We have investigated the association of oral health with development of dementia in elderly Koreans. Data for subjects aged ≥65 years who underwent regular National Health Insurance Service check-ups and received dental care in 2017 were analysed. Those treated for dementia in 2017 served as the dementia group and those with no record of dementia in 2002-2017 as the control group. Explanatory variables were sex, age, household income, place of residence, smoking status, alcohol consumption, and presence of diabetes mellitus and hypertension, periodontitis, and removable dentures. Regression analysis showed that dementia was significantly more common in women than in men and in those aged ≥81 years than in those aged 65-70 years. The risk of dementia was highest in the 'upper-middle' income group and in the rural population. Smokers and those who consumed alcohol were less likely to develop dementia. Subjects with diabetes were more likely to have dementia than those without it, as were those with hypertension. Dementia was less likely in subjects with periodontitis and more likely in those with removable dentures. Therefore, loss of teeth may contribute to development of dementia.