Table 2.

t-Test comparisons of arch dimensional changes between the First group vs. the RME group

Variables	First group			RME group				Difference	p Value	95% CI of the Difference
	Mean	SD		Mean		SD				Lower	Upper
53–63, mm	1.89	1.56	4.18		2.01		-2.28		0.002*	-3.67	-0.88
14–24, mm	2.83	1.90	5.05		1.81		-2.22		0.003*	-3.61	-0.83
55–65, mm	1.93	1.75	5.52		1.31		-3.59		0.000*	-4.70	-2.49
16–26, mm	2.43	1.42	5.32		1.13		-2.89		0.000*	-3.78	-1.99
Arch depth, mm	-0.46	0.86	-0.36		0.75		-0.10		0.715	-0.67	0.46
Arch perimeter, mm	1.69	2.01	3.32		1.86		-1.63		0.020*	-2.98	-0.28
Intercanine dentoalveolar width, mm	1.05	1.14	2.65		2.61		-1.60		0.028*	-3.02	-0.19
Intermolar dentoalveolar width, mm	1.43	0.86	4.01		1.08		-2.57		0.000*	-3.25	-1.89
Inclination of the molars, °	-4.49	6.87	-9.64		7.02		5.14		0.038*	0.29	10.00

First, Invisalign First System; RME, acrylic splint rapid maxillary expander; NG, natural growth; 53–63, intercanine width; 14–24, first interpremolar width; 55–65, second interdeciduous molar width; 16–26, first intermolar width; *p < 0.05 indicates statistical significance