Tensile Bond Strength of a So-called Self-adhesive Luting Resin Cement to Dentin

Purpose: The purpose of the study was to evaluate the bond strength and durability of a so-called self-adhesive resin luting cement to human dentin. In addition, the influence of a dentin adhesive system on the bond strength was tested. Materials and Methods: Forty-eight dentin disks from human teeth were divided into two groups of 24 specimens. One group was bonded to composite resin tubes with the self-adhesive luting cement (RelyX Unicem Aplicap, 3M ESPE), in the other group the dentin surfaces were conditioned with a three-step dentin adhesive system (OptiBond FL, Kerr) prior to bonding with the same cement. Three subgroups of eight specimens each were tested for tensile bond strength following storage in 37°C tap water for either 3 days or for 150 days with an additional 37,500 thermal cycles either between 20°C and 40°C ("soft TC") or between 5°C and 55°C ("hard TC"). Statistical analyses were performed with the Shapiro-Wilk test, Levene's test, two-way analysis of variance (ANOVA) followed by multiple comparisons with the Scheffé test. Results: Without the dentin adhesive, the mean tensile bond strengths after 3 days were 7.1 ± 3.8 MPa; after 150 days/"soft TC" 6.8 ± 3.6; and after 150 days/"hard TC" 5.3 ± 4.5 MPa. With the dentin adhesive, the mean bond strengths after 3 days were 16.5 ± 5.5 MPa; after 150 days/"soft TC" 13.1 ± 3.9 MPa; and after 150 days/"hard TC" 10.1 ± 5.2 MPa. Conclusion: Regardless of storage conditions, the use of a dentin adhesive increased the tensile bond strength of a self-adhesive resin luting cement significantly in comparison to the use of the luting cement without adhesive. Keywords: tensile bond strength, RelyX Unicem, self-adhesive resin, dentin bonding