Functional appliances almuzian

Functional Orthodontic Appliances/Growth Modification Appliance/Myofunctional Appliance

Mohammed Almuzian

2013

List of the contents

Table of ContentsDefinition..............................................................................................................................................

History...................................................................................................................................................

Classification.........................................................................................................................................

I. According to mode of action......................................................................................................

II. According to mode of retention.................................................................................................

III. Hunt’s Classification..............................................................................................................

Indications.............................................................................................................................................

Problems with functional appliances.....................................................................................................

1. Rebound of overjet........................................................................................................................

Aetiology...............................................................................................................................................

Solutions................................................................................................................................................

2. Incisor proclination........................................................................................................................

Studies...................................................................................................................................................

Solutions................................................................................................................................................

3. Lateral open bite............................................................................................................................

Compliance with different type of functional appliance........................................................................

Problems with functional appliance studies...........................................................................................

Effects and Mode of action....................................................................................................................

Dentoalveolar modification...................................................................................................................

Skeletal effect......................................................................................................................................

Soft tissue effect..................................................................................................................................

Habit breaker.......................................................................................................................................

Comparing the functional appliance regarding the skeletal effect.......................................................

If there are no skeletal changes by functional appliance, so, why the functional appliance is still recommended highly in growing patient? And what is the factor influencing the timing of treatment with myofunctional appliances..........................................................................................

Factor influencing the Choice of appliance of myofunctional appliances............................................

Types of myofunctional appliances.....................................................................................................

I. Myofunctional appliances for treatment of Deep overbite...........................................................

II. Myofunctional appliances for treatment of openbite....................................................................

III. Myofunctional appliances for treatment of Class III................................................................

Frankel FR3.........................................................................................................................................

Class 3 twin-blocks..............................................................................................................................

IV. Myofunctional appliances for treatment of Class II.................................................................

a. History of TB...............................................................................................................................Mohammed Almuzian, 2013 1

Functional Orthodontic Appliances/Intraoral Growth Modification Appliance/Myofunctional Appliance

Definition A removable or fixed orthodontic appliance which use or eliminate the force

arising from the masticatory, facial muscles & peridodontium to alter the skeletal

and dental relationship. (Mills, 1991).The term “myofunctional appliance” is

preferable as they all depend for their action upon the activity of the orofacial

musculature.

History Kingsley in 1879 used the bite jumping appliance.

Inclined bite plane first used in 19th century In Spain by Catalan.

Monobloc appliance developed 1902 Pier Robin

“Norwegian system “ Andreasen appliance (activators), developed from

URA retainers used with inclined bite planes and mandibular lingual

extensions when Andreasen prescribed it to his daughter during her long

school holidays in Norway. (Andreasen and Haupl,1936)

Balter Bionator 1950

Frankle appliances 1966

TB appliances were originally described by William Clark (1982 and

1988).

Classification

I. According to mode of action by Vig and Vig 1974.1.Myotonic: Work by passive muscle stretch through large mandibular opening

(8-10mm). eg. Harvold

2.Myodynamic: Work by stimulation of the muscle activity with medium

mandibular opening (<5mm). eg Andreasen, Bionator, MOA

Mohammed Almuzian, 2013 2

II. According to mode of retention 1.Tooth borne:

Passive tooth borne eg Andreasen, Bionator

Active tooth borne eg twin block, Herbst.

2.Tissue borne eg Frankel

III. Hunt’s Classification1. Removable: good for deep overbite / short face cases. Andreasen, Bionator,

Harvold, MOA, Function Regulator.

2. Removable functional headgear appliances: good choice in high angle cases,

CTB (Clark, 1982) with HG, Van Beek, Bass appliance with HG, Teuscher

or headgear activator Teuscher appliance (HATA)

3. Fixed: can be classified as either

A. Flexible (Flexible Fixed Functional Appliance – FFFA) AdvanSync

B. Rigid (Rigid Fixed Functional Appliance – RFFA) Dynamax

C. Hybrid types- Herbst (Pancherz)

Indications

1.Interceptive treatment for trauma: Functional appliances are frequently

advocated for early treatment to reduce the overjet early which subsequently

might reduce trauma. This had been disapproved by (Kurlock 2004)

2.Psychological advantages in young patient: Functional appliances are

frequently advocated for early treatment to reduce the overjet early which

subsequently might reduce teasing problems. (O’Brien 2003)


3.Orthopaedic treatment

Correction of AP in class II division 1 malocclusions or class II D2 with

incisors decompensation (for more details see below)

CL III cases.

AOB like Frankle 4

Mild degree of facial asymmetry by using hybrid appliance

4.Compromise treatment: Some cases are not suitable for fixed appliance

treatment because of, for example, poor oral hygiene, so the functional

appliance can offer an acceptable degree of occlusal and facial improvement.

5.Anchorage reinforcement: Turning a class II case into an easy class 1 case

6.Habit breaker (digit sucking) combined with one of the above problems.

7.Patient with gonial angle less than Franchi and Bacceti 2006. A Class II patient at

the peak in skeletal maturation (CS 3) with a pretreatment Co-Go-Me° smaller than

125.5° is expected to respond favorably to treatment

Correction of AP in class II division 1 malocclusions or class II D2 with functional appliances

'Classic' functional appliance cases is:

1.Growing patient

2.Motivated patient

3.Moderate to severe Class II D1 or class II D2 with incisors decompensation

4.Normal or low MMPA (average or increased OB)

5.Slightly proclined upper teeth.

6.Slightly retroclined lower incisors.

7.Well aligned or minimal crowded arches.

Class II cases not suitable for functional appliances

1. Non-growing patient


2. High angled cases, posterior mandibular rotation, AOB

3. Cases with proclined LLS or retroclined ULS

4. Cases which can be treated by conventional fixed appliance on extraction or

non-extraction basis.

Problems with functional appliances1. Rebound of overjet

2. Lower incisor proclination

3. Lateral open bite

In details

1.Rebound of overjet

Aetiology

I. A rebound of condylar position caused by atrophy of hyperatrphyed meniscus

II. Reduction in the activity of protractor muscle (lateral Pterygoid muscle)

III. Uprighting of ULS or LLS. LLS relapsed more.

IV. Unfavourable growth

Solutions (DiBiase and Fleming 2007) wrote a comprehensive review article about this topic. They

mentioned the following as a transition technique:

Technique Advantages Disadvantages1. Over-correction. To counteract the relapse2. Reinforcing

anchorage Headgear and palatal arches

To control molar buccal tipping during alignment stage.

3. Maintaining postured bite by inclined URA or clip over URA (Plint clasp appliance). The bite plane should be 8mm deep and 70 degree inclination

Maintain transverse correction

Allow settling of occlusion Maintain class II effect.

Increased proclination of LLS.

Interference with the placement of FA.


(Sandler and DiBiase, 1996).

4. Night wear appliance. Advantages: Better to predict rebound, Good time for postured

condyle to adapt Good settling of occlusion, Maintain transverse

correction5. Integration of the

functional appliance with the fixed appliance until rigid AW in place.

Good settling of occlusion, Maintain transverse

correction Quick methods

But this needs a modification in the functional appliance to avoid interference with FA.

6. Early light class II elastics at an early stage on light wires to keep overjet controlled.

Further proclination of LLS and retroclination of ULS.

Extrusion of LBS cause reduction in the OB

Lingual tipping and rolling of the lower molars due to poor rigidity of the NiTi AW.

7. Appliance prescription

(MBT is preferred because It correct LLS and ULS

inclination The zero tipping of the U6 and

U3 cause less rebounding effect

Increase palatal root torque of buccal segment will compensate for tipped molar due to expansion.

Lastly the reduce lingual crown torque of L6 to counteract the lingual rolling when class II elastic is used

8. The use of fixed functional appliance to avoid the transitional phase

DynamaxFixed TBAdvanSyncHerbst

9. Last option is the immediate transition without retainer.

It is a short treatment option Difficult to predict rebound,No time for postured


condyle to adaptNo settling of occlusion

2.Increase in the incisor inclination (upper retroclination and lower proclination)

Lower incisor proclination is a feature of almost all functional appliance

treatment. (Approximately 8-15 degree)

Studies

Studies show a wide range of proclination with any given appliance and a

wider range between different appliances.

• Appliances which are tooth-borne, such as the Herbst appliance, seem to

produce greater proclination (average 3.2 mm or 11 degrees in Koutsonas and

Pancherz, 1997).

• The Bass appliance which places no direct pressure behind the lower incisors

can produce very little labial incisor movement, albeit with slower overjet

reduction. Bass 2006

• Lund and Sandler (1998), reported average proclination of 8+7 degrees using

TB.

Solutions

1.Lower labial cap of acrylic on their twin blocks and reported average

proclination of 5.2+3.9 degrees (Young & Harrisson 2005). However this

might cause extensive decalcification in poor OH (Dixon 2005).

2.Trenouth & Desmond (2010) used Southern end clasps on the lower incisors

and reported almost no lower incisor proclination.

3.Other functional appliance like Dynamax


4.Headgear with functional appliance

5.Relief to the acrylic lingual to the lower incisors (Ball and Hunt, 1991)

6.Avoidance of labial bows in the upper arch

7.Extending the lower lingual acrylic as posterior as possible

8.Incremental advancement

9.Short time use or avoidance of class II elastic

10.Overcorrect the OJ and then use class III elastic

11.MBT prescription

12.Extraction

3.Lateral open bite

1.Lower incisor capping to prevent incisor overeruption.

2.Upper incisor capping or 'torquing' spurs to prevent incisor overeruption.

3.Grinding from the functional appliance to allow eruption. However this might

encourage the lower molars to erupt more mesially causing lower premolar

crowding as well as leading to more LLS crowding.

