This study was carried out to evaluate the effect of resin composite application techniques either bulk or incrementally fill, of class II cavities with different regional dentin with and without load cycling on the microtensile bond strength of resin-dentin. In addition the ultramorphology of resin-dentin interface was examined using scanning electron microscope. A total of sixty extracted caries free third human molars were selected for this study; for preparing 180 specimens for testing the microtensile bond strength. Molars were prepared to receive standardized class II cavities and then the adhesive system was applied according to manufacturer instruction. Resin composites were applied either in bulk or incrementally. All specimens were sectioned to obtain sticks of 0.1mm2 0.05 thickness and were subjected to microtensile bond strength testing. Microtensile bond strength (µTBS) values were recorded tabulated and statistically analyzed. It was concluded that resin composite application technique might have no impact on the adhesion of the resin composite. The morphological and structural variations in dentin influence the bond strengths. Resin-dentin bond were prone to deterioration after cyclic loading.