Three-dimensional finite element analysis of cuspal-coverage thickness influence on the stress distribution of all-ceramic onlay-restored premolars / 华西口腔医学杂志

OBJECTIVE@#To investigate the influence of cuspal-coverage thickness on the stress distribution of all-ceramic onlay-restored premolars by using 3D finite element (FE) analysis and to provide references for the design of all-ceramic onlays for clinical application.@*METHODS@#3D FE models of all-ceramic onlays with three cuspal-coverage thicknesses (2, 3, and 4 mm) of endodontically treated maxillary premolar were constructed based on micro-CT images. Stress distributions in the onlay, adhesive resin cement layer, and dentin of models were analyzed under vertical load (600 N) and oblique load (200 N).@*RESULTS@#When the cuspal-coverage thickness increased, the peak maximum principal stress value decreased inside the onlay but increased in the margin of the adhesive resin cement layer. In addition, stress concentration areas increased in the coronal residual dentin on the palatal side under oblique load.@*CONCLUSIONS@#An increase in the cuspal-coverage thickness of all-ceramic onlays may reduce the risk of rupture of the restoration but may deteriorate the restoration and cause palatal dentin fracture.

Effects of three drying methods on the physical properties and drug delivery in chitosan microspheres / 华西口腔医学杂志

OBJECTIVE@#The purpose of this study is to investigate the effects of different drying methods on the physical properties and drug delivery of chitosan microspheres.@*METHODS@#Three types of drying methods were utilized, including air drying and freeze drying after freezing at -20 ℃ (slow cooling) and at -80 ℃ (fast cooling). The physical properties of microspheres were characterized. Utilizing bovine serum albumin (BSA) as the model drug, the in-vitro release behaviors of drug-loaded beads were investigated.@*RESULTS@#By comparing the physical properties of the different drying methods, the microspheres' diameters, porosities, and surface area were observed to increase successively from air drying and slow cooling to fast cooling, whereas the pore size and the swelling and degradation rates varied. The drug-loading experiments revealed that the loading capacity of air-dried microspheres was the lowest and the release rate was the slowest. Although the loading capacity of fast cooling microspheres was high, an obvious burst release was observed. The loading capacity of slow cooling microspheres was similar to that of the fast cooling microspheres and the loaded BSA can be released continuously.@*CONCLUSIONS@#The results indicate that different drying methods can affect the physical properties of chitosan microspheres, which further influence drug loading and release.

Research advances in endogenous neural stem cells promoting neural repair after ischemic stroke / 生理学报

Neural stem cell therapy, as a new therapeutic method for neural diseases, has aroused a wide concern for over 20 years since neural stem cells were first found in 1992. Ischemic stroke is highly concerned because of its high incidence, mortality and disability rates. Because the brain has a limited ability to repair itself, to improve neural function and promote neural regeneration may help to prevent occurrence and development of neurological diseases. It is noteworthy that some stroke patients showed an ability to repair brain several months after the stroke happened, suggesting an existence of endogenous nerve repair in these patients. The research advances in functions of endogenous neural stem cells in neural regeneration and the related regulators after ischemic stroke are summarized in this review to provide new views of the mechanism of neural functional recovery after ischemic stroke.

Rat dental papilla cell culture with nanometer-HAP in vitro / 中南大学学报(医学版)

OBJECTIVE@#To determine the effects of nano-hydroxyapatite(nano-HAP)on the proliferation and activity of rat dental papilla cells(RDPCs)in vitro, and to evaluate the feasibility of using nano-hydroxyapatite(nano-HAP)as dental papilla cell scaffold in dental tissue engineering.@*METHODS@#RDPCs cultured with the porous nano-HAP in vitro served as the experimental group, and the routine culture of RDPCs in flasks served as the control. Scanning electronic microscope was used to observe the growth and adherence of the RDPCs to nano-HAP. Cell proliferation, cellular protein content, and alkaline phosphatase(ALP) were detected to assess the cellular activities.@*RESULTS@#RDPCs proliferated well, and adhered to the outer and inner surface of the nano-HAP scaffold. Compared with the control group, cells in the experimental group presented higher proliferation on 6 d and 8 d and higher cellular protein content on 6 d and 9 d. No significant difference was detected in the ALP activity in the 2 groups.@*CONCLUSION@#RDPCs seeded into nano-HAP grow better and have more vigorous cellular activity, suggesting that nano-HAP has excellent biocompatibility with dental papilla cells, and it can serve as a promising scaffold for dental tissue engineering.

Construction of tissue engineered gingiva with gingival epithelia and acellular dermal matrix / 中南大学学报(医学版)

OBJECTIVE@#To culture human gingival epithelia in vitro, and to construct the tissue engineered gingiva with the acellular dermal matrix (ADM).@*METHODS@#Human gingival epithelia were isolated from the gingival tissue, and the cells were cultured and seeded onto the surface of ADM. After 7 days of submerged incubation, an air-liquid interface culture was performed for 7, 14, and 21 days. The complex constructed above was taken for histological examination.@*RESULTS@#Human gingival epithelia could proliferate well on the surface of ADM, and form multilayer structure. But the superficial epithelium was partially keratinized.@*CONCLUSION@#Tissue engineered gingiva may be constructed with human gingival epithelia and ADM in vitro.

Effects of Porphyromonas gingivalis lipopolysaccharide on collagen phagocytosis by human periodontal ligament fibroblasts / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS) on collagen phagocytosis of human periodontal ligament fibroblasts (hPDLF).</p><p><b>METHODS</b>Fluorescence localization and flow cytometry was used to test the collagen phygocytosis of hPDLF stimulated by the various concentration of LPS for 48 hours in vitro.</p><p><b>RESULTS</b>The collagen phygocytosis of hPDLF was increased significantly by 0.1 microg/mL LPS (P < 0.05).</p><p><b>CONCLUSION</b>This study indicates that P. gingivalis LPS may enhance the degradation of collagen by stimulating the phagocytic activity of the hPDLF in periodontitis.</p>

Effect of porcelain firing cycle on microstructure and corrosion resistance of 4 metal ceramic alloys / 中南大学学报(医学版)

OBJECTIVE@#To determine the effect of porcelain firing cycle on microstructure of 4 metal ceramic alloys, and to analyze the changes of their corrosion resistance in the artificial saliva.@*METHODS@#We simulated the process of firing and repolishing when fabricating porcelain-fused-to-metal restoration in clinic,and then observed the microstructures of Ni-Cr, Ni-Cr-Ti, Co-Cr alloys and high gold alloy by field emission scanning electron microscopy and energy dispersive spectroscopy. The electrochemical corrosion behavior of alloys in artificial saliva was analyzed by polarization curves and corrview 2 corrosion analysis software. The data of self-corrosion potential and transpassive potential were obtained and analyzed.@*RESULTS@#After the porcelain firing cycle, the surface composition changed slightly, and the morphological in the 3 predominate base metal alloys also changed. The self-corrosion potential turned to more negative, and the transpassive potential declined.@*CONCLUSION@#The procedure of porcelain firing cycle can affect the surface microstructure and increase the corrosion of 4 metal-ceramic alloys.