Development of the Occlusion Flashcards
Name 2 reasons a knowledge of development of dentition is important
- Prediction of future need for treatment
2. Early diagnosis may enable interceptive treatment
Name 3 key stages of development of the occlusion
- Primary dentition
- Mixed dentition
- Permanent dentition
What is mixed dentition?
Transition period between primary and permanent dentitio
What are 3 stages of tooth development?
- Bud
- Cap
- Bell
Name 3 key points of primary dentition
- Eruption times vary by 6 months from expected ages
- Calcification begins 4-6 months in utero
- Root formation complete 12-18 months after eruption
Describe the sequence of eruption of primary teeth
a - b - d - c - e
What are 4 notable points with regards to the sequence of eruption of primary teeth?
- b-c-d earlier in maxilla than mandible
- Girls erupt faster than boys
- 6 month variation is normal
- No significant left and right differences
What are the eruption dates of primary central incisors in maxilla and mandible?
10 months - 8 months
What are the eruption dates of primary lateral incisors in maxilla and mandible?
11 months - 13 months
What are the eruption dates of primary cuspids in maxilla and mandible?
19 months - 20 months
What are the eruption dates of primary 1st molars in maxilla and mandible?
16 months - 16 months
What are the eruption dates of primary 2nd molars in maxilla and mandible?
29 months - 27 months
Describe 2 changes which may occur between 2.5 and 5.5 years
- Increase in spacing due to increase in arch width
2. Occlusal attrition can lead to edge-to-edge incisal relationship
Name 6 things to check for when examining a primary dentition
- Spacing
- Crossbites
- Overjet
- Overbite
- Early loss
- Incisor trauma
Why is spacing important to check for in primary dentition?
No spacing indicates permanent dentition likely to be crowded so interceptive orthodontic treatment may be required
Why are overjets and overbites important to check for in primary dentition?
May be due to skeletal defect and important to ensure these patients are under review
Name 2 causes of an open bite
- Thumb sucking
2. Pacifier sucking
Why is incisor trauma important to check for in primary dentition?
It can lead to permanent dentition being dilacerated where the crown is displaced but root is not
Describe the arch length prediction from alignment of primary teeth and the likely permanent outcome
Primary crowding - Almost certain extractions
No primary spacing - Possible extractions
Fair spacing - Mild to moderate crowding
Good spacing - No or mild crowding
Excess spacing - No crowding / Excess spacing
What 2 permanent teeth are most likely to erupt first?
- 1st molars
2. Lower central incisors
What 2 permanent teeth are most likely to erupt first?
- 1st molars
2. Lower central incisors
What 2 permanent teeth are most likely to erupt first?
- 1st molars
2. Lower central incisors
Name 6 things to check for when examining a mixed dentition
- Ankylosis
- Carious first molars
- Early loss of deciduous molars
- Ectopic eruption of maxillary canines
- Eruption failures
- Missing / extra teeth
What is ankylosis?
- Fusion of alveolar bone and cementum so tooth cannot erupt an become submerged compared to other teeth
- First primary molar most commonly affected and most common in the mandible
Why must a clinician be wary of a carious first molar in the mixed dentition?
- Extraction is a very last resort
- Space closure is not particularly good but better in maxilla
- Extraction of 6s doubles treatment time and halves prognosis
Describe 2 types of ectopic eruption of 1st molars
Reversible - 66% of the time where tooth self corrects
Irreversible - 33% of the time where tooth does not correct and usually involved referral
Describe the epidemiology of ectopic eruption of first molars
- Genetic component
- More common in maxilla
- More common in males
- Increased incidence in patients with cleft lip and palate
Name 4 teeth most commonly affected by hypodontia, excluding 3rd molars
- Mandibular 2nd premolar
- Maxillary lateral incisor
- Maxillary 2nd premolar
- Mandibular central incisors
What is the rule when considering failure of eruption of a permanent incisor?
6 month rule - 6 months later than contralateral tooth
Name 2 common reasons a permanent incisor would fail to erupt?
- Supernumerary tooth
2. Dilaceration
Where are supernumerary teeth most often found?
Maxillary incisor region as mesiodens
Name 4 types of supernumerary teeth
- Supplemental
- Conical
- Tuberculate
- Odontome
What is the most common type of supernumerary tooth?
Conical (small peg shaped tooth)
Name the eruption date of the upper 1s
7-8 years
Name the eruption date of the upper 2s
8-9 years
Name the eruption date of the upper 3s
11-12 years
Name the eruption date of the upper 4s
10-11 years
Name the eruption date of the upper 5s
10-12 years
Name the eruption date of the upper 6s
6-7 years
Name the eruption date of the upper 7s
12-13 years
Name the eruption date of the upper 8s
17-21 years
Name the sequence of eruption of maxillary teeth
6 - 1 - 2 - 4 - 5 - 3 - 7 - 8
Name the eruption date of the lower 1s
6-7 years
Name the eruption date of the lower 2s
7-8 years
Name the eruption date of the lower 3s
9-10 years
Name the eruption date of the lower 4s
10-12 years
Name the eruption date of the lower 5s
11-13 years
Name the eruption date of the lower 6s
6-7 years
Name the eruption date of the lower 7s
11-13 years
Name the eruption date of the lower 8s
17-12 years
Describe the eruption sequence of mandibular permanent dentition
6 / 1 - 2 - 3 - 4 - 5 / 7 - 8
Describe 3 features of the dental arch development
- Length
- Width
- Height
Describe how the arch width changes from mixed to permanent dentition
- Increases slightly on eruption of permanent incisors due to jaw growth
- Increase in length to accommodate additional permanent molars
- From 1st molar to central incisor arch length decreases after primary molars are shed
Describe the proclination of permanent incisors compared to primary incisors
More proclined (by 10-15 degrees)
Describe how arch width is affected during eruption of permanent dentition
- Increases on eruption of permanent incisors
- Once permanent incisors fully erupt there is no further transverse growth of the arches
Describe juvenile occlusal equilibration
After teeth have erupted into occlusion, they must continue to erupt at slower pace to match vertical skeletal growth
Describe adult occlusal equilibration
Once the adolescent growth spurt has passed teeth must continue to erupt at a very slow rate to compensate for wear and continued vertical skeletal growth
What is the clinical significance of the growth of the arch?
Dimensions of the dental arches are established early and do not change much after lateral incisors fully erupt so it is unrealistic to expect crowding to be relieved by growth of the arches
