Stoichiometry oftheLeaching Process ofFluoride-contain ing Aluminosilicate Glass-ionomer Glasses

Dental glass-ionomer cements(GIC) setbyan acid-base reaction between apolyalkenoic acidandanion- leachable glass. Theexact relationship between theglass composition andthesetting andfinal properties ofGICis notyetfully elucidated. Aspartofasystematic study ofthis relationship, we studied theleaching stoichiometry of glasses usedincommercial formulations tocorrelate the glass composition withitsleaching properties. Theleaching experiments wereperformed inacetic acidsolutions atpH= 3.4bymeansofapH-stat method. After predetermined time intervals, thesuspension wasfiltered andthefiltrate was analyzed fortheglass constituents. Theusefulness ofthe pH-stat methodforthedetermination ofglass reactivity was corroborated. Thedeviation oftheleaching stoichiometry withrespect tothepureglass stoichiometry decreased with increasing relative content ofmono-andbivalent glass net- workdwellers andmodifiers. Indications werefoundthat thelatter canbeleached outindependently andpreferen- tially, whiletheleaching ofnetwork dwellers iscoupled withthealuminum release. TheFcontent aswellasthe reactivity oftheglass affect theamountoffluoride available forrelease fromasetGIC.Itcouldbeconcluded that the leaching stoichiometry ofGICglasses canbecorrelated with their absolute andrelative composition.