Pawluk, Katarzyna Malgorzata (2011) Release of antimicrobial compounds from glass-ionomer dental cements. PhD thesis, University of Greenwich.

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Abstract

This thesis reports a study of the possibility of using conventional glass-ionomer cements (GICs) as matrices for release of antimicrobial compounds. Sodium fusidate, cetyl pyridinium chloride (CPC), benzalkonium chloride (BACH), triclosan and triclosan/zinc citrate at concentrations ranging from 1% to 5% by weight were added into Fuji IX and Chemflex cements. Disc-diffusion studies showed antimicrobial effect against Streptococcus mutans. Inhibition zones were proportional to the amount of added bactericide, CPC and BACH showed highest antibacterial activity. The release of the bactericides into water was studied for time intervals up to seven weeks. The amount of additive released varied from 0.61% to 5.00% of total bactericide added and samples containing more antimicrobial agent gave higher release into the surrounding water. The release was shown to be diffusion based for the first 2-4 weeks. Compressive strength and surface hardness of reformulated materials decreased in comparison with the control specimens. Addition of bactericides also decreased the amount of fluoride released. 27Al MAS-NMR showed that aluminium switches its coordination number from four, Al (IV), in the glass phase to six, Al (VI), in the cement matrix and addition of antimicrobial agents reduced the rate of this change. Incorporation of additives also prolonged the working time. By contrast, water loss properties were not affected by additives. The overall conclusion is that the presence of additives affects the setting and maturation reactions of GICs. These results can be interpreted as showing that the additives having an effect on the conformation of the poly (acrylic acid) (PAA) component in solution. Changes in the conformation of the PAA also influence the release of key ions from the glass (Al3+, Ca2+, F- and Na+). Alteration in the balance of these ions, especially Al3+, would result in slower cross-linking processes and lower cross-link density matrix. Additionally, adsorption properties of surfactants to GI aluminosilicate glass particles can also lead to reduction in the number of available active sites on the glass which can react with PAA. The reduction in available active sites on the glass will result in a lower bonding density and thus a weaker matrix. All above will leads to the observed changes in mechanical properties, working kinetics, F- release and kinetics of conversion of Al (IV) to Al (VI).

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	glass-ionomer cement, dental cement, chemical compounds,
Subjects:	Q Science > QD Chemistry
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science > School of Science (SCI)
Last Modified:	17 Oct 2016 09:12
URI:	http://gala.gre.ac.uk/id/eprint/9813

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