4.Night time wear. However it is important to mention that one intriguing

thought arises from work showing by Lee and Proffit (1995), that nearly all

human tooth eruption occurs between 8 pm and midnight. Should we get our

patients to wear the twin block just in the mornings once the overjet is

reduced and the remaining posterior open bite can usefully settle at night

when teeth erupt?

5.Stop and wait until settling of the occlusion

6.Steep and deep URA.

7.Other type of removable functional like Dynamax.

8.Claim that fixed functional produce less open bite problems


9.Fixed appliance

Compliance with different type of functional appliance

In general the TB fail in 1 out of 5 patients

Failure rate

TB in pre-adolescent 18% O’Brien 2003TB in adolescent 25%

33%

9%

O’Brien 2003 b (with herbest)Lee et a 2007

Incremental and one go advancement TB

The first one has half of the failure of the latter

Bank 2004

Fixed TB 3% Read, 2001Dynamx 9% Lee et a 2007Dynamx 84% Bader Thiruvenkatachari,

2010Herbst appliance 13% O’Brien 2003Frankle appliance 42% in female and 24%

in maleGhafari 1998

HG 5% for female and 25% for male

Ghafari 1998

Schafer K, Ludwig B, Meyer-Gutknecht H, Schott TC. Quantifying patient adherence during active orthodontic treatment with removable appliances using microelectronic wear-time documentation. Eur J Orthod 2015;37:73-80


Removable appliances are a common treatment modality used in both active and retentive phases of orthodontic treatment. It is well known that patient adherence is imperative for optimal therapeutic success. Until recently, it has been almost impossible for orthodontists to objectively evaluate how consistently patients were adhering to their prescribed wear times. The aim of this study was to quantify the adherence of active removable appliances during the first 3 months of treatment. This was a multicenter, prospective cohort study that evaluated how wear time was influenced by age, sex, device type, location of treatment, and health insurance status. One hundred forty-one patients were divided into 3 age groups: 7-9, 10-12, and 13-15 years. Each patient was treated either in one of 3 private practices in Germany or at the University Hospital of Tubingen, Germany. A temperature-sensitive microsensor, TheraMon Sensor, was placed in a standard activator, a Class III activator, or a maxillary expander, and the stored data were transferred at routine visits. The overall median wear time was 9.7 hours per day compared with the prescribed wear time of 15 hours per day; only 7.8% of the patients reached the prescribed 15 hours. Statistically significant differences were seen based on sex, age, location, and health insurance. Wear time decreased as age increased, with the youngest patients wearing their appliances for a median of 12.1 hours per day, and the oldest wearing them for 8.5 hours a day. Girls wore their devices longer in each age group by 1.3 hours. Wear times were significantly higher in patients with private health insurance during the first 3 months and in each month separately. There was no significant difference between device types.

Problems with functional appliance studies1.Small samples

2.No controls:

No controlling to differentiate treatment effect from normal growth

effect.

If involved historic control it is considered invalid for the today

population

Also the randomization is absent which would not involve the bias in the

confounding factors.

3.Retrospective so the best cases tend to be selected.


4.Unmatched samples for age and gender

5.Different appliances

6.Different operators

7.Different lengths of study

8.Inaccuracies in measurement

9.Most based on cephalometric.

10.Animal studies may not be relevant to humans. This is because:

Animal are different species

Animal has no class II problems

Unrealistic prolong use of functional in animal

On the other hand, the retrospective are weak studies because:

Only good cases were shown

Only enthusiastic clinician are involved

So the RCT are the gold standard

Mode of action Stretch and activate the muscle of mastication and facial muscle

Stretching of periosteal

Relieve soft tissue effect (Frankle appliance)

Disocclude the occlusion

Effects

Effect With Against

Dentoalveolar modificationWe should employ the knowledge that a large proportion of their effect is via

upper incisor retroclination and distal movement of upper molars

1. ULS retroclined


2. LLS proclined

3. Distalization of U molars.

4. Mesilaization of L molar

5. Inhibition of the eruption of upper posterior teeth

6. OB: Differential eruption of the teeth by encouragement of the eruption of

lower posterior teeth which cause reduction in the OB and increase LAFH.

7. Transverse expansion if screw is incorporated

The evidences are:

1. Tulloch et al 1997

2. Tulloch et al 1998

3. Lund and Sandler 1998

4. Keeling et al 1998

5. Ghafari 1998

6. O’Brien et al 2003

7. Dolce et al 2007

8. O’Brien in 2009

These dental effects are due to the stretching of the muscle of mastication and facial

tissue as well as alteration of the soft tissue balance when the mandible is postured.

Skeletal effectEffect With Against

Redirection of condylar

growth (altering growth

direction, mainly vertically)

which is more stable over a

long period of time

Mills, 1991

Deflection of ramal formRemodeling of the

gonial angle in


response to altered

muscle activity and

tone in the

pterygomasseteric

sling has been found

in animal

experiments

(Woodside et al,

1983; Joho, 1968,

1973; Altuna, 1979;

Harvold, 1960) and

human functional

appliance studies

(Harvold, 1960;

Hutchison, 1982).

Condylar position changes

within the fossa results

mainly due to condyle

remodelling and glenoid

fossa remodelling

Petrovic 1990 suggested

that the functional would

increase the activity of

the lateral pterygoid

which helps in

enhancing growth of the

condyle by increasing

the number of

proliferative cells.

An MRI study by Ruf and

Pancherz (1998) showed no

mean change in condylar

position within the fossa

Mandibular effect:

Enhancement of mandibular

growth (True condylar

growth). It is probable that

Animal Studies,

McNamara 1987

showed that the

mandible of monkeys

Human Studies on long

term

1. Weislander (1993)

showed 2mm skeletal


an average 1-2 mm of extra

short-term mandibular

growth can be obtained.

There is a great individual

variation regarding this

issue. This is clinically

worthwhile, but it would not

be sufficient to obviate

orthognathic surgery in those

cases deemed to require it

before the start of treatment.

The increasing evidence is

that the long-term gain in

mandibular growth is very

small or non-existent.

grow by 5-6mm more

than control.

changes lost after 2

years

2. Keeling et al (1998),

Bionator, one year

after active treatment,

all changes lost.

3. The long-term results

of the groups in the

RCT by Keeling et al

have been published

(Dolce et al 2007)

and they show no

long-term differences

4. Tulloch et al (1997)

using Bionator

showed a small (0.6

degrees/year)

enhancement of

mandibular growth in

the short term, then

Tulloch et al (1998)

none in the after 1

year

5. Tulloch et al (2004)

the growth

modification group

were lost.

6. O’Brien et al (2003)

using TB, growth in

Human Studies on long

term, Lund and Sandler

(1998) they found

cephalometric evidences

of mandibular growth

when measured as

Articulare-Pogonion but

could not attribute this

growth or just

repositioning.


the mandible of

approximately1.2

mm per year. This

small change was

stable 12 months

after treatment.

7. O’Brien in 2009

long-term results

there were no

differences of

skeletal pattern

8. Harrsion 2007

Maxillary skeletal changes:

Restriction of the maxillary

growth. An average 1-2 mm

of long-term maxillary

restraint seems possible,

although many studies fail to

find this. There is some

evidence that this does not

relapse after active

treatment, but may continue

and even increase.

on long term,

The study by

Weislander (1993)

showed that

maxillary growth

restraint actually

increased relative

to controls after

the end of active

treatment using a

combined

Herbest-HG

appliance.

O’Brien et al

(2003) found

0.88mm restraint

in the TB gp.

No significant maxillary

restraint, with Frankel

appliance Keeling et al

(1998) or with the modified

Bionator (Tulloch 2004).


3. Soft tissue effectIn general, Functional appliances are said to modify

the neuromuscular environment of the dentition and

associated bones. Adaptive processes may include:

Elongation of muscle fibers (McNamara, 1973; Golspink, 1976) or tendons (Muhl and Grimm, 1974).

Migration of muscle attachments along bony surfaces (McNamara, 1973; Symons, 1954; Van der Klauuw, 1963; Rayne, 1975)

Changes in muscle dimensions due to bone displacements and rotations (Altuna, 1977, 1979, 1985; McNamara, 1973).

Certain muscles of mastication may adapt by changing the proportion of specific muscle fiber types and fiber diameters (Altuna, Herbert and Woodside, 1983).

1. Muscles of face: Frankel reported to restrain the

muscles of face

2. Muscle of mastication: Other appliances

stretching the muscle of mastication specially

lateral pterygoid. So the force will be

transmitted to the dentition causing a

dentoalveolar changes, condylar adaptation and

growth

3. Tongue: functional appliance can remove tongue

adaptively.

4. Lip muscle: Functional appliance can eliminate

lip trapping which is a cause of proclination


All these effect produce dental and skeletal changes by

altering position of balance (Bishara & Ziaja, 1989).

The soft tissue changes include: (Sharma and Lee

2003, 2005).

1. Increased commissure width

2. Increased LFH,

3. Retrudes the upper lip.

4. Increased lower lip height & projection,

5. Increased projection of ST pog

Effect on Oropharyngeal airway: Özbek, (1998) suggested that mandibular deficiency may be a factor in reduced oropharyngeal airway (OAW) dimensions and related impaired respiratory function. The purpose of the study was to evaluate the use of functional-orthopaedic devices in increasing OAW dimensions in children with Class II skeletal patterns (ANB>4) and clinically deficient mandibles. Comparisons were made between two groups, one comprising 26 treated patients and the other comprising 15 controls. Compared with controls, OAW dimensions increased significantly in treated patients, especially those with sagittally smaller and more retrognathic maxillomandibular complexes and smaller OAW dimensions.


