Nippon Oil Company

Toshiyuki Ohban

Masao Nambu

Osamu Kuwabara

Yoshihiko Okuno

A denture base contains an elastic support for supporting at least one artificial tooth and fittings fixed to the elastic support for removably positioning the denture base. The elastic support is made of a hydrogel prepared by a process comprising a casting step of casting into a mold an aqueous solution containing more than 5 wt % and not more than 40 wt % of a polyvinyl alcohol having a degree of hydrolysis of not less than 95 mol % and an average polymerization degree of not less than 700, a freezing step of cooling the cast aqueous solution to a temperature of not higher than - (minus) 10.degree. C. to obtain a frozen mass, a thawing step of thawing the frozen mass, and one to seven additional cyclic processing steps each including the freezing and thawing steps.

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Osaka, Japan

Toshiyuki Ohban