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 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 Re-educate the muscle Stimulate the lateral pterygoid muscle Unload the mandibular condyle Transduction of viscoelastic forces Differential eruption of teeth

1. Re-educate the musculature The mandible is continuously held forward in Class II cases. The muscle will ‘learn’ to adapt to the new pattern. Muscle adaptation takes place. 2. Stimulate the Lateral Pterygoid muscle

Functional Appliances Stimulation of lateral pterygoid muscle. Increased activity of the retrodiscal pad Growth of the condylar cartilage Posterior superior deposition of bone in condyle Saggital growth of mandible

3.Unload the condyle When the functional appliance is used, condyle is distracted from fossa. Facilitating an increased growth. Adaptation to the new position occurs through condylar growth

4. Transduction of viscoelastic force Functional appliances harness the passive tension arising from the inherent elasticity in muscle, skin and tendinous tissue and transmit to the dentition. 5. Differential eruption of teeth Eruption pattern is modified as per need such as placing molar stops and providing acrylic guide planes.

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

CLASSIFICATION Various 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 Clinician factors Age Compliance Malocclusion 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 changes Skeletal changes are seen in both maxilla and mandible. In Class II Midface restriction Restriction of forward maxillary growth is observed Mandibular growth induction Growths acceleration of mandible take place Change in condylar position Glenoid fossa remodelling Redirection of condylar growth In class III Stimulation of maxillary growth 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

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