Innovations in zirconia resin-composite bonding systems

Objectives: The aim of this work was to evaluate an innovative bonding concept, the combination of selective infiltration etching treatment (SIE) and engineered zirconia primers on the zirconia resin-composite bond strength.

Methods: Zirconia discs (Procera, NobelBiocare) received SIE as a surface treatment while ‘As-sintered' surface served as a control. The bonding surface was the coated with 4 engineered zirconia primers which contained one of one of the bi-functional silane monomers: acrylatesilane, isocyanatesilane, styrylsilane, and methacrylatesilane (all from ABCR and Toray Silicone). The chemical activation of zirconia primers before their use was investigated using Fourier Transformation Infra-Red (FTIR) spectroscopy. Pre-aged resin-composite discs (Tetric IvoCeram) were bonded to the zirconia discs (Panavia F 2.0). The zirconia-resin bond strength was evaluated using microtensile bond strength test (MTBS). The tested microbars (n=20) were examined under a scanning electron microscope (SEM) to assess failure type.

Results: ANOVA revealed significant differences between the surface treatments (P<0.0001), the zirconia primers (P<0.0001), and the interaction between the surface treatment and the used zirconia primers (P<0.0001). ‘As-sintered' specimens demonstrated spontaneous interfacial failure mode. SIE-treated specimens demonstrated higher MTBS values (28-41 MPa) with predominantly cohesive failure mode. All zirconia primers became activated within 1 h according to the FTIR spectroscopic analysis, after which they were used.

 

Zirconia primers (reactive monomer)	Surface treatment	MTBS (MPa)	SD (MPa)
1% Methacrylatesilane in ethanol	SIE	40.6	5.8
	As-sintered	2.6	3.1
1% Acrylatesilane in ethanol	SIE	31.2	4.4
	As-sintered	3.1	2.4
1% Isocyanatesilane in ethanol	SIE	32.4	3.9
	As-sintered	2.9	2.8
1% Styrylsilane in ethanol	SIE	28.0	2.2
	As-sintered	2.8	2.7

Conclusions: The combination of selective infiltration etching and engineered zirconia primers significantly improved the zirconia resin bond strength.