Enamel etching for bonding fixed orthodontic braces

Acid etching of tooth surfaces to promote the bonding of orthodontic attachments to the enamel has been a routine procedure in orthodontic treatment since the 1960s. Various types of orthodontic etchants and etching techniques have been introduced in the past five decades. Although a large amount of information on this topic has been published, there is a significant lack of consensus regarding the clinical effects of different dental etchants and etching techniques.

To compare the effects of different dental etchants and different etching techniques for the bonding of fixed orthodontic appliances.

We searched the following electronic databases: the Cochrane Oral Health Group's Trials Register (to 8 March 2013), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 2), MEDLINE via OVID (to 8 March 2013), EMBASE via OVID (to 8 March 2013), Chinese Biomedical Literature Database (to 12 March 2011), the WHO International Clinical Trials Registry Platform (to 8 March 2013) and the National Institutes of Health Clinical Trials Registry (to 8 March 2013). A handsearching group updated the handsearching of journals, carried out as part of the Cochrane Worldwide Handsearching Programme, to the most current issue. There were no restrictions regarding language or date of publication.

Randomized controlled trials (RCTs) 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.

Two review authors extracted data and assessed the risk of bias of included studies independently and in duplicate. We resolved disagreements by discussion among the review team. We contacted the corresponding authors of the included studies to obtain additional information, if necessary.

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 etchantsEleven 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 SEPsTwo 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.