Effect of resin remnant removal techniques on enamel and composite restoration surfaces after orthodontic debonding

In an in vitro model, this study compared three resin-remnant removal technique combinations on enamel and adjacent resin-composite restoration surfaces after orthodontic bracket debonding and evaluated whether adhesive type or ×6 magnification altered outcomes. A total of 180 extracted maxillary central incisors were restored with a nano-ceramic composite, and brackets were bonded across the enamel-restoration junction using Transbond XT, Transbond Plus Color Change, or Brackfix (n = 60 each). Specimens were thermocycled after restoration and again after bracket bonding. After debonding, residual resin was removed using: (1) tungsten carbide bur followed by multistep discs/spirals; (2) zirconia bur followed by polyamide bur; or (3) 53-µm alumina air-abrasion followed by bioactive-glass air-polishing. Surface roughness (arithmetical mean roughness, Ra) and total material loss, measured volumetrically, were co-primary outcomes; FESEM was qualitative illustrative support. Magnification and adhesive type did not significantly affect Ra or total material loss, whereas removal technique significantly affected both. Technique 1 produced the lowest Ra (0.36 ± 0.24 μm) and Technique 3 the highest (1.52 ± 0.51 μm). Technique 2 showed the lowest measured total material loss (0.07 ± 0.01 mm³) and Technique 3 the greatest (0.26 ± 0.05 mm³). Under these in vitro conditions, carbide bur plus multistep polishing was associated with the lowest Ra, whereas zirconia plus polyamide bur was associated with the lowest measured total material loss. Because fluorescence-aided visualization was used only within the Brackfix protocol, its independent effect could not be determined.