short notes on fixed functional appliances in orthodontics

1. Fixed Functional Appliances
Safa Basiouny
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Fixed functional appliances
Collected by
Safa Basiouny Mahmoud Alawy
MSc, PhD Orthodontics
Lecturer of Orthodontics, Faculty of
Dentistry, Tanta University

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Contents
1.Introduction
2.Indications and contraindications
3.Advantages and disadvantage
4.Effects
5.Undesirable dental changes & how to counteract
with these changes
6.Classification:
• Flexible FFA
• Rigid FFA
• Hybrid FFA

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Introduction
❖ Functional appliances are those appliances that don’t act
primarily on teeth like conventional appliances (springs, elastics)
• They transmits, eliminate or guide natural forces
• Natural forces that can be controlled by functional appliances are: muscle
activity from the tongue and check, tooth eruption, and growth and
development.
-Although functional appliances have been designed to treat all types of
malocclusions, they are most effective in treating dental and skeletal Class
II malocclusions, particularly cases with mandibular deficiency.
-Functional appliances can be classified as Removable and fixed functional
appliances(FFA)
Disadvantages of removable functional appliances :
• very large in size
• have unstable fixation
• cause discomfort
• exert pressure on the mucosa (encouraging gingivitis)
• reduce space for the tongue
• cause difficulties in deglutition and speech and very often affect
aesthetic appearance, the alteration in the mandibular posture
creates added difficulties.
These adverse effects make the adaptation and acceptance of these
appliances more difficult.
❖ Patient compliance Facts :
During orthodontic treatment, the cooperation or compliance of the patient is
a major factor for a successful treatment outcome. According to Haynes,
compliance, as it relates to healthcare, is the “extent to which a person’s

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behavior (in terms of taking medications, following diets, or executing
lifestyle changes) coincides with medical or health advice.”
This means that in order to achieve successful treatment results, patients are
expected to follow the recommended regimens suggested by their
orthodontists. Unfortunately, noncompliance of the patient is a serious and
common problem and orthodontists have to deal with this issue almost daily.
 Percentage of poor compliance --- 50%
 Both patients and families mis-represent the extent of compliance. 
Compliance decreases the longer the patient is treated
Fixed functional appliances
Indications:
1. It is used primarily in actively growing individuals with favorable
facial growth patterns.
2. Cl . II skeletal pattern with mandibular deficiency
3. Lack of vertical development in lower face height
4. Cl. II molar relationship
5. True deep over bite, with infra-occlusion of the posterior segments
6. The mandibular incisor teeth should be positioned upright over basal
bone structures. The maxillary and mandibular teeth should be well
aligned.
7. Produce headgear effect on maxillary dentition. So, it can be used as
anchorage reinforcement or even for molar distalization
8. In reverse type, it can be used for ttt of class III malocclusion
Contraindications:
1. Non-growing individuals
2. Cl . II skeletal pattern with maxillary excess
3. Increased lower anterior face height

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4. Cl. I molar relationship
5. Shallow over bite
6. Pseudo deep bite due to supra eruption of the anterior teeth
(“Gummy” smile)
7. Proclined mandibular anterior teeth
8. Decreased overjet/ Retroclined maxillary anterior teeth
9. Cases predisposed to root resorption
Advantages of FFA (over removable app):
Fixed functional appliances have lately been in vogue and are preferred over
removable appliances especially in non-compliant patients. They are known
as “non-compliance class II correctors”. However, good pt cooperation is
necessary
1. These have the advantage of 24-hour continuous stimulus for
mandibular growth.
2. They are smaller in size permitting better adaptation to functions like
mastication, swallowing, speech and respiration.
3. Promote better compliance
4. Their greatest advantage seems to be for those patients who report for
orthodontic treatment at fag end of the facial growth. Fixed functional
appliances being 24- hour wear appliances produce rapid sagittal
correction hence utilizing short span of remaining growth to maximum
advantage.
5. Offer extensive range of motion
6. Simple and relatively in expensive
7. Easier to fit
8.Adaptable to either class II or III
9.Can be used for mandibular positioning and/or dentoalveolar movement

