Causal relationship of impacts. To increase the usefulness of the OIDP for assessing specific treatment needs,
additional questions have been asked about the perceived causal symptoms and impairments of any impact on performance.
Respondents who perceived any impact were asked whether the major cause of their problems was from pain, discomfort, limitation in function, dissatisfaction with appearance or other problems.
Then they were asked to specify the oral impairments, such as toothache, loose tooth, gum abscess or bad breath, which they perceived caused their problems. The methods and results have been described elsewhere.