Treatment with functional appliances Flashcards
what are functional appliance?
> Variety of appliances which alter the sagittal and vertical position of the mandible (A-P position) (when worn by the patient)
> This repositioning generates muscular forces which result in orthodontic and possible orthopaedic changes
what are the 5 main functional appliances used and who developed them?
- Monobloc = Pierre Robin
- Activator = Andresen
- Bionator = Balters
- Functional Regulator = Frankel
- Clark Twin Block = Clark (most widely used)
what are the classifications of functional appliances
> Fixed functional appliances (common in some countries but not here)
> Removable functional appliances (most commonly used)
what are the most established fixed functional appliances?
- Herbst appliance
- “Fixed Twin Block”
what is a Herbst appliance?
> piston mechanism each side
> attached to fixed appliance (so functional and fixed at the same time)
what are the positives of a Herbst appliance?
> less cooperation required
> more effective??
> use simultaneously with FA
what are the negatives of a Herbst appliance?
> complex design
> time consuming to fit
> more frequent breakages
what are examples of removable appliances?
> Twin Block (Clark)
> Andresen activator (Andresen)
> MOA (medium open activator)
> Bionator (Balters)
> Dynamax (Bass)
> Functional regulator (Frankel)
what are the theoretical advantages of functional appliances?
> improve facial aesthetics
> correct dental relationship
> reduce the need for extractions
> reduce the time needed for fixed appliance therapy
> reduce chairside time
> reduce incidence of trauma
> reduce need for headgear
> removable = facilitates plaque control
what are the proven advantages of a functional appliance?
> do produce a clinically significant correction in the A-P dental relationship
> do provide efficient anchorage reinforcement prior to FA treatment
> allows for FT wear – thereby more effective than HG at correcting molar relationship
> can be used during mixed dentition phase
> can attach auxiliaries / expand upper arch etc
what are the disadvantages of a functional appliance?
> cannot produce detailed tooth movement
> do not produce a clinically significant effect on skeletal bases
> can cause excessive proclination of lower incisors
> may cause AOB in patients with increased LAFH / minimal OB
> demand high level of patient cooperation
what is the advantage of a twin block over other functional appliance?
> well tolerated (2 piece design)
> full-time wear possible
> eating possible (in theory)
> versatile appliance
eg. elastics / sectional FA
> expansion of upper arch possible
> can add headgear
> can add fixed appliance
> possible to secure CTB to FA
how do functional appliances work?
> The subject of varying opinion, but forces arising from the facial soft tissues are undoubtedly the source of the main tooth movements
what are the mode of actions of functional appliances?
> orthodontic effect - dentoalveolar
> orthopaedic effect - jaw growth ?
what are the dentoalveolar changes we see during functional appliances when trying to achieve a class 1 occlusion?
> Upper arch
- retroclination of upper incisors
- distal movement of upper molars
> Lower arch
- mesial movement of lower teeth, including lower incisors
- vertical movement of lower posterior teeth
what are the orthopaedic changes observed during tx with functional appliances?
> (Controversial…conflicting results (& opinions!!))
> maxilla
- 1-2mm of long term restriction in growth possible
- may more long lasting than mandibular change
> mandible
- 1-2mm of extra short term growth possible
evidence for long-term gain is limited
> recent RCTs would seem to support such changes
what are the indications for functional appliances?
> Mild, uncrowded Class II with well aligned teeth
- uncommon in Western Europe
> As first phase in more severe Class II’s, with second phase of FA
> Anchorage reinforcement in Class II cases
- prior to FA Tx
> Interceptive treatment
- early Tx to reduce very large OJ
- questionable use in certain countries (stiff private competition)
what are the limitation and contraindications of functional appliance tx?
> poor cooperation
> non-growing PTs
> timing of treatment (age 12)
> individual tooth movements…difficult
> high angle cases
> variability of response
what factors dictate when we can start treatment with a functional appliance?
> dental factors
- erupted permanent teeth (first premolar erupted)
- trauma risk
> psychological factors
- O’Brien et al 2003
> growth
- difficult to predict
- may not make much difference in any case
what are some characteristics to look at to judge the timing of treatment based on growth?
> AGE
CHANGES OF HEIGHT
> Hand-wrist radiographs
> Hormone levels
> Secondary sex characteristics
what continue to grow for longer the mandible or the maxilla?
> the mandible continue to grow until around 19
> the maxilla continue to grow until around 17
> the mandible has larger growth spike also in this pubescent years
> eg. class 3s will worsen
what are some characteristics to look at to judge the timing of treatment based on dental factors?
> can start functional treatment in mixed dentition phase
- await eruption of 1st premolars
> time start of functional phase to allow progression straight into FAs
- avoid temptation to start functional Tx too early (don’t start until 11)
- avoid significant pause between 2 stages
> aim in general to start functional treatment at 11/12 years of age
what are the stages for a functional appliance?
- Assessment
- treatment planning
- consent - Imps & bite / laboratory prescription
- Fit appliance
- take baseline measurements - Review visits
- review measurements - Retention
- night time wear
- plan fixed appliances
why do we take bite registration for a functional appliance?
> Estimate amount of sagittal advancement of mandible needed
- as a rule of thumb this is edge to edge unless the patient has a really deep overly
- ensure the dental centrelines are coincident
how do you take a bite registration for a functional appliance?
> Select and try in ProJet jig
- Colour coded
- Insert with single slot to lower
- Demonstrate to patient
> Soften wax into horseshoe shape
- Wax bite should be 2-3mm thicker than planned vertical opening
- Carefully apply to ProJet jig
> The softened wax bite and jig are placed against the upper teeth
- Patient is asked to bite into desired position
- Ask patient to hold face mirror while recording bite
> Wax bite removed from the mouth
- Allow wax bite to cool / cool under running water
> The cooled wax bite is tried in again
- Critical to ensure accurate fit against upper & lower teeth
- If necessary soften and carefully any errors
Consider retaking if not correct
what is the prescription for the upper functional appliance?
> clasp 4s and 6s
> split baseplate and screw
> labial bow?
> acrylic blocks
what is the prescription for a lower functional appliance?
> lower incisor capping or ball clasps
> clasp lower 4s +/- 6s
> acrylic blocks
when are review appointments for functional appliances?
> every 6 weeks
what assessments are carried out at review appoints for functional appliances?
> asses cooperation
- speech
- handling / ease swallowing / hypersalivation
- talk to parent
> measure overjet
> record molar relationship
> adjust clasps as necessary
> check / start expansion
> update patient / parent on progress
- Study models
what advice do you give instructions for patient for a functional appliances?
> parent present
> full-time wear essential
> remove appliance for
- eating / cleaning / rough sports / swimming
> use box
- TLC
> OHI
- appliance and dentition
> written instructions
- to back up verbal instructions
what are the key points of retention post treatment?
> to assess stability of the result
> over-correct (instead of 2mm go to 0mm)
> night-time wear (initially full time wear)
> review closely
> explain rational carefully to PT and parent (get over the finish line and then some)
