Mode of action of functional appliances /certified fixed orthodontic courses by Indian dental academy

MODE OF ACTION OF
FUNCTIONAL APPLIANCES
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

www.indiandentalacademy.co
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Introduction:


Correction of malocclusion, primarily by
means of controlled movement of the
developing and mature dentition into a
desirable occlusal relationship



Control and modification of growth of
skeletal structures of the craniofacial
complex, especially via tooth borne
appliances
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Historical perspective:


Genetic control theory:
-inheritance and immutability of
normal and abnormal facial form
- genotype supplies all information
required for phenotypic expression

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Late 1890s: Wolff’s law and Roux
hypothesis:
changes in functional stress produced
changes in internal bone architecture and
external shape
 Early 1900s: Pierre Robin: monobloc
- passive positioning device
 Modified from bite jumping vulcanite
maxillary guide planes designed by
Norman Kingsley (1880)
 Vorbissplatte: Hotz


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Viggo Andresen : Activator
 Lischer’s theory:
If abnormal musculature can exacerbate
existing malocclusions, can not the same
muscles be used to correct these
problems?
 Andresen: modified Hawley type retainer
with lower lingual horse shoe flange
Significant sagittal basal bone and
neuromuscular improvement


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

Initially not accepted in US:
- facial growth could not be affected
- tooth position can be altered with
appropriate appliances and
biomechanics

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Theories of growth:


Genetic theory



Sutural growth theory: Sicher (1947):
growth at the sutures results in growth of
cranial vault and downward and forward
growth of the midface

Cartilage- directed growth theory:
Scott (1956): synchondroses, nasal septum
and mandibular condyle are centers of
growth


m

Theories of growth:
Functional matrix hypothesis:
Melvin Moss (1960)




Craniofacial skeleton develops initially and
grows in direct response to its extrinsic,
epigenetic environment



Functional matrix and skeletal unit



“ Bones do not grow, bones are grown.”
- Moss (1972)
m

Theories of growth:




Servosystem theory of craniofacial growth:
Alexandre Petrovic (1970s)
2 factors:
- hormonally regulated growth of the
midface and anterior cranial base, which
provides a constantly changing reference
input via the occlusion
- rate-limiting effect of growth of the
midface on the growth of the mandible
m

Activator:
Initial appliance: passive
 Loose appliance:Biting into the appliance
effected the extrinsic force; worn only at
night
 Andresen and Haupl:
altering skeletal relationship depending on
the direction and amount of jaw growth
incorporated in appliance ( Norwegian
system)


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Activator:







Activator: Andresen and Haupl
Sagittal positioning of the mandible
Elimination of abnormal musculature
Musculoskeletal adaptation by inducing a
new pattern of mandibular closure
Condylar adaptation: growth in upward
and backward direction to maintain
integrity of TMJ structures
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Activator:








Stimulation of myotactic reflex activity,
causing isometric muscle contractions
Loose fit of appliance with low vertical
dimension
Muscle force transmitted onto teeth: uses
kinetic energy
Increased activity of elevator and
protractor muscles with relaxing and
stretching of retractors
m

Activator:
Other views:
 Muscle contraction: superior head of
lateral pterygoid muscle
- Petrovic (rat studies), McNamara
(primate studies)
- variations in the mode and direction
of dislocation of mandible
 Condylar unloading: Lysle Johnston
m

Activator:
Viscoelastic activity:
Herren(1953), Woodside(1973),
Harvold(1974
 Viscoelastic reaction:
- emptying of vessels
- Pressing out of interstitial fluid
- Stretching of fibres
- Elastic deformation of bone
- Bioplastic adaptation


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Activator:








Herren: anterior crossbite relationship
Woodside: 10- 15 mm. Beyond postural
rest vertical dimension
Opening of 4-6 mm: Eschler(1952) no
overcompensation
Transitional type of activator action
Uses isometric and isotonic contractions
m

