title: The kinetics of water loss from zinc phosphate and zinc polycarboxylate dental cements.
abstract: The water desorption behaviour of three different zinc oxide dental cements (two polycarboxylates, one phosphate) has been studied in detail. Disc-shaped specimens of each material were prepared and allowed to lose water by being subjected to a low humidity desiccating atmosphere over concentrated sulfuric acid. In all three cements, water loss was found to follow Fick's second law for at least 6 h (until M(t)/M(infinity) values were around 0.5), with diffusion coefficients ranging from 6.03 x 10(-8 )cm(2 )s(-1) (for the zinc phosphate) to 2.056 x 10(-7 )cm(2 )s(-1) (for one of the zinc polycarboxylates, Poly F Plus). Equilibration times for desorption were of the order of 8 weeks, and equilibrium water losses ranged from 7.1% for zinc phosphate to 16.9% and 17.4% for the two zinc polycarboxylates.
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Greenwich, Medway Campus, Chatham, Kent, ME4 4TB, UK, J.W.Nicholson@gre.ac.uk.
authors.forename: John W
authors.initials: JW
authors.lastname: Nicholson
authors.forename: Beata
authors.initials: B
authors.lastname: Czarnecka
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry; D003738:Dental Cements / Q000737:chemistry*; D004058:Diffusion; D006813:Humidity; D007700:Kinetics; D008422:Materials Testing; D015233:Models, Statistical; D010710:Phosphates / Q000737:chemistry*; D011076:Polycarboxylate Cement / Q000737:chemistry*; D013464:Sulfuric Acids / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D002264:Carboxylic Acids; D003738:Dental Cements; D010710:Phosphates; D011076:Polycarboxylate Cement; D013464:Sulfuric Acids; D017967:Zinc Compounds; D014867:Water; C043952:zinc phosphate; C005506:polycarbonate; D015032:Zinc; C033158:sulfuric acid