Progress in Orthodontics

Table 1 Intergroup comparability (chi-square and t tests)

From: External root resorption with the self-ligating Damon system—a retrospective study

	Male		Female		Total
Damon	13		12		25
Conventional	15		12		27
Total	28		24		52
	X² = 0.06 DF = 1 P = 0.797^a
	Group 1—Damon n = 25		Group 2—conventional n = 27
	Mean	SD	Mean	SD	P
Initial age	16.04	5.20	16.77	5.32	0.623^b
Final age	18.06	5.51	18.47	5.43	0.788^b
T. time	2.02	0.68	1.70	0.56	0.078^b
MxII.	6.60	3.68	5.13	1.66	0.065^b
MdII.	6.36	2.93	5.40	1.60	0.144^b

MxII. maxillary irregularity index, MdII. mandibular irregularity index
^aChi-square test
^b t test

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