Randomised controlled trials (RCTs) and non-randomised controlled studies comparing supragingival use of oral water irrigation as an adjunct to toothbrushing, or regular oral hygiene with toothbrushing alone, or regular oral hygiene, in adults in good general health were eligible for inclusion. Included studies were required to be of at least four weeks duration. Eligible studies had to report the outcomes of interest, which were plaque, bleeding, gingivitis, or pocket depth. Studies using orthodontic appliances or subgingival irrigation tips were excluded.
A range of irrigation devices were evaluated, irrigating with 500ml or 600ml of water, once or twice per day, where reported. A range of different indices were used to measure plaque, bleeding and gingivitis. Where reported, participants were aged from 18 to 75 years. Periodontal status of included participants varied across studies, including those with healthy tissue, periodontitis in a maintenance care phase, bleeding on probing, and those with a gingival index greater than one at a minimum number of sites.
Two reviewers independently screened studies for inclusion, with any disagreements resolved by discussion.