Interfacial characteristics of adhesive luting resins and composites with dentine

Purpose To evaluate the interfacial characteristics of five adhesive resin luting agents with dentine including tensile bond strength, failure mode, extent of demineralisation, morphological changes and hybrid layer formation. Materials and methods The products tested were Bistite II DC (BDC), C&B Super-Bond (CBM), M-Bond (MBD), Panavia-F (PAF) and Rely-X Unicem (RXU). For tensile bond strength measurements (TBS), metallic rods were bonded to standardised dentine surface areas (n = 10), thermal-cycled (3000× 5–55 °C, 4 cycles/min) and debonded at 1 mm/min crosshead speed. The failure mode was examined on dentine surfaces by LV-SEM (n = 10), whereas the thickness of the hybrid layer by HV-SEM (n = 4). FT-IR microscopy (n = 4) and ESEM (n = 4) were used to assess the extent of demineralisation and the morphological changes induced on dentine by the conditioning and priming treatments. Results TBS (MPa) values were BDC (13.01), MBD (9.19) and PAF (7.07) significantly different from CBM (4.79) and RXU (4.47). The percentage of debonded dentine area covered with resin showed the highest values in BDC (47.80) and MBD (38.12) significantly different from CBM (17.20), PAF (16.47), and RXU (16.50). The extent of demineralisation for CBM was 100%. No statistical differences were found among BDC (60.86%), MBD (60.22%) and PAF (51.99%). RUX (45.03%) showed the lowest value. CBM induced the most pronounced tubule funneling and intertubular dissolution, followed by PAF, BDC and MDB. RXU partially removed the smear layer without opening tubule orifices. The thickest hybrid layer was found in CBM (4.17 μm) followed by MBD (2.39 μm). No statistically significant differences were found between PAF (0.95 μm) and BDC (1.12 μm), whereas RXU showed no detectable hybrid layer. Significance Significant differences were found in the interfacial properties among the materials tested, that may lead to differences in their clinical performance.