Bonding efficacy of a self-adhesive resin cement to enamel and dentin

With the objective to evaluate the bonding efficacy of a new self-adhesive resin cement (RelyX Unicem, 3M ESPE) to enamel and dentin using a shear bonding strengths test with or without acid etching pretreatment, flat buccal dentin surface and mesial/distal enamel surface were made using a high-speed diamond bur. Copper rings were luted using Rely X Unicem (RU; 3M ESPE), Panavia F (PF; Kuraray) or Vitique (VI; DMG). For RU, the shear bonding strengths using GL (Gluma Etch, Heraeus) acid etching pretreatment were also tested. The teeth were placed into copper rings (inner diameter: 16mm, height: 4mm) and embedded in methylmethacrylate resin. The specimens were stored for 24h in distilled water at 37 °C prior to shear bonding strengths testing. In addition, bond failures were examined by optical microscope and categorized as 4 models such as different adhesive, cohesive, or mixed. Shear bonding strengths were calculated by dividing the maximum debonding force over the cross sectional area of each specimen. The Kruskal-Wallis test was used to determine pairwise statistical differences (P < 0.05) in SBS between the experimental groups. For dentin bonding strength, statistical analysis showed that there was no significant difference among RU (12.84 MPa), PF (14.93 MPa) and VI (11.03 MP); and the bonding strengths of them were higher than RU with acid etching pretreatment (9.12 MP). When bonded to enamel, PF (17.99 MP) and VI (17.58 MP) scored significantly higher than RU efficacy. The use of self-adhesive cement RelyX Unicem can obtain the bonding strengths to dentin similar to traditional resin cements. Phosphoric acid etching can improve the bonding strengths of the self-adhesive resin cement to enamel, but was negative for dentin.