PURPOSE: To obtain the subject excellent material for denture bases, having extremely low water absorptivity without any malodor even in mounting thereof in the oral cavity for a long period and capable of keeping a clean state for a long period, etc., by mixing vinylidene difluorides and, as necessary, polychlorotetrafluoroethylene therein.

CONSTITUTION: A material is composed of vinylidene difluoride expressed by the formula [R1 and R2 are perfluoroalkyl or H; the ratio (n/m) of (n) to (m) is (100/0) to (0/100)wt.% ratio] or a derivative thereof and prepared by, as necessary, mixing 5-15% polychlorotetrafluoroethylene (hereinafter abbreviated to PCTFE) capable of imparting toughness therein. The resin expressed by the formula and PCTFE contain no additive and are safe for human bodies, also chemically stable, excellent in durability and hardly discolored. The resin expressed by the formula has 115 Rockwell hardness which is a sufficient hardness as denture bases with extremely low water absorptivity. The aforementioned material can be molded by a normal press molding, an injection molding methods and a combined molding method of both the molding methods.