Do intact collagen fibers increase dentin bond strength?

The purpose of the present study was to evaluate surface morphology and shear bond strength of All Bond 2 bonded to dentin surfaces, that were treated progressively to remove collagen fibers. For the study of surface morphology, fifteen teeth were divided in to five groups. Dentin surfaces in groups 1-4 were etched either with 24% EDTA for 30 seconds or 32% phosphoric acid for 15 seconds with and without subsequent treatment with 10% NaOCl for 60 seconds. Group 5 received no treatment and served as control. Evaluation was performed using scanning electron microscopy. Thirty teeth were used for the shear bond strength test. Two experimental surfaces were prepared on each tooth and cylindrical copper matrixes were attached to the surfaces. Experimental surfaces were divided into four groups and treated in the same way as group 1-4 in the morphology part of the study. Dentin was bonded with All Bond 2, after which a flowable composite was inserted and light cured. Shear strength test was performed at a crosshead speed of 1 mm/minute until the composite debonded. Results showed that etching followed by treatment with NaOCl removed all collagen fibers from the dentin surfaces, while treatment with EDTA alone denuded the fiber structures. Shear strength was significantly decreased when surfaces were treated with NaOCl. The highest shear strength values were obtained in the EDTA etched group. The results from the present study indicate that exposed dentin associated collagen fibers increases adhesion of All Bond 2 to dentin.