A 30-year-old woman complains of a carious cavity in the 16 tooth, food retention in the gap between the 16 and 17 teeth. During examination there was detected a carious cavity within mantle dentin with wide opening on the approximal-medial surface of the 16 tooth. The cavity floor and walls are pigmented, dense, painless on probing. Percussion of the 16 tooth is painless. On thermodiagnostics a short-term reaction can be observed. Make the diagnosis: