Fracture strength of porcelain fused to metal crowns made of cast, milled or laser-sintered cobalt-chromium

Abstract

Aims. The aim was to compare the fracture strength of porcelain fused to metal crowns with copings fabricated in Co-Cr using different manufacturing techniques (casting, milling and laser-sintering) with crowns manufactured in a high-gold alloy. Methods. A total of 50 identical crowns were fabricated and sub-divided into five groups; cast Co-Cr, milled Co-Cr, two groups of laser-sintered Co-Cr and a control group cast in a high-gold alloy. After thermocycling (5000 cycles, 5–55°C) and pre-load (30–300 N, 10,000 cycles) the crowns were loaded until fracture. Load (N) and fracture mode were recorded. Results. There was a significant difference (p < 0.05) in fracture strength between the control group and one of the laser-sintered groups. The mean values (N) for the groups were as follows: cast Co-Cr, 1560 ± 274; milled Co-Cr, 1643 ± 153; laser-sintered Co-Cr 1, 1448 ± 168; laser-sintered Co-Cr 2, 1562 ± 72; control group, 1725 ± 220. Conclusion. There is no difference in strength between Co-Cr crowns produced using the different production technologies: casting, milling or laser-sintering. Metal ceramic crowns made with copings fabricated in a high-gold alloy present numerically higher fracture strength than crowns made with copings fabricated in Co-Cr alloys. The difference is confirmed when analyzing the fracture surfaces, but the difference in fracture strength value is limited and is only significant with regard to one of the two laser-sintered groups.

Key Words::

• CAD/CAM dental
• Co-Cr alloys
• dental laser sintering
• fracture strength
• metal ceramic alloys

Acknowledgment

The authors want to thank Dental Syd (Dental Syd AB, Malmö, Sweden) for scanning the die replica. The M-tec milling center (M-tec AB, Malmö, Sweden) for fabricating the milled Co-Cr copings and Biomain (Biomain AB, Helsingborg, Sweden) and BEGO (Bremer Goldschlägerei. Wilh. Herbst GmbH & Co. KG, Bremen, Germany) production centers for fabricating the laser-sintered copings. The Multilink® Automix cement was kindly provided by Ivoclar Vivadent (Stockholm, Sweden) and C-Cast discs by Kavo (Stockholm, Sweden). Evaggelia Papia for the SEM analysis.

Declaration of interest:

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.