钴铬合金表面镀氮化锆涂层对细菌黏附性能的影响

背景：细菌黏附与钴铬合金材料的表面性能密切相关,因此近年来材料的表面改性技术成了该领域的研究重点。 目的：验证钴铬合金表面所镀氮化锆薄膜是否可以改善义齿金属材料的细菌黏附性能。 方法：应用磁控溅射沉积方法在钴铬合金材料表面镀氮化锆薄膜,制备钴铬合金镀膜组试件(实验组),以未镀膜的钴铬合金试件为对照组,分别将变形链球菌、白色念珠菌和黏液放线菌接种在两组试件的测试面上,待培养结束时进行菌落计数。 结果与结论：细菌黏附实验结果显示,实验组3种细菌的菌落计数均低于对照组,差异有显著性意义(P < 0.05),对照组的细菌黏附数量明显高于镀膜组。提示：钴铬合金表面所镀氮化锆薄膜可以显著降低变形链球菌、白色念珠菌及黏性放线菌的黏附数量,从而改善钴铬合金材料的细菌黏附性能。  中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

冷光美白对釉质表面细菌生物膜形成的影响

目的:研究Beyond冷光美白对牙釉质表面主要致龋菌生物膜形成的影响。方法:制备4 mm×4 mm×1 mm的釉质片20片,随机分为冷光美白组、美白剂组、冷光照射组和对照组4组,每组5片。冷光美白组用Beyond美白凝胶（主要成分为H₂O₂）+冷光照射美白3次,每次12 min;美白剂组只在釉质片表面涂布美白凝胶美白3次,每次12 min;冷光照射组仅用冷光灯照射釉质片3次,每次12 min;对照组不做任何处理。在人工口腔模型内,将上述4组釉质片置于变形链球菌、黏性放线菌、具核梭杆菌混合菌液中培养36 h,用激光共聚焦显微镜(confocal laser scanning microscopy, CLSM）观察所形成的混合细菌生物膜,采用SAS8.2软件包对所得数据进行Kruskal-Wallis秩和检验。结果:CLSM扫描可见冷光美白组、美白剂组、冷光照射组的生物膜较对照组生物膜稀疏,生物膜厚度均显著小于对照组（P<0.05）;冷光美白组、美白剂组、冷光照射组之间生物膜厚度差异无显著性（P>0.05）;与对照组相比,冷光美白组、美白剂组、冷光照射组釉质表面生物膜中活菌百分比显著降低（P<0.001）。结论:冷光美白可抑制釉质表面混合细菌生物膜的形成,破坏生物膜的结构,降低混合细菌生物膜中活菌的数量。     

口腔纳米载银无机抗菌材料的抗菌性能

背景：纳米载银无机抗菌剂具有抗菌谱广、抗菌能力强等特点,是目前口腔无机抗菌材料研究的热点之一。 目的：研究纳米载银无机抗菌材料的抗菌性能及抗菌机制,为基础实验研究和临床应用提供参考信息。 方法：研究多种口腔纳米载银无机抗菌材料对常见病原菌如变形链球菌、白色念珠菌以及粘性放线菌等的抗菌性能,其中包括最低杀菌浓度以及抗菌率等,同时进行对比分析。并且研究纳米载银无机抗菌材料的抗菌机制,明确其优点与不足。 结果与结论：口腔纳米载银无机抗菌材料具有较广的抗菌谱,对变形链球菌、乳酸杆菌、粘性放线菌、白色念珠菌、牙龈卟啉单胞菌、金黄色葡萄球菌以及大肠埃希菌等均具有较强的抗菌性能,最低杀菌浓度较低,而抗菌率较高。但是同一纳米载银无机抗菌材料对不同的病原菌,其最低杀菌浓度不同,抗菌率也不同,而不同的纳米载银无机抗菌材料对同一病原菌的最低杀菌浓度也不相同,抗菌率也不同。     

老年人根面菌斑内氏放线菌临床分离株基因型多样性分析

目的分析老年人根面菌斑中内氏放线菌临床株的基因型多样性,探讨内氏放线菌基因型与根面龋的关系。方法选择老年根面龋患者20例设为根面龋组,无根面龋老年人20例设为无龋组。根面龋组以暴露的无龋根面和根面龋损部位为取样位点,无龋组以暴露的根面为取样位点,刮取菌斑进行临床株的分离鉴定,并利用基因外重复回文序列聚合酶链反应（REP-PCR）分析内氏放线菌基因型的多样性。结果2组共分离出内氏放线菌299株,选择156株进行REP-PCR分析,分离出61个不同的基因型。根面龋组无龋根面分离的57株内氏放线菌有25个基因型,根面龋损部位分离的34株有25个基因型,无龋组分离的65株有26个基因型：内氏放线菌基因型存在多样性。单个取样位点的基因型数目存在差异（P<0.05）。结论多种基因型的内氏放线菌参与了根面龋的发生。     

Actinomyces viscosus and Actinomyces naeslundii agglutinins in human saliva

Abstract – The objectives were to determine the degree of Actinomyces agglutinating activity in human saliva and to begin characterizing the agglutination mechanism. Agglutination titres of whole saliva collected from adults and 6-yr-old children were compared. Titres for A. naeslundii were always higher than for A. viscosus. The mean A. naeslundii titre for the adults’ and children's samples were equivalent. The children had a slightly lower mean titre than the adults for A. viscosus. No correlation was found between IgA concentration and agglutination titre. Agglutinating activity was partially impaired by incubation with anti-IgA serum. Activity in submandibular/sublingual saliva was resistant to heat at 56°C but sensitive to boiling. Boiling the bacteria had no effect. In sugar inhibition tests, only galactosides (β-Gal) and glucosamine (for A. viscosus) affected Actinomyces agglutination but impairment was only temporary. Agglutinating activity was diminished by incubating saliva with hydroxyapatite. Thus, Actinomyces agglutinins 1) are probably distinct from IgA but may complex with it; 2) may include both β-Gal and higher affinity sites; and 3) may contribute to salivary pellicle.     

