An Efficient Distalization Technique Using Coil Springs and Mini Screws—A Finite Element Analysis

Background: More efficient molar distalization is demanded in orthodontics to shorten treatment times. In the present study, we propose a novel technique to improve force distribution to distalize molars more efficiently by using open-coil springs and an anchor screw. We conducted a finite element analysis to assess the efficiency of the proposed technique. Methods: A three-dimensional finite element model of an upper dental arch with brackets and an archwire was constructed based on cone-beam computed tomography. We analyzed two distalization methods: a conventional grouped distalization technique (NoSp model), and our proposed technique using open coils (Sp model). Finite element analyses were performed to evaluate long-term tooth movement in both techniques. Results: The distalization force was more evenly distributed in the Sp model than in the NoSp model. Moreover, less concentration of compressive stress in the periodontal ligament (PDL) was observed in the Sp model. The force systems of the two models became more similar as the distalization progressed. However, the NoSp model still showed higher stress concentration at the end of the simulation. Conclusions: Inserting open-coil springs between distalized teeth improved the distribution of the force significantly. The conventional grouped distalization method might cause stress concentration at the first premolar, indicating risks of the hyalinization of the PDL and root resorption.