effect of functional appliances action of functional appliances limitation of functional appliances effect of regulators

1. 1
Dr. Mohammed Alruby
Effects of functional appliances
on facial growth
Prepared by:
Dr Mohammed Alruby
‫بال‬ ‫عاش‬ ‫من‬
‫كرامه‬
‫شرف‬ ‫بال‬ ‫مات‬

2. 2
Dr. Mohammed Alruby
Definition:
Functional appliances are large category of orthodontic appliances that used primarily to
reposition the bone in order to alter the muscular forces against the teeth and craniofacial skeleton.
Development and philosophy: Rogers
= One of the oldest concept in orthodontic is (the importance of muscles in the etiology and
treatment of malocclusion)
= The leaders of the functional theory are: Bannet, Walkjoff, Paker, Moss, Vander, among others
have been stated that (function dictates form)
= As the bone is the last unit to exert its influence, its form is completely controlled by other
elements which called according to Moss terminology (the functional matrix)
= Kingsley 1880 introduced a bite jumping appliance to alter mandible position and consequently
alter the muscular environment
= Robin 1902 developed a Monoblock that used primarily in treatment of tongue thrust and
glossoptosis.
= Andreson 1908, based upon the above appliance, he introduced appliance that used at the first
as temporary retainer for his daughter after complete correction of class II malocclusion, after his
daughter come from her summer vacation, he noticed unexpected improvement in malocclusion,
then he uses the appliance in other cases and report a similar success
In his explanation, he stated that, activator activate the masticatory system which in turn
produced the favorable changes
Later on Andreson and Hauple worked extensively for many years (1939 – 1945) in the
development of activator. Their idea was to create not only a new appliance but an entirely a new
explanation of orthodontic tooth movement. They laid down the (shaking theory) that based upon
the functional adaptation hypothesis of Willian Roux. This theory stated that ((the muscular stimuli
are adequate influences, creating an adaptation changes in the periodontal tissue and alveolar
bone))
= an extensive research was taking place in Europe to investigate and modify the Andreson
appliance
These efforts led to the appearance of many modifications such as: Harvold, Balter, Frakel
= American orthodontist were not interested in the functional appliances until 1951, when Harvold
joined the staff at university of Foronto and started to teach them the principles of functional jaw
orthopedics
Mode of action of appliances
The original appliance is made to be loose, so that by constantly falling down, it raised
reflexly by the tongue which activates the muscles of mastication to posture the mandible upward
and forward
= Shwartz among others, attributed the changes produced by the appliance to the stretching of
muscles which undergo reflex contraction in an attempt to return to their resting tone. This
concentration creates an inter-maxillary reciprocal force that tend to move upper teeth backward
and lower teeth forward,
So the functional appliances act by transmitting the force of orofacial musculatures to the teeth
and preventing unwanted forces from adversely affecting the teeth.

3. 3
Dr. Mohammed Alruby
Effect of functional appliances
= There are great controversy regarding the effect of functional appliances on facial growth
= Andreson and Fischer among others claim that, functional appliances can alter the environment
of the growing facial skeleton to bring a significant change in growth pattern
= This concept has been rejected by mainly other investigation who suggest that: growth of
craniofacial skeleton is under close genetic control and therefore, the orthodontic appliances can
have a little effect other than to move the teeth within alveolar bone
= one concept is now clear: functional appliances only work well in growing children and have
their greatest effect when growth is most rapid
= Janson, Harvold and Petrovic among others proved that, significant skeletal changes in the
basal bone of maxilla, mandible and glenoid fossa ((maxilla retracted backward, proliferative
activity clearly demonstrated in condyle and glenoid fossa translated forward and downward))
But this studies in human has great limitation for the following:
1- The craniofacial morphology of animals is different from that of human, therefore, the
response will be differing
2- The appliance used with primate experiment were fixed, unlike the appliances commonly
used in human which is removable and worn only part time
3- In animals, the functional forces are applied to produce an abnormal condition, while in
human, we wish to use these appliances to correct abnormal condition. This make the result
of animals studies not comparable with human and if applied, great caution should be taken
= On the other hand, the results of clinical studies were varying conflicting and most of these
studies have not been drawn a clear conclusion, this may be due to the following reasons:
1- Limitation in methodology: for example, precise measurements of bony changes and
studying histological changes can do in experimental animals after scarifying them,
while the only method available in human is the radiographic cephalometry which has
the following limitation:
- Errors inherent in the technique itself such as magnification, blurring, and distortion
- Errors in landmarks identification
- Errors in landmarks reproducibility for superimposition purpose
2- Standardization of all variables is possible in animals but not possible in human such as
cooperation
3- Improper selection of patient: most studies have only included patients who have
achieved successful results, while very few also looked for those patient in whom
treatment failed
4- Great emphasis on case report
5- Small sample size
6- Most of clinical studies did not take into account, the amount of normal growth, which
needs to be differentiated from treatment changes. This can only do by having a control
group of patient with similar age, sex, and malocclusion who will accept to remain
without treatment while exposing regularly to a doses of x-ray.

