Faculty Collaboration Database

Analysis of four dental alloys following torch/centrifugal and induction/ vacuum-pressure casting procedures. J Prosthet Dent 2013 Dec;110(6):471-80

Date

10/15/2013

Pubmed ID

24120072

DOI

10.1016/j.prosdent.2013.09.001

Scopus ID

2-s2.0-84888424669 (requires institutional sign-in at Scopus site)   5 Citations

Abstract

STATEMENT OF PROBLEM: Previous studies have shown casting methodology to influence the as-cast properties of dental casting alloys. It is important to consider clinically important mechanical properties so that the influence of casting can be clarified.

PURPOSE: The purpose of this study was to evaluate how torch/centrifugal and inductively cast and vacuum-pressure casting machines may affect the castability, microhardness, chemical composition, and microstructure of 2 high noble, 1 noble, and 1 base metal dental casting alloys.

MATERIAL AND METHODS: Two commonly used methods for casting were selected for comparison: torch/centrifugal casting and inductively heated/ vacuum-pressure casting. One hundred and twenty castability patterns were fabricated and divided into 8 groups. Four groups were torch/centrifugally cast in Olympia (O), Jelenko O (JO), Genesis II (G), and Liberty (L) alloys. Similarly, 4 groups were cast in O, JO, G, and L by an inductively induction/vacuum-pressure casting machine. Each specimen was evaluated for casting completeness to determine a castability value, while porosity was determined by standard x-ray techniques. Each group was metallographically prepared for further evaluation that included chemical composition, Vickers microhardness, and grain analysis of microstructure. Two-way ANOVA was used to determine significant differences among the main effects. Statistically significant effects were examined further with the Tukey HSD procedure for multiple comparisons. Data obtained from the castability experiments were non-normal and the variances were unequal. They were analyzed statistically with the Kruskal-Wallis rank sum test. Significant results were further investigated statistically with the Steel-Dwass method for multiple comparisons (α=.05).

RESULTS: The alloy type had a significant effect on surface microhardness (P<.001). In contrast, the technique used for casting did not affect the microhardness of the test specimen (P=.465). Similarly, the interaction between the alloy and casting technique was not significant (P=.119). A high level of castability (98.5% on average) was achieved overall. The frequency of casting failures as a function of alloy type and casting method was determined. Failure was defined as a castability index score of <100%. Three of 28 possible comparisons between alloy and casting combinations were statistically significant. The results suggested that casting technique affects the castability index of alloys. Radiographic analysis detected large porosities in regions near the edge of the castability pattern and infrequently adjacent to noncast segments. All castings acquired traces of elements found in the casting crucibles. The grain size for each dental casting alloy was generally finer for specimens produced by the induction/vacuum-pressure method. The difference was substantial for JO and L.

CONCLUSIONS: This study demonstrated a relation between casting techniques and some physical properties of metal ceramic casting alloys.

Author List

Thompson GA, Luo Q, Hefti A

Author

Arthur Hefti DDS,PhD Associate Dean - Research & Graduate Studies in the Dentistry department at Marquette University

MESH terms used to index this publication - Major topics in bold

Chromium Alloys
Dental Alloys
Dental Casting Investment
Dental Casting Technique
Electron Probe Microanalysis
Gold Alloys
Hardness
Hot Temperature
Humans
Materials Testing
Metallurgy
Microscopy, Electron, Scanning
Palladium
Particle Size
Platinum
Porosity
Pressure
Radiography
Spectrometry, X-Ray Emission
Surface Properties
Vacuum