Effects of enamel sealing on shear bond strength and the adhesive remnant index

Selected combinations of materials were used to create tooth–adhesive–bracket complexes to evaluate shear bond strength (SBS) and the adhesive remnant index (ARI) with regard to enamel sealing.

Four adhesive systems also appropriate for use as enamel sealants were combined with four bracket types, resulting in 16 adhesive–bracket combinations, each of which was tested on 15 permanent bovine incisors. Sealant–adhesives included two recently introduced fluoride-releasing systems (Riva bond LC^® and go!^®), one established primer (Opal^® Seal™), and one commonly used adhesive as control (Transbond™ XT). Brackets included two metal (discovery^® by Dentaurum and Sprint^®) and two ceramic (discovery^® pearl and GLAM^®) systems. After embedding the bovine teeth, bonding the brackets to their surface, and storing the resultant samples as per DIN 13990-2 with modifications, an SBS test was performed by applying the shear force directly at the bracket base in an incisocervical direction. Then the ARI scores were determined.

Discovery^® + Transbond™ XT yielded the highest (47.2 MPa) and GLAM^® + go!^® the lowest (17.0 MPa) mean SBS values. Significant differences (p < 0.0001) were found between metal and ceramic brackets of the same manufacturers (Dentaurum and Forestadent). Our ratings of the failure modes upon debonding predominantly yielded ARI 0 or 1. The high SBS values and low ARI scores observed with discovery^® + Transbond XT™ were reflected in a high rate of enamel fracture, which occurred on 11 of the 15 tooth specimens in this group.

All sealant–bracket combinations were found to yield levels of SBS adequate for clinical application. SBS values and ARI scores varied significantly depending on which sealant–brackets were used.