Browsing by Subject "Ceramics"
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Item Evaluation of silicosis in ceramic workers; [Seramik fabrikasi işçilerinde silikozis.](2005) Sakar A.; Kaya E.; Celik P.; Gencer N.; Temel O.; Yaman N.; Sepit L.; Yildirim C.A.; Dagyildizi L.; Coşkun E.; Dinç G.; Yorgancioglu A.; Cimrin A.H.This study is aimed to evaluate the incidence of silicosis and the relation of it with personal and work-related factors among workers exposed to silica in ceramic factory. Workers were evaluated by respiratory symptoms, physical examination, pulmonary function and radiological findings. Occupational and Enviromental Pulmonary Disease Evaluation Questionnaire of the Turkish Thoracic Society Enviromental and Occupational Pulmonary Diseases Working Group was used. 365 of 626 workers had exposure to silica and the rest 261 were concerned as control group. There was no difference between mean age, duration of work and smoking pack year among the groups (p> 0.05). Cough and sputum rates were higher in silicosis group FEV1 and FVC values were lower in silica group but this was not statistically significant. When the two subgroups of silica group (the workers in high dust concentration and the ones in low concentration) were compared, the high concentrated group had significantly more sputum but the other symptoms and pulmonary functional parameters were not different significantly. 24 workers had parenchymal densities adjusted with pneumoconiosis. The workers with the pneumoconistic finding, had a higher mean age and longer duration of work. As a conclusion, ceramic industry has risk for silicosis. And the risk increase by time and age.Item Microshear bond strength and finite element analysis of resin composite adhesion to press-on-metal ceramic for repair actions after various conditioning methods(Quintessence Publishing Co., Ltd, 2014) Kanat B.; çömlekoğlu M.E.; çömlekoğlu M.D.; çulha O.; özcan M.; Güngör M.A.Purpose: This study evaluated the repair bond strength of differently surface-conditioned press-on-metal ceramic to repair composites and determined the location of the accumulated stresses by finite element analysis. Materials and Methods: Press-on-metal ceramic disks (IPS InLine PoM, Ivoclar Vivadent) (N = 45, diameter: 3 mm, height: 2 mm) were randomly divided into 3 groups (n = 15 per group) and conditioned with one of the following methods: 9.5% hydrofluoric acid (HF) (Porcelain etch), tribochemical silica coating (TS) (CoJet), and an unconditioned group acted as the control (C). Each group was divided into three subgroups depending on the repair composite resins: a) Arabesk Top (V, a microhybrid; VOCO), b) Filtek Z250 (F, a hybrid;3M ESPE); c) Tetric Evo- Ceram (T, a nanohybrid; Ivoclar Vivadent) (n = 5 per subgroup). Repair composites disks (diameter: 1 mm, height: 1 mm) were photopolymerized on each ceramic block. Microshear bond strength (MSB) tests were performed (1 mm/min) and the obtained data were statistically analyzed using 2-way ANOVA and Tukey's post-hoc test (α = 0.05). Failure types were analyzed under SEM. Vickers indentation hardness, Young's modulus, and finite element analysis (FEA) were performed complementary to MSB tests to determine stress accumulation areas. Results: MSB results were significantly affected by the surface conditioning methods (p = 0.0001), whereas the repair composite types did not show a significant effect (p = 0.108). The interaction terms between the repair composite and surface conditioning method were also statistically significant (p = 0.0001). The lowest MSB values (MPa ± SD) were obtained in the control group (V = 4 ± 0.8; F = 3.9 ± 0.7; T = 4.1 ± 0.7) (p < 0.05). While the group treated with T composite resulted in significantly lower MSB values for the HF group (T= 4.1 ± 0.8) compared to those of other composites (V = 8.1 ± 2.6; F = 7.6 ± 2.2) (p < 0.05), there were no significant differences when TS was used as a conditioning method (V = 5 ± 1.7; F = 4.7 ± 1; T = 6.2 ± 0.8) (p > 0.05). The control group presented exclusively adhesive failures. Cohesive failures in composite followed by mixed failure types were more common in HF and TS conditioned groups. Elasticity modulus of the composites were 22.9, 12.09, and 10.41 GPa for F, T, and V, respectively. Vickers hardness of the composites were 223, 232, and 375 HV for V, T, and F, respectively. Von Mises stresses in the FEA analysis for the V and T composites spread over a large area due to the low elastic modulus of the composite, whereas the F composite material accumulated more stresses at the bonded interface. Conclusion: Press-on-metal ceramic could best be repaired using tribochemical silica coating followed by silanization, regardless of the repair composite type in combination with their corresponding adhesive resins, providing that no cohesive ceramic failure was observed. © Quintessenz. All right reserved.Item Spray drying of hydroxyapatite powders: The effect of spray drying parameters and heat treatment on the particle size and morphology(Elsevier Ltd, 2017) Bastan F.E.; Erdogan G.; Moskalewicz T.; Ustel F.The physical and chemical properties of spray dried hydroxyapatite (SD-HA) are significantly depended on precipitation and spray drying (SD) process parameters. This study presents the effects of precipitation pH, solid content, slurry feed rate, atomization pressure, hot air temperature and hot air flow rate on the particle size distribution of SD-HA. Moreover, the physical and chemical properties of SD-HAs and heat treated micro-granules depending on the precipitation pH were investigated. Taguchi Experimental Design (DoE) was employed to optimize the parameters and to determine the significant factors. The physical properties of SD-HA and heat treated micro-granules were analyzed via particle size analyzer, SEM and TEM. RAMAN and FTIR were carried out to examine the chemical properties. Increasing of the precipitation pH led to slightly increase of the median particle size and the high temperature stability of the SD-HA. DoE results demonstrated the most significant SD parameters as atomization pressure and slurry feed rate. The increases in heat treatment temperature decreased the specific surface area, pore volume and particle size of SD-HA, while increased the crystallinity and powder density. SD-HA were stable up to 1250 °C and decomposed at approximately 1450 °C. © 2017 Elsevier B.V.Item Biological Response of Osteoblastic and Chondrogenic Cells to Graphene-Containing PCL/Bioactive Glass Bilayered Scaffolds for Osteochondral Tissue Engineering Applications(Humana Press Inc., 2018) Deliormanlı A.M.; Atmaca H.Graphene-containing 13-93 bioactive glass and poly(ε-caprolactone)-based bilayer, electrically conductive scaffolds were prepared for osteochondral tissue repair. Biological response of osteoblastic MC3T3-E1 and chondrogenic ATDC5 cells to the composite scaffolds was assessed under mono-culture and co-culture conditions. Cytotoxicity was investigated using MTT assay, cartilage matrix production was evaluated by Alcian blue staining, and mineralization of both types of cells in the different culture systems was observed by Alizarin red S staining. Results showed that osteoblastic and chondrogenic cells utilized in the study did not show toxic response to the prepared scaffolds under mono-culture conditions and higher cell viability rates were obtained in co-culture conditions. Larger mineralized areas were determined under co-culture conditions and calcium deposition amount significantly increased compared with that in control group samples after 21 days. Additionally, the amount of glycosaminoglycans synthesized in co-culture was higher compared to mono-culture conditions. Electric stimulation applied under mono-culture conditions suppressed the viability of MC3T3-E1 cells whereas it enhanced the viability rates of ATDC5 cells. The study suggests that the designed bilayered osteochondral constructs have the potential for osteochondral defect repair. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.