Stoichiometry of the leaching process of fluoride-containing aluminosilicate glass-ionomer glasses

Dental glass-ionomer cements (GIC) set by an acid-base reaction between a p olyalkenoic acid and an ion-leachable glass. The exact relationship between the glass composition and the setting and final properties of GIC is not y et fully elucidated. As part of a systematic study of this relationship, we studied the leaching stoichiometry of glasses used in commercial formulati ons to correlate the glass composition with its leaching properties. The le aching experiments were performed in acetic acid solutions at pH = 3.4 by m eans of a pH-stat method. After predetermined time intervals, the suspensio n was filtered and the filtrate was analyzed for the glass constituents. Th e usefulness of the pH-stat method for the determination of glass reactivit y was corroborated. The deviation of the leaching stoichiometry with respec t to the pure glass stoichiometry decreased with increasing relative conten t of mono- and bivalent glass network dwellers and modifiers. Indications w ere found that the latter can be leached out independently and preferential ly, while the leaching of network dwellers is coupled with the aluminum rel ease. The F content as well as the reactivity of the glass affect the amoun t of fluoride available for release from a set GIG. It could be concluded t hat the leaching stoichiometry of GIC glasses can be correlated with their absolute and relative composition.