裏装材のレジンモノマー遮断性に関する研究

Abstract

Composite resins have been preferably used as the esthetic cavity restorations. However, certain irritation response of the dental pulp has often occurred in the cases restored with them. It might be accelerated by the penetration of the residual monomers from the composite resins into the pulp. Pathological studies have previously shown that the inflammatory response of the pulp can be reduced effectively by adopting the cavity liners but can not always disappear completely. The present study was designed to evaluate the ability of sevcral commercial cavity liners to block the passage of the monomers by comparing the amount of the monomer that passed into distilled water through the liner, the membrane filter and glass filter as the substitute of dentin. The monomer extracted in the water was analysed quantitatively by liquid chromatography. Three kinds of typical pure monomers were selected for the experiment : EDMA, Tri-EDMA and Bis-GMA. Zinc phosphate cement 'Elite 100' and polycarboxylate cement 'Unident' showed better abilities to block the passage of these monomers. Glass-ionomer cement 'Fuji Ionomer Type I' was slightly inferior to above two cements because of its larger disintegration behabior in the monomers. Cyanoacrylate liner 'Isobutyl cyanoacrylate' allowed Tri-EDMA to pass easily but showed a good ability to block for other two monomers. In the case of calcium hydroxide 'Dycal', much larger amount of Bis-GMA monomer passed through into the water. No blocking effect was recognized in varnish 'Copalite' on all of the monomers used even if it was lined very thick. All the liners seemed to set densely and did not show any air permeability just after the set. The liners which showed poor ability to inhibit the passage of the monomers generally exhibited larger solubility and disintegration in water and marked decreases in hardness and changes in structure in the monomers. Such liners may have been subjected to severe damages by the chemical actions of the adjoining monomers. Similar experiments were conducted using two brands of commercial composite resins and one experimental composite resin in place of the pure monomers. Extracted residual monomers from the composite resins through the liner, the membrane filter and glass filter were also detected even though much lesser in amount than from the pure monomers. Zinc phosphate cement and polycarboxylate cement exhibited as good blocking effect on the residual monomers in the composite resins as on the pure monomers, followed by cyanoacrylate liner and glass-ionomer cement. No blocking effect appeared to be expected in the case of applying varnish.