Basic concepts of functional appliances with theories of craniofacial growth , mode of action of functional appliances and recent advances.

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2. BASIC CONCEPTS OF
FUNCTIONAL APPLIANCES
Presented by
Dr.Ashok kumar A
1st year PG
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3. SYNOPSIS
• Introduction
• Evolution
• Classification
• Indications & Criteria for functional Appliance
therapy
• Effects of functional appliances
• Principles of functional appliances
• Theories of craniofacial growth
• Mode of action of functional appliances
• Conclusion
• Reference
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4. INTRODUCTION
Functional appliances are defined as loose fitting or passive
appliances which harness natural forces to the orofacial
musculature that are transmitted to the teeth and alveolar bone
through the medium of the appliances.
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5. Loose removable appliances are those designed to alter the
neuromuscular environment of the orofacial region to improve
occlusal development and/or craniofacial skeletal growth.
Most loose removable appliances,
a) utilize muscle forces to effect dental and bony changes,
b) disarticulate the teeth,
c) encourage new mandibular position,
d) require a tight lip seal during swallowing, and
e) selectively alter the eruptive paths of teeth.
5Hand book of Orthodontics – Robert E Moyers

6. EVOLUTION OF FUNCTIONAL
APPLIANCES
• 1879 -Norman kingsley ,
bite jumping appliances
• 1888-Wilhelm Roux ,
Theory of functional adaptation
• 1902-Pierre Robin,
Monobloc
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7. • 1908-Viggo Anderson,Loose fiting appliances
(Biomechanical working retainer)
• 1936- Anderson & Karl Haupl,
Norwegian appliances
(Functional jaw orthopedics )
• 1918-Alfred Paul Rougers,
Father of Myofunctional therapy
• 1909-Emil Herbst ,Piston worked
fixed appliances
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8. • 1949-Dr H.P.Bimler ,
Bimler Appliances
• 1950-Wilhelm Balter
Bionator
• 1956-Martin Schwarz ,
Double plate
• 1960-Rolf Frankel,
Functional Regulator
• 1977-William J Clark,
Twin block
• 1979-Hans Pancherz ,popularized herbst appliance
• 1989-Blechcmann et al-
Magnetic functional therapy
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9. CLASSIFICATION
Graber’s classification -
Group 1 : Inclined plane , Oral screen
Group 2 : Activator
Group 3 : Frankel appliance
Proffit’s classification -
Tooth-borne passive : Bionator, Activator, Herbst
Tooth-borne active : Activator modification
Tissue-borne : Frankel appliances
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10. Based on Nature of Removability -
Removable : Activator , Twin block
Semifixed : Bass , Denholtz
Fixed : Flexible - Jasper jumper
Rigid - Herbst appliances
Based on the way Muscle Used -
Myotonic - Bionator
Myodynamic - Bimler
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11. Indications and Criteria for functional
Appliance therapy
1. Skeletal Criteria
Low angle case
Proportionate balance between upper & lower face
Mild to moderate class II pattern
Positive VTO
2. Dental Criteria
No crowding
No labial tipping of mandibular incisors
Moderate deep overbite 11

12. 3.Soft tissue criteria
Competent or potentially competent lip
Muscular pattern that does not exhibit undue tightness
4.Emotional Criteria
Keen patient interest & desire from both patient & parent
Patient cooperation is essential .
5.Respiratory Criteria
No nasal obstruction or chronic respiratory disorders
6.Age/Growth Criteria
Indicated in growing patient ( Late mixed dentition )
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13. Effects Of Functional Appliances
on dentofacial skeleton
Dentoalveolar Changes
-Proclination of lower anterior
-Retroclination of upper anterior
-Differential eruption of teeth
-Mesial & vertical eruption of lower molars
-Flattening deep curve of spee & change in
funtional occlusal plane
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14. Skeletal changes
-Enhanced growth at the head of condyle
-Mandibular growth & forward placement
-Defelection in ramal form and reduction in gonial angle
-Remodelling of CGF complex & relocation
-Increase in lower anterior face height.
-Restraining vertical & sagittal growth of
maxilla .
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15. PRINCIPLES OF FUNCTIONAL
APPLIANCES
Forces modulated by the Functional appliances
- Primary
- Secondary
A primary objective of functional appliances is
to take advantage of these natural forces and
transmit them to selected areas for desired change .
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16. It is important to consider that functional are both tooth
movement and skeletal changes (through growth
modification).
