OBJECTIVE Occlusal adjustment as part of periodontal therapy has been controversial for years, mostly because the literature does not provide enough evidence regarding the influence of trauma from occlusion (TfO) on periodontitis. The need for occlusal adjustment in periodontal therapy is considered uncertain and requires investigation. The aim of this systematic review was to identify and analyse those studies that investigated the effects of occlusal adjustment, associated with periodontal therapy, on periodontal parameters. METHODS A protocol was developed that included all aspects of a systematic review: search strategy, selection criteria, selection methods, data collection and data extraction. METHODS A literature search was conducted using MEDLINE via PubMed, the Cochrane Central Register of Controlled Trials, and EMBASE. METHODS Three reviewers screened the titles and abstracts of articles according to the established criteria. Every article that indicated a possible match, or could not be excluded based on the information given in the title or abstract, was considered and evaluated. On final selection, four articles were included. CONCLUSIONS Although the selected studies suggest an association between occlusal adjustment and an improvement in periodontal parameters, their methodological issues (explored in this review) suggest the need for new trials of a higher quality. There is insufficient evidence at present to presume that occlusal adjustment is necessary to reduce the progression of periodontal disease. CONCLUSIONS Although it is still not possible to determine the role of occlusal adjustment in periodontal treatment, adverse effects have not been related to occlusal adjustment. This means that the decision made by clinicians whether or not to use occlusal adjustment in conjunction with periodontal therapy hinges upon clinical evaluation, patient comfort, and tooth function.