Microstructure, elemental composition, hardness and crystal structure study of the interface between a noble implant component and cast noble alloys.

STATEMENT OF PROBLEM

Casting a high-gold alloy to a wrought prefabricated noble implant-component increases the cost of an implant. Selecting a less expensive noble alloy would decrease implant treatment costs.

PURPOSE

The purpose of this study was to investigate the interfacial regions of a representative noble implant component and cast noble dental alloys and to evaluate the effects of porcelain firing cycles on the interface.

MATERIAL AND METHODS

Six representative alloys (n=3) were cast to gold implant abutments (ComOcta). Scanning electron microscopy (SEM) was used to characterize microstructures. Compositions of interfacial regions and bulk alloys were obtained by energy-dispersive spectroscopy. Vickers hardness was also measured across the interface. By using Micro-X-ray diffraction, the phases were evaluated at 7 points perpendicular to the interface. The effects of porcelain firing cycles on microstructures, diffusion, hardness, and phases were also evaluated. For statistical evaluation of diffusion length and hardness, a 3-way repeated measures ANOVA was used. Pairwise comparisons of interest were conducted with Tukey pairwise comparisons or, when a significant interaction was found, Bonferroni-adjusted t-tests (overall α=.05).

RESULTS

Microstructures of bulk alloys were predominantly maintained to a well-defined boundary for both as-cast and heat-treated conditions. An interaction band, 5-6 μm wide, was observed. The alloy grain size at the interface and the interaction band width increased after simulated porcelain firing. The extent of elemental diffusion from the interface was about 30 μm and not affected by simulated porcelain firing. Differences in Vickers hardness for the alloys were consistent with their compositions. Micro-XRD patterns indicated that substantial amounts of new phases had not formed at the interfacial regions.

CONCLUSIONS

Less expensive noble alternatives to high-gold alloys provided comparable metallurgical compatibility with the noble implant component.