Orthodontic Extractions Flashcards
Describe 5 reasons to extract teeth for orthodontics
- Relieve crowding
- Reduce an increased overjet
- Correct centrelines
- Open space for missing teeth
- Correct anterior overbite
Describe increased overjet
Horizontal relationship between the upper and lower incisors, usually 2 - 4 mm
Describe 5 factors which influence the extraction decision
- Amount and site of crowding
- Size of overjet
- Caries
- Centre-lines
- Anchorage considerations
Describe how crowding is graded
Crowding = Total tooth size - Total arch length
What is anchorage?
Source of resistance to reaction from the active components
Describe why anchorage is important?
- Anchorage gives something to pull or push against when moving teeth
- Inadequate anchorage may prevent achieving desired treatment
Name 3 issues which inadequate anchorage can lead to
- Residual crowding
- Residual overjet
- Residual centreline discrepancy
Describe anchorage loss
Extraction space closes due to forward movement of the anchor teeth rather than those teeth that we wish to move
Name 4 ways to provide anchorage
- Other teeth (same arch or other arch using elastics)
- Baseplate on removable appliances
- Orthodontic mini-implants
- Extra-oral (headgear, facemask)
Describe the relationship between anchorage and root area
- 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
Name 2 ways to reduce anchorage demands
- Reducing number of teeth being moved
2. Limiting force from active components to optimum level for movement
Describe how elastics can help provide anchorage from teeth in opposing arch
- 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
Describe how baseplate can help provide anchorage
Baseplate can increase anchorage by engaging the palatal vault
Describe how orthodontic mini-implants can help provide anchorage
- Nickel titanium coil spring reinforces anchorage
- Miniscrew only would have no anchorage loss
- Do not want mesiobuccal aspect on root to impinge on screw
Describe how headgear provides anchorage
- Engaged into upper first molar bands
- Distalising molar into Class I
- Combipull, high pull, low pull and cervical pull
What is the most common upper arch orthodontic extraction?
1st premolars (sometimes 2nd premolars)
Describe the extractions of upper 1st premolars
- Provide space anteriorly for overjet reduction
- Provide space anteriorly for crowded incisors and canines
- Most ideal for Class II Div 1 cases
Describe 3 ways in which extraction of upper 1st premolars can affect a Class II Div 1 case
- Increased overjet
- Well aligned lower arch
- Proclined upper incisors
Describe how extraction upper 1st premolars affects Class II Div 1 relationship
- Extraction of upper 4s
- Retract canines with buccal canine retractor
- Reduce overjet by retracting incisors with Roberts retractor
Describe how the extraction of upper 1st premolars may be used as an interceptive treatment
- Buccally crowded upper canines
- Extract upper 4s as canines erupt
- Space created for canines to erupt into
- May need space maintaining appliance
Describe where upper 2nd premolars may be extracted
- Mild to moderate anterior crowding
- When overjet reduction is not required
- Provide about 3mm per side as some space is closed from behind
What is the most common lower arch orthodontic extraction?
2nd premolars (sometimes 1st premolars)
Describe the extractions of lower 2nd premolars
- Mild / moderate lower incisor crowding
- Usually with fixed appliances
- Extraction of choice
Describe 3 situations where lower 1st premolar extractions may be carried out
- Severe lower incisor crowding
- Class III malocclusions
- Impacted lower 2nd premolars as interceptive procedure
Describe why lower 1st premolars may be extracted in class III cases
- Space is used to retrocline lower canines and incisors
- Lower fixed appliance used
- May use circular archwire lower and rectangular upper to allow tipping
Describe why upper 2nd molars may be extracted for orthodontic purposes
- Aid distalisation of first molars
- Mild anterior crowding
- Using an upper removable appliance and / or headgear
Describe why lower 2nd molars may be extracted for orthodontic purposes
Prevent impaction of 3rd molars
Describe why 1st molars may be extracted for orthodontic purposes
- Rarely extractions of choice
- Space difficult to use for treating crowding and overjet
- May be a loss as result of caries
Describe the early loss of 1st molars due to caries
- Spontaneous space closure good at 8-9 years
- Residual spaces if extracted later
- Unopposed 6s may over-erupt
Describe why incisors may be extracted for orthodontic purposes
- Rarely extractions of choice
- Upper lateral if other side absent or peg shaped
- Lower extraction in adult patient with fixed appliance and crowding
Describe why canines may be extracted for orthodontic purposes
- Palatally ectopic upper canines
- Incidence around 2%
- Unwilling to wear appliances and poor position
Describe why 3rd molars may be extracted for orthodontic purposes
- Very weak association with lower incisor crowding
- Late lower incisor crowding alone not indication for extraction
In one word, describe normal orthodontic extraction patterns
Symmetrical
Describe 5 situations when extractions patterns may be asymmetrical
- Centreline correction
- Supernumeraries
- Caries and heavily restored teeth
- More crowding in one quadrant
- Anchorage situation more challenging on one side
Name 3 alternatives to extraction to create space
- Arch expansion (stable in upper / unstable in lower)
- Distalisation of teeth
- Enamel reduction (interproximal reduction)
Name 2 ways to distalise teeth to provide space in an arch
- Headgear in upper arch
2. Orthodontic mini-implants
Name a risk of interproximal reduction
Sensitivity
