Eruption and Exfoliation

Question 1

When does the primary dentition begin to erupt?
When is eruption complete?
How long does it take for root formation?

Answer 1

• start to erupt at approx. 6 months
• usually complete by age 3
• common to have spacing between anterior teeth
• root formation is complete by 18 months after eruption
• all calcify in utero

Question 2

At what age do primary teeth begin to exfoliate?
When is the permanent dentition eruption complete?
How long until root completion?

Answer 2

• primary teeth start to exfoliate at approx. 6 years
• complete by approx age 13, excluding 8’s
• root formation complete approx. 3 years after eruption
• anterior permanent teeth are significantly bigger

Question 3

Anterior permanent teeth are significantly bigger than primary teeth, how does the mouth cope with this?

Answer 3

Accommodated by:
- erupting into a bigger arc
- spacing in primary dentition helps
- growth of jaws
Buccal primary teeth are wider than permanent successors - difference is called leeway space
- greater in mandible (2.5mm) than the maxilla (1.5mm)
3, 4 and 5 are easily accommodated as they erupt, providing they have not had early loss of primary teeth

Question 4

What are some late changes in the permanent dentition?

Answer 4

• common to see lower incisor crowding during late teens/early 20s
• thought to be related to eruption of 8’s - not true
• due to late growth of mandible and general mesial migration of all teeth

Question 5

Give an overview of when the following events happen:
- tooth development starts
- tooth germs formed
- calcification starts
- first teeth erupt
- primary dentition complete

Answer 5

Tooth development starts: 6 weeks in utero
Tooth germs formed: 3rd-4th month i.u.
Calcification starts: 3rd-6th month i.u.
First teeth erupt: 6-7 months
Primary dentition complete: ~ 2.5 years

Question 6

When do the upper and lower A’s and B’s erupt?

Answer 6

Lower A’s: 6 months
Upper A’s: 7 months
Lower B’s: 7 months
Upper B’s: 8 months

Question 7

After the A’s and B’s have erupted, which teeth will erupt next and when?

Answer 7

D’s will erupt between 12-16 months
C’s: 16-20 months
E’s: 20-30 months

Question 8

Which permanent teeth erupt first and at what age?

Answer 8

Usually 6’s erupt then lower 1’s
- deciduous dentition begins to shed
Mixed dentition

Question 9

What age do 6’s, 1’s and 2’s erupt?

Answer 9

6’s: age 6
Lower 1’s: 6-7 years
Lower 2’s: 7-8 years
Upper 1’s: 7-8 years
Upper 2’s: 8-9 years

Question 10

When do 3’s erupt?

Answer 10

Lower 3’s: 9-10 years
Upper 3’s: 11-12 years

Question 11

At what age do 4’s and 5’s erupt?

Answer 11

10-12 years, maxillary can be before mandibular

Question 12

When do 7’s and 8’s erupt?
When is root completion?

Answer 12

7’s: 12-13 years
8’s: 17-21 years
Root completion 2-3 years after eruption