Controversies surrounding the efficacy of functional appliance

CONTROVERSIES
SURROUNDING
THE EFFICACY OF
FUNCTIONAL
APPLIANCES
www.indiandentalacademy.com

INTRODUCTION
A common strategy in the treatment of class II
malocclusion is frequently aimed at masking
the skeletal discrepancy or improving the
existing skeletal imbalances, arch form and
orofacial function using a variety of functional
appliances. But how effective are these
appliances in achieving the desired results &
what exactly happens at the specific sites…www.indiandentalacademy.com

DEFINITION
Loose removable appliances, designed to alter
the neuromuscular environment of the orofacial
region to improve occlusal development and
craniofacial skeletal growth
Loose fitting or passive app which harness
natural forces of the orofacial musculature that
are transmitted to the teeth & the alv bone
through the medium of the appliance.www.indiandentalacademy.com

CONCEPTS OF
FUNCTIONAL JAW
ORTHOPEDICS

NORMAN W.KINGSLEY (1880)
Jumping the bite
Vulcanite anterior inclined bite plane
Brought the lower dentition forward
without proclining the lower incisors
Hawley bite plate, with ant inclined
plane – Retainer,For TMJ problemswww.indiandentalacademy.com

PIERRE ROBIN (1902)
Monoblock
To position the mandible forward in
pts with Pierre Robin syndrome
First appliance that influenced the
oral muscular activity

VIGGO ANDRESEN (1908)
Followed Kinsgley’s concept & modified his
appliance –Used as a retainer after FA
Mobile loose fitting appliance with extended
lingual flanges (Myodynamic)
Construction bite
Biomechanic working retainerwww.indiandentalacademy.com

GROWTH GUIDANCE ???
To eliminate the adverse effects of abnormal
function
Lower lip trap
Hyperactive mentalis
Mouth breathingwww.indiandentalacademy.com

ANDRESEN + KARL HAUPL
Activator
Growth changes in TMJ & glenoid fossa
Permanent forward displacement of mandible
Stimulation of normal growth of the jaw
“Individual optimum”

HERREN ACTIVATOR
Paul Herren’s concepts
Night time loose appliance didn’t work as
claimed
Acts as a splint which repositions the md
during sleep
Herren’s modifications
Over compensating the anterior position
Firmly seating the appliance against maxilla
(Myotonic)www.indiandentalacademy.com

Harvold-Woodside activator
Exceeded the postural rest position to keep the
appliance in place during night
Vertical opening – up to 15mm
Forward positioning – 3mm distal to most
protrusive position
Wider opening – Visco-elastic force

BALTER’S CONCEPT(1960)
Bionator
Equilibrium b/w the tongue & circumoral
muscles is responsible for the shape of the
dental arches & intercuspation
The functional space of the tongue is essential
to the development of the orofacial system
Reduced bulk of the appliance

FUNCTION REGULATOR OF
FRANKEL
Oral vestibule – operational basis
Relieves pressure from Buccinator
mechanism – widening of dental arch &
apical base
Myotonic device, becomes myodynamic
with muscular exerciseswww.indiandentalacademy.com

CONSTRUCTIO
N BITE
CONTROVERSI
ES

Sagittal advancement
Vertical opening
Step by step/ Single step advancement

SAGITTAL
ADVANCEMEN
T

3- 6mm sagittal advancement
Severity of AP malrelationship &
Buccal segment interdigitation

HERREN & SHAYE ACTIVATOR
Overcompensated anterior position
3 – 4mm beyond neutroclusion
2 – 4 mm vertical opening in incisor region
Arrowhead clasps to seat the appliance
against maxilla
Myotonic applianceswww.indiandentalacademy.com

VERTICAL
OPENING

Andresen Activator
2mm opening- well within the
freeway space
Myotatic reflex activity & isometric
muscle contraction
Frankel & Bionator – Lip seal

Selmer Olsen 1937,
Harvold 1946, 1974
Woodside 1973
Vertical opening – beyond rest position
- 10-15mm
Stretching of soft tissues, Viscoelastic
propertieswww.indiandentalacademy.com

Schmuth 1994
Witt 1981
Witt & Komposch 1979
4-6 mm below the intercuspal position
Long periods of continuous pressure
Isometric contraction/viscoelastic properties

Step by step
or
Single step
advancement

Step by step advancement
Recommended by Frankel
Minor sagittal problem (2-4mm)
Single step advancement
Major sagittal problem (6 mm)
Advancement of 3 mm each
Not more than 2.5 to 3 mmwww.indiandentalacademy.com

Easy acceptance by the patient
  Less likelihood of dislodgement of the
appliance during both the day and night.
  More favorable mandibular response
  Decreased muscle strain or fatigue
  Less proclination of lower incisors
Advantages of staged advancement

Neumann
•Tries to avoid stepwise advancement
recommended by Frankel.
•Advances the mandible the width of the
entire tooth,
•Exception - severe malocclusion in the vertical
vector as well as in the horizontal vector.

