The answer is a simple no. Cavities in the teeth caused by dental decay cannot heal. Enamel which is affected by dental decay cannot heal as they are fully formed at the time of eruption and then on only deteriorates. The deeper part of the tooth which has dentin cannot heal the cavity formation, however it can produce a protective barrier between the advancing cavity front and the pulp inside. The cementum the third mineralised tissue of the tooth cannot heal a decay cavity. Its main function is to attach the tooth to the bony socket through the periodontal fibres.