Dense and ultra. ne alumina-zirconia composites (Al2O3-16 wt%ZrO2 and ZrO2-20 wt%Al2O3) are developed and characterized for load bearing prosthetic applications. The improvement of the ceramic/bone interface, namely of the ceramic bioactivity, is performed by a glass coating on the surface of the composites. A new composition is used to produce the glass powder, by melting at 1550 degrees C the mixture of oxide raw materials. The processing to obtain a homogeneous and adherent coating on the ceramic substrates is investigated: the optimal temperature for the glazing treatment is 1200 degrees C. The microstructure of the coating and of the ceramic/coating interface, the adhesion and some mechanical properties of the prepared glass and of the coating are analyzed. Besides, the in vitro bioactive responses, by incubation of osteoblast-like cells on the coated samples, are evaluated: positive results are confirmed after 24 h and 72 h. (C) 2009 Elsevier B. V. All rights reserved.