Abstract: We included four RCTs (3905 participants), all of which were at high risk of bias. The studies all evaluated one comparison: professional oral care versus usual oral care. We did not pool the results from one study (N = 834 participants), which was stopped at interim analysis due to lack of a clear difference between groups. We were unable to determine whether professional oral care resulted in a lower incidence rate of NHAP compared with usual oral care over an 18-month period (hazard ratio 0.65, 95% CI 0.29 to 1.46; one study, 2513 participants analysed; low-quality evidence). We were also unable to determine whether professional oral care resulted in a lower number of first episodes of pneumonia compared with usual care over a 24-month period (RR 0.61, 95% CI 0.37 to 1.01; one study, 366 participants analysed; low-quality evidence). There was low-quality evidence from two studies that professional oral care may reduce the risk of pneumonia-associated mortality compared with usual oral care at 24-month follow-up (RR 0.41, 95% CI 0.24 to 0.72, 507 participants analysed). We were uncertain whether or not professional oral care may reduce all-cause mortality compared to usual care, when measured at 24-month follow-up (RR 0.55, 95% CI 0.27 to 1.15; one study, 141 participants analysed; very low-quality evidence). Only one study (834 participants randomised) measured adverse effects of the interventions. The study identified no serious events and 64 non-serious events, the most common of which were oral cavity disturbances (not defined) and dental staining. No studies evaluated oral care versus no oral care. Although low-quality evidence suggests that professional oral care could reduce mortality due to pneumonia in nursing home residents when compared to usual care, this finding must be considered with caution. Evidence for other outcomes is inconclusive. We found no high-quality evidence to determine which oral care measures are most effective for reducing nursing home-acquired pneumonia. Further trials are needed to draw reliable conclusions.

Plain-language summary: This review was carried out through Cochrane Oral Health. We searched scientific databases for relevant studies, up to 15 November 2017. We included four studies, with a total of 3905 participants randomly assigned to treatment or usual care. Participants were long-term-care elderly residents in nursing homes who did not have pneumonia at the beginning of the studies. Some of the participants had dementia or systemic diseases. All studies focused on the comparison between 'professional' mouth care and 'usual' mouth care. None of the studies evaluated oral care versus no oral care. We identified four studies, all of which compared professional mouth care to usual mouth care in nursing home residents. From the limited evidence, we could not tell whether professional oral mouth care was better or worse than usual mouth care for preventing pneumonia. The evidence for death from any cause was inconclusive, but the studies did suggest that professional mouth care may reduce the number of deaths caused by pneumonia, compared to usual mouth care, when measured after 24 months. Only one study measured negative effects of the interventions, and reported that there were no serious events. The most common non-serious events reported were damage to the mouth and tooth staining. The quality of the evidence is low or very low, because of the small number of studies and problems with their design. Therefore, we cannot rely on the findings, and further research is required.