Fixed Functional Appliances - A Classification
Yazan: Korrodi Ritto (D.D.S., Ph.D.)
Functional orthopedic treatment seeks to correct malocclusions and harmonize the shape of the dental arch and oro-facial functions.
Removable functional appliances are normally very large in size, have unstable fixation, cause discomfort, lack tactile sensibility, exert pressure on the mucous (encouraging gingivitis), reduce space for the tongue, cause difficulties in deglutition and speech and very often affect aesthetic appearance. The alteration in the mandibular posture creates added difficulties. These adverse effects make the adaptation and acceptance of these appliances more difficult1,2 (Oliver and Knappman, 1985; Ngan et al., 1989). Fixed functional appliances first appeared in 1900 when Emil Herbst3 (Herbst E., 1910) presented his system at the Berlin International Dental Congress. Since then and up to the seventies, very little was published on this appliance. It was at that time that Hans Pancherz4 (Pancherz H., 1979) brought the subject back into discussion with the publication of several articles on the Herbst.
It was only in the eighties that several systems derived from Herbstís work started to appear. A number of fixed appliances have gained popularity in recent years to help achieve better results in non-compliant patients.
Fixed functional appliances are normally known as "non-compliance Class II correctors" giving a false idea about the co-operation necessary during treatment. In reality, when we compare them to removable appliances, we can clearly recognize fixed appliances as non-compliance devices. However, for treatment to be successful, good co-operation is always necessary, especially if skeletal modifications instead of dentoalveolar compensation are desired. The aim of this article is to update the classification of fixed functional appliances, published in 2000 in "The Functional Orthodontist". Their clinical applications will be listed and a description of how they work will be given. The advantages that some have over others will also be discussed.
Fixed functional systems have some advantages over removable systems. They are designed to be used 24 hours a day, which means that there is a continuous stimulus for mandibular growth. They are smaller in size permitting better adaptation to functions such as a mastication, swallowing, speech and breathing.
Fixed functional appliances are usually described as non-compliance Class II devices, which are able to treat Class II malocclusions successfully, while reducing the need for patient co-operation and overall treatment time. It is possible to treat this type of malocclusion with minimal effort. Just as the name implies, what distinguishes them from removable appliances is that it is impossible for the patient to remove them. What we have therefore, is an appliance that allows greater control by the orthodontist.
These appliances are fixed on the upper and lower arches. Since the application of force is transmitted directly to the teeth through a support system, the main disadvantage that may be encountered is dental movement that takes place during treatment which may not be the most suitable for the type of malocclusion in question. In an attempt to avoid this unwanted dental movement and as a way of finding an appliance that allows easy adaptation by the patient, various fixed functional appliances have appeared in recent years.
Fixed functional appliances can be classified as either flexible (Flexible Fixed Functional Appliance - FFFA) or rigid (Rigid Fixed Functional Appliance - RFFA).
Flexible Fixed Functional Appliances
Flexible fixed functional appliances (FFFA) can be described as an inter-maxillary torsion coils, or fixed springs. Elasticity and flexibility are the main characteristics of flexible appliances. They allow great freedom of movement of the mandible. Lateral movements can be carried out with ease. The major drawbacks with these appliances are the propensity with which fractures can occur both in the appliance itself (mainly in areas that have more acute angles) and in the support system (mainly in the lower arch). If on one hand flexibility is an advantage, on the other hand it does tend to produce fatigue in the springs. Another drawback is the tendency of the patient to chew on the appliance, possibly contributing to breakage or damage. While it is not possible for the patient to completely open his mouth, depending on the way the system is fixed onto the lower arch, good opening can be achieved.
