[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).

[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).