A 40-year-old patient complains about a long-existing fissure in the central part of red border of his lower lip. He has been smoking from the age of 16. Objectively: there is a deep 1,0 cm long fissure along the median line of red border of the lower lip, the fissure edges are bulgi-ngl. Characteristic quality of the fissure is its spontaneous healing, but after epi-thelization the fissure recurs. The patient was diagnosed with chronic fissure of the lower lip. Conservative treatment proved to be ineffective. Choose the most appropriate treatment method in this situation: