Al Esraa University College

Dentistry Department / Orthodontics

4th

Grade هبة محمذ الخطيب 0د

Lec: 16

Orthopedic Appliances

Orthopedic appliances generally use teeth as “handles” to transmit forces to the

underlying skeletal structures. Basis of orthopedic appliance therapy resides in

the use of intermittent forces of very high magnitude. Such heavy forces when

directed to the basal bone via teeth tend to alter the magnitude & direction of the

jaws by modifying the pattern of bone apposition at periosteal sutures & growth

sites.

There are 2 types of forces used in orthodontics

1) orthodontic force – when applied brings about dental change. They are light

forces ( 50- 100 gm) bringing about tooth movement.

2) orthopedic force – when applied brings about the skeletal changes. They are

heavy forces ( 300-500gm) that bring about changes in the magnitude &

direction of bone growth.

The appliances that produce skeletal changes by applying orthopedic forces are

known as orthopedic appliances. Since they employ heavy forces, adequate

anchorage required is gained by extra oral means using occipital, parietal, frontal

cranial bones and cervical vertebrae.

PRINCIPLES OF USING ORTHOPEDIC APPLIANCES

The following are the basic principles of using orthopedic appliances effectively

1) Magnitude of force

Extra oral forces of much greater magnitude, in excess of 400gms per side is

required to bring about skeletal changes. Most orthopedic appliances employ

forces in the range of 400-600 gm per side to maximize skeletal changes and to

minimize dental change. Such heavy force compress the periodontal ligament on

the pressure side & cause hyalinization, which prevents tooth movement.

2) Duration of force

Orthopedic changes are best produced by employing intermittent heavy forces.

Intermittent forces of 12-14 hours duration per day appear to be effective in

producing orthopedic changes. An intermittent heavy force is less damaging to

the teeth and periodontium than a continuous heavy force.

3) Direction of force

Orthopedic force should be applied in the appropriate direction to have a

maximum skeletal effect. The desired changes are best achieved when the line of

force passes through the center of resistance of the skeletal structures to be

moved. The force direction or force vector should be decided depending on the

clinical needs.

4) Age of the patient

It is advisable to begin orthopedic appliance therapy while patient is still in the

mixed dentition period, to make most of the active growth occurring prepubertal

growth spurt. Treatment may have to be continued until the completion of

adolescent growth, so as to prevent relapse caused by the re-expression of

patients fundamental growth pattern after cessation of orthopedic therapy .

5) Timing of force application

Optimum timing of extra oral force application is considered to be during

evening & night. This is because, an increase release of growth hormone and

other growth promoting endocrine factors has been observed to occur during the

evening & night rather than during the day. Evidence suggest that skeletal growth

is associated with sleep onset & follows circadian pattern.

Myofunctional appliances A removable or fixed appliance which favorably changes the soft tissue

environment” (Frankel,1974)

A removable or fixed appliance which changes the position of mandible so

as to transmit forces generated by the stretching of the muscles, fascia &/or

periosteum, through the acrylic and wirework to the dentition and the

underlying skeletal structures. (Mills,1991)

Classification of Myofuctional Appliances By Profitt ;

(i) Teeth borne passive-myotonic appliances e.g.: Activator, Bionator

(ii) Teeth borne active-myodynamic appliances e.g.; Bimler’s appliance, elastic

open activator.

(iii) Tissue borne passive appliances e.g.: Oral screen, lip bumpers

(iv) Tissue borne active appliances e.g.: Frankel’s appliances

(v) Functional orthopedic magnetic appliances (FOMA)

Indications of myofunctional appliances 1- The patient must still be growing, (phase of rapid growth).

2- The pattern and direction of facial growth should be reasonably favorable.

3. The patient must be well motivated because they are relatively bulky and must

be worn most of the time.

Advantages of functional appliances: 1- Can be used in early mixed dentition.

2- Less chair side time, number of visits and minimal chair side adjustment.

3- Reduce the severity of the case.

4- Favorable growth of the jaw with favorable dentoalveolar compensation.

5- Easy to maintain oral hygiene, less side effects of mechanotherapy such as,

root resorption and decalcification.

6- Acceptable, can be worn during night.

7- The cost is relatively lower than fixed appliance.

Disadvantages of functional appliances: 1. Success of functional appliances depend on patient cooperation.

2. Not possible to correct rotation, crowding and there is no precise tooth

movement.

3. Treatment duration is often prolonged.

4. Treatment must be carried out at a precise and relatively critical time.

5. Not useful in adults where active growth is completed.

Limitations of Functional appliances: 1. They can be used to correct basal bone/arch relationship and cannot be used

for correcting dental malocclusion.

