In vitro evaluation of the Long-term bond strength of two resin cements to enamel and dentin

In this in vitro study، the long-term bond strength of a self-adhesive resin cement and conventional resin cements to human enamel and dentin was compared.

80 sections of intact human third molars were randomly assigned into eight groups according to the cement type [Rely X Unicem (RXU)، Rely X ARC (RXA)]، bond substrate (enamel، dentin) and the duration of water storage (24 h or 1 year). Rods of cements (0. 75×1 mm) were prepared on the top surface of specimens using Tygon tubes. The micro-shear bond strengths of specimens were measured by a micro-tensile tester. Data were analyzed using Wilcoxon signed ranks and Mann Whitney tests (α =0. 05).

The bond strengths of RXA and RXU cements to enamel after 24h were 18. 56±4. 08 MPa and 14. 99±4. 17 MPa، and after 1 year were 19. 41±6. 24 MPa and 15. 51±6. 17 MPa، respectively. The bond strengths of RXA and RXU cements to dentin were 13. 36±4. 02 MPa and 14. 16±4. 69 MPa after 24h، and 14. 63±5. 96 MPa and 14. 08±6. 72 MPa after 1 year، respectively. Tooth substrate had significant effect only on the shear bond strength of RXA cement after 24h (P=0. 01)، while no other significant differences were found in this study (P>0. 05).

According to the results of this study، one-step self-adhesive and multi-step conventional resin cements were similarly effective in bonding to enamel and dentin after 1 year water storage.