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Objective:To investigate the effect and mechanism of bone marrow mesenchymal stem cells (BMMSCs) on liver transplantation with 50% reduced-size in rat models.Methods:For 40 normal male Brown Norway(BN) and Lewis rats weighing 210-250 g were included respectively to generate the acute rejection models following 50% reduced-size liver transplantation in rats. The recipients were divided into BMMSCs group ( n=20) and normal saline group ( n=20). Healthy male BN rats were used to prepare BMMSCs. Transplanted liver tissues were collected at 0h, 1d, 3d, 7d post the transplantation for further analysis. Pathological changes and the extent of rejection were evaluated under the light microscope. The levels of microtubule-associated protein 1 light 3 (LC3) and autophagy regulator Beclin-1 proteins were detected by immunohistochemical analysis and Western blotting. Results:Rejection activity indices of the normal saline group at 0d, 3d, 7d after the surgery were (2.33±0.58), (4.00±0.00), (6.33±0.58). The BMMSCs group were (2.10±0.58), (3.73±0.58), (5.67±1.15), which was decreased comparing with normal saline group, difference was statistically significant ( P<0.05). On the 1d, 3d, 7d after the transplantation, compared with normal saline group, expression of autophagy-related proteins LC3 and Beclin-1 in BMMSCs group was increased ( P<0.05). Conclusions:It showed that autophagy has an effect on the protection of BMMSCs liver graft of rats.
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Objective To explore the effects of the interfacial debonding caused by water environment in the mouth and the interfacial defects between the crown and cement on stress distributions in all-ceramic crowns. Methods The three-dimensional solid model of lithium disilicate CAD/CAM crowns for the first mandibular molar was established. Seven debonding states between inferior surface of the crown and top surface of the cement (Stage 1-7) as well as two interfacial defects (Case I and II) were defined in finite element software ABAQUS. The bottom of nine models was completely constrained. For stress calculation, the 600 N vertical load was applied at occlusal surface via an analytical rigid hemisphere with the diameter of 5 mm. Results Under occlusal vertical load, the stress on interior of the crown and top surface of the cement was mainly distributed at the boundary of the debonding areas and margin of the defects. The first principle stress on interior of the crown did not exceed its ultimate tensile strength, but the maximum tensile stress of the cement exceeded its ultimate tensile strength, leading to cohesive failure in the cement. Conclusions The axial wall played a critical role in maintaining the principal tensile stress of the crown at a lower level. The defects at bonding interface between the crown and cement had a more significantly impact on load capacity of the crown than the increase in debonding areas. In order to improve load bearing capacities of all-ceramic crowns, attention should be paid to avoid defects in clinical prosthodontic practices.
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Objective To explore the effects of the interfacial debonding caused by water environment in the mouth and the interfacial defects between the crown and cement on stress distributions in all-ceramic crowns. Methods The three-dimensional solid model of lithium disilicate CAD/CAM crowns for the first mandibular molar was established. Seven debonding states between inferior surface of the crown and top surface of the cement (Stage 1-7) as well as two interfacial defects (Case I and II) were defined in finite element software ABAQUS. The bottom of nine models was completely constrained. For stress calculation, the 600 N vertical load was applied at occlusal surface via an analytical rigid hemisphere with the diameter of 5 mm. Results Under occlusal vertical load, the stress on interior of the crown and top surface of the cement was mainly distributed at the boundary of the debonding areas and margin of the defects. The first principle stress on interior of the crown did not exceed its ultimate tensile strength, but the maximum tensile stress of the cement exceeded its ultimate tensile strength, leading to cohesive failure in the cement. Conclusions The axial wall played a critical role in maintaining the principal tensile stress of the crown at a lower level. The defects at bonding interface between the crown and cement had a more significantly impact on load capacity of the crown than the increase in debonding areas. In order to improve load bearing capacities of all-ceramic crowns, attention should be paid to avoid defects in clinical prosthodontic practices.
