[Studies on retainer's effect on unilateral designs of mandibular unilateral distal extention dentures]

Distal extention denture has intrinsic characteristics of cantilever and inevitably rotates around abutment tooth due to the difference of force transmissive characteristics between abutment tooth and alveolar mucosa. This study was undertaken to figure out the possible forms of advanced unilateral clasp denture and the principle to design them in the co-operation of direct and indirect retainer, and telescope retainer. The results were as follows: 1. Splinting of abutment resulted in much more efficient dispersion of load and in reduction displacement of abutment and denture base. 2. Generally the distal extention denture without indirect retainer exhibited considerable amount of displacement of abutment and denture base. Therefore this type of denture could not be an option upon designing unilateral denture. 3. Adequate organization of splinting of abutment, guide plane, and retainer with millinged abutment on clasp design denture was shown to improve retaining power as high as that of telescopic design denture. 4. Telescopic design denture with multiple abutment was much more preferable than that with single abutment. The amount of displacement of abutment and denture base could be greatly reduced by addition of positive-type indirect retainer to telescopic design denture with multiple abutment.