Table 3. Comparison of chronological age (CA) and Willems’ dental age (DA) by gender and age group.

Gender	Age group (years)	N	Mean age ± SD (years)		Mean DA-CA (years)	p value#
			CA	DA
GIRLS	5	24	5.46 ± 0.33	5.47 ± 0.86	+ 0.01 ± 0.84	0.964
	6	39	6.57 ± 0.32	6.81 ± 0.70	+ 0.24 ± 0.64	0.033
	7	46	7.52 ± 0.26	7.39 ± 0.78	- 0.13 ± 0.75	0.191
	8	50	8.51 ± 0.31	8.46 ± 0.73	- 0.05 ± 0.63	0.765
	9	55	9.48 ± 0.30	9.52 ± 0.78	+ 0.04 ± 0.79	0.811
	10	55	10.55 ± 0.32	10.53 ± 0.81	- 0.02 ± 0.85	0.694
	11	40	11.44 ± 0.32	11.73 ± 0.89	+ 0.29 ± 0.84	0.032
	12	55	12.49 ± 0.32	12.53 ± 0.83	+ 0.04 ± 0.88	0.744
	13	57	13.46 ± 0.30	13.21 ± 0.71	- 0.25 ± 0.70	0.018
	14	59	14.48 ± 0.28	15.09 ± 0.93	+ 0.61 ± 0.93	< 0.001
	15	21	15.48 ± 0.27	15.63 ± 0.37	+ 0.15 ± 0.42	0.126
	Total	501	10.68 ± 2.87	10.76 ± 3.04	+ 0.08 ± 0.80	0.049
BOYS	5	23	5.56 ± 0.29	5.74 ± 0.73	+ 0.18 ± 0.73	0.301
	6	40	6.52 ± 0.31	6.62 ± 0.77	+ 0.10 ± 0.84	0.183
	7	58	7.48 ± 0.29	7.62 ± 0.78	+ 0.14 ± 0.73	0.153
	8	58	8.47 ± 0.29	8.69 ± 0.69	+ 0.22 ± 0.76	0.043
	9	78	9.46 ± 0.28	9.56 ± 0.88	+ 0.10 ± 0.90	0.410
	10	100	10.45 ± 0.29	10.65 ±0.82	+ 0.20 ± 0.80	0.015
	11	82	11.51 ± 0.30	11.53 ± 0.75	+ 0.02 ± 0.75	0.705
	12	91	12.44 ± 0.30	12.34 ± 0.70	- 0.10 ± 0.67	0.145
	13	82	13.41 ± 0.31	13.42 ± 0.76	+ 0.01 ± 0.81	0.891
	14	58	14.47 ± 0.31	14.54 ±0.68	+ 0.07 ± 0.75	0.553
	15	29	15.24 ± 0.25	15.59 ±0.76	+ 0.35 ± 0.82	0.048
	Total	699	10.81 ± 2.60	10.90 ± 2.66	+ 0.09 ± 0.80	0.002
Total sample		1200	10.75 ± 2.72	10.84 ± 2.83	+ 0.09 ± 0.80	< 0.001

^#Wilcoxon Signed Rank test: p ≤ 0.05 = significant