BACKGROUND:With the development of tissue engineering, porous bioceramics are more and more used to repair bone defects. Current research focuses on the biological synthesis of this bioceramics and its performance evaluation.
OBJECTIVE:To discuss the preparation of a new kind of bone cement and to determine its physicochemical properties and biocompatibility with osteoblasts.
METHODS:Biphasic tricalcium phosphate powders were prepared using co-precipitation method. The powder was turned into granular stuff by arabic gum. After sintering, porous hydroxyapatite/tricalcium phosphate bioceramics were harvested, and then mixed with alpha-hemihydrate to prepare the bone cement.
RESULTS AND CONCLUSION:X-ray diffraction confirmed that the synthetic substance was a kind of biphasic calcium phosphate ceramic having a porous structure. The bone cement could be in the plastic state within 3 minutes. The curing time was 15 minutes, and the curing temperature was 36.5℃. The maximum compression strength was 5.82 MPa, and the MTT toxicity was level 0. Osteoblasts could grew wel on the material surface.

0.05). The maximum color differences ( ?E) in the selected firing cycles were 2.279 8 and 1.389 4 for GI Ⅱand Vita In Ceram Alumina groups respectively, the maximum ?E between the two groups was 2.295 6, which fell into the clinically acceptable threshold for color differences. Conclusion: Color stability of all ceramic restorations with GI Ⅱand Vita In Ceram Alumina as substructure can be guaranteed after repeated firing of veneering porcelain up to 10 times.

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.

Objective: To investigate the properties of zirconia toughened glass infiltrated nanometer-ceramic composite (Al 2O 3/nZrO 2) . Methods: Zirconia toughened glass infiltrated nanometer-ceramic composite(Al 2O 3/nZrO 2)powder was prepared with combination of chemical co-precipitation method and ball milling. The shape, size, partical distribution, crystal phase and chemical composition were measured and analyzed. Results: (1) The crystal phase composition of the studied nanometer ceramic composite powder was made up with ?-Al 2O 3, t-ZrO 2 and m-ZrO 2 examined by XRD?(2) The density of the powder was 4.12 g/cm 3?(3) The particle distribution of the powder ranged 0.02～3.0 ?m?(4)Observed with SEM, the particle profile of the powder was regular, the ratio of length and width of the particles was about 1.2. Conclusion: The studied nanometer ceramic composite powder owns good homogeneity, stable chemical composition, reasonable powder-size gradation and may be favourable in the improvement of the packing density of ceramics.

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

Objective:To study the new bone formation after distraction osteogenesis (DO) to repair cleft palate (CP) by laser scanning confocal microscope (LSCM) and quantitive image analysis. Methods: 20 cats were assigned randomly to 3 groups: Experimental group (15 cats), the CP bone defects in hard palate were corrected with DO repair at the rate of 0.4 mm twice a day, till the transport disc (TD) reached the opposite edge across the defect region. The tetracycline labeling (30 mg/kg) were intramuscularly injected 6 days before specimens retrieval of each 3 cats at 2, 4, 6, 8 and 12 weeks after the completion of distraction. The sections were observed and analyzed by LSCM and quantitive image analysis. The results were then compared with empty control (2 cats) and experimental control group (3 cats). Results: The data showed that active new bone formation were observed in 2 weeks and reached the summit in 4 weeks. The bone formation slowed down through 8 to 12 weeks but still significantly stronger than empty and experimental control groups in which no new bone growth were observed. Conclusion:The hard palate bone defect is eventually reconstructed by DO repair and the distraction gap was filled with active de nove intramembranous osteogenesis. A consecutive dynamic curve of fluorescent labeling deposition implies active bone formation and remodeling is revealed.

This paper is aimed to investigate the effect of rest-inserted loading on the mechanosensitivity of osteocytes. In the investigation, cultured MLO-Y4 osteocyte-like cells were strained on cyclic compressive force (CCF) by the self-made compressive loading device. Then we observed the effect of different rest periods-inserted loading (5 s, 15 s, 30 s, respectively) on the mechanosensitivity of osteocytes. We then determined the levels of secreted nitric oxide (NO) and prostaglandin E2 (PGE2) by Griess method and enzyme linked immunosorbent assay (ELISA), respectively. We then stained the cytoskeleton F-actin using immunofluorescence. We found that the expressions of NO and PGE2 in rest-inserted strained groups (> 15 s) were significantly increased compared to those in the continuous strained group. And rest-inserted loading promoted the parallel alignment of stress fibers. It indicates that rest-inserted loading could promote the mechanosensitivity of osteocytes, and this might be related to the parallel alignment of stress fibers.
Actins ; metabolism ; Animals ; Cell Culture Techniques ; Cell Line ; Cytoskeleton ; metabolism ; Dinoprostone ; secretion ; Mice ; Nitric Oxide ; secretion ; Osteocytes ; secretion ; Stress, Mechanical

