ABSTRACT
In recent years, stem cells have been studied for treating tooth loss. The present study aimed to investigate the roles of dentin non-collagen protein (DNCP)-associated microenvironments in the differentiation of induced pluripotent stem cells (iPSCs) into dentin cells. iPSCs were cultured and identified by examining octamer-binding transcription-factor-4 (Oct-4) and sex-determining region-Y-2 (Sox-2) expression. iPSCs were differentiated by culturing DNCP-associated microenvironments (containing specific growth factors), and they were divided into control, DNCP, DNCP+bone morphogenetic proteins (BMPs) and DNCP+Noggin (a BMP inhibitor) groups. Msh homeobox 1 (Msx-1), dentin sialophosphoprotein (DSPP) and dentin matrix protein 1 (DMP-1) mRNA expression was evaluated using reverse transcription-quantitative PCR. The levels of p38, phosphorylated (p)-p38, Smad and p-Smad were determined by western blotting. Upon treatment with mouse embryonic fibroblasts, iPSCs-dependent embryoid bodies (EBs) were successfully generated. iPSCs exhibited increased Oct-4 and Sox-2 expression. Differentiated iPSCs had higher expression levels of DSPP, DMP-1 and Msx-1 in the DNCP group compared with those in the control group (P<0.05). Noggin treatment significantly downregulated, while BMPs administration significantly increased the expression levels of DSPP, DMP-1 and Msx-1 compared with those of the DNCP group (P<0.05). The ratios of p-p38/p38 and p-Smad/Smad were significantly higher in the DNCP group compared with those in the control group (P<0.05). Noggin and BMPs significantly decreased ratios of p-p38/p38, compared with those of the DNCP group (P<0.05). In conclusion, DNCP induced the differentiation of iPSCs into odontoblasts by activating the Smad/p-Smad and p38/p-p38 signaling pathways.
ABSTRACT
@#The aims of tooth restoration of endodontically treated teeth are to protect the remaining dental tissue; restore coronal morphology, functions and aesthetics; prevent bacterial microleakage and ensure periodontal healthy; prevent fracture of the restorations and reduce the wear from antagonist teeth. This article reviews the preservation and minimally invasive restoration of endodontically treated teeth. The results of the literature review show that tooth fracture resistance decreases after root canal treatment, the amount of remaining tooth tissue is an important factor affecting the success of root canal treatment, and the neck is the stress concentration area of tooth tissue, the traditional full crown and postcore crown have a certain amount of abrasion on the healthy neck teeth tissue, which will further reduce the bending resistance of the teeth and may cause the teeth to fracture. With the development of bonding technology, composite resin materials and ceramic materials, there are fewer molar tissues removed when resin, inlay, onlay, overlay and inlay crown are used to repair tooth defects, which can better preserve the remaining tooth tissues, especially the neck tooth tissues. After root canal treatment, only the pulp cavity of the tooth can be directly repaired by resin. When the marginal ridge is absent, minimally invasive restoration methods, such as inlay, onlay, and inlay crown, can be selected according to the number of marginal ridges removed and the thickness of the remaining dental tissue.
ABSTRACT
The landfill gas, biochemical indications of leachate and toxicity of leachate had been investigated in two simulated anaerobic bioreactors. After 40 days of simulated rainfall, one reactor was recharged with the original leachate directly while the other one was recharged with the adjusted leachate of which the pH was changed to 7.5. The results indicate that during the simulated rainfall the garbage is acidified rapidly with the pH value decreased to 5.21. Recharged with the original leachate, acidification of the landfill layer is deteriorated. Recirculation of the adjusted leachate, which can produce methane rapidly, can also remove organic pollutants significantly. At the 80th day methane production rate is up to 64.8%. After 170 days, the removal of BOD5 comes to 93.5% while the removal of COD is 89.1%. Furthermore, the biological toxicity of leachate decreases significantly and the semi-lethal concentration of leachate to tetrahymena rises to 3.27% from 0.24% within 24 hours.
