A 40-year-old male patient complains of a long-existing fissure in the central portion of the vermilion border of his lower lip. The patient has been a smoker since the age of 16. Along the midline of the vermilion border of the lower lip there is a deep fissure up to 1,0 cm long with the rolled edges. The fissure heals spontaneously, but recurs soon after epithelialization. The patient was diagnosed with chronic lower lip fissure. Conservative treatment proved to be ineffective. Select the most efficient method of treatment: