Fixed functional appliiances /certified fixed orthodontic courses by Indian dental academy

Fixed functional
appliances

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CONTENTS
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Introduction
Historical back ground
Classification
Flexible fixed functional appliances(FFFA)
Rigid fixed functional appliances(RFFA)
Hybrid appliances
Mode of action-theories on condylar growth
Skeletal effects of bite jumping
Treatment timing and outcome
Conclusion
References

INTRODUCTION
• Functional appliances are considered to be
primarily orthopedic tools to influence the
facial skeleton of the growing child in the
condylar and sutural areas.
• A functional appliance by definition is an
appliance that produces all or part of its effect
by altering the position of the mandible.


• These appliances also exert orthodontic
effects on the dentoalveolar area. The
uniqueness lies in their mode of force
application.
•
Functional orthopedic treatment seeks
to correct malocclusions and harmonize
the shape of the dental arch and oro-facial
functions.


Removable functional appliances have been used
over the years and are clinically accepted.
But they have some disadvantages:
•normally very large in size,
•have unstable fixation,
•cause discomfort,
•lack tactile sensibility,
•exert pressure on the mucous
• reduce space for the tongue, cause difficulties in
deglutition and speech often affect aesthetic
appearance.
• alteration in the mandibular posture creates added
difficulties.

Fixed functional appliances have some advantages over
removable systems:
• They are designed to be used 24 hour a day
• They are smaller in size, permitting better adaptation to
functions
• Reduce the need for patient compliance
• As they are fixed on the upper &lower arches, transmit
force directly to the teeth through support system


HISTORICAL BACK GROUND
Fixed functional appliances first appeared in 1900’s
when Emil Herbst presented his system at the Berlin
international dental congress.
• Since then and up to the seventies, very little was
published on this appliance. It was at that time that
Hans Pancherz brought the subject back into
discussion with the publication of several articles on
the Herbst.
• A number of fixed appliances have gained popularity
in recent years to help achieve better results in noncompliant patients.

• Originally, the telescoping parts of the Herbst
appliance were curved conforming to the curve of
spee.
• Until 1934, Herbst made the telescopes of German
silver.
• In 1910, telescopic mechanism was placed upside
down and anchorage system consisted of crowns on
upper molars and lower first bicuspids.


Original Herbst appliance


Original curved Herbst
telescopes
• The telescoping parts
were curved
conforming to the
curve of spee


Standard anchorage system of
Herbst
• Crowns on upper first
molars and lower first
bicuspids
• crowns joined by
wires along palatal
surfaces
• Anchorage forms
used from 1909 to
1934

Anchorage forms from 1979
onwards
• Pancherz used a banded type of Herbst
appliance
• Bands placed on upper first molars and
premolars connected by sectional arch
wires
• Bands placed on lower first premolars
connected by a lingual arch wire


CLASSIFICATION
Fixed functional appliances can be
classified as:
• Flexible
• Rigid
• hybrid


FLEXIBLE
JASPER JUMPER
AMORIC TORSION COILS
ADJUSTABLE BITE CORRECTOR
SCANDEE TUBULAR JUMPER
KLAPPER SUPER SPRING
THE BITE FIXER
CHURRO JUMPER


RIGID
HERBST APPLIANCE
CANTILEVERED BITE JUMPER
MALU HERBST APPLIANCE
VENTRAL TELESCOPE
MANDIBULAR PROTRACTION APPLIANCE
MAGNETIC TELESCOPIC DEVICE
BIOPEDIC APPLIANCE
MARA
IST APPLIANCE


HYBRID
CALIBRATED FORCE MODULE
EUREKA SPRING
TWIN FORCE BITE CORRECTOR
FORSUS
ALPERN CLASS II CLOSERS


FLEXIBLE FIXED
FUNCTIONAL
APPLIANCES

FLEXIBLE FIXED FUNCTIONAL
APPLIANCES(FFFA)
• Flexible fixed functional appliances (FFFA) can be
described as an inter-maxillary torsion coils, or fixed
springs.
• Elasticity and flexibility are the main characteristics
of flexible appliances.
• They allow great freedom of movement of the
mandible.
• Lateral movements can be carried out with ease.


Drawbacks are:
• Fractures can occur both in the appliance itself
and in the support system,
• Tendency to produce fatigue in the springs,
• Tendency of the patient to chew on the appliance,
• Wide mouth opening is not possible,
• Curvature of springs accentuates the
protuberance of cheeks- unaesthetic.


• The intention when they first appeared was for the
treatment of Class II, both in malocclusions
characterized by a mandibular deficiency as well as in
cases where a dental problem predominated.
• Later on, their application extended to Class I problems
especially when treatment including extraction was
foreseen.
• The appliance was used as an anchorage
reinforcement or even for molar distalization.
• The appliance is also used in a reverse type for
treatment of Class III malocclusions, as well as in cases
of midline discrepancy.


• The type of the force exercised by FFFAs is continuous
and elastic in nature. The amount of force is variable in
accordance with the skeletal pattern of the patient, the
type of movement desired and the size of the cusps.
• FFFA produces a "headgear" effect on the maxillary
dentition due to the intrusive force applied to the
maxillary posterior segments and produces an anterior
intrusive force on the lower dentition
• It can be used to obtain maximum anchorage, holding
upper molars back as the upper incisors are retracted


Problems encountered
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Posterior open bite
Posterior cross bite
Proclination of lower incisors
Not recommended in mixed dentition


JASPER JUMPER
• Jasper jumper was the first
flexible functional
appliance.
• Introduced in 1987 by
Jasper JJ.
• Advantage : can be added
to existing appliance at
any point of time after
initial arch alignment is
completed.
• System is composed of
two parts:
• force module
• anchor units

• When the force module is straight it remains passive.
• When it is curved the muscles of mastication try to
elevate producing a force of 1 to 16 ounces.
• This kinetic energy potential energy to be used for
clinical effects.
• Types of forces produced:
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sagittal
intrusive
Head gear effect
Retraction of anterior teeth
Dental asymmetries
Mandibular advancement


THE AMORIC TORSION COILS
• This appliance is made up of two springs, one of which slides
inside the other.
• They are intermaxillary springs without covering and have a
simplified application system of rings on the ends.
• These rings are fixed to the upper and lower arches with double
ligatures.
• The force exerted by the appliance is variable in accordance with the
fixing points on the arch


THE ADJUSTABLE BITE
CORRECTOR (ABC)
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It is assembled by the orthodontist
as it is composed of various pieces
– caps, closed coil springs, nickel
titanium wire.
It can be used on either side of the
mouth with a simple 180º rotation of
the lower end cap to change its
orientation.
In the center lumen of the spring a
nickel titanium wire which is
responsible for the "push" force
generated.

THE SCANDEE TUBULAR
JUMPER
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This is a coated intermaxillary
torsion spring sold in a kit which
includes the spring, the covering,
the connectors, the ballpins and
the glue.
There is no distinction between left
and right.
The orthodontist constructs the
appliance, cutting the spring to the
length seeing fit.


THE KLAPPER SUPER SPRING
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Flexible spring element which is attached
between the maxillary molar and the mandibular
canine .
• The length of the element causes it to rest in the
vestibule when activated. This facilitates hygiene
and avoids occlusal surfaces.
The ends (fixing points) are different:
• The open helical loop of the spring is twisted
like a J-hook onto the mandibular archwire.
• On the maxillary end it is attached to the
standard headgear tube (Super Spring I)
or to a special oval tube and secured with a
stainless steel ligature (Super Spring II).
• This new version prevents any lateral
movement of the spring in the vestibule.


THE BITE FIXER
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This is a new intermaxillary spring
coil.
The spring is attached and
crimped to the end fitting to
prevent breakage between the
spring and the end fitting.
Polyurethane tubing is inside the
spring to prevent it from becoming
a food


THE CHURRO JUMPER
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This is an inexpensive alternative
force system for the
anteroposterior correction of Class
II and Class III malocclusions.
The mesial and distal end of the
jumper are circles.
The distal circle is attached to the
maxillary molars by a pin and the
mesial end is placed over the
mandibular archwire against the
canine bracket.
This is the only flexible functional
appliance which can be made up
by the orthodontist in his lab.
The costs are reduced and the
time spent is minimal


RIGID FIXED FUNCTIONAL
APPLIANCES


RIGID FIXED FUNCTIONAL
APPLIANCES
• These appliances have two distinct differences in
relation to FFFAs:
• RFFAs do not easily fracture but neither do they have
elasticity or flexibility.
• After fitting and activation they do not allow the patient to
close in centric relation. This means that the mandible is
in a forward position 24 hours a day creating greater
stimulus for mandibular growth than with FFFAs
• The working is based on telescopic mechanism which
encourages forward re positioning of the lower jaw as
the patient in to occlusion.


HERBST APPLIANCE
• The Herbst appliance was first
described by Emil Herbst in
1905 at the Berlin Dental
Congress. After that very little
was written on this appliance
until the end of the seventies
when Hans Pancherz brought it
back into discussion with the
publication of a series of
articles.
• The Herbst appliance consists
of two tubes, two plungers,
axles and screws.

The original device is a banded Herbst design.
The Herbst appliance has undergone some changes
in its original design but since the seventies has
maintained its general shape with only a few
modifications taking place with regard to methods
of application (Type I, II and IV).
Type I
Type II
Type IV


HERBST TYPE I
• Type I is characterized by
a fixing system to the
crowns or bands through
the use of screws.
• This is the most common
form.
• Necessary to weld the
axles to the bands or
crowns and then fix the
tubes and plungers with
the screws

HERBST TYPE II
Fixing system - directly
onto the archwires
through the use of
screws.
• Disadvantage:causes
constant fractures in the
archwires.
• The lack of flexibility
together with the difficulty
in lateral movements and
the stress placed on the
archwires -causes
fractures, especially in
the lower arch
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HERBST TYPE IV
Fixation system- ball
attachment, allows
greater flexibility and
freedom of mandibular
movement.
• disadvantage: needs
brakes to stabilize the
joint.
• The brakes are small and
sometime difficult to fit.
• When a fracture occurs
or a brake is lost, the
appliance comes loose
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HERBST APPLIANCE DESIGN
• Banded herbst design
• Stainless steel crown
• Acrylic splint design


BANDED HERBST DESIGN
• The current version incorporates additional anchorage
units of original design of Pancherz.
• Bands on all first premolars and first molars.
• Buccal and lingual wires connect these.
• 0.040 or 0.051” wire form support wire , soldered on
both sides


STAINLESS STEEL CROWN
HERBST DESIGN
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Original design has SS crowns on upper first molars to which
pivots are soldered tom secure maxillary tubes.

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Transpalatal arch or hyrax is placed to increase the rigidity

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Type I design of Smith- bands on lower I molars that connect
SS crowns to each other by 0.045” SS lingual wire.

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Type II design of Smith- cantilever herbst. Hs mandibular
extension arms that are anchored to SS crowns on the lower I
molars.

ACRYLIC SPLINT HERBST
• Has a wire frame work on which 2.5 to 3 mm Biocryl
is adapted.
• Splint can be : bonded or removable
• Removable- from canine to I molar.
• Boded- labial surfaces of canine not covered with
acrylic.


REVIEW ABOUT
HERBST APPLIANCE


The mechanism of class II correction in herbst
appliance treatment – A Cephalometric investigation
Hans Pancherz – AJO 1982
• Sagittal skeletal and dental changes contributing to class
II correction in Herbst treatment were evaluated
quantitatively on lateral roentgenograms.
• Study consisted of 42 cases, 22 treated with Herbst
appliance for 6 months and others served as controls.
• Results : 1) Bite jumping with the herbst appliance
resulted in class I occlusal relationships in all treated
cases.
• 2) The improvement in occlusal relationships was about
equally a result of skeletal and dental changes.


•3) Class II molar correction was mainly the result of
an increase in mandibular length, distal movement
of the upper molars, and mesial movement of the
lower molars.
•4) Over jet correction was mainly the result of an
increase in mandibular length and mesial movement
of the lower incisor.
•5) The restraining effect of treatment on maxillary
growth, distal movement of maxillary incisors, and
anterior condylar displacement was of minor
importance for the improvement in occlusal
relationship seen.
•6) A direct relationship existed between the amount
of bite jumping at the start of treatment and the
treatment effects on occlusion and on mandibular
growth.

