myofunctional or functional appliances
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Lec. 7 Myofunctional or Functional Appliances
1
Lec.7 د.سهى علي
Myofunctional or Functional Appliances
Introduction
Functional /Myofunctional Appliances are devices that alter patient's functional
environment in an attempt to influence and permanently change the surrounding
hard tissue. Most of the functional appliances are mainly designed to correct
skeletal class II relationship by positioning the mandible downward and forward
to enhance mandibular growth. All functional appliances are intraoral devices.
Functional appliances may be removable or fixed.
Definition
By Proffit—"Functional appliances are appliances which alter the posture
of the mandible, holding it open or closed and forward or backward."
Functional appliances are appliances which act by either harnessing the
muscular forces or by preventing aberrant muscular forces.
Advantages of Functional Appliances
1. They are effective in vertical control of increased overbite.
2. They can be used in the mixed dentition.
3. They require minimal chairside adjustment.
Disadvantages of Functional Appliances
1. The success of functional appliances therapy solely depends on patient
cooperation.
2. Precise tooth movement is not possible with functional appliances.
3. Treatment duration of functional appliances is often prolonged.
4. Functional appliances often need two phases treatment to complete the
treatment. Functional appliances may be used for definitive treatment or
as phase 1 of two phase treatment. Phase 1 treatment is aimed at reducing
the overjet, overbite and to correct sagittal jaw relationship, while phase 2
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treatment is aimed at completing the final alignment using fixed
mechanotherapy.
Classification of Functional Appliances
Functional appliances can be divided into removable or fixed functional
appliances. Removable functional appliances can be classified into removable
tooth borne and removable tissue borne functional appliances. The fixed
functional appliances are tooth borne
Removable Functional Appliances
Removable functional appliances include removable tooth borne and removable
tissue borne functional appliances.
Removable Tooth Borne Appliances
These appliances depend on the stretch of the soft tissues caused by the
mandible being positioned downward and forward, as well as by the muscle
activity generated by the mandible attempting to return to its original position.
Examples Activator, Bionator and Twin block appliance.
Removable Tissue Borne Functional Appliances
These appliances are used to minimize unwanted tooth movement and to
recontour the facial soft tissue adjacent to the teeth as well as posture of
mandible downward and forward. Example: Functional regulator /functional
corrector/ Frankel appliance.
Fixed Tooth Borne Functional Appliances
The fixed tooth borne functional appliances are fitted on the teeth and cannot be
removed by the patient at will. Example: Herbst appliances.
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Effects of Functional Appliances
Effects of functional appliances include effect on the dentition, skeletal and
muscular structures.
Effects of Functional Appliance on Dentition
Functional appliances typically cause some intrusion of maxillary incisors. This
is caused by a lingual force transmitted from the labial bow against these teeth
when the mandible attempts to reposition back to its normal position. This
natural repositioning attempt by the mandible causes protrusion of mandibular
incisors caused by a labial force transmitted from the portion of the appliance
lingual to these teeth.
Effect of Functional Appliances on Skeletal Structures
Functional appliances are designed to stimulate the growth in the condylar
region and can also produce change in the direction of growth of the jaws.
Functional appliances can also bring about downward and forward remodeling
of the glenoid fossa. Functional appliances are also capable of restricting the
growth of the jaws.
Effect of Functional Appliances on Muscular Structures
Functional appliances are designed to improve the tonicity of orofacial
musculature.
Principles of Functional appliances treatment
1. Most of the functional appliances are used to correct early Class II
malocclusions and some cases of Class III malocclusion, deepbite and
openbite.
2. A Class II division 1 malocclusion caused by a prognathic maxilla is not
a good case for functional appliance therapy. While, retrognathic
mandible are generally cases indicated for functional appliance therapy.
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3. Functional appliances can be utilized in the correction of Class II division
2 malocclusions if the growing patients with a mild to moderate Class II
skeletal pattern. In such cases it may be helpful to have a pre-functional
phase to procline the retroclined upper incisors, this can be achieved by
using a removable appliance.