Lip bumper transmit lip force(primary) to the PDL in form
of pressure(secondary) which cause distalization of molar.
For growth modification , they transmit forces to the
condylar region & thereby , inducing new bone formation or
glenoid fossa remodeling.
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17. Duration of force in most Functional appliances is
interrupted because it is usually not worn constantly.
The magnitude of force is small in functional
appliances therapy ( deliver light & physiologic
forces)
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18. Force Application
Compressive stress & strain act on the structures
involved resulting in primary alteration in Form with secondary
adaptation in Function.
Force Elimination
Function is rehabilitated & followed by secondary
adaptation in Form.
Neuromuscular response
Secondary adaptation of form to function or vice versa occurs
due to neuromuscular response
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19. THEORIES OF CRANIO FACIAL
GROWTH AND MODE OF ACTION
OF
FUNCTIONALAPPLIANCES
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20. THEORIES OF GROWTH
Growth Site
• Periosteal or sutural bone
formation & remodelling
resorption adaptive to
environment influences.
• Any location where growth
takes place
• All growth sites are not
growth centres .
Growth centre
• Places of ossification with
tissue separating forces
• Any location where
genetically controlled growth
takes place
• All growth centres are growth
sites
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21. GENETIC THEORY
Allan Brodie - 1941
• Genotype supplies all information required for phenotype
expression
• This theory is more of an assumption & it is not proved .
• Primary genetic control determines
only certain features & does not
have complete influence on growth .
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22. SICHER’S HYPOTHESIS-1952
Sicher and Weinnman
• Sutures that attach facial areas to the skull & cranial
base region push the naso-maxillary complex forward
to pace its growth with that of mandible.
• Lack of innate growth potential
• Sutures are reactive areas ,
not primary determinants of growth
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23. SCOTT’S HYPOTHESIS
Cartilage is the primary determinant of
growth while sutural & bone growth occur in
response to growth of cartilage .
Innate growth potential in the cartilage of
the nasal septum & mandibular condyle which
paces the growth of maxilla &
mandible.
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24. FUNCTIONAL MATRIX THEORY
Melvin Moss
• The concept of this theory was introduced first by Vander
Klaaw (1948-52).
BONES DO NOT GROW ,THEY ARE GROWN (1972)
The functional matrix hypothesis claims that the origin,form,
position ,growth, & maintenance of all skeletal tissue and
organs are always secondary ,compensatory and necessary
response to chronologically and morphologically prior events
or process that occur in specifically related non skeletal tissue ,
organs or functioning spaces
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27. Functional regulator uses all the logical means for growth
modification namely:
- Active muscular involvement(proprioception)
- Viscoelastic hypothesis (periosteal stretch by lip
pads/buccal shields)
- Screening deleterious forces (lip pads/buccal shields)
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28. SERVO SYSTEM THEORY
Alexandre Petrovic
Cybernatic system
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Closed loop
Open loop Regulator Servo system

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30. Release of Hormones
(Command)
Position of Maxillary
Dental arch(Ref Input)
Occlusion
(Comporator)
Periodontium
Teeth
Musculature
Joint
Mastication
(Performance)
Deviation signal
Brain
(Sensory engram)
Actuator (Motor cortex)
LPM & RDP
(Coupling system)
Growth at condyle
(Controlled system)
Actuating
signal
Output
Hormones
The Face as a Servo system
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31. Factors influencing
Growth
Primary cartilage Secondary cartilage
Hormones Yes yes
Local factors No (Chondroblast
surrounded by matrix)
Yes(Pre-Chondroblast
Not surrounded by
matrix)
Orthopeadic appliances Only direction Amount & direction
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32. Decreased biochemical feedback
Stutzmann & Petrovic
Zone of functional chondroblast in condyle secretes a
substance that retards the mitotic activity of stem cells – a sort
of negative feedback.
• Stimulation of LPM subsequent to FA wear cause quick
maturation of chondroblast ,secreting less ‘negative feedback’
material .
• Removal of this biochemical brake cause acceleration of
condylar growth.
