ABSTRACT
<p><b>OBJECTIVE</b>To compare the fracture surface of the machinable infiltrated ceramic (MIC) prepared in different conditions, and to relate its strength and toughness to the differences in their microstructures.</p><p><b>METHODS</b>The Al2O3 matrix were prepared, infiltrated by the machinable glass and crystallized. Based on sintering and infiltrating time and conditions, the specimens were divided into three groups: Perfect group, insufficiently infiltrated group, mal-sintered substrate group. Specimens were fabricated, three point flexural strength and elastic modulus were tested, and the microstructure of the MIC fracture surfaces was analyzed by means of scanning electron micrograph (SEM) observation.</p><p><b>RESULTS</b>The strength of the insufficiently infiltrated group and mal-sintered substrate group were lower than that of the perfect group, and faults in the microstructure of these two groups also proved this. The foreland of glass infiltrating in the Al2O3 and the interface of glass and complex demonstrated that the Al2O3 surface was smoother than the complex and there was a big crack in the glass but not in the complex which proved the crack resistibility of glass and Al2O3 were smaller than that of the complex (MIC).</p><p><b>CONCLUSION</b>Correct preparing process could make the glass infiltrate into properly sintered Al2O3 sufficiently which ensured best mechanical properties of the complex.</p>
Subject(s)
Aluminum Oxide , Ceramics , Dental Porcelain , Glass , Materials Testing , Microscopy, Electron, ScanningABSTRACT
This investigation was amied at the infiltrative capability of the machinable-infiltrated-ceramic(MIC) glass and the color of the composite after the MIC glass infiltrated through the aluminous matrix with different packing densities. By heating the components to 1100 degrees C for 2 hours, the MIC glass was made to infiltrate through the aluminous matrix with different packing densities. We measured the infiltrative depth and the color parameter and observed the rupture surface of the composite by means of SEM. There was a linear relation between the square of infiltrative depth and the packing density of aluminous matrix. The minimal depth was 3.092 mm. No relationship was noted between the composite's color coefficient and the packing density of aluminous matrix. In the rupture process of the composite, crack deflexion, crystal evulsion, and rupture through crystal could be observed. This experiment proved that the infiltrative characters of MIC glass meet the clinical requirement, the composite's color is steady and the mechanical intensity is stable.
Subject(s)
Aluminum Oxide , Chemistry , Ceramics , Chemistry , Color , Dental Porcelain , Chemistry , Hardness , Materials Testing , OsmosisABSTRACT
In order to develop tinted infiltration glass and its colorants, which can make the ceramic have good spectrum transmittance, color space, color stability and be suitable for clinical use, we selected the best prescription and confirm the ingredient and content of the colorants. Molten glass was prepared in Al2O3 crucible by heating the components to 1420 degrees C for 2 hours. The refractive index and thermal stability of the glass were investigated. The refractive index of the MIC infiltration glass was 1.5969(587.6 nm, nd). It was close to the index of aluminous matrix 1.759(546.07 nm, ne), which increased the spectrum transmittance of MIC. The thermal expansion coefficient of the glass was 7.565 microns/m/degree C, which was compatible with the thermal expansion coefficient of aluminous matrix(8.214 microns/m/degree C). This study proved that the tinted infiltration glass has good color stability, spectrum transmittance, and thermal expansion properties.
Subject(s)
Aluminum Silicates , Coloring Agents , Crystallization , Dental Porcelain , Elasticity , Glass , HardnessABSTRACT
Objective: To study the thermal expansion compatibili ty of a newly developed low temperature compensatory die stone (CDS) with Al 2O 3 base coping and to determine its setting time and setting expansion rate. Methods: Using HDS (Hieraus Die Stone ) as control. The ther mal expansion compatibility of CDS with Al 2O 3 was determined with TMA method on Du point 2100 thermometer;the setting time and setting expansion rate of CDS were measured with routine technique. Results: CDS showed much smaller thermal expansion with Al 2O 3 base coping than HDS.When the wa ter/powder ratio increased from 0.20 to 0.30,the setting time (h) of CDS increas ed from 12.75?0.7546 to 19.85?0.7472,that of HDS from 12.25?0.7169 to 24.00? 0.8165. The setting expansion of CDS was similar to that of HDS at various water /powder ratio. Conclusion: CDS has suitable thermal expans ion compatibility with Al 2O 3, it also has proper setting time and setting ex pansion rate to meet the clinical needs.
ABSTRACT
Objective:To study the effects of osteoid hydroxyapatite(OHA)in repair of bone defect.Methods:Bone defect in the size of 9 mm?5 mm?4 mm was made in bilateral thigh-bone entocondyle in 12 rabbits,OHA was implanted in the defects on one side and hydroxyapatite(HA)on another side.2,4,8 and 12 weeks after operation 4 rabbits were killed respectively,bone samples with the implants were prepared and examined by roentgenography,histology and SEM.New bone formation was determined by measuring the area of new bone in the samples.Results:Gross imspection and roentgenography observation showed that the defects were repaired in both groups 12 weeks after operation.Histological examination showed that new bone was increasing,absorption and disintegration of the implants were progressing from 2 to 12 weeks after operation.4,8 and 12 weeks after operation larger new bone area was found in OHA implanted defects than that in HA implanted(P