CDH 1 - dental development Flashcards
What are the anatomical differences between primary teeth vs permanent teeth?
- 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
What is the clinical implication of primary teeth being whiter than permanent teeth?
permanent teeth seem “yellow” in comparison
What are the clinical implications of primary teeth having larger pulp chambers than permanent teeth?
- need to be more careful with restoration prep etc
- caries progresses to pulp much quicker
What is the clincian implication of primary teeth being more bulbous than permanent teeth?
much broader contact point: more chance of proximal caries
When do primary teeth start to erupt?
6 months
Which primary teeth erupt first?
lower central incisors (lower As)
When is the primary dentition complete?
~30 months (2 and a half years)
When does the mixed dentition stage begin?
6 years
Which teeth erupt first in mixed dentition stage?
lower central incisors
What are the 2 main stages of the mixed dentition stage?
6-8 years: incisors and 1st molars
10-12 years: canines, premolars, and 2nd molars
When is the permanent dentition established by?
around 12 years
What are the main features of the established permanent dentition?
- Molar relationship
- No crowding
- No spacing
- No rotated teeth
- Occlusal plane flat or mild curve of Spee
When should the upper canines be palpable in the buccal sulcus by?
from ~9 years
What is the Curve of Spee?
- 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
What is the relevance of the Curve of Spee?
gives indication of how things are developing, mainly from orthodontic POV
When do primary teeth develop (in utero)?
- 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
What is molar incisor hypomineralisation (MIH)?
enamel of 6s, 1s and 2s hasn’t formed properly, enamel not as hard, less resistant to caries and occlusal forces etc
How many children in the UK are effected by MIH?
around 5%
What are the features of the primary dentition?
- 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
Why is there spacing of the primary dentition?
to accommodate the permanent teeth
Where does the spacing in the primary dentition come from?
- interdental spacing
- arch width increase
- greater labial inclination of permanent teeth
- increase in primary inter-canine width
How much greater is the combined mesio-distal width of the permanent incisors, than the primary incisors?
7.6mm greater in the maxillary arch
6mm greater in the mandibular arch
Why is ‘Leeway space’ needed?
because the combined mesio-distal width of C,D,E is greater than the combined mesio-distal width of 3,4,5
What is the leeway space in the upper arch?
0.9mm per quadrant
What is the leeway space in the lower arch?
1.7mm per quadrant
What does the extra space from the leeway space contribute to?
establishing a class I molar relationship
What are the effects of early loss of primary teeth on permanent teeth eruption?
- 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
What is a Class 1 incisor relationship?
the lower incisor edges occlude with the upper central incisor central plateaus
What is a Class 2 division 1 incisor relationship?
- 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
What is a Class 2 division 2 incisor relationship?
- 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
What a Class 3 incisor relationship?
- the lower central incisor edges sit anteriorly relative to the upper central incisor central plateaus
- the overjet is reduced or reversed
What is a Class I molar relationship?
the maxillary mesiobuccal cusp and the mandibular buccal groove are in line
What is a Class II molar relationship?
mandibular molars moved backwards
- mandibular buccal groove behind the maxillary mesiobuccal cusp
What is a Class III molar relationship?
maxillary molars moved backwards
- mandibular buccal groove in front of the maxillary mesiobuccal cusp
What teeth should you check in a 9 year old patient?
‘When a child of 9 arrives, think 3s, 6s and 5s’
- Check for canines, condition of 6s, 5s commonly missing in hypodontia
What are the most commonly missing teeth?
2s, 5s and 8s