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Objective To study the repairing effect of bone marrow mesenchymal stem cells (BMMSCs) on the donor liver after cardiac death (DCD) under normal temperature mechanical perfusion (NMP) in rats.Methods BMMSCs of Wistar rats were cultured in vitro,and 45-min warm ischemia after cardiac death model was established.The 30 Wistar rats were randomly divided into NMP,NMP + BMMSCs (N + B),cold storage (CS) groups,and the parameters were detected at 2 h and 4 h (n =10).Results N + B group was superior to NMP group and CS group in repairing the liver function and liver pathology including ultrastructure,improving the perfusate acidic environment,and increasing adenosine triphosphate level (P ＜ 0.05).The oxygen consumption of NMP group and N + B group were significantly different after 2h [2 h:(24.35 ±0.64) ml/min vs.(29.33 ±0.47) ml/min;3 h:(25.33 ±0.86) ml/min vs.(30.34 ± 0.49) ml/min;4 h:(26.88 ± 1.07) ml/min vs.(31.76 ± 0.96) ml/min;P ＜ 0.05],suggesting that the liver condition in N + B group was significantly better than that in the other two groups.Conclusion Bone marrow mesenchymal stem cells could obviously repair the DCD grafts under normal temperature mechanical perfusion.
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<p><b>OBJECTIVE</b>To study the effect of bleaching on the mechanical properties of human dentin.</p><p><b>METHODS</b>The finite element method (FEM) based the cohesive zone model had been employed to study the fracture resistance of human dentin. There types of dentin were considered, i.e. original dentin, dentin after direct-bleaching and indirect-bleaching.</p><p><b>RESULTS</b>The bleaching treatments had large impact on the crack growth resistance of human dentin. The initiation toughness (1.48 MPa x square root of m), growth toughness (3.90 MPa x square root of m x mm(-1)) and plateau toughness (3.25 MPa x square root of m) of human dentin were reduced to 1.29 MPa x square root of m, 3.45 MPa x square root of m x mm(-1) and 2.71 MPa x square root of m respectively after indirect-bleaching. The worst case was the direct-bleaching which causes significant reductions in the growth toughness (0.14 MPa x square root of m x mm(-1)) and plateau toughness (1.63 MPa x square root of m) respectively, while the initiation toughness remained the same as that after indirect-bleaching.</p><p><b>CONCLUSION</b>The cohesive zone modeling is an effective tool in characterizing the fracture behavior of human dentin. Bleaching treatments reduce the crack growth resistance of human dentin and increase the risk of fracture of teeth.</p>
Assuntos
Humanos , Dentina , Raiz DentáriaRESUMO
BACKGROUND: Metal ions released from the corrosion process of metal materials used in prosthodontics are directly related to the material biocompatibility, and decide the clinical application value and prospect in the clinical practice.OBJECTIVE: To review the metal ions released from the prosthodontic materials in the oral cavity and their biological effects.RETRIEVAL STRATEGY: Using the terms" biocompatibility, dental alloys", we retrieved PubMed data to identify studies published between January 1997 and October 2006 in the English language. A total of 67 manuscripts were researched. Inclusive criteria: mental materials used in prosthodontics. Exclusive criteria: reparative studies.LITERATURE EVALUATION: The included 67 manuscripts were all from PubMed database. After screening, 23 manuscripts were selected, among which, 20 were about original articles, and the maintaining 3 were review.DATA SYNTHESIS: At present, the research of the biological effects of metal ions released from prosthodontic materials focused on the following three areas:① The corrosion process of prosthodontic metal and the release of metal ions in the oral cavity: Two or even more kinds of metal restorations coexist in one man's oral cavity. Different metal components posed by the potential difference between the original battery will strengthen electrochemical corrosion role. This effect will accelerate the corrosion process and metal ion release, and may have a negative impact on the biocompatibility of prosthodontic materials, but the mechanism of this influence remains unclear. ②The local toxicity of the mental ions released from prosthodontic metal materials used commonly: These ions more or less have the risk of potential toxicity, but at the molecular biological level the mechanism of the adverse reaction in oral tissues acquires to be further explored. ③The hypersensitivity reaction induced by the metal ions released from prosthodontic metal materials: The ions could have an impact on the expression level of Th1 cytokines during the process of delayed-type hypersensitivity. The future research will focus on the mechanism and the establishment of immunohistochemical detection standards of biocompatibility of these prosthodontic metal materials.CONCLUSION: The metal ions released from prosthodontic materials used commonly have certain cytotoxicity, which can inhibit cell proliferation and cause mucosal diseases, oral contact gingivitis and delayed-type hypersensitivity, but at the molecular biological level the mechanism of these adverse reactions acquires to be further explored.