A 57-year-old patient complains about dental hypersensitivity to chemical stimuli, gum itch. Objectively: roots are exposed down to 1/3 of their length, gums are dense and pale rose. Wedge-shaped defects in the area of the 14, 13, 24, 25, 26, 34 teeth are within the dentine. Probing of dental cervixes and wedge-shaped defects is painfull. What is the most likely diagnosis?