Orthodontic anchorage: a systematic review

The aim of this systematic review was to examine, in an evidence-based way, what kind of orthodontic anchorage systems/applications are evaluated and their effectiveness. A literature survey from the Pub Med and Cochrane databases covering the period from January 1966 to December 2004 was performed. Randomized controlled trials (RCT), prospective and retrospective controlled studies, and clinical trials comparing at least two anchorage situations were included. Two reviewers selected and extracted the data independently and also assessed the quality of the retrieved studies. The search strategy resulted in 494 articles, of which 14 met the inclusion criteria. Two main anchorage situations were identified: anchorage of molars during space closure after premolar extractions and anchorage loss in the incisor or premolar region (or both) during molar distalization. Because of contradictory results and the vast heterogeneity in study methods, the scientific evidence was too weak to evaluate anchorage efficiency during space closure. Intraoral molar distalization leads to anchorage loss in various amounts depending on the choice of distalization unit. Most of the studies had serious problems with small sample size, confounding factors, lack of method error analysis, and no blinding in measurements. To obtain reliable scientific evidence, controlled RCT's with sufficient sample sizes are needed to determine which anchorage system is the most effective in the respective anchorage situation. Further studies should also consider patient acceptance and cost analysis as well as implants as anchorage.