Functional orthopaedic treatment aims to correct malocclusion and harmonize the orofacial function. Correcting class II malocclusion is difficult due to its complex and multifactorial aetiology. As several removable and fixed appliances are available the orthodontist can choose the appliance depending on patient’s needs. In this review article an attempt has been made to review various available fixed functional appliances.

Functional Appliances: A removable or fixed appliance which is designed to alter the posture of the mandible by stretching the musculature and changing the neuromuscular environment to produce movement of teeth and modification of growth [1]. Due to the bulk and inconvenience [2], their intermittent wear which does not elicit continuous muscle activity, Patient cooperation has long been recognized as an important factor in the outcome of orthodontic treatment. Failure of patient compliance to prescribed schedules of removable appliance wear will result either in slow treatment response or no response. To reduce these inadequacies, non-compliant appliances or fixed functional appliances were developed. An unfavourable response to functional appliances treatment can be summarized as due to excessive use, Poor or wrong diagnosis, Inadequate training, Poor knowledge of growth, Improper bite registration, Poor design/fabrication, Poor patient co-operation, Poor patient selection and Impatience of orthodontist. These factors combined with need for unprecedented demand for harnessing growth to its zenith led to the development of fixed functional appliances.

In the 19^th century, Norman Kingsley introduced bite plate for jumping the bite. He was the first to use the forward positioning of the mandible in orthodontic therapy. In the 20^th century, Pierre Robin (1867-1950), described the construction and properties of the monobloc. Cope JB showed that majority of class 2 corrections was due to dental rather than skeletal change. Clockwise or backward rotations were evident for the mandible. Weiland FJ and Bantleon gave a report of treatment of class 2 malocclusion with jasper jumper. It concluded that correction was a result of skeletal 40% and dental 60% changes.

Jasper JJ and McNamara gave an article describing in detail about anchorage preparation, torque application methods of anchoring, activating, and reactivating the modules. Carlos introduced the mandibular protraction appliance (MPA) for class 2 treatment. West R.P devised the adjustable bite corrector; it is a stretchable closed coil spring. Schiavaini et al described an attachment for Herbst appliance called the Mandibular Advancement Locking Unit (MALU). Korrodi Ritto invented the Magnetic Telescoping Device which linked a magnetic field to the functional appliance. Klapper Lewis (1999) introduced the Super spring II in non-complaint class II patient. Ritto described a Miniaturized Telescopic Device, the Ritto appliance. Cozza et al (2006) performed a systematic review of literature to evaluate the effectiveness of functional appliances in enhancing mandibular growth in class II subjects. Selmi Arici Huseyin Akan (2008) tested the hypothesis that functional appliance treatment in a group of class II div I patients with mandibular retrusion changes the condyle position in the glenoid fossa.

Herbst was a remarkable man, far ahead of his times. Herbst appliance was developed by in 1900s. Herbst presented the original banded design appliance for the first time at the 5th International Dental Congress in Berlin in 1909. It is a fixed bite jumping device. After 1934 very little was published about the Herbst appliance until it was rediscovered by Hans Pancherz of Malmo, Sweden in the late 1970’s. 

The Herbst appliance is basically a fixed bite jumping device used for correction of skeletal Class II malocclusions. A bilateral telescope mechanism forces the mandible in an anterior-forced position during all mandibular functions [4]. The telescope mechanism (tube and plunger) is attached to orthodontic bands, crowns, or splints. Herbst appliance (Figure 1) consists of 2 telescopic devices.

Figure 1: Herbst appliance.

Telescopic device consists of –

·         A tube

·         A plunger

·         2 pivots

·         2 screws

·         Pivot tube soldered to the permanent maxillary 1st molar band.

·         Pivot (plunger) to the mandibular 1st premolar band.

·         The screws prevent the telescopic parts from slipping off the pivots. The length of the tube determines the amount of advancement (bite jumping).

·         If the plunger is too long, it may extend far behind the tube & injure the buccal mucosa distal to upper 1st molar. To permit the lateral movements it may be necessary to widen the pivot opening.

The standard anchorage system used by Herbst:

·         Crowns on the maxillary permanent first molars and mandibular first premolars (sometimes canines).

·         Crowns joined by wires that run along the palatal surfaces of the upper teeth and the lingual surfaces of the lower teeth (Figure 2).

·         If upper second permanent molars have not erupted the appliance is anchored firmly by placing bands on the upper canines, which were soldered to the palatal arch wire as were the upper molars.