PERIODIC FORWARD REPOSITIONING
Robert Shaye,JCO-1983
Construction bite- Full protrusive position
Reactivation after 3 months
Reduced muscular strain
Increased mandibular length

Timing
of
treatment

Arne Bjork, AJO-1951
Early treatment – Greater effect on the apical
base of the dentition
Deciduous dentition – Most effective
Mixed dentition – less effective
Permanent dentition – very limited effectwww.indiandentalacademy.com

Frankel
Late mixed or transitional dentition
period
Greatest adaptational change in soft &
hard tissues

Pancherz & Hagg, AJO-1985
Favorable time -Peak of pubertal growth spurt
Increased condylar growth
Decreased dental effects
Early Rx - Unstable occlusion
- Extended retentionwww.indiandentalacademy.com

Demish - 1973
Compared the body height with
timing & duration of activator Rx
No interdependence b/w Rx effect &
pubertal growth spurt.

Effects of
functional
appliances

EFFECTS ON MAXILLARY
GROWTH
Hotz,AJO- 1970; Meach AJO-1966
Harvold & Vargervik, AJO 1971
Evald & Vargervik, AJO 1966
Freunthaller, AO 1967
McNamara, AJO-1973,1980,1982
Restriction of maxillary
growth
Head gear effectwww.indiandentalacademy.com

Jacobsson, AJO-1967,
Activator can cause a backward tilt
of the maxilla, as well as a restriction in
the normal downward and forward
growth of the maxilla
Frankel – No effect on maxillary growth

Almeida et al, EJO-2004
No significant difference in maxillary
skeletal measurement
Mandibular size significantly increased
Major effects are dentoalveolar with a
smaller skeletal effect
(Bionator)

EFFECTS ON MANDIBULAR
GROWTH
2 SCHOOLS OF THOUGHT
Increased
mandibular growth
Normal growth

Arne Bjork et al AJO-1951
The mandibular growth that occur in the
course of the Rx lies within the range
of normal growth. The Rx results
achieved are mainly confined to
reshaping of the alveolar archeswww.indiandentalacademy.com

Creekmore & Radney, AJO-1983
Compared Frankel, Edgewise therapy &
untreated samples
• No significant difference in forward mand.
growth b/w class I, II & untreated samples
• Forward gr of maxilla was reduced in cl II FR
• Both Frankel samples moved the l/incisors
forward www.indiandentalacademy.com

No significant diff. in yearly growth
increments for mand. length, maxillary length,
maxillomandibular differential & lower facial
height
Retraction of u/incisors - 37%
Labial movement of l/incisors - 26%
Retraction of maxilla - 16%
Normal forward growth of mandible- 21%www.indiandentalacademy.com

Woodside, Harvold et al AJO-1983
Consistent change in bone shape & internal
structure are obtained when the alteration in
neuromuscular activity is continuous
Only Herbst appliance can produce continuous
force
Removable appliances produce only intermittent
force
There is no clinically useful amount of condylar
remodeling associated with func.app therapywww.indiandentalacademy.com

Harvold & Vargervik, AJO-1971
Selective & controlled influence on the buccal
segments
Normal forward development of the maxilla
was delayed
Growth in mand length was unaffected
(Activator)

Kevin O’Brien et al, AJO-2003
Studied the effectiveness of early orthodontic
treatment with the twin block appliance
Substantial reduction of overjet was due
to dentoalveolar change, with a small
element of favorable skeletal change.

