Bi-colored zirconia as dental restoration ceramics
2013 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 39, no 8, 9277-9283 p.Article in journal (Refereed) Published
Machinable zirconia blocks with gradient colors are fundamental for fabrication of full-contour esthetic dental restorations. The aim of this study was to process and evaluate bi-colored zirconia ceramics as a pilot dental material by using well-established techniques. Two commercially available partially stabilized zirconia granules, one undoped and one doped with 0.202 wt% Fe2O3, resulted in white and yellow colors after sintering, respectively. Bi-colored zirconia was fabricated by two-step dry pressing of both zirconia granules one above the other to form green bodies, followed by cold isostatic pressing (CIP) and, a two-step pressureless sintering finally at 1450 degrees C. The dilatometer results showed that the Fe2O3 doped zirconia sintered slightly rapid, but the difference of shrinkage between two powders was <1%. Sintered bars achieved full density, 6.018 g/cm(3) (similar to 99%TD), without cracks in the similar to 1 mm color gradient zone. The microstructures were characterized by scanning electron microscopy (SEM) and careful observation of both surface and interior provided no obvious structural difference of either grains or pores among the three distinct regions, comprising white, yellow and color gradient zone. Vickers hardness of hi-colored zirconia was similar to 13.1 GPa, with no obvious difference in the three regions. The four-point bending strength of the hi-colored zirconia bars was 745.5 +/- 159.6 MPa, which appeared noticeably lower than that of the single-colored references being above 1000 MPa. Fractographic analysis revealed that in most of the cases (60%) the fracture was initiated at the color gradient zone, where large voids with high coordination numbers, agglomerates with critical size and concentration of irregular grains with porous surfaces were observed. Above all, bi-colored zirconia ceramics prepared by the improved technique could meet the basic requirements of dental materials. The ways of minimizing the defects within hi-colored blocks should be developed for the production of esthetic zirconia ceramics of high strength and reliability.
Place, publisher, year, edition, pages
2013. Vol. 39, no 8, 9277-9283 p.
Pressing, Color, ZrO2, Biomedical application
IdentifiersURN: urn:nbn:se:su:diva-96864DOI: 10.1016/j.ceramint.2013.05.036ISI: 000325835100096OAI: oai:DiVA.org:su-96864DiVA: diva2:668289
FunderVinnovaSwedish Research Council
China Scholarship Council (CSC); Swedish Innovation System (Vinnova); Swedish Research Council (VR) through Berzelii Center EXSELENT2013-11-292013-11-282013-11-29Bibliographically approved