Table 3. Plaque index (mean and standard deviation) in the two groups at t0, t1 and t2, with intra-group and between groups differences.

	t0 Initial	t1 After 3 months	t2 After 6 months	t0 versus t1 comparison	t0 versus t2 comparison	t1 versus t2 comparison
Clear aligners (CA group)	0	0	0	n.s.	n.s.	n.s.
Multibrackets appliance (MB group)	0	0.7 ± 0.55	1.4 ± 0.5	t = -7.85 p = 0.001	t = -5.6 p = 0.001	t = -17.8 p = 0.001
CA group versus MB group comparison	n.s.	t = -7.85 p = 0.001	t = -17.8 p = 0.001

n.s. = not significant