140 human molar crowns were used after separating them from their roots at the cementoenamel junction with a water-cooled, low-speed diamond saw (Mecatome T201 A, Presi, Grenoble, France). The roots were discarded, and the crowns were randomly assigned into two groups: 70 samples for testing bond strength to enamel, and 70 for evaluating adhesion to dentin. To prepare enamel surfaces, a 0.5 mm-deep flat area was created in the center of the buccal surface of each crown using the cutting machine mentioned above. Each crown was then embedded in acrylic resin blocks (Acropars, Marlic Medical Industries Co., Tehran, Iran), positioning the buccal surface facing upward and level with the base. The enamel was polished gently with 320-grit silicon carbide abrasive paper (Starcke GmbH & Co. KG, Melle, Germany) to ensure surface uniformity. Enamel quality and flatness were examined using a stereomicroscope (Stemi 305, Carl Zeiss AG, Oberkochen, Germany). For the dentin group, the occlusal enamel and superficial dentin layers were removed to expose flat mid-coronal dentin using the same saw, under continuous water cooling. The dentin surfaces were also embedded in acrylic blocks with the surface aligned parallel to the base. A smear layer was created by polishing the exposed dentin for 60 s with 320-grit silicon carbide paper. Finally, the surfaces were rinsed and lightly dried using an air–water spray syringe (DABI Atlante, São Paulo, Brazil). Before bonding the RMGIC to the prepared enamel and dentin surfaces, a conditioning step was performed using GC Cavity Conditioner (GC Corporation, Tokyo, Japan) in accordance with the manufacturer's guidelines. The conditioner was applied to the tooth surface using a cotton pellet or applicator sponge. It was allowed to react for 10 s, after which the surface was thoroughly rinsed with water and gently blotted dry, leaving the surface moist but not desiccated. generate a image for this matter

140 human molar crowns were used after separating them from their roots at the cementoenamel junction with a water-cooled, low-speed diamond saw (Mecatome T201 A, Presi, Grenoble, France). The roots were discarded, and the crowns were randomly assigned into two groups: 70 samples for testing bond strength to enamel, and 70 for evaluating adhesion to dentin. To prepare enamel surfaces, a 0.5 mm-deep flat area was created in the center of the buccal surface of each crown using the cutting machine mentioned above. Each crown was then embedded in acrylic resin blocks (Acropars, Marlic Medical Industries Co., Tehran, Iran), positioning the buccal surface facing upward and level with the base. The enamel was polished gently with 320-grit silicon carbide abrasive paper (Starcke GmbH & Co. KG, Melle, Germany) to ensure surface uniformity. Enamel quality and flatness were examined using a stereomicroscope (Stemi 305, Carl Zeiss AG, Oberkochen, Germany). For the dentin group, the occlusal enamel and superficial dentin layers were removed to expose flat mid-coronal dentin using the same saw, under continuous water cooling. The dentin surfaces were also embedded in acrylic blocks with the surface aligned parallel to the base. A smear layer was created by polishing the exposed dentin for 60 s with 320-grit silicon carbide paper. Finally, the surfaces were rinsed and lightly dried using an air–water spray syringe (DABI Atlante, São Paulo, Brazil). Before bonding the RMGIC to the prepared enamel and dentin surfaces, a conditioning step was performed using GC Cavity Conditioner (GC Corporation, Tokyo, Japan) in accordance with the manufacturer's guidelines. The conditioner was applied to the tooth surface using a cotton pellet or applicator sponge. It was allowed to react for 10 s, after which the surface was thoroughly rinsed with water and gently blotted dry, leaving the surface moist but not desiccated. generate a image for this matter