BSSO Vs. Herbst – Ruf and Pancherz
AJO Aug’04
Study assessed the extent of adult Herbst treatment
as an alternative to orthognathic surgery by comparing
the dento-skeletal treatment effects.
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In surgical group the improvement in sagittal
occlusion was achieved by skeletal more than dental
changes, in the Herbst group, the opposite was the case.
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The success and predictability of Herbst treatment
for occlusal correction was as high as surgery.
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Herbst treatment can be considered an alternative
to orthognathic surgery in border like adult class II MO,
especially when a great facial improvement is not the
treatment goal.
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Cephalometric comparison of treatment with Twin Block and SS Crown
Herbst application followed by fixed application therapy. (AJO July 2004)

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Study compared the effects of two treatment protocols for correcting
class II disharmony.
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Very similar therapeutic modifications were produced though
twin block group exhibited almost 2 mm greater correction of the
maxillo-mandibular differential than did the crown Herbst group.
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The treatment effects of both protocols led to a normalization
of dentoskeletal parameters at the end of overall treatment period.
• Over all, only minor differences were detected in the treatment and
post treatment effects of compliance-free (crown Herbst) and non
compliance-free application for correcting class II disharmony


TMJ growth changes in hyper- and hypo- divergent Herbst
subjects. Pancherz AJO August 2004
• Long term study assessed the amount and direction of
glenoid fossa displacement, condylar growth and
“effective” TMJ changes =
sum of glenoid fossa displacement, condylar growth
and condylar position changes in fossa) in 3 vertical
facial types group class II div 1 treated with Herbst.
• The amount and direction of TMJ growth changes were
only temporarily affected favorably in the sagittal
direction of Herbst treatment.
• For glenoid fossa displacement changes, no differences
existed between hyper and hypo subjects at examination
period.

Effectiveness of treatment of class II MO
with the Herbst or Twin Block appliances
AJO 2004 Kevin o’ Brien et al
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Study evaluated the effectiveness of Herbst and Twin
– block appliances for established class II div 1
malocclusion.
• A total of 215 patients were randomized to receive
treatment with either the Herbst or the twin block
appliance.
Study concluded that :
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Patient cooperation with the Herbst application better
than that with the twin block.
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Phase I treatment is more rapid with the Herbst
application, but overall duration of treatment is similar to
that with the twin block.

• The Herbst application is prone to debonding
and component breakage.
• There are no differences in the dental and
skeletal effects of treatment between the 2
appliances.
• Marked sex effect -girls responded treatment
better than boys.


Treatment and post- treatment effects of acrylic
splint herbst appliance therapy AJO 1999 lorenzo
Franchi and Mc Namara
Evaluated the skeletal and dentoalveolar changes
induced by acrylic splint Herbst therapy of 55 subjects
with class II MO treated with Herbst followed by
comprehensive edgewise therapy.
•
Treatment effects were mostly skeletal in nature
and are due to changes in mandibular sagittal position
and in mandibular dimension.
• An important component in molar relationship and
overjet correction was the mesial most of mandibular
dental arch.
• The amount of relapse during post treatment period is
ascribed mainly to mesial involvement of maxillary
molars.
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Step wise advancement using fixed
functional appliances Rabie et.al Semi.
Orthod 2003

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Studied the pattern of bone formation in the TMJ in response to the
step wise advancement compared to single step advancement with
FFA’s.
250, 35-day old female spraue-dawley rats were randomized in to
20 experimental and 10 control groups.
Results: during the first advancement, bone formation in the condyle
and glenoid fossa was less than that of one-step advancement.
In response to second advancement, new bone formation was
significantly higher than with single advancement.
Concluded : step wise advancement produced more skeletal effects
than single advancement.
More prominent effect seen with step wise advancement in glenoid
fossa.

CANTILEVER BITE JUMPER
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It is a Herbst style appliance
fitted directly to the lower
molar bands through a
cantilever arm.
Crowns have to be fitted to
the upper and lower molars.
Disadvantage -thickness of
the screw mechanism can
impinge on the patient’s cheek
The parts are available in kit
form with pre-welded screw
mechanisms and cantilever
arms on crowns of seven
different sizes.


