Basic fundamental principles of myofuntional appliances.

1. AN INTRODUCTION TO
MYOFUNCTIONAL
APPLIANCES
Presented By :- Dr. Smriti (JR III)
Department of Orthodontics

2. MOYER’S - Functional Appliances are loose removable appliances
designed to alter neuromuscular environment of orofacial
region to improve occlusal development and/or
craniofacial skeletal growth.
PROFITT -
WHITE,GARDNER -
Functional Appliances are appliances which alter the
posture of mandible, holding it open or closed and forward
or backward.
A functional appliance harnesses natural forces which it
transmits to teeth and alveolar bone in a predetermined
direction.
INTRODUCTION

3. • According to Graber The term ‘Myofunctional appliances’ and
‘Functional appliances’ earlier have been used synonymously. However,
there are subtle differences between the two, Myofunctional appliances
are those appliances, which harness the muscle pressure to their
advantage and thereby affect tooth movement.
• Functional appliances are those appliances, which elicit certain natural
functions of the orofacial region and thereby affect results.

4. • However, with the understanding and sharing of ideas of both the
continents, the appliances, now is dictated by differential
morphogenetic, functional, growth and sex linked factors.

6. RETRODISCAL PAD “METABOLIC
PUMP”

7. • It Controls the condylar growth rate and endochondral ossification rate
• Governs both bone apposition and condylar growth direction at posterior
border of the ramus

8. • Mandibular condylar cartilage plays a crucial role in TMJ function. It
facilitates articulation with the TMJ disc and reduces point loads on the
underlying bone.
• It is of the fibrous type and is therefore structurally different from the
generally applied hyaline articular cartilage.
CONDYLAR CARTILAGE

9. • The cartilage layer on the mandibular condyle is from the articular
surface to the underlying bone, composed of several zones: the
fibrous, proliferative, mature and hypertrophic zones.
• Mandibular condylar cartilage differs from general articular
cartilage by the presence of type I collagen
• Shear strength has been suggested to originate from cross-links
between the collagen fibers

10. • In articular cartilage, collagen forms a three-dimensional network and thus
impacts its form, stability and tensile strength and resistance to shear forces.
• When cartilage is loaded by compression, the low permeability of the collagen
network impedes the interstitial fluid to flow through the collagen network.
This feature contributes to the viscoelastic properties of cartilage.

11. • The load-bearing functions of cartilage are mainly provided by the
viscoelastic property of collagen fiber network and the osmotic pressure
due to the presence of proteoglycans.
• Condylar cartilage of the TMJ is macroscopically similar in structure to
articular cartilage in other synovial joints, and also similar regarding
pathological changes. For instance, TMJ arthritis resembles knee or hip
arthritis largely.

12. CLASP KNIFE REFLEX

13. • Also called as autogenic inhibition, if one tries to stretch the muscle
forcibly , resistance is encountered as soon as the muscle is stretched
• This is a resistance due to the hyperactive reflex contraction of the
muscle in response to stretch
• If flexion is carried further forcibly a point is reached where all
resistance melts and the rigid limb collapses readily.
• The resistance resembles spring loaded folding knife blade which is
called “clasp knife reflex”.

14. • A muscle belly consists of large number of fasciculi.
• Each fasciculus consists of large number of muscle fibers.
• A single muscle fiber contains numerous myofibrils.
• The portion of a myofibril, in between any two successive Z lines is
called sarcomere.
MUSCLE PHYSIOLOGY

15. • Isometric contraction occurs when a muscle is simply resisting
an external force without any actual shortening.
• In an isotonic contraction, such as flexing the biceps, there is an
actual shortening
• The greatest strength of contraction is elicited when the muscle
approximates its resting length.

16. MYOTACTIC REFLEX

17. • Functional matrix theory is the most widely accepted theory of
craniofacial growth recently.
• Moss and Salentijn, have suggested that the craniofacial growth is the
result of the changes in functional matrix.
• Accordingly, neither bone nor cartilage is responsible for the growth of
the craniofacial skeleton.
FUNCTIONAL MATRIX THEORY

18. • The growth of the face, is formed by the growth of the soft tissues as a result
of functional requirements. The soft tissues grow; and bone and cartilage
react.
• Myofunctional applications can be used to obtain or alter functional stimulus
so that the current bone structure and form can be changed.
• Trabecular structure change that occurs as a result of forces applied to the
bone will cause morphological structure change in bone during craniofacial
growth stage

19. EQUILLIBRIUM THEORY
• An imbalance of force between tongue on one side and lip or
cheeks on the other normally is present.
• Forces produced by active metabolism in the periodontal
membrane stabilize the teeth against reasonable imbalances in
tongue and lip forces.
• In the short term, function adapts to changes in form.
• In the long term form adapts to function.

20. PIEZO ELECTRIC EFFECT

21. • Piezo electricity is a phenomenon observed in many crystalline materials
in which deformation of the crystal structure produces a flow of electric
current as a result displacement of electrons from one part of the crystal
lattice to the other.
• A small electric current is generated and bone is mechanically deformed.

