Effect of 3D‑printed customized base designs on the mechanical retention and bonding strength of metal brackets

The objectives of this study were to (1) evaluate the effect of different customized base designs on the shear bond strength (SBS) of metal orthodontic brackets fabricated by selective laser melting (SLM) and (2) assess their clinical feasibility. Seventy-five extracted human premolars were randomly divided into five groups ( n = 15). Five types of bracket bases were designed: smooth base, pin-retention base, mesh base, hexagonal honeycomb base, and hollow honeycomb base. All brackets were fabricated using SLM technology with 316 L stainless steel. SBS was measured using a universal testing machine, and adhesive remnant index (ARI) scores were evaluated under magnification. Statistical analysis was performed using one-way analysis of variance (ANOVA) and Kruskal–Wallis tests. Significant differences in SBS were observed among the groups ( P < 0.05). The hollow honeycomb group showed the highest bond strength, followed by the hexagonal honeycomb group. No significant differences in ARI scores were found among the groups ( P > 0.05). SLM-fabricated customized orthodontic brackets demonstrated clinically acceptable bonding performance levels. The hollow honeycomb base design significantly improved mechanical retention and bond strength.