08. chronology (lecture) - dentition

Condition of Teeth Condition of Teeth At Different AgesAt Different Ages

1- Teeth begin its calcification long before its date of eruption.

2- When tooth erupts the crown and about 1

3

of the root is completed.

3- Roots are completed after eruption by 1-1.5 years (for deciduous) and after eruption by 3 years (for permanent).

4- Roots of deciduous teeth begin resorption 3 years before shedding.

Generally:

Chronology Of Deciduous

Teeth

• Enamel organ for deciduous teeth appears from 7-9 w.i.u.

• Beginning of calcification of deciduous from 4-6 m.i.u.

• Deciduous Canines erupt after deciduous1st molars.

• Mandibular teeth erupt before maxillary teeth.

• Shedding occurs at the same date of eruption of successors.

• Shedding of deciduous teeth occurs from 7-11 years

For deciduous teeth:

A B C D E A B C D E

1 2 4 3 5

Lower before upper

Beg. Of Beg. Of calc. calc. (m.i.u)(m.i.u)

EruptionEruption(m.)(m.)

Root Root completed completed (Y)(Y)

BeginningBeginning

of root res.of root res.

AA

AA

BB

BB

CC

CC

DD

DD

EE

EE

454.5

6

76

78

24

1412

1618

20

1.5

3

2.5

3

-3 ye

ars

befo

re s

hedd

ing

Chronology Of permanent

Teeth

For permanent For permanent teeth:teeth:

*At birth, first permanent molar is the only permanent tooth showing evidence of calcification .

*Dates of eruption of permanent incisors is the same as deciduous incisors but in years.

*Premolars start calcification between 112 & 2

12 y .

*Lower teeth sequence of eruption is 1 2 3 4 5. *Upper teeth sequence of eruption is 1 2 3 5.

*Lower teeth erupts before upper opposing teeth. *First, second& third molars erupt at ages of 6,12,18

years respectively .

4

Beginning Beginning of calcof calc..

))monthmonth((

Crown Crown completedcompleted

EruptionEruption

(years)(years)

Root Root completedcompleted

11

11

22

22

33

33

3-4

73-4 -3

year

s

7

94-5

10-12

+3 ye

ars

11

8

6

Beginning Beginning of calcof calc..

Crown Crown completedcompleted

EruptionEruption

(years)(years)

Root Root completedcompleted

44

44

55

55

134

2

10

11-12

10

11-12

112 -

3-4

ye

ars

+3 ye

ars

212

Beginning Beginning of calcof calc..

Crown Crown completedcompleted

EruptionEruption

(years)(years)

Root Root completedcompleted

66

66

77

77

88

88

3y

6y

12y

At birth -

3-4

ye

ars

+3 ye

ars

8y 18y

• Permanent teeth ML cusp of lower 6. • No erupting teeth

½ crown

Less than1/2

Cusp tip

Occ.S Separate

cusp

ML cusp

6 months

start eruption

Crown&1/4 root

most of crowns formed C&D&E

Incisal 1/3 of 1&2

separate cusps of 6

cusp tip

1 year

AB

CDE6

13

2

2 years

ABCDE

6

13 245

3 years

All deciduous teeth erupted with fully formed teeth

More than ½ crown of 1&2 formed

½crown 3

small part of 4&5

crown of 6 completed

separate cusps of 7

Root of lower A resorped

B&C&D some amount of resorption

E no resorption

crown&1/3 root formed

less than 1/3 of the root formed

crowns of 3&4&5 formed

6 is erupted

crown of 7 not completed

7 years

7-8 years

7 years

BCDE

6

1

3

2

45

7

C&D&E most of their roots

resorbed

1&2 is erupted their root completed

3&4&5 not yet erupted &less than 1/3 of root formed

root of 6 completed

7 crown& less than 1/3 root formed

8 Calcified separate cusps are formed

All permanent teeth erupted except 8 .