Activator:
Head posture during sleep:
Changes of head posture alter the
magnitude and direction of force
 Change in mandibular position varies
force vectors acting on mandible and
different muscle groups
 Plane of sleep( light or deep), intraoral air
pressure, dream cycle, state of mind also
affects activator response during sleep


m

Activator:


Skeletal effects:
- movement of condle in forward and
downward position due to the appliance
- adaptation to the new position through
condylar growth; growth in more
backward and upward direction
- adaptation to new position through fossa
remodeling
- more posterior orientation of trabaculae
m

Activator:


Dental effects:
- forward displacement of lower
anterior segment (Bjork,1969)
- bodily displacement of incisors
(Jacobsson, 1967)
- labial tipping of lower incisors
(Richardson,1982)
- lingual tipping (Moss, 1962)
m

Activator:


Types of force employed in activator
therapy:
- sagittal: mandible downward and forwardmuscle force to condyle and slight reciprocal
force to maxilla
- vertical: teeth and alveolar processes are
either loaded or relieved of normal forces ;
high construction bite inhibits growth,
direction and inclination of maxillary base
- transverse: incorporation of screws and
springs; midline correction
m

Bionator:
Balters (1943)
 Equilibrium between tongue and
circumoral muscles infleunces shape
of dental arches and intercuspation
 Tongue is the center of reflex
activity in the oral cavity


m

Bionator:
Position of the tongue:
posterior displacement: class II
low anterior displacement: class III
narrow arches and crowding: low
outward pressure
open bite: hyperactivity and forward
posture



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Bionator:


Forward posturing of mandible:
- enlargement of oral space
- dorsum of tongue contacting soft
palate
- accomplish lip closure

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Bionator:
Effects:
 Modulation of muscle activity of tongue
 elimination of abnormal influences of
perioral musculature
 Stimulation of myotactic muscle activity and
isotonic muscle contractions

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Bionator:
Effects:
 No vertical component except for guiding
eruption of teeth
 No viscoelastic response
 Prevention of deleterious parafunctional
activity at night : relaxation of lateral
pterygoid ( used for TMJ problems)

m

Frankel function regulator:
Frankel philosophy:
 Potential restraining influence of the
active muscle and tissue mass of the
buccinator mechanism and the
orbicularis oris complex
 Artificial matrix allowing the muscles
to exercise and adapt
m








Exercise device: stimulates normal function,
eliminating the lip trap, hyperactive
mentalis, aberrant orbicularis oris and
buccinator
Negative pressure of the muscles during
deglutition is prevented
Bodily buccal movement of posterior teeth
Oral gymnastics: lip seal exercises
m

Periosteal pull of buccal shields and lip
pads increases bone activity
 Stimulation of mid palatal suture
growth lesser extent increasing bone
apposition on the external
subperiosteal layer of maxilla
( Stutzmann et al 1983, Graber et al
1991)


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Dental effects:
 Appliance anchored to maxillary arch;
allows more downward and outward
movement of upper teeth
 Lower posterior teeth are allowed to
erupt upward and forward; sagittal
and vertical correction
m

Twin block:








Clark ,1977
Modification of occlusal inclined planes by
means of acrylic inclined planes on bite
blocks
Guide mandible downward and forward
Favorable proprioceptive contacts of inclined
planes
Adaptation of the muscles of mastication
Vertical and transverse control
m

Twin block:
Mode of action:
 McNamara(1980)
 Rapid neuromuscular response
 Gradual dentoalveolar response
 Pterygoid response: pain while
retracting the mandible
m

Twin block:
Proliferation of connective tissue and
blood vessels in the retrodiscal area
 Johnston( 1976) unloading of the
condyle
 Discomfort on removal of appliance
due to compression in the tension
zone behind the condyle


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Functional appliances and
extraoral force:





Class II div 1 with excessive vertical
growth
Unloading of the condyle by forward
posture of mandible
Retardation of horizontal and vertical
maxillary growth by headgear
Margolis ACCO(1976); Jacobsson splint
(1967); Stockli and Teuscher activatorheadgear combination
m

