非水溶性葡聚糖水解酶在控制人牙菌斑形成中的作用

本研究通过实验观察,证实非水溶性葡聚糖水解酶(insoluble glucan hydrolase)能降解非水溶性葡聚糖粘附物中多糖成分,松散牙菌斑结构,且对口腔粘膜无刺激作用及不良影响,能显著抑制人体口腔内牙菌斑形成。     

Coaggregation profiles of the microflora from root surface caries lesions

Bacterial coaggregation reactions between different species and the auto aggregation of the same species are associated with the initiation and development of dental plaque and biofilms. As no such data is available on isolates from root caries lesions, we evaluated, by a visual, semi-quantitative scoring system and a spectrophotometric, quantitative assay, the coaggregation of 22 different wild-type microbial species comprising ten bacterial genera and a single Candida spp. The quantitative coaggregation assay we used proved to be a more sensitive method than the semi-quantitative, visual evaluation as the results yielded the percent coaggregation. Fusobacterium nucleatum, Lactobacillus acidophilus, Streptococcus bovis II/2 and Gemella morbillorum were observed having higher degrees of autoaggregation than the other examined strains. Significant levels of inter-species coaggregation was seen between: (1) Actinomyces spp. and Veillonella spp.; (2) Actinomyces israelii and Peptostreptococcus prevotii; (3) Campylobacter gracilis and Actinomyces spp.; (4) Prevotella intermedia and nine different species; and (5) Fusobacterium nucleatum and six other species. The single Candida albicans isolate did not coaggregate to a significant extent with any of the 21 bacterial isolates studied. Scanning electron microscopy observation of the coaggregation interactions between bacterial pairs having strong coaggregation reactions revealed varying adhesive patterns. Our findings on coaggregation amongst these isolates imply existence of multiple interactions between the coaggregation-inducing bacterial species in root caries. In particular, Actinomyces spp., Veillonella spp., Prevotella spp. and Fusobacterium spp. appear to play a significant role in this context.     

口腔中生物膜分散机制的研究进展

细菌生物膜是细菌在介质表面黏附生存的细菌群体,生物膜菌落的形成使得细菌更容易适应周围环境。在生物膜发展的最后一个阶段,细菌从生物膜菌落中分离出来然后分散到周围环境中,这个过程称为生物膜的分散。生物膜分散由酶促降解、种植传播、鼠李糖脂的产生等机制介导,并受到自身以及外界多种物理化学因素等调控。口腔中生物膜分散一方面使细菌得以从病灶扩散到新的部位导致感染性疾病的加重,而另一方面,分散开的细菌由于失去生物膜的保护而变得容易去除和杀灭。通过对生物膜分散机制的研究,找到促进生物膜分散的途径,解决治疗难治性细菌感染的难题,是近年来的研究热点。本文就生物膜形成发展、分散机制、调控和临床意义做一综述。     

Influence of orthodontic brackets design and surface properties on the cariogenic Streptococcus mutans adhesion

ObjectiveTo compare the surface properties of self-ligating metallic (SLM), ceramic esthetic, and conventional metallic (CM) brackets, and evaluate the adhesion of Streptococcus mutans biofilms to their surface, attempting to interpret the correlation between bracket type and enamel demineralization from a microbiological perspective.Materials and methodsTwenty-two brackets of each group were used. The brackets’ surface roughness was defined and the bacterial adhesion was performed using the strain S. mutans ATCC25175 with 8 h or 24 h of incubation time. The total bacterial adhesion (TBA) of biofilms was assessed using optical density (OD) methodology. To quantify bacteria viability (BV), the colony forming units (CFU) were counted. A scanning electron microscopy (SEM) observation of biofilms was also performed. Results: Ceramic brackets exhibited significantly higher roughness (0.304) compared to CM (0.090) and SLM (0.067) ones (C > CM = SLM). The data obtained with the TBA and BV tests showed that S. mutans biofilm formed on bracket groups exhibited similar results for both incubation periods. From the SEM images it is possible to observe that biofilm structure formed for 24 h was denser than that for 8 h of incubation with significantly more aggregates and cells for three groups.ConclusionThis in vitro study suggests that despite the higher surface roughness of ceramic brackets, this alone does not influence the adhesion of the S. mutans biofilms.Clinical relevanceFrom a microbiological perspective, the bracket's design may be more relevant than its surface roughness with respect to the adhesion of cariogenic bacteria biofilm with potential risk to dental enamel integrity.     

A comprehensive in vitro comparison of the biological and physicochemical properties of bioactive root canal sealers

Clinical Oral Investigations - To evaluate the biological and physicochemical features of bioactive root canal sealers. Human periodontal ligament fibroblasts (hPDLF) and human osteoblasts (hOB)...     

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.     

不同fimA基因型牙龈卟啉单胞菌黏附和侵入口腔上皮细胞能力的比较

目的 通过比较临床分离的不同fimA型牙龈卟啉单胞菌(Porphyromonas gingivalis,Pg)菌株黏附和侵入KB细胞的能力,探讨不同fimA基因型Pg菌株之间致病力差异的原因.方法 应用培养法和抗生素保护法测定不同fimA型Pg菌株黏附和侵入KB细胞的能力,扫描电镜观察不同fimA型Pg对KB细胞的黏附情况.结果 所有菌株均可黏附和侵入KB细胞,黏附率为0.523%～37.125%,侵入率为0.017%～3.750%;各fimA型Pg菌株之间黏附和侵入KB细胞的能力差异无统计学意义(P>0.05);各株Pg之间、4株Ⅱ型菌株之间、5株Ⅳ型菌株之间,黏附和侵入KB细胞的能力差异有统计学意义(P<0.01).结论 Pg的fimA型与其对KB细胞的黏附和侵入能力无相关性,提示可能存在其他影响不同fimA型Pg致病力差异的因子.     

