PRINCIPLES OF FUNCTIONAL APPLIANCE

THERAPYDr 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

Problem with appliance

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

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

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

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.

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

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.

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….)

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

INDICATIONS : b. DENTAL

“Classic” case: uncrowded, well aligned

Functional appliance have non-mechanism for treating irregularities of alignment of teeth

INDICATIONS : c. SKELETAL

Commonly:

Moderate to severe Class II skeletal base

Normal to low MMPA

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)

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

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

TYPES OF FUNCTIONAL APPLIANCE

TWIN BLOCK

THE ANDRESEN ACTIVATOR

THE HARVOLD ACTIVATOR

HERBST APPLIANCE

MEDIUM OPENING ACTIVATOR

BIONATOR

FRANKEL APPLIANCE

Others

Twin block appliance The upper and lower parts fit together using posterior bite

blocks with interlocking biteplanes which posture the mandible forward

The Andresen Activator

Monoblock

Loose, difficult to tolerate

To correct the Class II

buccal segment

Buccal facetting to aid

posterior eruption

The Harvold Activator Based on Andresen design

Wider opening

Guidance of eruption,

Can be use with Fixed App

Maximum effect from

stretching muscle.

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.

Medium Opening Activator

A one-piece appliance to reduce deep OB

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.

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

Twin block appliance The upper and lower parts fit together using posterior bite

blocks with interlocking biteplanes which posture the mandible forward

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

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

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

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)

TB

About 30% skeletal, 70% dentoalvelar

Increase lower anterior facial height

WEAR

12-14 hrs-Andresen, Harvold, Bionator

Full-time- TB, Herbst, Frankel (except for eating and sports)

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

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

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

Choice of appliance: Depends on

Patient factors Age

Compliance

Malocclusion

Clinician factors

Preference/familiarity

Lab/ facilities

Effect of appliance

Dentoalveolar changes

Skeletal modification

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.

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

Success/ failure rate

Older patients had 34% failure rate

Younger patients 19% failure rate

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

Others..

TRAUMA :

Ulceration : Spring not positioned correctly and compress on soft tissue

Sharp acrylic

Overexpansion

Thank you for listening!