Papers by Keyword: Glas Ceramics

Abstract: The desirable characteristics of the microwave materials include excellent dielectric constant εr, low dielectric loss (high quality factor, Q*f0 value), and small temperature coefficient (~0ppm/°C) of resonant frequency (Tf). The advantages of using a glass-ceramic include shape stability during the sintering stage, improved dielectric properties, mechanical strength, and controlled thermal expansivity. In the present study, glass-ceramic compositions consisting of a glass system (BaO-TiO2-SiO2-Al2O3) and a ceramic filer (BaNd2Ti5O14) were prepared. The glass and glass-ceramic compositions were evaluated for sintering behavior such as shrinkage, densities, thermal properties, and microstructures. In addition, the microwave dielectric properties (≈ 15~20 for εr, > 6000 GHz for Q*f0) were determined by a network analyzer at 6-8 GHz. These results suggest that the compositions can be a candidate for LTCC dielectric materials.

Abstract: 60CaO-30P2O5-7Na2O-3TiO2 (mol%) glass-ceramic can be strongly joined with a new β-type Ti-29Nb-13Ta-4.6Zr alloy. In the present work apatite-forming ability in simulated body fluid of the glass-ceramic-coated titanium alloy was enhanced by autoclaving in water at 120°C for 1 h; surface of the autoclaved coating was completely covered with apatite after 10 days of soaking. In vivo tests showed that the glass-ceramic-coated titanium alloy after autoclaving in water makes a strong bond to natural bone.

Abstract: The purpose of this study was to compare the bone regenerative effect of calcium phosphate glass and glass-ceramics in the system of CaO-CaF2-P2O5-MgO-ZnO, which is already reported that promoted the bone-like tissue formation in vitro and formed new bone in Sprague-Dawley rats. We prepared calcium phosphate glass and glass-ceramics with Ca/P ratio of 0.6 using the system CaO-CaF2-P2O5-MgO-ZnO and subsequently milled to 400 µm. 4×4 mm 1-wall intrabony defects of six beagle dogs were surgically created and used in this study. 8 weeks after transplantation of the prepared calcium phosphate glass and glass-ceramics in the experimental group 1 and 2, respectively, the animals were sacrificed. No root resorption or ankylosis were observed in all groups. It can be examined that the prepared glass-ceramics were more effective in alveolar bone regeneration with statistical signigicant difference. In cementum regeneration, both the prepared glass and glass-ceramics showed significantly different effect. However, there were no statistical significant difference neither in glass nor glass-ceramics in the amounts of junctional epithelium migration and connective tissue adhesion. Further study is required to control the flowability as well as reduce the absorption rate in vivo.

Abstract: The purpose of our study is to compare the biodegradation and osteoconduction between CaO-SiO2-B2O3 glass-ceramics(CS10B) and hydroxyapatite(HA), tricalcium phosphate(TCP). Porous CS10B implants were prepared by polymer sponge method. Single-level posterolateral spinal fusions were performed on thirty rabbits. The animals were divided into three groups by implant material: HA, TCP and CS10B. Radiographs checked every two weeks. All animals were sacrificed 12 weeks after surgery. The proportion of the area occupied by ceramics in final radiography on the initial radiography was calculated. Uniaxial tensile strength was measured on 7 cases in each group. The proportion of the area of HA(88.7%±16.1) was significantly higher than those of the others(p<0.05), and the proportion of the area of CS10B(28.2%±9.3) was significantly lower than those of HA and TCP(37%±9.6)(p<0.05). The mean values of tensile strength of the HA(191.4±33.5 N) and CS10B(182.7±19.9 N) were significantly higher(p<0.05) than those of the TCP(141.1±28.2 N). CS10B showed the tensile strength of fusion masses similar to those of the HA, however, more rapid biodegradation than HA and TCP. These findings suggest that CS10B grafts have the possibility as a bone graft substitute.