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33. Functional appliance
↓
Increased contractile activity of the LPM
↓
Intensification of the repetitive activity of the
retrodiscal pad (bilaminar Zone)
↓
Increase in Growth-stimulating factors
(enhancement of local mediators,
Reduction of local regulators of –ve feedback)
↓
Change in condylar Trabecular Orientation
↓
Additional Growth of Condylar Cartilage
and subperiosteal ossification of the Posterior Border
of the mandible
↓
Supplementary lengthening of the Mandible
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34. MUSCLE PHYSIOLOGY
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35. Myotactic Reflex
“Myotatic reflex activity of protractor muscle, especially
lateral pterygoid ,keep mandible in forward direction,
stimulating the growth of mandible”
Grude (1952) suggested that such adaptation is possible only
with small bite opening (within physiological rest position)
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36. • If muscles are stretched too much ,then clasp knife reflex will
take over myotatic reflex.
• Andersen-Haupl concept stated that the myotatic reflex activity
that arises & the isometric contraction(kinetic energy) induces
musculoskeletal adaptation by introducing new mandibular
closing pattern . H –Activator
.
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37. VISCOELASTIC HYPOTHESIS
Herren Harvold Woodside
Viscoelastic properties of muscle & Stretching
of soft tissue are decisive for activation of functional
appliances.
STAGE
Emptying of vessel
Pressing out of interstitial fluid
Stretching of fibers
Elastic deformation of bone
Bioplastic adaptation of bone
B
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38. • Harvold & Woodside opened mandible 10-18 mm
beyond postural rest vertical dimension.
• Overextended activator stretching soft tissue like
splint induce no myotatic reflex but instead applies
rigid stretch and buildup in potential energy .
V – activators, sagittal
Advancement is less with
Increased vertical opening
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39. Transitional type activator -
Alternatively uses muscle contraction & viscoelastic
properties of soft tissue ( both kinetic & potential energy )
MUSCLE STRETCHING METHOD – Eschler
Technique that open vertical dimension beyond 4mm
construction bite , working alternatively with isotonic &
isometric muscle contraction .
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40. BALTERS PHILOSOPHY
Theories upon which the bionator is based:
1.The works of Robin, Andresen and Haupl.
2.The early function and form concepts of Van der
Klaaw and the functional matrix theory of Moss.
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41. Equilibrium between the tongue and the circumoral muscles –
shape of dental arches and intercuspation.
The essential part of Robin’s concept is function whereas for
Balter’s it is the tongue (which is the center of reflex activity in the
oral cavity).
• Effects :
-Modulation of muscle activity of Tongue .
-Elimination abnormal influence
of perioral musculature
-Stimulation of myotatic muscle
activity & isotonic muscle contraction
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42. Clark’s Twin Block
• Wolff’s law - The internal and external structures of
bone is modified by functional demands
• In the dentition the force of occlusion of the teeth is the
most natural functional mechanism that can be used to
influence the structure of the supporting bone.
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43. • Twin blocks are simple bite – blocks that
effectively modify by transmission of favourable
occlusal forces to inclined plane
• Occlusal forces transmitted through the dentition
provide constant proprioceptive stimuli to
influence the growth rate and trabecular structure
of the supporting bone.
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44. Pterygoid response
• McNamara and Petrovic noticed one peculiar phenomenon
where patient experienced pain when mandible was retracted.
They termed it as ‘pterygoid response’
• . This was due to altered muscular balance resulting in ‘tension
zone’ distal to condyle.
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45. Improved clinical use of Twin-block and Herbst as a result of
radiating viscoelastic tissue forces on the condyle and fossa in
treatment and long-term retention: Growth relativity
Voudouris & Kuftinec AJODO (2000)
• Growth relativity refers to growth that is relative to the displaced
condyles from actively relocating fossae.
• Attachments of the LPM to the condylar head or articular disk may
be expected to cause condylar growth, but anatomic research has not
found evidence that significant attachments actually exist
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46. • Hyperactivity of LPM during mandibular advancement
therapy is doubtful as the muscle actually shortens during
this procedure.
• More recently, permanently implanted longitudinal muscle
monitoring techniques have found that the condylar growth is
actually related to decreased postural and functional LPM
activity.
