Primary Tooth Morphology And Chronology Of Eruption

Question 1

List 4 early problems that can occur in children’s mouths

Answer 1

1. Gingival cysts (Epstein’s pearls/Bohns nodules) - appear white
2. Congenital epulis
3. Natal or neonatal teeth
4. Eruption cysts - appear blue

Question 2

How is the primary dentition written using FDI notation?

Answer 2

Quadrants 5 6
7 8

Letters A B C D E used

Question 3

When do teeth start to form?

Answer 3

During week 5 of intra-uterine life

Question 4

When does hard tissue formation begin?

Answer 4

Week 13 IUL

Question 5

Describe the development of the maxillary central incisor in chronological order:
•hard tissue formation
•crown complete
• eruption
•root complete

Answer 5

1. Hard tissue formation. 13-16 weeks IUL
2. Crown complete 1.5 months after birth
3. Eruption 8-12 months
4. Root complete 33 months

Question 6

Describe the development of the maxillary second primary molar in chronological order

Answer 6

1. Hard tissue formation - 16-23 weeks IUL
2. Crown formation complete - 11 months after birth
3. Eruption - 25-33 months
4. Complete root formation - 47 months

Question 7

List the tooth crowns that are calcified at birth

Answer 7

1/2 of primary central incisors
1/3 of primary lateral incisors
Tip of primary canines
1/2 of first primary molars
1/3 of second primary molars
Tip of cusps of first permanent molars

Question 8

List some possible theories behind tooth eruption

Answer 8

1. Cellular proliferation at apex of tooth
2. Localised change in blood pressure/hydrostatic pressure
3. Metabolic activity within the PDL
4. Resorption of the overlying hard tissue

Question 9

How does the dental follicle appear on a radiograph?

Answer 9

Dark halo around unerupted tooth

Question 10

What process is considered essential to the process of tooth eruption?

Answer 10

Remodelling of bone and primary tooth tissue

Question 11

What is the main function of the dental follicle?

Answer 11

Follicle is activated to initiate osteoclastic activity in the alveolar bone ahead of the tooth in order to clear a path for tooth eruption

Question 12

What sequence does the primary dentition erupt in?

Answer 12

1. Central incisor (A)
2. Lateral incisor (B)
3. First primary molar (D)
4. Canine (C)
5. Second primary molar (E)

ABDCE

(As a general rule, lowers erupt before uppers except the lateral incisors)

Question 13

When does the lower central incisor erupt?

Give the FDI notation for these teeth

Answer 13

• 4-6 months

* 81 and 71

Question 14

When does the lateral incisor erupt?

Give the FDI notation

Answer 14

• 7-16 months

* 52, 62, 72, 82

Question 15

When do the 1st molars erupt?

Give the FDI notation

Answer 15

• 13-19 months

* 54,64,74,84

Question 16

When do the canines erupt?

FDI notation

Answer 16

• 16-22 months

* 53,63,73,83

Question 17

When do the second molars erupt?

Answer 17

• 15-33 months

* 55,65,75,85

Question 18

How long does it normally take for all teeth of the same series to erupt?

Answer 18

Less than 3 months

Question 19

At what age is the primary dentition complete?

Answer 19

2.5-3 years

Question 20

Is it normal for children of 1 year to still have no erupted teeth?

Answer 20

Yes - there is huge variation in eruption dates

Question 21

What are the main differences between the crowns of primary and permanent teeth?

Answer 21

1. Primary incisors are smaller in both crown and root proportions
2. Primary molars are wider mesiodistally than the permanent premolars which take their place
3. Primary molars have more bulbous crowns
4. Primary teeth usually whiter in colour

Question 22

What is a distinguishing feature of the upper right 1st primary molar?

Answer 22

Prominent mesio buccal tubercle

Question 23

What is an anatomically important feature on the upper right second primary molar?

Answer 23

Transverse ridge

- important to preserve if possible

Question 24

What is the main distinguishing feature of the lower right second primary molar?

Answer 24

3 buccal cusps (like lower 1st permanent molar)

Question 25

What are the main differences between the roots of primary and permanent teeth?

Answer 25

1. Roots of primary teeth tend to be narrower when compared with their permanent counterparts 2. Roots of primary molars are longer and more slender than the roots of the permanent molars - these roots also tend to flare apically to allow room in between for the developing permanent tooth crowns

Question 26

What are the main differences in primary and permanent tooth pulp? how does this effect you clinically?

Answer 26

1. Pulp chambers of the primary teeth are relatively large in proportion to the crowns that surround them 2. The pulp horns of primary teeth extend high occlusally - means pulp horns are closer to enamel than in permanent teeth - makes pupal exposure on cavity preparation more likely

Question 27

What is the main difference between root canals of primary and permanent teeth?

Answer 27

1. Primary root canals tend to be ribbon shaped with multiple interconnecting and accessory canals - clinically impossible to clean completely

Question 28

What are the main differences in hard tissue between primary and permanent teeth?

Answer 28

1. Enamel of primary teeth is relatively thin and has consistent depth 2. The thickness of coronal dentine is much thinner than in permanent teeth

Question 29

Why is spacing of the primary dentition desirable?

Answer 29

Reduces the likelyhood of overcrowding in the permanent dentition

Question 30

What is meant by leeway space in the primary dentition?

Answer 30

•extra mesio distal space occupied by the primary molars which are wider than the premolars which will replace them

Question 31

How big is the leeway space on the upper and lower arches?

Answer 31

Upper: 1.5mm per side Lower: 2.5mm per side

Question 32

In what age range does the mixed dentition stage occur?

Answer 32

6-11 years - this varies (Normally begins at age 6 - 1st permanent molar)

Question 33

What is normally the final primary tooth to be exfoliated from the mouth?

Answer 33

Upper primary canine

Question 34

In cases of overcrowding, what teeth are often excluded due to lack of space in the upper and lower arches?

Answer 34

Upper: canine Lower: second premolar

Question 35

What results in an increased A-P arch length in the permenant dentition

Answer 35

Proclined permanent incisors

Question 36

What is a potential trauma risk to the permanent teeth which relates to the path of eruption?

Answer 36

Trauma risk to permanent teeth if primary incisors are displaced towards the developing central incisors which normally erupt palatally to the primary incisors

Question 37

What causes transient spacing of the developing upper 1’s, referred to as the ‘ugly duckling stage’?

Answer 37

Close proximity of roots pushes teeth outwards | - problem is self correcting once the permanent dentition is established

Question 38

How long does root formation take in the permanent dentition

Answer 38

3 years