Primary Tooth Morphology And Chronology Of Eruption Flashcards
List 4 early problems that can occur in children’s mouths
- Gingival cysts (Epstein’s pearls/Bohns nodules) - appear white
- Congenital epulis
- Natal or neonatal teeth
- Eruption cysts - appear blue
How is the primary dentition written using FDI notation?
Quadrants 5 6
7 8
Letters A B C D E used
When do teeth start to form?
During week 5 of intra-uterine life
When does hard tissue formation begin?
Week 13 IUL
Describe the development of the maxillary central incisor in chronological order: •hard tissue formation •crown complete • eruption •root complete
- Hard tissue formation. 13-16 weeks IUL
- Crown complete 1.5 months after birth
- Eruption 8-12 months
- Root complete 33 months
Describe the development of the maxillary second primary molar in chronological order
- Hard tissue formation - 16-23 weeks IUL
- Crown formation complete - 11 months after birth
- Eruption - 25-33 months
- Complete root formation - 47 months
List the tooth crowns that are calcified at birth
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
List some possible theories behind tooth eruption
- Cellular proliferation at apex of tooth
- Localised change in blood pressure/hydrostatic pressure
- Metabolic activity within the PDL
- Resorption of the overlying hard tissue
How does the dental follicle appear on a radiograph?
Dark halo around unerupted tooth
What process is considered essential to the process of tooth eruption?
Remodelling of bone and primary tooth tissue
What is the main function of the dental follicle?
Follicle is activated to initiate osteoclastic activity in the alveolar bone ahead of the tooth in order to clear a path for tooth eruption
What sequence does the primary dentition erupt in?
- Central incisor (A)
- Lateral incisor (B)
- First primary molar (D)
- Canine (C)
- Second primary molar (E)
ABDCE
(As a general rule, lowers erupt before uppers except the lateral incisors)
When does the lower central incisor erupt?
Give the FDI notation for these teeth
- 4-6 months
* 81 and 71
When does the lateral incisor erupt?
Give the FDI notation
- 7-16 months
* 52, 62, 72, 82
When do the 1st molars erupt?
Give the FDI notation
- 13-19 months
* 54,64,74,84
When do the canines erupt?
FDI notation
- 16-22 months
* 53,63,73,83
When do the second molars erupt?
- 15-33 months
* 55,65,75,85
How long does it normally take for all teeth of the same series to erupt?
Less than 3 months
At what age is the primary dentition complete?
2.5-3 years
Is it normal for children of 1 year to still have no erupted teeth?
Yes - there is huge variation in eruption dates
What are the main differences between the crowns of primary and permanent teeth?
- Primary incisors are smaller in both crown and root proportions
- Primary molars are wider mesiodistally than the permanent premolars which take their place
- Primary molars have more bulbous crowns
- Primary teeth usually whiter in colour
What is a distinguishing feature of the upper right 1st primary molar?
Prominent mesio buccal tubercle
What is an anatomically important feature on the upper right second primary molar?
Transverse ridge
- important to preserve if possible
What is the main distinguishing feature of the lower right second primary molar?
3 buccal cusps (like lower 1st permanent molar)
What are the main differences between the roots of primary and permanent teeth?
- Roots of primary teeth tend to be narrower when compared with their permanent counterparts
- 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
What are the main differences in primary and permanent tooth pulp?
how does this effect you clinically?
- Pulp chambers of the primary teeth are relatively large in proportion to the crowns that surround them
- 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
What is the main difference between root canals of primary and permanent teeth?
- Primary root canals tend to be ribbon shaped with multiple interconnecting and accessory canals
- clinically impossible to clean completely
What are the main differences in hard tissue between primary and permanent teeth?
- Enamel of primary teeth is relatively thin and has consistent depth
- The thickness of coronal dentine is much thinner than in permanent teeth
Why is spacing of the primary dentition desirable?
Reduces the likelyhood of overcrowding in the permanent dentition
What is meant by leeway space in the primary dentition?
•extra mesio distal space occupied by the primary molars which are wider than the premolars which will replace them
How big is the leeway space on the upper and lower arches?
Upper: 1.5mm per side
Lower: 2.5mm per side
In what age range does the mixed dentition stage occur?
6-11 years
- this varies
(Normally begins at age 6 - 1st permanent molar)
What is normally the final primary tooth to be exfoliated from the mouth?
Upper primary canine
In cases of overcrowding, what teeth are often excluded due to lack of space in the upper and lower arches?
Upper: canine
Lower: second premolar
What results in an increased A-P arch length in the permenant dentition
Proclined permanent incisors
What is a potential trauma risk to the permanent teeth which relates to the path of eruption?
Trauma risk to permanent teeth if primary incisors are displaced towards the developing central incisors which normally erupt palatally to the primary incisors
What causes transient spacing of the developing upper 1’s, referred to as the ‘ugly duckling stage’?
Close proximity of roots pushes teeth outwards
- problem is self correcting once the permanent dentition is established
How long does root formation take in the permanent dentition
3 years