It is important to tell patients to avoid opening their mouths too widely because this could result in breakage. Also, they are not very aesthetic appliances. When the curvature of the spring is accentuated, some protuberances can appear in the cheeks. Several appliances have come on to the market since the eighties featuring variations on the covering and type of springs, method of fixation and replaceability of fractured components. The covering used on the springs makes the appliance more comfortable and hygienic as food does not accumulate inside the spring. A disadvantage is that the covering can degrade quite quickly, especially if the patient bites on the appliance. The ability to replace components is important, as fractures are an unavoidable reality. These appliances are expensive, therefore, a system that allows the replacement of some of its components can reduce the cost of treatment. This leads to another disadvantage: the inventory of material that must be kept. Almost all are sold in kits of various sizes which contain components for both the left and right side. It is not always possible to treat a patient with only one size making it necessary to replace it with a larger size. Once again, this increases costs.
FFFAs can be used in the treatment of Class I, II division 1 and 2 and III malocclusions. The intention when they first appeared was for the treatment of Class II, both in malocclusions characterized by a mandibular deficiency as well as in cases where a dental problem predominated. Later on, their application extended to Class I problems especially when treatment including extraction was foreseen. The appliance was used as an anchorage reinforcement or even for molar distalization. The appliance is also used in a reverse type for treatment of Class III malocclusions, as well as in cases of midline discrepancy. The type of the force exercised by FFFAs is continuous and elastic in nature. The amount of force is variable in accordance with the skeletal pattern of the patient, the type of movement desired and the size of the cusps. Normally, in brachyfacial cases, due to their strong musculature, it is necessary to use more force (greater activation) than in dolicofacial cases. The height of the dental cusps is a factor to bear in mind when treating with FFFAs. If the patient has high cusps with good intercuspation, it will be necessary to exert greater activation on the spring. If the large size of the cusps is linked to a brachyfacial skeletal pattern with strong musculature, we can predict a difficult clinical scenario and the appliance will be prone to fracture.
If an advance of the mandible is required as when treating a retromandibular case, the force exerted has to be greater than that used when only dental movement is desired to distalize the upper molar and procline the lower incisors. If the goal of the treatment is to achieve dentoalveolar movements, the appliance should be activated minimally by placing a slight bow in the force module. To maximize the dentoalveolar movements in the upper arch and minimize any loss of anchorage in the lower, the upper archwire is not tied back. FFFA produces a "headgear" effect on the maxillary dentition due to the intrusive force applied to the maxillary posterior segments and produces an anterior intrusive force on the lower dentition. It can be used to obtain maximum anchorage, holding upper molars back as the upper incisors are retracted. Due to the intrusive force on the upper molars, a posterior open bite is common as well as posterior expansion due to the deflected force module. Another unwanted common movement is the tendency for the lower molar to rotate mesiobuccally, causing a mild posterior crossbite especially when the second molars have not been banded. Some buccal expansion in the upper and lower arches is to be expected, and placing bands on the second molars will aid final alignment. Placing a transpalatal or lingual arch during the force activation stage will help control unwanted buccal expansion of both arches. Loss of occlusion adds to instability, especially in the transverse dimension.
The most unwanted dental movement is proclination of lower incisors. To avoid this effect, good anchorage preparation should be carried out. However, in a brachyfacial pattern with strong musculature this movement would be expected. To increase anchorage to avoid unwanted dental movements, various additional systems can be used, such as a transpalatal bar, lingual arches or lower incisor brackets with lingual torque. It is advantageous to start the treatment in adolescent patients when the majority of permanent teeth have erupted and 12-year molars can be banded. FFFAs are not recommended in mixed dentition, especially late mixed dentition to avoid unwanted dental movements. Proper anchorage preparation is critical to achieving successful results. It is necessary to align and level arches before placing the final wire and activating the force module. A .017" x .025" or .018" x .025 stainless steel archwire should be placed before inserting the FFFA. By fully engaging the brackets in both arches, especially the lower, anchorage is maintained during the activation of the force module, preventing unwanted mesial movement of the lower incisors and distal movement of the uppers. When proclining the lower incisors is desired as in in Class II division 2 it may be advantageous to use a .016" x .022" stainless steel archwire as a final wire.
All FFFAs allow the patient to close in centric relation.