(Sessle, Woodside, Gurza, Powell, Voudouris and Metaxas,
1990)
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47. Growth relativity hypothesis
• In his hypothesis, growth is discussed relative to long-term retention
results, rather than short- term treatment outcomes that are different
• THREE GROWTH STIMULI in growth relativity
Displacement + Viscoelasticity + Referred force
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48. Mandible advanced forward
Stretching of retrodiscal tissues
Engorgement of blood vessels
Influx of various nutrients into fibrocartilage
During reseating of condyle
Expulsion of these nutrients
Metabolic pump like action
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49. Alteration of synovial fluid dynamics
During disocclusion (open position)
Low subatmospheric pressure within the TMJ
Alters the joint fluid dynamics/ flow of synovial fluid
Negative pressure created shifts the fluid
perfusion in a posterior displaced direction
Permits greater flow of blood into C-GF region
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50. • The concept that viscoelastic tissue forces can affect growth of the
condyle suggests that modification first occurs as a result of the action
of anterior Orthopedic displacement.(Displacement)
• Second, the condyle is affected by the
posterior viscoelastic tissues anchored
between the glenoid fossa and the condyle,
inserting directly into the condylar
fibrocartilage. (Viscoelasticity)
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51. • Third and the most interesting aspect is the new bone formation
some distance from the actual retrodiscal tissue attachments in
the fossa by the transduction of forces over the fibrocartilage
cap of the condylar head
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52. Light Bulb Analogy of Condylar growth and
Retention
• The active return of the condyles to the fossae during post-
treatment appears to deactivate the modifications occurred by
compressing the condyle against the proliferated retrodiskal
tissues.
• Hence long term retention is not clinically significant 52

53. VEGF and bone formation in the glenoid fossa during
forward mandibular Positioning - Rabie.M , Lily Shum
AJO DO 2002;122:202-09
• VEGF - central regulator of angiogenesis – induces
endothelial cell migration and proliferation
VEGF is secreted by chondroid cells in response to
forward mandibular Positioning.
Neovascularization
Differentiation of mesenchymal cells – osteogenesis
Highest amount of new bone formation – posterior fossa
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54. VEGF expression and bone formation in posterior
glenoid fossa during Stepwise mandibular
advancement - Rabie.M, Lily shum AJODO
2004;125:185-90
• After 2nd advancement – this pull effect again
delivers mechanical strain that triggers another cycle of
VEGF expression.
• Thus stepwise advancement delivers a series of
mechanical stimuli that produces tissue response that
lead to increased vascularization and bone formation.
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55. Outcomes in a 2-phase randomized clinical
trial of early Class II treatment
Tulloch, William A. Proffit , (AJODO 2004;125:657-67)
• Early (preadolescent) versus later (adolescent) treatment for
children.
• Favorable growth changes were observed in about 75% of those
receiving early treatment with either a headgear or a functional
appliance.
• After a 2 phase of fixed appliance treatment for both the previously
treated children and the untreated controls, however, early treatment
had little effect on the subsequent treatment outcomes.
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56. • The differences created between the treated children and
untreated control group disappeared when both groups received
comprehensive fixed appliance treatment during adolescence
• 2 phase might not be more clinically effective than 1 phase
• Early treatment did not reduce the percentage of children needing
extractions in phase 2 or eventual orthognathic surgery
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57. Mandibular changes produced by functional
appliances in Class II malocclusion:
A systematic review
Paola Cozza et al – AJODO 2006
• “Does the mandible grow more in Class II subjects
treated with functional appliances than in untreated
Class II subjects?”
• “Is the average effect of functional appliances on
mandibular length clinically significant?”
• “Which functional appliances are more efficient?”
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58. • Two-thirds of the samples in the 22 studies reported a
clinically significant supplementary elongation in total
mandibular length (a change greater than 2 mm in the treated
group compared with the untreated group) as a result of overall
active treatment with functional appliances.
• The amount of supplementary mandibular growth appears to
be significantly larger if the functional treatment is performed
at the pubertal peak in skeletal maturation.
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59. • The Herbst appliance had the highest coefficient of
efficiency (0.28 mm/month) followed by the Twin-
block (0.23 mm/month).
• Both the bionator and the activator had
intermediate scores of efficiency (0.17 and 0.12
mm/month, respectively).
• The Frankel appliance had the least efficiency
(0.09 mm/month).
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60. CONCLUSION
Growth modification or Growth re-direction
• Answers to these questions are still at large , one thing is clear
that Growth modification/growth re-direction & Success with
this mode of treatment is influenced by multitude of factors
which include severity and nature of problem ,biological
growth potential of the individual ,appliance selection
,operators experience & expertise ,and patient cooperation .
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61. REFERENCE
1. Dentofacial Orthodontics with functional appliances-Graber
Petrovic Rakosi 2nd edition
2. Removable Orthodontic Appliances- Graber Neumann
3. Orthodontic principles and practice- T. M. Graber – 3rd Edition
4. Contemporary orthodontics- William profitt – 4th edition
5. Orthodontics – Diagnosis and mangement of malocclusion
and dentofacial abnormalities – Om Prakash Kharbanda
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