Fig. 1
Finite element models. Two group sets including six sub-models were presented. Set I (A1, B1, and C1) represents the initial distalization of the 2nd molar, Set II (A2, B2, and C2) simulated the initial distalization of the 1st molar after 2 mm distalization of the 2nd molar. Models A (A1, and A2) indicated maxillary models to simulate the upper-molar distalization using clear aligners without Class II elastics. Models B (B1, B2) were designed to simulate the upper-molar distalization using clear aligners in combination with Class II elastics by buttons. Models C (C1, and C2) were designed to simulate the upper-molar distalization using clear aligners in combination with Class II elastics by precision cutting. The red circles represent the temporal-mandibular joint