The effects of titanium nitride-coating on the topographic and biological features of TPS implant surfaces

Objectives

Titanium nitride (TiN) coating has been proposed as an adjunctive surface treatment aimed to increase the physico-mechanical and aesthetic properties of dental implants. In this study we investigated the surface characteristics of TiN-coated titanium plasma sprayed (TiN-TPS) and uncoated titanium plasma sprayed (TPS) surfaces and their biological features towards both primary human bone marrow mesenchymal stem cells (BM-MSC) and bacterial cultures.

Methods

15 mm × 1 mm TPS and TiN-TPS disks (P.H.I. s.r.l., San Vittore Olona, Milano, Italy) were topographically analysed by confocal optical profilometry. Primary human BM-MSC were obtained from healthy donors, isolated and expanded. Cells were seeded on the titanium disks and cell adhesion, proliferation, protein synthesis and osteoblastic differentiation in terms of alkaline phosphatase activity, osteocalcin synthesis and extracellular mineralization, were evaluated. Furthermore, adhesion and proliferation of Streptococcus pyogenes and Streptococcus sanguinis on both surfaces were also analysed.

Results

TiN-TPS disks showed a decreased roughness (about 50%, p < 0.05) and a decreased bacterial adhesion and proliferation compared to TPS ones. No difference (p > 0.05) in terms of BM-MSC adhesion, proliferation and osteoblastic differentiation between TPS and TiN-TPS surfaces was found.

Conclusions

TiN coating showed to modify the topographical characteristics of TPS titanium surfaces and to significantly reduce bacterial adhesion and proliferation, although maintaining their biological affinity towards bone cell precursors.     

A comparative study of physicochemical properties of AH Plus and Epiphany root canal sealants

AIM: To evaluate setting time, solubility and disintegration, flow, film thickness, and dimensional change following setting in a dual-cured resin root canal sealer Epiphany compared with an epoxy-resin-based sealer AH Plus. METHODOLOGY: The experiments were performed according to ANSI/ADA Specification 57 which tests the physicochemical properties of endodontic sealing materials. Five samples of each material were tested for each of the properties. In addition, deionized distilled water from the solubility test of Epiphany was submitted for analysis of the cations Fe, Ni, Ca, Mg, Zn, Na, and K in an atomic absorption spectrometer. Three samples were analysed. RESULTS: There were no statistical differences (P>0.05) in flow (AH Plus: 38.57 mm; Epiphany: 35.74 mm) and film thickness (AH Plus: 10.6 microm; Epiphany: 20.1 microm). The solubility (AH Plus: 0.21%; Epiphany: 3.41%) and dimensional alterations following setting (AH Plus: expansion of 1.3%; Epiphany: expansion of 8.1%) were statistically different (P<0.05). The setting times of both sealants were in accordance with ANSI/ADA requirements. CONCLUSIONS: Setting time, flow, and film thickness tests for both cements conformed to ANSI/ADA standards. Dimensional alteration test for both cements were greater than values considered acceptable by ANSI/ADA. Epiphany values regarding solubility were also greater than values considered acceptable by ANSI/ADA.     

Antibacterial,biological, and physicochemical properties of root canal sealers containing chlorhexidine-hexametaphosphate nanoparticles

ObjectiveThe aim of this study was to evaluate the influence of the incorporation of chlorhexidine-hexametaphosphate nanoparticles (CHX-HMP NPs) on antibacterial, cytotoxic and physicochemical properties of AH Plus (AH), MTA Fillapex (MTA) and Pulp Canal Sealer (PCS).MethodsThe NPs were synthesized and characterized by Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), zeta potential, Atomic Force Microscopy (AFM) and Energy-Dispersive X-ray Spectroscopy (EDS). The incorporation was made by weight, 2% and 5% of NPs. The antimicrobial activity, cytotoxicity, flow, radiopacity, setting time, solubility and pH were evaluated. The statistical analysis was performed by two-way analysis of variance test and Tukey post hoc test (P < 0.05).ResultsSEM analysis showed the tendency for CHX-HMP NPs to cluster, the effective mean diameter measured by DLS: 169.39 nm and the zeta potential: -10.18 mV. The NPs were individually measured by AFM: 22.99–52.75 nm. EDS analysis identified the presence of C, N, O, Na, P, Cl. After incorporation: The Direct Contact Test showed an increase in the antimicrobial action of AH, PCS and MTA; the sealers showed a decrease in flow and at 24 h of immersion also an increase in solubility, but did not affect the radiopacity of the samples; AH setting time increased and MTA did not reach setting under any of the conditions tested. All samples showed a decrease in pH value as the immersion time progressed.SignificanceThe incorporation of NPs can improve the antimicrobial performance of endodontic sealers without impairing other biological and physicochemical properties.