Chemomechanically treated dentin has been reported to enhance dentinal bonding. This was evaluated in vitro in 96 mixed Class V restorations. Thirty-two cavities were prepared mechanically only and had bevels in enamel and butt joints in dentin, and 32 cavities were further treated chemomechanically for 10 minutes, while 32 carious lesions were excavated only chemomechanically and had bevels in enamel and dentin. Eight identically prepared cavities from each preparation group were assigned to each one of four different bonding techniques and restored accordingly Restoration quality was assessed for margins in enamel and dentin separately and quantitated as percentage of excellent margin before and after thermal cycling and degree of dye penetration. C'hemomechanical preparation procedures did not provide better results than the ordinary mechanical preparation. In addition, the chemoinechanical preparation procedures were time-consuming and resulted in ragged cavity margins.