principles of functional appliance therapy
DESCRIPTION
PRINCIPLES OF FUNCTIONAL APPLIANCE THERAPY. Dr Diana Md Zahid. Topics to be covered. Definition The appliance Type of case and use Aim of treatment Mechanism of action. Indications and contraindications Classification and types of appliance Timing Effect of appliance - PowerPoint PPT PresentationTRANSCRIPT
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PRINCIPLES OF FUNCTIONAL APPLIANCE
THERAPYDr Diana Md Zahid
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Topics to be covered..
Definition
The appliance
Type of case and use
Aim of treatment
Mechanism of action
Indications and contraindications
Classification and types of appliance
Timing
Effect of appliance
Problem with appliance
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DEFINITION
Removable or fixed orthodontic appliances which use forces generated by the stretching of muscles, fascia, and /or periodontium to alter skeletal and dental relationships
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THE APPLIANCE
In general : no active component (springs or elastics)
Alter the anteroposterior occlussion between upper and lower dental arches
Thus cannot on their own treat irregularities of alignment
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TYPE OF CASE
For correction of moderate to severe Class II div I and Class II div 2
Less for correction of Class III due to much lower success
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THE USE
To modify growth when jaw discrepancies exist.
The growth modification usually aimed at
the mandibular condyles and
the maxillary sutures
Direct pressure applied to bones.
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MECHANISM OF ACTION
1. Re-educate the muscle
2. Stimulate the lateral pterygoid muscle
3. Unload the mandibular condyle
4. Transduction of viscoelastic forces
5. Differential eruption of teeth
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AIM OF TREATMENT
Correct OJ and OB
Correct buccal, AP, transverse relationship
Alter soft tissue environment
By maximising the changes in facial growth, adaptation and development.
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INDICATIONS : a. PATIENT
1. Growing patient:
Utilize growth potential
Preferably approaching a phase of rapid growth
The pattern and direction of growth should be reasonably favourable (which direction? Forward….)
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INDICATIONS : a. PATIENT
2. Motivated patient:
The appliances are bulky, must be worn for substantial amount of time
Thus requires a considerable effort and commitment,
Particularly in early stages of treatment
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INDICATIONS : b. DENTAL
“Classic” case: uncrowded, well aligned
Functional appliance have non-mechanism for treating irregularities of alignment of teeth
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INDICATIONS : c. SKELETAL
Commonly:
Moderate to severe Class II skeletal base
Normal to low MMPA
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Other uses:
Interceptive e.g large OJ
Anchorage e.g CII molars
Compromise cases e.g poor OH with increase OJ
CII/2 cases once converted to CII/1
CIII cases (modified TB and FR3 Frankel have been described but no evidence of any skeletal correction)
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CONTRAINDICATIONS
Non-growing
Non compliance
Labial tipping of lower incisors
Care needed with:
High angle cases with backward mandibular growth rotation
AOB
Cases with proclined lower incisors
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CLASSIFICATIONVarious systems:
Myotonic- large mandible opening (8-10mm)
Myodynamic - medium mandible opening (<5mm), stimulate muscle activity
Passive tooth borne e.g Andresen
Active tooth borne e.g Twin Block (actively move teeth by components, spring, screw)
Tissue borne e,g Frankel
Component approach e.g Hybrid appliance
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TYPES OF FUNCTIONAL APPLIANCE
TWIN BLOCK
THE ANDRESEN ACTIVATOR
THE HARVOLD ACTIVATOR
HERBST APPLIANCE
MEDIUM OPENING ACTIVATOR
BIONATOR
FRANKEL APPLIANCE
Others
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Twin block appliance The upper and lower parts fit together using posterior bite
blocks with interlocking biteplanes which posture the mandible forward
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The Andresen Activator
Monoblock
Loose, difficult to tolerate
To correct the Class II
buccal segment
Buccal facetting to aid
posterior eruption
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The Harvold Activator Based on Andresen design
Wider opening
Guidance of eruption,
Can be use with Fixed App
Maximum effect from
stretching muscle.
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Herbst Appliance A fix-functional appliance.
The section attached to the upper buccal segment teeth and a section on lower buccal segment teeth to protrude mandible forward.