Fixed functional appliances:
Herbst, 1909- Scharnier
 Mandible was kept forward
continuously, eliminating the need
for patient compliance
 Herbst and Schwartz, 1934
 Pancherz, 1979


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Sagittal changes:
 Restraint of maxillary growth: headgear
like effect
 Stimulation of mandibular growth:
- remodeling on lower border of
mandible(Pancherz and Ruf,1997)
- modification of TMJ fossa( Paulsen,1997;
Buschang,1998)
- ultimate condylar position in fossa is
unaffected
m

Sagittal changes:
 Proclination of lower incisors
 Posterior movement of upper
molars: headgear like effect

m

Vertical changes:
 Eruption of lower molars; intrusion
of lower incisors: reduction of
overbite
 Proclination of lower incisors
contributing to overbite reduction

m

Long term changes:
 Class I relationship is maintained with
stable cuspal interdigitation
 Causes of relapse:
- too early treatment
- mixed dentition treatment
- persistent abnormal musculature
- unstable post treatment occlusion
- insufficient length of appliance wear and
retention
m

Soft tissue changes:
 Reduction of soft tissue convexity,
excluding the nose
 Increase in soft tissue convexity,
including the nose, because of normal
nasal growth
 Retrusion of upper and lower lips in
relation to esthetic line due to normal chin
and nose growth
m

Jasper jumper:
 James Jasper, 1987
 Effects:
- functional effect similar to Herbst
appliance
- dentoalveolar changes
m

Repositioning effect:
 Farrar effect: reciprocal clicking
 Recapturing of the disc
 Repositioning of condyle
 Maintaining the repositioning effect
 Orthodontic occlusal correction in
the desired position


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Mode of action:
Condylar growth:
 Forward positioning of mandible
 Increased activity of LPM
 Intensification of repetitive activity
of retrodiscal pad

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Mode of action:


1.
2.

-

Condylar growth:
increase in growth stimulating factors:
enhancement of local mediators
Reduction of local regulators
change in condylar trabacular orientation
additional growth of condylar cartilage
additional subperiosteal ossification of
posterior border of mandible
lengthening of mandible
m

Mode of action:


1.

Increased activity of LPM
Retrodiscal pad- mediator of response
Blood circulating effect:
- increase in blood and lymph flow,
- increase in nutritive and growth
stimulating factor supply
( STH-somatomedin, testosterone and
estrogen in low doses, insulin,
prostaglandin F2, mitogenic peptides)
m

Mode of action:
- decrease in locally produced
catabolites and other negative
feedback factors
( prechondroblast’s multiplication
restraining signal, cAMP,
prostaglandin E2, somatostatin-like
substance)
- iterative action
m

Mode of action:
2. Biomechanic effect:
- Accentuated concavity at the posterior
border of mandibular ramus due to
increase in condylar growth and more
posterior directed growth
- piezoelectric effect: increase in negative
charges along posterior border, causing
increased periosteal bone formation and
vice versa
- supplementary lengthening of mandible
m

Herren and LSU activator:
 Bite opened well beyond postural rest
position
 Forward positioning of mandible leads to
reduced increase in length of LPM
 Sensory engram formed for new position of
mandible
 Functioning of mandible in more forward
position when appliance is not worn
 Increased activity of retrodiscal pad with
acceleration of condylar growth
m

Growth restriction of glenoid fossa:
normal growth of glenoid fossa is in
posterior and inferior direction
Anterior slope of articular eminence
undergoes bone deposition on posterior
slope and resorption on anterior slope
Anterior relocation of glenoid fossa in
orthopedic treatment
Reciprocal forces from viscoelastic tissue
between condyle and fossa


m

Growth relativity hypothesis:
Voudoris, Kuftinec AJODO March 2002

Mandibular advancement

Fibrocartilagenous lining in glenoid fossa
induces bone formation locally

Stretch of nonmuscular viscoelastic
tissues

New bone formation some distance from
the actual retrodiscal attachments in the
fossa
m


