Effect of different surface treatments on the hydrothermal degradation of a 3Y-TZP ceramic for dental implants

Objectives. Implant surface modifications are intended to enhance bone integration. The objective of this study was to assess the effect of different surface treatments on the resistance to hydrothermal degradation, hardness and elastic modulus of a 3Y-TZP ceramic used for dental implants. Methods. Samples grouped according to their surface morphologies (AS, as-sintered; C, coated; P, dry-polished; R, roughened; PA, polished and annealed; RA, roughened and annealed) were subjected to accelerated hydrothermal degradation (LTD) by exposure to water steam (134 degrees C, 2 bars) for 100 h. The t-m phase transformation was quantified by grazing incidence X-ray diffraction (GIXDR) and by combined focused ion beam and scanning electron microscopy (FIB-SEM). Elastic modulus and hardness before- and after prolonged aging (100 h) were assessed by nanoindentation. Results. AS and C specimens presented a better resistance to hydrothermal degradation than P and R samples. After prolonged aging, the depth of the monoclinic transformed layer ranged from 11 mu m to 14 mu m. Hydrothermal degradation led to a significant decrease of elastic modulus and hardness. Signcance. Surface treatments affected the resistance to hydrothermal degradation of the 3Y-TZP ceramic. Dry mechanical surface modifications should be avoided since a high t-m transformation rate associated to the initial monoclinic content was observed. Annealing was useful to reverse the initial t-m transformation, but did not improve the resistance to hydrothermal degradation. (C) 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.