Initial Force Expression of Different Clear Aligner Systems in a Simulated Maxillary Canine Distalization Model with Lateral Incisor Agenesis: An In Vitro Comparative Study

Background: This in vitro study compared initial force release by different clear aligner systems during simulated maxillary canine distalization with lateral incisor agenesis and evaluated attachment effects. Methods: Five aligner systems were tested: SmartTrackTM (Invisalign®, Align Technology Inc., Santa Clara, CA, USA), TruGENTM (Spark®, Ormco Corporation, Brea, CA, USA), Essix® (SureSmile®, Dentsply Sirona Inc., Charlotte, NC, USA), MasterControl S (Angel Aligner®, Angelalign Technology Inc., Shanghai, China), and a directly 3D-printed aligner fabricated with TC-85 DAC resin (Graphy®, Graphy Inc., Seoul, Republic of Korea). Ten identical aligners per configuration were tested for 1 h at 37 °C in physiological solution. The ElectroForce® system measured the translational force at the canine’s root-level support. Data were analyzed using descriptive statistics and two-way ANOVA. Results: TruGENTM with attachments generated the highest mean force (1.25 N), followed by SmartTrackTM (0.61 N), Essix® (0.42 N), MasterControl S (0.39 N), and TC-85 DAC resin (0.01 N). Without attachments, forces were minimal for all systems. Force decay was observed in groups expressing measurable forces. Conclusions: Attachments enabled measurable translational force components in thermoformed systems. Force expression differed among systems, while TC-85 DAC resin produced negligible forces with or without attachments under experimental conditions. Further clinical validation is warranted.