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10.Cause less breakage of the archwire and appliances
11.Can be used in any stage of ttt (mixed or permanent)
Disadvantage: the main disadvantage is the dental movement that takes
place during treatment (discussed later)
Effects and mode of correction:
Onset of ttt…in adolescent pt when the majority of permanent teeth have
erupted. Not recommended in mixed dentition to avoid un wanted dental
movements.
Treatment duration…6-9 months (growth remaining and severity of
problem are major considerations).
1. Dentoalveolar changes
• On upper molars — distalization, intrusion. Lateral expansion (if not
counteracted with transpalatal arch)
• On incisors—lower incisor proclination (labial root torque required)
• Reduction in overbite due to intrusion of lower incisors and eruption
of lower molars.
2. Skeletal effects
• Maxilla: High-pull headgear like effect
• Mandible: Mandibular lengthening and forward repositioning.
3. Molar correction
• Increase in mandibular length
• Maxillary molar distalization
• Mandibular molar mesialization.
4. Overjet correction is due to:
• Increase in mandibular length

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• Lower incisor proclination
• Upper incisor retroclination.
5. Overbite correction is due to:
• Intrusion of the lower incisors (partial proclination)
• Enhanced eruption of the lower molars.
6. Soft tissue and Herbst therapy (Pancherz 1995)
• Reduction of soft tissue concavity.
• Retrusion of the U/L lips in relation to E-line
• Improvement in soft tissue profile.
Undesirable dental changes of FFA:
1. Labial tipping or flaring of lower incisor
2. Maxillary posterior dental expansion
3. intrusion of buccal cusps(lingual root torque)
4. Anterior movement of lower dentoalveolar process beyond that
of the body of the mandible or apical base
5. Lingual tipping of maxillary incisor.
Ways to counteract (anchorage preparations):
1. Full sized rectangular arch wire with 10 to 15 degree lingual
crown torque placed in the lower incisor region +cinch back the
arch wire….prevent proclination of lower incisors.
2. Transpalatal arch & lingual stabilizing arch to enhance
anchorage.
3. Buccal root torque +TPA ( counteract with intrusion of buccal
cusps)+heavy rectangular archwire+constriction in archwire
(counteract transverse expansion caused by the buccal vector of
force).

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4. Lingual tipping of maxillary incisor overcomed by lingual root
torque of incisor region or pretorqued bracket with full sized
arch wire tied back.
5. Including upper second molar in the archwire to counter act the
intrusive vector of force to avoid posterior open bite.
Classification of FFA:
Flexible
1. Jasper jumper
2. Amoric torsion coils
3. Adjustable bite corrector
4. Klapper super spring
5. Churro jumper
6. Saif spring
Rigid
1. Herbest app
2. Mandibular protraction
app(MPA)
3. Mandibular anterior
repositioning app(MARA)
4. Universal bite jumper
5. Cantilever bite jumper
6. Ritto app (Magnetic
Telescopic device)
Hybrid
1.Twin force bite corrector
2. Eureka spring
3. Forsus fatigue resistant
device
4.Forsus nitinol flat spring
1-Flexible fixed functional appliances
-Can be described as an intermaxillary torsion coils or fixed springs.
-Elasticity and flexibility are the main characteristics of flexible appliances.
Advantages:
1. Allow great freedom of movement of the mandible
2. Lateral movement can be carried out with ease
Disadvantages:
1. Fracture can occur either in the appliance itself or in the support
system (mainly in lower arch)
2. Fatigue in the spring may occur
3. Tendency of the pt to chew on the appliance..breakage
4. Pt can’t open his mouth widely as this could result in breakage
5. They are not very esthetic app as when the curvature of the spring is
accentuated, some protuberances can appear on the cheek

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6. Covering can degrade quickly especially if the pt bites on the app
7. Relatively expensive(as more than one size can used for the same pt)
8. Due to intrusive force on upper molars, a posterior open bite is
common as well as post expansion
9. Proclination of lower incisors
Jasper jumper (JJ)
Appliance design:
-It is constructed from stst coil that is attached at both ends to stst end caps.
-It is covered with opaque polyurethane covering for hygiene and comfort.
-It is available in 7 sizes ranging from 26mm to 38mm in length in 2mm
increment.
-The force module is selected by measuring the distance between the mesial
aspect of upper facebow tube and distal aspect of the lexan ball distal to the
mand canine. To this length, 12mm is added to get the required length of the
force module.
-The end caps are attached to the fixedapp at: posteriorly to the facebow tube
of max first molar by a ball pin. Anteriorly, to the lower archwire distal to
mand canine by a small bayonet bend and lexan bead.
-When the teeth come into occlusion the force module being longer tends to
curve ..producing mesial force on mand arch and distal force on max arch

