Analysis of the interface zirconia/coating ceramic after different surface treatments and aging, by means of structural characterization and bond strength

Abstract

Obtaining a durable union of zirconia/coating ceramic interface is a concern for clinical success of metal-free restorations. However, evidences indicate that a technique with better predictability and durability has not been determined yet. To increase the bonding strength between zirconia and coating ceramic, and consequently reduce the incidence of shear fractures during the prosthesis life, several surface treatments have been proposed for zirconia, before the coating process. A new method of zirconia surface treatment through the deposition of thin films by non-thermal plasma is progressing on researches in order to obtain better knowledge and results. Thus, this study aims to characterize the topography of zirconia discs without treatment (control) and submitted to different surface treatments (airbone-particle abrasion with 110¼m aluminum oxide particles, airbone-particle abrasion with 250¼m aluminum oxide particles, liner and non-thermal plasma), through the analysis of surface roughness (Ra, Rq, Rt e Rz), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) associated with Energy Dispersive Spectroscopy (EDS), surface energy and contact angle (SE) and to evaluate the bond strength between zirconia (with and without surface treatments) and coating ceramic , after 24 hours of storage in distilled water at room temperature (initial period) or after aging (after 12.000 cycles of thermal cycling at a temperature ranging from 5 to 55pC). The null hypothesis will be that none of the different surface treatments will promote alterations neither in the surface characteristics of Y-TZP nor in bond strength values between the this ceramic and the coating, regardless aging. For this, 156 zirconia specimens will be prepared with 20mm in diameter and 4mm in thick. The specimens will be randomly divided into 5 groups according to the treatment surface: control/untreated (G1), airbone-particle abrasion with 110µm aluminum oxide particles (G2), airbone-particle abrasion with 250¼m aluminum oxide particles, (G3) the application of zirconia liner (G4) and non-thermal plasma (G5). Fifty six specimens will be used to analyze the topography of zirconia discs characterization, before and after surface treatment through the analysis of surface roughness (Ra, Rq, Rt e Rz), atomic force microscopy (AFM), scanning electron microscopy (SEM) associated with energy dispersive spectroscopy (EDS), surface energy and contact angle (SE), being randomly distributed in the four proposed groups (n=14). To perform the bond strength tests, the coating ceramic will be applied on the 100 remaining zirconia specimens, which will also be randomly distributed in the five proposed groups, and subsequently subdivided according to storage condition (n=10). The surface roughness and surface energy values will be compared before and after the proposed treatments. The values obtained through bond strength tests and failure classification will be compared between the different groups, before and after the aging period. Data will be submitted to the adherence test to the normal curve, being applied appropriate statistical analysis to compare the mean values of the specimens. The Atomic Force Microscopy (AFM) and Scanning Electron Microscopy associated with Energy Dispersive Spectroscopy (SEM/EDS) will be performed in one specimen o each group, since these tests provide only a qualitative analysis of specimens surface and visual comparison between the different groups and periods proposed. (AU)