When the patient closes in centric relation, the contour of the bow should be significantly increased. By slightly overactivating the appliance in centric relation, the patient will automatically position the mandible forward. This is a natural response to decrease the force module and alleviate discomfort. The upper archwire should be cinched to increase anchorage and minimize dentoalveolar movements. Despite the clinical references available in published work about skeletal effects produced by a bite-jumping mechanism with a FFFA, no current scientific research would be found. Very few articles were published and these only report clinical cases. This is in contract to the data available for the RFFA 14-23.
Found in this group were:
1 - The Jasper Jumper 16,17 (Jaspar J., 1987) (American Orthodontics, 1714 Cambridge Avenue Sheboygan, WI 53082-1048, USA).
This was the first FFFA to appear (Fig.1a and 1b).
It is made up of a covered spring and is marketed in a kit of different sizes with both left and right sides. It is accompanied by a quite thorough instruction manual. It is also an appliance which is more comfortable for the patient because of its covering. Potential disadvantages are: the large inventory that must be kept, the coating material may degrade and fractures can occur with some frequency. The majority of articles published on FFFAs are about the Jasper Jumper. However, they are few in number, are comprised of mainly clinical cases, and rarely refer to the skeletal and dental changes seen in treatment groups or comparative studies.
2 - The Amoric Torsion Coils23 (Amoric M., 1994)
This appliance is made up of two springs, one of which slides inside the other (Fig.2). They are intermaxillary springs without covering and have a simplified application system of rings on the ends. These rings are fixed to the upper and lower arches with double ligatures.
They are marketed in one size only and are bilateral. A large stock of material is therefore, not necessary. The force exerted by the appliance is variable in accordance with the fixing points on the arch.
3 - The Adjustable Bite Corrector14 (Richard P. West, 1995) (Orthoplus, Inc., 1275 Fourth St., Suite 381, Santa Rosa, CA 95404)
This is an appliance which is assembled by the orthodontist as it is composed of various pieces - caps, closed coil springs, nickel titanium wire (Fig.3).
It can be used on either side of the mouth with a simple 180ļ rotation of the lower end cap to change its orientation. This reduces the inventory by as much as one half. In the center lumen of the spring we find a nickel titanium wire which is responsible for the "push" force generated. Repairs and replacements are rapid and easily carried out with this kit. The cost of repair is minor.
4 - The Scandee Tubular Jumper (Saga Dental AS, 2201 Kongsvinger, Norway).
This is a coated intermaxillary torsion spring sold in a kit which includes the spring, the covering, the connectors, the ballpins and the glue (Figs.4a and 4b). There is no distinction between left and right.
The covering can be of different colors making it more attractive for patients. The orthodontist constructs the appliance, cutting the spring to the length seen fit. When a fracture occurs, it is only necessary to replace individual components. It has the drawback of being thick after the covering is applied.
5 - The Klapper Super Spring15 (Lewis Klapper, 1999) (Trademark of Orthodesign, 744 Falls Circle, Lake Forest, IL 60045).
This is a flexible spring element which is attached between the maxillary molar and the mandibular canine (Fig.5). The length of the element causes it to rest in the vestibule when activated. This facilitates hygiene and avoids oclusal surfaces.
The ends (fixing points) are different:
The open helical loop of the spring is twisted like a J-hook onto the mandibular archwire. 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 movement of the spring in the vestibule.
Only two prefabricated sizes are available (with left and right versions of each). The length of the spring can be increased or decreased by simply bending the attachment wires. The horizontal configuration of the attachment wire at the maxillary molar tube permits distalization with good radicular control.
6 - The Bite Fixer (Ormco 1717 West Collins Avenue, Orange, CA 92867)
This is a new intermaxillary spring coil. The spring is attached and crimped to the end fitting to prevent breakage between the spring and the end fitting. Polyurethane tubing is inside the spring to prevent it from becoming a food trap (Figs.6a and 6b).
The Bite Fixer is supplied in a kit with various sizes for both left and right.
7 - The Churro Jumper21 (Castañon R. et al., 1998)
This is an inexpensive alternative force system for the anteroposterior correction of Class II and Class III malocclusions (Fig.7).
