CDH 1 - dental development

Question 1

What are the anatomical differences between primary teeth vs permanent teeth?

Answer 1

• primary teeth are whiter
• primary teeth have larger pulp chamber/pulp:crown ratio
• primary teeth more bulbous
• primary teeth have more divergent roots
• primary teeth have thinner enamel

Question 2

What is the clinical implication of primary teeth being whiter than permanent teeth?

Answer 2

permanent teeth seem “yellow” in comparison

Question 3

What are the clinical implications of primary teeth having larger pulp chambers than permanent teeth?

Answer 3

• need to be more careful with restoration prep etc
• caries progresses to pulp much quicker

Question 4

What is the clincian implication of primary teeth being more bulbous than permanent teeth?

Answer 4

much broader contact point: more chance of proximal caries

Question 5

When do primary teeth start to erupt?

Answer 5

6 months

Question 6

Which primary teeth erupt first?

Answer 6

lower central incisors (lower As)

Question 7

When is the primary dentition complete?

Answer 7

~30 months (2 and a half years)

Question 8

When does the mixed dentition stage begin?

Answer 8

6 years

Question 9

Which teeth erupt first in mixed dentition stage?

Answer 9

lower central incisors

Question 10

What are the 2 main stages of the mixed dentition stage?

Answer 10

6-8 years: incisors and 1st molars
10-12 years: canines, premolars, and 2nd molars

Question 11

When is the permanent dentition established by?

Answer 11

around 12 years

Question 12

What are the main features of the established permanent dentition?

Answer 12

• Molar relationship
• No crowding
• No spacing
• No rotated teeth
• Occlusal plane flat or mild curve of Spee

Question 13

When should the upper canines be palpable in the buccal sulcus by?

Answer 13

from ~9 years

Question 14

What is the Curve of Spee?

Answer 14

• the curvature of the mandibular occlusal plane
• begins at the tip of the lower incisors
• follows the buccal cusps of the posterior teeth
• ends at the anterior mandibular ramus
• sagittal plane descriptor

Question 15

What is the relevance of the Curve of Spee?

Answer 15

gives indication of how things are developing, mainly from orthodontic POV

Question 16

When do primary teeth develop (in utero)?

Answer 16

• at ~28 days in utero, a continuous plate of epithelium arises in the maxilla and mandible
• by 37 days in utero, a well-defined, thickened layer of epithelium overlying the cell-derived mesenchyme of the neural crest delineates the dental lamina
• 10 areas in each jaw become identifiable at the location of each primary tooth

Question 17

What is molar incisor hypomineralisation (MIH)?

Answer 17

enamel of 6s, 1s and 2s hasn’t formed properly, enamel not as hard, less resistant to caries and occlusal forces etc

Question 18

How many children in the UK are effected by MIH?

Answer 18

around 5%

Question 19

What are the features of the primary dentition?

Answer 19

• spaced anteriors
• primate spaces
• shallow overjet and overbite
• class I molar relationship
• primary mandibular 2nd molar is wider than maxillary 2nd molar
• vertical inclination of the anteriors

Question 20

Why is there spacing of the primary dentition?

Answer 20

to accommodate the permanent teeth

Question 21

Where does the spacing in the primary dentition come from?

Answer 21

• interdental spacing
• arch width increase
• greater labial inclination of permanent teeth
• increase in primary inter-canine width

Question 22

How much greater is the combined mesio-distal width of the permanent incisors, than the primary incisors?

Answer 22

7.6mm greater in the maxillary arch
6mm greater in the mandibular arch

Question 23

Why is ‘Leeway space’ needed?

Answer 23

because the combined mesio-distal width of C,D,E is greater than the combined mesio-distal width of 3,4,5

Question 24

What is the leeway space in the upper arch?

Answer 24

0.9mm per quadrant

Question 25

What is the leeway space in the lower arch?

Answer 25

1.7mm per quadrant

Question 26

What does the extra space from the leeway space contribute to?

Answer 26

establishing a class I molar relationship

Question 27

What are the effects of early loss of primary teeth on permanent teeth eruption?

Answer 27

• formation of fibrous tissue over the eruption tooth
• delayed eruption

however,

• if the develops permanent tooth has 1/3 to 2/3 of the root formation completed, there will be accelerated eruption

Question 28

What is a Class 1 incisor relationship?

Answer 28

the lower incisor edges occlude with the upper central incisor central plateaus

Question 29

What is a Class 2 division 1 incisor relationship?

Answer 29

• the lower central incisor edges sit posteriorly relative to the upper central incisor central plateaus
• the upper central incisors are either proclined, or of an average inclination
• there is often an increased overjet

Question 30

What is a Class 2 division 2 incisor relationship?

Answer 30

• the lower central incisor edges sit posteriorly relative to the upper central incisor central plateaus
• the upper central incisors are retroclined
• there is often a minimal overjet

Question 31

What a Class 3 incisor relationship?

Answer 31

• the lower central incisor edges sit anteriorly relative to the upper central incisor central plateaus
• the overjet is reduced or reversed

Question 32

What is a Class I molar relationship?

Answer 32

the maxillary mesiobuccal cusp and the mandibular buccal groove are in line

Question 33

What is a Class II molar relationship?

Answer 33

mandibular molars moved backwards
- mandibular buccal groove behind the maxillary mesiobuccal cusp

Question 34

What is a Class III molar relationship?

Answer 34

maxillary molars moved backwards
- mandibular buccal groove in front of the maxillary mesiobuccal cusp

Question 35

What teeth should you check in a 9 year old patient?

Answer 35

‘When a child of 9 arrives, think 3s, 6s and 5s’
- Check for canines, condition of 6s, 5s commonly missing in hypodontia

Question 36

What are the most commonly missing teeth?

Answer 36

2s, 5s and 8s