The relationship between critical convergence angle and surface defects in stone casts.

Surface defects on stone casts threaten the accuracy of cast restorations. The aim of this study was to examine the relationship between critical convergence angle and voids in stone casts. Three addition silicone materials, one condensation silicone material, and one polyether impression material were used. The highest convergence angle at which voids presented at the tip of the specimens was recorded, and the number of voids found at margins and line angles of tile tooth preparations were counted. Results showed a positive and significant correlation between the critical convergence angle and the number of voids at margins and line angles of stone casts. Casts poured franz polyether impressions registered significantly lower critical convergence angle values and presented with fewer voids than did those fabricated from silicone materials.