Evaluation of marginal and internal fit of metal copings fabricated by selective laser melting

Abstract

Methods: An extraoral scanner was used to scan a die of the prepared maxillary right first molar, and the coping was designed using computer-aided design software and saved as an stereo lithography (STL) file. Ten specimens were printed with an SLM-type metal 3D printer (SLM group), and 10 more specimens were fabricated by casting the castable patterns output generated by a digital light processing-type resin 3D printer (casting the 3D printed resin patterns [CRP] group). The fit was measured using the silicon replica technique, and 8 points (A to H) were set per specimen to measure the marginal (points A, H) and internal (points B~G) gaps. The differences among the groups were compared using the Mann-Whitney U-test (α=0.05). Results:The mean of marginal fit in the SLM group was 69.67±18.04 µm, while in the CRP group was 117.10±41.95 µm. The internal fit of the SLM group was 95.18±41.20 µm, and that of the CRP group was 86.35±32 µm. As a result of statistical analysis, there was a significant difference in marginal fit between the SLM and CRP groups (p<0.05); however, there was no significant difference in internal fit between the SLM group and the CRP group (p>0.05). Conclusion:The marginal and internal fit of SLM is within the clinically acceptable range, and it seems to be applicable in terms of fit.