Structure of dental glass-ionomer cements by confocal fluorescence microscopy and stereomicroscopy

The microstructure of four cements, setting by different mechanisms (acid-b ase, dual cure, triple cure), was studied. The porosity of unpolymerized ma terials was detected by stereo microscopy. After polymerization and storage in water or lactic acid solution, the porosity, filler distribution and ge l layer, which was formed at the filler/matrix interface of polymerized mat erials, were examined by confocal laser microscopy. For this purpose, the s pecimens were treated with fluorescent dye solution before the test. The re sults showed that hydrolytic degradation (pH 7) mainly involved the resin m atrix, and the acid erosion (pH 3.5) involved the gel layer too. As regards the filler, materials with different setting mechanism released the glass particles in different times. The loss of the filler particles occurred qui cker in acid-base setting cements, and slower in triple-cured material. (C) 2001 Elsevier Science Ltd. All rights reserved.