4. Habit breaker: By occupying the space which might be a space for the digit and or tongue in case of habit.

NB:Summary of the evidences:

The increasing evidence is that the long-term gain in mandibular growth is very small or non-existent. It is probable that an average 1-2 mm. of extra short-term mandibular growth can be obtained. This is clinically worthwhile, but it would not be sufficient to obviate orthognathic surgery in those cases deemed to require it before the start of treatment.

An average 1-2 mm of long-term maxillary restraint seems possible, although many studies fail to find this. In contrast to the mandibular effect, there is some evidence that this does not relapse after active treatment, but may continue and even increase. Headgear may well be more effective for maxillary restraint.

We should remember the large variability of growth - both with and without treatment.

Some uncertainty remains about the influence of the pubertal growth spurt on growth enhancement.

We should employ the very large occlusal benefits of functional appliances in the knowledge that a large proportion of their effect is via upper incisor retroclination and distal movement of upper molars. 75% dentoalveolar and 25% short term skeletal changes.

We should keep in mind that the skeletal changes might be relapsed after finishing FA treatment. For example a patient use TB to correct class II D1 malocclusion, in general he will gain a lot of dentoalveolar changes as well as some skeletal changes. According to the evidence the skeletal changes will lost in average two years after functional treatment. So this is one of the causes of relapse after treatment as well as one of the reasons for continuous use of active retainer in a form of steep and deep or activator. The aims of using it after active treatment are to enhance more dentalveolar compensation when the skeletal changes relapsed.

Individual variation in effectsWoodside (1998) has outlined “prominent reasons” for individual variation in results:

Patient compliance


Night-time wear vs full-time wear. Full-time wear requires appliance designs that will not unduly affect the patient’s facial appearance and speech.Wavelike fashion of mandibular growth –accelerations followed by quiescent periods. If treatment is applied during a quiescent period, significant orthopaedic changes may not occur.Improper diagnosis. Severe cases are probably future surgical cases, we can’t expect growth control to exceed certain limits.Type of mandibular rotations

Problems with Cephalometrics in Measuring the Orthopaedic Effect: [Aelbers and Dermaut, 1996]

A cephalogram is a magnified two-dimensional image of a 3-D object. Maxillary and mandibular lengths are often used to show possible

orthopaedic effects. Condylion, gnathion and pogonion are mandibular points used, however, it is often difficult to define the head of the condyle on a cephalogram. Results have indicated that the open mouth method does not significantly change the recognition of condylion, others have found improvement in landmark identification.

Articulare is sometimes used because of the high reproducibility of this landmark. Articulare does not, however, show full mandibular length, and a change in the amount or direction does not necessarily create the same positional change of articulare. Anterior positioning of the condyles out of the glenoid fossae could be interpreted as an increase in mandibular length.

Maxillary length can be measured using PTm point, spinal point (ANS) or point A. These landmarks can not be accurately identified. Point A is influenced by dental changes. Because most functional appliances induce a large dentoalveolar change, point A has a limited value to evaluate orthopaedics.

Angular measurements, such as SNA, SNB and ANB, may increase or decrease when the incisor position changes, although no skeletal change occurs, rendering the results invalid (Woodside, 1998).

Statistical significance may not necessarily correlate to clinical significance. Small statistically significant amount may be clinically insignificant in the total malocclusion correction (Woodside, 1998).

Implant studies are limited by ethics and small sample sizes.


Comparing the functional appliance regarding the skeletal effect1.Fixed and removable functional appliances: (Pacha, Fleming and Johal a

systematic review 2015

There is little difference in the dental and skeletal effects of fixed and

removable functional appliances.

Most of the correction of the overjet is by dento alveolar movement, but there is a small amount of skeletal change (1-2mm).

There is greater co-operation with fixed functional appliances but this is not 100%. There is no such thing as non compliance orthodontic treatment!

Only one study reported on patient centred outcome and these should be

included in all trials in addition to some cephalometric and dental

measurements.

2.TB versus Bionator by Harrsion 2007 statistic difference in the reduction of

ANB when TB compared to bionator, however, there was no difference in

regard to the final OJ.

3.Comparison of Herbst with twin-block appliances in preadolescent patients,

O’Brien 2009, Treatment with the Herbst appliance resulted in a lower failure-

to-complete rate for the functional appliance phase of treatment (12.9%) than

did treatment with Twin-block (33.6%). Herbest appliance where more

effective in reducing OJ than TB. However, there were no differences in

treatment time between appliances, There were no differences in skeletal and

dental changes

4.Comparison of Twin-block and Dynamax appliances. ,

Lee et al 2007, similar compliance rate. More breakage with Dynamax. Forward

movement of the chin and Pog are similar. More vertical skeletal changes with

TB (6mm compared to 5mm), ANB changes in TB 2 degree and in Dynamax 1

degree.

Thiruvenkatachari Bader, 2010, The incidence of adverse events was greater in

the Dynamax group (82%) than in the Twin-block group (16%). The Twin-

block appliance was more effective than the Dynamax appliance


Factor influencing the timing of treatment with myo-functional appliances

Dental factors

Growth spurt

Trauma prevention

Psychological factors

Patient compliance

Factors With Against

Dental factors Better to start when the

permanent teeth have erupted for

better clasping of the appliance.

Treatment whilst deciduous teeth

are being shed may pose minor

problems of appliance retention,

discomfort or a delay in the

shedding of deciduous teeth.

Growth spurt

The principle

issue to start

functional

appliance is to

try to

synchronize the

treatment with

pubertal growth

spurt.

Treatment during growth spurt

may cause slight difference from

that earlier or later in that it has

little dental tipping, more skeletal

growth and stable results as well

as better occlusal settling.

Pancherz (1985) and Baccetti

(2000).

Stephens and Houston (1985)

stated that a growing patient

has greater potential for:

Dentoalveolar effect of the

But neither Tulloch 1997

using hand wrist or

O’Brien 2003 using

CVM failed to relate the

skeletal changes to

skeletal maturity.

An important point is

that the growth spurt

cannot be predicted with

clinically useful

accuracy. Even with

longitudinal monitoring

of stature, Sullivan


functional appliance

Overbite reduction

Occlusal settling

Space closure

Maxillary expansion

Distalization or mesialization

of posterior teeth.

All of these make changes by

functional appliance as well as

the second phase fixed appliance

efficiently and fast.

(1983) has shown that

our prediction will still

be more than one year

incorrect in 33% of

cases.

The timing of treatment seems to have minimal impact (0.6 mm) on the treatment outcome (Baccetti, 2009Franchi, 2000)

Trauma

prevention

A definite

potential

advantage of

starting

treatment early

is the reduced

incidence of

trauma to

prominent

upper incisors.

High trauma with increased

overjets >9mm (Todd & Dodd

1983) (45% 10 yr olds with OJ

more than 9mm have traumatised

incisors compared to 27% if the

OJ was less than 9mm especially

if the lip is incompetent. Nuygen

1999 systematic review

However this had be

contradicted by Korluk

in 2004.The same results

by O’Brien 2009. But

the latest Cochrane

review by

Thiruvenkatachari in

2013 confirm the trauma

prevention benefits of

early treatment.


Psychological

factors

Unless for psychosocial reasons

(increase self-concept, reduce

negative experience and improve

self esteem) (O’Brien 2003),

which can result from teasing,

early treatment with functional

appliances is not indicated.

OIIRR In the UNC study (Brin 2003),

the percentage of children with

more than one incisor with

moderate to severe in the two-

phase group was 5% in the

functional group and 12.5% in

the headgear group. In the single-

phase treatment group, the

incidence was 20.4%.

Does severe OIIRR

affect the longevity of

the affected teeth? In a

long-term evaluation

(average of 14.1 years)

of longevity of teeth

with severe OIIRR (>

1/3 loss of root length),

it was found that even

the most severely

affected teeth were

functioning in a

reasonable manner many

years after orthodontic

intervention.( Remington

1989) This is not

surprising because the

apical portion of the

tooth plays only a minor

role in overall


periodontal support. It

has been reported that 3

mm of apical root loss is

equivalent to 1 mm of

crestal bone loss

(Kalkwaf 1989).

Patient

compliance

The studies by O’Brien et al

(2003) showed a significantly

lower failure-to-finish rate in the

younger patients when treated by

the same operator with the same

appliance. Similarly, the study by

Banks et al (2004), found that

patients younger than 12.3 years

were three times more likely to

complete functional treatment

with twin-blocks.

Summary

1. Dental factors are important. We usually want to start treatment as soon

as the eruption of the permanent teeth permits and this is in the late

mixed dentition.

2. Enhancement of growth is on average small and seems to be only

marginally related to the pubertal growth spurt. However, it is probable

that regardless of growth enhancement effect, treatment is faster rapid

growth. Treatment during growth spurt is aiming to

a. Borrow the potential mandibular growth when needed

b. Provide a better environment for dentoalveolar compensation

c. Disoccluding the unfavourable occlusion that might interfere with

the potential growth leading to dysmorphic compensation (Kim and


Nanda 2002, You 2001 using Burlington sample).

However there is no evidence comparing adolescent patients with TB

treatment to control because of the equipoise. Again the long term

effect involve limited AP changes and more attractive profile

(O’Brien 2009 a & b) with increase VH, dental and occlusal changes

and favourable ST changes for low angle cases.