MALU HERBST APPLIANCE
• It consists of two tubes, two
plungers, two upper
"Mobee" hinges with ball
pins and two lower key
hinges with brass pins.
• Advantages -lower cost, no
laboratory needed,
flexibility and the possibility
of using combined with
edgewise therapy


•Each upper Mobee hinge is inserted into the hole
at the end of the MALU tube and secured to the first
molar headgear tube with ball pin.
•Each lower key hinge is inserted into the hole at
the end of the plunger and locked to the base arch,
distal to the cuspid, with the brass pin.


FLIP- LOCK HERBST APPLIANCE
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This is the third generation of
ball-joint Herbst appliances
available from this company.
The first generation was made
from a dense polysulfone
plastic but breakage occurred
because of the forces
generated within the ball-joint
attachment.
The second generationplastic replaced with metal.
Advantage: thin and small.


THE MANDIBULAR
PROTRACTION APPLIANCE
• Filho developed in 1995
• Advantages- ease of
manufacture, low cost,
infrequent breakage,
patient comfort and rapid
fitting.
• can be made up
orthodontist


THE VENTERAL TELESCOPE

• This was the first telescopic RFFA that
appeared as a single unit; i.e. upon reaching
maximum opening it does not come apart
• Available in two sizes and fixing is achieved
• through ball attachments.
• easy to activate-unscrewing the tube allows
activation of around 3 mm.


•Disadvantages quite thick , suffers from
•fractures to the brake which stabilizes the joint.
•Great accuracy is necessary with inclination and
the welding of components


THE MAGNETIC TELESCOPIC
DEVICE

• Consists of two tubes and two plungers with a semicircular section and with NdFeB magnets placed in such a
manner that a repelling force is exerted. Fitting is
achieved by using the MALU system.
• Advantage: linking a magnetic field to the functional
appliance.
• Disadvantages: thickness, the laboratory work necessary
to prepare it and the covering of the magnets

THREE TYPES OF
APPLIANCE
MPA I
MPA II
MPAIII


MPA I
• MPA I – each side made by bending a small loop at a
right angle to the end of an .032" SS wire.
• The length of the appliance is determined by protruding
the mandible and another small right-angle circle is then
bent in an opposite direction.
• The appliance slides distally along the mandibular arch
wire and mesially along the maxillary arch wire.
• Bicuspid brackets must be debonded.
• Limited mouth opening is the major disadvantage.


MPA II
• MPA II – made by making right-angles circles in two
pieces of .032" SS wire.
• A small piece of slipped coil is slipped over one of the
wires.
• One end of each wire is then inserted through the loop
in the other wire.
• This version allows the mouth to open wider than the first
version.


MPA III
• MPA III – eliminates much of the arch wire stress that
occurs with the MPA I and II.
• It permits a greater range of jaw movement while
keeping the mandible in a protruded position.
• It is adaptable to either Class II or Class III
malocclusions.


UNIVERSAL BITE JUMPER

• Its like a Herbst but is smaller in size and more
versatile
• It can be used in all phases of treatment in mixed or
permanent dentition, Class II or III malocclusions
• It is fitted in the patient’s mouth and cut to the
appropriate length for the desired mandibular
advancement.
• Activations are made by crimping 2-4 mm splint
bushings onto the rods. UBJs with nickel titanium coil
springs do not need to be reactivated.

THE BIOPEDIC APPLIANCE
• Engaged on the maxillary
and mandibular molars,
using a cantilever like
system, then attached to
a BioPedic buccal tube.
• Activation by sliding the
appliance along the
buccal tube and fixing the
screw.
• Universally sized for left
and right sides.
• Two pivots on the ends
allow the appliance.


THE MANDIBULAR ANTERIOR
REPOSITIONING APPLIANCE(MARA)
• Created by Douglas Toll
of Germany in 1991.
• It consists of cams on the
molars which is guided
the patient to bite into
class I
• Indication: skeletal class
II with mandibular
deficiency
• Contra indications:
dolicofacial, root
resorption, dental and
skeletal open bites, high
mandibular plane angle

IST -APPLIANCE
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The Intraoral Snoring-Therapy
Appliance is a new device
designed by Hinz, to treat
patients who suffer from
breathing problems during
sleep.
Suppresses snoring by moving
the lower jaw forward reducing
the obstruction in the
pharyngeal area
Advantage:orthodontist can
change the protrusion on each
side up to 8 mm
An end stop in the guiding
sleeve prevents the telescope
from disengaging

