina. X-ray and topography testing, as well as studying of micromechanical properties made it clear that structural performance, material strength, and fracture pattern of single grains of Ti-containing fused alumina affected by temperature depend on the type and ratio of alloy additives in alumina and on the decomposition level of the Ti2O3 solid solution. In terms of aggregate properties, purple varieties of Cr-Ti fused alumina featuring the minimum TiO2/Cr2O3 ratio of 1.5 in the solid solution after heat treatment are preferable.

Surface Treatment Effect on Shear Bond Strength between Lithium Disilicate Glass-Ceramic and Resin Cement

Objective The study aimed to evaluate the shear bond strength (SBS) of lithium disilicate glass-ceramic (LDGC) and resin cement (RC) using different surface treatments. Materials and Methods LDGC blocks (Vintage LD Press) were prepared, etched with 4.5% hydrofluoric acid, and randomly divided into seven groups (n = 10), depending on the surface treatments. The groups were divided as follows: 1) no surface treatment (control), 2) Silane Primer (KS), 3) Signum Ceramic Bond I (SGI), 4) Signum Ceramic Bond I/Signum Ceramic Bond II (SGI/SGII), 5) experimental silane (EXP), 6) experimental silane/Signum Ceramic Bond II (EXP/SGII), and 7) Experimental/Adper Scotchbond Multi-purpose Adhesive (EXP/ADP). The specimens were cemented to resin composite blocks with resin cement and stored in water at 37 °C for 24 hours. The specimens underwent 5,000 thermal cycles and were subjected to the SBS test. Mode of failure was evaluated under the stereo microscope. Statistical Analysis Data were analyzed with Welch ANOVA and Games-Howell post hoc tests (α = 0.05). Results The highest mean SBS showed in group EXP/ADP (45.49 ± 3.37 MPa); however, this was not significantly different from group EXP/SGII (41.38 ± 2.17 MPa) (p ≥ 0.05). The lowest SBS was shown in the control group (18.36 ± 0.69 MPa). This was not significantly different from group KS (20.17 ± 1.10 MPa) (p ≥ 0.05). Conclusions The different surface treatments significantly affected the SBS value between LDGC and RC. The application of pure silane coupling agent with or without the application of an adhesive improved the SBS value and bond quality.

Impregnation of the surface of niobium alloy when grinding with corundum and silicon carbide wheels

The features of the formation of a relief after grinding a niobium alloy with abrasive tools made of corundum and silicon carbide on a ceramic bond are considered. The treated surface is studied with a scanning two-beam electron microscope. Keywords: niobium, grinding, corundum, silicon carbide, material transfer, impregnation, micro-X-ray pattern. [email protected]

Automation of calculations of cutting modes taking into account the wear of cubic boron nitride tools when applying solid lubricants

The effect of a solid lubricant on the wear of cubic boron nitride grinding wheels on a ceramic bond of different hardness and grain size in the processing of high-speed steel is investigated. The dependences of the change in the wear of cubic boron nitride on the parameters of the processing mode are determined. An automated calculation system is proposed to control the consumption of cubic boron nitride grinding wheels in production conditions. Keywords: solid lubricant, grinding, high speed steel, cubic boron nitride grinding wheel, consumption, wear, grinding mode. [email protected]

Effects of accelerated aging cycles on resin cement-glass ceramic bond strength

Aim: A successful restoration is the result of the proper adhesion between dental tissue, cement and restoration material. The long-term durability of this bond is mandatory for clinical success. The aim of the present study is to investigate the influences of three different thermal cycle applications on resin cement-glass ceramic shear bond strength. Methodology: In the present study, a single CAD/CAM glass ceramic block and five different resin cements (Panavia V5, RelyX U200, G-CEM LinkForce, RelyX Veneer,and Variolink Esthetic) were used. A total of 240 sections 2 mm in thickness were obtained under water cooling in a precision cutting machine with the aid of a diamond saw. Cementation of glass ceramic samples was conducted in accordance with the instructions of the manufacturer, and the cemented samples were incubated at 37 °C for 24 hours. Afterwards, samples were randomly divided into four groups according to thermal cycle: control group, 1750, 3500 and 7000 cycles (n = 12). Following aging procedures, the samples were tested for shear bond. Statistical analyses were done by using the IBM SPSS 20.0 program. While the ANOVA test was used for intra-group statistical analyses, LSD multi-comparison analysis was used for detection of the inter-group differences. Statistical significance was set at p < 0.05. Results: Although an overall reduction was seen in shear bond of all cement groups following thermal cycle applications, this reduction was found to be statistically significant for Panavia V5, RelyX Veneer and Variolink Esthetic (p<0.05). Following 1750 cycles of thermal cycle application, Panavia V5 and G-Cem LinkForce with dual-cure property showed higher shear bond strength than RelyX Veneer and Variolink Esthetic with light-cure structure (p<0.05). Conclusion: The reduction in bond strength following the thermal cycle procedure is associated with water absorption in the resin cement-glass ceramic interface. So resin cement preferred for cementation of restorations is among the key parameters for clinical success. How to cite this article: Eskitaşçıoğlu M, Bozbay R, Ünalan Değirmenci B. Effects of accelerated aging cycles on resin cement-glass ceramic bond strength. Int Dent Res 2021;11(2):121-8. https://doi.org/10.5577/intdentres.2021.vol11.no2.10 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Mathematical Modeling of Process Optimization in Profiling Grinding Wheels via Laser

