Fixed orthodontic treatment has an insignificant effect on clinical attachment level.

Data sources Medline, Embase, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Scopus, Web of Knowledge, Virtual Health Library, Google Scholar and ISRCTN registry databases.Study selection Randomised controlled trials (RCTs) and prospective or retrospective non-randomised clinical trials on periodontal healthy human patients receiving comprehensive fixed appliance treatment were considered.Data extraction and synthesis Two reviewers independently extracted data and assessed risk of bias using either the Cochrane tool for RCTs or the ROBINS-I (Risk Of Bias In Non-randomised Studies - of Interventions) tool for non-randomised studies. A Paule-Mandel random-effects meta-analyses was conducted for clinical attachment loss. Results Nine prospective non-randomised trials involving a total of 335 periodontally healthy patients were included. The patients' average age was 22.6 years (range 11.4 - 42.1 years). Seven of the nine studies were assessed as being at moderate risk of bias. Orthodontic treatment was associated with a mean clinical attachment loss of 0.11 mm (95 %CI: 0.12 mm gain to 0.34 mm loss; P = 0.338, I2 = 99.6%), which was neither statistically nor clinically significant.Conclusions The findings suggest that orthodontic treatment might have little or no clinically relevant detrimental effect on the clinical attachment levels of patients.