Can the modeling for simplification of a dental implant surface affect the accuracy of 3D finite element analysis?

The aim of this study was to assess stress/strain of different implant modeling simplifications by 3D-FEA. Three variation of external hexagon implant (Ø3.75?×?10 mm) supporting one molar crown were simulated: A (no threads); B (slightly threads simplification); C (original design). 200 N (axial) and 100 N (oblique) were applied. Cortical bone was evaluated by maximum principal stress and microstrain qualitatively and quantitatively (ANOVA and Tukey post hoc (p < 0.05)). Higher stress levels (p < 0.05) were observed in model A. Models B and C presented similar stress transmission. It was possible to conclude that slightly simplification should be used for studies evaluating stress transferring for bone tissue.     

三维联合培养牙髓细胞和血管内皮祖细胞促进成牙本质向/成骨向分化

目的:探讨三维联合培养牙髓细胞(dental pulp cells, DPCs)和血管内皮祖细胞(endothelial progenitor cells, EPCs)对成牙本质向/成骨向分化的影响。方法:取单独培养DPCs及联合培养的DPCs和EPCs进行三维培养后成牙本质向/成骨向诱导,使用茜素红染色及半定量分析、RT-PCR和细胞免疫荧光检测成牙本质向/成骨向分化能力。采用SPSS 23.0统计软件对数据进行统计学分析。结果:茜素红染色显示联合培养组和单独培养组之间未见显著差异。RT-PCR和细胞免疫荧光显示成牙本质向/成骨向相关基因m RNAs和蛋白表达水平联合培养组显著高于单独培养组。结论:三维联合培养的DPCs和EPCs促进成牙本质向/成骨向分化,为牙髓再生提供可能实验依据。     

The histone-like protein HupB influences biofilm formation and virulence in Xanthomonas citri ssp. citri through the regulation of flagellar biosynthesis

Citrus canker is an important disease of citrus, whose causal agent is the bacterium Xanthomonas citri ssp. citri (Xcc). In previous studies, we found a group of Xcc mutants, generated by the insertion of the Tn5 transposon, which showed impaired ability to attach to an abiotic substrate. One of these mutants carries the Tn5 insertion in hupB, a gene encoding a bacterial histone-like protein, homologue to the β-subunit of the Heat-Unstable (HU) nucleoid protein of Escherichia coli. These types of protein are necessary to maintain the bacterial nucleoid organization and the global regulation of gene expression. Here, we characterized the influence of the mutation in hupB regarding Xcc biofilm formation and virulence. The mutant strain hupB was incapable of swimming in soft agar, whereas its complemented strain partially recovered this phenotype. Electron microscope imaging revealed that impaired motility of hupB was a consequence of the absence of the flagellum. Comparison of the expression of flagellar genes between the wild-type strain and hupB showed that the mutant exhibited decreased expression of fliC (encoding flagellin). The hupB mutant also displayed reduced virulence compared with the wild-type strain when they were used to infect Citrus lemon plants using different infection methods. Our results therefore show that the histone-like protein HupB plays an essential role in the pathogenesis of Xcc through the regulation of biofilm formation and biosynthesis of the flagellum.