Objectives: To evaluate marginal fit and stability of porcelain-fused to metal crowns (PFMCs) using a new laser-melting-technology for fabrication of metallic copings. Methods: 5 extracted teeth, molars and Premolars, were prepared with a circumferential shoulder. Impression was taken (Impregum, 3M-ESPE) and plaster dies (Fujirock, GC) were cast. The dies were scanned using a CAD/CAM unit and copings were designed and fabricated with a laser-melting-technology (BEGO Medifacturing, BEGO, Germany), compacted metallic powder derived from a CoCrMo-alloy (Wirobond C+, BEGO). The copings were veneered with conventional PMF-ceramic (Omega, VITA) and luted on the natural teeth with ZnO-Phosphate cement under standardized conditions. The circumferential marginal gap was measured with a light-microscope, randomly selected 50 measurement points for each of the five teeth. A steel die was fabricated by copying a natural upper first incisor which was prepared with a circumferential shoulder. For this steel die 6 copings were cast (CoCrMo-alloy, Wirobond BEGO) and 6 copings were computer-designed and laser-melted as described above. All copings were veneered with ART-i-motion (Debomed) ceramics. The PFMCs were consecutively cemented onto the steel die with ZnO-Phosphate cement, placed into a testing machine (Zwick Z005) and loaded axially. The mean fracture loads of the veneered cast and veneered laser-melted-crowns were compared with t-test. Results: The mean gap was 29 µm (84 % of 250 measurements were smaller than 50 µm, maximum value 100 µm). The mean fracture load of veneered cast PFMCs was 2080 N (SD 830 N) compared to 1887 N (SD 510 N) of veneered laser-melted PFMCs. The difference was statistically insignificant (p > 0,05). Conclusion: In-vitro evaluation of marginal fit and stability with revealed data supports clinical tests of laser-melted PFMCs. |