Different yttrium stabilized zirconium-oxide core ceramics have different element contents

Introduction: Yttrium stabilized zirconium-oxide ceramics are considered highly stable materials and are coming into wide use as core materials for ceramic crowns. However, little is known about possible contaminants. Objectives: To investigate and compare some relevant elements in three commercially available yttrium stabilized zirconium-oxide ceramic core materials. Methods: The element content of the materials Lava, DC Zircon and Procera Zirconia were studied by the laser ablation ICP/MS technique (UP213, New Wave, USA). Nine test-spots were made in each material. The following isotopes were analyzed: Zr90, La139, Ce142, Pr141, Nd146, Sm147, Eu153, Gd157, Tb159, Dy163, Ho165, Er166, Tm169, Yb172, Lu175, Hf178, Pb208, Th232 and U238. Y89 was used as an internal standard. Results: Lava contained significantly less Zr90 (mean 565000 ppm vs. 689000 ppm and 634000 ppm) and more Er166 (mean 1999 ppm vs. 0.6 ppm and 0.5 ppm) than DC Zircon and Procera Zirconia (One-way ANOVA-test). This is consistent with the yellow coloured Lava containing the pigment erbium oxide. Lava also contained about half as much Hf178 as DC Zircon and Procera Zirconia (means 7770 ppm vs 14800 ppm and 15800 ppm). Hafnium (Hf) is commonly found together with Zr. Since differences in the content of oxides might influence crystallic structure, this might have clinical consequences. The other elements were present in sub-ppm concentrations. It was possible to separate the three materials by principal component analysis into three distinct classes based on their element content. This indicates that the materials came from different sources. Conclusion: * Lava, DC Zircon and Procera Zirconia contains different amounts of the main elements Zr, Er and Hf. * The differences in the concentrations of the bulk elements might have clinical implications. * The other elements studied were present in sub-ppm amounts. * The materials probably had different sources.