Association between microtensile bond strength and leakage in the indirect resin composite/dentin adhesively bonded joint

Purpose: Develop a methodology to correlate microtensile bond strength (μTBS) and leakage within the same site of a specimen and evaluate the predominate debond and leakage pathways. Materials and methods: A Class II (MO) slot cavity was prepared in 37 extracted human molars and restored with indirect resin composite restorations. The restored teeth were thermocycled 300X between 5 and 55°C and then stained with silver. Two specimens per tooth were obtained by diamond saw sectioning for measurement of leakage (μm) and microtensile bond strength (MPa) at the gingival wall and then tested for association with regression analysis. Scanning electron microscopy techniques and energy dispersive spectroscopy (EDS) were used to evaluate the debond and leakage pathways. Results: Association between leakage and bond strength was not significant (t=1.31, p=0.198). All 74 samples debonded within the joint, predominantly at the hybrid layer-adhesive resin region with only one specimen including a small portion of resin cement in the debond pathway. Secondary and backscatter imaging and EDS analysis showed leakage in all samples that involved the hybrid layer. Conclusion: This study demonstrates a feasible method for evaluating leakage and bond strength at the joint interface within the same specimen.