Table 3.

Mean Values MM and Number of Subjects for 14 Variables at the 4 Registration Points Measured on Study Models and the Differences in Mean Values Between Groups 1 and 2.

Variables	Group 1 (Canine-to-Canine Retainer)			Group 2 (Twistflex Retainer)
	n	Mean	SD	n	Mean	SD	P
Little's Irregularity Index
T0a	28	4.5	3.46	35	4.7	2.96	NSb
T1	28	1.9	1.36	36	1.6	1.07	NS
T2	26	3.2	2.01	36	3.4	2.16	NS
T3	24	4.2	2.52	28	4.4	2.31	NS
Available space, mand 3-3
T0	28	−1.9	2.59	35	−2.1	2.51	NS
T1	28	−0.1	0.45	36	−0.1	0.30	NS
T2	26	−1.3	1.16	36	−0.8	0.84	NS
T3	24	−2.0	1.45	28	−1.3	1.01	NS
Intercanine width
T0	27	26.3	1.92	34	25.6	1.72	NS
T1	28	26.2	1.63	36	25.8	1.66	NS
T2	26	25.7	1.49	36	25.2	1.63	NS
T3	24	25.2	1.62	28	24.7	1.66	NS
Intercanine perimeter distance
T0	27	24.3	1.24	34	23.5	1.42	NS
T1	28	24.9	1.12	36	24.1	1.59	NS
T2	26	24.1	0.89	36	23.3	1.66	NS
T3	23	23.4	1.13	28	22.7	1.88	NS
Lateral arch length, left 2-6
T0	28	20.2	2.60	36	20.3	2.49	NS
T1	28	18.9	3.65	36	19.4	3.32	NS
T2	26	18.6	3.64	36	18.9	3.52	NS
T3	24	18.4	3.57	28	18.8	3.46	NS
Lateral arch length, right 2-6
T0	28	19.9	2.47	36	20.0	2.45	NS
T1	28	18.4	3.57	36	19.5	3.35	NS
T2	26	17.7	3.80	36	19.1	3.28	NS
T3	24	17.4	3.69	28	19.0	3.29	NS
Lateral arch length, left central-6
T0	28	29.8	2.26	36	29.6	2.38	NS
T1	28	28.5	3.28	36	28.9	3.10	NS
T2	26	27.6	3.34	36	27.9	3.04	NS
T3	24	27.2	3.05	28	27.7	3.07	NS
Lateral arch length, right central-6
T0	28	29.5	2.19	36	29.6	2.57	NS
T1	28	28.0	3.22	36	29.0	3.20	NS
T2	26	27.2	3.26	36	28.1	3.13	NS
T3	24	26.8	3.11	28	27.9	3.12	NS
Tooth width, 32
T0	28	6.3	0.32	36	6.1	0.36	NS
T3	24	6.3	0.30	28	6.0	0.39	NS
Tooth width, 31
T0	28	5.7	0.33	36	5.5	0.31	NS
T3	24	5.7	0.32	28	5.5	0.33	NS
Tooth width, 41
T0	28	5.6	0.32	36	5.5	0.36	NS
T3	24	5.6	0.31	27	5.4	0.37	NS
Tooth width 42
T0	28	6.3	0.40	36	6.0	0.39	*
T3	24	6.3	0.41	28	5.9	0.36	**
Overjet
T0	28	6.3	3.32	36	7.5	3.04	NS
T1	28	3.2	0.91	36	3.3	1.13	NS
T2	26	3.6	1.58	36	3.9	1.68	NS
T3	24	3.7	1.91	28	4.0	1.46	NS
Overbite
T0	28	3.7	2.62	36	3.5	1.79	NS
T1	28	2.5	1.12	36	2.4	1.07	NS
T2	26	2.8	1.80	36	2.7	1.39	NS
T3	24	2.9	1.85	28	2.9	1.20	NS

^aT0 indicates before treatment; T1, after treatment; T2, 6 years after treatment; T3, 12 years after treatment.

^bNS indicates not significant; * P = .05; **P = .01.