Self-etch primers and conventional acid-etch technique for orthodontic bonding: a systematic review and meta-analysis

The use of self-etch primers has increased steadily because of their time savings and greater simplicity; however, overall benefits and potential disadvantages and harms have not been assessed systematically. In this study, we reviewed randomized controlled trials to assess the risk of attachment failure, bonding time, and demineralization adjacent to attachments between 1-stage (self-etch) and 2-stage (acid etch) bonding in orthodontic patients over a minimum follow-up period of 12 months.

Data sources were electronic databases including MEDLINE, EMBASE, the Cochrane Oral Health Group's Trials Register, and CENTRAL, without language restrictions. Unpublished literature was searched on ClinicalTrials.gov, the National Research Register, and Pro-Quest Dissertation Abstracts and Thesis database. Authors were contacted when necessary, and reference lists of the included studies were screened. Search terms included randomized controlled trial, controlled clinical trial, random allocation, double-blind method, single-blind method, orthodontics, self-etch, SEP, primer, and bonding agent. Randomized clinical trials directly comparing self-etch and acid-etch primers with respect to the predefined outcomes and including patients with full-arch, fixed, and bonded orthodontic appliances (not banded) with follow-up periods of at least 12 months were included. Using predefined forms, 2 authors undertook independent data extraction with conflict resolution by the third author. Randomized clinical trial quality assessment based on the Cochrane Risk of Bias tool was also used.

Eleven studies met the inclusion criteria; 6 were excluded because of a high risk of bias. In total, 1721 brackets bonded with acid-etch and 1723 with self-etch primer techniques were included in the quantitative synthesis. Relatively low statistical and clinical heterogeneity was observed among the 5 randomized clinical trials (n = 3444 brackets) comparing acid-etch with self-etch primers. A random effects meta-analysis demonstrated a tendency for a higher risk of failure (odds ratio, 1.35; 95% CI, 0.99-1.83; P = 0.06) with self-etch primers. A small but statistically significant time saving was also associated with the self-etch primer technique (weighted mean difference, 23.2 seconds per bracket; 95% CI, 20.7-25.8; P <0.001). There was insufficient evidence to assess the effect of bonding modality on demineralization rates.

There is weak evidence indicating higher odds of failure with self-etch primer than acid etch over 12 months in orthodontic patients, and there is strong evidence that a self-etch primer is likely to result in a modest time savings (8 minutes for full bonding) compared with acid etch.