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Craniofacial and Tooth Biology > 9. Tooth Eruption and Exfoliation > Flashcards

9. Tooth Eruption and Exfoliation Flashcards

1
Q

Dynamic replacement describes what?

A

the mixed dentition
- primary into permanent teeth

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2
Q

Teeth are displaced … and …

A
  • anteriorly
  • laterally
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3
Q

3 types of tooth movement

A
  • pre-eruptive
  • eruptive
  • post-eeruptive
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4
Q

Explain pre-eruptive tooth movement

A
  • movement of successional tooth germs
  • developing anterior permanent teeth move into position behind the roots of primary teeth
  • developing premolars move into position between roots of primary molars
  • lack of space causes occlusal surfaces of maxillary molar germs to face backwards - once maxilla grows, repositioning occurs
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5
Q

When does eruptive tooth movement start?

A

while the crown is still being formed and eruption begins

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6
Q

Explain eruptive tooth movement

A
  • requires remodelling of all periodontal tissue
  • final tooth position in jaw is determined by muscle and occlusal forces acting on erupted teeth
  • tooth eruption, emergence (through alveolar bone and gingiva - tooth partially erupted), clinical emergence
  • in primary teeth, there is root reabsorption (in addition to alveolar bone resorption) and exfoliation - shedding of primary teeth
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7
Q

Define ‘exfoliation’

A

shedding of primary teeth

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8
Q

What influences the pattern of resorption of the primary teeth?

A

the developing permanent teeth

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9
Q

Give the root resorption patterns

A
  • root resorption of primary incisors and canines occurs from lingual side, results in an intact pulp chamber at exfoliation
  • root resorption of primary molars occurs in occlusal direction, results in resorption of pulp chamber, coronal dentine and sometimes enamel
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10
Q

Stages of exfoliation of anterior primary teeth

A
  • permanent tooth germ moves into position
  • resorption begins
  • primary tooth is shed
  • permanent tooth emerges
  • root incomplete
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11
Q

Stages of exfoliation of primary molars

A
  • permanent tooth germ moves into position
  • resorption (almost complete)
  • primary tooth is shed
  • permanent tooth erupted and in occlusion
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12
Q

What happens in root resorption?

A

odontoclasts resorb dental hard tissues like root dentine

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13
Q

What happens in coronal dentine resorption?

A
  • monocytes migrate from pulp to dentine surface and fuse with other cells to form odontoclasts
  • begin to resorb dentine from pulp outwards
  • odontoblasts regenerate towards end of root resorption
  • resorption ceases before exfoliation occurs and cementum like tissue forms along coronal dentine
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14
Q

Explain PDL resorption

A
  • occurs rapidly associated with cell death
    -PDL fibroblasts undergo necrosis/apoptosis
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15
Q

Explain post-eruptive tooth movement

A
  • maintenance of erupted teeth in occlusion while jaw grows and compensates for tooth wear
    (like mesial and vertical drift, dento-alveolar compensation)
  • mechanisms is bone and PDL remodelling and compensatory formation of cellular cementum
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16
Q

Reasons for early primary teeth loss
How does this affect the permanent teeth?

A
  • due to caries or extraction
  • affects space distribution and symmetry
  • leads to accelerated eruption of permanent teeth
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17
Q

Reasons for prolonged retention of primary teeth

A
  • due to failure of successional tooth to resorb primary tooth
  • or ectopic position of successor - impacted canines are common
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18
Q

Effect of primary teeth retention on permanent teeth

A
  • lots of variation regarding exfoliation of primary teeth
  • check radiograph when asymmetry in loss of contralateral teeth
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19
Q

3 categories of abnormal tooth eruption

A
  • delayed
  • accelerated
  • impaction of teeth
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20
Q

Types of delayed eruption

A
  • congenital (3rd molars)
  • systemic (deficiencies)
  • local (eruption cysts)
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21
Q

What happens in accelerated eruption?

A
  • neonatal central incisors
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22
Q

Define ‘impaction of teeth’ in regards to eruption

A
  • eruption failure
  • caused by abnormal eruption pathway or lack of space
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23
Q

What is the role of successional teeth in exfoliation?

A
  • retained primary teeth are common
  • shedding is delayed if successional teeth are missing
  • exfoliation determined by the successional teeth coming through
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24
Q

If successional tooth is missing, does the primary tooth shed?

A

eventually

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25
Q

Explain supernumerary teeth
How does this impact eruption?

A
  • extra teeth (more than 32)
  • can be an isolated trait or as part of a clinical syndrome
  • normal teeth tend to be larger
  • can prevent eruption of other teeth
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26
Q

Supernumerary teeth is more common in
- primary or permanent dentition?
- males or females?

A
  • permanent
  • twice as common in males
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27
Q

Define ‘hypodontia’

A
  • absence of 1-6 teeth
  • excluding 3rd molars
28
Q

Define ‘oligodontia’

A

absence of more than 6 teeth

29
Q

Most commonly missing teeth in hypodontia
Which are most likely to be congenital?

A
  • 3rd molars
  • lower 2nd premolar
  • upper lateral incisor
    above are the congenital
  • upper premolars
  • lower central incisors
30
Q

Localised Incisor-Premolar Hypodontia in common in what nationality?

A

European ancestry

31
Q

Congenital absence of what teeth is rare?
How to confirm?

A
  • canines, 1st and 2nd molars
    -check evidence from clinical observation, a radiograph, clinical history from patient and patient records
32
Q

In what percentage of people are 3rd molars missing?

A

20-30%

33
Q

Hypodontia can be associated with …

A
  • reduced crown and root size
  • conical crown shape
  • enamel hypoplasia
  • molar taurodontism
  • delayed eruption
  • retention of primary teeth
  • impaction of maxillary canines
34
Q

What is taurodontism?