·         An alternative to bands on the upper canines is placing a thin gold wire on the labial surfaces of the upper incisors and soldered to the palatal arch wire.

Figure 2: Standard anchorage system used by Herbst.

Figure 3: The Cast Splint Herbst.

Figure 4: Herbst with stainless steel crowns.

Figure 5: Cantilevered Herbst appliance.

Figure 6: The EMDEN Herbst.

Figure 7: Edgewise bioprogressive Herbst appliance.

Figure 8: Flip-Lock herbst appliance.

Figure 9: Force module.

This appliance was introduced by Ralph M Clements and Alex Jacobson in 1982 [13] and was a substitute for intermaxillary elastics (Figure 10).

·         Piston

·         Cylinder

Locking devices

Figure 10: MARS appliance.

The MARS appliance is composed of a pair of telescopic struts (piston & cylinder of 0.045” thickness), the ends of which are attached to the upper and lower arch wires of a multi-banded fixed appliance by means of locking device. The appliance is placed after levelling and alignment is done. It is attached to the heaviest rectangular arch wires i.e. the wire that can be accommodated by the brackets and tubes.

Disadvantages: Need for a fixed multi-banded appliance limits its use in mixed dentition cases.

This appliance was developed by Carlos Martin & Coelho Filho in 1995 [14]. It was developed to be quickly made up by the orthodontist in the lab (Figure 11).

Figure 11: Mandibular protraction appliances.

MPA- I

A small loop is bent on each side at a right angle to the end of an 0.032” SS wire. Patient is asked to protrude the mandible into a position with proper overjet, overbite to determine the length of the tube. The distance from the mesial of the maxillary tube to the stop on the mandibular arch wire is measured. Another small right-angle circle is then bent in an opposite direction into the other end of the .032" stainless steel wire. One appliance circle is placed over the maxillary arch wire against the molar tube, and the other circle against the mandibular arch wire stop.

MPA- II

The right angles circle is made of 0.032” SS wire. A small piece of slipped coil is slipped over one of the wires. One end of each wire is then inserted through the loop in the other end. This version allows mouth to open wider than the previous version.

MPA- III

Appliance length measured from mesial of maxillary tube to mandibular arch wire stop with mandible in proper protruded position. This helps to eliminates arch wire stress that was experienced with MPA I and II. It permits a greater range of jaw motion while keeping the mandible in a protruded position. The MPA IV is much easier to construct and install, more comfortable. The MPA IV assembly consist of: “T” tubes, Upper molar locking pin, Mandibular rod, Mandibular arch wire.

Introduced by Richard P. West [15]. The assembly consists of: A stretchable closed coil spring made of 0.018” stainless steel and internally threaded end cap Nickel titanium wire in the centre lumen of the spring (Figure 12). The closed coil spring will stretch to about 25% beyond its original length without permanent deformation. The ABC can be used on either side of the mouth with a simple 180° rotation of the lower end cap to change its orientation. This reduces the inventory. The NiTi wire is responsible for the push force.

Figure 12: Adjustable bite corrector.

The Eureka Spring

Introduced by John DeVincenzo and Steve Prins [16]. It is a three-part telescopic appliance fixed to the upper arch at the level of the molar band and to the lower arch distal to the cuspid (Figure 13). The main component of the Eureka spring is an open coil spring encased in plunger assembly [17].

Figure 13: Eureka spring. 

The Churro Jumper

Introduced by Ridhardo Castanon, Mario S Valdes and Larry White [18]. It is an effective and inexpensive alternative force system for the anteroposterior. It was developed as an improvement of the MPA of Coelho. The distal circular end is attached to the maxillary molars by a pin and the mesial circular end is placed over the mandibular arch wire against the canine bracket (Figure 14).

Figure 14: Churro jumper 

Till date, this is the only flexible functional appliance which can be made up by the orthodontist making it cost effective.

The Ritto Appliance

The Ritto Appliance [19] (Figure 15) can be described as a miniaturized telescopic device with simplified intraoral application and activation. Its mechanism is of the ventral telescope without any disengagement. It comes in a single format which allows it to be used on both sides and is available in only one size. It is comfortable, easy to adapt, cost effective, esthetical and breakage resistant. Conventionally banding the upper and lower molars and placing brackets on the lower incisor makes it useful in mixed dentition. The appliance is fixed onto a prepared lower arch, its length is adjusted, locks are fitted, and the appliance is then inserted. It is activated by sliding the lock along the lower arch in the distal direction and then fixing it against the Ritto Appliance.

