The purpose of this study was to synthesize the experimental restorative glass ionomer cement by change of glass component and fusing temperature. Mixtures of Al₂O₃, SiO₂, CaF₂, NaF, AlPO₄and SrCO₃were fused in recrystallized alumina crucibles. Initially 6 mixtures were fused at 3 different temperatures (1050℃, 1200℃, and 1350℃), but 17 groups (exception of GI-6C) were tested. The glasses were ground, and the fraction which passed through a 44㎛ sieve was collected. The glass powders were analyzed by a differential thermal analyzer and a x-ray powder diffractometer. A chemical-cured glass ionomer cement (FI-A) and a light-cured glass ionomer cement (FI-B) were used as control group.
The powder/liquid ratio for cement formation was 2.3g/0.8g. Compressive strength of specimens was measured by a Instron universal testing machine. Surface hardness of specimens was evaluated by Vickers hardness tester, and fluoride ion release from specimens was estimated by the fluoride ion electrode and standard solutions. Solubility of specimens in 0.1 M lactic acid solution was also measured.
From the experiment, the following results were obtained.
1. Compressive strength, surface hardness, and fluoride release of experimental groups which were fused at 1050℃ were greater than those of the groups fused at 1350℃. Experimental groups which were fused at 1350℃ however, exhibited the lowest solubility in lactic acid solution.
2. GI-1 group base cements showed better physical properties than the other groups. Especially, the results showed that GI-1B base cement was comparable in physical properties to Fuji Ⅱ glass ionomer cement except for short working time.
3. It was observed that SrCO₃would act as a radio-opacifier in GI-2, GI-3, GI-5 and GI-6 base cements.
4. GI-3A and GA-6B groups were unsuitable for clinical use since it base cements dissolved in lactic acid solution and exhibited a delayed setting reacting respectively. GI-6A Group was unsuitable since it base cement dissolved in lactic acid as well as exhibited a delayed setting reaction.
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