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Medium Opening Activator
A one-piece appliance to reduce deep OB
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Bionator Originally to modified tongue behavior (on the basis
that tongue increased the overjet)
Minimal bulk, easy to wear, expansion by heavy wire loop of buccal segment.
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The Frankle Appliance Is a functional regulator and uses
shield.
Complex, uncomfortable, rapid changes if worn properly.
Three main variants:
FR1: Class II div 1
FR2: Class II div2
FR3: Class III
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Twin block appliance The upper and lower parts fit together using posterior bite
blocks with interlocking biteplanes which posture the mandible forward
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TB
A modification of TB appliance described by Clark
Indicated for Class II/1, Class II/2
Removable
To be worn full time except eating in some cases
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TB:The standard design
Adams clasp on maxillary and mandibular 4’s & 6’s
Ball end clasp on lower labial segment to maximise retention
Labial bow
Steep inclined plane interlocked at about 70° to the occlusal plane which postures mand forward
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TB:Modified design
Possible to modify appliance to allow expansion
Components may be added e.g expansion screws, headgear tubes, springs
Fixed TB-variation of TB which is not removable
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TB
Jaw registration taken with approximate 7 to 8 mm protrusion and the blocks 6 to 7 mm apart in buccal segments
Compensatory lateral expansion of the upper arch by upper midline expansion screw to be turned once a week if necessary (why? prone to create buccal crossbite when mandible postured forward).
Reactivation of the blocks is possible if necessary for further advancement of mandible (how? A 2nd set of TB)
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TB
About 30% skeletal, 70% dentoalvelar
Increase lower anterior facial height
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WEAR
12-14 hrs-Andresen, Harvold, Bionator
Full-time- TB, Herbst, Frankel (except for eating and sports)
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TIMING
The pubertal growth spurt is the most rapid period of growth
Optimum changes could occur during this period
Thus appliance fitted just prior to the pubertal growth spurt (prepubertally)
PREDICT GROWTH!
Growth prediction is difficult: >1 yr incorrect prediction in 33% cases
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When is the best tiMe? (Proffit 1993)
1-3 years before peak of adolescent growth spurt
(approximately 10-11yrs old: girls, 12-13 yrs old: boys)-Houston, 1998
Common practice: to fit appliance in the mixed dentition, but difficult to manage when primary teeth are mobile and exfoliating
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When eruption of permanent teeth allows
If children treated too early, they are subjected to further treatment during the mixed dentition to maintain correction
2nd phase of comprehensive FA treatment in the early permanent dentition should be anticipated from the beginning
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Choice of appliance: Depends on
Patient factors Age
Compliance
Malocclusion
Clinician factors
Preference/familiarity
Lab/ facilities
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Effect of appliance
Dentoalveolar changes
Skeletal modification
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Dentoalveolar changes
The reduction of overjet and overbite in Class II malocclusion. The reduction in OJ and OB caused by:
Proclination of lower anterior Retraction of upper anteriors Differential eruption of teeth
Relative intrusion where the lower incisors are prevented from supraerupting and molar are allow to erupt. This causes opening of the bite or deep bite correction.
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Skeletal changesSkeletal changes are seen in both
maxilla and mandible.
In Class II
A. Midface restriction a. Restriction of forward
maxillary growth is observed
B. Mandibular growth induction
a. Growths acceleration of mandible take place
b. Change in condylar position
c. Glenoid fossa remodelling
d. Redirection of condylar growth
In class IIIA. Stimulation of
maxillary growthB. Restriction of
mandibular growth
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Success/ failure rate
Older patients had 34% failure rate
Younger patients 19% failure rate
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Problems
• Compliance• Most appliance procline lower incisors and retrocline
upper incisors• Lateral open bites created with Twin Block and
Harvold due to rapid correction• Frankel fragile prone to breakage• No detailed finishing allowed• May require 2nd phase of treatment which may
lengthen overall treatment time• Biological variability- do not all work in all patients• Relapse –should wear appliance overnight passively
as retainer
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Others..
TRAUMA :
Ulceration : Spring not positioned correctly and compress on soft tissue
Sharp acrylic
Overexpansion
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Thank you for listening!