Influence of different surface conditioning protocols on microtensile bond strength of self-adhesive resin cements to dentin

Abstract

According to manufacturers, bonding with self-adhesive resin cements can be achieved without any pretreatment steps such as etching, priming, or bonding. However, the benefit of saving time with these simplified luting systems may be realized at the expense of compromising the bonding capacity. The purpose of this study was to assess whether different dentin conditioning protocols influence the bond performance of self-adhesive resin cements to dentin. Flat dentin surfaces from 48 human molars were divided into 4 groups (n=12): 1) control, no conditioning; 2) H(3)PO(4), etching with 37% H(3)PO(4) for 15 seconds; 3) SEBond, bonding with self-etching primer adhesive (Clearfil SE Bond); and 4) EDTA, etching with 0.1M EDTA for 60 seconds. The specimens from each dentin pre-treatment were bonded using the self-adhesive cements RelyX Unicem, Maxcem or Multilink Sprint (n=4). The resin-cement-dentin specimens were stored in water at 37°C for 7 days, and serially sectioned to produce beam specimens of 1.0 mm(2) cross-sectional area. Microtensile bond strength (μTBS) testing was performed at 1.0 mm/min. Data (MPa) were analyzed by 2-way ANOVA and Tukey multiple comparisons test (α=.05). Fractured specimens were examined with a stereomicroscope (x40) and classified as adhesive, mixed, or cohesive. Additional bonded interfaces were evaluated under a scanning electron microscope (SEM). Cement-dentin μTBS was affected by the dentin conditioning approach (P<.001). RelyX Unicem attained statistically similar bond strengths to all pre-treated dentin surfaces. H(3)PO(4)-etching prior to the application of Maxcem resulted in bond strength values that were significantly higher than the other groups. The lowest μTBS were attained when luting Multilink Sprint per manufacturers' recommendations, while H(3)PO(4)-etching produced the highest values followed by Clearfil SE bonding and EDTA. SEM observations disclosed an enhanced potential of the self-adhesive cements to form a hybrid layer when applied following manufacturer's instructions. When evaluated self-adhesive resin cements are used, selectively etching dentin with H(3)PO(4) prior to luting results in the most effective bonding.