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Indications
• Dental and skeletal class II
• Deep bite with retraclined mand incisors
Contraindications
• Dental and skeletal open bite
• Vertical growth
• Minimum buccal vestibular space
• Case predisposed to root resorption
Advantage of JJ
• Produce continuous force
• Doesn’t require pt compliance
• Oral hygiene is easier to maintain
• Allow greater degree of mand freedom rather than Herbest app
Effects:
Skeletal(40%):
• Hold and displace maxilla distally
• A small shift of point A distally
• Clockwise rotation of mand
• Condyles move forward
Dentoalveolar(60%):
• Posterior tipping and intrusion of maxillary molars
• Posterior tipping of maxillary incisors
• Anterior tipping and translation of mand incisors
• Intrusion of mand incisors
Jasper 1980 stated that class II correction with this app isbrought about by
20% maxillary skeletal restraining , 20% backward dentoalveolar movement
of maxilla, 20% forward dentoalveolar movement of mand, 20% condylar
stimulation, 20% downward and forward remodeling of glenoid fossa.

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2-Rigid fixed functional appliances
-These app have two distinct differences in relation to flexible FFA:
-They don’t easily fracture but they neither have elasticity nor flexibility
-After fitting and activation they don’t aloe the pt to close in centric relation
this mean that the mand is in forward position 24 hour a day creating greater
stimulus for mand growth rather than flexible FFA
Herbest appliance
-Bilateral telescopic mechanism that keep the mand mechanically in a
continuous anterior position
-Consist of a tube into which the plunger fit
-The tube is fixed to the distal end of the maxillary molars while the rod is
fixed to the lower first premolars
Types:
Banded Herbest
-Upper and lower first premolars and molars are banded
-The tubes are fixed to bivots soldered to the distobuccal aspect of upper
first molar bands
-The shaft or rods are fixed to pivots soldered to lower first premolar bands
Bonded Herbest
-Wire reinforced acrylic splint that covers the occlusal and part of buccal
and lingual surfaces of all teeth except the anteriors
-The pivots are fixed to the wire framework at the distobuccal aspect of
upper first molars and mesial aspect of lower first premolars

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-The tube is fitted into the pivot in the maxillary molar area while the shaft is
fixed to the pivot in mandibular premolar region
N.B.
The original design is a banded Herbest but it has undergone some changes
with few modifications taking place with regard to methods of application
(type I,II,III,IV)
Advantages:
• Its action is continuous 24 hour a day
• Shorter ttt duration
• Less pt cooperation
• Can be used for pt who are at the end of their growth
• Can be used in pt with mouth breathing habit due to nasal airway
obstruction
Disadvantages:
• Initial pt discomfort
• Causes transient functional disturbance
• Increase TMD and development of dual bite
• Repeated breakage and loosening of app
• Plaque accumulation and enamel decalcification
• Tendency of post open bite
Timing:
• At or just after the pubertal growth spirt and when the permanent
dentition is established
• ttt in mixed dentition is not recommended
Treatment effects:
• Class I molar relation

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• Increase mand growth
• Distal driving of max molars
• Decrease overjet by increasing mand length and proclination of mand
incisors
• Inhibition of sagittal max growth
• Anterior transformation of glenoid fossa
• Increase SNB and decrease SNA angles
Mandibular Anterior Repositioning Appliance (MARA)
-It consists of cams made from 0.060 square wire attached to tube0.062
square on upper first molar bands or stst crown
-A lower first molar crown has 0.059 arm projecting perpendicular to its
buccal surface which engage the cam of upper molar
-The appliance is adjusted so that when the pt close the cam of upper first
molar guide the lower first molar and repositioning the mandible forward
into class I relationship
-The developer of appliance recommended 12 month ttt time to achieve a
bite jumping or orthopedic effect
-For stabilization of appliance upper TPA and lower lingual arch
-This appliance doesn’t require the placement of attachments on teeth other
than first molars
disadv:
-Temporary stst crowns are needed on all first molars
-Direct contact of lower molars with the metal give unpleasant sensation

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adv:
-ttt result of MARA are very similar to those produced by Herbest with less
headgear effect and less mand incisor proclination
-Can be used without attachments on other teeth except first molars.
3-Hybrid fixed functional appliances
-Hybrid appliances represent the combination of rigid FFA with flexible
FFA.
-They could be described as rigid appliance with coil spring type system
-The objective of these app is to move the teeth by applying 24 hour elastic
continuous force that would replace the traditional use of elastic and
extraoral force.
-Their common feature is the use of coiled spring to produce this force.
Twin Force Bite Corrector (TFBC)
-It is a push type intermaxillary FFA with ball and socket joint fastness that
allow wide range of motion and lateral movement
-The plunger/tube telescopic assembly contain niti coil spring that deliver a
constant force (average 210 g)
-The appliance is attached to maxillary and mand archwires by hex nuts
fastened mesial to maxillary first molar and distal to mand canines
-At full compression the TFBC postures the pt mand forward into an edge to
edge occlusion
-After aligning and leveling and with the pt in habitual maximum occlusion,
measure the distance from mesial edge of upper first molar tube to distal
edge of lower canine bracket.
If the distance is <27mm….twin force small is used
If the distance is >27mm… . twin force standered is used

