Dentin Adhesion and Elastic Modulus of Adhesives Containing a Functional Monomer Having Polyethylene Glycol Chains

Abstract

 Purpose: The purpose of this study was to evaluate the dentin bond strength and elastic modulus of adhesives having polyethylene glycol chains.

 Methods: Flat dentin surfaces were made in non-carious extracted human molars using a diamond saw and 600-grit SiC paper. The surfaces were treated with one of the three one-bottle self-etch adhesives: CFA-2.0 (CFA), iGOS BOND (iGOS), and CLEARFIL S³ BOND ND Quick (NDQ), or a two-step self-etch adhesive; CLEARFIL MEGABOND (MB). The adhesives were applied to the surfaces, and a resin composite was incrementally built on the adhesive. Following 37°C water immersion for 24 h, the specimens were sectioned and subjected to micro-tensile bond strength tests. Four extracted human molars were used to evaluate the elastic moduli of the adhesives. Two mm-thick discs of the coronal dentin were cut and smoothened with 600-grit SiC paper. The four adhesives were applied to the surfaces, then five replicate applications of each adhesive were performed, with irradiation after each application. After 24 h storage in 37°C distilled water, the surfaces of the adhesive layers were assessed using a nanoindenter to determine the elastic modulus. In addition, the primer/adhesive-treated dentin was observed by SEM and the resin-dentin interface was ultra-morphologically characterized by TEM.

 Results: The bond strength of CFA was significantly higher than that of the iGOS and lower than that of MB. There was no significant difference between CFA and NDQ. The elastic modulus of CFA was significantly greater than those of iGOS and NDQ. There was no significant difference between the moduli of CFA and MB. SEM observations of the primer/adhesive-treated dentin confirmed that CFA partially demineralized the dentin surface. TEM revealed that a relatively thin hybrid layer was formed without noticeable demineralization and filler particles were dispersed in the adhesive layer of CFA.

 Conclusion: The bond strength of the adhesive CFA containing a functional monomer having polyethylene glycol chains was equivalent to that of the existing one-step adhesive NDQ containing functional monomer MDP. The bond strength and the elastic modulus were linearly correlated with a high correlation coefficient (0.9899).