A 3D-Printed Crown Integrated with 3D-Printed Orthodontic Brackets: A Novel One-Unit Printing Technique

This study aimed to present a new application of 3D printing technology for crowns integrated with orthodontic brackets as one unit and to assess the strength of the bonded groups and the one-unit printed group. A total of 60 lateral incisors with brackets were obtained and allocated into two main groups: bonded groups and one-unit group. For the bonded groups, there were 40 specimens (20 conventionally fabricated crowns and 20 3D-printed crowns with bonded brackets), while for the one-unit group, there were 20 3D-printed crowns and brackets fabricated as one unit. One lateral incisor and one with a bracket were scanned, forming STL files for designing and printing 3D-printed specimens (20 without, 20 with brackets). Half of the specimens (30, n = 10) were thermocycled (5000 cycles). A universal testing machine was used for the bond strength (MPa) measurement, followed by analysis of the debonded areas and failure mode (adhesive, cohesive, or mixed). ANOVA and the post hoc Tukey's test were used for analysis of the collected data (α = 0.05). The 3D-printed one-unit group significantly showed high strength compared with the bonded brackets (p < 0.001). The 3D-printed bracket showed the highest SBS (10.14 ± 1.93 MPa). After thermocycling, the bond strength of the bonded brackets significantly decreased (p < 0.001). The adhesive failure was dominant in the bonded groups, while the one-unit group exhibited all the fractures in the brackets. The introduced technique for producing a one-unit 3D-printed provisional crown integrated with orthodontic brackets is considered a clinically plausible option in contemporary orthodontic practice. However, further investigations are recommended to verify the findings of the present study before clinical implementation.