Functional Appliance

1. Functional Appliance - Dr. Adelegan O.A.

2. Outline Introduction Brief History of Removable Appliances Definition of Functional Appliances Classification Components Clinical management Impression Bite Registration Timing of growth modification Advantages Disadvantages

3. History of Removable Appliance In USA, Victor Hugo Jackson was the chief proponent of removable appliance among the pioneer orthodontist in the early 20th century. At that time neither the modern plastic for baseplate material nor stainless steel wire were available. What he used was vulcanite bases and precious metals or nickel silver wires In early 1900s, George Crozat developed a removable appliance which consisted of effective claps on molars. Heavy gold wires as framework and a light gold wire to produce desired tooth movement.

4. For a variety of reasons, development of removable appliance continued in Europe but neglected in USA because Angle dogmatic approach to occlusion with emphasis on precise tooth positioning has less impact in Europe social welfare system developed more rapidly in Europe than USA with emphases on a limited orthodontic treatment for a large number of people which is carried out by general practitioners rather than orthodontists precious metals for fixed appliances were not readily available in Europe because of their social welfare and also because its use was banned in dentistry

5. A major part of European removable orthodontic appliance of this period was Functional Appliance. In the European approach of the mid 20th century. Removable appliance was differentiated into Active plates for tooth movement Functional appliance for growth modification

6. Definition of Functional Appilance A functional appliance is an orthodontics appliance that is used to alter the position of the mandible either by holding it open or by holding it open and forward. Pressure created by the stretch of the muscles and soft tissues are transmitted to the dental and skeletal structures, moving teeth and modifying growth. A functional appliance could perhaps be called mandibular displacing device.

7. Definition of Functional Appliance (Cont’d) The term functional appliance is an abbreviation of myofunctional appliance which is what such devices were called in Britain during the 1950s and 1960s. The prefix “myo” was later dropped in USA to distinguish this term from treatment from the then popular myofunctional therapy which was directed at muscles or restraining to alter some so called oral habits

8. Definition of Functional Appliance (Cont’d) The monoblock designed by Pierre Robin which was used in neonates with micromandible and cleft lip and palate (Pierre Robin Syndrome) was the forerunner of functional appliance, but the activator developed in Norway by Andresen in the 1920s was the 1st functional appliance to be widely accepted.

9. Classification of Functional Appliances Passive tooth borne Andresen Havold Bionator Twin block Active tooth borne Orthopaedic Correction Tuescher’s Appliance Van Beek headgear activator Stockil headgear activator Tissue Borne Frankel Appliance

10. Classification of Functional Appliances cont’d Removable All functional appliance except Herbst Fixed Herbst being the only fixed appliance

11. Classification of Functional Appliances cont’d Graber and Neumann Classification Those that displace the mandible to a moderate degree and are intended to stimulate muscle activity i.e. myodynamic – Bionator and Andresen Those that induce more extreme displacement and rely on the elastic properties of the muscles and facia for their action (myotonic) e.g. Havold

12. Classification of Functional Appliances cont’d Isaac et al Rigid – Andresen Havold Bionator More Flexible – Frankel appliance

13. Activators The original functional appliance design was a block of plastic covering the teeth of both arches and the palate, made to fit loosely, advance the mandible several mm for class II correction and open the bite 3 -4 mm. The appliance (Andresen) has the following features Lingual flange extension – stimulate the forward position of the mandible A labial bow for control of maxillary anterior teeth An acrylic cap over the lower incisors to control both eruption and mesial movement A facets or flutes in the acrylic to direct the eruption of the posterior teeth mesially in lower arch and distally and buccally in the upper arch. In the current design, i.e. Wood side activator, the facets is replaced by a plastic (acrylic) shelf which impede the eruption of the upper posterior teeth. It also has the other features as above

14. Mechanism of action of Andresen It is fitted in the mouth with the mandible postured forward. As a result, tension is generated in the muscle (temporalis muscle) and the transmitted force of the muscles help to retract the mandible, tends to move the upper buccal teeth distally and upper anterior teeth lingually through the pressure by the labia bow (but this can be prevented by not activating the labial bow) while the reciprocal force will tend to bring the lower teeth forward.

15. Mechanism of action of Andresen Forward postures of the mandible also stimulate the growth centres of the mandibular condyles so there is increase in growth of the mandible and thus helps to reduce or eliminate the discrepancy in jaw relationship The Andresen appliance is worn 10 – 12 hrs a day. Because it is monoblock, patient can’t speak with it It is better worn after school and at night till morning

16. BIONATOR (Balter’s type) Similar to Andresen, but the bulk of palatal coverage is eliminated. Also has three variants Standard appliance for class II correction A screening appliance for elimination of abnormal tongue activity Reverse appliance for treatment of class III

17. Herbst Appliance It is the only fixed functional appliance It consists of mandibular and maxillary arches splinted with frameworks that are usually cemented or bonded (but can be removable) and connected with a pin-end-tube device that holds the mandible forward. The jaw position is controlled by the pin and tube device. Pressure the teeth can produce significant tooth movement in addition to an effects. Despite the fact that it is fixed the dental versus skeletal effect depend on patient’s compliance.

18. Advantages of Herbst appliance It works 24 hrs a day Patient co-operation not required Treatment time is short (6 – 8 mths)

19. TWIN BLOCK (Clark appliance) It can also be used as removable or fixed. The twin block appliance consists of individual maxillary and mandibular plates with ramps that guide the mandible forward as the patient closes down. The maxillary and mandibular portions are configured so that interaction of the 2 parts controls how much the mandible is postured forward and how much the jaws are separated vertically. It is similar to the Herbst in that pressure against the teeth rather than the mucosa is employed to bring the jaw forward

20. TWIN BLOCK (Clark appliance) Advantages It allows nearly a full range of mandibular movement Easy acclimatization Reasonable speech Disadvantage Displacement of the mandible can occur freely despite the absence of active springs or screws

21. Havold appliance It is a modification of the Andresen appliance. It has an occlusal shelves which contact with the upper but not the lower posterior teeth, thus allowing the lower posterior teeth to erupt and move mesially and correct the molar relationship from class II to class I

22. Active Tooth borne appliance They are modification of activators and bionators designs that include expansion screws or springs to move the teeth. In the correction of a class II malocclusion as the patient moves the lower jaw forward in a class I position, a crossbite tendency is usually apparent, therefore transverse expansion of the upper arch is nearly always needed, so the springs or screws in active functional appliances were added to the basic design to provide this expansion. But in many cases, an additional goal may be further expansion of the upper and lower arches to correct crowding.

23. Tissue borne appliances Frankel appliance or function regulator is the only tissue borne appliance. It consists of acrylic shields which lie in the vestibule of the mouth, both labiallly and buccally. It also consist of small lingual pad which lie against the lingual mucosa beneath the lower incisors, which stimulate mandibular repositioning. Much of the appliances is located in the vestibule however and it alter both mandibular posture and the contour of facial soft tissues. It serves as an arch expansion appliance in addition to its effect on jaw growth because the arches tend to expand when lip and cheek pressure is removed.

24. Mechanism of Action of Functional Appliance The exact mode of action is not known but there are different postulations Eruption guidance – this is a mechanism whereby the vertical development of a group of teeth can be enhanced, inhibited or redirected and thus assist alteration of occlusal relationship. Basically, there is a belief that if vertical eruption of teeth is prevented, the forward and upward movement of the teeth is prevented

25. Mandibular reposturing – the appliances are constructed in such a way that the mandible is held in a postured position and with the teeth out of occlusion, the overall effect of this is altered-bony development. The mandibular repositioning has been known to have the following Redirection or retardation of the horizontal growth of the maxillar, the basal area of the maxillar is restrained in their normal forward growth. The anterior downward rotation of the maxillar is enhanced

26. Tipping movement – this movement occurs in both labial and buccal teeth. This can occur as a result of contact between the appliance and the teeth

27. Components of functional appliance Each functional appliance, no matter what name it carries is simply a melding of wires and plastic components. The appliance consists of – Functional component which generate forces by altering posture of the mandible, changing soft tissue pressure against the teeth or both A tooth controlling components. Although the functional components are the heart of the appliance, they only constitute a small portion of the total appliance, the bulk of which is devoted to controlling the position of the teeth

28. Functional component Lingual flanges (which rests against the alveolar mucosa below the mandibular molars). It provides the stimulus to posture the mandible forward The lingual pads (which contacts the mucosa below the lower incisors). It also provide stimulus to posture the mandible forward. Contact of the pad or flange with soft tissue (alveolar mucosa) not the teeth is the key to mandibular repositioning. If they contact the mandibular incisor, they can produce a labially directed force against these teeth as the mandible attempt to return to normal resting posture. For this reason, activators and bionators are usually relieved behind the lower incisors.

29. Functional component (Cont’d) Ramps supported by the teeth are another mechanism for posturing the mandible forward. the sliding pin and tube device – also force the mandible to be positioned forward by holding the teeth lip pads (which is positioned low in the vestibule labially) force the lip musculature to stretch during function.It is considered as an adjunct to mandibular repositioning rather than a primary functional component.

30. Tooth controlling component Arch expansion components Buccal shields and wires to hold the soft tissue away from the teeth. The effect is to distrupt the tongue and cheek equilibrium and this inturn lead to facial movement of the teeth and arch expansion Expansion screws and screens – can be use to actively increase the transverse diameter of the arches or to modify the anterior-posterior dimension of the appliance.

31. Tooth controlling component vertical control component acrylic or wires – when placed in contact with a tooth and the vertical dimension is opened past the normal postural position, the stretch of the soft tissues will exact and intrinsic force on the teeth. Intrusion does not usually occur probably the because the force is not constant, but if the patient wears the appliance often, eruption is impeded. Thus the presence or absence of incisal or occlusal stops including bite blocks provide a way of controlling the vertical position of anterior and posterior teeth allowing teeth to erupt where this is desirable and preventing it where it is not. Lingual shields – remove the resting tongue from between the teeth. This has the effect of enhancing tooth eruption.

32. Tooth controlling component Stabilizing components. Claps – this help to retain the functional appliance in position in the mouth. Though it was thought in early days of functional appliance and a loose fit was important and therefore claps were contraindicated, it is clear now that growth effect with or without clasps is remarkably similar. Clasps help the first time wearer to adapt to the appliancel. They can be used initially and then removed or deactivated if desired when the patient has learned to wear the appliance Labial bow – across the maxillary incisors in many functional appliances should be considered as a stabilizing component. Its purpose is to help guide the appliance into proper position, not to tip the upper incisors lingually. For this reason, labial bow is adjusted not to touch the teeth when the appliance is seated in position. Torquing springs – which contact the incisors in the cervical 1/3 are aimed at counteracting the tipping movement often produced by a labial bow.

33. Clinical management of functional appliance :Impression The impression for functional appliance differ from those of other ortho diagnostic records in two important ways Areas where appliance component will contact soft tissue must be clearly delineated. Most appliances use contact with the lingual mucosa to stimulate forward posturing of the mandible, so this is a critical area. The impression must include the alveolar process below the lower molars if long lingual flanges are to be employed. The impression must not stretch and excessively displace soft tissues in an area of contact with the appliance. This is critical when lip pads and buccal shields are planned. Too much extension of the impression will result in pads and shields that are too long and will cause soft tissue irritation and ulceration when the appliance is worn

34. Clinical management of functional appliance: Bite Registration The construction of bite for the functional appliance for class II patients advances the mandible so that the condyles are out of the fossae and separate the jaw by predetermined amount. In clinical practice, the mandible is advanced to 7 to 8 mm. Greater advancement may lead to patient’s discomfort which can reduce compliance. For most patients, initial advancement is limited to 4 to 6mm. The vertical opening depends on the appliance design and purpose With franckel appliance, the minimum opening is 3 to 4mm. This amount of space is necessary for connectors between the facial and the lingual components of the appliance With interocclusal stop or facet to guide the eruption, about 4-5mm vertical opening is needed. If bite blocks to limit posterior eruption are planned, 5 – 6mm of separation are needed.

35. Timing of growth modification Whatever the kind of appliance that is used or growth effect desired, if growth is to be modified, the patient has to be growing. Growth modification has to be done before the adolescent growth spurt ends. In theory, it could be done at any time up to that time. Because of the rapid growth exhibited by children during the primary dentition years, it would seem that treatment of jaw discrepancies by growth modification should be successful at a very early age

36. Timing of growth modification cont’d The rationale for treatment at ages 4 – 6 would be that the cause of the rapid rate of growth, significant amount of skeletal discrepancies would be overcome in short time. This implies that once discrepancies in jaw relationships are corrected, proper function would harmonious growth thereafter without further treatment. Unfortunately, although most antero-posterior and vertical problems can be treated during he primary dentition years, relapse occurs because of continued growth in the original disproportionate pattern. If children are treated very early, they usually need further treatment during the mixed dentition and again in the early permanent dentition to maintain the correction

37. Timing of growth modification cont’d The opposite point of view will be that since treatment in permanent dentition will be required anyway, there is no point in starting treatment until then. But delaying treatment that long has two potential problems By the time the canines, premolar and second molars erupt, there may not be enough growth remaining for effective modification, especially in girls The child will be denied the psychosocial and functional benefit of treatment during an important period of development. A child can benefit from treatment during the pre-adolescent years if aesthetic and resultant social problems are substantial or if he or she is trauma-prone.

38. Advantages of functional appliances It utilises the growth potential of dental arches to the maximum and can achieve a better facial profile than conventional appliances treatment can be commenced in the mixed dentition and can be effective during pubertal growth spurt minimal chair side time is required less frequent adjustment it is economical it is the only appliance that brings about true skeletal changes

39. Disadvantages of Functional Appliances Precise control of tooth position is not possible variable response in post-pubertal patients and it is ineffective in adults not suitable for cases where crowding is present with the exception of fixed functional appliance, it is totally dependent on patients cooperation. it is bulky and often unpleasant to wear

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