Abstract
The present study concerns the effect of differences in the type of direct retainers and in the arrangement of rests on the distribution of pressures under dentures. A model with both mandibular molars missing (Kennedy classification of partial dentures-Class I) was prepared. Then two types of direct retainers, one using the Krol type R.P.I.clasp and the other using the Kratochvil type R.P.I.clasp, were selected.Then three types of rests were prepared.
Then the pressures under dentures were measured and the conclusions presented below were obtained.
1.Between the direct retainer and rest, the direct retainer tended to exert greater effect on the pressures under dentures.
2.Between direct retainers, the Krol type R.P.I.clasp tended to show greater pressures than the Kratochvil type R.P.I.clasp.
3.In the effect of differences in the rest arrangement, the smaller the number of rest, the greater the effect on the pressures.
4.In case of the fabrication of partial dentures against the mandibular bilateral distal extention case, the combination of the use of the direct retainer as the Kratochvil R.P.I.clasp and arrangement of the rests on the mesial side of the occlusal table of the second premolars on both sides and on the mesial and distal side of theocclusal table of the first premolars on both sides was suggested to be clinically the best design from the viewpoints such as distribution and uniformity of the pressures under dentures.