3. An early treatment in large class 2 discrepancies may be moderately

significantly advantageous in terms of dental trauma

4. An earlier start than this in large class 2 discrepancies may be

advantageous in terms of psychosocial benefits

5. Cooperation with functional appliances is better before 12.5 years of age

Factor influencing the Choice of appliance of myofunctional appliances1.Patient factors

• Patient compliance

• Type of malocclusion

• OH

• Preference

2.Clinician factors preference

• Familiarity

• Laboratory facilities

• Available evidences


Types of myofunctional appliances

I. Myofunctional appliances for treatment of Deep overbite

1.The Anterior Bite Plane (ABP)

It is the simplest form of a myofunctional appliance. Its types;

1.Upper horizontal bite-planes

2.Upper inclined bite-planes

3.A lower inclined bite-plane can be used in deep bite class III cases.

II. Myofunctional appliances for treatment of open bite Frankle IV Intrusive splint The oral screen

A. Design

This very simple functional appliance lies in the

labial vestibule. The oral screen has no place in

modern orthodontics.

B. Indication:

1.It has been used to discourage thumb-sucking

and to correct the associated malocclusion.

2.Prevention of trauma during contact sport activity.

3.It has also been used for lip training in patients with incompetent lips.


III. Myofunctional appliances for treatment of Class III

1.Frankel FR3

2.Class 3 twin-blocks

Frankel FR3

1.Not commonly used

2.Holding away of the soft tissues from the upper incisors would stimulate

maxillary growth through stretching the periosteum.

3.Most of the effects are dentoalveolar.

Class 3 twin-blocks

1.Not commonly used

2.In this case, the mechanism is a reversal of the conventional orientation of

interlocking blocks used to posture the mandible forward in class 2 cases.

3.Most of the effects are dentoalveolar.

IV. Myofunctional appliances for treatment of Class II 1. Lip bumper

2. The Andresen appliance (or activator)

3. The Bionator

4. Harvold appliance

5. The Palatal and Labial Medium Opening Activators (MOA)

6. The Frankel appliance

7. The Intrusive Myofunctional Appliances

8. Teuscher appliance

9. Hybrid appliance

10.Mini-block appliance

11.Twin-block type appliances


12.Fixed twin block

13.The Herbst appliance

14.The Dynamax appliance

15.The AdvanSync appliance

16.Fixed magnetic appliance

In details

The Andresen appliance (or activator)

The activator was popularized by the publication of Andresen in 1936. It is a

loose appliance.

A. Mode of action:

It is loosely fitting act as an exercise appliance resulting in passive tension of

the muscle and moderately displaces the mandible forwards (passive tooth

borne)

Moderately bite opening (Myodynamic) <5mm

B. Indications: Useful in mild to moderately severe class II cases with no

crowding

C. Instruction for Use: The patient is

instructed to wear the appliance for

10-12 hours in every 24: this will be at

night with 2-4 hours' wear in the

evening

D. Design:

Upper labial bow.

Upper and lower baseplates sealed together.

The acrylic caps the lower incisor edges to prevent them from over erupting

In the upper arch these slope guided the teeth distally and buccally as they

erupt with the opposite in the lower arch.


It is possible to reactivate the first appliance by trimming it away from the

lower teeth so that wax can be added to register the more advanced position

of the mandible.

E. Advantage of Andresen over TB (Bennet 2001)

1.Robust

2.Simple and cheap

3.Part time wear cause less dental effect and more skeletal

4.Easy to wear because not complicated and only 2-4mm opening of the bite

5.No lateral OB because eruption is allowable during its use and there is no

intrusive force on the post teeth, so less time for transient or supportive stage

The Bionator

A. History:

Advocated by Balter Bionator 1950.

This appliance is derived from Andresen's activator

but is greatly reduced in bulk.

Although it has generally been neglected outside

Germany.

B. Mode of action:

Loose appliance (passive tooth borne)

Moderately displaces the mandible forwards & moderately bite opening

(Myodynamic) <5mm

C. Indication:

Useful in mild to moderately severe class 2 cases with no crowding.

D. Instruction for Use:

Worn full time apart from during meals and sports.

E. Design

Similar to the activator except:


The palatal acrylic coverage is replaced by palatal loop 1.25mm to encourage a

forward posture of the tongue and mandible.

Upper posterior teeth occlusal coverage while the lower are free to erupt

except the LLS which are capped.

The vestibular bow 0.9mm contacts the upper incisors but is clear of the buccal

teeth by 2-3 mm to allow expansion.

F. Evidences

The study by Tulloch et al 1997 (class II D1 OJ 7mm, HG, Bionator or CG for 15

months) concluded that the bionator produced some mandibular change, whereas,

with the headgear, there was some maxillary restraint. In the TG (HG or Bionator)

the improvement in the ANB in 70-80% while no improvement in 20%. In the CG

no improvement 50%, improvement 30% and worsening 20%.

Then Tulloch 1998 followed the patient and found that skeletal improvement is

lost after 1 year.

Keeling et al 1998 (HG/Biteplane, Bionator, CG, OJ 7mm for 2 years or until

class I achieved) suggested that a headgear biteplane combination resulted in no

restraint of the maxilla but forward positioning of the mandible while bionator

resulted in some mandibular growth that lost after 1 year follow up.

Harvold appliance

A. History: The Harvold appliance is

derived from the activator of Andresen.

It is similar to MOA except the amount

of opening is more.

B. Mode of action:


The mandible is advanced a few

millimetres less than the maximum the patient can achieve.


It is opened to give an interocclusal clearance of 10-20 mm measured at the

premolars. This is a myotonic appliance

C. Indication: Useful in mild to moderately severe class 2 cases with no

crowding and deep anterior bite due to deep COS.

D. Instruction for Use: 24h except meal time

E. Design:

The upper labial bow

Upper occlusal coverage

Adam on U6 and U4

Lower incisor capping

Medium Opening Activators (MOA)

A. Mode of action:


Moderately displaces the mandible

forwards

Moderately bite opening (Myodynamic)

<5mm

Indication: Useful in mild to moderately severe

class 2 cases with no crowding and deep anterior

bite due to deep COS.

B. Instruction for Use: 24h except meal time.

C. Design:

The upper labial bow

Upper occlusal coverage

There are Adams cribs and occlusal rests present on the upper first

permanent molars and first premolars.

Lower incisor capping


The Frankel appliance

A. History : This appliance, named after its

originator, Rolf Frankel of East Germany,

B. One of its advatages is using it in a mixed

dentition.

C. Mode of action &Design:

It is a myodynamic loose tissue born

appliance, so it activate the lateral

pterygoid muscle.

Frankel termed it a function regulator (FR) because it is intended to correct

functional anomalies in the circumoral musculature, which he holds

responsible for crowding and other aspects of malocclusion

The buccal shields extend to produces 'periosteal stretch ‘and the teeth are free

of muscular pressures on the buccal but not on the lingual surfaces.

The lip pads (Pelotte wire) are also intended to

a.Produce periosteal stretch

b.Alter and control lower lip activity,

c.The lip pads eliminate any trapping of the lower lip behind the upper incisors.

d.When the lip is displaced by the lip pad, it will force the appliance posteriorly

causing some headgear effect.

The lingual pad contacts the alveolar mucosa on the lingual surface of the

mandibular alveolar process, but it is clear of the teeth. Thus a forward

mandibular posture is induced without any protrusive force on the lower

incisors.

D. Indication

1.Frankel 1a – Class 1

2.Frankel 1b – Mild Class 2/1

3.Frankel 1c – Moderate Class 2/1

4.Frankel 2 – Class 2/2


5.Frankel 3 – Class 3

6.Frankel 4 - AOB

E. Instruction for Use: the patient should wear it full time, except for meals and

sport

The study by Ghafari et al 1998 suggested that headgear produces some

maxillary restraint and the Fränkel, mandibular growth increase.

Hybrid functional

Used in the orthopaedic management of occlusal canting in growing patients

(Vig and Vig 1986).

It consists of acrylic block at the side of overgrowth and no block at the

undergrowth site to allow differential eruption of the teeth at the

underdeveloped site.

There is a buccal shield same like the one use in Frankle appliance to allow

arch expansion.

Lip bumper

A. Design:

This is a functional component, occasionally

used in conjunction with a lower fixed

appliance.

B. Indication:

The lip bumper can occasionally be useful in

Class 11, division 1 with lip trap interference.

Distalization of lower molars

Reinforce lower posterior teeth

IO to avoid loss of space after premature loss of primary teeth.

C. Mode of action


Change in muscle balance

Periosteal stretching.

The Dynamax appliance

Advantages

1.Little patient compliant.

2.No need for a postured bite

3.Incremental mandibular

advancement.

4.It can be used with fixed

appliance.

5.Minimal mouth opening - which may increase patient acceptance, especially in

high angle cases with less (the 'goldfish' look).

6.Upper incisor inclination is controlled by torque spring

7.Extra oral traction may be added.

8.Conversely, the posterior occlusal capping helps control molar eruption in

cases with reduced overbite. The aims of the post capping are to

Disoccluding the teeth,

Allow even distribution of the HG force

Prevent and intrude U post teeth.

9.Dynamx show better control of vertical height and insignificant less relapse

than TB (Lee 2007)

10.Little LLS proclination because the appliance works by avoidance's reflex

theory which might cause little LLS proclination.(Myodynamic passive tooth

borne appliance).

Disadvantages

It has higher failure rate than TB (two times more failure rate).

Thiruvenkatachari, 2010.

As well as more difficult to construct.


The Herbst appliance

A. History: It was first described by Dr. Herbst and popularized by Pancherz

1979.

B. Design:

Fixed functional.

Bands on upper and lower 6’s and 4’s.

Palatal bar and lingual bar.

Telescopic arms form upper 6’s to lower 4’s.

C. Advantages

According to O'Brien study in 2009, Herbst was superior to Twin Block when

we measured:

Speech interference.

Disturbance of sleep.

Influencing school work.