THE RITTO APPLIANCE
• Ritto A K in 1998
• Miniaturized telescopic
device with simplified
intra oral application and
activation
• Initial wear of splint with
bite block for 15 days to
1 month
• There is posterior contact
after advancement of
mandible


Hybrid fixed functional
appliances


HYBRID APPLIANCES
• They classified as hybrid appliances because they
represent the combination of a rigid fixed functional
appliance (RFFA) with flexible fixed functional appliance
(FFFA).
• They could be described as rigid appliances with coil
spring-type systems.
• Objective is to move the teeth by applying 24-hour
elastic continuous force that would replace the traditional
use of elastics and extra-oral force.


•Common feature- use of coiled springs to produce
force. The force generated varies between 150 and 200
gm.
• Advantages -reduction in the need for patient
cooperation and the ease of placement.


THE CALIBRATED FORCE
MODULE
Fixed appliance
designed to substitute
Class II elastics
• Developed in 1988 by
the CorMar Inc.
• Applied to the inferior
arch close to the molars
and fixed by a screw, and
mesial or distal to upper
cuspids, and also fixed to
the arch.
• Its coil spring produced a
force between 150 and
200 gm
•


EUREKA SPRING
• Developed by DeVicenzo
and Steve Prins.
• It is a three part
telescopic appliance fixed
to the upper arch at the
level of the molar band
and to the lower arch
distal to the cuspid.
• The appliance has an
open coil spring that is
placed inside of a part of
the system.
• The placement is simple

THE TWIN FORCE BITE
CORRECTOR
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Consists of two joint
telescopic systems and
two internal coil springs.
At the superior level, fixed
with a ball pin that is fitted
into the buccal tube of a
molar band.
Lower arch involves a
fitting-in system that is
fixed with a screw to the
inferior arch and placed
distal to the lower cuspid.
Available in two sizes.
Drawback :difficulty to
control the force. www.indiandentalacademy.com

FORSUS- FATIGUE RESISTANT
DEVICE
• An innovative three telescopic
appliance with a coil spring in
its exterior part.
• Advantage lies in coil spring
resistance to breaking.
• The coil spring is applied by its
sliding on a rigid surface
avoiding in this way
angulations at the fixing points.
• It is sold in kits that include
different length sizes for left
and right side


THE FORSUS NITINOL FLAT
SRING
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The Forsus Nitinol Flat Spring is slim,
flat and made of Super-Elastic Nitinol.
Nitinol is always at work, delivering
consistent forces
Requires no laboratory setup, making
chairside installation quick and easy.

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Available in three different bypass
designs, accommodate a variety of
molar attachments

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Force levels remain constant from the
initial setup to the time of removal. The
result is faster, more efficient treatment.


• Study evaluated the clinical application of forsus spring ,
treated 13 patients with class II malocclusion.
• It was found that the saggital correction improved by ¾
cusp width to the mesial on both sides as a result of
distal movement of upper molars and mesial movement
of lower molars.
• Retrusion of of upper and protrusion of lower incisors ,
reduced over jet by 4.6mm and over bite by 1.2mm
• Two- thirds of adolescent patients found Forsus spring
more comfortable


ALPERN CLASS II CLOSERS
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This appliance is most recent.
It is predominantly applied in Class II
correction and as a substitute for
elastics.
It consists of a small telescopic
appliance with an interior coil spring and
two hooks for fixing
It functions in the same way as elastics
and, similarly, is fixed to the lower molar
and to the upper cuspid.
It is available in three different sizes.
Its telescopic action enables a
comfortable opening of the mouth.


Theories of condylar growth
Can we aid in the growth of condyle to a
clinically significant degree ?


Genetic theory
• Suggests that condyle is under strong genetic control,
like an epiphysis that causes the entire mandible to grow
downward and forward.
• More related to prenatal development of condyle.
• Questions the effectiveness of orthopedic appliances in
condylar growth as proposed by Brodie.