Fibrocartilage caps the condyle in 3
dimensions: posterior, anterior and 2
collateral along with fibrous capsule and
synovial fluid

Advancement: engorgement of blood
vessels, influx of nutrients and
biodynamic factors

Reseating of condyle in fossa: expulsion
of these factors

Resulting metabolic pump-like action
m


Disoccluding appliances cause low intraarticular subatmospheric pressures within
TMJ in open position ( Nitzan, 1994)

Shift of synovial fluid perfusion on a
posteriorly displaced direction

Negative pressures are below capillary
perfusion pressure

Greater flow of blood to the region
m

Bone architecture is influenced by the
neuromusculature and the
contiguous nonmuscular, viscoelastic
tissues anchored to the glenoid fossa
and the altered dynamics of the
fluids enveloping bone
m

Displacement+ viscosity+
referred force

1.
2.
3.

Three growth stimuli:
Anterior orthopedic displacement
Posterior viscoelastic tissues between
condyle and fossa
Transduction of forces over the
fibrocartilage cap of the condylar head,
increases radiating endochondral bone
formation beneath condylar fibrocartilage
and periosteal bone formation in the fossa
m

Condylar light bulb analogy:
Condyle acts like a light bulb on a
dimmer switch
 Lights up during advancement,
dimming back to near normal levels
during retention
 Growth potential diminishes with
age while remodeling potential last
long into adulthood


m

Clinical implications:
Prevention of condylar compression
by using Herbst with thin posterior
bite blocks
 Rapid maxillary expander to reduce
occlusal interferences and functional
shifts due to the anterior positioned
mandible


m

Studies on functional
appliances:
Activator:
 Charlier et al 1968, 1969, Petrovic et al
1975: Distribution of dividing cells in
sagittal section of condylar cartilage of
juvenile rats
 Histologic and radiographic study
 Results: Treatment with both postural
hyperpropulsor and and growth hormone
STH produced increase in growth rate of
condylar cartilage as compared to
controls
m

appliances:
Activator:
 Location of increase of dividing cells:
- more posterior in hyperpropulsor
- more anterior in STH

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Histologic

study:

- growth of bony trabaculae formed in
parallel and posteriorly oriented condylar
cartilage

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appliances:
Activator:
 Petrovic and Stutzmann (1977), rat
experiment
 Administration of growth hormone and
treatment by postural hyperpropulsor:
- increase in condylar cartilage growth
rate
- hyperpropulsor: opening of Stutzmann
angle
- growth hormone: closing of Stutzmann
angle
m

appliances:
Activator:
- lengthening of mandible measured from
posterior edge of condylar cartilage to
mental foramen is greater in case of
opening of angle
 Administration of testosterone:
male rats for 3 weeks; stimulation in
growth rate of condylar cartilage and
(Stutzmann 1976, Petrovic, Stutzmann
1977, 1978) www.indiandentalacademy.co
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appliances:
Activator:
 Resection of lateral pterygoid muscle:
decrease in condylar growth rate and
( Petrovic, Stutzmann 1972, 1974);
opening of Stutzmann angle
 Effect of postural hyperpropulsor:
greater the sagittal advancement, greater
the condylar cartilage growth rate and
mandibular lengthening, opening of
angle; decreases with time
m

appliances:
Activator:
 Growth rotation and alveolar bone
turnover of mandible:
high alveolar turnover rate with
anterior growth rotation than
posterior rotation

m

appliances:


Woodside et al 1975:
- effect of activator treatment applied
during the evening and night on
mandibular length
- periods of treatment were not coincident
with mandibular growth accelerations
(except in 1 case)
- therefore, treatment with functional
appliances should be started coincident
with naturally occurring mandibular
growth accelerations
m

appliances:


Altuna, Woodside 1977, 1985:
- primate experiments using juvenile and
adult animals in which mandible was
opened 2, 4, 8, 12 mm. Without sagittal
advancement
- openings greater than 2mm resulted in
increased mandibular length due to
changes in condylar stress

m

appliances:


