Alcohol and drug addiction is a widespread phenomenon among the general population that reaches global proportions. Despite numerous preventive approaches and programs, unfortunately the number of addicts is increasing each year. Addiction limits the normal functioning of an individual and his or her environment, as it manifests itself both orally and systematically on each addict's body. Oral hygiene is an important segment and an integral part of an individual's overall hygiene. There are minimal differences in oral hygiene maintenance between alcohol and drug addicts. Their oral hygiene is considered extremely bad and its consequence is a poor oral health. There is a higher risk for certain pathological conditions due to oral hygiene negligence. Therefore, addicts suffer regularly from: high caries prevalence, tooth staining, periodontal disease, including gingivitis and periodontitis and halitosis. If we take into account that abuse of alcohol and illegal drugs is a widespread phenomenon, it is highly probable that each doctor of dental medicine will encounter, in his or her working life, a certain number of patients who are current or former addicts. The dentist must have the necessary knowledge of addictions in order to recognize them. Furthermore, the dentist must inform the addicts about the importance of oral health, motivate them and should provide them with proper oral hygiene instructions.