BACKGROUND: Although mechanical non-surgical therapy (scaling and root planing) is the most common means of initial treatment of periodontal diseases, the relative clinical efficacy of various methods, including manual versus machine-driven, with or without adjunctive agents, has not been determined. RATIONALE: This systematic review analyzes the literature in an effort to identify the most effective therapies, based on both clinical and patient-centered outcomes. FOCUSED QUESTION: In patients with periodontitis, what is the effect of mechanically-driven instrumentation (e.g., power-driven) and/or subgingival irrigation with and without manual instrumentation compared to manual instrumentation alone? SEARCH PROTOCOL: Two investigators examined MEDLINE and the Cochrane Oral Health Group specialized registry for clinical trials published in English. Hand searches were performed of the International Journal of Periodontics & Restorative Dentistry, Journal of Clinical Periodontology, Journal of Periodontology, and Journal of Periodontal Research. Searches were performed for articles published through April 2002. Editors of these journals were asked to provide information on articles currently under review. In addition, an electronic discussion group on periodontal diseases and treatment was contacted, as were manufacturers of manual and mechanical instruments and of adjunctive agents. INCLUSION CRITERIA: Only randomized clinical trials, cohort studies, or case-control studies at least 3 months long were included. All studies had to compare manual instrumentation (MI; scaling and root planing [SRP]) alone with some other form of non-surgical therapy. These included MI versus mechanically-driven instruments (MDI) alone; MI versus MI plus MDI; MI versus MDI plus an agent (e.g., chlorhexidine); and MI versus subgingival irrigation (SGI) delivered in conjunction with MI or MDI. EXCLUSION CRITERIA: Studies not meeting the inclusion criteria or those treating periodontal diseases as a manifestation or complication of some other disease or disorder were not included. DATA COLLECTION AND ANALYSIS: Probing depth, clinical attachment level, bleeding on probing, and gingival recession were the primary outcomes. Because of the heterogeneity of the patient populations, treatments, and outcome measures, meta-analysis was not appropriate. Only in-study data were compared. Four of the studies required extrapolating data from figures and graphs, resulting in questionable accuracy. MAIN RESULTS: 1. Nine studies, representing a study population of 129, were included in the review. 2. Five studies compared MI with MDI alone. The other 4 compared MI alone to MI plus SGI or subgingival tissue treatment. 3. There was comparable efficacy between MI and MDI when treating single-rooted teeth. 4. The use of SGI or subgingival tissue treatment as an adjunct to MI provided no additional benefit compared to MI alone. 5. Findings reported in the review must be interpreted with considerable caution, as lack of study heterogeneity made meta-analysis unfeasible and the need to extrapolate outcomes values from graphs and figures may have resulted in some inaccuracy. REVIEWERS' CONCLUSIONS: 1. Manual and mechanically-driven instrumentation appears comparable in affecting improved clinical outcomes. 2. Instrumentation time for MI and MDI were similar, except for 1 study in which MDI was significantly shorter. 3. Adjunctive SGI plus MI and subgingival tissue treatment result in similar clinical outcomes when compared to MI alone. 4. If study data are to be effectively and analytically combined to facilitate meaningful comparisons of treatment outcomes, detailed and standardized study designs must be developed and used consistently in clinical trials.