Background There is a relationship between cognitive function and dental health as cognitive impairment may lead to poor tooth brushing activities as well as poor dental care and use of medications. Method A cross sectional study was carried out on three hundred patients attending a geriatric clinic in Nigeria. The diagnosis of dementia was made using ICD 10 diagnostic criteria. Dental health was assessed using a dental chart that shows the number of teeth present and absent in the four quadrants of the mouth. Result Blessed Dementia Rating Scale (BDRS) and Instrumental Activities of Daily Living (IADL) showed statistical significant association with tooth loss. BDRS (p = 0.001), IADL (p = 0.007). There was positive correlation between tooth loss and BDRS. Pearson correlation = 0.19, p = 0.001. The mean number of tooth loss was significantly higher in patients with dementia compared to those without cognitive impairment. Conclusion The finding of higher tooth loss among people with dementia may support the evidence of ascending infection leading to inflammation in the brain might be responsible.