Feelings of embarrassment.

Better success rate than Twin Block.

It can be used with fixed appliance. Recently a Flip-Lock Herbst

assembly with the 'male' attachments welded to rectangular tubing, which

is slid over a rectangular archwire. This mechanism is very simple to

install and to date is encouragingly robust.

D. Disadvantages

1.Expensive.

2.Breaks more significant and mechanical failure of piston assemblies.


3.Cement problem.

4.Removal difficulty.

5.Enamel decalcification.

6.Recommended in the permanent dentition only

7.If joined with FA treatment, it should use when full arch SS in use.

8.Inability to incorporate arch expansion during the functional phase

9.Do not grow mandibles and in contrast to others, there is evidence of sufficient

satisfaction with other simpler functional - in particular the twin-block.

10.More lower incisor proclination

E. Indications

a.Dental Class II malocclusion.

b.Skeletal Class II mandibular deficiency.

c.Deep bite with retroclined mandibular incisors.

d.Pancherz (1995) also recommends its use in post-adolescent patients, mouth-

breathers, uncooperative patients, and those that do not respond to removable

functional appliances

F. Contra-indications

a.Cases predisposed to root resorption.

b.Dental and skeletal open bites.


c.Vertical growth with high maxillomandibular plane angle and excess lower

facial height.

G. Effects of the Herbst Appliance

1.Restraining effect on maxillary growth

2.A stimulating effect on mandibular growth. The long-term effect on mandibular

growth is uncertain and may only have a short-term effect on skeletal growth

pattern (Pancherz and Fackel, 1990).

3.Dento-alveolar changes include lower incisor proclination, upper incisor

retroclination, lower posterior teeth mesialization and maxillary molar

distalization and intrustion. The changes are similar to those produced by high

pull headgear (Pancherz and Anehus-Pancherz, 1993).

4.Vertically, the overbite is reduced. This occurs by intrusion of lower incisors

and enhanced eruption of lower molars (Pancherz, 1995)

5.Hansen et al. (1990) found that the appliance did not have any adverse effects

on the temporomandibular joint (TMJ).

The AdvanSync appliance

A. History: Developed by Terry Dischinger in 2008

B. Design:

This molar-to-molar fixed functional assembly


The name of the appliance therefore reflects that the mandible can be postured

forward synchronously with the start of all the other fixed appliance tooth

movements.

The appliance requires no laboratory work

Molar band separation at one visit permits selection and cementation of the

molar attachments at the next visit.

The telescoping arms have a long range of action and permit good lateral

excursion and are very easily advanced either by means of the alternative

screw position on the lower molars or via C rings which are crimped over the

pistons.

The Intrusive Myofunctional Appliances

As Tulloch points out, there is a widespread belief that children who grow

vertically will respond less well to class 2 treatment, but this is not well

documented or understood. The study by Ruf and Pancherz (1997) found no

evidence to support this view. The “hyperdivergent” cases in fact showed 1

mm. better mandibular response than the “hypodivergent” cases although this

was not statistically significant. This evidence suggests that ‘high angle’ cases

are no reason to avoid functional appliances because of the potential effects on

growth.

These appliances will be discussed below:

1.The Buccal Intrusion Splint (BIS) This appliance consists of an acrylic palatal baseplate which is clear of the

upper anterior teeth and with occlusal capping on the teeth in occlusion.

There are double Adams cribs present on the upper first permanent molars

and second premolars and molar tubes embedded in the occlusal capping

acrylic to accept a Kloehn facebow near the area of maxillary rotation

(premolar area).


There is a midline screw present in the palatal acrylic.

This appliance is used to treat skeletal anterior open bites by intrusion of

the upper buccal segment teeth.

2.The Maxillary Intrusion Splint (MIS)

• This appliance consists of an acrylic baseplate which extends over the occlusal

surfaces of all teeth and onto the incisal surfaces of the upper anterior teeth.

• There are Adams cribs present on the upper first permanent molars and first

premolars, along with a Southend clasp on the upper central incisors.

• There are headgear tubes present within the molar capping

• This appliance is designed to be used for patients with a Class II division 1

malocclusion and a "gummy smile" with an overjet of 6 to 8mm. .

3.The Maxillary Intrusion Splint and Lower Traction Plate (CONCORDE)

• This is a two part appliance which consists of a maxillary intrusion splint as

described above along with a lower appliance.

• The lower appliance consists of an acrylic baseplate with no occlusal or incisor

capping. There are double Adams cribs present on the lower first permanent

molars and second premolars, and a semi-fitted labial bow on the lower

incisors.

• There is a lingual hook on the lingual aspect of the acrylic baseplate to enable

elastics to be attached to the midpoint of the facebow.

• The selection criteria are the same as for the maxillary intrusion splint but these

combined appliances work more effectively at reducing overjet between 9 to

18mm than the maxillary intrusion splint alone.

• This appliance combination can also be used for the treatment of a severe Class

II division 1 malocclusion with a "gummy smile" and an average face height.


4.The Intrusive Activator a.The Van Beek appliance

Described by Pfeiffer (1972).

It consists of a simplified short outer arm

facebow embedded in the acrylic part of the

activator (Myotonic functional appliance)

There is full palatal coverage and fully extended

lingual flanges

There is no buccal channel

300 gms of force/12 hours a day

b.Teuscher appliance

Teuscher (1978)

Basically it is an activator with two

significant design features - torquing spurs

on the upper incisors to prevent retroclination and headgear to produce

more vertical control and anterior restraint on the maxilla

There advancement of 6mm maximum and minimal bite opening

Indicated in high angle class II D1

Newport appliance: same as TB

Mandibular anterior repositioning appliance (MARA): New fixed functional appliance (Rondeau 2002, Pangrazio-Kulbersh et al 2003) consists of metal modules fixed to both first upper molars at right angles to the occlusal plane, and pairs of abutments fixed to the lower molars, which make contact when the jaw is closed, thus rendering it impossible for the patient to bring the dental arches into contact in the distal bite position. Only through active protrusion of the mandible can the modules and abutments be manoeuvred past each other to allow complete jaw closure. The appliance is normally fixed by means of orthodontic bands or temporary crowns, with the wires being guided into a small, welded-on square profile


tube and slight reactivation being achieved by fitting spacers. Ligatures on the metal bows prevent them from slipping out. This appliance can thus be regarded overall as a training device aimed at encouraging the patient to adopt an anterior mandibular position.( Kinzinger 2002)

Fig 1 Intra Oral view of MARA, Pangrazio-Kulbersh et al 2003

Pangrazio-Kulbersh et al (2003) MARA positions the mandible forward into a Class I occlusion. The results of the study showed that the MARA produced measurable treatment effects on the skeletal and dental elements of the craniofacial complex. These effects included a considerable distalisation of the maxillary molar, a measurable forward movement of the mandibular molar and incisor, a significant increase in mandibular length, and an increase in posterior face height (Fig 2). The effects of the MARA treatment were then compared with those of the Herbst and Fränkel appliances. The treatment results of the MARA were very similar to those produced by the Herbst appliance but with less headgear effect on the maxilla and less mandibular incisor proclination than observed in the Herbst treatment group


Fig 2 Skeletal and dental changes by MARA, Pangrazio-Kulbersh et al 2003

A fixed magnetic appliance

Described by McNamara 1998,

This appliance presents a promising mode of improving facial harmony in

patients with Class II, Division 1 malocclusion associated with mandibular

retrusion, increased lower facial height, and increased interlabial gap.

Further research and development of the appliance are advocated.

It is useful in high angle case as the condyle is displaced inferiorly resulting in

increase in the PFH and improving of the MMPA angle.


A fixed magnetic appliance was designed that hinged the mandible open and

exerted an intrusive force on the teeth. Treatment with this appliance resulted

in:

1.An increase in length of the mandible

2.Intrusion of teeth

3.Upward and forward autorotation of the mandible

4.Creation of temporary buccal crossbite caused by the shearing force of

repelling magnets

Miniblock appliance

A. Design:

Same as TB but with

1. Reduced height of block with 90 degree angulation of the step.

2. Gradual advancement 3mm

3. Incisor torque spurs.

B. Advantages:

1. The idea is that gradual advancement will activate lateral pterygoid

muscle, this will achieve better growth.

2. The reduced the visco-elastic force on the teeth by gradual advancement

will cause less teeth inclination.

3. Reduction in the block height will cause the reactive force vector to pass

close to the centre of resistance of maxilla so it cause less rotation of maxillary

plane and then less increase in the facial height.

4. The benefit of the incisor torque spur is controlling of incisor inclination

C. Evidences

Two reports of a RCT study (Shrarme and Le, 2002, Gill & Lee 2002)

compared the hard and soft tissue effects of a conventional twin-block with a

single large advancement and a modified twin-block named the Mini block.


The only differences of significance were that the conventional Twin-block

retroclined the upper incisors a little more and advanced hard and soft tissue

Pogonion approximately 2mm more on average. Lower incisor proclination

was very similar.

Fixed twin block

A. History: Developed by Mike Read (2001).

B. Advantages

Robustness and possibly patient comfort

Because the two halves of the appliance are not permanently linked together,

the problems of leverage on the fixation points does not arise during

mandibular excursion in contrast to Herbest appliance.

Integration of FA is easy from the start

No lateral open bite.

C. Disadvantages

• OH problems and decalcification

• Need for lower premolar bands to remain securely cemented.

• Not quick and easy for all clinicians to make, fit and adjust as well as

robustness.

• Need technical development and extra experience are continually bringing

improvements.

Twin-block appliances

a. History of TB

• These appliances were originally described by William Clark (1982).

