In the last decades the problem of professional responsibility of the doctors went through deep conceptual re-examination. Some criteria, both general and more technically legal, are presented in order to correctly evaluate the professional liability. Then some specific aspects of the object are examined, such as the damaging of the inferior alveolar nerve after dental extraction, the problems concerning dental prosthetics and implants as well as the questions about HIV infection, acquired by patients or collaborators of the dentist, in his office.