Impact of buccopalatal translation and trimline design on clear aligners: An in vitro study of the maxillary right central incisor

Objective: The present study focused on the biomechanical dynamics of clear aligners in managing translational movement with a view to exploring the effects of trimline design and buccopalatal translation on the force and moments acting on the maxillary right central incisor in vitro.
Materials and methods: The Orthodontic Force Simulator (Institut Straumann, Basel, Switzerland), a device proficient at evaluating the biomechanical performance of aligners, was used to examine buccopalatal translations of the maxillary right central incisor. The present authors used a human head model to prepare a model of the maxilla with independent teeth, which was then segmented and interfaced with the Orthodontic Force Simulator. Thirty aligners were crafted from ClearQuartz material (ClearCorrect, Round Rock, TX, USA) in a process that encompassed intraoral scanning, digital superimposition, 3D printing, thermoforming and laser trimming. The central incisor’s forces and moments were assessed across four scenarios combining flat/scalloped trimlines and buccal/palatal translation.
Results: The highest translational force (7.51 N) and tipping moment (15.94 Ncm) were recorded for palatal translation coupled with a flat trimline. This was followed in descending order by buccal translation with a flat trimline (5.49 N and 12.46 Ncm), palatal translation with a scalloped trimline (4.93 N and 10.64 Ncm), and buccal translation with a scalloped trimline (2.96 N and 6.58 Ncm). Each tested scenario generated a clinically relevant translational force; however, the presence of undesirable buccopalatal tipping moments indicated potential off-target movements in an in vivo context.
Conclusion: The present findings highlight the substantial influence of the aligner trimline design and direction of translation on force and moment generation. Flat trimlines and palatal translation were associated with higher forces and moments compared to scalloped designs and buccal translation, respectively. These findings underscore the importance of careful aligner design in achieving the desired orthodontic outcomes; however, further research is required to gain a comprehensive understanding of aligner–tooth interactions and their implications for clear aligner therapy.