BACKGROUND: The authors conducted a study to determine one-year coronal and root caries increments in patients newly diagnosed as having Alzheimer disease (AD), other dementia (OD) or no dementia. METHODS: The authors recruited patients from two hospital memory clinics in Copenhagen. The oral examination included an assessment of dental status and dental caries. The authors used a structured questionnaire to obtain information regarding demographic, social and functional variables. RESULTS: In the baseline study, 106 dentate patients participated. Of these, 77 completed the follow-up study. The participants' mean age was 81.9 years at baseline and 82.5 years at follow-up. At baseline, 87 (82 percent) of 106 participants had dementia and at follow-up, 64 (83 percent) of 77 participants had dementia. The mean number of decayed tooth surfaces was significantly higher at follow-up than at baseline for all participants, and the number was highest for the OD group. The one-year adjusted caries and filling increments (ADJCIs) were high for participants with and without dementia but were highest for participants in the AD and OD groups. Baseline risk factors for developing elevated coronal and root ADJCIs included having caries, having many teeth and being older than 80 years. CONCLUSIONS: Elderly people referred to a memory clinic were at an elevated risk of developing high levels of coronal and root-surface caries during the first year after referral, and those with a dementia diagnosis other than AD appeared to be at a particularly high risk of developing multiple carious lesions during the first year after diagnosis. CLINICAL IMPLICATIONS: These findings underscore the importance of addressing the oral health needs of elderly people suspected of having experienced cognitive decline.