Abstract
Change in compressive and tensile strengths, dimensional and weight change of glass ionomer cement("Chembond" and "Fuji-ionomer Type I") were observed in regards to the passage of time. Also, the surface of hardened cement was examined with SEM by means of replication technique and compared with polycarboxylate and zinc phosphate cements. Following results were obtained:
1. In respect to the compressive strength, those of "Fuji-ionomer" were largest regardless to the period of passed time. However, those of "Chembond" were similar to a zinc phosphate cement.
2. On the other hand, tensile strength of a polycarboxylate cement was the largest regardless to the period of passed time, followed by "Fuji-ionomer, ""Chembond" and a zinc phosphate cement in this order.
3. Bond strength of a polycarboxylate cement asw largest, followed by"Fuji-ionomer, ""Chembond" and a zinc phosphate cement. Although those tendencies were apparent up to 30 days, after this, similar bond strengths were obtained regardless to the type of cements.
4. As to the dimensional change under dry condition, similar contraction were observed with glass ionomer cements as a polycarboxylate cement.However, under wet condition, only glass ionomer cements indicated expansion.5.Decrease in weight of glass ionomer cements were intermediate between polycarboxylate and zinc phosphate cements under the dry condition.Contrastingly, apparent increase in weight was observed with glass ionomer cements.
6. From the SEM observation, it has become apparent that small cracks, appeared on the surface of glass ionomer cements, became more greater in width and depth after 1 day placement under dry condition.But, these cracks disappeared following 1 day placement under wet condition.
