BACKGROUND: Previous studies have shown associations between periodontal disease and age-related cognitive impairment. However, little is known about the different cognitive functions that may be affected in patients with periodontal disease. METHODS: We reviewed the recent literature to better understand the bidirectional relationship between cognitive function and periodontal disease, and to explore the cognitive assessments that may be useful when investigating this relationship. We also reviewed the literature around improving periodontal health in older adults presenting with cognitive impairment, which may improve their cognition. RESULTS: There is a bidirectional relationship between periodontal disease and cognitive impairment. We also found that visuospatial function, attention, memory, and language are important cognitive domains that may be impaired in older people with periodontal disease, possibly because these factors are associated with the ability to adequately brush one's teeth. Furthermore, we noted that the choice of cognitive assessment may be particularly important when studying cognitive function in relation to periodontal health. To improve periodontal health in older people with cognitive impairment, partner-assisted interventions, adequate toothbrushing, and the use of a powered toothbrush have all been proposed. The early initiation of regular oral care visits, education for individuals, improving cooking skills, and dietary/caloric restrictions may also contribute to improving periodontal health. CONCLUSIONS: The bidirectional nature of the relationship between periodontal health and cognitive function is important for older adults presenting with cognitive impairment. Furthermore, improvements in periodontal health may help to improve cognitive impairment. The appropriate assessment of cognitive function will contribute to preserving and improving oral health in older people with periodontal disease.