Statement of problem
The selective laser melting (SLM) technique has been a promising method of fabricating Co-Cr metal-ceramic restorations; however, the lower metal-ceramic bond properties of SLM Co-Cr restorations have become a major issue in clinical use.
The purpose of this in vitro study was to propose and verify a method of improving the metal-ceramic bond properties of SLM Co-Cr alloy with heat treatment after porcelain firing (PH).
Material and methods
Forty-eight (25×3×0.5 mm) Co-Cr specimens, divided into 6 groups (Control group [CG]; 550 °C; 650 °C; 750 °C; 850 °C; 950 °C) according to PH temperatures, were prepared by using SLM techniques. The 3-point bend tests were performed to evaluate the metal-ceramic bond strengths; subsequently, the fracture feature was assessed by using a digital camera and scanning electron microscope (SEM) coupled with an energy-dispersive X-ray spectroscopy (EDS) detector, to determine the area fraction of adherence porcelain (AFAP). The interface morphologies and element distribution were determined with SEM/EDS detectors. Phase identification and quantification were examined with an X-ray diffractometer (XRD). A 1-way ANOVA and the Tukey honestly significant difference tests were used to analyze bond strengths and AFAP values (α=.05).
The bond strengths were 35.33 ±1.25 MPa for the CG group, 34.53 ±3.20 MPa for the 550 °C group, 38.20 ±2.60 MPa for the 650 °C group, 42.85 ±2.31 MPa for the 750 °C group, 33.28 ±3.85 MPa for the 850 °C group, and 29.09 ±2.86 MPa for the 950 °C group. Significant differences were not observed among the CG, 550 °C, and 850 °C groups (P>.05) but were found among the other groups (P<.05). Fracture and AFAP results displayed a mixed fracture mode of adhesive and cohesive fracture. The thicknesses of native oxide films across the 6 groups were relatively close as the temperature increased, but the thickness of the diffusion layer increased as well. Excessive oxidation and massive phase transformation caused holes and microcracks to appear in the 850 °C and 950 °C groups, reducing bond strengths. XRD analysis evidenced that the phase transformation of γ→ε occurred at the interface during PH treating.
PH treatment significantly affected the metal-ceramic bond properties of SLM Co-Cr porcelain specimens. The 750 °C-PH-treated specimens displayed higher mean bond strengths and improved fracture characteristics among the 6 groups.
To read this article in full you will need to make a payment
Purchase one-time access:Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
One-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:Subscribe to Journal of Prosthetic Dentistry
Already a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
- Structural characterization of biomedical Co-Cr-Mo components produced by direct metal laser sintering.Mat Sci Eng C-Mater. 2015; 48: 263-269
- Metallurgical and interfacial characterization of PFM Co–Cr dental alloys fabricated via casting, milling or selective laser melting.Dent Mater. 2014; 30: 79-88
- Fatigue strength of Co-Cr-Mo alloy clasps prepared by selective laser melting.J Mech Behav Biomed Mater. 2016; 59: 446-458
- Defects-tolerant Co-Cr-Mo dental alloys prepared by selective laser melting.Dent Mater. 2015; 31: 1435-1444
- Microstructural, mechanical, ionic release and tarnish resistance characterization of porcelain fused to metal Co-Cr alloys manufactured via casting and three different CAD/CAM techniques.J Prosthodont Res. 2019; 63: 150-156
- Microstructural Characterization, Mechanical properties, and corrosion resistance of dental Co-Cr-Mo-W alloys manufactured by selective laser melting.J Mater Eng Perform. 2018; 27: 5312-5320
- Microstructural features of biomedical cobalt-chromium-molybdenum (CoCrMo) alloy from powder bed fusion to aging heat treatment.J Mater Process Tech. 2020; 45: 146-156
- Microstructures and metal-ceramic bond properties of Co-Cr biomedical alloys fabricated by selective laser melting and casting.Mat Sci Eng A-Struct. 2019; 759: 594-602
- Adhesion of dental porcelain to cast, milled, and laser-sintered cobalt-chromium alloys: shear bond strength and sensitivity to thermocycling.J Prosthet Dent. 2014; 112: 600-605
- Adherence controlling elements in ceramic-metal systems. II. Nonprecious alloys.J Dent Res. 1977; 56: 1053-1061
- Study of bond strength of dental porcelain fused to metal.J Dent Res. 1966; 45: 1047-1051
- Phillips’ science of dental materials.12th ed. W.B. Saunders, Philadelphia2012: 621-654
- Craig’s restorative dental materials.13th ed. Mosby-Year Book Inc, St. Louis2012: 231-251
- Effects of the rare earth element lanthanum on the metal-ceramic bond strength of dental casting Co-Cr alloys.J Prosthet Dent. 2019; 121: 848-857
- Effect of annealing procedure on the bonding of ceramic to cobalt-chromium alloys fabricated by rapid prototyping.J Prosthet Dent. 2018; 119: 643-649
- Effects of heat treatment on metal-ceramic combination of selective-laser-melted cobalt-chromium alloy.J Prosthet Dent. 2018; 120: 319.e1-319.e6
- Effects of multiple firings on metal-ceramic bond strength of Co-Cr alloy fabricated by selective laser melting.J Prosthet Dent. 2016; 115: 109-114
- Microstructure evolution and mechanical properties improvement of selective laser melted Co-Cr biomedical alloys during subsequent heat treatments.J Alloys Compd. 2020; 840: 155664
- ISO 9693-1(E): Dentistry – Compatibility testing – Part 1: Metal-ceramic systems. International Organization for Standardization, Geneva2012.(Available at:)
- Effect of heat-treatment temperature on microstructures and mechanical properties of Co-Cr-Mo alloys fabricated by selective laser melting.Mat Sci Eng A-Struct. 2018; 726: 21-31
- An x-ray spectrometric technique for measuring porcelain-metal adherence.J Dent Res. 1983; 62: 933-936
- Méthode d'analyse quantitative des variétés allotropiques du cobalt par les rayons X.Rev Metall-Paris. 1950; 49: 139-145
- Comparative analysis of the microstructures and mechanical properties of Co-Cr dental alloys fabricated by different methods.J Prosthet Dent. 2018; 120: 617-623
Published online: March 02, 2023
Publication stageIn Press Corrected Proof
© 2023 by the Editorial Council for the Journal of Prosthetic Dentistry.