Microtensile bond strength of different components of core veneered all-ceramic restorations.
OBJECTIVE
The present study aims to evaluate the core-veneer bond strength and the cohesive strength of the components of three commercial layered all-ceramic systems. Two surface treatments for the core surface finish and different veneering ceramics with different thermal expansion coefficients (TEC) were applied. The selected systems were two CAD-CAM ceramics; Cercon and Vita Mark II and one pressable system; (IPS)Empress 2 for layering technique.


METHODS
Standardized core specimens were fabricated according to the manufacturer's instructions, or polished with 1200 siliconcarbide polishing paper. The core specimens were veneered with either its manufacturer's veneer or an experimental veneer with higher TEC. The obtained micro-bars were subjected to the microtensile bond strength test. The obtained data were analyzed using one and two-way ANOVA. A finite element analysis (FEA) model of the test setup was analyzed. Scanning Electron Microscopy (SEM) was carried out at the fracture surface.


RESULTS
The core materials were significantly stronger than the veneering materials and the layered core-veneer specimens of which the results were statistically comparable. Polishing the core surfaces did not have an effect on the core-veneer bond strength. Experimental veneer with higher TEC resulted in massive fractures in both the core and veneering material. SEM and FEA demonstrated fracture pattern and mechanism of failure.


CONCLUSIONS
The core-veneer bond strength is one of the weakest links of layered all-ceramic restorations and has a significant role in their success. To exploit fully the high strength of zirconium oxide cores, further research work is needed to improve its bond with its corresponding veneering material.
Aboushelib
Moustafa N
MN
Department of Dental Material Science, Academisch Centrum Tandheelkunde Amsterdam, Universiteit van Amsterdam and Vrije Universiteit, The Netherlands. mabou@acta.nl
de Jager
Niek
N
Kleverlaan
Cornelis J
CJ
Feilzer
Albert J
AJ
D001672:Biocompatible Materials / Q000737:chemistry; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D017076:Computer-Aided Design; D003442:Crowns; D001840:Dental Bonding; D003775:Dental Polishing; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003801:Dental Veneers; D020342:Finite Element Analysis; D006801:Humans; D018020:Lithium Compounds / Q000737:chemistry; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D011176:Post and Core Technique; D017655:Silicon Compounds / Q000737:chemistry; D013499:Surface Properties; D013718:Tensile Strength; D013816:Thermodynamics
D001672:Biocompatible Materials; D017554:Carbon Compounds, Inorganic; C118557:Empress 2; D018020:Lithium Compounds; D017655:Silicon Compounds; C082340:Vita Mark II; D003776:Dental Porcelain; C022088:silicon carbide