Evaluation of marginal and internal gaps in single and three-unit metal frameworks made by micro-stereolithography

PURPOSE: The purpose of this study is to compare single and three-unit metal frameworks that are produced by micro-stereolithography. MATERIALS AND METHODS: Silicone impressions of a selected molar and a premolar were used to make master abutments that were scanned into a stereolithography file. The file was processed with computer aided design software to create single and three-unit designs from which resin frameworks were created using micro-stereolithography. These resin frameworks were subjected to investment, burnout, and casting to fabricate single and three-unit metal ones that were measured under a digital microscope by using the silicone replica technique. The measurements were verified by means of the Mann-Whitney U test (α=.05). RESULTS: The marginal gap was 101.9 ± 53.4 µm for SM group and 104.3 ± 62.9 µm for TUM group. The measurement of non-pontics in a single metal framework was 93.6 ± 43.9 µm, and that of non-pontics in a three-unit metal framework was 64.9 ± 46.5 µm. The dimension of pontics in a single metal framework was 110.2 ± 61.4 µm, and that of pontics in a three-unit metal framework was 143.7 ± 51.8 µm. CONCLUSION: The marginal gap was smaller for the single metal framework than for the three-unit one, which requires further improvement before it can be used for clinical purposes.