Table 1.

Mechanical properties of the involved structures.

	Young's modulus (MPa)	Poisson's ratio	References
Cortical bone	13.7 × 103	0.30	Barone et al. [23]
Spongious bone	1.37 × 103	0.30	Barone et al. [23]
Composite attachment	12.5 × 103	0.36	Gomez et al. [14]
Plastic aligner	528	0.36	Gomez et al. [14]
Enamel	4.1 × 104	0.30	Gomez et al. [14]
PDL (nonlinear elastic)∗		0.45	Qian et al. [20]

PDL, periodontal ligament. ^∗Nonlinear mechanical properties for PDL were based on experimental data.