Mechanical Characterization of Thermoplastic Aligner Materials: Recommendations for Test Parameter Standardization

Table 4

Measured forces and calculated stresses (MPa) at the individual deflection depths for thermoformed specimens (TF) using different thermoforming forms. The SD values represent the standard deviation of the corresponding forces. Force and stress reduction due to thermoforming are given as percentage values.

Original foil thickness (mm)	Deflection depth (mm)	Raw foil			TF with flat metal plate			TF with stone model base			TF with round stone disc			TF with stone roof form
		Mean force (N)	SD	Stress (MPa)	Mean force (N)	SD	Stress (MPa)	Mean force (N)	SD	Stress (MPa)	Mean force (N)	SD	Stress (MPa)	Mean force (N)	SD	Stress (MPa)
0.4	0.2	2.66	0.27	16.14	1.69	0.16	14.61	1.16	0.36	13.45	1.71	0.14	14.61	1.03	0.07	13.45
0.5	0.15	6.27	0.21	16.14	3.38	0.25	14.70	1.53	0.13	12.97	2.89	0.41	14.41	1.57	0.15	12.97
0.625	0.15	7.63	0.11	18.16	4.15	0.97	17.30	2.33	0.08	15.57	3.72	0.60	16.72	1.61	0.22	14.99
0.75	0.10	12.22	0.19	14.80	6.35	0.41	14.03	3.93	1.25	13.45	7.67	0.35	14.41	2.02	0.27	12.49
Reduction					−44%			−67%			−44%			−75%