Post on 31-Jan-2023
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.