The oral health status of elderly dependent residents is reported to be poor, as well as difficult to describe. Analysis of oral microbial flora has been suggested as a suitable measurement method. Oral care aides have been shown to have a positive influence on oral health care in nursing. The outcome of an intervention with oral care aides was followed during a two-year period by recording: (a) the proportion of opportunistic microorganisms and bacteria associated with caries (b) whether oral hygiene assistance were given to the residents or not, and (c) individual experiences concerning oral health care among the staff involved. The oral flora and the amount of oral hygiene assistance improved throughout the entire study period, but staff interviews revealed that it took two years for good cooperation and prophylactic routines to be established. An unexpected finding was the positive correlation (p = .0005) between a high proportion of the opportunistic microorganisms and death within one year.