This study was designed to observe the effects of various concentration of polyacrylic acid containing different concentration of sulfate ion on the crystal formation on the enamel surface.
Experimental crystal growth solutions were made of 10/, 20% 30%, and 40% polyacrylic acid(molecnlar weight, 5,000) solutions which containing O.1M, 0.2M, 0.3M, 0.5M, and LOM sulfate ion respectively. The extracted human first bicuspid enamel surface was contacted for 60 seconds with these solutions, washed for 15 seconds, dried, and then the crystal topography on the enamel surface was observed under the scanning electron microscope. The crystal topography were evaluated on the SEM photographs by degree of crystal coverage, crystal length, and consistency of crystal morphology, and conclusions were as the follows.
1. Polyacrylic acid. solution etched slightly the enamel surface, and the difference of etching effect by its concentration was not observed.
2. The effect of concentration of polyacrylic acid on the crystal formation was less, e?.:pecially that of 20% - 40% polyacrylic? acid was almost not different.
3. Concentration of the sulfate´ ion was a- determinant factor in precipitating crystals on the enamel. The experimental crystal growth solutions containing 0.1 M sulfate ion did not make crystal formation but those containing over 0.2 M sulfate ion did
4. The degree of crystal coverage showed a tendency to increase and then decrease according to the concentration of sulfate ion in the 20% - 40% polyacrylic acid. The experimental solutions containing 0.5 M sulfate ion showed the peak of degree of crystal coverage.
5. The crystal length showed a tendency to decrease by increment of sulfate ion in the polyacrylic acid solution.
6. There was a tendency to increase the frequency of random arragement of short crystals when increasing the concentration of sulfate ion in the polyacrylic acid solution. The lower concentration of sulfate ion in the polyacrylic acid solutions tended to make spherulitic arrangement of crystals, the higher concentration of sulfate ion, the more random arrangement of crystals. The experimental solutions containing 0.5M sulfate ion showed more spherulitic
arrangement than random arrangement of crystals.
7. The best one of these experimental crystal growth solutions was 30% polyacrylic acid solution containing 0.5M sulfate ion.
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