This study aimed to assess the effect of different types of laser etching versus phosphoric acid etching on shear bond strength (SBS) of metal brackets to human enamel.

In this systematic review and meta-analysis, relevant articles published until the end of October 2019 were retrieved from PubMed, ISI Web of Science, Scopus, Embase, and Cochrane Library. The inclusion criteria were in vitro studies on the effect of laser on SBS of metal brackets to the enamel in comparison with acid-etching, and studies published in English to the end of October 2019. After assessing the eligibility criteria and quality, a total of 18 studies were statistically analysed using STATA software.

The SBS of 554 human tooth specimens in the test group (subjected to irradiation of different laser types) was compared with the SBS of 313 tooth specimens in the control group (etched with phosphoric acid). The meta-analysis showed that laser etching decreased the SBS of brackets by 1.39MPa, compared with phosphoric acid etching, and this reduction was statistically significant (P<0.05). The Er:YAG group, however, showed 0.6MPa higher SBS than phosphoric acid etching group, but this increase was not statistically significant.

Laser etching yields lower SBS than acid etching; even though different laser types have different effects on SBS. Thus, the conventional acid-etching technique is still recommended for enamel etching prior to the bonding of orthodontic metal brackets.