Table 2.

Paired t-Tests From Objective and Subjective Analysis of Invisalign and Fixed Groups at T₀, T₁, and T₂ ^a

	Invisalign Group (n = 24)			Fixed Group (n = 20)
	Mean	SD	P Value	Mean	SD	P Value
Upper boundary frequency (MHz)
T0 × T1	–0.31	0.37	<.01**	–0.11	0.37	.19
T1 × T2	0.16	0.27	.01*	0.01	0.32	.89
T0 × T2	–0.15	0.29	.02*	–1.39	0.51	.06
Patient perception of speech alteration (mm)
T1 × T2	39.99	17.91	.02*	26.15	17.58	0.30

^aSD indicates standard deviation.

^*Significant by the Student's t-test at P < .05.

^**Significant by the Student's t-test at P < .01.