Table 3. ANOVA comparison of compensatory differences of the axial inclination of the maxillary first molars between groups within each stratification.

Classification	<12 years		12–16 years		>16 years		P value
	n	(Mean±s.d.)/ °	n	(Mean±s.d.)/ °	n	(Mean±s.d.)/ °
Angle classification
1	127	77.625±4.137	366	80.347±5.015	142	85.078±5.132	0.000**
2	145	75.645±5.055	309	77.041±5.130	93	82.147±6.085	0.000**
3	68	78.831±5.619	113	80.773±5.045	40	86.618±5.135	0.000**
P value		0.000**		0.000**		0.000**
Skeletal classification
1	132	77.805±4.384	350	79.907±5.026	106	85.329±4.895	0.000**
2	156	75.676±4.838	358	77.619±5.239	132	82.558±5.664	0.000**
3	52	79.070±5.888	80	82.311±4.879	37	87.647±5.855	0.000**
P value		0.000**		0.000**		0.000**
MP/SN classification
Low-angle	6	78.093±5.650	33	80.027±5.605	17	85.840±5.834	0.002**
Average angle	168	77.428±5.129	394	79.584±5.438	141	85.118±5.778	0.000**
High-angle	166	76.572±4.846	361	78.512±5.126	117	83.116±5.384	0.000**
P value		0.257		0.013*		0.010*
Total	340	77.022±5.006	788	79.112±5.327	275	84.311±5.693

ANOVA, analysis of variance; n, number of cases; MP/SN, anteroinferior crossing angle of the mandibular plane with the anterior cranial base plane.

^*P < 0.05, **P<0.01.