1. PRINCIPLES OF FUNCTIONAL APPLIANCE THERAPY
Dr Diana Md Zahid

2. 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

3. 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

4. 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

5. 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

6. 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.

7. MECHANISM OF ACTION Re-educate the muscle
Stimulate the lateral pterygoid muscle
Unload the mandibular condyle
Transduction of viscoelastic forces
Differential eruption of teeth

9. 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

10. 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

11. 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

12. 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.

13. 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.

14. 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….)

15. 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

16. INDICATIONS : b. DENTAL “Classic” case: uncrowded, well aligned
Functional appliance have non-mechanism for treating irregularities of alignment of teeth

17. INDICATIONS : c. SKELETAL
Commonly:
Moderate to severe Class II skeletal base
Normal to low MMPA

18. 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)

19. 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

20. 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

21. TYPES OF FUNCTIONAL APPLIANCE
TWIN BLOCK
THE ANDRESEN ACTIVATOR
THE HARVOLD ACTIVATOR
HERBST APPLIANCE
MEDIUM OPENING ACTIVATOR
BIONATOR
FRANKEL APPLIANCE
Others

22. Twin block appliance
The upper and lower parts fit together using posterior bite blocks with interlocking biteplanes which posture the mandible forward

23. The Andresen Activator
Monoblock
Loose, difficult to tolerate
To correct the Class II
buccal segment
Buccal facetting to aid
posterior eruption

24. The Harvold Activator Based on Andresen design Wider opening
Guidance of eruption,
Can be use with Fixed App
Maximum effect from
stretching muscle.

25. 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.

26. Medium Opening Activator
A one-piece appliance to reduce deep OB

27. 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.

28. 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

29. Twin block appliance
The upper and lower parts fit together using posterior bite blocks with interlocking biteplanes which posture the mandible forward

30. 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

31. 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

32. 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

33. 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)

35. TB About 30% skeletal, 70% dentoalvelar
Increase lower anterior facial height

36. WEAR 12-14 hrs-Andresen, Harvold, Bionator
Full-time- TB, Herbst, Frankel (except for eating and sports)

37. 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

38. When is the best tiMe? (Proffit 1993)
1-3 years before peak of adolescent growth spurt
(approximately 10-11yrs old: girls, 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

39. 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

40. Choice of appliance: Depends on
Patient factors
Clinician factors
Age
Compliance
Malocclusion
Preference/familiarity
Lab/ facilities

41. Effect of appliance
Dentoalveolar changes
Skeletal modification

42. 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.

43. 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

44. Success/ failure rate Older patients had 34% failure rate
Younger patients 19% failure rate

45. 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

47. Others..
TRAUMA :
Ulceration : Spring not positioned correctly and compress on soft tissue
Sharp acrylic
Overexpansion

48. Thank you for listening!