Preclinical Evaluation of 3D-Printed Orthodontic Aligners Using an Electro-Typodont Model

Ammar A Al Shalabi¹Shaima Malik²Hoon Kim³Abdulaziz Alhotan⁴Ahmed Ghoneima^1,5Tarek M Elshazly^6*

• ¹Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates
• ²Eastman Institute for Oral Health, Rochester, United States
• ³Seoul National University, Gwanak-gu, Republic of Korea
• ⁴King Saud University, Riyadh, Saudi Arabia
• ⁵Section of Orthodontics, School of Dentistry, University of California, Los Angeles, United States
• ⁶Research Associate at oral technology department, university hospital Bonn, Bonn, Germany

Objectives: The use of 3D printing in orthodontic aligner production addresses several limitations of conventional thermoforming. However, existing experimental techniques for evaluating aligner efficacy remain restricted. This study aims to introduce a novel experimental approach employing an electric typodont model to assess the effectiveness of 3D-printed orthodontic aligners in correcting rotation of the maxillary right central incisor (Tooth 11). Materials and Methods: An electric typodont, equipped with heat-activated wax blocks, simulated four rotational severities of Tooth 11: 22°, 32°, 42°, and 52°. Digital scans were processed in Maestro 3D software to design virtual treatment plans, from which four sequential aligners were fabricated per severity level. In total, 240 aligners were 3D-printed, using Tera Harz TC-85 resin, in three thicknesses: 0.50, 0.75, and 1.00 mm. Each aligner underwent a 10-minute heating cycle, followed by a 10-minute cooling period. Tooth rotation was measured manually using a protractor relative to a fixed baseline. The procedure was repeated five times per subgroup, with repositioning guided by custom guiding stents. Results: Across all aligner thicknesses, 80.0–93.1% of the planned rotational correction was achieved by the fourth aligner, leaving residual rotations of approximately 4–5°. Higher initial rotations resulted in a greater percentage of corrections (p < 0.001). The 0.50-mm and 1.00-mm aligners demonstrated faster early-stage correction, whereas the 0.75-mm aligner exhibited a more gradual and consistent derotation pattern throughout the treatment stages (p < 0.001). Conclusion: The electric typodont appears to be a reliable pre-clinical tool for evaluating the effectiveness of aligners. Furthermore, 3D-printed aligners successfully achieved incisor derotation without the use of attachments. Furthermore, while variations in aligner thickness influenced the dynamics of derotation, they did not alter the ultimate correction outcome.