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.
Abstract: Dental impression materials are used to register or reproduce the form and relationship of the teeth and oral tissues. They should not be torn when removing from the wet mouth after setting. Nowadays, silica is widely used as filler to overcome the low mechanical strength of the dental impression materials. The purpose of this study was to synthesize high strength glass in the system of
MgO-CaO-Al2O3-SiO2 and investigate its usefulness according to ISO standard after mixing with addition silicone. Commercial products, Contrast, Examix, Express, and Perfect-F were selected as control group. When the prepared glass filler was introduced in addition silicone impression material, tear strength was drastically increased significantly than that of the control group, keeping the consistency. All experimental groups showed higher tear stength than that of control groups. As the
amount of filler content increases, tear strength was increased. Strain in compression, recovery from deformation, and linear dimensional change were satisfied the ISO standard either all the experimental or control groups. Therefore, calcium-substituted magnesium aluminosilicate glass in the system of 12.5MgO-17.5CaO-20Al2O3-50SiO2 is expected the useful filler in the light body of addition silicone impression materials.
Abstract: The effect of boron-containing bioactive glass (BG) particles in the SiO2-CaO-P2O5-Na2O system on the bone formation was studied by histologic, histomorphometric and microchemical evaluation. Wistar rats were used throughout. Under anesthesia, 45S5 BG particles were placed inside the medullary compartment of the tibia (Control), while in the contralateral tibia (Experimental) 45S5.2B BG particles were implanted. The animals were sacrificed 15 days postimplantation. The tibiae were resected, radiographed, and embedded in methyl methacrylate resin. Sections were stained with toluidine blue and analyzed by light microscopy, backscattered scaning electron microscopy and energy-dispersive X-ray analysis
(EDX). Histomorphometric determinations were performed. Light microscopy of the histologic sections showed lamellar bone formation surrounding both biomaterials. The histomorphometric study revealed a statistically significant increase in bone tissue around 45S5.2B BG particles.
EDX of newly formed bone tissue showed a rise in the Ca:P ratio when 45S5.2B BG particles were employed. The results described in the present study reveal that this boron-containing bioactive glass may be used as scaffold for bone tissue regeneration.
Abstract: Alkali oxides were added to glass frit in order to lower the firing temperature of dental
porcelain, and the effects of Li2O and B2O3 on the thermal properties and chemical solubility of low-fusing dental porcelain were investigated.
The glass transition temperature(Tg) and softening temperature(Ts) of glass frits were decreased remarkably by adding Li2O, but the coefficient of thermal expansion(CTE) was increased with Li2O. In the case of adding B2O3, the thermal properties were unchanged. Tg of B0L4, B2L4 and B4L4 specimens were lower than 500°C and Ts were lower than 550°C. The chemical solubility of prepared low-fusing dental porcelain with these glass frits were 37.3,
43.9, and 49.2µg·cm-2 respectively. The chemical solubility was increased by adding Li2O and B2O3, but all the results were below 100µg·cm-2 and satisfactory to ISO Standards. Further, the chemical solubility of the commercial low-fusing dental porcelains were 52.6µg·cm-2 for Ceramco Finesse(Clear), 70.8µg·cm-2 for Duceram-LFC(TC) and that of conventional dental porcelain, CeraMax(T-C), was 34.8µg·cm-2.
Abstract: The crystallization tendency for 30 experimental glasses in the system Na2O-K2O-MgOCaO-B2O3-P2O5-SiO2 was studied with thermal methods, DTA, HSM and XRD. The glasses were also immersed into simulated body fluid for 8 and 72 hours. The formation of the silica-rich gel and calcium phosphate layer on the glasses were analyzed with SEM. The in vitro behavior and crystallization tendency for heat-treated glasses were then related. This information is essential for choosing glass compositions that can be manufactured to desired products with controlled
bioactivity for different applications. In general, glasses with low alkali content can tolerate heattreatment without crystallization but have less initial Si-gel formation ability and show less in vitro bioactivity than glasses with high alkali content.
Abstract: Aqueous-based alumina tape, prepared using acrylate emulsion binder, was employed to form 3-unit all-ceramic anterior fixed partial denture core structures. Formability, linear shrinkage, and strength of the tape were optimized by adjusting tape composition to a/(a+b+p)=0.84 and b/(b+p)=0.5. Marginal fitness of the core framework was acceptable for clinical applications when more than two points on lingual side of core structure were placed to touch a plate during sintering.
The 3-unit all-ceramic anterior fixed partial denture utilized ceramic tape has functioned successfully for 3 years without any loss of structural integrity and esthetics.
Abstract: We tried to prepare a new filling material for bone defects using β-Tricalcium phosphate (β-TCP) particles and Histoacryl®. The aim of this study was to evaluate physical and bioactive properties of cyanoacrylate-based filling materials for bone defects in the dental field. The shear bond strength values of the Histoacryl® and β-TCP/ Histoacryl® compounds stored in double-distilled
water decreased with the increase of the amount of added β-TCP. The temperature change of the β-TCP/ Histoacryl® compounds during polymerization decreased compared to that of the Histoacryl®. The cytotoxicity of the filling materials decreased when the amount of added β-TCP was increased. In the evaluation of bioactivity, hydroxyapatite (HA) was precipitated on the surface and inner space of the porous filling material 4 weeks after immersion in SBF. This precipitation of HA on the surface of the filling material was also confirmed in the XRD result. These results indicate that our novel β-TCP/Histoacryl® compounds have the potential to serve as filling materials for bone defects in the dental field.
Abstract: Feldspathic porcelain paste system using organic vehicle was prepared and applied to fabricate the porcelain fused to metal fixed partial denture. The mean linear fired shrinkage of paste porcelain system was 15.2% that is 0.8% lower than that of conventional build-up method. The color difference between two methods (E*) was 0.156. Mean biaxial flexural strength of sintered preformed laminating porcelains of this system and conventionally build-up porcelains were 74±3
and 70±4 MPa respectively. There was no deterioration of physical properties of feldspathic porcelain system by introducing organic vehicle, and this new build-up method can be applied to fabricate the porcelain fused to metal restorations.
Abstract: Stimulation of bone healing through local application of growth factors from implants
may improve the clinical outcome in fracture treatments. However, the growth factors in reconstructive application require supraphysiologic dosing and considerable expense while hampering their clinical application. Genetic modification of mesenchymal stem cells (MSCs) to both produce and respond to osteogenic factors may have potential for use in enhancing bone healing. In this study, MSCs were genetically modified by a recombinant adenoviral containing the gene for human bone morphogenetic protein 2 (hBMP-2). The gene-transduced cells were
incorporated with a porous beta-tricalcium phosphate (TCP) as a novel complex. We investigated osteogeneic potential of gene-transduced MSCs/ceramic and the ability of the complex on facilitating bone formation in a radius segmental defect of rabbits. In vitro results showed that there were apparent hBMP2 gene expression and protein synthesis in MSCs with hBMP2 stably transfection, whereas negative expression of hBMP2 in controls. Histological studies demonstrated that gene-transfected MSCs/ceramic composite appeared an ability of heterotopic osteogenesis. In the segmental bone defects, endochondrial ossification at fracture sites was found in both transfected and untransfected MSCs-ceramic composites. While the composite with hBMP2 transfection showed the earliest and the most effective healing of the segmental bone defects both radiographically and morphologically. Our results show that genetically modified MSCs/ceramics
had enhanced osteogeneic capacity relative to unmodified MSCs or only ceramic implants. This study suggests that use of cell-and gene-activated bioceramics may offer promise for molecular design of implants to induce osteogenesis and enhance bone regeneration.