Bonding braces and etching enamel: review update!

Dental_braces_smallMany people need to wear fixed orthodontic braces to correct problems with their teeth or jaw. In order to attach a brace to the teeth, the surface of the appropriate tooth needs to be prepared so that it can retain the glue or bonding agent. Acid etching, to roughen tooth surfaces to promote the bonding of orthodontic braces or brackets to teeth, has been a routine procedure in orthodontic treatment since the 1960s. Various types of orthodontic etchants and etching techniques have been introduced over the past 50 years, such as self-etching primers. These have been seen as an alternative to conventional acids or etchants. This review considers which type of etchant or etching technique is most effective.

What was the research?

A systematic review of the evidence to compare the effects of different dental etchants and different etching techniques for the bonding of fixed orthodontic appliances.

Who conducted the research?

The research was conducted by a team led by Haikun Hu from the West China College of Stomatology, on behalf of the Cochrane Oral Health Group. Chunjie Li, Fan Li, Jianwei Chen, Jianfeng Sun, Shujuan Zou, Andrew Sandham, Qiang Xu, Philip Riley and Qingsong Ye were also on the team.

What evidence was included in the review?

Data was extracted from 13 randomised controlled trials. A total of 417 orthodontic patients participated in the trials. People were assigned to conventional etching versus self-etching primers in 11 of the trials, and two trials compared different self-etching primers. The trials looked at the rate of bond failure, which is when the orthodontic bracket comes away from the tooth and becomes detached.

What did the evidence say?

Only five of the studies provided evidence for this review that could be used, and the combined results did not enable a conclusion to be drawn about whether or not there is a difference in bond failure between self-etching primer and conventional etching. There was also no usable evidence to suggest which technique leads to less decay around the etching site, which is associated with fewer costs and which with better patient satisfaction.

How good was the evidence?

Several issues were identified in the way that the studies were conducted, and the review team conclude that the evidence presented is of low quality. There were serious concerns over selection bias in two of the studies. Some of the more recent trials were “split mouth” studies, where one etching technique was used on one tooth, and another technique on a different tooth, in the same patient. This may be misleading as one bonding agent may affect the performance of the other and does not reflect clinical practice.

What are the implications for dentists and the general public?

Low quality evidence was found that was not sufficient to draw a conclusion on the difference in bond failure rates between different etching techniques.

What should researchers look at in the future?

More randomized controlled trials on this topic are needed, especially studies investigating new etching techniques and etching materials.


Hu H, Li C, Li F, Chen J, Sun J, Zou S, Sandham A, Xu Q, Riley P, Ye Q. Enamel etching for bonding fixed orthodontic braces. Cochrane Database of Systematic Reviews 2013, Issue 11. Art. No.: CD005516. DOI: 10.1002/14651858.CD005516.pub2.