Effect of different labio-lingual spaces in tray designs on the displacement of and pressure against a mobile tooth.

The present study aimed to examine the effect of custom tray designs on the displacement of mobile tooth and local impression pressures during the impression procedure, using partially edentulous simulation models with six anterior teeth containing a mobile tooth prepared in previous studies. The custom trays were designed by altering the thickness of the respective spaces on the labial and lingual sides of the remaining tooth arch. In previous studies, the mobile tooth was displaced in the labial direction and local impression pressures of the mobile tooth were greater against the lingual side than the labial side for all custom tray designs. Furthermore, the custom trays perforated with holes on the lingual side were effective to reduce mobile tooth displacement, labial and lingual impression pressures against the mobile tooth, and the differences between them. Therefore, the present study was performed focusing on the labial and lingual thickness of spaces in custom tray designs. It was found that mobile tooth displacement, labial and lingual impression pressures against the mobile teeth and their differences were less in trays with spaces>3.0 mm thick on both the labial and lingual sides, but markedly greater in trays with a 1.5 mm-thick space on the labial side. These results indicate that the thickness of spaces on the labial side in the tray should not be reduced to prevent mobile tooth displacement.