Mental illnesses are among the most common debilitating diseases (
1) and are considered as the risk factors of oral health problems (
2). Today, more than 450 million people in the world have mental illnesses (
1,
2). They engage people at all economic, social, and national levels (
2,
3). The studies carried out in Iran show that the prevalence of such disorders varies between 10.8% and 21% (
1). Individuals with severe mental illnesses have a higher risk of oral illness as compared with healthy people, which is due to different factors such as type and severity of the illness, poor oral health, specific dental phobias, problem accessing healthcare centers, inappropriate diet, lack of personal understanding of oral care problems, and side-effects of psychiatric medications (
2). The psychological-social impacts of oral health problems affect the quality of life considerably; this affects eating, speaking, and social and psychological aspects of life (
2). Dental caries and periodontal diseases are the most common diseases engaging the oral health (
2,
4). Consumption of psychiatric medications reduces salivary flow rate and its buffering capacity and causes dental caries in the presence of a normal diet (
5). Dental treatment of these patients will be difficult due to lack of motivation, detachment, limited partnership, mobility problems, fear of treatment, poor adaptation to new prostheses, and financial considerations (
2). In addition, nursing staff of hospitals lack necessary knowledge, ability and incentive to provide conditions for oral heath cares of these patients (
5). Several studies were conducted on oral health care of patients with psychiatric disorders in Denmark (
6), Italy (
7), Spain (
8), India (
9), and Turkey (
10) and proved that the mental illnesses and the medications consumed for these diseases may increase the severity of dental illnesses, especially caries.