Stability and Retention in Orthodontics Flashcards
What is retention
Retention is the phase after active orthodontic treatment when teeth need to be maintained in their new positions
What is the objective of retention
Minimise relapse
What is defined as relapse? (BSI and Patient Perspective)
BSI: The return, following correction, of features of the original malocclusion
Patient: Any change from the final tooth position at the end of treatment (could be caused by age) - UNPREDICTABLE
What factors determine the stability post ortho treatment
- Periodontal and gingival tissues (soft tissue)
- Musculature (soft tissue)
- Apical base (Arch widths and mandibular incisors)
- Occlusion
- Growth
How does orthodontic tooth movement affect the periodontal and gingival tissues
Causes widening of PDL spaces and disruption of collagen fibre bundles
How long does reorganisation of periodontal and gingival tissues take (important for stability)
Alveolar bone remodelling: 1 month
PDL reorganisation: 3-4 months
Gingival tissues takes longer
Collagen fibres: 4-6 months
Elastic Supracrestal fibres: can displace a tooth up to >1year after debond
How does musculature of the lips, cheek and tongue affect the stability post ortho?
How can this be reduced?
Can aid or hinder stability depending on the direction of tooth movement
Avoiding encroachment beyond the neutral zone
How does occlusion affect the stability post ortho
- Well-interdigitated teeth are more stable (poor evi)
- Stability of deep overbite correction associated with positive occlusal stop
- Stability of single tooth crossbite correction associated with adequate overbite (at least 2mm)
How does growth affect the stability post ortho?
- Can cause recurrence of skeletal discrepancies –> deterioration of occlusal relationships
- Small age changes throughout life can lead to late lower incisor crowding - Mandibular rotation or forward growth –> Increases force of lower lip onto lower incisors –> crowding
What type of skeletal discrepancy worsens with age
Class III: Man prognathia
Is third molars a cause of relapse or late lower incisor crowding?
NO
What are the implications of stability in terms of planning treatment
- Timing (during or after growth)
- Correct diagnosis, treatment plan and mechanics
- Eliminate etiology of malocclusion (esp. habits)
- Minimise changes in arch form (esp lower)
- Consider magnitude of tooth movement
Prevention: Ensure adequate space for eruption
What are the implications of stability in terms of executing treatment
- Correct tooth position early (rotation, extrusion)
- Position teeth within basal bone (inclination. position)
- Achieve good intercuspation
- Overcorrect occlusal relationships and tooth position (rotation) - generally not done
How long should retention be put in place for?
- Adequate time for remodeling of periodontal and gingival tissues
- Until growth completion
How to improve retention?
- Permanent fixed/long-term retention
- Adjunctive techniques prn eg. circumferential supracrestal fiberotomy (CSF) - for severely corrected teeth, frenectomy
What is a case with limited need for retention?
Single tooth crossbite with sufficient (at least 2mm) of overbite
What are some cases which are prone to relapse
- Rotations
- Considerable spacing due to small/missing teeth, median diastemas
- Movements involving significant expansion (buccal movement)
- Periodontically involved teeth
Why do rotation cases relapse
Elastic supra-crestal gingival fibres remodel slowly (>1year) and hence there is residual tension and 20# relapse
Hence fixed retainers should be considered
Why do large diastemas relapse
Failure of gingival elastic fibres to cross the midline
Aggravated by large or inferiorly attached labial frenum (moves apically till 12)
What is the difference between orthopedic (young) vs surgical maxillary skeletal expansion
Orthopedic: gradual and stable
Surgical: drastic expansion hence less stable
Why are cases involving movements involving excessive expansion prone to relapse
Maxillary skeletal expansion: Time for bone infill at the suture, elasticity of palatal soft tissue
Dental expansion: pressure from soft tissues + risk of moving teeth beyond alveolar bone
Why are cases involving periodontally involved teeth prone to relapse
- Loss of bone and soft tissue around the teeth
- Soft tissue balance altered (less opposed –> more likely to drift(
What cases should have permanent or semi-permanent (1-2 years) retention?
