Retention Flashcards
What is retention?
Holding of teeth following orthodontic treatment in treated position for a period of time necessary for maintenance of the result
Why do we need to retain?
Widening of the periodontal ligament
Disruption of the collagen fibres
Takes time to reorganise and reset the periodontal ligament
How long does it take periodontal ligament fibres to reorganise after orthodontic treatment?
3-4 months
How long does it take collagen fibres to reorganise after orthodontic treatment?
4-6 months
How long does it take for elastic supracrestal fibres to reorganise after orthodontic treatment?
1 year
How long should we retain?
Standard retention protocol-
- 0-3 months full time
- 9-12 months part time
- lifetime wear to maintain occlusion achieved at deboned/titrate retention
What are the ideal properties of a retainer?
Keep each tooth in its new position Should be strong enough Good aesthetics Facilitate plaque control Allow settling to occur Be removable
What cases don’t require retention?
Correction of anterior crossbite if adequate overbite at end of treatment
Correction of posterior crossbites if adequate positive contact and no excessive tipping
Interceptive orthodontics
What are the types of removable retainers?
Hawley Vacuum formed Wraparound Barrer-type Activators
What are the types of fixed/permanent retainers?
Coaxial wire (round) Coaxial wire (rectangular) Thick SS wire bounded to canines only
What are in the indications for a removable Hawley retainer?
Historical To carry Pontic teeth (hypodontia cases) To allow settling To maintain transverse dimensions To carry a biteplanes Can allow for tooth eruption
What are the indications for vacuum formed retainers?
Default choice for most orthodontic retention
To retain all types of irregularity
It’s suitable if there’s concerns
As an adjunct to a fixed retainer
What is the protocol for VFRs?
1-3 months full time wear
9-12 months part time wear (every night)
After 12 months, continue with regular night time wear on a indefinite basis
Replace if problems
What’s the process for providing VFRs?
Debond as required (removing all composite)
Record an impression in the clinic and write a prescription
Fabrication in the lab
Fit in the clinic (usually the same day)
What is the fabrication process of VFRs?
Impression/lab prescription
Cast model
Name model
Block out any undercuts as appropriate
Turn on heating element of vacuum forming machine
Select blank- copolyester resin and place jig on machine
Heat the blank until it drops by approx 10mm/turn on vacuum/drop jig with blank into model
Allow to cool
Trim blank using bench-top trimmer and cutting disc 2-3mm past gingival margin/leave more palatally and lingually
Tidy flash from margins using stone
What is the clinical placement of VFRs?
Fit retainer
Trim at chair side as appropriate
Demonstrate removal/re-insertion to patient
Ask patient to remove/re-insert
Verbal/written instruction in presence of patient as necessary
Arrange review, normally 6-12 weeks
What is the protocol for fixed retainers?
Patient generally provided with removable retainer also
Fixed retainer often placed at the time of debond
Advised lifetime wear/care/cleaning
Requires regular checkups with GDP
Immediate repair required if debonds
Requires excellent OH
What are the indications for fixed retainers?
Median diastema Generalised spacing Adults Cleft patients Missing lateral/centrals Mandibular incisor extraction cases Severe rotations
What are the contraindications for fixed retainers?
Poor plaque control
Occlusion (deep bite)
GDP not happy to monitor
What are the risks/problems with fixed retainers?
Decalcification Unwanted tooth movements Only retain anterior segments May complicated planned restorative treatment Hinder interdental cleaning Speech issues (usually resolve)
According to Renkema et al. 2011 what % of bonded retainers maintained alignment of the lower labial segment at 5 years?
90.5%
According to Pandis et a. 2014 what % of bonded retainers failed within 2 years?
46.4%
What is the fabrication process of fixed retainers?
Impression over fixed appliances
Model cast
Multistrand wire is formed accurately against the palatal/lingual aspect of the model
A jig or VFR may be used to facilitate fitting
Clinical placement
What is the clinical placement of fixed retainers?
Prophy brush/composite removing bur/sandblast tooth surface
Isolation with cheek retractors, slow suction/cotton wool
Etch (check and re-etch if required)
Prime and seat retainer
Bond to 1-2 teeth initially
Check occlusion once fully bonded
What is the relationship between stability and retention?
Before treatment the teeth are in a position of balance between occlusal and soft tissue forces
After treatment a new position of balance must be found
What is the cause of post-treatment change?
Arch width and arch length constriction is a normal physiological process
Teeth continue to move throughout life
What are the clinical variables that affect stability?
Large overjet and severe class II cases Overbite Anterior openbite Expansion Lower incisor position Rotations Diastema’s
What can be done to minimise relapse?
Avoid enlargement of lower arch
Do not alter AP position of LLS teeth
Correct rotations in early treatment
Consider interproximal reduction to increase area of interproximal contact
Consider active retention for severe class II cases
Achieve good incisor relationship at the end of treatment
Consider free to my at end of treatment prior to debond
Move upper incisors within control of lower lip
Maximise buccal interdigitation
