ABSTRACT
Objective:To investigate the surface characterization,cell adhension and proliferation of ultrafine grained titanium (UFG Ti) after different sand blasting and acid-etching(SLA).Methods:The billets of UFG Ti and commercially pure titanium Ti(CP Ti) were incised into cylindrical specimens with 7 mm in diameter and 2 mm in height.The specimens were sand blasted at the air pressure of 0.2,0.4,0.6 and 0.8 MPa respectively(n =10) and then acid-etched.The surface morphology,roughness and surface wettability of the specimens were examined.Rat embryo osteoblasts MC3T3-E1 were cultured on the speciments for 1 d,3 d and 5 d respectively,the cell morphology and cell density were observed.Results:The different hierarchical porous topographies were formed on the surface of UFG and CP Ti after modified by SLA.The sizes of blasted holes on the surface and the surface roughness of both materials increased with the increase of blast pressure,but the values of UFG Ti were lower than those of CP Ti correspondingly(P ＜ 0.05).The surface wettability of them was also changed with the blast pressure,but the values of UFG Ti was significantly smaller than those of CP Ti(P ＜ 0.05).When the blast pressure was 0.6 Mpa,the UFG Ti exhibited excellent wettability,the cell density was the highest,the morphology of MC3T3-E1 cells on UFG Ti was superior to that on CP Ti.Conclusion:UFG Ti exhibits proper surface morphology,roughness and excellent wettability,which is more appropriate for adhension and proliferation of MC3T3-E1 cells after modification by SLA at blast pressure of 0.6 Mpa.
ABSTRACT
Objective@#To explore the function of NLRP1 in noninfectious pulmonary injury (nonIPI) after allogeneic stem cell transplantation (allo-HSCT) .@*Methods@#In this study, we established the model of allo-HSCT with C57BL/6 and NLRP-/- mouse as recipients. Chimera rate was measured by flow cytometry. The HE staining was used to observe the pathology changes in the lungs. NLRP1 and relevant inflammatory proteins were measured by Western Blot.@*Results@#On the day 14 after allo-HSCT, the chimera rate was more than 96%, HSCs of donors had been successfully transplanted into recipients. HE staining showed that nonIPI occurred after allo-HSCT. The degrees of injuries reached the peak on day 21. In addition, the expressions of MPO, NLRP1, p20, Mature-IL-1β and Mature-IL-18 had same tends with the degrees of nonIPI. When we knocked out NLRP1 gene of recipients, the degrees of nonIPI reduced and the expressions of MPO, p20, Mature-IL-1β and Mature-IL-18 were less than in non-knockout group.@*Conclusion@#allo-HSCT could cause nonIPI and high expressions of MPO, p20, IL-1β, IL-18, NLRP1. Knocking out NLRP1 gene could alleviate the degrees of nonIPI and reduce the expressions of relevant inflammatory proteins, indicating that NLRP1 might be one of factors contributed to nonIPI after allo-HSCT.
ABSTRACT
Objective@#To evaluate the effect of sandblasting on bending strength and subcritical crack growth (SCG) under cyclic loading of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics.@*Methods@#After being polished, sixty bar-shaped specimens of Y-TZP (Wieland zirconia ceramics) were assigned to two groups (n=30) according to the random number table, the sandblasting group (SG) which was treated with sandblasting and the control group (CG) which remained untouched. In each group, half of the specimens (n=15) were subjected to bending strength test, and the results were examined by Weibull statistics and analyzed with ANOVA. The other 15 specimens in each group were subjected to fatigue tests. The results were examined by Weibull statistics and subcritical crack propagation rates were calculated.@*Results@#The bending strengths of SG and CG were (1 291±133) and (1 140±124) MPa (F=10.117, P=0.004), and the Weibull modules of the two groups were 11.06 and 10.64 respectively. The crack growth rate of SCG of SG was lower than that of CG under the same cyclic loading.@*Conclusions@#Proper sandblasting on Y-TZP ceramic can increase its bending strength and resistance to SCG.