2. It is not useful in managing adult patents where the active growth is

completed.

3. It requires a final phase of fixed appliance therapy to achieve final detailing or

final alignment of tooth position.

4. The result of treatment is totally dependents upon the patient's cooperation.

5. They have a tendency to increase the lower facial height and hence,

they cannot be used in patients with backward rotating mandible.

Mode of action Dento-alveolar changes: They produce dentoveolar changes by teeth movement.

In fact, their major effect is on the position of teeth and alveolar process.

Changes in maxillary growth: There is a restriction of forward growth of the

maxilla similar to the effect of headgear.

Changes in mandibular growth: There is evidence that functional appliances

may induce on average an extra of 1-2 mm of the growth of the mandible.

Changes in the glenoid fossae: Remolding of the glenoid fossae.

They can bring about the following changes:

1. An increase or decrease in jaw size.

2. A change in spatial relationship of the jaws.

3. Change in direction of growth of the jaws.

4. Acceleration of desirable growth.

Duration and timing of wear Functional appliance treatment should be started before the pubertal growth spurt

when the mandible may exhibit increased growth rate.

Functional appliances should be worn for at least 10- 12 hours a day.

These appliances should be worn at nighttime as this is when growth takes place.

Oral screen

Oral screen is a thin sheet of acrylic processed over the occluded waxed working

casts extending deep into the sulcus both labially and buccally which act as a

screen between teeth and musculature. Vestibular screen does not contact teeth as

compared to oral screen.

Indications:

1. To intercept mouth breathing, thumb sucking, tongue thrusting, lip biting &

cheek biting.

2. To perform muscle exercises to help in correction of hypotonic lip & cheek

muscles.

3. Mild anterior proclination.

LIP BUMPER

“Combined removal-fixed appliance”. Used in both maxilla & mandible to shield

the lips away from the teeth.

Uses:

-In lip sucking patients.

-Hyperactive mentalis activity.

-To augment anchorage

-Distalization of first molars.

ACTIVATOR

This is a one-piece functional appliance, with minimal acrylic to improve

patient comfort. As there is no molar capping on the lower posterior teeth, these

teeth are free to erupt. The Activator is therefore useful when trying to reduce a

deep overbite.

Indications:

-In actively growing individuals with favorable growth patterns.

-class II div I malocclusion

-class II div II malocclusion

-class III

-class I open bite

-class I deep bite

-as a preliminary treatment before major fixed appliance therapy to improve

skeletal jaw relations.

-children with lack of vertical development in lower facial height.

Contraindications:

-correction of class I cases with crowded teeth caused by disharmony of tooth

size & jaw size.

-in children with excess lower facial height.

-in children whose lower incisors are severely proclined.

-in children with nasal stenosis caused by structural problems in the nose or

chronic untreated allergy.

-in non-growing individuals.

Advantages:

-uses existing growth of the jaws.

-minimal oral hygiene problems.

-intervals between appointments is long.

-appointments are short and minimal adjustments required .

- relatively economic.

Disadvantages:

-requires very good patient cooperation.

-cannot produce a precise detailing & finishing of occlusion.

The Twin-Block Appliance It is well tolerated by patients as it is constructed in two parts. The upper and

lower parts fit together using posterior bite blocks with interlocking bite-planes.

The patient is encouraged to posture the mandible forwards, so that the lower

block occludes in front of the upper block.

The appliance can be worn full time, which means that rapid correction is

possible. It is also possible to modify the appliance to allow expansion of the

upper arch during the functional appliance phase.

It is also easy to reactivate the twin-block appliance. This means that during

treatment if further advancement of the mandible is required, it is possible to

modify the existing appliance rather than having to construct a new appliance.

One of the side-effects of the twin-block appliance is that; The posterior teeth are

prevented from erupting by the occlusal coverage of the bite blocks. Some

clinicians will trim the acrylic away from the occlusal surfaces of the upper block

to allow the lower molars to erupt. Any remaining lateral open bites are closed

down in the fixed appliance phase of treatment.

HERBST APPLIANCE

The Herbst appliance is a fixed functional appliance.

It is as successful at reducing overjets as the twin-block appliance. It is however

slightly better tolerated than the bulkier twin-block appliance, with patients

finding it easier to eat and talk with it in place. The principle disadvantages are

the increased breakages and higher cost of the Herbst appliance.

Indications:

-correction of class II malocclusion due to retrognathic mandible.

-can be used as anterior repositioning splint in patients having TMJ disorders.

