S2 - Relapse and Retention Flashcards
Define relapse and retention
relapse - tendency for teeth to return to their pre-tx positions
retention - holding of teeth following ortho in the treated position for a period of time necessary to hold the result -> prevent relapse
Current evident re: retention
- remains a conundrum
- overall insufficient high-quality evidence to recommend retention procedures for stabilising tooth position after treatment with braces, further RCTs are needed
2 types of gingiva and characteristics
free gingiva - close contact with enamel surface and its margin is located 0.5-2mm coronal to the CEJ
attached gingiva - firmly attached to the underlying alveolar bone and cementum by connective tissue and is therefore comparatively immobile in relation to underlying tissues
Describe the connective tissue in gingiva
CT consists of collagen fibres which are arranged into fibre bundles with distinct orientations depending on location
Describe gingival tissue reorganisation in terms of collagen fibres.
- signficant individual tooth movements stretch collagen
- gingival and periodontal tissues need time to re-organise
How long does it take periodontal, gingival and trans-septal fibres to reorganise?
periodontal: 3-4m
gingival: 4-6m
trans-septal: 12m
Which tooth movements are more prone to relapse?
rotations
What is the procedure shown?
Circumferential Supracrestal fiberotomy - scalpel used to cut fibres around tooth to release tension in collagen fibres and they reorganise into a more passive condition, thereby reducing the relapse
not commonly done in aus
4 factors affecting retention
- periodontal and gingival anatomy
- soft tissues (neutral position)
- occlusal balance (retroclined/proclined teeth, anterior plane - intrusion/extrusion)
- growth and development
What is needed in soft tissue and occlusal balance for retention?
- want final position of teeth to be in ‘neutral’ area where equal forces from tongue and lip/cheek so they don’t move
- eliminate any parafunctional habits
What may be done if teeth are moved forward closer to the lip in this image?
may relapse as lip pushes back → 4pm exos so that they could be moved to neutral position instead, more stable result
Why wouldnt you retrocline teeth that are already retroclined and vice versa?
building inherent instability
What must be done in cases with lip trap (lower lip trapped behind upper incisors) causing increased overjet
eliminate lip trap or else relapse
(e.g. functional appliance to move md fwd)
What can/cant be done for this pt
have scope to procline lowers to correct overjet
What can/cant be done for this pt?
proclining lowers will produce unstable position (bcos they are already proclined or normal)
Problem that may arise with treatment of this patient?
anterior open bite
extruding the incisors to close the open bite will likely relapse as ready in correct position
How to check intrusion/extrusion of anterior teeth
angle made by comparing md plane to occlusal plane (occlusal surface of molars to incisal edge of anteriors)
What can/cant be done for this patient?
scope to extrude incisors to close open bite and produce reasonably stable result
What can/cant be done for this pt?
extruding will make more unstable, better treated by orthognathic surgery to move jaws
Hierarchy of stability (from worst to best)
- vertical change: anterior open bite
- transverse change (posterior crossbites, midline discrepancies)
- alignment: irregularity and spacing
- vertical change: deep overbite
- A-P change: class II to I w functional appliance, anterior cross bite
How does growth and development influence dental changes?
most dont change or get slightly bigger after age 13/14 and beyond 45yrs but mandibular intercanine width decreases 1.3mm → lower anterior crowding is common
(whereas intermaxillary and intercanine width increases, upper incisor crowding alot less common)
How does growth and development cause skeletal changes
Growth fairly stable until puberty where it accelerates (good time for ortho), from adolescence to young adulthood we continue to grow
Principal features of maxillary and mandibular post-pubertal growth
- termination of growth (md stops growing later)
F - mx = 15, md = 17
M - mx = 17, md = 19
Facial types and tendency for jaws to grow
dolichofacial - tendency for jaws to grow apart
brachyfacial - tend to grow tgt
Genders and tendency for md to grow in adulthood
F - downward growth of md
M - forward and downward growth of md
Pros and cons of fixed and removable retainers
removable
- usually worn part-time
- can remove for cleaning
- rely on compliance
- more intrusive
fixed
- do not rely on compliance
- more difficult to clean
Acrylic retainers with labial bow. Give 3 advantages and 1 disadvantage. 2 examples
- robust and can be worn during eating without becoming damaged
- allow posterior occlusal settling
- anterior bite plane can be incorporated to help retain deep bites
Hawley retainer, Begg retainer
Describe Hawley retainer
fairly common
components: acrylic base plate, labial bow, Adams clasps for retention
con: quite visible
pros: can activate labial bow or incorporated anterior bite plane if pt had tendency for deep bite or posterior bite plane for tendency toward open bite (to keep molar intruded and incisors extruded)
Describe Begg retainer
similar to Hawley, acrylic base plate and can also be activated but wire around all teeth, no occlusal contacts
Pros and cons of vacuum formed retainers
- inexpensive
- better aesthetics
- decreased speech interference
- can be worn night-time only
- can be modified to produce minor tooth movements
- prosthetic teeth can be incorporated
- must have full posterior occlusal coverage
- patients cant eat or drink with in
- risk of caries with high risk pts
Bonded (fixed) retainers. Pros and cons
- discreet
- do not rely on compliance
- long term failure rate high
- can become active and cause unwanted tooth movements
- care with bonded upper retainers to minimise occlusal contacts
- impede oral hygiene
Risk associated w fixed retainer in pic
bent for free contact points - can easily become active and cause tooth movements
Pro of pre-fabricated Ni-Ti wires
- pre-bent by machine, dont have problem of over activating incase bent in mouth (unlike stainless steel wire) just springs back
Which ortho treatments require limited retention?
- corrected crossbites
- serial extraction cases
- impacted/blocked out canines treated with extractions
- dentition where mx and md have been seperated to allow for eruption of teeth which were previously blocked out
Which ortho treatments require moderate retention?
- class I
- class II extraction cases
- corrected deep bites in class I and II
- corrected class II div 2
Which ortho treatments require high retention?
- expansion in lower arch
- rotations
- considerable spacing
- midline diastemas in upper arch
- teeth placed in position outside soft tissue envelop
e.g. mesialising canines in spaced arch
Importance of consent in retention
patients need to be made aware of limitations of ortho and need for retention
relapse is unpredictable but likely, patients should only undergo tx if willing and capable to follow prescribed retention regimen
Adjunct methods to assist retention (3)
- extraction of 3rd molars
- eliminate parafunctional habits
- pericision
