Chitosan [10] which is produced commercially by de-acetylation of chitin is a natural polysaccharide composed of randomly distributed β-1, 4-linked D-glucosamine and N-acetyl α-glucosamine.Chitosan is non-toxic, biocompatible, bio-degradable and has muco-adhesive properties and as a result became widely used in the pharmaceutical field as a carrier system for drugs, hormones, proteins, enzymes and genes [11][12][13][14]. Chitosan is positively charged in acid medium because the amino groups become protonated
The aims of this study were to synthesize highly positively charged chitosan nanoparticles (Ch-Np) using the electrospraying technique, and to test their antimicrobial activity against endodontic pathogens, and cytotoxicity against fibroblast cells. Ch-Np were synthesized from low molecular weight chitosan (LMW-Ch) using the electrospraying technique, and characterized. The antimicrobial activity was evaluated against Streptococcus mutans, Enterococcus faecalis, and Candida albicans in their planktonic state using a Time-Kill Test performed by using broth micro-dilution technique, and against biofilm biomass using a microtiter plate biofilm assay. The cytotoxicity was evaluated using Balb/c 3T3 fibroblast cells with the standard MTT assay. Electrospraying of LMW-Ch produced Ch-Np with an average size of 200 nm, and a surface charge of 51.7 mV. Ch-Np completely eradicated S. mutans and E. faecalis in the planktonic state and showed fungistatic activity against C. albicans. Furthermore, it significantly reduced the biofilm biomass for all the tested microbial species [S. mutans (p = 0.006), E. faecalis (p < 0.0001), and C. albicans (p = 0.004)]. When tested for cytotoxicity using 3T3 cells, Ch-Np showed no cytotoxicity. In conclusion, the highly positively charged, colloidal dispersion of Ch-Np are effective as a biocompatible endodontic antimicrobial agent.
The acid-etch technique of SBMP produced higher bond strength and no microleakage when compared with the self-etching/self-priming 'non-rinse technique' of NRC with PBNT. Thus it can only be speculated that SBMP should be the superior in the clinical situation.
Artificial saliva as an in vitro aging medium may be an effective method of simulating the clinical degradation of resin composite restorations. The composition and desirable properties of artificial saliva are not yet standardised. Incorporation of oral bacteria may more closely approximate the intra-oral effect of saliva on composite restorations. Surface deterioration on an old broken restoration repaired with fresh composite may result in a weak adhesive interface, measureable, in vitro, by a shear bond strength test. To evaluate whether artificially aged composite affects the shear bond strength of the adhesive interface with fresh composite. A silicone mould was used to fabricate 240 composite cylinders. 120 were aged in a solution of artificial saliva for 28 days. The remainder served as controls. The specimens were divided into seven groups of twenty, each group being subjected to a different repair protocol. Shear bond strength testing was then carried out on the repaired composite blocks. Aging in artificial saliva resulted in a reduction of 15.04% to 21.1% in shear bond strengths compared with un-aged composite. Composite samples aged in artificial saliva had a significantly weaker repair interface compared with nonaged samples.
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