Effectiveness of self-adhesive luting cements in bonding to chlorhexidine-treated dentin

Objectives. The aim was to investigate the microtensile bond strength (mu-TBS) and failure pattern of self-adhesive luting cements (SLC) to dentin pre-treated with different concentrations of chlorhexidine (CHX) solutions. Methods. The occlusal enamel was removed from 30 extracted sound human molars in order to expose a flat dentin. Resin-composite (Filtek Z250, 3 M ESPE) discs (12 mm in diameter, 6.0 mm thickness) were cemented to the smear layer-covered dentin using the SLC [RelyX U100, 3 M ESPE (U100); Multilink Sprint, Ivoclar Vivadent (MS)] with 0.2% or 2.0% CHX solutions. Results were compared with the control, untreated dentin. Six groups were then created based on the SLC and dentin pre-treatment (n = 5). After 24 h of water storage, restored teeth were serially sectioned into beams with a cross-sectional area of 0.8 mm(2) at the bonded interface. Subsequently, specimens were tested in tension with a crosshead speed of 0.5 mm/min in a universal testing machine, and the failure patterns were classified. Two-way ANOVA and Tukey's tests were performed (alpha = 0.05). Additionally, 18 teeth were subjected to energy-dispersive X-ray spectroscopy (EDS) analysis and micromorphology characterization of the smear layer-covered dentin and 0.2% or 2.0% CHX-treated dentin surfaces. Results. The mu-TBS obtained for both control groups were significantly higher, regardless of the CHX concentration and/or the cement used. Bond strengths were significantly higher for U100 than for MS, except when 2.0% CHX was applied. Fractographic analysis indicated that most failures in the control groups occurred cohesively in the SLC. Pre-treated dentin with 0.2% and 2.0% CHX solutions presented higher incidences of adhesive failures. EDS/SEM analysis exhibited varied concentrations of chlorine ions and crystal-shaped precipitates, depending upon the CHX concentration. Significance. Pre-treatment of dentin with 0.2% or 2.0% CHX adversely affects the bonding efficacy when associated with the SLCs tested. (C) 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.