Effect of zirconia surface modification using dopamine polymerisation on the shear bond strength of resin cement.

This study evaluated the influence of polydopamine treatment on the surface properties and bond strength of yttria-stabilised tetragonal zirconia polycrystal (Y-TZP). Sixty-three zirconia blocks (10 × 10 × 2 mm) were randomly divided into three groups defined by surface treatment: (i) control group (C), (ii) grit-blasted with 110 µm alumina particles (GB), and (iii) polydopamine (PDA) coating. The surfaces of specimens subjected to different treatments were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and water contact angle measurements. After the surface treatments, the specimens were cemented to resin composite cylinders. After bonding, the shear bond strength of the ceramic to the resin was measured, and the failure mode of each specimen was analysed using a stereomicroscope. The results indicated that the shear bond strength is highest for the GB treatment and lowest for the controls. However, the difference between groups GB and PDA was not statistically significant. In the control group, adhesive failure was predominant, whereas in the treatment groups, mixed mode failure was predominant. The pre-treatment of Y-TZP ceramic with the polydopamine coating might improve the bond strength of the resin cement to the zirconia ceramic.

[Temporal and spacial expression of perlecan in dental pulp after injury].

PURPOSE: To investigate the temporal and special expressions and functions of perlecan in dental pulp of rats after injury. METHODS: Specimens of one side of maxillary molars of 24 male SD rats were collected 1,3,5,7 days after injury, and the other side were used as controls. The specimens were decalcified and embedded in paraffin, sliced by longitudinal section and stained by immunohistochemistry. The staining of perlecan and ß1 integrin were examined, and the average optical density (AOD) was compared. The measurement data were analyzed by ANOVA using SPSS 19.0 software package. RESULTS: The staining intensity of perlecan in dental pulp in the experimental group was significantly higher compared with that of the control group. The immunolocalization of perlecan in dental pulp was gradually progressed as the inflamed tissue was progressing after injury, and its AOD was significantly higher than that of control group (F=11.104,P>0.05), especially in the group of 1 d. The staining of ß1 integrin was generally enhanced in the pulp 3 d after injury, and its AOD was significantly higher than that of control group (F=124.18,P>0.05). CONCLUSIONS: Perlecan may play an important role in tissue defense mechanism after injury through regulating angiogenesis and inflammatory cell infiltration. Supported by Science and Technology Research Project of Department of Education of Zhejiang Province (20051196) and Wenzhou City (Y20100015).

Lanthanum-containing hydroxyapatite coating on ultrafine-grained titanium by micro-arc oxidation: a promising strategy to enhance overall performance of titanium.

Titanium is widely used in biomedical materials, particularly in dental implants, because of its excellent biocompatibility and mechanical characteristics. However, titanium implant failures still remain in some cases, varying with implantation sites and patients. Improving its overall performance is a major focus of dental implant research. Equal-channel angular pressing (ECAP) can result in ultrafine-grained titanium with superior mechanical properties and better biocompatibility, which significantly benefits dental implants, and without any harmful alloying elements. Lanthanum (La) can inhibit the acidogenicity of dental plaque and La-containing hydroxyapatite (La-HA) possesses a series of attractive properties, in contrast to La-free HA. Micro-arc oxidation (MAO) is a promising technology that can produce porous and firmly adherent hydroxyapatite (HA) coatings on titanium substrates. Therefore, we hypothesize that porous La-containing hydroxyapatite coatings with different La content (0.89%, 1.3% and 1.79%) can be prepared on ultrafine-grained (~200-400 nm) titanium by ECAP and MAO in electrolytic solution containing 0.2 mol/L calcium acetate, 0.02 mol/L beta-glycerol phosphate disodium salt pentahydrate (beta-GP), and lanthanum nitrate with different concentrations to further improve the overall performance of titanium, which are expected to have great potential in medical applications as a dental implant.

In vivo evaluation of in situ polysaccharide based hydrogel for prevention of postoperative adhesion.

In this paper, the carboxymethyl chitosan/oxidized dextran hydrogel was developed and its potency application in the prevention of postoperative adhesion was investigated. The developed hydrogel showed porous and interconnected interior structure with pore size about 250 µm, which was sensitive to lysozymic solution (1.5 µg/ml) with almost complete degradation after 4 weeks of in vitro incubation. In vivo study suggested that the developed hydrogel showed the great capacity on the prevention of postoperative adhesions in rat model. According to the result of histopathological examination, it clearly showed that the mesothelial cell layer of abdominal wall and cecum were completely recovered after 7 days of surgery in 3% carboxymethyl chitosan/oxidized dextran hydrogel group, while obvious adhesion between abdominal wall and cecum was observed as treatment with saline solution or 3% carboxymethyl chitosan solution after 1 day of surgery. All these results suggested that the developed biodegradable hydrogel might have potential application in the prevention of postoperative adhesion.

Sol-gel-derived hydroxyapatite-carbon nanotube/titania coatings on titanium substrates.

