A 30-year-old woman came to a dentist with complaints of discoloration of her t upper front tooth and food getting stuck between the teeth. Objectively, a carious cavity is observed on the mesial contact surface of tooth 12 within the mantle dentin. The walls and floor of the carious cavity are dense and pigmented. The dentinoenamel border is tender to probing. Thermal stimulus provokes no response. Percussion results are negative. Make the diagnosis.