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Advantage:
• Minimal pt cooperation
• Produce continuous and light force due to its niti coil spring
• Allow lateral jaw movement which is more comfortable to the pt
• No lab work is required as it is inserted directly at the clinic using
simple procedure… decrease time and cost
• Easy to remove at the clinic to check the position of mandible
• Can be used both in extraction and nonextraction cases
Other uses:
• Distalization of upper molar
• Reinforcement of anchorage in extraction case
• Inverse use in class III malocclusion
Forsus Fatigue Resistant Device
-This is an innovative 3 telescopic app with a coil spring in its exterior part.
-Available in different length and sizes for right and left sides.
-Can be fixed in various way according to needs of the pt.
-Allow controlling the amount of force through various available sizes or
through direct attachment to the lower arch and use of stop for activation.
-Can be used in cases of mixed dentition
-It allows for dental asymmetry correction when higher force on both sides
is needed
-It allows pt to open and move their jaw freely
Component:
Spring Modules
L-pin Spring Module EZ2 Module
-The L-pin module allows for more
flexible installation options and
movement in the mouth.
-It can be used with a gingival or
occlusal headgear tube.
-The left and right sides are universal
-The EZ2 module allows for more
consistent installation and
automatically prevents the spring
from pivoting toward the cheek.
-The EZ2 module can be used only
with an occlusal headgear tube and
has permanently marked indicators
for the left and right sides

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Push Rods
The push rods come in six different lengths and are oriented to the patient’s
right and left.
Measurement Gauge
The measurement gauge is used to select the correct push rod length
Determining Push Rod Position
There are three options available to place the push rod:
1-Bicuspid
Placing the push rod distal to the bicuspid is a more recent recommendation
for placement.
The benefits of placing the push rod distal to the bicuspid include improved
patient comfort, better aesthetics and reduced interference.
2-Cuspid
The traditional location to place the push rod is distal to the cuspid.
Placement behind the cuspid will work in most cases, especially when the
bicuspid is not an option, for example:
• When placement at first bicuspids is over-active with a 22 mm push rod
• When placement is more vertical than needed
• Severe Class II malocclusions where a large portion of the discrepancy is
from a retruded mandible
3-Omega Loop
Using an Omega Loop allows the angulation to be varied. It will also keep
the push rod from contacting the bracket

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Push Rod Selection
1. Use the Measurement Guide to determine correct push rod length,
depending on the selected push rod location (distal to cuspid, bicuspid,
Omega loop).
a. Measure each side from the distal end of maxillary molar tube to the distal
side of the chosen mandibular stop, having the patient bite in centric
occlusion without advancing the mandible. When in doubt, use the shorter
length push rod.
b. Select the Right and Left configuration push rods from the available sizes.
Note: It is important to measure both the right and the left sides
2-Once the push rod is placed in the correct position, have the patient bite
down in centric occlusion and double check the spring activation.
• Correct activation exerts approximately 200 grams of force.
• There should be 2 mm of space (1 mm minimum) between the completely
compressed spring and the stop on the push rod, with patient in centric
occlusion.

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3-Avoiding overactivation:
-It is important to avoid overactivation. If the push rod protrudes distally of
the spring module in centric occlusion, the spring is overactivated because
the push rod is too long.
Overactivation can result in:
• Debonding of brackets
• Unwanted dental movements
• Flaring of mandibular incisors
• Unplanned rotations
• Breakage
Note: If the push rod is overactivated, switch to a shorter push rod.
Appliance removal
The fixed functional appliances is ready to be removed when:
• Buccal segments and molar relationships are Class I.
• Maxillary incisors have ideal torque and position.
• Overjet is eliminated.
Clinical tips
1-Mandibular incisors will rebound approximately 2-3 degrees after spring
removal if using negative torque on incisor brackets. So, slight
overcorrection of 1-2 mm is preferred (edge to edge incisor relation).
2- Once the targeted amount of correction is achieved, it is recommended to
keep the non-activated appliance in place for at least one appointment
interval.
3- elastics for final occlusal adjustment after appliance removal.