The mesial and distal end of the jumper are circles. The distal circle is attached to the maxillary molars by a pin and the mesial end is placed over the mandibular archwire against the canine bracket. So far, this is the only flexible functional appliance which can be made up by the orthodontist in his lab. The costs are reduced and the time spent is minimal.
Rigid Fixed functional appliances - RFFA
These appliances have two distinct differences in relation to FFFAs:
- RFFAs do not easily fracture but neither do they have elasticity or flexibility.
- After fitting and activation they do not allow the patient to close in centric relation. This means that the mandible is in a forward position 24 hours a day creating greater stimulus for mandibular growth than with FFFAs.
Their appearance dates from the beginning of the century and their main indication is for the treatment of Classes II malocclusions. Basically, correction consists of advancing the mandible to a forced anterior position to stimulate growth and harmonize skeletal defects. The majority of these appliances do not adapt to the treatment of Class III cases. The working of RFFAs is based on a telescopic mechanism which encourages forward repositioning of the lower jaw as the patient closes into occlusion. Numerous published articles can be found that describe their method of application, function and expected results over the short and long term. The skeletal effects produced with this type of appliance are greater than with FFFAs and are well described24-39. Only at the end of the eighties did different designs for RFFAs appear. Alternatives were also developed for fixation which sought to allow greater freedom of mandibular movement and also to avoid unwanted dental movement, especially that related to intrusion and vestibular inclination of the lower incisors.
Variations on the Herbst appliance and similar systems, utilizing ball attachments have appeared on the market in an attempt to:
- improve patient comfort and acceptance
- cause fewer clinical problems compared to screw or pin attachments
- reduce the frequency of emergency appointments
- allow good lateral mandibular movements
- allow easy application in splints for correction in mixed dentition
To ensure a perfect fit into the ball attachments, great accuracy is required when welding attachments. Nor is it possible to have lower brackets or fixed appliance at the same time, unless other systems are resorted to such as a cantilever or mini-tubes which require greater laboratory time.
1 - The Herbst Appliance3,4 (Herbst E., 1910; Pancherz H., 1979) (Dentaurum, Inc, 10 Pheasant Run, Newtown, PA 18940).
The Herbst appliance was first described by Emil Herbst in 1905 at the Berlin Dental Congress. After that very little was written on this appliance until the end of the seventies when Hans Pancherz brought it back into discussion with the publication of a series of articles4, 38, 39.
The Herbst appliance consists of two tubes, two plungers, axles and screws. The original device is a banded Herbst design. The Herbst appliance has undergone some changes in its original design but since the seventies has maintained its general shape with only a few modifications taking place with regard to methods of application (Type I, II and IV).
Type I is characterized by a fixing system to the crowns or bands through the use of screws. This is the most common form. It is necessary to weld the axles to the bands or crowns and then fix the tubes and plungers with the screws (Fig.8).
Type II has a fixing system that fits directly onto the archwires through the use of screws. This method of application has the disadvantage of causing constant fractures in the archwires. The lack of flexibility together with the difficulty in lateral movements and the stress placed on the archwires through activation causes fractures, especially in the lower arch (Fig.9).
Type IV has a fixation system with a ball attachment, which allows greater flexibility and freedom of mandibular movement. A disadvantage in relation to other similar appliances is the fact that it needs brakes to stabilize the joint. The brakes are small and sometime difficult to fit. When a fracture occurs or a brake is lost, the appliance comes loose (Fig.10).
The first articles published describe a banded Herbst design that involved the fitting of bands on the upper molars and first premolars with the bands connected by a lingual wire. In the mandible, bands were placed on the lower first premolars, and connected by a lower lingual arch. Later on, the banded version of the appliance was modified to incorporate additional anchorage units:
- Bands were placed on all first premolars and all first molars and both buccal and lingual wires connected the premolars and molar bands.
- The use of stainless steel crowns instead of bands has been advocated.
