The effect of saliva on surface hardness and water sorption of glass-ionomers and "compomers".

A study is reported in which commercial dental materials (glass-ionomers, resin-modified glass-ionomer and polyacid-modified composite resins) in the form of discs of dimensions 6 mm diameter x 1 mm thickness were prepared and exposed to natural salivas (parotid and unstimulated whole), artificial saliva and water for up to 1 year. Surface hardness was measured at various time intervals, and water sorption characteristics were determined. For all types of material, storage in artificial saliva gave specimens of lowest surface hardness by amounts that were generally significant to p<0.05, whereas no differences were found between specimens stored in water or either of the natural salivas. Water sorption characteristics were found to be unaffected by the nature of the storage medium. These results contrast with some previous findings and were not expected, given the known surface reactions between salivas and glass-ionomers, or the known enzymic degradation of composite resins. They demonstrate, however, that the current widespread practise of employing pure water for storage of specimens in laboratory studies is acceptable.