Chronology of odontogenesis and age determination from radiographs

1. Chronology and Age
determination from
Radiograph
BY:
Mennat Allah Alkaram
Under supervision of:
Professor Nagwa Khattab

2. What’s chronology ?
a study which deals with the timings of
various stages of tooth development

3. Physiological stages of tooth
development :
 Initiation stage
 Proliferation
 Histodeffrentiation
 Morphodefrintiation
 Apposition stage
Dental anomalies as Gemination , Fusion , dilacerations ,
hypocalcefication , tetracycline staining and fluorosis take
place in corresponding stage .

4. Chronology of deciduous teeth
Upper
A B C D E
7-8 M 8-9 M 18 M 14 M 24 M
Lower
A B C D E
6-7 M 7-8 M 16 M 12 M 20 M

5. Chronology of deciduous teeth
Upper
A B C D E
7-8 M 8-9 M 18 M 14 M 24 M
Lower
A B C D E
6-7 M 7-8 M 16 M 12 M 20 M

6. Chronology of Permanent teeth
7-8y 8-9 12-13 10-11 11-12 6-7 12-13
1 2 3 4 5 6 7
1 2 3 4 5 6 7
6-7 7-8 9-10 10-11 11-12 6-7 11-12

7. Chronology of Permanent teeth
7-8y 8-9 12-13 10-11 11-12 6-7 12-13
1 2 3 4 5 6 7
1 2 3 4 5 6 7
6-7 7-8 9-10 10-11 11-12 6-7 11-12

9. Eruption Formula
Tooth eruption
(primary)
Root completion of
primary teeth
Starting of root
resorption
Shedding of
deciduous tooth
Root completion of
permanent tooth
+ 1(incisor) or
1.5y(canine or
molars)
+ 3y
+ 3 to 5y
+ 1.5 to 2.5y

10. Radiographic Tips
If erupted
6 y or above
If not erupted
Look at its root
closed Not closed
9y or
above
Btw. 6y , 9y
according to
amount of root
formed
Below 6y
Above 4.5 y
Bifurcation
is formed
Bifurcation
is not
formed
Below 4.5

11. • Bifurcation of 6 is at  4.5 years
• Bifurcation of 7 is at 8.5 years
• Root completion of permanent teeth takes 3years
• For tooth to erupt so  1/2 to 3/4 root must be
formed
Radiographic Tips

12. 5-6 yrs 6-7 yrs
7-8 yrs 8-9 yrs
8- 9 yrs

13. 4.5 – 5.5 Years
If not erupted
Below 6y
Above 4.5 y
Bifurcation
is formed

14. 6 – 7 Years
If erupted
6 y or above
Look at its root
Not closed
Btw. 6y , 9y
according to
amount of root
formed

15. 8 – 9 Years
If erupted
6 y or above
Look at its root
Not closed
Btw. 6y , 9y
according to
amount of root
formed

16. 9 – 10 Years
If erupted
6 y or above
Look at its root
closed
9y or
above

17. 10 – 11 Years
If erupted
6 y or above
Look at its root
closed
9y or
above

18. 11 – 12 Years
If erupted
6 y or above
Look at its root
closed
9y or
above

19. 11 – 12 Years
If erupted
6 y or above
Look at its root
closed
9y or
above

20. If erupted
6 y or above
Look at its root
closed
9y or
above
12-13 y

21. Importance of dental chronology study:
• Differentiate normal from abnormal and explanation of causes
of pathological condition : (tetracycline stain , delayed
eruption )
• Parent counseling and education ( food intake during
pregnancy )
• Prevention of anomalies related to drug intakes during tooth
development (tetracycline is contraindicated before 8 years)

22. Test Yourself

23. 1

24. 2

25. 3

26. 4
13-14 years

27. 5

28. 6

29. 7

30. 8

31. 9

32. 10

33. Thank you