Papers by Author: Jun Cui

Abstract: The purpose of this study is to determine the bi-axial flexural strength, weibull modulus and fracture mode of bilayered alumina glass-infiltrated core and the veneering porcelain. Forty disk specimens were fabricated from alumina glass-infiltrated core (HSDC-A) and veneer porcelain (Vintage AL). The specimens were equally divided into four groups as: MV, monolithic specimens of veneer material; MC, monolithic specimens of core material; BV, bilayered specimens with the veneer in tension; BC, bilayered specimens with core material in tension. Mean flexure strength, standard deviation and associated Weibull modulus were determined using bi-axial flexure (ball-on-ring) for each group. Both optical and scanning electron microscopy were employed for identification of the fracture mode and origin. The surface loaded in tension influenced the bi-axial flexural strength and reliability of the composites. The frequency of specimen delamination, Hertzian cone formation and sub-critical radial cracking in the bilayered discs are also dependent on the surface loaded in tension.

Abstract: This study is to investigate the method of pamidronate modifying HA bioceramics and the effect of pamidronate modifying HA bioceramics on the osteoblastic cells. Pamidronate was immobilized on the surface of porous HA bioceramics for bone scaffold by chelating. The outermost layer of the specimens was analyzed by XPS and FT-IR. The depth profile was investigated by the argon-ion sputtering method. The MC3T3-E1 osteoblastic cells were inoculated and cultured on the scaffolds. SEM and phase contrast microscope observation of the cells, MTT test and ALP activity test evaluated the cell attachment, proliferation and activity on the scaffolds. Characteristic peaks in XPS and FT-IR spectra indicated pamidronate being immobilized on the surface of the bioceramics. The cell culture test indicated that the cells actively proliferated on the scaffolds. There was no significant difference between the ALP activity of the cells cultured for 1d, 3d and 7d on PAM-HA and that of the controls. The result indicated that PAM-HA bioceramics had favorable cytocompatibility to be used as bone scaffold with potential ability to improve osteogenesis.

Abstract: This study is to investigate the effect of PAM on protein adsorption and osteoblastic cells adhesion to HA bioceramics. PAM was immobilized on the surface of HA bioceramics for bone scaffold by chelating. The outermost layer of the specimens was analyzed by XPS and FT-IR. The protein adsorption test was performed using the 10% bovine calf serum absorbed on the specimens in vitro. The osteoblastic cells were inoculated and cultured on the scaffolds. SEM, MTT test and ALP activity test evaluated the cell attachment, proliferation and activity on the scaffolds. Characteristic peaks in XPS and FT-IR spectra indicated PAM being immobilized on the surface of the bioceramics. PAGE and 2-D DIGE results indicated that HA absorbed more acidic proteins, while PAM-HA absorbed more basic and neutral proteins.The cell culture test indicated that the cells actively proliferated on the scaffolds. There was no significant difference between the ALP activity of the cells cultured for 1d, 3d, 5d and 7d on PAM-HA and that of the controls. PAM had no obvious effect on the cytocompatibility of HA, and PAM-HA bioceramics could be used as bone scaffold with potential ability to improve osteogenesis.

Abstract: Dental ceramic materials do not always show linear expansion behavior. In general, thermal contraction behavior of dental porcelain can be described with the polynomial function: L/L= C+α1 T+α2 T2. In addition, a new method for taking into consideration of nonlinear contraction behavior of dental ceramics is proposed for calculating thermal mismatch value (α) between substrate and veneering materials. Discs of eight substrate/veneer combinations (n=10) were fabricated for thermal shock testing. In this study, a stepwise multiple regression analysis was performed to determine the relationship between thermal shock test results and thermal mismatch value (α) on these combinations. A high degree of correlation was found between αs-b and T. The new method proves to be a reliable one to predict thermal compatibility of multi-layer dental ceramic composites.

Abstract: This in vitro study compared the wear behavior between the enamel/dentine, two types of dental veneering ceramics for all-ceramic restorations (Vita-alpha，Vintage -AL ). A variety of factors including hardness, fracture toughness, flexural strength, frictional coefficients, wear scar width, element concentrations were considered. The wear scars of the samples were characterized by dynamic atomic force microscopy (DFM). The element concentrations of the surface before/after the wear test were determined with energy dispersion spectrometry (EDS). In this study Enamel/dentine, Vita-alpha and Vintage-AL have showed good wear resistance. The results also showed that there were statistical significance in samples. The friction coefficient varied from time in each kind of materials. The analytical differences between materials were observed in wear width and properties of materials (p<0.05). The wear ability among four materials ranked from highest to lowest as follows, Vintage-AL, Vita-alpha, enamel and dentine. DFM results demonstrated the wear patterns of natural tooth detected as abrasive and denaturation of dental texture. Wear patterns of tested veneering ceramics consisted mainly of abrasive wear, adhesion and fatigue wear and the different pattern plays different roles in Vita-alpha and Vintage-AL. The EDS results showed the element concentration of Fe was obviously found on the samples. Resistance ability against wear of veneering ceramics is better than that of natural human teeth. And the ability may have some correlation with the ceramics mechanical properties.

Abstract: Merwinite powders were synthesized by a sol-gel process. The bioactivity in vitro of merwinite was investigated by soaking the powders in simulated body fluid (SBF), the growth of hydroxyapatite(HAp) on the surface of the powder was evaluated in various time. It was found that hydroxyapatite was formed after soaking for 14 days. The results indicate that merwinite possessed apatite-formation ability might be a potential candidate biomaterial for hard tissue repair.