Extractions And Anchorage Flashcards
Why extract teeth?
To create space To relieve crowding Reduce an increased overjet Correct centrelines Open space for missing teeth Correct AOB
What factors influence the extractions decision?
Amount and site of crowding Size of overjet Caries Centrelines Anchorage considerations
What is anchorage?
Anchorage is the source of resistance to the reaction from the active components
Why is anchorage important?
Gives something to pull or push against when moving teeth
Inadequate anchorage may prevent us achieving the desired treatment result leading to- residual crowding, residual overjet, residual centreline discrepancy
What might anchorage loss result in?
Residual overjet
Residual crowding
Inadequate centreline correction
How do we provide anchorage?
Other teeth- in the same arch, in the opposing arch
Baseplate on removable appliances
Orthodontic mini-implants
Extra-oral- conventional headgear, face mask/reverse pull headgear
Class 2 elastics
What is the correlation in anchorage and root area?
The anchorage value of a tooth is closely related to the surface area of its root surface
The anchorage unit can be reinforced by incorporating more teeth to increase the total root surface area
How can the demands on the anchorage be reduced?
Reducing the number of teeth being moved
Limiting the force from the active components to the optimum level for tooth movement (25-50g)
When retracting canines, extracting which tooth improves the anchorage?
Extraction of the 1st rather than 2nd premolar improves the anchorage
What are the most common upper arch extractions?
Upper 1st premolars
Sometimes upper 2nd premolars
What does the extraction of upper 1st premolars provide space anteriorly for?
Overjet reduction
Crowded incisors and canines
Provides 7mm space per side
Most ideal for class II Div 1 cases
Why are upper 2nd premolars sometimes extracted?
To relieve mild to moderate anterior crowding
When overjet reduction is not required
They provide about 3mm per side as some spaced is closed from behind (anchorage loss)
What are the most common lower arch extractions?
Lower 2nd premolars
Sometimes lower 1st premolars
Why are lower 2nd premolars extracted?
To relieve mild to moderate lower incisor crowding
Why are lower 1st premolars sometimes extracted?
Severe lower incisor crowding
Class II malocclusions
Impacted lower 2nd premolars as an interceptive procedure
Poor prognosis
Why are upper 2nd molars sometimes extracted?
To aid distalisation of 1st molars
For mild anterior crowding
When using an upper removable appliance and/or headgear
Why are lower 2nd molars sometimes extracted?
To prevent impaction of 3rd molars
Why do 1st molars sometimes have to extracted?
May be lost as a result of caries
But space difficult to use for treating anterior crowding and/or overjet
Spontaneous space closure good at age 8-9 years
Residual space if extracted later- upper 7s close better than lowers, lower 7s tend to tip mesially
Unopposed upper 6s may overerupt
When are incisors extracted for orthodontic purposes?
Rarely extraction of choice
Upper laterals if other side absent or peg-shaped
Sometimes lower incisor extraction in adult patients with fixed appliances and lower incisor crowding
When are canines extracted for orthodontic treatment?
Palatally ectopic upper canines (incidence of 2%)
Buccal lay crowded canines
When are lower 3rd molars extracted?
Surgical removal of impacted 3rd molars should be limited to patients with evidence of pathology
Very weak association with lower incisor crowding
Late lower incisor crowding alone is not an indication for lower 3rd molar extraction
What are common extraction patterns?
Extraction patterns are usually symmetrical But they are sometimes asymmetrical for: -centreline correction -more space needed on one side -supernumeraries -caries/heavily restored tooth -more crowding in one quadrant -anchorage situation more challenging on one side
What are some alternatives to extraction used to create space?
Arch expansion
Distalisation of teeth
Enamel reduction
