Objective: To clarify the association between multiple tooth loss and dementia. Basic research design: Case-control study based on the claims data from National Health Insurance Research Database (NHIRD). Patients were divided into two groups: the dementia groups and non-dementia group. For each case patient, one control patient was randomly selected and frequency matched by age (per 5 years) and sex. The case group comprised patients newly diagnosed with dementia, and the index date was the the date of dementia diagnosis, which became the baseline for comorbidity and age calculations. Results: Among the 43,026 individuals, patients with dementia had a significantly higher extraction density at ages 60–69 (p < 0.0001) and 70–79 (p = 0.04) years compared with control patients. Conclusions: This population-based retrospective study demonstrated an association between tooth loss and dementia. Patients in Taiwan with more tooth extraction experience are likely to have an increased risk of dementia. Keywords: Tooth loss; dementia; cognitive impairment