Linda Cheng DDS, FAGD, ABGD
Weak evidence indicates higher odds of orthodontic attachments failing with self-etch primers (SEPs) than acid-etch bonding systems (AEs) over 12 months; while strong evidence exists indicating SEPs are likely to provide modest time savings compared with AEs.
In patients with full-arch, fixed and bonded orthodontic appliances, what is the risk of attachment failure, difference in bonding time, and risk of demineralization adjacent to attachments bonded with SEPs as compared to AEs?
The reviewers searched four databases with no language restrictions for literature published between 1966 to July 2011 and three additional databases for unpublished literature. They screened conference abstracts and the reference lists of the final included studies in addition to contacting the authors to identify unpublished studies and to clarify data when required. The reviewers included only RCTs that reported primary outcomes as first-time bond failures of SEPs compared to AEs in full-arch, fixed and bonded orthodontic appliances in a minimum follow-up period of 12 months. They included bonding time and demineralization around attachments as secondary outcomes. They excluded studies with banded attachments. Two reviewers, who were not blinded to the authors or the results of the research, extracted the data and assessed risk of bias independently and in duplicate. A third reviewer resolved any disagreements by consultation and discussion. The authors assessed heterogeneity and conducted sensitivity analyses.
Eleven articles met the inclusion criteria. The authors excluded five studies that had inadequate randomization procedures from the final quantitative analysis and a sixth study that ended prematurely with an excessive number of failures with SEP.1 They conducted the random-effects model of meta-analysis on the remaining five studies that were deemed to have low or unclear risk of bias. Failures with AEs were 4.5 percent (77 brackets) while failures with SEPs were 6.0 percent (104 brackets). The odds of attachments failures bonded with SEPs were slightly higher than with AEs, though not statistically significant (n=3,444 brackets (SEP and AE); odds ratio (OR)=1.35; 95% CI:0.99-1.83; P=0.06). Use of SEPs provided some time savings (weighted mean difference=23.2 seconds per bracket; 95% CI: 20.7-25.8; P<0.001). Insufficient data regarding demineralization around bonded attachments did not allow for analysis.
Weak and statistically insignificant evidence indicates that attachments bonded with SEPs have a tendency to fail when compared to AEs. Strong evidence suggests that practitioners may save eight minutes of chair-side time per patient when bonding dual-arch appliances by using SEPs rather than AEs.
Source of Funding:
Importance and Context:
The use of SEPs has grown since they do not involve a separate application of etchant. An estimated 29.5 percent of practitioners in the United States use SEPs for orthodontic bonding because of their simplicity and potential time savings.2 This SR assesses the time saved, the risk of bond failures, and demineralization around attachments bonded with SEPs as opposed to AEs.
Strengths and Weaknesses of the Systematic Review:
In this well-conducted SR, the authors used seven criteria in the Cochrane Risk of Bias Tool to assess the risk of bias in each study. The reviewers deemed studies with at least one criterion of high risk as having an overall high risk of bias and excluded them from the final meta-analysis. For completeness, the authors conducted a meta-analysis that included the study with Ideal 1 SEP, which had been excluded for excessive failure rates,1 and found that the results did not change significantly (95% CI: 0.92-2.9), but statistical heterogeneity increased significantly (I2=78.3%; chi-square, P<0.001). Because included studies had to have minimum follow-up periods of 12 months, the SR does not contain information from studies of shorter duration. Only two RCTs in the list of studies considered for quantitative analysis identify the SEP used: Ideal 1 in one study and TransBond Plus in the other.
Strengths and Weaknesses of the Evidence:
All the split mouth and parallel studies in the meta-analysis had complete outcome data reported with low statistical and clinical heterogeneity (I2=0.0%, P=0.497; tau2=0.00). Only two studies assessed the time taken to place individual attachments. The statistical heterogeneity of these studies was elevated (I2= 68.2%; chi-square, P=0.08; tau2=2.48); however, the variance in time lies in a narrow range.3 Only one RCT followed the long-term performance of SEP for the entire duration of orthodontic treatment. The single study that assessed demineralization outcomes lacked information on randomization and allocation concealment.
Implications for Dental Practice:
No clear evidence currently exists favoring SEPs or AEs in orthodontic bonding.4 The choice of which bonding protocol to follow remains at the discretion of each practitioner. More studies are needed to investigate SEPs versus AEs concerning time savings and cost-effectiveness of bonding and de-bonding, overall bond strength, and demineralization around attachments over the complete course of orthodontic treatment. 1) House K, Ireland AJ, Sherriff M. An investigation into the use of a single component self-etching primer adhesive system for orthodontic bonding: a randomized controlled clinical trial. J Orthod 2006;33(1):38-44. 2) Keim RG, Gottleib EL, Nelson AH, Vogels DS 3rd. 2008 JCO study of orthodontic diagnosis and treatment procedures, part 1: results and trends. J Clin Orthod 2008;42(11):625-40. 3) Bornstein M., Hedges LV, Higgins JPT, Rothstein HR, eds. Introduction to meta-analysis. Chichester, United Kingdom: John Wiley & Sons; 2009. 4) Hu H, Li C, Li F, et. al. Enamel etching for bonding fixed orthodontic braces. Cochrane Database Syst Rev 2013 Nov 25:11:CD005516. doi: 10.1002/14651858.CD005516.pub2.