抄録
Orthodontic treatment with clear aligners is attracting attention, and various mechanical analyses are being conducted to improve simulation accuracy. Molar distalization in this type of treatment is considered highly predictable. However, methods for determining the regions that receive orthodontic force from the aligner are currently insufficient. Therefore, the objective of this study was to employ a two-dimensional birefringence measurement system using the optical phase difference proposed by Shimada et al. to visualize the area and distribution of orthodontic force during molar distalization in clear aligner orthodontic treatment. In addition, we quantitatively evaluated the impact of molar distalization. Four types of clear aligners were prepared: a control aligner, second molar aligners only （#27）, and first-and-second molar aligners （#26 and #27）, with distalization distances of 0.25mm and 0.50mm. Subsequently, we compared the orthodontic forces applied by the clear aligners to the models. A two-dimensional birefringence measurement system （WPA-200-NIR） was used to calculate the mechanical strain energy from the generated optical phase difference. When the first and second molars （#26 and #27） were distalized, greater movement distance resulted in a lower load on the terminal molar. Furthermore, although the load decreased on the canines, the load on the anterior teeth increased. These results suggest that during molar distalization in clear aligner orthodontics, careful consideration must be given to the distalization distance and the number of teeth to be distalized.
