Comparison of bond strength and adhesive remnant index of 3-dimensional-printed orthodontic brackets fabricated with different resins and surface treatments.

INTRODUCTION This study evaluated the shear bond strength (SBS), maximum debonding force (MDF), and adhesive remnant index (ARI) of 3-dimensional-printed brackets made from 3 resins after different base treatments.

Methods

Premolars (n = 240) were assigned to 12 groups (n = 20). Brackets were printed from Saremco Print Crowntec, VarseoSmile Crown plus, or P-Crown V3 with retention grooves (G1), aluminum oxide air abrasion (G2), erbium, chromium:yttrium-scandium-gallium-garnet laser treatment (G3), or as-printed bases (G4). After thermocycling, SBS, MDF, ARI, and structural fracture incidence were evaluated. SBS and MDF were analyzed using 2-way analysis of variance followed by Tukey honestly significant difference tests, whereas ARI and fracture incidence were analyzed using Fisher-Freeman-Halton exact tests. The SBS sensitivity analysis excluded specimens with enamel or bracket fractures.

Results

Resin type and surface treatment affected SBS (both P <0.001), which ranged from 11.81-15.42 MPa. P-Crown V3 exhibited higher SBS than Saremco Print Crowntec and VarseoSmile Crown plus, whereas G2 and G3 had higher SBS than G1 and G4. Sensitivity analysis confirmed the resin (P = 0.004) and surface-treatment (P <0.001) effects and showed a significant interaction (P = 0.043). Surface treatment affected MDF (P <0.001), with G1 showing the highest value. ARI distributions differed among resins (P <0.001), and surface treatment affected ARI only within VS (P = 0.031). The incidence of structural fracture did not differ by resin or surface treatment.

Conclusions

All groups, including the untreated G4 group, exceeded the 6-8 MPa laboratory benchmark. G2 and G3 increased SBS, whereas the G1 design increased MDF. These findings should be considered alongside failure mode and the potential for enamel damage.