Abstract
The anchorage by investing was practiced to make a linear 3-unit bridge for molars by the soldering method. An experiment was carried out to determine the adaptability after soldering when three factors constituting the size of the investing block; i.e. the height, the buccolingual width, and the mesial-distal width, are changed. The following results have been obtained:
1. Two of the factors constituting the invested block, the height and the buccolingual width, affected the adaptability of bridges with a significance of 1% of danger rate.
2. As to the displacement quantity, the mesial-distal displacement was largest when the height of the block was 10 mm.
3. As to distortion, the occlusal surface was bent throughout the bridge and the distortion was observed in the direction of the neck of the tooth, which was more serious when the invested block was thinner.
4. The size of the block with witch the best adaptability was obtained was 20 mm in height, 25 mm in buccolingual width and 35 mm in mesial-distal width.