The objective of this research is to evaluate the effects of different silane coupling agents on the bond strength between Ceramco3 opaque porcelain and indirect composite resin. Five groups of Co-Cr metal alloy substrates were fabricated according to manufacturer's instruction. The surface of metal alloy with a layer of dental opaque porcelain was heated by fire. After the surface of opaque porcelain was etched, five different surface treatments, i.e. RelyX Ceramic Primer (RCP), Porcelain Bond Activator and SE Bond Primer (mixed with a proportion of 1:1) (PBA), Shofu Porcelain Primer (SPP), SE bond primer (SEP), and no primer treatment (as a control group), were used to combine P60 and opaque porcelain along with resin cement. Shear bond strength of specimens was tested in a universal testing machine. The failure modes of specimens in all groups were observed and classified into four types. Selected specimens were subjected to scanning electron microscope and energy disperse spectroscopy to reveal the relief of the fracture surface and to confirm the failure mode of different types. The experimental results showed that the values of the tested items in all the tested groups were higher than that in the control group. Group PBA exhibited the highest value [(37.52 +/- 2.14) MPa] and this suggested a fact that all of the specimens in group PBA revealed combined failures (failure occurred in metal-porcelain combined surface and within opaque porcelain). Group SPP and RCP showed higher values than SEP (P < 0.05) and most specimens of SPP and RCP performed combined failures (failure occurred in bond surface and within opaque porcelain or composite resin) while all the specimens in group SEP and control group revealed adhesive failures. Conclusions could be drawn that silane coupling agents could reinforce the bond strength of dental composite resin to metal-opaque porcelain substrate. The bond strength between dental composite resin and dental opaque porcelain could meet the clinical requirements.
Acrylic Resins ; chemistry ; Ceramics ; chemistry ; Composite Resins ; chemistry ; Dental Bonding ; Dental Porcelain ; chemistry ; Humans ; Polyurethanes ; chemistry ; Resin Cements ; chemistry ; Silanes ; chemistry

OBJECTIVEThe purposes of this study were to determine the spectral transmittance of GI-II glass/alumina composites and to explore the effects of different specimen thickness and fining arts of glass infiltration on the transmittance. Data were compared with those of Vita In-Ceram Alumina materials.

METHODSPlate-shaped specimens 12.5 mm in diameter, with 3 thickness (0.5, 1.0, 1.5 mm), 6 color groups for GI-II and 4 color groups for Vita In-Ceram Alumina were fabricated. Specimens of color AL2 for In-Ceram and IG2 for GI-II were selected in the study of relationship between different infiltration arts and transmittance. Five infiltration time duration and three temperatures were studied. A spectrophotometer with standard A light source paralleled light beam 5 mm in diameter and spectra range 380-780 nm was employed to measure the spectral transmittance.

RESULTSThe range of spectral transmittance were 2.7%-4.5% for GI-II and 2.4%-5.2% for Vita In-Ceram Alumina. Transmittance decreased with specimen thickness, but they were not linearly related. Transmittance of GI-II tended to increase and that of Vita In-Ceram Alumina decreased as the infiltration temperature elevated. The transmittance increased with infiltration time less than 4 hours and reduced with prolonged time over 6 hours for both materials.

CONCLUSIONGI-II glass/alumina composite has comparatively lower translucency. Influences of factors as color, thickness and infiltration arts on translucency of restorations should be considered in the clinical selection of the all-ceramic materials.

Aluminum Oxide ; chemistry ; Ceramics ; chemistry ; Dental Materials ; Dental Porcelain ; chemistry ; Glass ; chemistry ; Light ; Spectrophotometry ; Temperature ; Tensile Strength ; Transition Temperature

OBJECTIVEThe purpose of this study was to determine the thermal, mechanical properties and density of the composite infiltrated with GI-II tinted infiltration glass.

METHODSThe bar-shaped aluminum oxide and glass/alumina composite specimens with the size of 20 mm x 5 mm x 5 mm were prepared, with two free-end surfaces perpendicular to the long axis of the specimens and parallel to each other. The thermal expansion curves were obtained on a TMA2940 thermal analyzer with heating rate of 5 degrees C/min and temperature range of 25 degrees C to 1000 degrees C. The bar-shaped specimens with the size of 25 mm x 5 mm x 2 mm were fabricated and employed to test the density using Archmede's method. The flexural strength, elastic modulus were measured by means of 3-point bending test with the same specimens. The fractured specimens were indented with Vicker's diamond pyramid under load of 49 N for 15 seconds to determine the hardness and indentation fracture toughness.

RESULTSThe thermal expansion coefficient of the glass/alumina composite was 7.620 x 10(-6) degrees C-1 (25-500 degrees C), which was higher than that of Vitadur alpha veneering porcelain. The 3-poit flexural strength, elastic modulus, Vicker's hardness, indentation fracture toughness and density were 389.6 MPa, 92 GPa, 9.409 GPa, 3.2425 MNm-3/2 and 3.662 g/cm3 respectively.

CONCLUSIONThe thermal expansion of the GI-II glass/alumina composite is compatible with that of Vitadur alpha veneering porcelain, and the material could meet the strength demands for clinical use.

Aluminum Oxide ; chemistry ; Ceramics ; Dental Materials ; Dental Porcelain ; chemistry ; Glass ; chemistry ; Tensile Strength ; Transition Temperature