In this study, posterior human extracted teeth were used. The teeth were thoroughly inspected for caries, cracks, fluorosis, abrasion facets, and damage from extraction and 40 teeth were selected. Samples were thoroughly washed and stored in dark glass containers in 1% (v/v) thymol solution at 4°C after extraction and used within 2 months. IsoMet 2000 Precision Saw (Buehler, Ltd., Lake Bluff, IL, USA) used to cut the roots below the furcation. Mesiodistal sectioning of the teeth crowns was performed, and both buccal and lingual surfaces were used for this study. Sectioned samples were mounted in acrylic resin mold where the sectioned surface was positioned facing the resin. The samples were then divided randomly into two groups with half of the sample surfaces being subjected to enamel roughening with 600‐grit disk (Automata Grinding and Polishing Unit; Jean Wirtz GmbH, Dusseldorf, Germany) and continuous air–water irrigation to resemble simple cavity preparation in enamel. The other half of the samples were subjected to different grits of abrasive disks (320‐grit/400‐grit/and 600‐grit) to get rid of the enamel layer and expose the dentin (Automata Grinding and Polishing Unit). The ground samples were then placed in an ultrasonic machine (Sonicer; Yoshida Dental Mfg. Co., Ltd., Osaka, Japan) filled with distilled water for 15 min to remove the enamel debris. To confirm complete enamel removal specimens were examined under a light microscope (Stereo 80 Widefield Microscope; Swift Optical Instruments, Schertz, TX, USA). Finally, the samples were randomly divided into two groups—in the enamel group (E), the bonding was performed on the enamel, whereas in the dentine group (D), the bonding was performed on the dentin. These groups were further divided randomly into two subgroups per the kind of etching used: either phosphoric acid etching (EA and DA) or Er,Cr:YSGG laser conditioning (EL and DL) with 20 samples in each subgroup. All the materials and equipment utilized in this study were applied per the manufacturers' instructions.