Functional Appliances in Orthodontics Flashcards
What do functional appliances do?
Change the position of the mandible - open and forwards
Stretch muscles: apply forces to bones and teeth - condyle out of the glenoid fossa
Use growth
When do you use functional appliances?
Use during active growth period
Who wears functional appliance?
Class II div 1 incisors with increased overjet
Class II molars
Actively growing patient
What is the class II aetiology?
86% Mandibular retrusion
14% Maxillary protrusion
What are the 2 ways of assessing skeletal pattern?
Clinical assessment - assess visually, posture test
Cephalometric analysis
What are the ceph analysis figures?
SNA 81 degrees
SNB 75 degrees
ANB 6 degrees
MxMnPA = 30
What does the clinical assessment involve?
Patient sitting upright
Look at the profile
Posture test - bring the mandible forwards - does the patient look better or worse?
What is the posture test?
Posture the mandible forwards - get an improvement in the profile
Lips relaxed, not forced together
Who should avoid functional appliances?
Non-motivated patients
Class I molar relationship - increase the length of treatment
High FMPA - Frankfort mandibular plane angle
What does the ideal time for functional appliance depend on?
Stage of development:
Dental - late/mixed permanent dentition - need 4’s
Emotional - motivation
Physical - height
What are the 2 measurements of standing height?
Height curve: Standing height - skeletal growth
Velocity curve: rate of growth per year - shows how quickly growing
When is the best age range for functional appliance
13-16
When are the rapid growth periods for boys? and girls?
Boys 11-13
Girls 10-12
What are the different functional applicances?
Twin block
Activators: Medium-opening activator, Andresen, Harvold, Bionator
Frankel
What is the twin block appliance?
Separate upper and lower appliance - blocks fit together which postures the mandible forwards
Removable functional appliance
Work 24 hours except sports and cleaning
Midline screw - widen mandible
Crib on lower 6 to increase stability
What are the advantages of twin block?
Aesthetic Patient can move the mandible Full-time Robust Can expand the upper arch/reactivate Can integrate with fixed appliances if want to straighten them Posterior teeth still free to erupt
What is a medium opening activator?
Capping over lower incisors
Leaves the posteriors to do what they want
Tend to erupt/ reduce the overbite
Cribs on the upper 4 and 6 - gives more stability
What is the fixed (herbst) appliance?
Consists of a barreld
Add a collar
piston arrangement to allow chewing
What is the Frankel appliance?
Soft tissue borne
Sheilds alter the soft tissue balance
Moves the tissue out of the way, allowing the teeth to find natural position
If distort it - difficult to repair
Not as robust, not as easy to wear as twin block
Crib on 3 and 2 to prevent fracture at the midline
Can add more acrylic to reacitvate
No 4’s then use labial bow
What is the dental mode of action of functional appliances?
Mandible moves down and forwards
Retraction of upper incisors
Upper labial segment retroclines with or without labial bow
Lower labial segment proclines controlled eruption of lowers into class I
What is the skeletal mode of action of funcional appliances?
Forward movement of the mandible
Condyle secondary or primary groth site
Inhibits normal growth of the maxila - can do this by fitting head gear
73% correction due to dento-alveolar 27% due to skeletal
What are the dental effects of functional appliance
- Upper labial segment retroclines
- Lower labial segment proclines
- Controlled eruption of lowers into class I
What are the skeletal effects of funcitonal appliance
Inhibits normal forward groth of maxilla
Forward movement of the mandible
What is are the percentage effect of the funcitonal appliance on skeletal and dento-alveolar
Skeletal 30%
Dento-alveolar 70%
