Pilot study of the relationship between the hardness and abrasion resistance of two base metal alloys used for metal-ceramic restorations

Correlation between microhardness and wear resistance of dental alloys against monolithic zirconia

PURPOSE

The aim of this study is to compare the hardness according to the conditions of metal alloys. Moreover, the correlation between the cast crown hardness before and after wear testing and the degree of wear for each dental alloy was assessed.

MATERIALS AND METHODS

Cast crowns of three metal alloys (Co-Cr, gold, and Ni-Cr alloys) opposing smooth-surface monolithic zirconia were used. The Vickers microhardness of the ingot (which did not undergo wear testing) and the cast crown before and after wear testing were measured for each alloy. Two-way ANOVA and Scheffé tests were used to compare the measured hardness values. Moreover, the Pearson correlation coefficient was used to evaluate the relationship between the surface hardness and the wear of the cast crown (α=.05).

RESULTS

There was no significant difference in the hardness before and after wear testing for the gold alloy (P>.05); however, the hardness of the worn surface of the cast crown increased compared to that of the cast crown before the wear tests of Ni-Cr and Co-Cr alloys (P<.05). Furthermore, there was no correlation between the wear and hardness of the cast crown before and after wear testing for all three metal alloys (P>.05).

CONCLUSION

There was a significant difference in hardness between dental alloys under the same conditions. No correlation existed between the surface hardness of the cast crown before and after wear testing and the wear of the cast crown.

Sprue design alterations and its effect on the properties of base metal alloy castings: An in vitro study

Introduction:

To study the effect of various sprue designs on the properties of base metal alloy castings. The base metal alloys are extensively used for their excellent properties such as an increase in hardness, high melting range, high elastic modulus, its compatibility with ceramic material and low cost. However, to improve the properties of the base metal alloys is an ongoing research leading to various modifications in their fabrication procedure – which include sprue designs and their mode of attachment to the wax pattern.

Aims and Objectives:

Study compared the effect of three sprue designs viz. conical sprue, cylindrical sprue and bottleneck sprue on the properties of mass and microhardness of base metal alloy castings.

Materials and Methods:

A prefabricated wax mesh pattern was selected for the fabrication of the alloy test samples in the study. The cylindrical sprue design was connected to the mesh pattern with a straight attachment. The bottleneck sprue design was connected to the mesh pattern with a constricted attachment. The conical sprue design was connected to the mesh pattern with a flared attachment. In this manner, ten samples for each of the three different sprue designs were prepared.

Results:

The obtained value for mass and microhardness were subjected to statistical analysis. ANOVA test was performed to determine the difference between the sprue designs.

Conclusion:

The bottleneck sprue, conical sprue, and cylindrical sprue designs did not exert any apparent influence on the mass and microhardness.