Pancherz, AJO-1984
Equal dental & skeletal changes
Mandibular growth appeared not to be
affected by activator Rx
Threshold for adaptive remodeling process in
the condyle
(Activator)

Paola Cozza et al,EJO-2004
Orthopedic retraction of maxilla
No significant increase in mandibular length
Anterior displacement of mandible
Anterior relocation of glenoid fossa (NSCo
angle)
(Activator)

Studies by McNamara
Form function relationship – Functional
protrusion in Rhesus monkey
McNamara - AJO,1973
Elgoyhen et al – AJO,1972
McNamara-1972
McNamara-1976
McNamara- EJO,1980
McNamara - AJO,1981
McNamara - AJO,1982www.indiandentalacademy.com

Cast gold or ticonium onlays
To alter the mandibular postural position
Ant- 4 to 5 mm
Vertical- 2 to 3 mmwww.indiandentalacademy.com

ELECTROMYOGRAPHIC FINDINGS
Decrease in the activity of posterior
Temporalis
Increase in the activity of Masseter
Increase in the activity of Lateral pterygoid
muscle
Distinct change in muscle activity

CEPHALOMETRIC FINDINGS
Implants were placed in maxilla, mandible,
frontal bone & cranial base regions
Mandibular changes – Growth of the condyle
increased in the following directions
Posterior condylar growth
Posterosuperior condylar growth
Superior condylar growthwww.indiandentalacademy.com

HISTOLOGIC FINDINGS
Significant adaptations could be seen along the
posterior & posterosuperior regions of the TMJ
(after 2weeks)
Increased deposition of new bone along the
posterior border of the ramus & anterior border
of the postglenoid spine
Greatest response – After 6 weeks
4 fold increase in the posterior thickness of
condylar cartilage www.indiandentalacademy.com

Adaptive response to functional
protrusion

Studies by Petrovic & Stutzmann
Petrovic,Stutzmann-1972,1974,1975
Lateral pterygoid muscle apparently plays
a regulating role in the control of condylar
cartilage’s growth rate
Stutzmann-1972
Retrodiscal pad apparently has a mediator
role in the efforts of the LPM to control condylar
growth www.indiandentalacademy.com

Interaction b/w STH, Somatomedin,
Testosterone & LPM activity on the
condylar cartilage growth rate

Primary cartilage Secondary cartilage
Diff.chondroblasts
Matrix secretion
Not influenced by local
factors
Subjected to general
extrinsic factors
Prechondroblasts
No matrix
Influenced by local
factors
Local extrinsic factors

Nature of cells of secondary cartilage
Petrovic,Stutzmann-1976,1982

Role of LPM & Retrodiscal pad
in condylar cartilage growth

Inhibition of chondroblast differentiation
Interruption blood supply from LPM &
retrodiscal pad
Periodic forward repositioning
Best procedure for eliciting supplementary
lengthening of the mandible

Christine Mills et al,AJO-1998
Slight inhibition of forward maxillary growth
Mandibular length increased by 6.5 mm in Rx
group ( 2.3 mm in control group)
Uprighting of u/incisors
Distalization of u/molars
Vertical movement of l/molars
(Twin block)

Rabie et al, AJO-2001
Cellular changes in glenoid fossa &
amount of bone formation
Increased bone formation in the glenoid
fossa
Highest level of new bone formation-post
region of fossa
Orientation of mesenchymal cells in the
post. region in the direction of pull

Expression of Sox 9, type II collagen
Sox 9 Transcription factor
Differentiation of mesenchymal cells to
chondrocytes
Type II collagen
Synthesized by chondrocytes
Forms the framework of cartilage matrixwww.indiandentalacademy.com

Growth Treatment
Sox 9 Day 9 Day 5
Type II
collagen
Day 11 Day 7
Functional appliance therapy accelerates condylar
growth by speeding up the entry & progression of cells
into the process of chondrogenesis

Replicating mesenchymal cells in condyle &
glenoid fossa
During growth
Condyle – Posterior region
gl.fossa - Anterior region
During forward positioning
Condyle & fossa – Posterior regionwww.indiandentalacademy.com

Functional appliances are useful where
dysfunction has played a role in the etiology
of the malocclusion. Generally in functional
class II problems with posterior displacement
and functional deep overbite problems with
large interocclusal spaces, functional
appliances have good prognoses for successful
therapy.
Conclusion

The possibility of growing the mandible with
the functional appliances still remains an
issue of controversy. Probably more
research clinically and at the molecular
level is necessary to conclude.

Colin Nelson,AJO-1993
Compared Frankel & Harvold activator
Two measurements
Ar-Pg – Increased in both groups
Co-Pg – No significant difference
Ar point
changes with condylar positionwww.indiandentalacademy.com

Controversies surrounding the efficacy of functional appliance

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