Background: Adherence to oral hygiene is an important aspect of the treatment of periodontal disease. Traditional educational interventions have been shown to be of little value in achieving long term behaviour change. Objectives: The aim of this review was to determine the impact of interventions aimed to increase adherence to oral hygiene instructions in adult periodontal patients based on psychological models and theoretical frameworks. This review considered the following outcomes:Observational measures of oral health related behaviourSelf reported oral health related behaviours, beliefs and attitudes towards oral health related behaviourClinical markers of periodontal disease. Search methods: The Cochrane Oral Health Group's Trials Register (2005), CENTRAL (The Cochrane Library 2004, Issue 4), MEDLINE (from 1966 to December 2004), EMBASE (from 1980 to December 2004), PsycINFO (from 1966 to December 2004), Ingenta (from 1998 to December 2004) and CINAHL (from 1966 to December 2004). Reference lists from relevant articles were searched and the authors of eligible trials were contacted to identify trials and obtain additional information. No language restriction was applied. Selection criteria: Randomised controlled trials testing the effectiveness of interventions based on psychological models compared with educational, attention or no active intervention controls to improve adherence to oral hygiene in adults with either gingivitis or periodontitis. Data collection and analysis: Titles and abstracts of studies that were potentially relevant to the review were independently screened by two review authors. Those that were clearly ineligible were rejected. For the remaining studies, the full paper was reviewed by two review authors and where necessary further information was sought from the author to verify eligibility. Included studies were assessed on their quality using standard criteria. Main results: The review identified four studies (including 344 participants) in which a psychological model or theory had been explicitly used as the basis for the design of the intervention. The overall quality of trials was low. Due to the heterogeneity between studies, both in terms of outcome measures and psychological models adopted, a meta-analysis was not possible. The four studies adopted four different theoretical frameworks, though there was some overlap in that three of the studies incorporated elements of Operant and Classical Conditioning. Psychological interventions resulted in improved plaque scores in comparison to no intervention groups, and in one study in comparison to an attention control group. One study found decreased gingival bleeding in the active intervention group but no change in pocket depth or attachment loss after 4 months. Psychological interventions were associated with improved self reported brushing and flossing in both studies which assessed these behaviours. Only one study explored the impact of psychological interventions on beliefs and attitudes, the psychological intervention, in comparison to educational and no intervention controls, showed improved self efficacy beliefs in relation to flossing, but no effect on dental knowledge or self efficacy beliefs in relation to tooth brushing. Authors' conclusions: There is tentative evidence from low quality studies that psychological approaches to behaviour management can improve oral hygiene related behaviours. However, the overall quality of the included trials was low. Furthermore, the design of the interventions was weak and limited, ignoring key aspects of the theories. Thus, there is a need for greater methodological rigour in the design of trials in this area.