Min-Ho Hong1, Bong Ki Min2, Du-Hyeong Lee3, Tae-Yub Kwon4. 1. Postdoctoral Researcher, Institute for Biomaterials Research and Development, Kyungpook National University, Daegu, Republic of Korea. 2. Senior Researcher, Center for Research Facilities, Yeungnam University, Gyeongsan, Republic of Korea. 3. Associate Professor, Department of Prosthodontics, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea. 4. Professor, Department of Dental Biomaterials, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea. Electronic address: tykwon@knu.ac.kr.
Abstract
STATEMENT OF PROBLEM: Few studies have investigated changes in the marginal fit of metal-ceramic restorations fabricated by selective laser melting (SLM) techniques after the application of veneering ceramic. PURPOSE: The purpose of this in vitro study was to evaluate the marginal fit (silicone replica technique) and internal porosity (cross-section analysis) of cobalt-chromium (Co-Cr) alloy metal crowns prepared by using 2 SLM processes together with a casting technique before and after ceramic veneering. MATERIAL AND METHODS: Cast single Co-Cr crowns and SLM-processed crowns with large (SLML) or small (SLMS) porosity were prepared (n=20/group), and half were subjected to ceramic veneering. On a single Co-Cr master die, the marginal discrepancy (MD) and absolute marginal discrepancy (AMD) of the crowns were measured by using the silicone replica technique, in which each replica was cut into 4 sections before and after ceramic veneering (n=10 for each subgroup). After marginal fit measurements, each metal coping was cross-sectioned into 4 parts, and 5 rectangular optical microscope images were acquired on both outer corners of each quarter. The porosity was then calculated as the ratio of the black-to-white pixels on the binarized images. The data were analyzed by 2-way ANOVA and the post hoc test (Tukey or Student t test) (α=.05). RESULTS: Before ceramic veneering, the 2 SLM groups showed significantly larger MDs than the casting group (56.4 ±10.4 μm) (P<.05). A significant increase in MD after ceramic veneering was detected only in the SLML group (P<.001). The AMD values showed a similar trend with MD values. The 2 SLM groups (in particular, SLML) showed a significantly higher amount of porosity than the casting group before ceramic veneering (P<.001). Only the SLML group showed a significant decrease in the amount of porosity after ceramic veneering (P<.001). CONCLUSIONS: Within the limitations of this in vitro study, large internal porosity within the SLM-fabricated Co-Cr metal copings affected the marginal fit of the metal-ceramic crowns. However, all the MD values of the 3 groups were lower than the acceptable range even after the application of veneering ceramic.
STATEMENT OF PROBLEM: Few studies have investigated changes in the marginal fit of metal-ceramic restorations fabricated by selective laser melting (SLM) techniques after the application of veneering ceramic. PURPOSE: The purpose of this in vitro study was to evaluate the marginal fit (silicone replica technique) and internal porosity (cross-section analysis) of cobalt-chromium (Co-Cr) alloy metal crowns prepared by using 2 SLM processes together with a casting technique before and after ceramic veneering. MATERIAL AND METHODS: Cast single Co-Cr crowns and SLM-processed crowns with large (SLML) or small (SLMS) porosity were prepared (n=20/group), and half were subjected to ceramic veneering. On a single Co-Cr master die, the marginal discrepancy (MD) and absolute marginal discrepancy (AMD) of the crowns were measured by using the silicone replica technique, in which each replica was cut into 4 sections before and after ceramic veneering (n=10 for each subgroup). After marginal fit measurements, each metal coping was cross-sectioned into 4 parts, and 5 rectangular optical microscope images were acquired on both outer corners of each quarter. The porosity was then calculated as the ratio of the black-to-white pixels on the binarized images. The data were analyzed by 2-way ANOVA and the post hoc test (Tukey or Student t test) (α=.05). RESULTS: Before ceramic veneering, the 2 SLM groups showed significantly larger MDs than the casting group (56.4 ±10.4 μm) (P<.05). A significant increase in MD after ceramic veneering was detected only in the SLML group (P<.001). The AMD values showed a similar trend with MD values. The 2 SLM groups (in particular, SLML) showed a significantly higher amount of porosity than the casting group before ceramic veneering (P<.001). Only the SLML group showed a significant decrease in the amount of porosity after ceramic veneering (P<.001). CONCLUSIONS: Within the limitations of this in vitro study, large internal porosity within the SLM-fabricated Co-Crmetal copings affected the marginal fit of the metal-ceramic crowns. However, all the MD values of the 3 groups were lower than the acceptable range even after the application of veneering ceramic.
Authors: Peter Gehrke; Philip Hartjen; Ralf Smeets; Martin Gosau; Ulrike Peters; Thomas Beikler; Carsten Fischer; Carolin Stolzer; Jürgen Geis-Gerstorfer; Paul Weigl; Sogand Schäfer Journal: Int J Mol Sci Date: 2021-01-17 Impact factor: 5.923