Internal fit of bridge patterns fabricated by a 3D printing technique

Abstract

The purpose of this study was to compare the marginal and internal fit of resin bridge patterns fabricated by a 3D printer system. Three type bridge models (2-, 3-, 4-unit bridge) were prepared with die stone and two types of margin, knife or chamfer were applied to the abutment teeth. The gypsum models were used to fabricate resin patterns by a 3D printer. The printed resin patterns were fixed to their master dies using zinc phosphate cement and then invested with dental stone in a box. The resin patterns were cut mesiodistally using a diamond saw and further polished with #1000 SiC paper. Internal fit of the bridge patterns was measured at areas of marginal opening (MO), marginal gap (MG) of maximum curvature area, axial gap (AG), and occlusal gap (OG) from the images of gaps captured by a stereoscope with CCD camera. Overall, mean gap dimensions of the resin patterns prepared in this study were <155 μm, except for OG. The 3D bridge patterns with chamfer margin showed a significantly higher adaptation accuracy at MO, but those with knife margin showed a better accuracy at MG. Internal fit of all patterns at AG were found to be <50 μm.