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Functional appliances
Background
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Functional appliances are conceptually based on Moss’
functional matrix theory
Functional matrix theory proposes that functional
matrices, tissues like muscles and glands influence
skeletal units such as jaw bones and ultimately control
their growth
Form follows function
Functional appliance types
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Orthodontic functional appliances may be active or
passive:
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Active appliances reposition the mandible so that the condyle
is forced out of the glenoid fossa and this in turn is thought
to stimulate the posterior/superior growth of the condyle
Passive appliances act by repositioning the musculature
associated with the mandible so that the jaw bone itself
responds by growing to the new equilibrium position
Passive functional appliances
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Frankel
Active functional appliances
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Fixed active functional appliances
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Herbst
Active functional appliances
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Removable active functional appliances
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Bionator
Active functional appliances
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Removable active functional appliances
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Woodside activator
Active functional appliances
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Removable active functional appliances
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Twin-block appliance
Duration and timing of wear
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Functional appliance treatment should be
started before the pubertal growth spurt
This is the time when the mandible may exhibit
increased growth which may be influenced
Functional appliances should be worn for at
least 10-12 hours a day
These appliances should be worn at nighttime as
this is when growth takes place
Evidence of clinical effectiveness
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A Cochrane review, published in 2008, studied
orthodontic treatment for prominent upper teeth in
children
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The study concentrated on primary outcomes including the
prominence of upper front teeth and the relationship
between upper and lower jaws
The secondary outcomes compared included self-esteem,
injury to teeth, joint problems, patient satisfaction and the
number of appointments during active treatment
Evidence of clinical effectiveness
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It has been shown that when front teeth stick out by
more than 3mm, they are twice as likely to be injured
The Cochrane review included eight clinical trials, based
on data from 592 patients with Class II Division 1
Three trials, evaluating 432 patients, compared early
treatment (before the age of 10) with a functional
appliance compared to no treatment
It was found that functional appliance treatment
resulted in significant decreases in overjet and the ANB
angle
Evidence of clinical effectiveness
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When the same patients received the second phase of
treatment (full fixed treatment) and when they were
compared to patients who only received one phase of
treatment in adolescence, it was found that there were
no significant differences
Other reviews have also found that although the overall
effect of early treatment was not significant, the
patients did have a milder malocclusion at the start of
full fixed treatment
Evidence of clinical effectiveness
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A systematic review by Cozza et.al. included 18
retrospective longitudinal controlled clinical trials
It was found that functional appliances did result in a
significant elongation of mandibular length (>2mm)
It was concluded that the effect of growth modification
is the greatest during the pubertal growth peak
What does this mean?
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According to the evidence one should not use
functional appliances as they are not necessarily more
efficient than one phase treatment
Should we rely only on evidence in guiding our clinical
decisions?
I would argue that although sound scientific evidence is
the most important aspect of clinical practice, it is not
the only factor to consider
What does all this mean?
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Indeed, care for our patients extends beyond all
the evidence available
True care also includes:
Honesty
 Empathy
 Being genuine
 Patient centered approach
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Refernces
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http://farm1.static.flickr.com/47/154578698_6011a485ce.jpg
http://www.sleepingtiger.org/blog/wpcontent/uploads/2007/08/maxyawns.jpg
http://imagecache2.allposters.com/images/146/PP0195.jpg
http://www.nimrodental.co.uk/appliances/media/functional5.jpg
http://coloradospringsortho.com/Web%20site/About%20braces_files/herbs
t_appliance.jpg
http://www.weisskircher.de/bilder/bionator.jpg
http://www.tanos.co.uk/braces/bkb/images/activatorwoodside.jpg
http://www.orthodentlab.com/products/images/photos/TwinBlock1.jpg
References
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Harrison JE, O’Brien KD, Worthington HV. Orthodontic treatment for prominent
upper front teeth in children (review). The Cochrane Collaboration. John Wiley &
Sons, 2008.
Nguyen QV, Bezemer PD, Habets L, Prahl-Andersen B. A systematic review of the
relationship between overjet size and traumatic dental injuries. European Journal of
Orthodontics 1999;21(5):503-515.
Pavlow SS, McGorray SP, Taylor MG, Dolce C, King GJ, Wheeler TT. Effect of early
treatment on stability of occlusion in patients with Class II malocclusion. American
Journal of Orthodontics and Dentofacial Orthopedics 2008;133:235-244.
Dolce C, McGorray SP, Brazeau L, King GJ, Wheeler TT. American Journal of
Orthodontics and Dentofacial Orthopedics 2007;132:481-489.
Cozza P, Baccetti T, Franchi L, De Toffol L, McNamara JA. Mandibular changes
produced by functional appliances in Class II malocclusion: a systematic review.
American Journal of Orthodontics and Dentofacial Orthopedics 2006;129:599.e1599.e12.