- The ball attachment appeared as an alternative to screws.
2- The Cantilevered Bite Jumper (Ormco 1717 West Collins Avenue, Orange, CA 92867)
More recently, the use of a cantilever has been proposed (Fig.11). The biggest difference resides in the fact that the Herbst style appliance is fitted directly to the lower molar bands through a cantilever arm. This system means that crowns have to be fitted to the upper and lower molars. The cantilever secured to the mandibular stainless steel crowns has a disadvantage in that the thickness of the screw mechanism can impinge on the patientís cheek. The parts are available in kit form with pre-welded screw mechanisms and cantilever arms on crowns of seven different sizes.
3- MALU Herbst Appliance (Saga Dental Supply A/S, postboks 216, Kongsviner, Norway)
The MALU - Mandibular Advancement Locking Unit is a recently developed attachment device for the Herbst (Fig.12). It consists of two tubes, two plungers, two upper "Mobee" hinges with ball pins and two lower key hinges with brass pins.
The major advantages are the lower cost, no laboratory needed, flexibility and the possibility of using combined with edgewise therapy24,35. Each upper Mobee hinge is inserted into the hole at the end of the MALU tube and secured to the first molar headgear tube with ball pin. Each lower key hinge is inserted into the hole at the end of the plunger and locked to the base arch, distal to the cuspid, with the brass pin.
4 - Flip-Lock Herbst Appliance (TP Orthodontics, Inc., 100 Center Plaza, LaPorte, IN 46350).
This is the third generation of ball-joint Herbst appliances available from this company. The first generation was made from a dense polysulfone plastic but breakage occurred because of the forces generated within the ball-joint attachment (Fig.13).
In the second generation, the plastic was replaced with metal (Fig.14). However, fracture problems persisted.
The third generation is made of a horse-shoe ball joint (Fig.15). This system has proved to be more efficient than the previous models, both in terms of application as well as its resistance to fracture40 (Miller R., 1996).
One of the advantages of this appliance over other similar appliances with a ball joint, is that it is thinner and smaller which means greater patient comfort.
5 - The Ventral Telescope (Professional Positioners, Inc., 2525 Three Mile Road, Racine Wisconsin 53404 - 1328).
This was the first telescopic RFFA that appeared as a single unit; i.e. upon reaching maximum opening it does not come apart (Figs.16 a, b, and c).
This appliance is available in two sizes and fixing is achieved through ball attachments. It is particularly easy to activate. The operation is simple and is carried out by unscrewing the tube thus allowing an activation of around 3 mm. Its disadvantages lie in the fact that it is quite thick and suffers from fractures to the brake which stabilizes the joint. As with the other appliances where fixing is achieved through ball attachments, great accuracy is necessary with regard to inclination and the welding of components.
6 - The Magnetic Telescopic Device41 (Ritto A.K., 1997 and author of this article)
This consists of two tubes and two plungers with a semi-circular section and with NdFeB magnets placed in such a manner that a repelling force is exerted (Fig.17). Fitting is achieved by using the MALU system.
This appliance has the advantage of linking a magnetic field to the functional appliance. Its main disadvantages are its thickness, the laboratory work necessary to prepare it and the covering of the magnets.
7- The Mandibular Protraction Appliance7-9 (MPA) (Filho C., 1995, 1997, 1998)
This is an RFFA which was developed to be quickly made up by the orthodontist in the laboratory (Fig.18).
Its advantages include ease of manufacture, low cost, infrequent breakage, patient comfort and rapid fitting. Another advantage it offers is that it can be made up at any time. This is helpful when there has been a failure in the supply of other commercially available appliances or if the orthodontist practices in an area where it is difficult to quickly obtain certain other alternatives.
The designer of the MPA developed three different types:
MPA I - each side of the appliance is made by bending a small loop at a right angle to the end of an .032" SS wire. The length of the appliance is then determined by protruding the mandible and another small right-angle circle is then bent in an opposite direction. The appliance slides distally along the mandibular archwire and mesially along the maxillary archwire. Bicuspid brackets must be debonded. Limited mouth opening is the major disadvantage.