4. 4
Dr. Mohammed Alruby
= at the present time, the evidence derived from the better scientific studies suggest the
following changes:
I- Modification of muscular environment:
a- Effects on masticatory functions:
Ahlgren reported that activator therapy helps in normalization of masticatory functions, this view
is supported by Sander who recommended the use of activator until adaptation to the normal
chewing pattern
b- Effects on swallowing pattern:
The original appliance in made loose, so that, constantly fallen down. Thus caused a reflex
elevation of the tongue and contraction of mandibular elevators, which also the same
neuromuscular pattern occurs during normal swallowing. In addition, the appliance provides a
screening effect which is very helpful in correction of abnormal pressure habits
II- Dento-alveolar effects:
a- Vertical:
Functional appliances have the ability to control the vertical height of the teeth, stopping some
teeth while permitting other to develop vertically through the selective relief, built in the appliance.
This hypothesis aids in levelling occlusal plane, correcting deep bite cases, correcting open bite
cases, and was supported by Scheldt 1938 and Frankel, Harvold
b- Anterior posterior:
Functional appliances move the maxillary dentition against the mandibular dentition utilizing
reciprocal inter-maxillary anchorage and thus brought about dento-alveolar remodeling in
anterior posterior direction, which is very helpful in the correction of class II and class III,
providing excellent results when skeletal bases permit
= Janson observed that, with Bionator therapy, most of class II correction is gained through dento-
alveolar remodeling when craniofacial skeleton shows anterior posterior harmony.
She also observed that, with this appliance, the teeth eruption is guided into more distal and buccal
directions, which is very helpful in correction of buccal cross bite and some space deficiency
problem
III- Skeletal effects:
The skeletal effects of functional appliances are still a matter of controversy, occlusion from
clinical studies can be divide to the following:
1- Stimulation of mandibular growth:
This concept was first proposed by Fischer 1938 and supported by MacNamara and Owen. But
rejected by others.
2- The changes were in the direction of growth and in mandibular position, but the total
volume of mandible is not affected (Frankel)
3- Rotation of mandible with occlusal plane changes
4- Restraining forward maxillary growth: correction of class II is achieved mainly by
inhibition of maxillary growth rather than stimulation of mandibular growth (Bjork,
Harvold)
5- Backward translation of maxilla: (Nielsen and Owen)
6- Forward translation of glenoid fossa.
N: B:
30% --- 40%: orthopedic changes, 60% -- 70% dento-alveolar changes: by functional appliances

5. 5
Dr. Mohammed Alruby
A- Effects on maxilla:
= Nielsen observed significant effect on maxillary growth with FR2 appliance, several patients
showed a backward rotation of maxilla, so that, the maxilla was more retrognathic at the end of
treatment period.
= these finding were in agreement with the finding of Owen, but dis-agreed with McNamara and
Dellinger
= on the other hand, some investigator stated that, these appliances only restrict the forward
maxillary growth.
= Jacobson reported that ANS and A points were prevented from moving forward by about 1.1mm
and 0.7mm respectively with activator III supported by Bjork and Harvold, and rejected by:
McNamara and Dellinger
B- Effects on mandible:
= Several investigators have reported that FR2 promotes forward growth of mandible
= according to Frankel, the major effect of appliance is redirection of mandibular growth at
condyles
= McNamara reported an acceleration of mandibular growth in patients treated by FR2 this
observation is also suggested by Owen.
= At contrast, Nielsen found no evidence to support this view in children treated with FR2 or
Harvold activator, he stated that, either appliances were not capable of altering the size of the
mandible
N: B:
The conflicting viewpoints may be due to:
1- Variation in the appliance design and the amount of forward positioning and amount of
vertical opening
2- Individual variation in the treatment response.
** changes in the vertical relationship:
- With both activator and FR2: these was increase in LAFH and TAFH.
- Country et al suggested that larger increase in LAFH and TAFH with Harvold
activator is attributed to greater bite opening (1.5mm) with this appliance but in
other appliances the bite opening (2-3mm)
- Nielson et al claimed that increase in ALFH and TAFH was due to vertical eruption
of mandibular molars that lead to ------------- downward rotation of mandible
because both appliances have extension to prevent eruption of maxillary teeth
** changes in horizontal relationship:
- Country and Dellinger among others reported that, overjet is reduced by tipping of
maxillary incisors palatally and mandibular incisors labially
- The apices of maxillary incisors tipped labially from 0.5mm to 1mm
- Excessive proclination of mandibular incisors is the major cause for overjet relapse
C- Changes in glenoid fossa:
= remodeling of glenoid fossa in more anterior dentition seen in experimental animals and there
is some evidence that it may occurs in human if it happens, the TMJ and mandible will become
translated in more forward
Limitation of functional appliances
a- Functional appliances are typically associated with mandibular and maxillary molar
extrusion that help for eliminate deep over bite.

