Effects of light penetration and smear layer removal on adhesion of post-cores to root canal dentin by self-etching adhesives

Objectives. This study investigated the effects of light penetration and removal of smear layer on the adhesive properties of self-etching adhesives to root canal dentin when using fiber posts. Methods. Altogether 54 human incisors and premolars were decoronated, and the roots after preparing the post space were randomly assigned into six groups. Three groups were treated with a light-cured self-etching adhesive and the other three with a dual-cured self-etching adhesive. In a further sub-division, the first group was light-cured with an irradiation unit; the second was light-cured with the irradiation unit and a light-guiding attachment; and the third was light-cured with the irradiation unit and the attachment after removing smear layer by EDTA and NaOCl. Then, a glass-fiber post was luted into the post space by a dual-cured composite. After 24 h, an hourglass-shaped specimen was trimmed and subjected to MTBS testing. Results. Using the light-guiding attachment and removing the smear layer reduced the incidence of pre-testing failure significantly from 57.1% to 19.0% (p < 0.05) in the light-cured adhesive groups and from 68.3% to 3.2% (p < 0.01) in the dual-cured adhesive groups. The MTBS in different locations within a post space were in the range from 8.9 to 17.5 MPa in the light-cured group and from 11.2 to 17.2MPa in the dual-cured group. Significance. Better light penetration in post spaces and removal of the smear layer are effective in improving the adhesive properties of self-etching adhesives to root canal dentin when using fiber posts. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.