[Studies of dental methacrylic resin. (Part 7) Adhesive strength of fluid methacrylic resin to polymethylmethacrylates with various cross-linked density (author's transl)].

Heat-curing methacrylic resins cross-linked with three kinds of dimethacrylates, i.e. EDMA, tri-EDMA and nona-EDMA, were prepared, and the tensile adhesive strength of fluid methacrylic resin to them was examined. The results obtained were as follows. (1) To adherent resin cross-linked with EDMA, the adhesive strength of fluid resin showed the maximum at the concentration near 2 mole% and decreased with increasing the concentration. (2) To adherent resin cross-linked with tri-EDMA or nona-EDMA, the effect of the concentration of cross-linking agent on the adhesive strength was little, except that the adhesive strength to the latter adherent resin showed a steep increase in the range of lower concentration. (3) The adhesive strength did not appreciably change in the range of L/P ratio of fluid resin from 0.57 to 0.71 ml/g. (4) The adhesive strength under the wet condition decreased about 40 to 50% compared under the dry condition. (5) To cross-linked adherent resin, the adhesive strength of fluid resin was somewhat higher than that of self-curing resin under the dry condition. But, under the wet condition this difference was little. (6) Contrarily, to non-cross-linked adherent resin, the adhesive strength of fluid resin was somewhat lower than of self-curing resin. This may be because the cracks, which are occured on the surface of non-cross-linked adherent resin by contact with abundant MMA of fluid resin, work as defects to decrease the adhesive strength.