In this work, the experimental research was carried out on the processing of the cutting surface of a grinding wheel with a ceramic bond via continuous laser radiation with a wavelength of 10.6 μm. The influence of laser radiation power, processing speed on the depth and width of the obtained cut was investigated. A full factorial experiment was carried out with varying factors at two levels. In the form of a regression equation, a mathematical model of the effect of radiation power and processing speed on the output parameters of the process is obtained. Using Fisher's criterion, it is shown that the resulting equation adequately describes the process under the study. The analysis of the regression equation makes it possible to assess the relative influence of each factor and the effects of the interaction of factors on the depth and width of the cut on the surfaces of the grinding wheel.

Silane Heat Treatment Could Eliminate the Hydrofluoric Acid Etching of Lithium Disilicate Overlays: A Four-Year Follow-Up

A four-year follow-up of a novel silane heat treatment method for bonding lithium disilicate overlays to tooth structures without hydrofluoric acid etching of the ceramic surface is presented in this case report. Silane heat treatment modifies the silane layer and thus enhances resin ceramic bond strength without hydrofluoric acid etching. The standard ceramic preparation technique prior to bonding silicate ceramics to tooth structure is hydrofluoric acid etching and applying a silane coupling agent, followed by dental adhesive. In this case, the micromechanical roughening of the ceramic surface was performed by air abrasion with Al2O3. Silane heat treatment with constant 120°C airflow, applied for 60 sec, followed by dental adhesive application enhanced the resin-ceramic bond strength. After a four-year follow-up, the restorations’ clinical appearance could be defined as excellent/very good according to the FDI clinical criteria for the evaluation of direct and indirect restorations. This clinical result supports many in vitro studies regarding the resin-ceramic bond strength and durability obtained through postsilanization heat treatment.

Transfer of Abrasive Material at Grinding a Titanium Alloy with a Wheel of Cubic Boron Nitride

The article summarizes the results of the of the titanium alloy surface morphology and chemical composition study after grinding with a wheel of cubic boron nitride on a ceramic bond. The titanium alloy was treated using the method of cut-in grinding in the finishing mode using a synthetic water-soluble lubricant-cooling liquid that does not contain mineral oil. The research was carried out using the FEI Versa 3D LoVac electron microscope. Digital photos of the titanium alloy surface at different magnifications are given. Individual objects’ morphology allows us to identify them as wear products of abrasive tools. The chemical composition of the selected objects was studied by local x-ray spectral analysis. CBN crystals are partially or completely pressed into the treated surface and covered with a layer of the treated material. On the surface of CBN crystals, there are chemical elements that are part of the abrasive tool bond.

Study of Metal, Silicon Carbide Crystals and Ceramic Bond Transfer to the Surface of Titanium Alloy during Grinding

The high adhesive activity of titanium alloys in interaction with abrasive materials is the main cause of poor grinding treatment. The most common abrasive material for grinding titanium alloys is silicon carbide. Silicon carbide wheels operate primarily in self-sharpening mode. Wear of the abrasive tool in the self-sharpening mode occurs as a result of brittle destruction of the fret. The purpose of the study was to determine experimentally the crystalline wear products of an abrasive tool, made of silicon carbide, on the treated surface during grinding of a titanium alloy. Samples of VT9 titanium alloy were processed by flat mortise grinding by a wheel of silicon carbide with the use of VOLTES coolant and the characteristic of the abrasive tool - 64CF80L7V. The treated surface was examined on the electron microscope Versa 3D Dual Beam. The condition of the treated surface testifies to the intensive adhesive interaction of the titanium alloy with the abrasive tool. The thickness of the metal deposits reaches 3 microns. As a result of morphological analysis, objects are identified on the treated surface, the appearance of which allows us to attribute them to crystals. The chemical composition of the selected objects was determined by a microprobe analysis in a microscope camera. On the basis of the conducted researches, a presence on the grinded surface of silicon carbide crystals of various sizes and a ceramic ligament is established.

ENSURING HIGH UNIFORM HARDNESS OF CERAMIC-BOND GRINDING WHEELS

The hardness of the abrasive tool material can be increased as follows: use of fine-grained fillers in abrasive masses in addition to the main fractions. Additional grinding of this bond slightly decreases its grain size, approximately down to 32 - 36 µm, and, above all, ensures higher uniformity. The additional introduction of the borosilicate glass based on fused alumina to the extent up to 15 % of the bond weight is of use. An optimum solution is the simultaneous application of the described ways to increase the hardness.