Anchorage onto deciduous teeth: effectiveness of early rapid maxillary expansion in increasing dental arch dimension and improving anterior crowding

Progress in Orthodontics

Table 3 Descriptive statistics and statistical analysis of the treated patients at T3 and the control groups

	Groups				Comparison among groups
	Treated group	Children with a lateral cross-bite	Children without a lateral cross-bite	Adolescents with a normal occlusion	p value
	n = 20	n = 20	n = 20	n = 20
Mean age (SD), years	9.8(1.3)	9.0(0.9)	9.2(1.1)	14.3(2.4)
Inter-canine width
mean (SD), mm	32.2(2.0)	30.3(3.1)	31.8(2.0)	-	0.0353*
95 % CI	31.3 to 33.1	28.8 to 31.7	30.9 to 32.7
Inter-molar width
mean (SD), mm	49.6(2.3)	44.5(2.4)	47.9(2.9)	50.6(2.8)	<0.001^†
95 % CI	48.5 to 50.6	43.3 to 45.6	46.5 to 49.2	49.4 to 52.1
Inter-molar depth
mean (SD), mm	29.8(1.7)	31.8(2.2)	32.1(2.0)	29.0(1.6)
95 % CI	29.0 to 30.6	30.8 to 32.9	31.2 to 33.0	28.3 to 29.8	<0.001^‡
Irregularity index
median (Iqr)^§, mm	2.4(1.4)	3.2(2.9)	4.0(4.0)	-	0.0094^‡

*One-way ANOVA (F _(2,57) = 3.55; power of the test = 98 %; rho = 0). Significant pair differences (Bonferroni test): treated group vs children with a lateral cross-bite (p = 0.042). ^†One-way ANOVA (F _(3,76) = 21.60; power of the test = 100 %; rho = 0). Significant pair differences (Bonferroni test): treated group vs children with a lateral cross-bite (p < 0.001) and adolescents with a normal occlusion vs both children with a lateral cross-bite (p < 0.001) and children without a lateral cross-bite (p = 0.005). ^‡One-way ANOVA (F _(3,76) = 12.86; power of the test = 99 %; rho = 0). Significant pair differences (Bonferroni test): treated group vs both children with a lateral cross-bite (p = 0.006) and children without a lateral cross-bite (p = 0.001); adolescents with a normal occlusion vs both children with a lateral cross-bite (p < 0.001) and children without a lateral cross-bite (p < 0.001). ^§Iqr is interquartile range. ^ǂKruskal-Wallis equality-of-populations rank test. Significant pair differences (two-sample Wilcoxon rank-sum test): treated patients vs children with a lateral cross-bite (p = 0.0094) and children without a lateral cross-bite (p = 0.0080)