Ideal case for interceptive class III correction
- Case type: low angle functional shift
- Type of treatment: orthopaedic treatment
Success rate
Systematic review of class 3 interceptive treatment with protraction facemask : Woon 2017
- Overjet improves: 2.5mm
- AOB improves 3.9o
- But short term improvement
Long term study
- 5 year follow up systematic review: 75% stability with protraction facemask, chincup and FR3 Toffol 2008
- 10 year follow up: 81% stability with chincup and expansion Palma 2015
Cause of relapse
- Reduced maxillary growth (2mm) & excessive mandibular growth (4mm)
Expansion with protraction facemask – to loosen the Maxilla to facilitate advancement
- Alt-RAMEC protocol: Repeated expansion and constriction of the maxilla
- Systematic review favouring Alt-RAMEC Vs conventional RME
- SNA 1.2 greater with Alt-RAMEC
Ngan protocol for PFM and Alt-RAMEC
- Alt-Ramec: 2 week expansion, then alternate constriction and expansion for 7 weeks,
- PFM at night, with 30 o to the occlusal plane
- Lower 2 x 4 fixed for alignment and class 3 elastics 018SS
- Day time class 3 elastics
- 9-12 months of PFM
Skeletal anchorage and class III correction: Bone anchored maxillary protraction (BAMP)
- Can be used in patients older than PFM patients
- Systematic review: less chance of skeletal relapse with BAMP Guzman – Barrera 2017
Decision making after 11-14
- Skeletal expansion with TAD supported expansion
- Device: Maxillary-skeletal expansion device
- 2mm + 12mm length: aiming for bicortical anchorage
- PFM 11 months
- Retention: essix with class 3 elastics in retainers- cut out lower VFR and button upper molars – maintain maxillary stimulation
- Seminar in Orthodontics: 2020 Ngan
OVERALL SUCCESS OF INTERCEPTIVE ORTHOPAEDIC TREATMENT IN CLASS 3 CASES IS 70%, IF AETIOLOGY IS MAXILLARY DEFICIENCY
References
Ngan P, Musich D. Stability and relapse of Class III treatment. Stability, Retention and Relapse in Orthodontics. USA: Quintessence Publishing; 2017. p. 93-124.
