The dentin surface treated with primer A + B and Bond A + B (CLB AB) revealed a dense bonding layer without any dentinal structures observed (10,000x, dotted line: 5 μm). Figure 2f: The SBMP-treated dentin surface revealed some porosities on some bonding layer areas (210x, dotted line: 100 μm), as well as a dense bonding layer among the porosities at high magnification (5000x, dotted line: 5 μm).