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Altered corrosion resistance from casting to stainless steel posts
J A Sorensen1, M J Engelman, T Daher
1University of California, School of Dentistry, Los Angeles.
The Journal of Prosthetic Dentistry
|June 1, 1990
Summary
Simulated burnout procedures, including heat treatment and investment materials, significantly reduce the corrosion resistance of stainless steel posts. Direct casting onto these posts is not recommended due to this decreased durability.
Area of Science:
- Materials Science
- Biomaterials Engineering
- Dental Materials
Background:
- Stainless steel posts are widely used in dental restorations.
- The burnout procedure, involving heat treatment, is a critical step in casting prosthetics.
- Concerns exist regarding the potential for heat treatment to compromise the corrosion resistance of stainless steel posts.
Purpose of the Study:
- To investigate the impact of simulated burnout procedures on the corrosion resistance of stainless steel posts.
- To evaluate the effects of different investment materials (gypsum-bonded and phosphate-bonded) and cooling methods (bench cooling and quenching) on post integrity.
Main Methods:
- Five groups of stainless steel posts were subjected to distinct simulated burnout conditions.
- Control group: no treatment.
- Experimental groups: gypsum-bonded or phosphate-bonded investment with either bench cooling or quenching.
- Corrosion resistance was assessed over 30, 180, and 600 days in Ringer's solution.
- Analytical techniques included scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), optical emission spectroscopy (OES), and optical microscopy.
Main Results:
- Simulated burnout procedures, involving investment materials and heat treatment, altered the metallic structure of stainless steel posts.
- Posts subjected to these procedures exhibited a significant reduction in corrosion resistance compared to the control group.
- Both gypsum-bonded and phosphate-bonded investments, especially when quenched, contributed to the degradation of corrosion resistance.
Conclusions:
- Heat treatment during burnout procedures negatively affects the corrosion resistance of prefabricated stainless steel posts.
- The choice of investment material and cooling method during burnout influences the extent of corrosion.
- Direct casting onto stainless steel posts is contraindicated due to the observed reduction in corrosion resistance.