ABSTRACT
Objective:To evaluate the reliability of flexural strength and subcritical crack growth(SCG)of WL and HT zirconia ce-ramics under cyclic loading.Methods:Bar-shaped speciments of WL(n =30)and HT(n =30)were fabricated and loaded in three-point bending and cyclically fatigued.The flexural strength and the number of cycles to fracture were obtained from three-point flexural test and cyclic fatigue test respectively.Data were examined using Weibull statistics.Pairs law was used to analysize the subcritical crack growth(SCG),the behavior of which was described in terms of crack velocity as a function of maximum stress intensity factor (KImax ).Results:The Weibull module(m)of WL and HT was 10.64 and 12.04,the stress corrosion cracking susceptive indexes(n) 23.71 and 32.87,the SCG 90% and 76.7%,the KImax 49.6% and 50.9% of its maximum stress intensity factor(KIC ),respectively. Conclusion:WL and HT produce pronounced SCG.The minimum fatigue crack growth rate of HT is lower than that of WL(νHT <νWL ).
ABSTRACT
<p><b>OBJECTIVE</b>The theory of strain energy density (SED) was combined with finite element analysis to investigate alveolar bone remodeling of the mandibular first molar with different levels of periodontal attachment under mastication loading.</p><p><b>METHODS</b>Three-dimensional finite element models of the mandibular first molar with different levels of periodontal attachment were established. Based on SED theory, the user material subroutine (UMAT) (used by ABAQUS software) was developed by ourselves to simulate the remodeling process of mandibular bone. The stress distributions and bone density changes were analyzed under different mastication loading. The influence of loading magnitude on alveolar bone remodeling with different levels of periodontal attachment was investigated.</p><p><b>RESULTS</b>The results showed that the neck of buccal, lingual regions and root apex area experienced a higher stress. The stress and the density of alveolar bone increased gradually with the enhancing of the bite force at the beginning. Then the density would appear declining when the bite force exceeded the extreme load. The extreme load reduced from 420 N to 240 N with the periodontal attachment falling from normal to 1/2 of root length also. And the remodeling rate of the bone was faster as the loading increasing.</p><p><b>CONCLUSION</b>The capability of the periodontal tissue for supporting the teeth will drop gradually as the periodontal attachment level dropping. And the decline of bone density also appeared in earlier time. The change of density is associated with mastication loading during the bone remodelling. And reducing the occlusal force properly to the molar with different attachment level is benefit for clinical treatment and prognosis of periodontal disease.</p>
Subject(s)
Humans , Bite Force , Bone Density , Bone Remodeling , Finite Element Analysis , Mandible , Mastication , Models, Biological , Molar , Stress, Mechanical , Tooth RootABSTRACT
Objectives To investigate antimicrobial resistance and beta-lactamase production of Moraxella catarrhalis isolates from respiratory tract in children and to understand the characteristics of BRO beta-lactamase gene. Methods From June 2011 to Sep-tember 2012, 401 Moraxella catarrhalis isolates were obtained from respiratory tract in children. Minimum inhibitory concentrations (MIC) of commonly-used antibiotics were determined by microbroth dilution assay, and beta-lactamase production was detected by Nitroceifn disk test. PCR combining restriction endonuclease analysis was employed to do the BRO genotyping. Results 96.5%iso-lates were beta-lactamase positive (387/401), MIC (MIC50/MIC90) values and resistant rates of beta-lactamase producing isolates were higher than those of non beta-lactamase producing isolates for ampicillin, cefaclor and cefuroxime (P<0.05). The positive rate of BRO gene was 99.2%in beta-lactamase producing isolates (384/387), consisting of 93.0%BRO-1 isolates and 7.0%BRO-2 isolates. MIC50 and MIC90 values of BRO-1+isolates were higher than those of BRO-2+isolates for ampicillin, cefaclor, cefuroxime and azithromycin. Conclusions The beta-lactamase production rate is high in Moraxella catarrhalis isolates from respiratory tract in children. BRO-1 type was the dominant genotype of beta-lactamase producing isolates, having more inlfuence than BRO-2 type in the inlfuence on some beta-lactams and macrolides.
ABSTRACT
Objective:To study the residual stress distribution through the thickness of bilayered dental ceramic subjected to thermal stress, in order to improve the restoration. Methods: The finite element model of bilayered dental ceramic was set up based on International Organization for Standardization(ISO) 96936:1999. The residual stresses were calculated in viscoelastic and elastic phases during cooling of dental ceramic to analyze the residual stress distribution. Results: The deformation of core was greater than the veneer ceramics during the cooling period of dental ceramic. The residual stress increased with the decreasing of the temperature approaching the interface of core and veneer ceramics. But it decreased with the increasing of the thickness of veneer ceramics.Conclusion: Thermal compatibility of core and veneer ceramics is very important to the residual stress distribution in the bilayered dental ceramic, which may benefit to All-ceramic restorations. The viscoelastic behavior of ceramic should be taken into account in the thermal compatibility.