The deficiency of the rigidity of the retainer causes the falling of the acid-etched fixed partial denture from the abutment teeth. It was reported in the previous paper that the adhesive strength of the bridge increased as the thickness of the retainer increasing and reached the plateau. Suitable thickness of the retainer, however, may be difficult to obtain due to the occlusal relation. The purpose of this study is to look for the proper shape of the retainer. The following conclusions were obtained. 1) Using cobalt-cromium alloy, the adhesive strength in the retainer of 1.0 mm thickness was better than that of 0.5 mm on the same shape. 2) The extension of proximal wing portions and adding ledge-form were effective to gain higher adhesive strength in using cobalt-cromium alloy and Au-Ag-Pd alloy.

Abstract:Temporary restoration is useful to decide prosthodontic method.If the strength of the temporary restoration is so higher that is tolerable in services for long period, fixed prosthesis is better than removable one in regard to an appearance and a feeling.The purpose of this study is to confirm experimentally the strength of the provisional fixed prostheses which are composed of acrylic resin teeth and adhesive resin. The compressive force need to replace the pontic which is directly bonded the extracted human teeth was measured in vitro.Approximate 30 kg was needed to break the provisional adhesive pontic, whereas about 120 kg was needed to the posterior pontic reinforced with wire.These results suggest that this method is useful as one of the provisional treatments.