ABSTRACT
Objective To investigate the influence of pullulan molecular weight and spacer length on the properties of modified pullulan carriers including morphologies,sizes and in vitro release behaviours of drug-loading carriers.Methods Using cholesterol as hydrophobic ligand,succinic anhydride and 1,6-hexyldiisocyanate as spacers,hydrophobic modified pullulans with different molecular weights were prepared.Self-assembled nanoparticles were then formed in the aqueous solution,and drug-loaded nanoparticles were prepared by dialysis method.The influence of pullulan molecular weight and spacer length on the loading-content,morphologies and in vitro release behaviours of drug-loading nanoparticles were then investigated in detail.Results Self-assembled nanoparticles could be formed by the cholesterol-modified pullulan,and doxorubicin and mitoxantrone could be loaded into cholesterol-modified pullulan to form nanoparticles.Pullulan molecular weight and spacer length show influences on sizes,morphologies and stabilities of pullulan nanoparticles and drug-loaded nanocarriers.Conclusions Before drug loading,nanoparticles with larger moleculare weight and shorter spacer length are more stable in solution,while after drug loading,the influences of these two factors on the nanoparticles are drug-type depended.
ABSTRACT
Objective:To evaluate the effects of different ultrasonic retroprep tips on the root-end preparation in cadavers.Methods:34 anterior teeth in situ in maxillary and mandibular jaws in cadavers were chosen and the root-end of 3 mm of all teeth was exposed. Root canal was prepared and filled with gutta-purcha in all teeth,3 mm of the root end was cut off.The teeth were divided into 2 treat-ment groups(n=1 5),and 1 control group(n=4).The root-end preparation was made using ultrasonic diamond tip and stainless steel tip respectively to 3 mm depth.The teeth in control group were not treated.Microcracks,marginal integrity and gutta-percha clearance were observated under SEM.Results:Diamond ultrasonic tips provoked a smaller number of cracks(P=0.059)and destroy of margin-al integrity(P=0.269)than stainless steel tips.Less gutta-percha clearance was produced by stainless steel tip than that by diamond ultrasonic tip(P=0.006).Conclusion:Diamond ultrasonic tip is more suitable for root-end preparation.