• Survey in UK by Chadwick 1998, 75% of orthodontist are using TB.


b. Indications of TB

1.Cooperative

2.Good OH

3.Class 2 with deep OB with minimal dental compensation

4.Growing patient. Recent prospective studies have found that stage of maturity

of the cervical spine did not influence outcome, O’Brien 2003. The same

result by Trenouth and Desmond 2012 who showed that there is no

correlation between the age and the skeletal effect of TB.

c. Advantage of TB

Harradine and Gale (2000) and Morris et al. (1998)

1.Robust

2.Easy to repair

3.Easy to activate.

4.Relatively well tolerated by the patient because it is two pieces that is not

interfering with function.

5.Expansion is easy by a midline screw

6.Incorporation of auxiliary and headgear is easy.

7.Suitable for mixed or permanent dentition.

d. Disadvantage of TB

1. Require skilled technician

2. Failure rate of 33% (O’Brien)

3. Poor retention of LRA because of shallow inter-proximal dental

undercut in a younger age group.

4. AP change too rapid: This would result in posterior open bites.


5. Teeth tilt excessively: lower incisor proclination and upper incisor

Retroclination

6. It increase the VH which make it worse in high angle cases

7. Short term skeletal effect

e. Design

A. The original design

1.U6s, U4s & L4s delta clasps.

2.labial bow,

3.Ball end clap between lower incisors.

4.45 degree blocks it made from hot acrylic.

5.HG tube.

6.Anchorage

The anchorage component of the TB comes from

AP from reciprocal anchorage of the block as well as HG if it is added

Transversely from reciprocal anchorage around the screw

B. The modified design by Clark in 2010

1. Delta clasps on U4, U6,L4 (Delta clasp is preferable because it will not

open by insertion and removal)

2. No labial arch because the ULS will retraction by the effect of lower lip.

3. Ball end clasp mesial to L3s

4. Midline screw

5. Inclined bite plane of 70-75 with 7-8mm thickness the cover up to half

of lower 5. The reason for this is to prevent interference with clasping of

lower premolars and to allow potential grinding of upper block with

sufficient acrylic remaining as a ramp to support posturing.


6. Interincisal opening in deep bite case should be 2mm and in high angle

case should be 5mm to control lower posterior teeth eruption.

7. Lowe lingual flange extend posteriorly to L6 and L7 for better

anchorage

C. Currently favoured design features

A national UK survey in 2000 by Spicer in Bristol discovered that the

following was the most popular.

1. URA: Cribs on the 4&6, A labial bow, Midline screw, Blocks on 4,5,6,

2. LRA: cribs on 4&6, incisor capping, blocks on 4,5. at a steep angle of 70

degrees to the occlusal plane and should be mesial to the lower 6, permitting

removal of the lower molar crib and grinding of the upper block if accelerated

eruption of these teeth is required.

D. Labial arch

1. In order to maximize the TB effects it is better to include the

upper buccal teeth only (without labial bow) and to involve all lower

post teeth. So, the result would be distalising the upper post teeth while

the ULS will be moved by the effect of lower lip and the traction of the

transeptal fibres following U buccal teeth movement (Lee et al 2005).

2. Qureshi 2007 found that the use of labial bow increase LLS

proclination and more mandibular growth.

3. A recent RCT had shown that the presence or absence of a labial

bow had no effect on maxillary incisor retraction or skeletal change.

Yaqoob O, DiBiase 2011 . Compliance may well be improved by an

absence of upper labial wirework.

4. Sometime lower labial arch can be added if the LLS are spaced.

E. Posterior attachments


Additional headgear produced more maxillary restraint and less rebound force

on the lower teeth which lead to reduce lower incisor proclination. Parkin et al

(2001).

The purpose of this study was to compare the skeletal and dental changes

contributing to Class II correction with 2 modifications of the Twin-block

appliance: Twin-block appliances that use a labial bow (TB1) and Twin-block

appliances that incorporate high-pull headgear and torquing spurs on the

maxillary central incisors (TB2). After pretreatment equivalence was

established, a total of 36 consecutively treated patients with the TB1

modification were compared with 27 patients treated with the TB2 modification.

Both samples were treated in the same hospital department and the same

technician made all the appliances. The cephalostat, digitizing package, and

statistical methods were common to both groups. The results demonstrated that

the addition of headgear to the appliance resulted in effective vertical and

sagittal control of the maxillary complex and thus maximized the Class II

skeletal correction in the TB2 sample. Use of the torquing springs resulted in

less retroclination of the maxillary incisors in the TB2 sample when compared

with the TB1 sample; however, this difference did not reach the level of

statistical significance

Indications for concurrent headgear with functional appliances:-

1. Maxilla is very prominent

2. Proclined LLS.

3. Long face/'high angle' case

F. Anterior attachments

1. Addition of double cantilever Z spring or anterior screw with

torqueing spring to deal with class II D2. The bite registration is taken

with the buccal segment relationship in an over corrected position, this

may result in an edge-to-edge incisor position or a slight reversed


overjet. However, by ensuring that there is 7–8 mm of separation in the

buccal segments, there should be no incisal interference as the upper

labial segment is proclined. It is also essential to have sufficient height

of the blocks to ensure that the patient is more comfortable posturing

forwards than closing in centric relation (Dyer and Sandler 2002). The

advantages of this technique are:

As advancement of the upper labial segment occurs simultaneously with

sagittal correction the patient should never have an increased overjet

placing them at risk of trauma due to prominent upper incisors.

This technique also prevents patients being left with an increased overjet

if they fail to comply with the functional phase following upper incisor

proclination.

Theoretically increase the upper posterior teeth distalization and reduce

the LLS proclination because of the altered anchorage balance.

2. Addition of southern end clasp to the upper and lower incisors

will enhance the skeletal effect and reduce upper incisor retroclination

and lower incisor proclination (Trenouth and Desmond, 2012). The

Southern end clasp was originated by DiBiase and Leavis. It locks the

tooth surface against the acrylic base plate providing greater control

over the axial inclinations of the incisors. The design is similar to the

original Jackson clasp. But it has a problem when expansion by midline

screw is wanted.

3. Acrylic capping of the lower incisors is commonly practiced, but

this has been shown to be ineffectual in preventing proclination Young

& Harrisson 2005 but it might cause demineralization (Dixon, 2005).

4. Flapper spring can be added similar to Southern end clasp and

result in resulted in less retroclination of the maxillary incisors, Parkin

2001


5. Torquing spring: the claimed advantages are to control

retroclination of ULS. The positive effect of the torquing spring had

been proved by Harridine and Gale in 2000.

f. Advancement

It can be activated in asymmetrical way to correct ML deviation One go or incremental advancement of functional appliances?

This was recommended by Petrovic 1975 and Rabie et al 2003. The

theoretical purposes of incremental advancement:

1.Repeated stimulation of lateral pterygoid resulting in more mandibular growth.

If the appliance is stretched as one go then the advantages of lateral pterygoid

will be lost.

2.Less dentoalveolar effect.

3.Better patient compliance.

RCT compared the effects of twin-block treatment with a single advancement to

an edge-to-edge bite and the incremental advancement (Banks et al 2004). This

excellent paper by the developer of this particular incremental mechanism

clearly showed no advantage for the incremental method in terms of process or

outcome of the treatment.

g. Clinical tips

1.It is recommended to trim the acrylic palatal to ULS to allow spontaneous

alignment by the lower lip and the stretch of transeptal fiber.


2.Always check the difference between OJ and reverse OJ since the difference is

fixed and this is a good landmark of the treatment progress

h. Effectiveness of the Twin-block appliance compared to normal

1. Lund & Sandler 1998: This prospective controlled study investigated the

net effects of the Twin Block functional appliance taking into account

the effects of normal growth in an untreated control group. statistically

significant restraint in the maxillary growth was observed. Forward

growth of the mandible. Dentoalveolar effect as usual.

2. O’Brien 2003 9TB, CG, OJ 7mm, 8-10years) 73% dentoalveolar and

27% skeletal)

i. Profile changes:

O’ Brien 2009 did a study to compare the effect of TB on the facial profile using

silhounte tracing for treated and untreated patient who had been rated by their

peers and teachers and found that children with Class II malocclusion, treated

with Twin-blocks in the mixed dentition, had profiles that were generally

perceived as more attractive than those of an untreated cohort, by both peers and

teachers. However, these differences were small.

j. Psychosocial benefits of early orthodontic treatment with the Twin-block appliance

O’Brien 2003 RCT study Results showed that early treatment with Twin-

block appliances resulted in an increase in self-concept and a reduction of

negative social experiences.


FAQ about functional appliance

I. Treatment duration Treatment should continue for at least 12 months to allow intermediate collage

fibres (type 3) to change to more stable one (type 1) (McNamara 1990 &

Voudouris 2003)

II. Advantages of two stage treatment with the functional applianceKing 1990

1.Better cooperation. (True, O’Brien 2003, 2009 with regard to TB treatment

early treatment 18% failure but late 33%)

2.Psychosocial advantages (true O’Brien 2003)

3.Elimination of gingival/palatal trauma. Questionable?

4.High trauma with increased overjets >9mm (Todd & Dodd 1983) (45% 10 yr

olds with OJ more than 9mm have traumatised incisors compared to 27% if the

OJ was less than 9mm especially if the lip is incompetent) however RCT

comparing early versus late treatment concluded:

all groups experienced trauma

very early treatment may prevent trauma but not cost effective (Koroluk et al

2003)

So that, the provision of a mouthguard is recommended to try to prevent trauma

for patients with an increased risk of trauma (contact sports, large OJ).

Latest Cochrane review confirm the trauma prevention benefit.

5.Eliminate growth/local disturbances before they have had time to act fully.

Questionable?