Lateral pterygoid hyperactivity
hypothesis
•

By Charles et al, Petrovic and
Later espoused by McNamara.
•
Earliest available acute and
blind EMG monitoring technique,
suggested that hyperactivity of the
lateral pterygoid promotes
condylar growth.
•
Anatomic research has not
found evidence that significant
attachments exist.


3 d perspective of primate TMJ –advanced
downward and forward

LPM tendon is observed attaching to the anterior border of
the fibrous capsule.
•
Recently, permanent implanted longitudinal muscle
monitoring techniques have found that condylar growth is actually
related to decreased postural and functional LPM activity.
∀•


Functional matrix theory
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Postulates that the principal control of bone growth
is not the bone growth is not the bone itself, but rather
the growth of soft tissues directly associated with it.
• ·
Validity is questioned as it lacks explanation of
specific mechanism by which condyle is stimulated to
grow.


Enlow and Hans suggested that mandibular
growth
↓
Composite of regional forces and functional
agents of growth control
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Specific extracondylar activating signals
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Formation of the growth relativity hypothesis

Growth relativity hypothesis
Growth relatively refers to
growth that is relative to
the displaced condyles
from actively relocating
fossa.


Three main foundations:
•
The glenoid fossa promotes condylar growth with the use
of orthopedic mandibular advancement therapy.
•
Initially, displacement effects the fibro cartilaginous lining
in the glenoid fossa to induce bone formation locally ; followed
by the stretch of non muscular viscoelastic tissues.
•
New bone formation at some distance from the actual
retrodiskal tissue attachment in the fossa.


I -foundation

The glenoid fossa promotes condylar growth
with the use of orthopedic mandibular
advancement therapy.


II - foundation
• Initially, displacement
effects the fibro
cartilaginous lining in the
glenoid fossa to induce
bone formation locally ;
followed by the stretch of
non muscular
viscoelastic tissues


III - foundation
New bone formation at
some distance from the
actual retrodiskal tissue
attachment in the fossa.


Three growth stimuli
Displacement + visco elasticity + referred force
•

Modification first occurs as a result of action of
anterior orthopedic displacement.
•
Condyle is affected by the posterior viscoelastic
tissues anchored between the glenoid fossa and the
condyle inserting directly into the condylar fibro cartilage.
•
Displacement and visco elasticity further stimulate
normal condylar growth by transduction of forces over
fibro cartilage cap of the condylar head.


Clinical implications of
viscoelasticity
Useful for dento alveolar changes using
condylar displacement and viscoelastic to tissue
forces.
•
Antero-posterior and vertical changes also
occur by differential eruption of the dentition.
•
Key element in using propulsive orthopedic
appliances is to avoid compression of condyle
against the eminence.
•


•
Compression is associated with reduced
condylar growth, TMD, osteoarthritic changes,
condylar flattening in preadolescent herbst patients.
•To prevent these, herbst appliance can be used with
a posterior bite block and in combination with a rapid
maxillary expander


Factors controlling C_GF modification
6 factors:
• Skeletal(displacement)
• Dental
• Neuromuscular
• Nonmuscular
viscoelastic tissues
• Biodynamic intrinsic
and extrinsic factors
• Maturational age


Condylar light bulb analogy


Skeletal effects of bite jumping
therapy


•

The fundamental principle for all bite jumping functional
appliance is to keep the mandible in protrusive position in an
attempt to evoke condylar and then mandibular growth, which
in turn consolidates the repositioned mandible.
• ·
The fixed functional appliance have mainly two clinical
advantages :
•
The coil-spring mechanism by using superior quality of NiTi
alloy secures a forcible advancement of the mandible with
sufficient flexibility of mandibular functional movement.
•
Direct and easy placement of appliance


On TMJ and mandibular growth
• During normal growth, the mandible is translated
downward and forward as the actual growth occurs at
the mandibular condyle and along the posterior surface
of ramus.
•
The body of the mandible grows longer by periosteal
apposition of bone on its posterior surface.
•
The ramus grows higher by endochondral
replacement at the condyle.
•
Together with the remodeling of glenoid fossa
straight down and posteriorly.


• When the mandible is held in a forward
position by functional appliance, the condyle is
brought downward and forward from its original
position.
•
The ligaments of the disc attaching to the
posterior aspects of both condyle and the
glenoid fossa are stretched and affect the
tissue involved.