In this paper, hydroxyapatite-carbon nanotube/titania (HA-CNT/TiO(2)) double layer coatings were successfully developed on titanium (Ti) substrates intended for biomedical applications. A TiO(2) coating was firstly developed by anodization to improve bonding between HA and Ti, and then the layer of HA and CNTs was coated on the surface by the sol-gel process to improve the biocompatibility and mechanical properties of Ti. The surfaces of double layer coatings were uniform and crack-free with a thickness of about 7 µm. The bonding strength of the HA-CNT/TiO(2) coating was higher than that of the pure HA and HA-CNT coatings. Additionally, in vitro cell experiments showed that CNTs promoted the adhesion of preosteoblasts on the HA-CNT/TiO(2) double layer coatings. These unique surfaces combined with the osteoconductive properties of HA exhibited the excellent mechanical properties of CNTs. Therefore, the developed HA-CNT/TiO(2) coatings on Ti substrates might be a promising material for bone replacement.

Preparation and characterization of cationic curcumin nanoparticles for improvement of cellular uptake.

In the present paper, cationic nanoparticles of curcumin, chitosan and poly(ɛ-caprolactone) were developed by a simple nano-precipitation method. The developed curcumin loaded chitosan/poly(ɛ-caprolactone) (chitosan/PCL) nanoparticle showed almost spherical shape and its diameter was varied between 220 nm and 360 nm and zeta potential was varied between +30 mV and 0 mV as a function with pH value. The encapsulation of curcumin into nanoparticles was confirmed by fluorescence spectral analysis. In vitro release study showed the sustained release behavior of curcumin from nanoparticles during the period of 5 days study. In vitro cytotoxicity test revealed the drug concentration dependent on the cell viability against Hela cells and OCM-1 cells after 48 h co-incubation. Furthermore, in vitro cell uptake study revealed that the cell uptake of curcumin was greatly enhanced by encapsulated curcumin into cationic chitosan/PCL nanoparticles. Therefore, the developed cationic chitosan/PCL nanoparticles might be a promising candidate for curcumin delivery to cancer cells.

[Influence of MgO and TiO2 on mechanical properties of zirconia toughened alumina ceramics formed by gel-casting technique].

OBJECTIVE: The objective of this study is to investigate the influence of mechanical properties and sintering performance by adding 5% weight percentage aids to nano-compound zirconia toughened alumina (ZTA) ceramics. METHODS: Micrometer Al2O3 and nanometer ZrO2 (quality ratio 4:1) were used to get 55% volume percentage slurry. Magnesium oxide and titanium oxide were taken as aids which were 5% weight percentage of the Al2O3 and ZrO2 powder. Five groups (number 0, 1, 2, 3, 4 group) were divided according to different proportion of aids. After gel-casting, the porcelain pieces were sintered at 1150, 1200, 1300, 1400, 1450, 1500, 1600 degrees C for 2 hours. Static three-point flexure strength, line shrinkage, relative density were measured and scanning electron microscopy (SEM) was used to observe section. RESULTS: Number 1 (MgO 1%, TiO2 4%) group had the highest bending strength. It was (401.78+/-19.50) MPa after sintering at 1600 degrees C for 2 hours and was higher than 0 group (380.64+/-44.50) MPa. Bending strength became lower than 0 group when MgO was more than 2% or more than that weight percentage of ZTA powder. When MgO content was higher than 2% or more than that weight percentage, there was no difference in relative density raising rate between each sintering assistants groups. When the sintering temperature was higher than 1200 degrees C, all groups showed obvious line-shrinkage and the groups which contained sintering assistants were all was higher than 0 group. CONCLUSION: Adding MgO and TiO2 aids from 1% to 4% weight percentage of ZTA will promote fritting and increase ZTA nano-compound ceramics mechanical properties. Adding 2% MgO aids or more than that weight percent will has no obvious help to increase the relative density raising rate of ZTA nano-compound ceramics and will degrade the mechanical properties of ZTA nano-compound ceramics.

[Effects of fluid shear stress on apoptosis of osteoblasts and expression of bcl-2,Bax and caspase-3].

PURPOSE: The aim of the present investigation is to evaluate the effects of fluid shear stress on the cells of osteoblasts and to determine the mechanisms involved. METHODS: The fluid shear stress with a magnitude of 0 (control group), 0.6, 1.0, 2.0, 3.0, 4.0, 5.0 Pa was exerted on the third passage of osteoblasts for 1 hour,and incubation in static condition for 24 hours. The cell apoptotic index was tested by the terminal transferase dUTP nick end-labeling(TUNEL) method. The expression of bcl-2 ,Bax and caspase-3 were detected by immunohistochemical method. Statistical analysis was performed using SPSS11.5 software package for one-way ANOVA. RESULTS: The apoptosis of osteoblasts and the expression of bcl-2, Caspase-3 were not affected significantly by the fluid shear stress with a magnitude from 0 to 2.0 Pa(P>0.05) . But in the 3.0,4.0 and 5.0 Pa groups, the number of apoptotic cells and the expression of caspase-3 increased while the expression of bcl-2 decreased(P<0.05).There was no significant difference in expression of Bax in all groups. CONCLUSIONS: The physiological fluid shear stress does not affect apoptosis of osteoblasts. However,the fluid shear stress of over-magnitude may lead to the decrease the expression of bcl-2,which results in activation of caspase-3 and apoptosis of osteoblasts. Supported by Research Grant from Zhejiang Provincial Education Committee(Grant No.20061823).