The effect of nano-structured alumina coating on resin-bond strength to zirconia ceramics.
OBJECTIVE
The aim of this study was to functionalize the surface of yttria partially stabilized tetragonal zirconia ceramics (Y-TZP) with a nano-structured alumina coating to improve resin bonding.


METHODS
A total of 120 densely sintered disc-shaped specimens (15.5+/-0.03 mm in diameter and 2.6+/-0.03 mm thick) were produced from biomedical-grade TZ-3YB-E zirconia powder (Tosoh, Tokyo, Japan), randomly divided into three groups of 40 and subjected to the following surface treatments: AS - as-sintered; APA - airborne-particle abraded; POL - polished. Half of the discs in each group received an alumina coating that was fabricated by exploiting the hydrolysis of aluminium nitride (AlN) powder (groups AS-C, APA-C, POL-C). The coating was characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The shear-bond strength of the self-etching composite resin (RelyX Unicem, 3M ESPE, USA) was then studied for the coated and uncoated surfaces of the as-sintered, polished and airborne-particle abraded specimens before and after thermocycling (TC).


RESULTS
The SEM/TEM analyses revealed that the application of an alumina coating to Y-TZP ceramics created a highly retentive surface for resin penetration. The coating showed good surface coverage and a uniform thickness of 240 nm. The resin-bond strength to the groups AS-C, APA-C, POL-C was significantly higher than to the groups AS, APA and POL, both before and after TC (p< or =0.05). During TC all the specimens in the POL and AS groups debonded spontaneously. In contrast, the TC did not affect the bond strength of the AS-C, POL-C and APA-C groups.


CONCLUSIONS
A non-invasive method has been developed that significantly improves resin-bond strength to Y-TZP ceramics. After surface functionalization the bond survives thermocycling without reduction in strength. The method is relatively simple and has the potential to become an effective conditioning method for zirconia ceramics.
Jevnikar
Peter
P
Department of Prosthodontics, Medical Faculty, University of Ljubljana, Hrvatski trg 6, Ljubljana, Slovenia. peter.jevnikar@mf.uni-lj.si
Krnel
Kristoffer
K
Kocjan
Andraz
A
Funduk
Nenad
N
Kosmac
Tomaz
T
D000537:Aluminum Oxide; D020099:Coated Materials, Biocompatible; D001840:Dental Bonding; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D006358:Hot Temperature; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D049329:Nanostructures; D011897:Random Allocation; D019279:Resin Cements; D033081:Shear Strength; D013499:Surface Properties; D015019:Yttrium; D015040:Zirconium
D020099:Coated Materials, Biocompatible; C483701:Rely X Unicem; D019279:Resin Cements; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium; D000537:Aluminum Oxide