["The Cochrane Oral Health Group's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), Medline, Embase, Chinese Biomedical Literature Database, the WHO International Clinical Trials Registry, and the National Institutes of Health Clinical Trials Registry were searched with no restrictions regarding language or date of publication.", 'Randomised controlled trials comparing different etching materials, or different etching techniques using the same etchants, for the bonding of fixed orthodontic brackets to incisors, canines and premolars in children and adults.', 'Study assessment, risk of bias assessment and data extraction were carried out independently by at least two reviewers. The primary outcome was bond failure rate.', 'Thirteen studies involving 417 patients with 7184 teeth/brackets were included. Two studies were considered to be at low risk of bias, 10 at high risk and one at unclear risk. Eleven studies compared the effects of self-etching primers (SEPs) with conventional etchants.Five of these studies (three of split-mouth design and two of parallel design) reported data at the participant level, with the remaining studies reporting at the tooth level, thereby ignoring clustering/the paired nature of the data.A meta-analysis of these five studies, with follow-up ranging from five to 37 months, provided low-quality evidence that was insufficient to determine whether or not there is a difference in bond failure rate between SEPs and conventional etchants (risk ratio 1.14; 95% confidence interval (CI) 0.75 to 1.73; 221 participants). The uncertainty in the CI includes both no effect and appreciable benefit and harm. Subgroup analysis did not show a difference between split-mouth and parallel studies.There were no data available to allow assessment of decalcification, participant satisfaction and cost-effectiveness. One study reported decalcification, but only at the tooth level.Two studies compared two different SEPs. Both studies reported bond failure rate, with one of the studies also reporting decalcification. However, as both studies reported outcomes only at the tooth level, there were no data available to evaluate the superiority of any of the SEPs over the others investigated with regards to any of the outcomes of this review. No eligible studies were found evaluating different etching materials (eg phosphoric acid, polyacrylic acid, maleic acid), concentrations or etching times.'] Does limited evidence suggest no difference in orthodontic attachment failure rates with the acid-etch technique and self-etch primers?