-Post adolescent patients: treatment completed within 6-8 months, hence possible

to use the residual growth in these patients.

-Mouth breathers

-Uncooperative patients

Advantages:

-continuous action

-Treatment duration is short -less patient cooperation needed

-can be used in patient who are at the end of their growth

-can be used in patient with mouth breathing habit.

Disadvantages:

-cause minor functional disturbances.

-repeated breakage & loosening of appliance occurs, especially in lower

premolar area.

-plaque accumulation & enamel decalcification can occur

-tendency for posterior open bite.

JASPER JUMPER

• A relatively new flexible fixed functional appliance introduced by

J.J.Jasper,1980 • Actions similar to Herbst appliance, but lack rigidity.

• Basically indicated in skeletal class II Malocclusion with maxillary excess &

mandibular deficiency.

Advantages:

-produce continuous force.

-does not require patient compliance.

-allows greater degree of mandibular freedom than Herbst appliance

-oral hygiene is easier to manage.

Bionator The bulkiness of the activator and its limitation to night-time wear was a major

deterrent in its greater use by clinicians to obtain maximum potential of

functional growth guidance.

The bionator was originally designed to modify tongue behavior, using a heavy

wire loop in the palate.

Indications

Bionator is indicated for the treatment of Class II Division 1 malocclusion in the

mixed dentition using under the following conditions:

• Well aligned dental arches.

• Functional retrusion

• Mild to moderate skeletal discrepancy

• No evidence of labial tipping seen

Contraindications

• Class II relationship caused by maxillary prognathism

• Vertical growth pattern

• Labially tipped lower incisors.

Advantages

1. Appliance is less bulky.

2. Can be worn full time, except during meals.

3. Appliance exerts a constant influence on the tongue and perioral muscles.

Disadvantage of appliance

The main disadvantage lies in the difficulty of correctly managing it.

Frankel appliance (Function Regulator / FR ) The Frankel appliance is the only completely tissue-borne appliance.

There are different versions designs; FR1, FR2, FR3 and FR4 to treat different

types of malocclusions; CL I, CL II, CL III and Open bite respectively. Like

other functional appliances it postures the mandible forwards. It also has buccal

shields to hold the cheeks away from the teeth and stretch the periosteum.

It can be difficult to wear, is expensive to make and is troublesome to repair. As

a result it is now used less frequently.

Mode of action of FR

1. Increase in transverse sagittal direction by use of buccal shields and lip pads.

2. Increase in vertical direction by allowing the lower molar to erupt freely

because appliance is fixed to the upper arch.

3. Muscle adaptation. The form and extension of the buccal shields and lip pads

along with the prescribed exercises corrects the abnormal peri-oral muscle

activity.

1- HEADGEAR Headgears are the most common among all the orthopedic appliances.

They are ideally indicated in patients with excessive horizontal growth of the

maxilla with or without vertical changes.

They are most effective in the prepubertal period.

Headgears can also be used to distalize the maxillary dentition along with the

maxilla. They are an important to gain or maintain anchorage.

2- FACEMASK Class III malocclusion is usually a result of a combination of maxillary

deficiency and mandibular excess. Growth modification for Class III problems is

the reverse of Class II, i.e. treatment involves restriction of mandibular growth

along with downward and forward maxillary growth.

A facemask works on the principle of pulling the maxillary structures forward

with the help of anchorage from the chin or forehead or usually both. A forward

maxillary pull is applied with the help of heavy elastics that are attached to hooks

on the rigid framework. It works best in young, growing children (around 8

years).

Indications

1. Mild to moderate Class III skeletal malocclusion due to maxillary retrusion,

2. Ideal patients for facemask should have:

• Normal or retrusive maxillary teeth.

• Short or normal, but not long, anterior vertical facial dimensions.

3. Correction of postsurgical relapse after osteotomies.

4. Selective rearrangement of palatal shelves in cleft patients.

3- CHIN CUP It is an extraoral orthopedic device, which is useful in the treatment of Class III

malocclusions that occurs due to a protrusive mandible but a relatively normal

maxilla.

Chin cup therapy attempts to retard or redirect the growth of the mandible in

order to obtain a better anteroposterior relation between the two jaws; therefore

chin cup works well in patients with reduced or normal lower anterior face height

but is contradicted in long face patients.

Effects of Chin cup

Extraoral force of the chin cup, directed against the mandibular growth, the

following effects are seen:

a. Redirection of mandibular growth in a downward and backward direction.

b. Remodeling of the mandible and a decrease in mandibular plane angle and

gonial angle.

c. Lingual tipping of lower incisors.

d. Improvement in skeletal and soft tissue profile.