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Orthodontics > Orthodontic Extractions > Flashcards

Orthodontic Extractions Flashcards

1
Q

Describe 5 reasons to extract teeth for orthodontics

A
  1. Relieve crowding
  2. Reduce an increased overjet
  3. Correct centrelines
  4. Open space for missing teeth
  5. Correct anterior overbite
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2
Q

Describe increased overjet

A

Horizontal relationship between the upper and lower incisors, usually 2 - 4 mm

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3
Q

Describe 5 factors which influence the extraction decision

A
  1. Amount and site of crowding
  2. Size of overjet
  3. Caries
  4. Centre-lines
  5. Anchorage considerations
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4
Q

Describe how crowding is graded

A

Crowding = Total tooth size - Total arch length

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5
Q

What is anchorage?

A

Source of resistance to reaction from the active components

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6
Q

Describe why anchorage is important?

A
  • Anchorage gives something to pull or push against when moving teeth
  • Inadequate anchorage may prevent achieving desired treatment
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7
Q

Name 3 issues which inadequate anchorage can lead to

A
  1. Residual crowding
  2. Residual overjet
  3. Residual centreline discrepancy
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8
Q

Describe anchorage loss

A

Extraction space closes due to forward movement of the anchor teeth rather than those teeth that we wish to move

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9
Q

Name 4 ways to provide anchorage

A
  1. Other teeth (same arch or other arch using elastics)
  2. Baseplate on removable appliances
  3. Orthodontic mini-implants
  4. Extra-oral (headgear, facemask)
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10
Q

Describe the relationship between anchorage and root area

A
  • Anchorage value of tooth related to root surface
  • Anchorage unit reinforced by incorporating more teeth
  • Extraction of 1st rather than 2nd premolars improves anchorage balance
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11
Q

Name 2 ways to reduce anchorage demands

A
  1. Reducing number of teeth being moved

2. Limiting force from active components to optimum level for movement

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12
Q

Describe how elastics can help provide anchorage from teeth in opposing arch

A
  • Elastics connect upper and lower jaw
  • Forces resolved horizontally in one direction
  • Can get false projection of overjet loss if lower teeth move anteriorly
  • Rectangular archwires force lower teeth to move bodily
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13
Q

Describe how baseplate can help provide anchorage

A

Baseplate can increase anchorage by engaging the palatal vault

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14
Q

Describe how orthodontic mini-implants can help provide anchorage

A
  • Nickel titanium coil spring reinforces anchorage
  • Miniscrew only would have no anchorage loss
  • Do not want mesiobuccal aspect on root to impinge on screw
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15
Q

Describe how headgear provides anchorage

A
  • Engaged into upper first molar bands
  • Distalising molar into Class I
  • Combipull, high pull, low pull and cervical pull
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16
Q

What is the most common upper arch orthodontic extraction?

A

1st premolars (sometimes 2nd premolars)

17
Q

Describe the extractions of upper 1st premolars

A
  • Provide space anteriorly for overjet reduction
  • Provide space anteriorly for crowded incisors and canines
  • Most ideal for Class II Div 1 cases
18
Q

Describe 3 ways in which extraction of upper 1st premolars can affect a Class II Div 1 case

A
  1. Increased overjet
  2. Well aligned lower arch
  3. Proclined upper incisors
19
Q

Describe how extraction upper 1st premolars affects Class II Div 1 relationship

A
  • Extraction of upper 4s
  • Retract canines with buccal canine retractor
  • Reduce overjet by retracting incisors with Roberts retractor
20
Q

Describe how the extraction of upper 1st premolars may be used as an interceptive treatment

A
  • Buccally crowded upper canines
  • Extract upper 4s as canines erupt
  • Space created for canines to erupt into
  • May need space maintaining appliance
21
Q

Describe where upper 2nd premolars may be extracted

A
  • Mild to moderate anterior crowding
  • When overjet reduction is not required
  • Provide about 3mm per side as some space is closed from behind
22
Q

What is the most common lower arch orthodontic extraction?

A

2nd premolars (sometimes 1st premolars)

23
Q

Describe the extractions of lower 2nd premolars

A
  • Mild / moderate lower incisor crowding
  • Usually with fixed appliances
  • Extraction of choice
24
Q

Describe 3 situations where lower 1st premolar extractions may be carried out

A
  1. Severe lower incisor crowding
  2. Class III malocclusions
  3. Impacted lower 2nd premolars as interceptive procedure
25
Q

Describe why lower 1st premolars may be extracted in class III cases

A
  • Space is used to retrocline lower canines and incisors
  • Lower fixed appliance used
  • May use circular archwire lower and rectangular upper to allow tipping
26
Q

Describe why upper 2nd molars may be extracted for orthodontic purposes

A
  • Aid distalisation of first molars
  • Mild anterior crowding
  • Using an upper removable appliance and / or headgear
27
Q

Describe why lower 2nd molars may be extracted for orthodontic purposes

A

Prevent impaction of 3rd molars

28
Q

Describe why 1st molars may be extracted for orthodontic purposes

A
  • Rarely extractions of choice
  • Space difficult to use for treating crowding and overjet
  • May be a loss as result of caries
29
Q

Describe the early loss of 1st molars due to caries

A
  • Spontaneous space closure good at 8-9 years
  • Residual spaces if extracted later
  • Unopposed 6s may over-erupt
30
Q

Describe why incisors may be extracted for orthodontic purposes

A
  • Rarely extractions of choice
  • Upper lateral if other side absent or peg shaped
  • Lower extraction in adult patient with fixed appliance and crowding
31
Q

Describe why canines may be extracted for orthodontic purposes

A
  • Palatally ectopic upper canines
  • Incidence around 2%
  • Unwilling to wear appliances and poor position
32
Q

Describe why 3rd molars may be extracted for orthodontic purposes

A
  • Very weak association with lower incisor crowding

- Late lower incisor crowding alone not indication for extraction

33
Q

In one word, describe normal orthodontic extraction patterns

A

Symmetrical

34
Q

Describe 5 situations when extractions patterns may be asymmetrical

A
  1. Centreline correction
  2. Supernumeraries
  3. Caries and heavily restored teeth
  4. More crowding in one quadrant
  5. Anchorage situation more challenging on one side
35
Q

Name 3 alternatives to extraction to create space

A
  1. Arch expansion (stable in upper / unstable in lower)
  2. Distalisation of teeth
  3. Enamel reduction (interproximal reduction)
36
Q

Name 2 ways to distalise teeth to provide space in an arch

A
  1. Headgear in upper arch

2. Orthodontic mini-implants

37
Q

Name a risk of interproximal reduction

A

Sensitivity

Orthodontics (11 decks)

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