Fluoride release from glass-ionomer and compomer restorative materials: 6-month data

To investigate the daily fluoride release of two glass ionomers (Ketac-Fil and ChemFil Superior) and two compomers (Compoglass and Dyract Restorative) over 6 months.

A pilot study evaluated the time taken for sample solutions to equilibrate to establish an appropriate time period for sample solution storage between fluoride ion measurements. In the main study storage water replacement and fluoride ion determination was made daily using a specific ion electrode, TISAB buffer and standard solutions for calibration.

Equilibration of fluoride concentration in aqueous solution occurred in under 48 h for all materials. Total fluoride released (microgram mm-2) after 6 months by Ketac-Fil (30.6, s.d. 4.9) was significantly greater than ChemFil Superior (12.7, s.d. 2.5), Compoglass (10.4, s.d. 1.0) and Dyract Restorative (7.7, s.d. 1.7) (P < 0.05). Daily fluoride release at 24 h and 10 days was significantly higher for the glass ionomers than the compomers (P < 0.05). After 40 days the daily fluoride release (microgram mm-2) from ChemFil Superior (0.05, s.d. 0.01) was not significantly different from Compoglass (0.04, s.d. 0.01) and Dyract Restorative (0.03, s.d. 0.00) (P > 0.05). Daily fluoride release from Ketac-Fil remains significantly higher than the compomers at 3 and 6 months (P < 0.05).

Specimens stored in water equilibrate rapidly, suggesting the rate at which storage water is changed may alter the relative fluoride release rates of materials. This important fact is often overlooked. Fluoride release from the glass ionomers is initially higher than for the compomers. Fluoride release from glass ionomers falls rapidly to approach levels released by compomers. Compomers produce no initial burst of fluoride and levels of release remain relatively constant.