Evaluation of the effects of mechanical properties in feldspathic porcelain by addition of bor alloys

Background: Even though the dental ceramics are strong and heat-resistant, they are brittle and can be broken in a sudden change of force and temperature. Micro-cracks are formed in the ceramic structure as a result of volumetric shrinkage during porcelain firing and cooling after firing. These micro-cracks would unfavorably affect the mechanical behavior of the structures. One of the factors that positively affect the mechanical behavior of the ceramics against force is the presence of crystal structures added to the ceramic. The aim of this study is to improve the mechanical strength and to reduce the micro-cracks that occur in the microstructure of the dentin ceramic, by adding various boron compounds (borax, boric acid) to the dentin ceramic. Materials and Methods: Crack lengths, flexural strength and fracture toughness values of borax and boric acid (1,2,3% of the weight percent) added traditional feldspathic porcelain were analyzed in this study. The data obtained in the study were statistically analyzed by one-way ANOVA (p <0.05). Differences between groups were determined by the Tukey HSD method. Results: The crack lengths were decreased, and the fracture toughness values were increased in all boric acid added groups. However, the difference between groups was not statistically significant. Also, while the crack lengths were decreased and the fracture toughness values were increased in 1% and 2% borax added groups, the addition of 3% borax had increased the crack length, and reduced the fracture toughness. However, the difference between groups was not statistically significant. On the other hand, the group containing 1% boric acid had statistically significantly decreased the biaxial flexural strength value compared to the control group (p = 0.034, p <0.05). Differences in biaxial values between the other groups were not statistically significant. Besides, the Vicker's hardness value of the group containing 1% borax was found to be statistically significantly lower (p = 0.042, p <0.05). Conclusions: It was observed that various proportions of borax and boric acid addition in dentin ceramic had reduced the formation of cracks but this finding was not statistically significant.