Fluoride Uptake by the Glass Component of Glass Ionomer Cement
Objective: F ion has an established effect on silicate glasses; in acid
conditions, etching and in neutral conditions, being taken up by both soda and
borosilicate glass. Glass ionomer cement (GIC) takes up F ion in large
quantities from dilute neutral F ion solutions. It has proved difficult to
precisely locate the F in the cement. This study aims to assess the potential
role of the alumino-silicate glass component. Method: Three glasses previously
used in cement uptake studies were chosen. LG30 (A) contained Al, Ca, P, O, &
Si. LG26 (B) also contained F and AH2(C) also F and Na. Samples of glass were
tested after comminution (M) and after washing with acetic acid to represent
cement formation (N). Samples [~130mg] were immersed in 10ml KF solution
containing 900ppm F in plastic containers at 37 C for 2 days(n=5). Five 10mL
samples of KF solution were similarly stored as controls. F concentrations of
the solutions were measured using Ion Selective Electrode with TISAB
decomplexant. Results: Uptake is (Control - Test) in µmol F per g glass
(s.d.). Previously reported uptake by GICs [containing 73% glass] made from A and C
are 161 and 378 µmol/g respectively.
AM BM CM AN BN CN
56.0(16.3) 35.2(17.2) 16.7(31.4) 285(41) 431(42) 286(50)
Statistical analysis (Wilcoxon) shows that F uptake for N is significantly
greater than M for all three glasses (p=0.01). The only inter-material
difference is BN>AN & CN (p=0.01).
Conclusion: Uptake of F by acid treated glass is of similar magnitude to that
shown by cement made from these glasses. The depleted zone surrounding the glass
particles could accommodate an appreciable amount of the F taken up by GIC