Functional appliances Flashcards
what are functional appliances?
Variety of appliances which alter the sagittal
and vertical position of the mandible (when
worn by the patient)
This repositioning generates muscular forces
which result in orthodontic and possible
orthopaedic changes
What are the main functional appliances?
Clarktwin block
Andresen activator
Classification of functional appliances?
Fixed functional appliances
Removable functional appliances
Fixed functionals?
Fixed twin block
Herbst appliance
How does a Herbst appliance work?
piston mechanism each side
attached to fixed appliance
+
◦ less cooperation required
◦ more effective??
◦ use simultaneously with FA
-
◦ complex design
◦ time consuming to fit
◦ more frequent breakages
What are the removable functionals?
Twin Block (Clark)*
Andresen activator (Andresen)
MOA
Bionator (Balters)
Dynamax (Bass)
Functional regulator (Frankel)*
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
Proven advantages
of functional appliances
do produce a clinically significant correction in
the A-P dental relationship
do provide efficient anchorage reinforcement
prior to functional appliance treatment
allows for full time wear – thereby more effective than headgear at correcting molar relationship
can be used during mixed dentition phase
can attach auxiliaries / expand upper arch etc
Disadvantages of functional appliances
cannot produce detailed tooth movement
do not produce a clinically significant effect on
skeletal bases
can cause excessive proclination of lower
incisors
may cause anterior open bite in patients with increased lower anterior face height / minimal overbite
demand high level of patient cooperation
Advantages of clark twin block vs other functionals
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 clark twin block to functional appliance
Example of what clark twin block does
Carries elastic traction to canine
How to 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.
Mode of action
Orthodontic effect…..dentoalveolar
Orthopaedic effect…..? jaw growth
Mode of action orthodontic effect? upper and lower arch
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
this allows class I occlusion to be achieved
Mode of action- orthopaedic changes
Controversial
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
what patients are suitable?
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 functional appliance
Anchorage reinforcement in Class II cases
◦ prior to functional appliance Tx
Interceptive treatment
◦ early Tx to reduce very large overjet
◦ questionable use in certain countries (stiff private
competition)
limitations and contraindications*
poor cooperation*
non-growing PTs*
high angle cases*
timing of treatment
individual tooth movements…difficult
variability of response
Timing of treatment
dental factors
◦ erupted permanent teeth
◦ trauma risk
psychological factors
growth
◦ difficult to predict
◦ may not make much difference in any case
timing of treatment- growth
Age
Height
Hand-wrist radiographs
Hormone levels
Secondary sex characteristics
Timing of treatment- 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 functional appliances
◦ avoid temptation to start functional Tx too early
◦ avoid significant pause between 2 stages
aim in general to start functional treatment at
11/12 years of age
Stages for a functional appliance
(CTB )
Assessment
treatment planning
consent
Imps & bite / laboratory prescription
Fit appliance
take baseline measurements
Review visits
review measurements
Retention
night time wear
plan fixed appliances
Bite registration for functional
appliance (CTB )
Estimate amount of sagittal advancement of
mandible needed
As rule of thumb this is edge to edge
Ensure dental centrelines are coincident
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
Prescription
- design appliance- upper and lower
upper
◦ clasp 4s and 6s
◦ split baseplate and screw
◦ labial bow?
◦ acrylic blocks
lower
◦ lower incisor capping or ball clasps
◦ clasp lower 4s +/- 6s
◦ acrylic blocks
Review visits
asses cooperation
◦ speech
◦ handling / ease swallowing / hypersalivation
◦ parent
measure overjet
record molar relationship
adjust clasps as necessary
check / start expansion
update patient / parent on progress
◦ SMs
