BACKGROUND: It is important to institute an effective supportive therapy to maintain or recover soft tissue health around dental implants. Different maintenance regimens have been suggested, however it is unclear which are the most effective. OBJECTIVES: To test the null hypotheses of no difference between different interventions (1) for maintaining healthy peri-implant soft tissues, and (2) for recovering soft tissue health, against the alternative hypothesis of a difference. SEARCH STRATEGY: We searched the Cochrane Oral Health Group's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. Handsearching included several dental journals. We checked the bibliographies of the identified randomised controlled trials (RCTs) and relevant review articles for studies outside the handsearched journals. We wrote to authors of all identified RCTs, to more than 55 oral implant manufacturers and to an internet discussion group to find unpublished or ongoing RCTs. No language restrictions were applied. The last electronic search was conducted on 13 June 2007. SELECTION CRITERIA: All randomised controlled trials comparing agents or interventions for maintaining or recovering healthy tissues around dental implants. DATA COLLECTION AND ANALYSIS: Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were conducted in duplicate and independently by two review authors. Results were expressed as random-effects models using standardised mean differences for continuous data and risk ratios for dichotomous data with 95% confidence intervals. MAIN RESULTS: Eighteen RCTs were identified. Nine of these trials, which reported results from a total of 238 patients, were included. Follow ups ranged between 6 weeks and 1 year. No meta-analysis could be made since every RCT tested different interventions. Listerine mouthwash showed a reduction of 54% in plaque and 34% in marginal bleeding compared with a placebo. Two trials evaluated the efficacy of powered and sonic toothbrushes compared to manual toothbrushing and showed no statistically significant differences, though more patients liked the sonic brush. No statistical differences were found between brushing with a hyaluronic or a chlorhexidine gel, between cleaning with an etching gel or manually, between injecting a chlorhexidine or a physiologic solution inside the implant's inner part and between submucosal minocycline and a chlorhexidine gel. When an amine fluoride/stannous fluoride (AmF/SnF(2)) mouthrinse was compared with a chlorhexidine one, no statistically significant differences were found for implant failures and staining index while patients preferred and had less taste change with the AmF/SnF(2) mouthrinse. Self administered subgingival chlorhexidine irrigation resulted in statistically significantly lower plaque and marginal bleeding than a chlorhexidine mouthwash, however the mouthwash was given at a suboptimal dosage. AUTHORS' CONCLUSIONS: There was only little reliable evidence for which are the most effective interventions for maintaining or recovering health of peri-implant soft tissues. The included RCTs had short follow-up periods and few subjects. There was not any reliable evidence for the most effective regimens for long term maintenance. This should not be interpreted as current maintenance regimens are ineffective. There was weak evidence that Listerine mouthwash, used twice a day for 30 seconds, as an adjunct to routine oral hygiene, is effective in reducing plaque and marginal bleeding around implants. More RCTs should be conducted in this area. In particular, there is a definite need for trials powered to find possible differences, using primary outcome measures and with much longer follow up. Such trials should be reported according to the CONSORT guidelines (http://www.consort-statement.org/).