MPA II - this is made by making right-angles circles in two pieces of .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 wire. This version allows the mouth to open wider than the first version.
MPA III - This version eliminates much of the archwire stress that occurs with the MPA I and II. It permits a greater range of jaw movement while keeping the mandible in a protruded position. It is adaptable to either Class II or Class III malocclusions.nIt resembles the Herbst by also incorporating a telescoping mechanism but is smaller in size. It requires more time to be built and a good electronic welder that does not darken or weaken the wire.
8- The Universal Bite Jumper5 (UBJ) (Calvez X., 1998).
This is like a Herbst but is smaller in size and more versatile - it can be used in all phases of treatment in mixed or permanent dentition, Class II or III malocclusions. An active coil spring can be added if necessary (Fig.19).
No laboratory preparation is required. It is fitted in the patientís mouth and cut to the appropriate length for the desired mandibular advancement. Activations are made by crimping 2-4 mm splint bushings onto the rods. UBJs with nickel titanium coil springs do not need to be reactivated.
9- The BioPedic Appliance (GAC International, Inc., 185 Oval Drive, Central Islip, NY 11722 - 1402).
This is a bite jumping appliance which is engaged on the maxillary and mandibular molars, using a cantilever like system. It is then attached to a BioPedic buccal tube (Fig.20).
Activation is achieved by sliding the appliance along the buccal tube and fixing the screw. It is universally sized for left and right sides.Two pivots on the ends allow the appliance to be rotated when the patient opens his mouth.
10 - The Mandibular Anterior Repositioning Appliance6 (MARA) (AOA, 13931 Spring Street, PO Box 725, Sturtevant, WI 53177).
This was created by Douglas Toll of Germany in 1991. It consisted of cams on the molars which guided the patient to bite into Class I (Fig.21).
The first molars have to be covered with stainless steel crowns and the appliance must be laboratory manufactured.
The patient can pull back his mandible to a Class II relation but will be unable to achieve intercuspidation. This means that the lower molars will make direct contact with the metal, giving an unpleasant sensation. Furthermore, should the orthodontist opt for bands instead of crowns, fractures will often occur. The appliance design allows for use in conjunction with braces. It can be used for Class II treatment and for TMJ problems.
In our opinion, this is an appliance of simple characteristics which allows good hygiene during the correction stage. With a small modification to the original design using only wire and composite, a very interesting appliance can be created for finishing treatment of a Class II malocclusion treated with a functional appliance.
11 - The IST - Appliance (Sheu Dental, 58613 Iserlohn, Germany).
The Intraoral Snoring-Therapy Appliance is a new device designed by Hinz in order to treat patients who suffers from breathing problems during sleep, e.g. obstructive sleep apnea (Fig.22 a and b). According to the inventor, the IST appliance suppresses snoring by moving the lower jaw forward reducing the obstruction in the pharyngeal area.
Fig 22 a
Fig 22 b
The device offers two very important advantages:
- The telescope is threaded so the orthodontist can change the protrusion on each side individually up to 8mm.
- An end stop in the guiding sleeve prevents the telescope from disengaging.
The appliance is available in two different lengths.
12 - The Ritto Appliance10-13 (Ritto A.K., 1998 and author of this article)
The Ritto Appliance can be described as a miniaturized telescopic device with simplified intraoral application and activation (Fig.23 a and b).
Fig 23 a
Fig 23 b
The construction of this appliance is based on the mechanism and function used in the Ventral Telescope adapted for use in conjunction with a fixed appliance.
The main differences when compared to the Ventral Telescope appliance are:
- The appliance does not come apart (no disengagement after achieving maximum extension).
- The smaller size facilitates adaptation and it does not affect aesthetic appearance or speech.
- It comes in a single format which allows it to be used on both sides and is available in only one size.
