Effects of zirconia additives on beta-tricalcium-phosphate cement for high strength and high injectability

Injectable calcium phosphate cements (CPCs) exhibit many advantages as bone substitution materials. However, the strength of injectable CPCs after setting are often insufficient. In our previous studies, mechano-chemically modification of ll-tricalcium phosphate cement powder through a planetary ball-milling process exhibited simultaneous improvement in the strength and injectability of CPC. Two plausible effects of this process are: changes in the CPC powder properties and zirconia abrasion powder contamination from the milling pot and balls. The objective of the present study is to separately evaluate these two effects on the strength and inject ability of CPCs. The calculated injectability of the cement paste with and without the addition of zirconia powder were higher than 65% at 6 h after mixing. These values were much higher than that of the CPC paste without mechanochemically modification, and similar to that of CPC with zirconia abrasion powder contamination. By contrast, the compression strength of the set CPC with zirconia powder additives were higher than that without the addition, and similar to that of CPC with zirconia abrasion powder contamination. These results suggest that the changes in the CPC powder properties due to mechano-chemically modification mainly affected the inject ability of the CPC paste, and the zirconia abrasion powder contamination of the CPC powder affected the strength of the set CPC.