The case report is an illustration of the medical paradigm of treating dental caries over a 20-year period. Lesions are not being "watched," but rather modern medical principles are used to treat incipient caries, monitor caries risk and preserve tooth structure.
Dr. Urbans statement that tooth no. 13 had a pulp cap is unsupported by evidence. It was one of several teeth that required operative intervention because tooth structure was lost to advancing caries, and there is little likelihood that tooth no. 13 will ever be lost. For most lesions in this case, subtle early changes in hard tissue were treated by remineralization.
Consider how much tooth structure has been saved by not cutting and weakening these teeth. By communicating an understanding of the caries process to the patient, much of the natural dentition has been preserved.