Methods: Eleven GICs with varying ratios of strontium to fluoride were prepared. Compressed HAp discs (20mm diameter, 3mm thickness, 20% nominal porosity) were used as tooth analogues. 5mm diameter holes were drilled into the HAp discs and filled with GICs. Discs without GICs and Fuji IX GIC were used as controls. SMR was used to measure the rate of demineralisation of the treated HAp discs during exposure to demineralising solutions at pH 4.0, simulating caries conditions.
Results: Increasing the fluoride in the GICs decreased the rate of demineralisation of the HAp tooth analogues in the presence of strontium. Whereas, increasing the strontium increased the rate of demineralisation of the HAp tooth analogues, even in the presence of fluoride.
Conclusions: Strontium and fluoride in GICs do not have a co-operative effect in preventing demineralisation during artificial caries-like demineralisation. Strontium may have a caries inhibitory role, but may not be released from GICs at sufficient concentration to have a caries inhibitory effect. Increasing the strontium to fluoride ratio in GICs may increase the rate of demineralisation