Surface ultrastructure of some oral bacteria

Abstract – Adhesion of Streptococcus sanguis, Fusobacterium nucleatum and an Actinomyces sp . to enamel and epon and their interspecies cohesion was studied with scanning and transmission electron microscopy. For adhesion studies enamel or epon was coated with salivary macromolecules and then cells of S. sanguis and in some experiments also with F. nucleatum or Actinomyces sp . Cells of S. sanguis were seen scattered over the surface of a thin "pellicle" that was heavily stained, and F. nucleatum and Actinomyces sp . adhered to S. sanguis or directly to the "pellicle". For studies of cohesion S. sanguis was brought to cohere with F. nucleatum or Actinomyces sp . and then processed for transmission electron microscopy. The morphology of the cell surface structures involved was studied in negatively stained preparations or in thin sections of material treated with ruthenium red or poststained with uranyl and lead salts, phosphotungstic acid or periodic acid-thiocarbohydrazide-osmium tetroxide. S. sanguis demonstrated a fuzzy coat of fimbriae that seemed to unfold in areas of contact with other cells, while cells of F. nucleatum had 6–10 polar pilus-like fimbriae, which appeared to be instrumental in cohesion, as did a dense coat of long, slender fimbriae that covered cells of Actinomyces sp .     

Direct detection of cell surface interactive forces of sessile, fimbriated and non-fimbriated Actinomyces spp. using atomic force microscopy

Actinomyces species are predominant early colonizers of the oral cavity and prime mediators of inter-bacterial adhesion and coaggregation. Previous workers have evaluated the adhesion of Actinomyces spp. by quantitative assessment of sessile, as opposed to planktonic cells attached to substrates, but did not quantify the cell surface interactive forces. Therefore we used atomic force microscopy to directly detect the interactive force between an approaching silicon tip and sessile Actinomyces spp. adhering to a substrate, at nanonewton (nN) range force levels. A total of eight strains each belonging to fimbriated and non-fimbriated Actinomyces species were employed, namely A. bovis, A. gerencseriae, A. israelii, A. meyeri, A. naeslundii genospecies 1 and 2, A. odontolyticus and A. viscosus. The sterile mica discs, used as the adhesion substrate, were immersed in mono-species bacterial suspensions for five days to obtain a thin bacterial biofilm. Interactive forces were measured using a silicon nitride cantilever attached to a Nanoscope IIIA atomic force microscope. The interactive forces between the approaching silicon nitride tip and bacterial biofilm surfaces were randomly quantified at three different locations on each cell; namely, the cell surface proper, the periphery of the cell and the substrate and, the interface between two cells. When the interactive forces at these locations of the same species were compared, significantly higher force levels at the cell-cell interface than the other two locations were noted with A. gerencseriae (P < 0.001), A. viscosus (P < 0.01) and A. israelii (P < 0.05). When the interactive forces of different Actinomyces spp. at an identical location were compared, fimbriated A. naeslundii genospecies 2 showed the greatest interactive force at the cell surface proper (-32.6 +/- 8.7 nN, P < 0.01). A. naeslundii genospecies 1, 2 and A. viscosus demonstrated greater interactive force at the cell-mica periphery than the other five species (P < 0.05); A. viscosus (-34.6 +/- 10.5 nN) displayed greater interactive force at the cell-cell interface than the others (P < 0.01), except for A. gerencseriae (P > 0.05). These data indicate that fimbriated Actinomyces spp., including A. naeslundii genospecies 1, 2 and A. viscosus exert higher cell surface interactive forces than those devoid of fimbriae and, such variable force levels may modulate their adhesion and coaggregation during biofilm formation.     

Efficacy and mechanisms of non-antibacterial, chemical plaque control by dentifrices--an in vitro study

OBJECTIVES: The provision of antiplaque benefits to dentifrices assists patients in improving hygiene and reducing susceptibility to gingivitis and caries. Chemical plaque control involves different mechanisms and is mostly associated with antibacterial effects, but also includes effects on pellicle surface chemistry to improve cleansing or discourage renewed plaque formation. It is the aim of this paper to analyze in vitro detachment of co-aggregating oral actinomyces and streptococci from pellicle surfaces by dentifrice supernates and to study subsequent de novo streptococcal deposition. METHODS: Detachment by dentifrices of a co-adhering bacterial pair was studied in the parallel plate flow chamber on a 16 h pellicle coated surface. After detachment by perfusing the chamber with a dentifrice, re-deposition was initiated by flowing with a fresh streptococcal suspension. The dentifrices included both a regular, SLS-fluoride based formulation as well a pyrophosphate, anticalculus and antimicrobial formulations. RESULTS: All dentifrice supernates containing SLS were effective in detaching co-adhering bacteria from pellicles surfaces, except in combination with SnF(2). When hexametaphosphate was added immediate detachment was relatively low, but continued even during re-deposition. The re-deposition of streptococci after detachment by other, NaF containing dentifrices involved relatively few large aggregates, presumably because fluoride was able to block bi-dentate calcium binding sites on the bacterial cell surfaces, mediating co-adhesion. When pyrophosphate was present in addition to NaF, re-deposition involved significantly more large aggregates, likely because pyrophosphate served as a bi-dentate bridge between calcium bound on the bacterial cell surfaces. CONCLUSION: Commercially available dentifrice formulations differ in their ability to stimulate bacterial detachment from pellicles and dependent on their composition yield the formation of large co-adhering aggregates of actinomyces and streptococci in de novo deposition.