Aim: This research was designed to evaluate the bonding potential of two low shrinking and one hybrid resin composites to both caries affected and sound dentin without and with pH cycling for 24 hours and 2 weeks.Methods: The restorative materials tested were Filtek P90, Filtek Z350XT and Filtek Z250. The occlusal surfaces of 108 carious human molars were ground flat to obtain caries affected dentin surrounded with sound dentin. The adhesive systems were applied according to manufacturers’ instructions then light cured followed by resin composite crown built up. The teeth were sectioned into beams and then divided into 3 groups in relation to pH cycling regimen: (1) control group; (2) pH cycling for 24 hours and (3) pH cycling for 14 days. The specimens were then subjected to microtensile bond strength testing. The mode of failure was examined using stereomicroscope. Nanoleakage was evaluated using Environmental Scanning Electron microscope.Results: caries affected dentin recorded lower microtensile bond strength values compared to sound dentin with all restorative materials used. All restorative material used gave lower microtensile bond strength values when subjected to pH cycling. Filtek P90 recorded the highest microtensile bond strength values when applied to caries affected dentin and when subjected to pH cycling. Nanoleakage evaluation revealed different nanoleakage pattern with different resin composite materials. Conclusions: Type of dentin substrate did influence the bond strength. Filtek P90 have improved the bonding performance to caries affected dentin. In addition, caries affected dentin interfaces are more prone to degradation than sound dentin.