Hydrolysis of amelogenin by matrix metalloprotease-20 accelerates mineralization in vitro

In the following respects, tooth enamel is a unique tissue in the mammalian body: (a) it is the most mineralized and hardest tissue in it comprising up to 95 wt% of apatite; (b) its microstructure is dominated by parallel rods composed of bundles of 40–60 nm wide apatite crystals with aspect ratios reaching up to 1:10,000 and (c) not only does the protein matrix that gives rise to enamel guides the crystal growth, but it also conducts its own degradation and removal in parallel. Hence, when mimicking the process of amelogenesis in vitro, crystal growth has to be coupled to proteolytic digestion of the amelogenin assemblies that are known to play a pivotal role in conducting the proper crystal growth. Experimental settings based on controlled and programmable titration of amelogenin sols digested by means of MMP-20 with buffered calcium and phosphate solutions were employed to imitate the formation of elongated, plate-shaped crystals. Whilst amelogenin can act as a promoter of nucleation and crystal growth alone, in this study we show that proteolysis exerts an additional nucleation- and growth-promoting effect. Hydrolysis of full-length amelogenin by MMP-20 decreases the critical time needed for the protein and peptides to adhere and to cover the substrate. The formation and immobilization of a protein layer subsequently reduces the time for calcium phosphate crystallization. Coupling the proteolytic reaction to titration in the presence of 0.4 mg/ml rH174 has been shown to have the same effect on the crystal growth promotion as quadrupling the concentration of rH174 to 1.6 mg/ml. Controlling the rate and the extent of the proteolytic cleavage can thus be used to control the nucleation and growth rates in a protein-guided crystallization system.     

胶囊粉对可见光固化复合树脂机械性能的影响

目的:改善光固化复合树脂的强度和抛光性能.方法:我们采用悬浮聚合法研制了微胶囊型复合填料粉(MCP),作为光固化改进型(VLC-Ⅱ型)复合树脂的填料.并对其性能进行了测试.结果:在复合树脂中加入15%的胶囊型填料粉,压缩强度可达232.1±9.1MPa,拉伸强度可达48.7±2.3MPa,70000次牙刷磨耗率为0.588%,表面粗糙度为2.8μm.结论:胶囊粉可以显著改善复合树脂的压缩强度,拉伸强度,磨耗及表面抛光性等机械性能.与其它同类产品比较,其机械性能、磨耗性能和表面抛光性能均较优越,且相差显著.     

中国人面神经神经电图正常值与影响因素的探讨

用调节刺激电流强度的方法８６例成年中国人的１７２条面神经电图。结果显示中国人神经电图中肌肉复合动作电位的波幅与潜伏期均呈正态分布，波幅值３．９４±１．０２ｍＶ，变异系数２５．８％；潜伏期３．１８±０．４２ｍｓ，变异系数１３．２％。是无明显差异。左右侧基本对称，作认为，鉴于个体差异较大，对神经电图的解释分析应以左右对称为基点。对影响常人面神经神经电图的各种因素作了较深入的探讨。     

Ethanol wet-bonding challenges current anti-degradation strategy

The long-term effectiveness of chlorhexidine as a matrix metalloproteinase (MMP) inhibitor may be compromised when water is incompletely removed during dentin bonding. This study challenged this anti-bond degradation strategy by testing the null hypothesis that wet-bonding with water or ethanol has no effect on the effectiveness of chlorhexidine in preventing hybrid layer degradation over an 18-month period. Acid-etched dentin was bonded under pulpal pressure simulation with Scotchbond MP and Single Bond 2, with water wet-bonding or with a hydrophobic adhesive with ethanol wet-bonding, with or without pre-treatment with chlorhexidine diacetate (CHD). Resin-dentin beams were prepared for bond strength and TEM evaluation after 24 hrs and after aging in artificial saliva for 9 and 18 mos. Bonds made to ethanol-saturated dentin did not change over time with preservation of hybrid layer integrity. Bonds made to CHD pre-treated acid-etched dentin with commercial adhesives with water wet-bonding were preserved after 9 mos but not after 18 mos, with severe hybrid layer degradation. The results led to rejection of the null hypothesis and highlight the concept of biomimetic water replacement from the collagen intrafibrillar compartments as the ultimate goal in extending the longevity of resin-dentin bonds.     

