Accuracy assessment of dental age estimation with the Willems, Demirjian and Nolla methods in Spanish children: Comparative cross-sectional study

Table 1 Distribution of the sample by age groups and sex

Age groups	Total	Mean	SD	Girls	Boys
4-6.9	122	6.43	0.52	59	63
7-7.9	119	7.55	0.30	65	54
8-8.9	136	8.45	0.29	69	67
9-10.9	130	9.93	0.57	67	63
11-13.9	97	12.14	0.61	42	55
Total	604			302	302
SD Standard deviation