22. FORCES
• The duration of force in most functional appliance treatment is
interrupted
• The direction of force for the movement of teeth should be consistent
• The magnitude of force is small in functional appliance therapy
• Applied force may be compressive or tensile. Depending on the type
applied, two treatment principles can be differentiated: force
application and force elimination

23. • In force application, compressive stress and strain act on the structures
involved, resulting in a primary alteration in form with a secondary
adaptation.
• The appliance wear by the patient results in compressive stress
transmission/ application directly or indirectly on the structures involved
(dentition and basal bone). This results in a primary alteration in function
and a secondary adaptation in form.
• Most of functional appliance (Removable and fixed) work on the principle.

24. • In force elimination, abnormal and restrictive environmental influences are
eliminated, allowing optimal development.
• The appliance wear by the patient results in elimination of abnormal and
restrictive muscular forces or other environmental factors which try to
modify the normal function and hence the proper form of the structures.
• The elimination of these aberrant forces restore the normal function and aids
in proper and normal development of orofacial structures.

25. • Its been classified as ‘Myotonic’ and ‘Myodynamic’
• Myotonic appliances
- Where it depends on the muscle mass for their action.
• Myodynamic appliances
- Depends on muscle activity for their function.
CLASSIFICATION

28. MECHANISM OF ACTION OF
FUNCTIONAL APPLIANCES
(a) Re-education of musculature
(b) Lateral pterygoid muscle stimulation
(c) Decreased biochemical feedback
(d) Unloading of mandibular condyle
(e) Transduction of viscoelastic forces
(f) Differential eruption of teeth.

29. (a)Re-education of musculature: Continous forward positioning of mandible in
skeletal Class II cases by functional appliance results in muscles learning a new
functional pattern.
(b)Lateral pterygoid muscle stimulation: The functional appliance wear results in
increased activity of superior head of lateral pterygoid muscle. This leads to
increased activity of retro discal pad and subsequent growth of condylar cartilage
on the posterio-superior aspect which results in sagittal growth of mandible

30. (c) Decreased biochemical feedback: The chondroblasts in the condyle secrete
a substance that retards mitotic activity of stem cells. This retardation acts as
a negative feedback.
• During functional appliance wear the lateral pterygoid is stimulated which
causes quick maturation of chondroblasts.
• This results in decreased secretion of the negative feedback material.
Removal of biochemical brake causes acceleration of condylar growth and
this increases mandibular sagittal growth.

31. (d) Unloading of condyle: During normal function of chewing, swallowing and
mandibular movements, the condyle is subjected to a lot of pressure and wear.
During functional appliance wear, the condyle is distracted from the glenoid
fossa, thereby providing an environment for matrix laying through meshwork of
blood capillaries and subsequent proliferation of cellular elements.
This results in growth of condyle at cartilaginous level and remodeling of glenoid
fossa and consequent increase in mandibular growth.

32. (e) Transduction of viscoelastic force: During wear functional appliances harness the
passive tension arising from the inherent elasticity in muscle, skin and tendinous
tissues and transmits it to the dentition.
(f) Differential eruption of teeth: Although functional appliances do not allow
unwanted tooth eruption, the eruption pattern is modified as per the need by placing
molar stops and by providing acrylic guide planes. Selective and favourable eruption
of teeth is also accomplished by trimming of the appliance(In case of Activator,
Bionator and Twin block).

33. INDICATIONS FOR FUNCTIONAL APPLIANCE
1) Patient should be in growing age.
2) Well aligned dental arches.
3) Posteriorly positioned mandible.
4) Severe skeletal discrepancy.
5) Lingual tipping of mandibular incisors.
6) Favourable growth pattern

34. CONTRAINDICATIONS
FOR FUNCTIONAL APPLIANCE
1) Class II skeletal due to maxillary prognathism.
2) Vertically directed grower.
3) Labial tipping of lower incisors.
4) Crowding

35. ADVANTAGES OF FUNCTIONAL APPLIANCE
1. It is used to manage certain types of malocclusions given during the mixed
dentition period or early permanent dentition period make use of growth potential
and bring about changes mainly in dental arches and improve the profile of the
patient.
2. It is used to eliminate the abnormal perioral muscle function which interferes the
normal bone growth.
3. Treatment can be started as early as in mixed dentition stage.

36. 4. These do not have any side effects of mechanotherapy such as
enamel decalcification, chronic inflammation of gingival.
5. It is easier to maintain oral hygiene with these appliances.

37. DISADVANTAGES OF FUNCTIONAL APPLIANCE
1. It is not useful in managing adult patients where the active growth period is
completed.
2. Patient’s ability to cooperate in following the instructions and wearing the appliance is
of vital importance in management of such cases.
3. It can be used to correct basal bone arch relationships only. And hence cannot correct
dental malocclusions like rotations, crowding etc.
4. Fixed appliance therapy may be required for final detailing or final tooth position.

39. REFERENCES
1. Graber T et al, Neumann B. Removable Orthodontic Appliances. Philadelphia:
WB Saunders Co.; 1984.
2. Begum et al. Current Approaches in Myofunctional Orthodontics (2009)
3. S. Kuroda et al. Biomechanical and biochemical characteristics of the
mandibular condylar cartilage (2016)
4. Abdul biass et al. Myofunctional Appliances: An Overview

40. Thank you