骨髓基质细胞-牙根-珊瑚羟基磷灰石复合体体内再植的初步观察

目的:评价体外构建的骨髓基质细胞(BMSCs)、珊瑚-羟磷灰石支架(CHA)、牙根复合体植入体内后牙根周组织的再生情况。方法:体外分离纯化的狗BMSCs分别与牙根及CHA支架共培养形成复合体后植入体内生长,16周后取材,组织切片观察牙根周组织的再生情况。结果:实验组较对照组所不同的是:有更趋成熟、致密的牙槽骨生成;牙根与牙槽骨之间形成了清晰的软组织间隙———类牙周膜结构,主要由纤维组织、毛细血管组成。结论:BMSC-CHA-牙根复合物植入体内后有效促进牙周组织的再生;组织工程学方法促进牙周组织再生具有可行性。     

bcl-2和bax在成釉细胞瘤中的表达

目的:通过检测凋亡相关基因bcl-2和bax在成釉细胞瘤(am elob lastom a,AB)中的表达,探讨AB发生发展中细胞凋亡的作用及其与AB临床生物学行为的关系。方法:采取免疫组化法对75例AB(原发31例,复发37例,恶变组7例)进行BCL-2和BAX蛋白检测,正常口腔黏膜(norm al oralmucosa,NOM)和牙源性角化囊肿(odontogen ic keratocyst,OKC)做对照。同时采用原位杂交法检测了20例AB、12例OKC中的bcl-2和baxmRNA表达。结果:BCL-2蛋白阳性表达率在AB中为88.0%(66/75),OKC中为74.3%(26/35),NOM中为44.4%(4/9)(P<0.001),主要在AB外周层细胞和少数星网状层细胞中表达。BAX蛋白阳性率AB为74.7%(56/75),OKC为65.7%(23/35),NOM为77.8%(7/9)(P<0.001),BAX在AB的外周层和星网状层细胞都有强度相似的表达。伴随着AB的复发恶变BCL-2蛋白表达增强,而BAX蛋白表达则不同:复发组阳性率较原发组高,但恶变组低。BCL-2与BAX蛋白表达呈中度负相关(rκ=-0.331,P<0.001)。结论:AB中凋亡抑制蛋白表达多于凋亡促进蛋白表达,凋亡抑制在AB的发生、发展中起着重要作用。bcl-2和bax在不同组织及良、恶性AB中的表达方式及强度有差异。     

姜黄素对口腔舌癌细胞增殖与转移能力影响的实验研究

目的 探讨姜黄素对口腔舌癌细胞增殖与转移能力的作用及其作用机制.方法分别以0、5、10、20、30、60、100μmol·L-1姜黄素处理人舌癌细胞SCC-4 24 h,采用MTT法、侵袭实验、流式细胞仪、免疫荧光显微镜分别检测姜黄素对口腔舌癌细胞增殖与转移能力的影响.然后,采用cDNA微陈列芯片技术筛选和实时定鼍RT...     

白细胞介素-1单核苷酸多态性与甘肃回族、东乡族人群慢性牙周炎的相关性研究

目的 通过检测并分析白细胞介素(IL)-1B+3954位点的单核苷酸多态性(SNP),探索其与甘肃回族与东乡族人群慢性牙周炎的关系.方法 收集215例回族、东乡族慢性牙周炎患者及219例正常对照组健康者的静脉血,提取外周静脉血白细胞DNA,采用聚合酶链式反应-限制性片段长度多态性技术(PCR-RFLP)方法检测IL-1...     

Removal of extrinsic stain using a 7.0% sodium hexametaphosphate dentifrice: a randomized clinical trial

A nine-week, randomized and controlled clinical trial was conducted to compare the stain removal efficacy of a 0.243% sodium fluoride dentifrice containing 7% sodium hexametaphosphate (5% hexametaphosphate anion) to that of a 0.243% sodium fluoride control dentifrice. Following prophylaxis and a three-week pre-treatment period to induce extrinsic stain, healthy adult volunteers with tooth stain were randomized to the sodium hexametaphosphate dentifrice or the control. Stain area and intensity were assessed at baseline, three and six weeks. At both three and six weeks, the sodium hexametaphosphate dentifrice was statistically significantly superior to the control for all overall stain measures (p < 0.04). After six weeks of product usage, the sodium hexametaphosphate dentifrice demonstrated reductions of 29% in composite stain, 24% in stain intensity, and 25% in stain area relative to the control. Significant reductions in composite stain were seen on both gingival and body regions for the sodium hexametaphosphate dentifrice versus the control at three and six weeks. Both products demonstrated favorable safety profiles, as determined by oral soft tissue evaluations and recording of subject-reported adverse events.     

Establishment of cell free conversion system with biotin-labelled recombinant PrPsen expressed in E. coli

Objective To report a protocol using biotin-labelled PrP protein in cell free conversion assay instead of isotope. Methods A hamster PrP protein （HaPrP） was expressed in E. coli and purified with HIS-tag affinity chromatograph. After being labelled with biotin, HaPrP was mixed with PrP^sen preparation from scrapie strain 263K. Results Protease-resistant bands were detected after four-day incubation. Conclusion The new conversion model provides a reliable, easily handling, and environment-friendly method for studies of prion and transmissible spongiform encephalopathies.