Figure 15: Ritto appliance.

Alpern Class II Closers

It consists of a small telescopic appliance with an interior coil spring and two hooks for fixing (Figure 16). It is fixed to the lower molar and to the upper cuspid like the elastics. Its telescopic action eases opening of the mouth.

Figure 16: Alpern class II closers.

The Mandibular Anterior Repositioning Appliance (MARA)

This was created by Douglas Toll of Germany in 1991. It consists of shim on the molars, the elbow fits in the shim and guides the patient to bite into Class I. If the patient pulls back his mandible to a Class II relation, he will be unable to achieve intercuspation (Figure 17). This means that the lower molars will make direct contact with the metal, giving an unpleasant sensation. The appliance design allows for use in conjunction with braces.

Figure 17: The Mandibular Anterior Repositioning Appliance (MARA).

Introduced by Lewis Klapper in 1997 [20]. It is a flexible spring element which rests in the vestibule when activated and is attached to the maxillary molar and the mandibular canine. The open helical loop of the spring is twisted like a J-hook onto the mandibular arch wire (Figure 18). On the maxillary end it is attached to the standard headgear tube (Super Spring I) or to a special oval tube and secured with a stainless-steel ligature (Super Spring II). This new version prevents any lateral movements of the spring in the vestibule. The horizontal configuration of the attachment wire at the maxillary molar tube permits distalization with good radicular control.

Figure 18: The Klapper Super Spring I & II.

Forsus-Fatigue Resistant Device

This is an innovative three telescopic appliance with a coil spring in its exterior part [21]. It is available in different length sizes for left and right side (Figure 19). In the original presentation, the appliance is placed in the mandible on the round-segmented arch. The appliance slides along the arch and helps opening of the mouth and lateral movements. Since the resulting force concentrates more on the anterior and inferior sectors. There is no interference with continuous arches used during the treatment. The appliance may be fixed according to the needs of the patient. The appliance may be used in mixed dentition cases and for dental asymmetry correction. The device allows the patient free mouth opening. Similar device is the forsus nitinol flat spring which presents a Nitinol flat wire instead of the coil. The appliance’s flat surface is more esthetical and comfortable. It is available in three different designs, with various molar attachments. The Forsus Nitinol Flat Spring is slim, flat, and made of Super-Elastic Nitinol. Force levels remain constant from the initial setup to the time of removal.

Figure 19: FORSUS.

It has a ready-to-use concept [22], eliminating the need for measuring, or assembly or appliance manipulation. It does not need gingival headgear tubes or special band assemblies and can be used with either banded or bonded tubes (Figure 20). 

Figure 20: PowerScope.

Features

·         It has one-size-fits which reduces inventory requirement [23]

·         It features a low profile which gives aesthetic appearance. Its smooth and rounded-edge design provides better patient comfort. Its telescopic system features will not disengage during treatment, thus avoid unnecessary emergency visits. Ulceration is not seen as the piston does not extend distally.

·         A NiTi internal spring mechanism delivers 260 grams of force for continuous activation during treatment. Painful pinching of the cheeks and food entrapment is avoided by enclosed design [24]. The ball-and-socket joint helps lateral mandibular movement for improved patient comfort and acceptance.

The AdvanSync combines two distinct treatment phases i.e. mandibular advancement along with malocclusion correction. Therefore, it helps in to achieve skeletal as well as dental corrections at the same time; hence reduces treatment time [25].

AdvanSync is designed to advance the mandible to a Class I occlusion within six to nine months – while the patient has been bonded upper and lower 5 to 5 [26-30]. Since it is fixed it does not need patient compliance. Its compact design provides maximum comfort and range of movement. It is placed simultaneously with initial bonding, synchronizing Class II treatment with orthodontic therapy [31-35] (Figure 21).

Figure 21: AdvanSync.

·         The factors affecting mandibular growth with functional appliances are more important and should be considered, rather than concentrating on short term results. Significant mandibular growth and long-term retention basis are still debatable. Because of individual differences in growth rates and direction may explain some of the discrepancies reported in clinical studies in human beings. This may also be one of the reasons, in some reports there increased condylar growth, whereas in other investigation it was of minor clinical value

·         Another area, where we have still lack of knowledge is soft tissue changes and adaptations after functional appliance therapy.

·         Future long-term studies, clinical trials with control group, are required to know whether we can grow mandibles and retain it for lifetime.

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