| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1987: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1986: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1985: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
We developed a new method for the evaluation of bond strength of posterior composite resin to tooth. In this method, specimens having cylindrical cavities filled with resin are used. After polymerization and curing, resin are pushed out by flat-based cylindrical punch. Bond strength thus obtaired are considered to have more close reiationships to the actual ciinic condition than those obtained by conentional shear test. We conducted several experiments and found that bond strength of resin to dentin was 1.31Mpa, and that to enamel was 5.82MPa. These values were 46% and 26%, respectively, of those obtained by shear test. We also carried out estimations and found that very large tensile stresses occur at resin/tooth interface. These tensile stresses do not occur in specimens utilized in shear test, and are considered to responsible for the reduction of bond strength noted with the proposed push-out method.
The adhesive durability of posterior composite resins under repeated compressive loads was investigated. Four types of cavities, i.e. box, box with bevel, saucer, saucer with bevel were prepared and filled with composite resins. Two filling procedures were examined, one was conventional method in which filling was done at one time, while in other method, filling was completed in two steps. Specimens were subjected to repeated compressive loads, and adhesive durability was evaluated by dye penetration test. It was found that the marginal leakages were promoted by repeated loadings. The saucer cavity showed less marginal leakage than box cavity, and bevel excellent effects on the improvement of durability of both types of cavities. Filling procedure has little effect on durability, and specimens filled by two-step method show poorer durability than specimens filled by two-step method show poorer durability than specimens filled by conventional one-step method.
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