8 - Interceptive orthodontics

Question 1

Describe the oral cavity at birth.

Answer 1

• gum pads
• upper is rounded, lower is more U shaped
• appears class III
• AOB

Question 2

What are natal/neonatal teeth?

Answer 2

• abnormal dental development
• lower incisors are most common
• extraction is only indicated if mobile and are at risk of inhalation or causing difficulty breastfeeding

Question 3

Describe the process of eruption.

Answer 3

• pre-eruptive phase (crown formation)
• eruptive phase (beginning of root formation to tooth reaching occlusal plane)
• post-eruptive phase (tooth movement as root forms)

Question 4

Describe the pre-eruptive phase.

Answer 4

• developing crowns move within the jaws as response to jaws growing
• crowns are contained within bony crypts

Question 5

Describe the eruptive phase.

Answer 5

• split into intra- and extra-osseous
• relative position of primary and permanent teeth change as jaws grow, primary roots are resorbed and neighbouring crowns move

Question 6

Describe the intra-osseous eruptive phase.

Answer 6

• begins with proliferation of epithelial root sheath
• development of dentine and pulp
• movement of developing tooth occurs slowly over months
• reduced enamel epithelial fuses with oral epithelium

Question 7

Describe the extra-osseous eruptive phase.

Answer 7

• quick penetration of crown through oral epithelial layers (1-2 weeks)
• crown continues to erupt to occlusal plane
• environmental factors affect tooth final position (eg lips, tongue)

Question 8

What is the Gubernacular cord?

Answer 8

Fibres that form from the dental follicle to guide the tooth to erupt into the oral cavity

Question 9

What causes teeth to erupt?

Answer 9

• root formation
• remodelling of alveolar bone
• development of PDL

Question 10

What controls tooth eruption?

Answer 10

• dental follicle plays role in modulating cellular activity
• signalling cascade of cytokines (IL1, CSF1, RANKL/OPG)

Question 11

Describe the role of the dental follicle.

Answer 11

• initiates resorption of bone overlying tooth
• facilitates connective tissue degradation and creates eruption pathway
• promotes bone remodelling at the base of the tooth
• provides traction within PDL
• cells contribute to root formation and cementum

Question 12

Where do the permanent incisors develop?

Answer 12

Palatal/lingual to primary teeth

Question 13

Where is space gained for permanent incisors?

Answer 13

• increase in inter-canine width though lateral growth of jaws
• incisors erupt more proclined
• leeway space

Question 14

What is the leeway space in the upper?

Answer 14

1.5mm

Question 15

What is the leeway space in the lower?

Answer 15

2.5mm

Question 16

How do you manage an impacted 6?

Answer 16

• if younger than 7, wait 6 months to self correct
• orthodontic separator to disengage
• distalise 6
• XLA E
• distal disking of E

Question 17

What are causes of unerupted centrals?

Answer 17

• supernumeraries
• trauma (dilaceration)
• other pathology

Question 18

How do you manage supernumeraries preventing eruption of centrals?

Answer 18

• XLA of primaries and supernumeraries
• maintain or create space
• monitor for 12 months if younger than 9
• if fails to erupt or patient older than 9, expose and bond gold chain for orthodontic traction

Question 19

What is the effect of early loss of primary teeth?

Answer 19

Localised crowding

Question 20

How do you manage early loss of As?

Answer 20

No balancing or compensating extractions

Question 21

How do you manage early loss of Bs?

Answer 21

No balancing or compensating extractions

Question 22

How do you manage early loss of Cs?

Answer 22

Balancing extraction

Question 23

How do you manage early loss of Ds?

Answer 23

• can cause small CL shift
• balance if under GA

Question 24

How do you manage early loss of Es?

Answer 24

Consider space maintainer

Question 25

What are the different types of space maintainer?

Answer 25

• removable passive URA
• fixed palatal and lingual arches with band and loop

Question 26

When should early XLA of 6s occur?

Answer 26

• 7s calcification of bifurcation occurring
• 8s are present
• moderate crowing in lower
• mild-moderate crowding in upper

Question 27

How should you manage early loss of 6s?

Answer 27

Class I
- if XLA of lower, compensate
- if XLA of upper, do not compensate
- balancing not required

Question 28

What is the IOTN of a displacing unilateral cross bite?

Answer 28

4c

Question 29

What should be assessed with an anterior cross bite?

Answer 29

• displacement discrepancies
• mobility of lower incisor (jiggling forces)
• tooth wear of lingual or labial surfaces
• gingival recession

Question 30

What active component can be used to correct an anterior crossbite?

Answer 30

Z-spring with posterior bite planes to prop bite open for tooth to move

Question 31

How successful are crossbite corrections?

Answer 31

Anterior is more successful that posterior due to lower incisors acting as a retainer to the upper

Question 32

Why do you need to treat digit/dummy habits early?

Answer 32

• prevent effect on transverse and vertical skeletal development
• maximise potential for spontaneous correction of AOB whilst there is eruptive potential for incisors due to root formation not being complete

Question 33

How do you stop a digit habit?

Answer 33

• positive reinforcement
• bitter nail polish
• gloves on hands, Elastoplast
• habit breaker device (fixed or URA)

Question 34

What components can be used as deterrents?

Answer 34

• single goal post (URA - can be incorporated with an expansion screw)
• tongue rake (fixed)