Recharge and Increase in Hardness of GIC with Bioavailable Calcium

Objectives: The properties and resistance of glass ionomer cement (GIC) may be improved by loading with bioavailable calcium as casein phosphopeptide amorphous calcium phosphate (CPP-ACP). The aim of this study was to assess the effect of CPP-ACP/F recharging on microhardness and ion release of the GIC Fuji VII.
Methods: Eighty blocks of GIC Fuji VII (Fuji Triage) and Fuji VII EP containing 3% CPP-ACP were subjected to an acidic solution over a three day period. The blocks measured 3 x 6 x 6 mm³ and were lapped with wet 600-grit paper to provide a standardized surface finish. Each block was placed in 5 ml of acid (pH 2 or 5) and every 12 hours half the blocks were treated with 2 ml of MI Paste (CPP-ACP/F) solution (1 in 5 dilution) for 2 min. The other half was treated with a placebo paste solution with the same dilution and for the same time. After each 2 min treatment the blocks were rinsed with distilled water and placed back into the acid solution. Ca, Pi and F levels in the acid solutions were measured using atomic absorption spectrophotometry (Ca), colorimetry (Pi) and ion specific electrode (F). Vickers hardness measurements were determined using a Microhardness Tester. Single factor ANOVA was used to analyse the results with a Bonferroni-Holm correction for multiple comparisons.
Results: Significantly (p < 0.001) higher calcium (1.52 µmol), inorganic phosphate (1.22 µmol) and fluoride (22.53 µmol) ion release and higher surface hardness (26.1%) was observed in the GIC’s treated with the CPP-ACP/F paste after 3 days in acid. Fuji VII EP released higher levels than Fuji VII.
Conclusions: Topical treatment of GIC with CPP-ACP/F paste recharged surface hardness and ion release which may help improve properties and resistance to degradation as well as improve ion release for caries control.