4. Functional appliances should be used when the patient is growing. As
girls complete their growth slightly earlier than boys, functional
appliances can be used a little later in boys. It has been suggested that
treatment should, if possible, coincide with the pubertal growth spurt (10-
14 years for girls, 12-16 years for boys). Generally it is better to start the
Functional appliance treatment in the late mixed dentition, provided there
is still growth remaining. This means that the patient is ready to progress
onto the fixed appliance stage which typically follows the functional
appliance. If the functional, appliance is started too early then there will
be delay while waiting for the remaining deciduous teeth to exfoliate.
Treatment for Class III and open bite cases should usually start sooner
than for Class II problems.
5. Functional appliances should be preferably fitted on well aligned dental
arches.
6. There are two major principles applied in the use of functional
appliances; force elimination e.g. oral screen and force application e.g.
the Activator appliance.
7. Functional appliance should be worn for 12-16 hours per day. Most
growth occurs during evening hours when growth hormone is being
secreted, typically between 8 pm and midnight or 1am, so it is suggested
that children wear functional appliances from after the evening meal until
they awake in the morning which should be approximately 12 hours per
day.
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8. There are two major principles applied in the use of functional
appliances; force elimination e.g. oral screen and force application e.g.
the Activator appliance.
Activator
Viggo Andresen, in 1908 in Denmark, designed a loose fitting appliance, which
he first used on his daughter. He used this appliance on his daughter who was
going on a three month vacation. On her return three months later, he found a
marked sagittal correction and improvement of the facial profile. Although it
was developed more than 70 years ago, the Andresen appliance, which is also
known as an activator or monobloc, has been successfully used by many
generations of orthodontists. The activator is generally used for the treatment of
Class II div I malocclusion. The disadvantages of Activator are fully rely on
patient cooperation, bulky and uncomfortable.
Components of the Activator
1. Acrylic portion
2. Upper and/or lower labial bow
3. Jack screw: Optional (fitted to maxillary arch).
Fig. 1: Activator
Indications
1. Class I malocclusion with deep bite
2. Class II malocclusion with open bite
3. Class II division 1 malocclusion
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4. Class II division 2 malocclusion after aligning the incisors
5. Class III malocclusion (reverse activator)
Contraindications
1. Crowded arch
2. Increase lower facial height
3. Severe proclined lower incisors
Fabrication
1. Impressions: The impressions should reproduce the whole alveolar process
to the depths of the sulci.
2. Bite Registration
• Before taking the wax bite, the study models can be used to help decide if the
overjet can be corrected with one activator or whether a second one will be
needed. If the overjet is 8 mm or more two activators will normally be required
• If the overjet is less than 8 mm, it can be corrected with one activator
appliance. For these cases, the wax bite can be taken with the mandible
protruded sufficiently to bring the incisors almost edge-to edge (Fig. 2).
• A piece of good quality pink wax of approximately 6x8 cm dimensions is
warmed in hot water and folded over two or three turns to make a soft sausage
of wax. A slightly more bulky sausage will be needed for deep bite low angle
cases.
• The softened wax is pressed onto the upper teeth and then the lower jaw
protruded. Then the wax bite is cooled and if necessary, trimmed with a sharp
knife. It should be checked on the study modes and in the mouth, possible (Fig.
3).
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Fig. 2: If the overjet is less than 8 mm it can be corrected with one activator
appliance. For these cases the wax bite can be taken with the mandible
protruded sufficiently to bring the incisors almost edge-to-edge
Figs 3: A to D: The softened wax is pressed onto the upper teeth and
then the lower jaw protruded, then the wax bite is cooled and if
necessary, trimmed with a sharp knife. It should be checked on the
study models
3. Casting the Impressions: The impressions are poured in dental stone and
carefully mounted on a plane line articulator ensuring that the bite is correct.
Bionator
The bionator was developed in Germany by Wilhelm Baiter in the early 1950s
to increase patient's comfort and facilitate daytime wear to increase the
functional use of the appliance. Baiter accomplished this by drastically reducing
acrylic bulk of the appliance.
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Indications
Bionator is mainly indicated for the treatment of Class II division 1
malocclusion with mild to moderate skeletal discrepancy (mandibular
deficiency) for growing patient.
Types of Bionator
There are three basic types:
• Standard appliance.
• Open-bite appliance.
• Class III or reverse bionator.