6.Craniofacial tissues more malleable so more favourable changes in skeletal and

dental relationship achieved but may not be clinically significant. (true for

short term, Tulloch, 2004, Kelling, 2008, O’Brien 2003)

7.Less root resorption than one phase (Brin 2003 use the data of UNC and prove

that)


III. Advantages of one stage treatment with the functional appliance1. Better teeth clasping

2. Little cost

3. Growth still present

4. Less risk of burning patient co-operation. Patient has time expiry

approximately 3yrs which can be lost in the first phase leaving no compliance

in the second phase.

5. Soft tissues do not mature until 12-14yrs with vertical growth of lips this might

affects stability of corrected OJ

6. Extraction decision is easy and less 50% less than two phase treatment

(Tulloch 2004)

7. Better final occlusion (O’Brien, 2009)

8. No difference from early treatment in term of skeletal, dental and

psychological results (Tulloch 2004, O’Brien 2009, Dolce 2007, Harrison,

2007)

IV. Stability of myofunctional appliances results• Maxillary changes more stable than mandibular changes.(Weislander, 1993)

• Mandibular skeletal changes all lost after 2 years. Tulloch et al 2004

• 58% dental relapse (Pancherz, 1991)

• Good buccal interdigitation reduces dental relapse (Pancherz and Fackel, 1990)

and (Tulloch et al., 1990)

V. SAQsHow long TB should be?

At least 1 year to allow remodelling of fossa and

the intermediate fiber to be be changed to type 10

stable fiber (Lee 2013) because in the beginning

the dominant fiber are type II (Rabie 1979) which

resulted from activation of lateral pterygoid


muscle.

What factor which

normally influences

extraction decisions

should not apply at the

end of functional

appliance treatment?

The overjet should be fully reduced and no longer a

factor.

What additional factors

will probably be present

which were not present

at the start of functional

treatment?

a) Upper incisor retroclination

b) Lower incisor proclination

c) Distal tipping of other upper teeth

d) Differential growth of the jaws during the

functional phase

How exactly would you

assess the factors in

question 3?

A cephalometric radiograph to measure all these

factors.

How are these factors in

question 3 likely to

influence your treatment

from the end of the

functional phase?

2a,b,c, will influence towards extraction or a more

anchorage-providing extraction pattern or

headgear. 2d is related and may reveal that overjet

correction has been largely due to favourable

growth as opposed to lower incisor proclination

and that extractions are less indicated.

What twin-block design

features would you

specifically choose in a

patient with an anterior

open bite?

Avoid any acrylic or wirework which prevented

eruption of the incisors. no torquing spurs on the

upper incisors and no acrylic or ball-clasps on the

lowers

High-pull headgear.

Spinner or passive tongue thrust breaker

NB: As Tulloch 1998 points out, there is a


widespread belief that children who grow vertically

will respond less well to class 2 treatment, but this

is not well documented or understood. The study

by Ruf and Pancherz (1997) found no evidence to

support this view. The “hyperdivergent” cases in

fact showed 1 mm. better mandibular response than

the “hypodivergent” cases although this was not

statistically significant. This evidence suggests that

‘high angle’ cases are no reason to avoid functional

appliances because of the potential effects on

growth


features would you


patient with upright

upper incisors (not

proclined)?

You would probably opt for torquing spurs to

minimise further retroclination of the upper

incisors.


features would you


patient in the early

mixed dentition?

In the absence of premolars to crib, you might well

opt for features giving more retention on the

incisors such as upper torquing spurs or even

Southend clasps and lower ball-clasps +/- acrylic

capping.


features would you


patient with a very deep

overbite?

Wirework to impede further eruption of the upper

incisors would be sensible such as torquing spurs

and in the lower appliance, incisor capping

An absence or early removal of molar cribs in

order to permit eruption of the molars to level the

curve of Spee at an earlier stage.


Aust Orthod J. 2012 Nov;28(2):190-6.

An investigation of cephalometric and morphological predictors of successful twin block therapy.Fleming PS1, Qureshi U, Pandis N, DiBiase A, Lee RT.

Author informationAbstractOBJECTIVE:To identify predictors of overjet reduction, changes in mandibular length (Co-Me) and antero-posterior changes in mandibular position (Pog-Vert) during Twin Block therapy.

METHODS:Pre- and post-treatment cephalograms of 131 participants were analysed (Mean age 12.73 years +/- 1) following Twin Block therapy.

RESULTS:Mean annualised overjet reduction was 7.29 mm (+/- 2.99) with chin projection improving by 2.66 mm (+/- 5.37). The magnitude of the initial overjet was a strong predictor (95% CI: 0.30, 0.77, p < 0.01) of overjet reduction and change in chin position (95% CI: 0.08, 0.77, p = 0.02). Greater forward movement of Pogonion occurred if there was greater retrusion of Pogonion at the outset (95% CI: 0.15, 0.45, p < 0.01). No prognostic relationship was noted for other potential cephalometric predictors including pretreatment mandibular lower border morphology and Co-Go-Me angle.

CONCLUSION:No relationship between mandibular morphology, vertical skeletal pattern and favourable dentoalveolar and skeletal responses to Twin Block therapy could be found. These results require confirmation on an external sample.

Eur J Orthod. 2013 Jan 4. [Epub ahead of print]

An extended period of functional appliance therapy: a controlled clinical trial comparing the Twin Block and Dynamax appliances.Lee RT1, Barnes E, Dibiase A, Govender R, Qureshi U.

Author informationAbstractSUMMARYThe aim of this clinical trial was to compare the hard- and soft-tissue effects of 15 month full-time functional appliance therapy with Twin Block (TB) and Dynamax (Dx) appliances. The effects on both hard and soft tissue were analysed using cephalograms and three-dimensional optical


http://www.ncbi.nlm.nih.gov/pubmed/23291502


http://www.ncbi.nlm.nih.gov/pubmed?term=Qureshi%20U%5BAuthor%5D&cauthor=true&cauthor_uid=23291502

http://www.ncbi.nlm.nih.gov/pubmed?term=Govender%20R%5BAuthor%5D&cauthor=true&cauthor_uid=23291502

http://www.ncbi.nlm.nih.gov/pubmed?term=Dibiase%20A%5BAuthor%5D&cauthor=true&cauthor_uid=23291502

http://www.ncbi.nlm.nih.gov/pubmed?term=Barnes%20E%5BAuthor%5D&cauthor=true&cauthor_uid=23291502

http://www.ncbi.nlm.nih.gov/pubmed?term=Lee%20RT%5BAuthor%5D&cauthor=true&cauthor_uid=23291502


http://www.ncbi.nlm.nih.gov/pubmed?term=Lee%20RT%5BAuthor%5D&cauthor=true&cauthor_uid=23304967

http://www.ncbi.nlm.nih.gov/pubmed?term=DiBiase%20A%5BAuthor%5D&cauthor=true&cauthor_uid=23304967

http://www.ncbi.nlm.nih.gov/pubmed?term=Pandis%20N%5BAuthor%5D&cauthor=true&cauthor_uid=23304967

http://www.ncbi.nlm.nih.gov/pubmed?term=Qureshi%20U%5BAuthor%5D&cauthor=true&cauthor_uid=23304967

http://www.ncbi.nlm.nih.gov/pubmed?term=Fleming%20PS%5BAuthor%5D&cauthor=true&cauthor_uid=23304967


surface laser scans. One hundred and three subjects with a class II division 1 malocclusion, and a minimum overjet of 7mm were available for analysis following stratified randomization according to gender and age. Data was collected at the start of treatment, 15 month therapy, and after 3 month post-treatment observation. Statistical analysis was conducted using analysis of covariance. The results demonstrated both appliances corrected the overjet with significantly increased skeletal dimensional changes with the TB compared with the Dx with forward movement of pogonion of 5.2mm (TB) and 0.7mm (Dx) P = 0.003. In addition, significant changes occurred particularly in the vertical dimension where there was also an increase in total anterior face height in both groups (TB = 6.4mm, Dx = 5.5mm) and significant (P = 0.003) mandibular length changes were also observed (TB = 7.2mm, Dx = 3.8mm). The cephalometric soft-tissue changes were significantly different between the two appliances at soft-tissue pogonion (TB = 9.8mm, Dx = 4.6mm, P = 0.001). Laser scan three-dimansional changes showed significant difference in the lower labial sulcus region where forward movements were observed (TB = 8.2mm, Dx = 6.2mm; P = 0.04). Overall these changes appear to be greater and more stable than those achieved in a previous 9 month study.

Review/ Effects as determined by clinical studies

Jakobsson (1967). Cephalometric evaluation of treatment effect on Class II, Division 1 malocclusions.

The purpose of the study was to evaluate the treatment effect on Class II, Division 1 malocclusions when the patients were treated with either activator or headgear therapy and to compare the two methods. The sample consisted of 33 boys and 27 girls, aged 8 to 9 years (mean 8.5 years). All children had Class II div 1 malocclusions. Patients were divided into 20 triples according to dental developmental age and morphology of malocclusion. It was decided by lot which patients in the triple were to receive treatment and which were to serve as a control. All patients were reassessed at 18 months. Cephalogram superimpositions of pre- and post-treatment were used to assess treatment changes within each triple. Both activator and headgear treatment had, in a posterior direction, a definite influence on the basal parts of the maxilla. During treatment there was an increase in the anterior facial height and, to a lesser extent, a descent of the condyle. It was concluded that the findings do not agree with the hypotheses that condylar growth and a forward position of the mandible can be obtained with activator treatment.

