A Test of the Demirjian method of dental ageing using a mixed population sample from Northern Ontario

Figures & data

Table 1. Breakdown of sample population by age and sex.

	For validation of Demirjian model		For validation of Sudbury-specific model
Age Group (yrs)	Boys	Girls	Boys	Girls	Total
5.0–6.9	6.0	5.0	0	0	11
7.0–8.9	26.0	18.0	5	9	58
9.0–10.9	23.0	27.0	5	11	66
11.0–12.9	23.0	34.0	10	2	69
13.0–14.9	12.0	12.0	1	3	28
15.0–16.0	3.0	2.0	0	0	5
Total:	93	98	21	25	237

Figure 1. Differences between estimated and actual ages for girls using Demirjian’s centile charts (p<0.001).

Figure 2. Differences between estimated and actual ages for boys using Demirjian’s centile charts (p<0.01).

Table 2. Results from single sample t-test comparing the actual ages and ages estimated using Dermirjian's original model for girls.

Comparing Means [t-test assuming equal variances (homoscedastic)]
Descriptive statistics
VAR	Sample size	Mean	Variance
Estimated age	93.00000	11.53817	7.90236
Actual age	93.00000	10.29937	5.76375
Summary
Degrees of freedom	184.00000	Hypothesized mean difference	0.00000
Test statistics	3.23162	Pooled variance	6.83305
Two-tailed distribution
p-level	0.00146	t critical value (5%)	1.97294
One-tailed distribution
p-level	0.00073	t critical value (5%)	1.65318
G-criterion
Test statistics	0.12168	p-level	0.06838
Critical value (5%)	0.14300
Pagurova criterion
Test Statistics	3.23162	p-level	0.99854
Ratio of variances parameter	0.57825	Critical value (5%)	0.06279

*α-level of 0.05 was used

†Reproduced from StatPlus:mac LE 2009

Table 3. Results from single sample t-test comparing the actual ages and ages estimated using Dermirjian's original model for boys.

Comparing Means [t-test assuming equal variances (homoscedastic)]
Descriptive statistics
VAR	Sample size	Mean	Variance
Estimated age	96.00000	93.45625	68.47701
Actual age	96.00000	10.72558	4.52416
Summary
Degrees of freedom	190.00000	Hypothesized mean difference	0.00000
Test statistics	94.87183	Pooled variance	36.50058
Two-tailed distribution
p-level	0.00000	t critical value (5%)	1.97253
One-tailed distribution
p-level	0.00000	t critical value (5%)	1.65291
G-criterion
Test statistics	2.99273	p-level	0.00000
Critical value (5%)	0.14300
Pagurova criterion
Test Statistics	94.87183	p-level	1.00000
Ratio of variances parameter	0.93803	Critical value (5%)	0.06285

*α-level of 0.05 was used

†Reproduced from StatPlus:mac LE 2009

Figure 3. Sudbury-specific model for girls with regression equation and R² value.

Figure 4. Sudbury-specific model for boys with regression equation and R² value.

Figure 5. Differences between estimated and actual ages for girls using the Sudbury-specific centile charts.

Figure 6. Differences between estimated and actual ages for boys using the Sudbury-specific centile charts.

Figure 7. The correlation between the actual and estimated ages for girls and R² value.

Figure 8. The correlation between the actual and estimated ages for boys and R² value.

Figure 9. Proportions of cases with the maximum number of stages different, testing for intra-observer agreement.

Figure 10. Proportions of cases with the maximum number of stages different, testing for inter-observer agreement.

Table 4. Summary of the previously completed population studies for Demirjian's method.

			Sample size
Ref. No.	Country	Province	Girls	Boys	Age Range (yrs)
[39]	Australia	Melbourne	216	451	15–25
[35]	Australia	Perth	60	83	4.6–14.5
[40]	Australia	Perth	71	73	3.6–14.5
[4]	Australia	Sydney	1624	1637	2–14
[7]	Belgium	Leuven	1255	1268	1.8–18.0
[20]	Canada	Ontario (Historic Population)	(241 total)	<15
[41]	Chile	Biobio	(159 total)	3-14
[17]	China	Sichuan	228	217	8–16
[8]	China	Southern	103	101	5–7
[36]	England	London (Historic Population)	23	40	0–5.4
[26]	Germany		420	0	7–15
[42]	India	Karnataka	348	199	7–25
[46]	India	Central India	165	175	5–14
[31]	International	Aust, Belg, End, Fin, France, Can, S. Korea, Swe	4742	4835	2–25
[12]	International	Aust, Belg, End, Fin, France, Can, S. Korea, Swe	(9002 total)	2-16.99
[14]	International	Aust, Belg, End, Fin, France, Can, S. Korea, Swe	4661	4710	2–18
[43]	Iran	Mashhad	170	141	6–13
[9]	Korea	Seoul	1691	1610	4–26
[13]	Korea	Seoul	729	754	3–16
[16]	Malaysia	Kelantan	214	214	7–15
[44]	Malaysia	Kuala Lumpur	(991 total)	5-15
[38]	New Zealand		723	600	2.5–13.9
[5]	Peru	Lima	152	135	9.5–16.5
[10]	Saudi Arabia	Riyadh	85	91	3–17
[11]	Spain	Galicia	157	151	2–10
[2]	Spain	Santiago	398	445	3–17
[32]	Sweden	Malmo	150	150	3.5–12.5
[34]	Turkey	Eastern	441	366	7–15
[15]	Turkey	Samsun	443	457	4–12
[37]	USA	Detroit	89	98	6–12
[45]	USA	Tennessee	(1200 total)	14-24
[11]	Venezuela	Merida	97	196	2–10

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