Self-etch adhesives for the bonding of orthodontic brackets: faster, stronger, safer?

Abstract

This study aimed to evaluate the performance of accelerating procedures for bonding of orthodontic brackets in vitro by comparing different adhesives (etch-and-rinse, self-etch) and polymerization procedures (curing devices, time). The performance was characterized by three parameters: (1) the bond strength achieved, (2) the incidence of enamel damage, and (3) the extent of residual composite on the tooth. Bracket bonding was performed on 500 extracted human teeth after application of either an etch-and-rinse adhesive or a one-step self-etch adhesive. Two different two-component self-etch adhesives (Clearfil SE and Transbond Plus) and two single-component self-etch adhesives (Ideal and iBond) were investigated after using different polymerization procedures (light-emitting diode for 10 or 20 s or plasma arc curing device for 3 or 6 s). The bond strength, incidence of enamel damage, and extent of residual composite on the tooth were measured. Single-component self-etch adhesives gave the lowest bond strengths. No significant difference in bond strength could be detected between the two-component self-etch adhesives and the etch-and-rinse method. There was a 70.3% risk for enamel damage at bond strengths above 12 MPa, but only 5% risk below 12 MPa and no risk below 8.2 MPa. The risk of enamel damage increased by an odds ratio increment of 1.3 for each additional MPa above 8.2 MPa. Single-component self-etch adhesives showed the lowest bond strengths, caused limited enamel damage, and generally left less residual composite on the tooth. The nature of the adhesive greatly influences the resultant bond strength, the risk of enamel damage, and the extent of residual composite on the teeth.