6. 6
Dr. Mohammed Alruby
So: functional appliances are contraindicated in backward rotation of the mandible with
minimal over bite
b- The results depend on patient cooperation
c- Limited correction of growing persons only
d- Difficulty in tooth movement
Effects of activator therapy
1- On mandible: Melan and Trep 1984
Condylar growth during 10 months of activator treatment increased 1.1mm and was redirected
12-degree in more posterior direction
= Forward displacement of glenoid fossa, 1.1mm increase in AFH and 2.5-degree increase in
mandibular plane angle
= Pancherz 1984: the magnitude of mandibular growth was not affected by activator treatment
2- On maxilla:
Melsen demonstrated an increase posterior vertical height that lead to backward rotation of
mandible
= Foesberg: significant decrease in SNA
= Harvold: activator inhibit the horizontal growth of maxilla by 2mm but Pancherz that inhibit by
1.7mm
3- On dentition:
Harvold appliance caused 1.4mm maxillary lingually tipping and 0.5mm incisors lower labial
tipping
4- On soft tissue:
Forsberg: observe upper lip retrusion, nose showed equal forward growth
Effect of functional regulators
1- On mandible:
= Frankel reported forward displacement of pogonion and B point:
4mm / year in 6 – 9 year of age
6mm / year in 9 – 13 year of age
= McNamara: by FR result in mandibular growth by 1 – 2mm / year
= Rigbellis: by FR result in mandibular growth by 1 – 8mm / year
2- On maxilla:
Righellis: no significant horizontal effect on maxilla in patient treated by FR as compared with
untreated
3- On dentition:
Nielsen: FR not induce any proclination in mandibular incisors relative to cranial base
McNamara: improve placement of lower labial pads either too far occlusally or labially would
result in lip bumper effect rather than restriction of mentalis activity.
N: B:
63% dental change, 37% skeletal change ----------------- overjet correction
4- On soft tissue profiles:
Nielsen examined 10 cases Class II div 1 patient treated with FR, all patient showed an
improvement in their soft tissue profile because of an improved lip position
5- McNamara and McDougall: significant amount of expansion by FR, less expansion in lower
arch

7. 7
Dr. Mohammed Alruby
Biomechanics of functional appliances by Nanda
1- Glenoid fossa
Causing stimulation of growth at mandibular condyle and remodeling at glenoid fossa
Condylar growth favorable (backward) or unfavorable (upward)
2- Maxillary inhibition:
Inter-maxillary force delivered by labial bow and sometimes by acrylic cap deliver orthopedic
force that inhibit downward and forward growth of maxilla this allow correction for class II
3- Posterior bite plate effect:
When large bite opening is used, inhibit the eruption of teeth that minimize the backward rotation
of mandible
The amount of positioning mandible in forward direction allow stretch of muscles that create
traction of mandible
Myodynamic: mandible postured 5 – 6mm opened 2 – 3mm beyond rest position
Myotonic: mandible postured or open vertically by greater amount more than Myodynamic
4- Guidance of eruption:
= By selective using of occlusal stops or facets in anterior or posterior segment that guide the teeth
to levelled and corrected its relationship
= using posterior bite blocks prevent continued eruption of posterior teeth while allowing incisors
for eruption
= to guide eruption and correct sagittal discrepancy, the upper molar should have occlusal stops
and not on lower molar because the upper molars tend to erupt in mesial and occlusal direction
but lower tend to erupt in vertical direction only, this allow correction of molar relationship
5- Stimulation of bone deposition in areas where the periosteum is stretched:
When using Frankel appliance, the buccal shields extended well into buccal sulci around point A
that lead to stretching periosteum and promotes bone deposition that allow relocation of muscle
attachment at that area.
6- Altering soft tissue forces:
Teeth in its position are in balance between the lips and tongue anteriorly and check and tongue
posteriorly
Cam change the effect of muscle from any side allow other change in the dental arches as:
- Eliminate the pressure from lips and check allow expansion of arches
- Eliminate the position of tongue from resting on the teeth that allow eruption
enhancement
- Anterior lingual shield prevent tongue to become in forward position in cases of
anterior open bite