Aluminium is a major constituent of glass ionomer cements. During mixi
ng and setting aluminium is released from the glass into the polyalkeo
nic acid solution. Part of this aluminium may not combine with the pol
yalkeonic acid, but may be released from the cement. The aluminium rel
ease from auto-cured and light-cured glass ionomer cements during earl
y water exposure was studied. The former cements released more alumini
um than the latter. Scanning electron microscopy (SEM) showed extensiv
e loss of polymer matrix for the cements with the highest aluminium re
lease. Insufficient curing of light-cured cements also resulted in los
s of matrix. It is suggested that the considerable release of aluminiu
m from glass ionomer cements during early water exposure may explain t
he reported lack of mineralization of predentin in the pulp beneath gl
ass ionomer cements. This would correspond to the inhibiting effect of
aluminium on bone mineralization.