Recently, various kinds of resins are in the market. Among several resins for the artificial denture base, the heat-curing methacrylic resin made by mixing monomer and polymer has widely been used.Despite its favorable characteristics of being supple, the heat-curing methacrylic resin has an unescapable defect of shrinkage at the time of heating.
An attempt was made to overcome the defect of the methacrylic resin in a simple way.Special attention was paid to eliminate the unfit at the mucous side of a denture base caused by the shrinkage at the time of heating. The heat expanding microcapsule (Matsumoto Microsphere F-30) was used as heat expanding mold seal, thus making the unfavorable shrinkage or gap minimum.Basic experiments were conducted on the expansion of the heat expanding microcapsule and on the shrinkage of the resin.Further experiments were conducted on the effect of contraction control of the resin made by conventional heat-curing method and applied with heat expanding mold seal.
The following were the results of the present study.
1.The rate of polymerization shrinkage was about 20% with L-Resin, Urban, and MMA monomers, and the rate slightly decreased as the content of crosslinking agent increased.
2.The rate of heat expansion at the same temperure increased as the content of F-30 in the thin film increased.
3.In the experiment of applying thin films of the heat expanding mold seal to the resin block, the gap distance at the plaster surface decreased as the content of F-30 in the thin film increased.
4.Applying the heat expanding mold seal to the lower complete denture improved the fit at the mucous side and at the junction of porcelain teeth.