•It has been shown that the proliferation of
chondrocytes in condylar cartilage increases and the
bone deposition in posterior of glenoid fossa is
evident.
•
The Mesenchymal cell within the articular layer
of both condyle and glenoid fossa are main source for
bone formation.
•Rabie et al found Mesenchymal cells to be stretched
and oriented in the direction of the pull, which might
trigger the bio physiological path of Mesenchymal
cells differentiating into bone making cells in TMJ.


•

The key difference in mode of bite jumping between
removable and fixed application lie in the duration of
mandibular protrusion and the magnitude of vertical bite
opening. In fixed appliances, the continuation of bite jumping
is secured but the dimension in vertical bite opening is
limited.
•
The Herbst application has been shown to enhance
mandibular growth. It accelerates the growth of the condyles
and result in a change in the growth direction of the condyles,
mostly into a more sagittal direction.
•
Saggital condylar growth was increased white vertical
condylar growth was unaffected by Herbst application
therapy which in contrast to removable application.


Effects related to treatment
timing
• The pattern of the mandibular growth curve follows that
of the general growth curve.
•
Mandibular growth is characterized by an adolescent
growth spurt and its peak closely coincides with that of
the maxilla and general growth.
• The pubertal growth period is most favorable time to
attack many orthodontic problems with skeletal
manifestation when correction of the malocclusion has
been achieved, the patient would reach the rate
adolescent growth period in which growth rate would
slowdown

•Unlike removable application, fixed application imposes a
short treatment time of 6-12 months, which leads to,
considerable flexibility in the selection of treatment time.
•On a short-term basis, the most favorable time to treatment
patient with Herbst application is at or just after the peak of
pubertal growth spurt, as at this time influence of mandibular
condylar growth is greatest and risk of undesirable dental
effects on the mandible is small.


• Taking into consideration other factors, such as the
long term stability of treatment results and efficiency of
retention, the ideal period is when permanent dentition
stage has been reached; at / just after peak height
velocity of growth.
•The major difference in mandibular treatment
changes during various growth periods is because of
the variations in basic mandibular growth rate.
•At long-term follow-up there seems to be no
difference in length of the mandible between patients
treated in different growth periods


Effects related to post treatment
follow -up
• Significant enhancement of mandibular growth occurs
during the initial treatment phase, but return to their pretreatment pattern after treatment on short term basis.
•
Long term studies show that the mandible effects
remained and reason for relapse was the change in
tooth position. The unfavorable post treatment changes
occurring after the removal of application are dominantly
appliance related.


TREATMENT TIMING , IDEAL
PERIOD AND OUTCOME
• How efficient is early class II treatment compared to later
treatment?
• Study at the University of Giensen defined treatment
efficiency as a better result in a shorter treatment time.
• Late treatment of class II treatment was more efficient
than treatment with removable appliances


IDEAL PERIOD FOR HERBST
APPLIANCE
• Permanent dentition at or just after the pubertal peak of
growth corresponding to stages FG to H of the middle
phalanx of third finger


CONCLUSION
From 1900’s when the fixed functional appliances
first appeared , to date, a number of fixed
functional appliances have been developed and
gained popularity.
Fixed functional appliances are called “Noncompliance Class II correctors” giving a false
idea about the co-operation necessary during
treatment .
Understanding mechanisms of action of these
appliances is critical to orthodontist

References
• Dento facial orthopedics with functional appliance- Graber, Rakosi
and Petrovic
• Orthodontics and dentofacial orthopedics-McNamara
• Contemporary Orthodontics-proffit
• The Herbst appliance-Semi. Orthod2002
• Voudouris et al. AJO 2003;123:604-13.
• Voudouris et al. AJO 2000;117:247-66.
• McSherry P F BJO 200;27:219-25
• Ritto AK func. orthod.;1999: 16, 122-35.
• Voudouris et al. AJO 2003;123:13-29


•

•Shin . crania fac res. 2005;8:2-10.
•Pancherz A O 1997;67:111-20.
•Pancherz A JO 1979;76:423-42.
•Jasper JJ AJO 1995;108:641-50.
•Filho JCO 1998;32:379-84.
•Pancherz A JO 2002;121:559.
•Frankel AJO 2001;120:17(a).


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