A person with developmental disability have limited daily activities. For this reason, person with developmental disability needs support and guidance. The mental retardation services aim is that the mentally disabled can live a normal life among other people. Accordingly, understanding the developmental disability person is important. Maintaining the oral health of a person with mental disability requires multi- professional co-operation. The key to the oral health is dealing with the attending staff. The staff should have sufficient knowledge and skill for developing the oral health of disabled people. Oral health experts have an important role to increase the staff knowledge about mental disabilities oral diseases and prevention. Bachelor of thesis Ì s subject was carried out in cooperation with Tahkokankaan service centre. Thesis work was to study care staff Ì s knowledge of mental disability residents oral health as well as development needs of knowledge. Aim of this study is to increase the health care staff knowledge and skills of mentally retarded oral health. Study was carried out a quantitative study. Service center conducted a survey among health care staff. The questionnaire was answered by 45 staff member, the response rate was 33%. The data were analyzed using a webropol program. The survey found that the medical staff had little knowledge of the basic things of special groups in oral health. Staff however, thinks a person with mental disability Ì s oral health as an important issue, and feel they need more knowledge and skills about men- tally disable people oral health. The medical staff felt that the residents ability to cooperate, as well as mental retardation level were the reasons why cleaning was hard. The oral health of people with mental retardation plays an important role, because of the weakness of motor skills. The medical staff has important role in developmental disabilities daily oral cleaning.