W2 - Ortho Relapse / Retention - Abdalla Flashcards
What are the different orientations of gingival connective tissue collagen fibre bundles?
- Periosteogingival fibres
- Inter-papillary fibres
- Transgingival fibres
- Circular and semicircular fibers
- Transseptal fibers
- Intercircular fibers
- Intergingival fibres
Gingival tissue reorganisation
What is it?
Role in ortho?
Connective tissue fibers are twisted/stretched after ortho
- Need time to re-organise
- Otherwise, teeth will relapse
How long does it take for periodontal fibers to reorganise
3-4 months
How long does it take for gingival fibers to reorganise
4-6 months
How long does it take for trans-septal fibers to reorganise
12 months
What ortho movements are more prone to relapse?
rotations
What is pericision aka circumferential supracrestal fiberotomy
Incision of supracrestal fibers around ortho treated teeth
- By cutting fibers, you speed up the rate of periodontal reorganisation
- Reduced rate of relapse in theory
- Not commonly done
4 factors that affect retention
Periodontal / gingival anatomy
Soft Tisses
Occlusal balance
Growth / development
How do the soft tissues affect occlusal positioning/balance
Must be equal force between tongue and cheek
- Teeth should be in the “neutral” area
- If not positioned neutrally → relapse due to force from cheek/tongue
Extraction of premolars necessary
otherwise → soft tissues will press against teeth (relapse)
What must be addressed first in these cases with lip incompetence / lip trap?
Lip trap must be addressed
otherwise will have soft tissue imbalance affecting ortho
How do you measure mandibular incisor extrusion?
Compare mandibular occlusal plane angle to mandibular plane angle
How does the maxillary arch change and develop over time?
Intercanine width increases (1.7mm btw 13-45yo)
Intermolar width decreases by 1mm by 45
How does the mandibular arch change over time?
Intercanine width decreases 1.2mm (13-45 yrs)
Intermolar width decreases by 1mm (by 45 yrs)
Why is it common to see mandibular teeth become crowded as people age
Intercanine width slowly decreases 1.2 mm
Maxilla termination of growth
Girls - 15
Boys - 17
Mandible termination of growth
girls - 17
boys - 19
Why does the mandible keep growing after the maxilla stops?
Cephalo-caudal gradient of growth
- Maxilla closer to top of head, thus stops earlier
Pros and cons of removable retainers (2 and 2)
Pros
- Can be worn part-time
- Can remove for cleaning
Cons
- Relies on compliance
- More intrusive
Pro and con of fixed retainers
Pro
Doesnt rely on compliance
Con
More difficult to clean
Advantages of acrylic retainers with labial bow (3)
- Robust- can eat without them getting damaged
- Allows posterior occlusal settling
- Anterior bite plane can be incorporated to retain corrected deep bites
Advantages of vacuum formed retainers (5)
- Cheap
- Aesthetic
- Decreased speech interference
- Nighttime only
- Prosthetic teeth can be incorporated
Pros (2) and cons (3) of bonded/fixed retainers
- Discreet
- Doesn’t rely on compliance
Cons
- Affects OH
- Can become active and cause mvmt
- Upper retainers can cause occlusal contact
What happened here?
Stainless steel bonded retainer became active
Which ortho treatments have limited retention (low risk of relapse)
- Corrected crossbites
- Impacted canines treated with extraction
- Dentitions where teeth have been separated to allow for eruption (Dahl)
risk of relapse?
Low
Limited retention
Which ortho treatments have moderate retention (medium risk of relapse)
Class 1 cases
Class 2 Exo cases
Corrected class 1 and 2 deep bites
Corrected class 2 div 1
Risk of relapse after tx?
Moderate
Which ortho treatments have high retention (high risk of relapse) (5)
- Lower arch expansion
- Rotation
- Considerable spacing
- Midline diastemas
- Teeth that are placed in position outside of soft tissue envelope (think lip/cheek balance)
Risk of relapse after tx?
High
Adjunct methods to assist with retention (3)
Pericision
Extraction of wizzies
Eliminate parafunctional habits (thumb suck)
Why is lifelong retention unlikely?
Dentition naturally changes with age - relapse is very likely
Pts should be advised of this
- Pts should only undergo ortho if they are willing and capable of following prescribed retention regimen following treatment (wearing retainers)