5
- Severe rotation or labiolingual malposition
- Considerable or generalized spacing
- Anterior dental expansion including excessive incisor proclination
- Compromised periodontal support
- Impacted incisors and canines
What are the two different types of removable retention appliances
Hawley type retainer (and its variations)
Vacuum formed retainer
How does a Hawley-type retainer prevent relapse of mild SK CII and III
Acts as a modified functional appliance
Prevents deep bite by having a thickened acrylic as an anterior bite plate
Can also be modified to have a twin block
Where does hawley-type retainers extend to
Lingual surfaces of second molars
What type of retainer should palatal expansion patients use
Palatal coverage retainers
What type of retention clasps are present on hawley retainers
Adam clasps on 6s, Circumferential clasps, Ball clasps
Should not have occlusal interferences
What is a U-looped labial bow on Hawley-type retainers
Round SS 0.020-0.036 inch wire
Contacts 6 anterior teeth or only 4 max ant teeth
Improves fit and anterior retention
What is a circumferential Hawley-type retainer
When the U-looped labial bow crosses occlusally distal to the canine
Keeper wires
What is a wraparound Hawley-type retainer
When the U-looped labial bow continues to contact buccal surface of posterior teeth
What is the benefit of circumferential retainer?
Minimises occlusal interference and holds extraction spaces closed (with a pontic)
Occlusal rests present if needed to prevent supraeruption
What are the advantages of Hawley-type retainers
5
- No coverage of occlusal surfaces: allows “setting-in of occlusion
- Robust
- Good for maintaining transverse dental expansion
- Passive biteplate can be inorporated to maintain deep OB correction
- Incorportate components to maintain growth correction
What are the disadvantages of Hawley-type retainers
3
- More time consuming to fabricate
- May not have a tight-fit around all teeth
- Poor at retaining selected complex vertical movements
What are vacuum formed retainers
Plastic sheets of varying grades and varying thickness (0.5-3mm) and properties
Trimmed to 2mm apical to gingival margin
What are the advantages of vacuum formed retainers
5
- Aesthetic
- Ease of fabrication
- Economical
- Less effect on speech
- Protects teeth in grinders/clenchers
What are the disadvantages of vacuum formed retainers
2
- Covers occlusal surfaces - may limit “setting of occlusion”
- Poor at retaining selected complex vertical movements
What are types of fixed retainers
Rigid lingual bar:
3-3 attached only to canines
28-30mil steel attached by CR
Multistrand wire retainer:
Bonded to individual teeth
Braided steel wire of 17.5mil diameter
For severe rotations/labiolingual displacement
What are the variations in the designs for fixed retainers
Hygienic Design : for flossing
Occlusal stops (CR): prevent bite deepening
Can fixed retainers be used with removable retainers
Yes
Are fixed retainers very rigid
No, they should be sufficiency flexible to allow physiological tooth movement
Should upper fixed retainers contact lower incisors
Minimised
Increased debonding
What are the advantages of fixed retainers
3
- Invisible from the front
- Reduced need for patient compliance
- Good for potentially unstable outcomes
What are the disadvantages of fixed retainers
4
- Localised retention (usually only 3-3 unless premolars ectopic)
- Wire distortion/fracture or debonding - unwanted dental movement –> close monitoring required
- Complicates interproximal hygiene
- Challenging to adjust or make chairside
What factors should be considered in retention
- Appliance type
- Compliance
- Duration
- Type and stability of correction
- Initial malocclusion
- Etiology of malocclusion
- Age of patient
- Any growth modification
- How many teeth have been moved and how far
- Speed of correction
- Final tooth positions and occlusion
- Periodontal support
- Muscular pressure, Interproximal contact
- Quality of result (any settling in of occlusion needed)
- Oral hygiene
- Patient expectations
- Patient preference
How long should retention be kept for
No consensus, longer is better
AT LEAST 12 months
Full-time for minimally the first 3-4 months (some recommend 6 months)
Subsequently can reduce to part–time
If there is significant residual growth: Part-time until growth completion
Exception: cases with high chance of relapse may benefit from permanent retention
Removable retainer delivery checks
Vacuum formed:
No gap between appliance and tooth
No impingement on soft tissue (blanching
Hawley-type retainer:
Acrylic and wires should adapt closely to teeth
No soft-tissue impingement
Extend occlusally by approximately half the palatal/lingual surfaces
Check interference
Loose/tighten adams clasp and labial bow
Fixed retainer delivery checks
Check passive adaptation of wire
Ensure no Occlusion
Sandblast ends of retainer bar
Secure retainer with floss
What are the generic guidelines for retention regime
First retention visit 1 month post debond
Subsequent appointment intervals: 3 –> 6 months
F/U for at least a year then optional annual reviews
What are some retainer care instructions?
- Remove when eating/drinking, brushing/flossing, playing contact sports or swimming
- Brush teeth before wearing retainers
- Kept in case
- Kept away from heat and pets
- Breakage/problems with retainers/ loss of retainers to inform provider ASAP
- How to insert and remove
- Duration
- Retainer hygiene
- How to floss/clean interdentally for fixed retainers
- How to monitor for debonding/fracture/distortion
- Compliance with retainer reviews