Woodside 1985: EMG activity in LPM
by Frankel functional regulator and
activator
- both appliances generated similar
amounts of LPM activity after initial
appliance insertion

m

appliances:





Woodside et al 1987: assessment of
remodeling changes in the glenoid fossa using
juvenile monkeys
- Herbst appliance with progressive
activations used
- extensive remodeling and anterior
relocation of glenoid fossa seen
Voudoris 1988: same changes
Angelopoulos 1991: changes in glenoid fossa
remodeling are stable
m

appliances:


Sessle et al 1990: longitudinal effect of
functional appliances on jaw muscle activity
using 6 female monkeys
- pre appliance and post appliance levels
compared with controls
- Herbst and functional protrusive appliances
inserted
- decreased activity in superior and inferior
head of LPM, superficial masseter, anterior
digastric; persisted for 6 weeks returning to
previous levels after 6 week observation
period
m

appliances:


McNamara 1972, 1973: cephalometric,
electromyographic and histologic study
of altered functional position of lower
jaw in monkeys
- increased activity of superficial head of
masseter, decreases activity of
posterior part of temporal muscle,
increased activity of superior head of
LPM
m

appliances:


Elgoyhen, McNamara et al, 1972:
advancement of mandible of 6 juvenile
monkeys for 5 months
- significant increase in rate of growth of
condyle
- rate increased with increased time of
appliance wear; within 3 months with peak in
2 months; reduction in 4 months

m

appliances:


McNamara 1973, 1974: vertical dimension
was increased by using cast gold inlays
opening bite from 2 to 15 mm in incisor
region in monkeys
- contraction of superior head of LPM
- elongation of elevator muscles
- gradual change
- inhibition of normal downward and forward
growth of maxilla
m

appliances:
Taken from the AJO-DO 1982 Oct (288-298):
- McNamara, Hinton and Hoffman
 Histologic analysis of temporomandibular
joint adaptation to protrusive function in
young adult rhesus monkeys (Macaca
mulatta)
- twelve young adult female rhesus monkeys
were fitted with functional protrusive
appliances for periods ranging from 2 to 24
weeks.


m

appliances:
- a proliferative chondrogenic response
accompanied by deposition of new bony
trabeculae at the bone-cartilage
interface, though greatly reduced in
magnitude as compared to juvenile
monkeys

m

appliances:


Taken from the AJO-DO 1987 Mar (213-224):
- DeVincenzo, Huffer, and Winn
- A study in human subjects using a new
device designed to mimic the protrusive
functional appliances used previously in
monkeys
- maxillary and mandibular posterior
biteplates separated by a sharp vertical
interface perpendicular to the occlusal plane

m

appliances:


-The rate of mandibular length
increase in the treatment group over
that of controls was comparable to
values reported in monkeys. Other
skeletal and dentoalveolar changes
were likewise similar to those found in
monkeys.

m

appliances:
Bionator:
 Taken from the AJO-DO 1990 Feb (113-120):
Mandibular response to orthodontic treatment
with the Bionator appliance - Mamandras and
Allen
- A group of 20 subjects who underwent
successful Bionator treatment was compared
with 20 subjects who were treated less
successfully with the same appliance. Both
groups had similar advancements in their bite
registrations, as well as similar treatment
times and growth-prediction parameters
m

appliances:
Bionator:
- both the total mandibular length and the
horizontal mandibular dimensions in the
large-advancement group was greater than
that in the small-advancement group. Only
the vertical mandibular dimension remained
slightly, but not significantly, reduced when
compared with the small-advancement group
- more distal posttreatment condylar position
in the large-advancement group as compared
with the small-advancement group
m

appliances:
Frankel appliance:
 Taken from the AJO-DO 1989 Oct (333341): - Falck and Fränkel
 Clinical relevance of step-by-step
mandibular advancement in the
treatment of mandibular retrusion using
the Fränkel appliance
 120 pts: 60 with end on relationship,
60 with step wise advancement
m

