The study on the adhesive durability of dental restorative composite resins by new testing mthod

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The adhesive shear strength and the adhesive durability of chemically cured type (CCT) and light cured type (LCT) of dental restorative composite resins were comparatively investigated. The test specimen cut from different locations on bovine tooth, cylindrical cavities 5mm in diameter were prepared and then filled with each composite resin. The test for adhesive shear strength was done using the push-out shear test method developed by the authors. The adhesive durability test of which the test specimen was the cavity with bottom was done by pulsating fatigue test in the conditions of load amplitudes of 50N and 100N,frequency of 1Hz and cycles of one handred thousand times, and then the adhesive durability was evaluated by measuring a marginal leakage. The following are major results :1. Push-out shear test In test specimens of all types, adhesive strengths of LCT resin were higher than those of CCT resin. Adhesive strength of Types I and II (dentin) were similar, consequently, it is difficult to positively confirm the anchoring effect of dentinal tubules by resin tags. And their strengths were much lower than those Type IV (enamel). Type III (enamel/dentin) showed an intermediate value between the strength of Type I and IV.In the test specimen of Type III,debonding was observed on the adhesive interface of the dentin layr by SEM photo.2. Adhesive durability test In test specimen for enamel/dentin after pulsating test the marginal leakage was verified, threfore, the repeated loading seemed to cause the debonding at a margin part. In adhesive interface of the composite resin/enamel the debonding was also observed from SEM photo.Such the shear test methods appear to be useful in evaluting the adhesive properties of composite resin for dental use.