Tulloch, Phillips and Proffit (1998). Benefit of early Class II treatment: progress report of a two-phase randomized clinical trial:

Preadolescent children (OJ> 7 mm) were randomly assigned to observation only, headgear (combination), or functional appliance (modified bionator) and were monitored for 15 months. 166 patients completed the first phase of the trial, 147 continued to a second phase of treatment. The data from the first 107 patients to complete phase 2 form the basis of this


progress report. During phase 1, on average there was no change in the jaw relationship of untreated children, but 5% showed considerable improvement and 15% demonstrated worsening. Both early-treatment groups had a significant average reduction in ANB angle, more by change in maxillary dimensions in the headgear group and mandibular growth in the functional appliance group. There were wide variations in response, however, with only 75% of the treated children showing favorable skeletal response. Failure to respond favorably could not be explained by lack of cooperation alone. On average, time in fixed appliances was shorter for children who underwent early treatment, but the total treatment time was considerably longer if the early phase of treatment was included. Only small differences were noted in anteroposterior jaw position between the groups at the completion of treatment, and the changes in dental occlusion, judged on the basis of Peer Assessment Rating scores, were similar between groups. Neither the severity of the initial problem nor the duration of treatment was correlated with the occlusal result. The number of patients who required extraction of permanent teeth was greater in the early functional appliance group than in the headgear or control group. The option of orthognathic surgery was presented more often in the cases of children who did not undergo early treatment , but surgery was accepted or was still being considered almost as frequently in the previous headgear group as in the controls, less often in the patients previously treated with functional appliances.

Ghafari, Shofer, Jacobsson, Markowitz and Laster (1998). Headgear versus function regulator in the early treatment of Class II, division 1 malocclusion: a randomized clinical trial:

A prospective randomised clinical trial was conducted to evaluate the early treatment of Class II, Division 1 malocclusion in prepubertal children. Facial and occlusal changes after treatment with either a headgear or a Frankel function regulator are reported. Molar and canine relationships, overjet, intermolar and intercanine distances were measured from casts taken every 2 months, and mounted on a SAM II articulator. Cephalometric radiographs were taken annually. The results indicate that both the headgear and function regulator were effective in correcting the malocclusion. A common mode of action of these appliances is the possibility to generate differential growth between the jaws. The extent and nature of this effect, as well as other skeletal and occlusal responses differ. Treatment in late childhood was as effective as that in midchildhood. This finding suggests that timing of treatment in developing malocclusions may be optimal in the late mixed dentition, thus avoiding a retention phase before a later stage of orthodontic treatment with fixed appliances.


Keeling, Wheeler, King, Garvan, Cohen, Cabassa, McGorray and Taylor (1998). Anteroposterior skeletal and dental changes after early Class II treatment with bionators and headgear:

Anteroposterior cephalometric changes in children enrolled in a randomized controlled trial of early treatment for Class II malocclusion were studied. Children, aged 9.6 +/- 0.8 years at the start of study, were randomly assigned to control (n = 81), bionator (n = 78), and headgear/biteplane (n = 90) treatments. Cephalograms were obtained initially, after Class I molars were obtained or 2 years had elapsed, after an additional 6 months during which treated subjects were randomized to retention or no retention and after a final 6 months without appliances. Calibrated examiners, blinded to group, used Johnston's analysis to measure anteroposterior cephalometric changes. Annual skeletal and dental changes during treatment, retention, and follow-up, and overall, were determined. They found that both bionator and head-gear treatments corrected Class II molar relationships, reduced overjets and apical base discrepancies, and caused posterior maxillary tooth movement. The skeletal changes, largely attributable to enhanced mandibular growth in both headgear and bionator subjects, were stable a year after the end of treatment, but dental movements relapsed.

Cura and Sarac (1997). The effect of treatment with the Bass appliance on skeletal Class II malocclusions: a cephalometric investigation:

The short-term effects of treatment with the Bass appliance by comparative evaluation of treated and untreated skeletal Class II malocclusions were studied. 47 Class II, division 1 malocclusion cases were observed. Twenty-seven (14 girls, 13 boys) were treated with the Bass appliance for an average of 6 months. The remaining 20 cases (6 girls, 14 boys) served as a control. At the end of the 6 month treatment period the statistically significant treatment changes could be summarized as follows: the sagittal skeletal relationship was improved as a result of favourable growth responses in both the maxilla and the mandible. The overjet was reduced and the molar relationship was corrected as a result of the extended skeletal changes. Distal movement of the upper dentition was evident, with unchanged inclination of the maxillary incisors. Both anterior and posterior facial heights were increased without changes in the inclinations of the palatal and mandibular planes. No significant dental movement was observed in the mandible.

Tulloch, Proffit and Phillips (1997). Influences on the outcome of early treatment for Class II malocclusion:


In the first phase of a randomized clinical trial of early versus late Class II treatment, statistically significant differences were observed between the treatment and observation groups. However, there were wide variations in response. The change in jaw relationship (categorized as the annualized reduction in ANB angle) was favorable or highly favorable in 76% of the headgear, 83% of the functional appliance, and 31% of control (observation only) groups. The patient's initial skeletal severity, age/maturity at the outset of treatment, growth pattern, and cooperation with treatment were examined as possible influences on early growth modification treatment. Correlations between the annualized change in the ANB angle and any of the possible influences were close to zero and not statistically significant. It was concluded that there is little to be gained from precisely timing early treatment to specific age/maturity markers and that a favorable reduction in Class II skeletal problems can occur for patients in a broad range of skeletal severity and growth patterns. Cooperation, measured as the number of hours of reported wear, or the clinical assessment of compliance, explained little of the variation in treatment response. The wide variation in growth seen in the untreated patients highlights the importance of well-controlled studies if clinicians are to improve their ability to select children with the greatest chances of a favorable treatment response.

Tulloch, Phillips, Koch and Proffit (1997). The effect of early intervention on skeletal pattern in Class II malocclusion: a randomized clinical trial:

In this controlled clinical trial, patients in the mixed dentition with overjet > or = 7 mm were randomly assigned to either early treatment with headgear, or modified bionator, or to observation. All patients were observed for 15 months with no other appliances used during this phase of the trial. The three groups, who were equivalent initially, experienced statistically significant differences (p < 0.01) in skeletal change. There was considerable variation in the pattern of change within all three groups, with about 80% of the treated children responding favorably. Although patients in both early treatment groups had approximately the same reduction in Class II severity, as reflected by change in the ANB angle, the mechanism of this change was different. The headgear group showed restricted forward movement of the maxilla, and the functional appliance group showed a greater increase in mandibular length. The permanence of these skeletal changes and their impact on the subsequent treatment remains to be evaluated.

Webster, Harkness and Herbison (1996). Associations between changes in selected facial dimensions and the outcome of orthodontic treatment:


In children with Class II, Division I malocclusion who were treated with functional appliances, the strength of the associations between the changes over 18 months in selected facial dimensions and the success of orthodontic treatment as determined by the weighted Peer Assessment Rating (PAR) were determined. Forty-two children, between 10 and 13 years of age (mean age 11.6 years), were randomly assigned to either an untreated group (control) or a group treated with either a Frankel function regulator or Harvold activator (treatment). The outcome of treatment was assessed on study models and the craniofacial changes were measured on lateral cephalometric radiographs. Correlation coefficients were then calculated between the differences in the cephalometric variables over 18 months and the differences in the PAR scores. In the treatment group, the effects of normal growth were held constant by partial correlation. The partial used was the change in both stature and weight. Significant positive partial correlations were found between the increases in total anterior face height, posterior face height, S-Pg, and treatment success. Significant negative partial correlations were found between downward movement of the maxilla and mandibular body and lower anterior face height and treatment success. It is postulated that these associations occurred mainly in response to the bite opening by the appliances. Treatment success was also significantly associated with maxillary restriction, an increase in the SNB angle and a reduction in the ANB angle. Changes in B point due to proclination of the mandibular incisors were considered to be responsible for the two latter significant associations. Although mandibular length increased significantly in the treatment group, as compared with the control group, it was not significantly associated with treatment success.

Courtney, Harkness and Herbison (1996). Maxillary and cranial base changes during treatment with functional appliances:

The purpose of this prospective study was to investigate the maxillary and the cranial base changes after treatment with the Harvold activator and the Frankel function regulator appliances. Forty-two children, who are 10 to 13 years old, with Class II, Division 1 malocclusions were matched in triads according to age and sex and randomly assigned to either the control, Harvold activator, or Frankel function regulator group. Lateral cephalometric radiographs were taken at the start of the study and 18 months later. Both appliances reduced the overjet by tipping the maxillary incisors palatally and, as a consequence, the length of the maxillary arch was reduced. The appliances had no effect on either the horizontal or vertical position of the maxillary molars. Small, but statistically significant, changes in the cranial base angle in the Frankel function regulator group were attributed to relatively large changes at basion in several children, influencing the results because of the small size of the sample. The appliances had no effect on the position of the maxilla.


Nelson, Harkness and Herbison (1993). Mandibular changes during functional appliance treatment:

The purpose of this prospective trial was to determine the changes in position and size of the mandible in children treated with either the Frankel function regulator or Harvold activator. Forty-two 10- to 13-year-old children with Class II, Division 1 malocclusions were matched in triads according to age and sex and randomly assigned to either control, Frankel function regulator, or Harvold activator groups. There were no statistically significant differences between the groups at the beginning of the study. After 18 months, significant increases in gonial angle and articulare-pogonion length in the Harvold group were attributed to a change in the location of articulare because the condyles were positioned downward and forward at the end of treatment. The main effects of both appliances were to allow vertical development of the mandibular molars and increase the height of the face. The Harvold appliance also proclined the lower incisors and increased mandibular arch length. No evidence was found to support the view that either appliance was capable of altering the size of the mandible.


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