appliances:
Frankel appliance:
- better sagittal correction with gr. B
- opening of mandibular plane angle in gr. A
- more dentoalveolar changes with gr.A
- condyle in more anterior position in gr. A
- gr. A had better restraining effect on
maxilla (point A and maxillary molar)

m

appliances:
Taken from the AJO-DO 1982 Jul (1022): Arch width development in Class II
patients treated with Fränkel appliance
- McDougall, McNamara, and Dierkes
 60 treated with FR 1 and 2 and 47
untreated cases
 changes in lingual, buccal, and alveolar
arch widths were compared.


m

appliances:
expansion of the maxillary and
mandibular dental arches and their
supporting structure occurs routinely
with a functional regulator (FR-1 or FR2)
 largest expansion in the premolar and
molar regions, lesser in the canine
region; in the maxilla narrower arches
tend to expand more than wider arches


m

appliances:
Taken from the AJO-DO 1990 Aug (134-144):
Comparison of Herbst and Frankel appliances
- McNamara, Howe, and Dischinger
 A comparison of the Herbst and Fränkel
appliances in the treatment of Class II
malocclusion
- 45 pts with acrylic splint Herbst and 41 pts
with FR2
- cephs compared with 21 untreated class II
pts


m

appliances:
- Significant skeletal changes were noted in
both treatment groups, with both groups
showing an increase in mandibular length and
in lower facial height, as compared with
controls.
- Greater dentoalveolar treatment effects
were noted in the group wearing the toothborne functional appliance than in those
wearing the tissue-borne appliance.
m

Proffit, Tulloch AJODO,June
2002
Optimal timing of treatment for Class II
malocclusion
 - can jaw growth really be modified, by
how much, with what predictability, in
which patients?
- do different appliances produce different
effects?
- would early intervention make later
treatment simpler and with better
treatment results?


m

2002

Methods:

Children with overjet> 7mm, in mixed
dentition, at least 1 yr before peak height
velocity, excluding children with extreme
vertical disproportions

2 phases:
1.
- Treatment with either a combination
headgear or functional appliance
- Control with no treatment until
permanent dentition
2. All children were treated with fixed
appliances
m

2002
Methods:
 Boys- 57.8%, girls- 42.2%
 Mean age- 9.4 yrs
 Mean overjet- 8.4 mm, 91%
bilateral class II
 175 children, 166 completed phase
1, 143 started and completed
phase 2
m

2002
Results:

Small mean reduction in jaw relationship
with early treatment

Mechanism of change:
- headgear group: restriction in fwd
movement of maxilla
- functional appliance: increase in
mandibular length and increase in chin
projection

75% of early treatment pts had highly
favourable changes as compared to 25%
of untreated pts
m

2002
Second phase:
 Clinician centered outcome:
change in skeletal jaw relationship
or alignment and occlusion of teeth
 Patient or parent oriented
outcome: duration of treatment or
need for extractions or other
surgical procedures
m

2002






2 early treatment groups : reduction in
ANB angle in phase 1, no sustained
advantage in phase 2
No difference in patients with convex
profiles
No difference in quality of occlusion
Early treatment did not reduce the
percentage of children needing
extractions in phase 2 or eventual
orthognathic surgery
m

2002
Treatment time:
 length of time in phase 2, and
time spent wearing fixed appliances
 Early treatment had very little
effect in reducing the time of fixed
treatment

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2002
Discussion:
 Early treatment produced an initial
differential growth change
 Not effective in correcting later
skeletal and dental class II
malocclusion
 No advantage in final treatment
outcome or simplification of later
treatment procedures
m

2002
Early treatment:

Psychological distress

Accident prone children

Skeletal maturity is ahead of dental
development

Children with vertical and class II
problems
Conclusion: no clear advantage for early
treatment
m

Thank you
For more details please visit
www.indiandentalacademy.com

m

Mode of action of functional appliances /certified fixed orthodontic courses by Indian dental academy

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