This study of 230 hospital geriatric clinic patients compared the oral health of individuals with dementias with that of persons with no dementing illnesses. Data collected included dental examinations, subject questionnaires and review of hospital records. There were few differences among groups of patients based on categorization into groups of those diagnosed with (1) no dementia, (2) dementia of the Alzheimer's type, and (3) other dementias. However, there were significant differences based on degree of cognitive impairment regardless of dementia diagnosis. Those with severe dementia had poorer gingival health and oral hygiene, but better self-perceived mouth health. There are numerous limitations and inherent difficulties in studies involving persons with dementia, and overcoming these in the future will likely require long-term, interdisciplinary approaches.