The recent demand for dental devices which are easier to handle and offer higher levels of reliability and safety has led to the development in the US of Isolite Plus, a new oral support device. When placed in the oral cavity, Isolite Plus enables marking of the surgical field, secures the treatment space, ensures a vacuum, protects the cheek and tongue, assists in opening the mouth, prevents accidental ingestion/aspiration, ensures treatment without contamination and enhances comfort and safety during dental treatment. The present study was carried out to verify whether Isolite Plus can fit well in the mouth of Japanese people and to determine whether it performs adequately. Thirty resident dentists were required to wear Isolite Plus in their mouth and perform mutual simulation training using an air turbine handpiece. After the training, both subjects playing the role of surgeon and those playing the role of patient were asked to complete questionnaires. On the basis of the results, we discuss the clinical usefulness of Isolite Plus in Japanese people. In the present investigation, Isolite Plus was rated slightly better by surgeons than by patients. The supportive functions of the device were judged inadequate due to the poor fit of the mouthpiece portion of the device to subjects' mouth. For the distribution of Isolite Plus in the Japanese market, the mouthpiece portion of the device should be improved so that it can fit the mouth of Japanese people.