Retention and stability Flashcards
Define retention
Maintenance of intra-arch relationship (alignments) and inter-arch relationships (static and dynamic occlusion)
Define relapse
Tendency for a treated malocclusion to return to the original features of occlusion (BSI)
What else can be considered relapse?
Any change to the teeth that occurs after treatment e.g. late lower incisor crowding
What is the importance of retention?
Without retention, the teeth will return back to normal
What are the aetiological factors for relapse?
Gingival and periodontal factors Post tx growth and maturation Ageing Soft tissue factors Occlusal factors
What are the gingival/periodontal factors associated with relapse?
If the fibres have not remodelled, there is tendency for them to pull the tooth back to the original position
How long does it take for gingival/perio fibres to reorganise post op?
4-6 months
Some may take 8 months
What type of post treatment growth can cause relapse?
- Late mandibular growth can cause late lower incisor crowding
- Any unfavourable growth with class II or III cases
What changes occur as you age and how can this cause relapse?
Reduction in intercanine width and arch length - thus causing tertiary crowding
What soft tissue factors can increase risk of relapse
- Tongue pushing forward
- Incompetent lips post op
Examples of occlusal factors that can reduce the risk of relapse
- Good interdigitation
- Centroid position and an occlusal stop (in overbite correction)
- For anterior XB correction adequate overbite is required
Importance of soft tissues in correction of class II div 1
The upper incisors ideally should be in control of the lips post op and there should be competence to allow stable overjet reduction
Why are changes to the inclination of the LLS prone to relapse?
The further the teeth lie from the zone of balance, the more unstable the position is
Why are space closures and corrected rotations prone to relapse
Transseptal fibres take long to reorganise and they may pull the teeth back into the original position
List areas prone to relapse post ortho treatment
- close spaces/diastemas
- correction of severe rotations
- Excessive lower incisor proclination or retroclination
- Reduced OJ with incompetent lips
- combined perio and ortho
How can you reduce risk of relapse of corrected rotations
- Overcorrect by 110% to give 10% leeway
- Incise the fibres (pericision/fiberotomy) - not common
What are retainers?
Passive orthodontic appliance used to maintain the post treatment position of teeth
What is a normal retainer regieme
- Full time for 3-6 months
- Night time wear indefinitely
What influences the type of retainer chosed
- Compliance of patient
- OH
- Predicted stability post op
- Patient preference and expectations
What are the types of retainers
- Removable - Hawley and vacuum formed retainer
- Fixed/bonded
What is a hawley retainer made of
Acrylic baseplate
0.7mm SS adams clasps on 6s
0.7mm SS labial bow
May have U loops for canine
Advantages of Hawley retainer
Robust
Simple to construct
Can incorporate other things e.g. prosthetic tooth or passive bite plane
Easy to clean
Disadvantages of Hawley retainer
- Poorly tolerated due to issues with speech
- Compliance issues as it is removable
- Poor aesthetics
- Expensive
- Inferior to VFR in maintaining lower incisor position
Describe vacuum formed retainers
Polyvinyl chloride material
Full coverage of teeth up to the 7s
Advantages of VFR
- Cheap
- Well tolerated
- Good aesthetics
- Better lower incisor control than hawley
- Less likely to break
Disadvantages of VFR
- Compliance issues
- Poor hygiene may contraindicate as the plastic engages the undercut gingival to the contact point
What is a fixed retainer?
Ortho SS wire bonded lingually and palatally of the anterior teeth (usually 3-3)
Advantages of fixed retainer
- Well tolerated
- No compliance issue
- No long term perio issue if there is good plaque control
Disadvantages of fixed retainers
- Time consuming
- Technique sensitive
- If deep bite, it may interfere with occlusion
- High failure rate
- May debond without realising
- Need long term maintenance
- Hard to achieve plaque control
What is the only tooth correction that is deemed self-retentive?
Correction of a single tooth in anterior crossbite will be self-retentive if there is sufficient overbite
