Biomechanical Analysis of Dental Germ Displacement Induced by Rapid Maxillary Expansion Appliances and Orthodontic Aligners: A Finite Element Study

Objective: The effects of maxillary expansion are well understood, but the movement of tooth germs is still underexplored. The current study aims to examine the displacement of tooth germs by rapid maxillary expansion (RME) and aligners via finite element analysis. Methods: A maxilla in the mixed dentition stage was modeled for finite element analysis with a rapid maxillary expander and aligner. Expansion forces simulating displacements on the midpalatal surface were applied. The distribution of von Mises stresses and the displacement values of tooth germs were obtained. Results: The maximum displacement value among the dental germs (1.439 mm) occurred at tooth number 14 in the x direction with the RME appliance, and the lowest displacement value (0.026 mm) occurred at tooth number 23 in the x direction with the aligner. In all directions, the RME appliance produced higher displacement values for each tooth. RME showed stress concentration in the midpalatal and circummaxillary regions, whereas aligner expansion produced mainly dentoalveolar stress distribution. Conclusions: Tooth germ displacement was greater with the RME appliance than with the aligner system. Greater displacement was observed in regions where primary tooth was absent. These findings suggest that orthodontic expansion forces may influence developing permanent tooth germs and should be considered during treatment planning in the mixed dentition period.