Selective air-abrasion removal of residual adhesive following orthodontic bracket de-bonding

Objective: This study presents the use of bio-active glass particles for selective orthodontic adhesive removal, following bracket de-bonding from sound premolars using air-abrasion. Methods: The buccal surfaces of 30 sound extracted human premolars were imaged using scanning electron microscopy (SEM, x40, x600) and then orthodontic brackets bonded using resin adhesive and assigned to three sample groups. Following 7-day storage in water (37^o C), brackets were removed conventionally using orthodontic de-bonding forceps. Residual adhesive was removed using a slow-speed, 8-bladed tungsten carbide bur in group 1, alumina air-abrasion (60 PSI) in group 2 and bioactive glass air-abrasion (60 PSI) in group 3. The enamel surface was deemed clinically adhesive-free after visual examination at x3 magnification. The resultant enamel surfaces were examined using SEM of resin replicas. The enamel loss after 60 seconds of bioactive glass air-abrasion and alumina air-abrasion was also recorded, gravimetrically. Results: In the 3 groups, the residual adhesive was completely removed. In group 1, bur-attributable enamel surface damage and ″scarring″ was observed using SEM (x40) whilst at x600, the surface detail exhibited micro-scarring in line with the enamel prisms. In both air-abrasion groups 2 & 3, no scarring was observed with x 40 SEM. In group 2 (alumina), the surface was rough, with jagged, angular finished profiles (x600). In group 3 (bioactive glass) the surface finish, although still pitted, was less deeply scarred and subjectively smoother (x600). Bioactive glass air-abrasion removed healthy enamel 40x slower than the equivalent alumina air-abrasion. Conclusion: Bioactive glass and alumina air-abrasion have been shown to be as effective as bur removal of residual resin adhesive after orthodontic bracket de-bonding. However, bioactive glass abrasion resulted in the least damage to the de-bonded enamel surface.