This study evaluated shear bond strength (SBS) and adhesive remnant index (ARI) of metal and ceramic orthodontic brackets bonded to three 3D-printed crown materials and one milled control.

In all, 128 samples were fabricated from VarseoSmile Crown TriniQ®, SprintRay Ceramic Crown, Flexcera™ Smile Ultra Plus, and Lava Ultimate™ ( n = 16 per group; 8 groups total). Metal (Mini Master®) and ceramic (Radiance Plus®) brackets were bonded using 50 μm aluminium oxide air abrasion and Transbond™ XT. Samples underwent thermocycling for 1000 cycles (5 °C to 55 °C). SBS was analysed using two-way ANOVA with Tukey's HSD; ARI scores were analysed using Kruskal-Wallis test with Dunn's post hoc comparisons.

All groups exceeded the clinically acceptable SBS threshold to enamel of 6 MPa. Restorative material significantly affected SBS ( P < 0.001), and a significant interaction between bracket type and material was observed ( P < 0.001). SprintRay Ceramic Crown produced the highest mean SBS for ceramic (28.18 ± 4.15 MPa) and metal brackets (22.68 ± 4.96 MPa), significantly exceeding all other materials ( P < 0.001). Bracket type had no significant overall effect on SBS ( P = 0.26); however, ceramic brackets showed significantly higher SBS than metal brackets on SprintRay and Lava Ultimate™, while metal brackets showed significantly higher SBS than ceramic brackets on VarseoSmile® and Flexcera™. Metal brackets produced predominantly higher ARI scores, while ceramic brackets showed more mixed failure patterns.

Standard bonding with aluminium oxide air abrasion and Transbond™ XT produced SBS higher than that reported for enamel across all materials. Restorative material significantly influenced bond strength, and bracket performance varied by substrate, suggesting bracket selection may account for the specific restorative material. ARI findings indicate failure location differs between bracket types.