Effectiveness of Modified Clear Aligner Attachment Designs on Molar Extrusion: An In Vitro Typodont Study

Background/Objectives: Clear aligner therapy (CAT) has become a popular, aesthetic, and comfortable alternative to fixed appliances. Advancement of in-house 3D printing has improved accessibility and customization of aligners. However, their effectiveness in achieving certain tooth movements, particularly extrusion, remains uncertain. This study aimed to evaluate the effectiveness of modified aligner designs with different attachment configurations in producing extrusion of the upper first molar using typodont models. Methods: An in vitro study was performed with 400 clear aligners fabricated from shape memory polymer (Graphy Tera Harz TC-85DAC) using a Uniz Slash-C LCD 3D printer. Aligners were divided into four groups (n = 100 each) based on attachment location: no attachment (G1), buccal (G2), palatal (G3), and combined buccal-palatal (G4). Typodont models were used to simulate clinical conditions. Tooth extrusion, inclination, and angulation were measured using CBCT scans (Veraviewepocs 3D R100) and analyzed with Dolphin 3D imaging software. Results: Tooth movement varied by attachment configuration. G1 showed negligible extrusion. G2 and G3 produced significant vertical and angular changes, particularly in cusp extrusion and buccolingual tipping. G4 achieved the most consistent and statistically significant extrusion, with mean values of 0.97 mm (palatal cusp), 0.87 mm (mesiobuccal cusp), 0.72 mm (distobuccal cusp), and 1.62° mesiodistal tipping. The extrusion detected at the mesiobuccal cusp was 0.27, 0.41, 0.95, and 0.87 in G1, G2, G3, and G4, respectively. Buccal-only attachments demonstrated limited effectiveness. Conclusions: Attachment placement significantly affects the efficiency of clear aligners in achieving upper first molar extrusion. Combined buccal and palatal attachments provide superior control of extrusion and tipping movements. Customized attachment strategies may enhance clinical outcomes in CAT.