Comparison of porcelain bond strength of different metal frameworks prepared by using conventional and recently introduced fabrication methods

Abstract

Statement of problem. Most studies evaluating dental laser sintering systems have focused on the marginal accuracy of the restorations. However, the bond strength at the metal-ceramic interface is another important factor that affects the survival of restorations, and currently, few studies focus on this aspect. Purpose. The purpose of this in vitro study was to compare the porcelain bond strength of cobalt-chromium (Co-Cr) metal frameworks prepared by using the conventional lost-wax tech nique, milling, direct metal laser sintering (DMLS), and laser cusing, a direct process powder bed system. Material and methods. A total of 96 metal frameworks (n=24 in each group) were prepared by using conventional lost-wax (group C), milling (group M), DMLS (group LS), and direct process powder-bed (group LC) methods according to International Organization for Standardization standard ISO 9693-1. After porcelain application, a 3-point bend test was applied to each specimen by using a universal testing machine. Data were statistically analyzed using 1-way ANOVA and Tukey honest significant difference tests (alpha=.05). Failure types at the metal-ceramic interfaces were examined using stereomicroscopy. Additionally, 1 specimen from each group was prepared for scanning electron microscopy analysis to evaluate the surface topography of metal frameworks. Results. The mean bond strength was 38.08 +/- 3.82 MPa for group C, 39.29 +/- 3.51 MPa for group M, 40.73 +/- 3.58 MPa for group LS, and 41.24 +/- 3.75 MPa for group LC. Statistically significant differences were observed among the 4 groups (P=.016). All groups, except for LS, exhibited adhesive and mixed type bond failure. Conclusions. Both of the laser sintering methods were found to be successful in terms of metal ceramic bond strength.