Fig. 4: Standar bionator -side view
Uses of Bionator
1. Class II malocclusion.
2. Class III malocclusion.
3. Deep bite cases.
4. Open bite cases.
Frankel Appliance
The function regulator (FR) appliances are developed by "Rolf Frankel". The
function regulators (FR) are orthopedic exercise devices that aid in the
maturation, training and reprograming of orofacial neuromuscular system.
Types of Frankel Appliance
There are five types of Frankel's Appliances:
1. FR-I is further divided into three types: FR-Ia, FR-Ib and FR-Ic.
2. FR-II
3. FR-III
4. FR-IV
5. FR-V.
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Indications of Various Types of Frankel Appliances
1. FR-1 a appliance of Frankel: Treating Angle's class I malocclusion with
deep bite.
2. FR-I b appliance of Frankel: Indicated for treating the cases of Angle's
class II division 1 malocclusion where the overjet does not exceed 5 mm.
3. FR-I c appliance of Frankel: Indicated for treating the cases of the Angle's
class II division 1 malocclusion where the overjet is more than 7 mm.
4. FR-II appliance of Frankel: Indicated for treating cases of Angle's class II
division 1 malocclusion and class II division 2 malocclusion.
5. FR-III appliance of Frankel: Indicated for Angle's class III malocclusion.
6. FR-IV appliance of Frankel: Indicated for treating bimaxillary protrusion
and open bite.
7. FR-V appliance of Frankel: It is used with headgear.
Fig 5: Frankel Appliance
Twin-Block Appliance
The twin block appliance was developed by Clark in 1977, and it consists of
upper and lower parts that fit together using posterior bite blocks with
interlocking inclined bite planes, which posture the mandible forwards.The
appliance became popular due to a number of advantages over other functional
appliances namely:
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1. Have greater freedom of movement arid cause less interference with normal
oral function as it is constructed in two parts.
2. Appearance is noticeably improved.
3. Less bulk, therefore, better patient compliance.
4. Can be used in later stages of growth (late mixed dentition/early permanent
dentition).
5. It can be easily modified to correct dental problems.
Indication
It is mainly used for correction of CI II division 1 cases (mandibular deficiency)
for growing patients.
Fig. 6: Twin Block Appliance
Herbst Appliance
It is a fixed functional appliance. It consists of bilateral telescopic mechanism
(rigid arms) attached to the upper and lower buccal segment teeth that maintains
the mandible in a protruded position. As it is a fixed appliance, it removes some
(but not all) compliance factors. The disadvantages are the increased breakages
and higher cost of the Herbst appliance. It is mainly used for correction of CI II
cases with mandibular deficiency.
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Fig. 7: Herbst Appliance
Oral Screen (Vestibular Screen)
Newell in 1912 introduced oral screen. It is composed of acrylic base material,
which fits in the buccal/labial vestibule of the mouth.
Indications
1. Oral habits, such as
a. Thumb sucking
b. Mouth breathing
c Tongue thrusting
d. Lip biting
2. In the cases of mild proclination of maxillary anterior teeth
Mechanism of Action
• Oral screen acts like a mechanical barrier between teeth and lips, tongue,
thumb and thereby help in correcting the oral habits, such as mouth breathing,
thumb sucking, lip biting and tongue thrusting.
• Oral screen is made to contact the proclined teeth when it is used to retrocline
the incisors. It transmits the forces of periooral musculature to the teeth and
these by retroclining the proclined anterior teeth.
• It is also used as a muscle exerciser to stimulate the hypotonic perioral
muscles.
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Figs 8 A to D: (Ai and ii) Oral screen, (B i and ii) Oral screen with wholes
can be used to treat mouth breathing habit, (C) Double oral screen, (Di, ii
and iii) Hotz type of oral screen. This type of oral screen can be used to
treat mild proclination of upper anterior teeth and also can be used to treat
habit, such as thumb sucking habit and digit sucking
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Lip Bumper
The lip bumper is a fixed functional orthodontic appliance that works by
altering the equilibrium between cheeks, lips and tongue and by transmitting
forces from perioral muscles to the molars where it is applied (Fig. )
Uses
Uses of lip bumper include (Fig. 9):
a. Lip bumper is used to treat lip suckling habit.
b. Lip bumper is used to treat lip biting habit.
c. Lip bumper is used as a molar anchorage.
d. Lip bumper is used for space gaining in the lower arch.
Fig.9: Lip bumper in conjunction with fixed orthodontic appliance
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