A

shortening of the space between roots in molars

35
Q

Explain dilaceration

A
  • abnormal angulation between crown and root of tooth
  • usually maxillary incisors
  • often due to trauma of primary predecussors (tooth fails to erupt)
  • trauma can cause cessation of root growth
  • root so stunted and doesn’t properly support tooth
36
Q

Which erupt first? Maxillary or mandibular teeth?

A

mandibular

37
Q

Anterior teeth or posterior teeth erupt first?

A

anterior

38
Q

Give 3 phases of tooth eruption

A
  • first is 6-1-2 at 6.8 to 8.5 years
  • second is 3-4-5-7 at 11-12 years (most variable)
  • third is 8s at 17-21
39
Q

Eruption dates of 1st and 2nd primary molars

A
  • 1.5 years
  • 2.5 years
40
Q

Eruption dates of 1st, 2nd and 3rd permanent molars

A
  • 6 yrs
  • 12 yrs
  • 18 yrs
41
Q

There is variability between cultures in individuals and populations in eruption. Give 2

A
  • some African populations erupts 3rd molars earlier than European, even though crown formation seems similar
  • South African populations initiate anterior teeth at same age as Northern Europe but crown completion is earlier
42
Q

4 important dates to look at in tooth formation

A
  • calcification
  • crown completion
  • root bifurcation for lower permanent molar roots
  • root coompletion
43
Q

Moores, Fanning and Hunt’s stages of tooth formation are below. What do they mean?
Ci
Cco
Coc
Cr1/2
Crc
Ri
A1/2
Ac

A
  • initiation
  • cusp coalescence
  • cusp outline complete
  • crown one half complete
  • crown complete
  • root initiation
  • apex 1/2 closed
  • apex closed
44
Q

What is the calcification date?

A
  • first radiographic appearance of crown
45
Q

Calcification dates for primary teeth

A

4-6 months in utero in womb
- front to back

46
Q

Calcification date for permanent first molars, incisors, canines

A
  • just before birth
  • 3-5 months, except upper lateral at a year
  • 6.5 months for lower, 9 months for upper
47
Q

Calcification date for permanent premolars, 2nd and 3rd molars

A
  • 1.85 to 2.65 yrs
  • 3 yrs
  • 8 years but unreliable
48
Q

When is the crown completion date as a rule of thumb?

A
  • usually little more than half of the time between first evidence of calcification and eruption
49
Q

Upper lateral incisors have a calcification date of …, eruption date of … and crown completion of …

A
  • 1 yr
  • 8.5 yrs
  • 4.5 yrs
50
Q

Lower 1st molars have a calcification date of …, eruption date of … and crown completed of …

A
  • just before birth
  • 6 yrs
  • 3 yrs
51
Q

How can we see crown completion on an X-ray?

A
  • denser enamel appears whiter than dentine
  • dentine extends lower than enamel - initiation of root formation
52
Q

Define ‘root birfurcation’

A
  • first evidence of calcification of bifurcation of lower permanent molar roots
53
Q

Root bifurcation date for
- lower 1st molar
- lower 2nd molar

A
  • 4.5 yrs
  • 8.5 yrs
54
Q

Root completion in primary teeth is … years after eruption

A

1-1.5

55
Q

Permanent teeth have root completion … to… after eruption

A
  • less than 2 years for lower incisors
  • to more than 3 years for 1st molars
56
Q

Define ‘tooth eruption’

A
  • process of tooth movement
  • from within alveolar bone upward
  • to reach functional occlusion
57
Q

Emergence of the crown is through what?

A
  • alveolar bone
  • gingiva
58
Q

Define ‘clinical emergence’

A
  • tooth is visible in oral cavity
59
Q

Mixed dentition begins at age … with appearance of … and ends at … age with appearance of …

A
  • 6
  • 1st perm molars
  • 11+
  • premolars
60
Q

Time from clinical emergence to occlusion

A
  • 3 months for incisors
  • up to 6 months for molars
61
Q

When does root resorption of primary teeth occur?

A
  • anterior teeth is a year from onset of resorption to exfoliation
  • molar teeth - 1.5 years
  • i.e the Es commense resorption at 9.5+ years, exfoliate at 11+
62
Q

What resorbs first? Mesial or distal roots?

A

distal

63
Q

Root resorption occurs earlier in girls or boys?

A

girls

64
Q

Give 2 examples of age determination from teeth

A
  • dental panoramic tomograph
  • age by tooth type graph
65
Q

How to do age determination from a dental panoramic tomograph?

A
  • find lower 6
  • if crown complete, over 3
  • bifurcation of root is around 4.5
  • if unerupted less than 6
  • if roots incomplete less than 9
  • confirm by looking at upper 6
  • find lower 7
  • if crown complete, then more than 6.5 yrs
  • root bifurcation calcifies at 8.5
  • unerupted means more than 12 ish
  • if root incomplete, around 15
  • confirm by looking at upper 7
  • look for evidence of calcification of 8 (around 8-10 years but crypt visible from 6)
  • look degree of eruption of incisors (some variation) lower 1 and 2 can erupt at same time
  • lower 1 6-7 yrs, lower 2 7-8 yrs, upper 1 erupts 7-8, upper 2 erupts 7.5-8.5 yrs
  • confirm by checking degree of development or eruption of 5s, 4s and 3s
66
Q

Why do dentists need to know eruption?

A
  • knowing the normal to recognise the abnormal (age/sequence/position)
  • estimate dental age (measure of growth) - number of erupted teeth indicates age

Craniofacial and Tooth Biology (25 decks)

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