Objectives: To help alleviate the shortage of reliable information on clinical care issues, the Spanish Observatory of Dental Patient Safety (OESPO) has resorted to the study of legal claims by patients, and searched those which produced clinical problems. Methods: Based on OESPO data, this paper proposes eleven basic procedures/practices for dental patient safety to help mitigate most preventable adverse events. Results: The sample of the OESPO is large (415 adverse events studied), but it has the bias of a judicial source. However the results provide an interesting approach to clinical safety in dentistry. When studying in detail the causes which led to preventable adverse events, it can be seen that most of these (and most severe) events have been caused by a small number of erroneous behaviours. Conclusions: Most preventable adverse events during the dental health care are produced by a relatively small number of causes. Therefore, a few basic safety procedures can reduce significantly these preventable adverse events.