Stability and Retention Flashcards
What are the pre-treatment risk factors of relapse post ortho tx?
Median diastema
Spacing (esp. in adults)
Palatal canines
Class II div II
Grossly incompetent lips
Forward tongue posture
Anterior open bite
Periodontal disease
Slipped contacts/Rotations
How should we use the concept of equilibrium when planning and finishing ortho tx?
Unless a new position of stability is found the result will not be stable
So teeth need to be in equilibrium with soft tissues
What are the risk factors of relapse created during ortho tx?
Expansion
Incisor advancement
Incisor retraction
Extraction spaces (adults)
How can facial growth affect ortho tx stability?
If intercuspation of the teeth is poor or dentoalveolar compensation is at its limit, occlusal changes can occur
(e.g. class III, skeletal open-bite)
What is Dentoalveolar adaptation?
Dentoalveolar adaptation tends to maintain occlusal relationships even when skeletal relationships change with growth
Relapse or lack of stability is the tendency for change in what ways?
Tooth position or Arch relationship in relation to where they finished after tx
What are the aims of retention in ortho?
1) Allow periodontal & gingival reorganisation
2) Minimise changes from growth
3) Permit neurovascular adaptation to corrected tooth positioning
4) Maintain unstable tooth positions (if such positions required for compromise or aesthetics)
Comment on supporting tissues in stability of ortho tx
When teeth are moved by orthodontic appliances, the recently deposited bone is particularly susceptible to resorption.
Therefore, must retain most tooth movements until supporting tissues have adapted fully
The supporting bone and principal fibres of the periodontal ligament take approximately 6 months, but the supra-alveolar connective tissue takes much longer ( 1 year).
What is stability of a posterior crossbite correction by use of upper arch expansion reliant on?
Stability of posterior crossbite correction by upper arch expansion is reliant on good intercuspation of teeth
Does this patient have favourable or unfavourable soft tissues for teeth stability?
Unfavourable as patient has short upper lip which means upper incisor are not under lower lip control
Adult upper lip length:
Females - 20-22mm
Males - 22-24mm
How are teeth in malocclusion pre ortho tx considered stable?
A malocclusion before any orthodontic treatment is in a position of balance (and therefore stability) partly determined by soft tissues e.g. lips and tongue
Define retention in regards to ortho
The holding of teeth following orthodontic treatment in the treated position for the period necessary for the maintenance of the result
What are the different types of retainer for ortho tx?
- Vacuum formed/ “Essix” retainer (Removable)
- Hawley retainer (Removable)
- Fixed/bonded retainer (Fixed)
What soft tissue controls the upper incisors?
The lower lip
What is the difference between relapse and lack of stability?
Relapse - Teeth have moved from A to B during ortho. They then move back to A after tx
Lack of Stability - Teeth have moved from A to B during ortho. They then move back to C after tx
Why does this patient have unfavourable soft tissues?
Incompetent lip seal
Meaning he upper central incisors are not in control by the lips therfore there those teeth are not stable
What is this?
Hawley retainer (removable)
How can correction of an anterior crossbite remain stable?
Correction of anterior crossbites is only stable if a positive overbite is present
In the picture see how the lower teeth are kept in position by upper incisors in an overbite position
