Normal Dental development

Question 1

How many permanent teeth are there?

Answer 1

32

Question 2

How many primary teeth are there?

Answer 2

20

Question 3

When do a’s erupt?

Answer 3

6-9 months (lower then upper)

Question 4

When do b’s erupt?

Answer 4

7-10 months (lower then upper)

Question 5

When do d’s erupt?

Answer 5

12-16 months (all similar time)

Question 6

When do c’s erupt?

Answer 6

16-20 months (lower then upper)

Question 7

When do e’s erupt?

Answer 7

23-30 months (lower then upper)

Question 8

In which order do the primary dentition erupt?

Answer 8

a -> b -> d -> c -> e

Question 9

By which age do we have most of our primary teeth?

Answer 9

2.5 y/o

Question 10

How long after eruption of the primary dentition does root formation complete?

Answer 10

12-18 months

Question 11

Which teeth erupt at 6-7 y/o?

Answer 11

Lower 1’s and 6’s
Upper 6’s
Upper 1’s

Question 12

Which teeth erupt at 7-8 y/o?

Answer 12

Lower 2’s

Question 13

Which teeth erupt at 8-9 y/o?

Answer 13

Upper 2’s

Question 14

Which teeth erupt at 9-11 y/o?

Answer 14

Lower 3’s

Question 15

Which teeth erupt at 10-12 y/o?

Answer 15

All 4’s then all 5’s

Question 16

Which teeth erupt at 11-13 y/o?

Answer 16

All 7’s

Question 17

Which teeth erupt 17-25 y/o?

Answer 17

All 8’s

Question 18

In which order do the permanent dentition erupt?

Answer 18

Lower 1's and 6's
Upper 6's
Upper 1's
Lower 2's
Upper 2's
Lower 3's
Upper 3's
All 4's
All 5's
All 7's
All 8's

Question 19

How long after eruption of permanent teeth does root formation complete?

Answer 19

2-3 yrs

Question 20

What is the leeway space?

Answer 20

The difference between the combined mesiodistal width of the primary canine and molars and the permanent canine and premolars

Question 21

What is the leeway space in the maxillary arch?

Answer 21

1.5mm

Question 22

What is the leeway space in the mandibular arch?

Answer 22

2.5mm (due to larger second molar)

Question 23

What is the occlusion like at birth?

Answer 23

Gum pads occlude distally
Anterior oval opening = suckling
Fleshy labial frenum

Question 24

What is the occlusion like at 6-10 months?

Answer 24

Maxillary incisors erupt labial to the mandibular

Incisors are more upright than permanent ones

Question 25

What is the occlusion like at 36 months?

Answer 25

Dentition is complete
Incisors vertical and spaced
Deep overbite
Anthropoid spaces mesial to maxillary canine and distal to mandibular canine
Flush terminal plane
Distal edges of the maxillary and mandibular e are matched

Question 26

What is occlusion like at 6 years?

Answer 26

Overbite decreases
Spacing of anterior teeth
Attrition of incisors
Eruption of first permanent molar
Mesial migration of primary molars = closure of anthropoid spaces
Permanent molars = class I or half class II relationship

Question 27

What is the class I relationship?

Answer 27

Where mesiobuccal cusp of U6’s is in line with the fissure of L6’s

Question 28

What is occlusion like at 7-8 years?

Answer 28

Maxillary central incisors erupt spaced and more proclaimed than primary predecessors
Maxillary lateral incisors are often more distally inclined
Maxillary incisors labial to mandibular

Question 29

What is occlusion like at 9-12 years?

Answer 29

Primary canines and molars exfoliate, permanent molars drift mesially into leeway space to form class I relationship
Maxillary permanent canines should be palatable buccal at 10 y/o unless gone astray (often erupt buccally)

Question 30

What is occlusion like at 11-12 years?

Answer 30

Incisal spacing reduced by eruption of canines

Question 31

What is occlusion like at 11-13 years?

Answer 31

All primary teeth have exfoliated
1st permanent molars in class I relationship
2nd permanent molars erupting

Question 32

What are the different deviations from normal/ideal occlusion (7)?

Answer 32

Anterior open bite
Deviation of eruption sequence
Attrition
Natal/neonatal teeth
Ectopic canines
Early tooth loss
Delayed tooth loss

Question 33

What is an anterior open bite?

Answer 33

Where front incisors do not touch = vertical gap between them
Due to thumb sucking/ tongue thrust or skeletal
Depends on child (if old tell them to stop sucking thumb)

Question 34

What is the significance in deviation of eruption sequence?

Answer 34

Dates may vary but sequence should not

Concern if contralateral counterpart not erupted 6 months later (won’t erupt at same time)

Question 35

What is attrition?

Answer 35

Normal

But significant tooth loss and pulp exposure is not (causes should be addressed)

Question 36

What are ectopic canines?

Answer 36

Canines in wrong place

• often not palpable buccally at age 10
• can do damage and cause resorption of roots of permanent teeth if in palate etc.)

Question 37

What are natal/neonatal teeth?

Answer 37

Teeth present at birth or soon after (usually the lower incisors)
Should be removed if cause aspiration risk/ interfering with feeding or traumatising the soft tissue
n.b. usually part of normal sequence but occasionally can be supernumerary teeth

Question 38

What is the consequence of early tooth loss?

Answer 38

Can delay permanent tooth eruption (gum heals over)
Can accelerate eruption of the successor (if comes out very close to natural tooth eruption)
Cause of space loss and crowding in the permanent arch

Question 39

What is the consequence of delayed tooth loss?

Answer 39

May be because successor is missing
Common that permanent tooth starts erupting before the primary is lost but if fails to resorb on further eruption can be extracted

Question 40

Why may an orthodontist be required?

Answer 40

Crowding / spacing in late dentition
Increase/reverse overjet
Increase or reverse overbite or overbite
Crossbite
Rotation of teeth
Unerupted / ectopic canines