Clinical Development of the Dentition

Question 1

What is orthodontics?

Answer 1

Orthodontics is that branch of dentistry concerned with facial growth, with development of the dentition and occlusion, and with the diagnosis, interception and treatment of occlusal anomalies.

Question 2

What are the stages of development (of the dentition)?

Answer 2

Newborn, primary (deciduous) dentition, mixed dentition, permanent dentition

Question 3

Describe newborn “dentition”

Answer 3

Gum pads, upper rounded, lower U shaped
Anterior open bite
Often appear very skeletal class 2

Question 4

Describe skeletal class I (antero/posterior relationship)

Answer 4

Mandible is 2-3mm posterior to the maxilla

Question 5

Describe skeletal class II (antero-posterior relationship)

Answer 5

Mandible is retruded relative to the maxilla

Question 6

Describe skeletal class III (antero-posterior relationship)

Answer 6

Mandible is protruded relative to the maxilla

Question 7

What is a natal tooth

Answer 7

A tooth present at birth. Rare. Needs to be removed

Question 8

What is cleft lip and palate?

Answer 8

Congenital defect that has a profound impact on patient’s dental development. Structures that form the upper lip and palate fail to fuse. Require a lot of treatment, early intervention carried out throughout stages of life. Surgery and orthodontics required.

Question 9

When do primary teeth erupt?

Answer 9

6 months - 3 years

Question 10

Which primary teeth erupt first?

Answer 10

Lowers erupt before uppers

a-b-c-d-e

Question 11

How does the primary dentition differ from permanent dentition?

Answer 11

Incisors are more upright than permanent dentition
Spaced
Often marked wear towards the end

Question 12

Why is it best to having spacing in primary dentition?

Answer 12

To prevent crowding when permanent dentition erupt

Question 13

What percentage of cases will show crowding with no spacing in primary dentition?

Answer 13

66% crowding

Question 14

What percentage of cases will show crowding with <3mm spacing?

Answer 14

50% crowding

Question 15

What percentage of cases will show crowding with 3-6mm spacing?

Answer 15

20% crowding

Question 16

What percentage of cases will show crowding with >6mm spacing?

Answer 16

No crowding

Question 17

Describe mixed dentition

Answer 17

Mixture of primary and permanent teeth
Age 6-13 approx.
Incisors and first molars erupt at age 6-8.5
Canines, premolars and second molars erupt at 10-12.5

Question 18

Which teeth generally erupt at age 6?

Answer 18

Upper and lower 6s

Lower 1s

Question 19

Which teeth generally erupt at age 7?

Answer 19

Upper 1s

Lower 2s

Question 20

Which teeth generally erupt at age 8?

Answer 20

Upper 2s

Question 21

Which teeth generally erupt at age 11?

Answer 21

Lower 3s

Upper and lower 4s

Question 22

Which teeth generally erupt at age 12?

Answer 22

Upper 3s
Upper and lower 5s
Upper and lower 7s

Question 23

How are permanent incisors accommodated?

Answer 23

1. Spacing of the deciduous dentition
2. Increase in inter-canine width: 3.5mm in the maxilla, 3.0mm in the mandible
3. Path of erupt is more proclined - bigger arc of circle - increase in AP arch

Question 24

Which incisors erupt first?

Answer 24

Centrals before laterals

Lowers before uppers

Question 25

What are supernumerary teeth?

Answer 25

Extra teeth that can block permanent teeth from erupting. Need to be removed

Question 26

Where are supernumerary teeth most common?

Answer 26

In upper incisor region, can impeded eruption of permanent incisors

Question 27

What leads to an increase in A-P arch length?

Answer 27

Proclined permanent incisors | Primary incisors are more upright

Question 28

Define "microdontia"

Answer 28

Small permanent teeth - can build them up with composite, porcelain veneer, etc

Question 29

Define "macrodontia"

Answer 29

Teeth that are too big. Can be difficult to reduce size without invading the pulp chamber. May need to extract tooth and replace with a prosthetic one

Question 30

What is increased overjet?

Answer 30

Upper teeth sticking out a bit | Increases risk of trauma to the upper teeth

Question 31

What is posterior/buccal cross bite?

Answer 31

Uppers and lowers not aligned in transverse axis

Question 32

What is the "Leeway" space?

Answer 32

Difference in size between e, d, c and 3, 4, 5 Maxilla = 1.5mm Mandible = 2.5mm

Question 33

What is dental alveolar disproportion?

Answer 33

Difference in size of teeth and space available to accommodate them in the jaw

Question 34

What is transposition?

Answer 34

Where 2 permanent teeth get swapped over. Usually involves the upper canine.

Question 35

Why is the upper canine usually involved in transposition?

Answer 35

The upper canine takes longer to erupt as it develops high up. More scope for it to lose its way and get swapped over with another tooth germ on the way down.

Question 36

What are the features of an ideal static occlusion?

Answer 36

1. Incisors slightly proclined, with the lower incisal edge in contact with the cingulum plateau of the maxillary teeth. Overjet and overbite 2-4mm on average. 2. The mesiobuccal cusp of the maxillary permanent molar occludes with the buccal groove of the mandibular first molar. 3. Long axis of the teeth have a slight mesial inclination EXCEPT the lower incisors 4. Tight approximal contacts with no rotations 5. Flat occlusal plane or slight curve of Spee 6. The crowns of the canines back to the molars have a lingual inclination

Question 37

Describe Class I (incisor classification)

Answer 37

The lower incisor edges occlude with or lie immediately below the cingulum plateau of the upper central incisors

Question 38

Describe Class II Div 1 (incisor classification)

Answer 38

The lower incisal edges lie posterior to the cingulum plateau of the upper incisors The upper central incisors are proclined or of average inclination, the overjet is increased

Question 39

Describe Class II Div 2 (incisor classification)

Answer 39

The lower incisal edges lie posterior to the cingulum plateau of the upper incisors The upper central incisors are retroclined, the overjet is usually minimal but can be increased

Question 40

Describe Class III

Answer 40

The lower incisal edges lie anterior to the cingulum plateau of the upper incisors The overjet is reduced or reversed

Question 41

Define overjet

Answer 41

Distance between the upper and lower incisors in the horizontal plane (normal overjet is 2-4mm)

Question 42

Define overbite

Answer 42

Vertical overlap of the upper and lower incisors when viewed anteriorly One third to one half coverage of the lower incisors is normal

Question 43

Define crowding

Answer 43

When there is insufficient space to accommodate the teeth in perfect alignment

Question 44

Define hypodontia

Answer 44

Congenital absence of one or more teeth

Question 45

Define leeway space

Answer 45

Difference in mesio-distal diameter between c, d, e and 3, 4, 5

Question 46

Define reverse overjet

Answer 46

The lower incisors lie anterior to the upper incisors

Question 47

Define malocclusion

Answer 47

Variation from the ideal occlusion which has dental health and/or psychosocial implications for the individual

Question 48

Define ideal occlusion

Answer 48

Anatomically perfect arrangement teeth

Question 49

Define normal occlusion

Answer 49

Acceptable variation from the ideal occlusion

Question 50

Define buccal cross bite

Answer 50

The buccal cusps of the lower premolars and/or molars occlude buccally to the buccal cusps of the upper premolars and/or molars

Question 51

What are natal teeth?

Answer 51

A tooth which is present at birth or erupts soon after

Question 52

Define transposition

Answer 52

The interchange in position between 2 teeth