The kinetics of water loss from zinc phosphate and zinc polycarboxylate dental cements.
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.
Nicholson
John W
JW
Department of Chemical and Pharmaceutical Sciences, University of Greenwich, Medway Campus, Chatham, Kent, ME4 4TB, UK, J.W.Nicholson@gre.ac.uk.
Czarnecka
Beata
B
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*
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