Abstract: We included 13 studies randomizing 417 participants with 7184 teeth/brackets. We assessed two studies (15%) as being at low risk of bias, 10 studies (77%) as being at high risk of bias and one study (8%) as being at unclear risk of bias. Self etching primers (SEPs) versus conventional etchants Eleven studies compared the effects of SEPs with conventional etchants. Only 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, thus ignoring clustering/the paired nature of the data. A meta-analysis of these five studies, with follow-up ranging from 5 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 convention 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 the outcomes: decalcification, participant satisfaction and cost-effectiveness. One study reported decalcification, but only at the tooth level. SEPs versus SEPs 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. We did not find any eligible studies evaluating different etching materials (e.g. phosphoric acid, polyacrylic acid, maleic acid), concentrations or etching times. We found low-quality evidence that was insufficient to conclude whether or not there is a difference in bond failure rate between SEPs and conventional etching systems when bonding fixed orthodontic appliances over a 5- to 37-month follow-up. Insufficient data were also available to allow any conclusions to be formed regarding the superiority of SEPs or conventional etching for the outcomes: decalcification, participant satisfaction and cost-effectiveness, or regarding the superiority of different etching materials, concentrations or etching times, or of any one SEP over another. Further well-designed RCTs on this topic are needed to provide more evidence in order to answer these clinical questions.

Plain-language summary: Cochrane Oral Health carried out this review of existing studies, which includes evidence current up to 8 March 2013. This review includes 13 published studies in which a total of 417 children and adults randomly received different tooth preparations before fixed orthodontic braces were bonded to their teeth. Eleven of these studies compared SEPs with conventional etching, and two compared two different SEPs. Only five of the studies provided usable evidence for this review and the combined results did not enable a conclusion to be made about whether or not there is a difference in bond failure (when the orthodontic fixings come away from the tooth) between SEPs and conventional etching. There was also no usable evidence to suggest whether SEPs or conventional etchants lead to less decay around the etching site, or are associated with fewer costs or better participant satisfaction. There was also no usable evidence to enable conclusions to be drawn about which was the best SEP, acid, concentration or etching time. The evidence presented is of low quality due to issues with the way in which some of the studies were conducted.