The Ritto Appliance is simple to use, comfortable, cost effective, breakage resistant and requires no patient cooperation. The fact that the appliance does not disengage creates enormous advantages. It eliminates the time lost in measuring length before fitting, as in other appliances. This feature makes it possible to fit the appliance in approximately 5 minutes and remove it in about half that time. It is even possible to carry out the treatment of Class II retromandibular cases in mixed or permanent dentition using only conventional bands on the upper molars and two tubes on the lower molars and brackets on the lower incisors.
Fixation accessories consist of a steel ball pin and a lock (Fig.24). Upper fixation is carried out by placing a steel ball pin from the distal into the .045 headgear tube on the upper molar band, through the appliance eyelet and then bending it back as shown in (Fig.25).
The appliance is fixed onto a prepared the lower arch. The thickness and type of arch is chosen, its length is adjusted, locks are fitted and the Ritto appliance is then inserted (Fig.26).
Fig 26 a
Fig 26 b
Activation is achieved by sliding the lock along the lower arch in the distal direction and then fixing it against the Ritto Appliance (Fig.27).
The most common question raised after the presentation of this appliance is on the effect produced on the lower incisors, given that the lower anchorage system is minimal. In a comparative study between the Ritto Appliance and the Herbst appliance, no statistically significant differences were found in the position of the lower incisors (II to A/pog; II to Pancherz plan). In a scanogram analysis of the lower incisors, no indication of radicular resorption was found during treatment with the appliance. According to the authors, these results are due to the fact the protocol with regard to patient selection was closely followed as were the 3 keys for the success of treatment25. Many orthodontists may have experienced the frustration of continual breakage which discourages the use of fixed functional appliances (FFAs).
In functional treatment with a rigid fixed functional appliance (RFFA), it is necessary to prepare the patient for 1 to 2 months before fitting the appliance to stimulate musculature and avoid having the patient exert too much force on the support systems, causing appliance breakage or unwanted dental movement. For this reason, the use of a mini-stimulator for mandibular advancement is advised. This is a thermoformed splint of 0.7 mm in thickness, for the upper incisors only and incorporating an acrylic bite block for the lower incisors. The bite block is constructed with the mandible in a forward position (Fig.28).
For the first 15 days or 1 month, the patient should wear the splint for as long as possible and maintain the lower incisors fitted into the Bite block. In the following weeks, the patient should practice swallowing exercises with the lips in contact and with lower incisors against the bite block.
Only after this stage should therapy be started with the Ritto Appliance, now that the musculature has been stimulated and the patient has memorized the forward position of the mandible. Delocking of the occlusion is also achieved.
It is possible to fit the Ritto appliance in conjunction with the mini stimulator for the first few weeks (Fig. 29).
Another important factor that contributes to comfort and rapid patient adaptation is the establishment of posterior contact after the advancement of the mandible. This also creates a posterior proprioceptive sense. It is not always necessary to have perfect coordination of the arches before starting functional treatment. Sometimes, even with a pronounced Curve of Spee, therapy can be started as long as some artificial contacts are constructed with composites on the molars (Figs.30 a, b, c, d, e, f). The extrusion of the premolars can be beneficial in the correction of a vertical problem.
Fig 30 a
Fig 30 b
Fig 30 c
Fig 30 d
Fig 30 e
Fig 30 f
There are also new appliances that can been classified as hybrid appliances because they represent the combination of a rigid fixed functional appliance (RFFA) with flexible fixed functional appliance (FFFA). They could be described as rigid appliances with coilspring-type systems. The objective of these appliances is to move the teeth by applying 24-hour elastic continuous force that would replace the traditional use of elastics and extra-oral force. Their common feature the use of coiled springs to produce this force. The force generated varies between 150 and 200 gm. Other advantages include reduction in the need for patient cooperation and the ease of placement.
We should be aware that the primary objective of the hybrid appliances is not to reposition the mandible anteriorly. If such was the case, it would be illogical to reposition a mandible and at the same time to keep exerting mesial inferior and distal superior force. Rigid fixed functional appliances offer the best choice to obtain this goal, as is well documented in the literature. With RFFAs, once the appliance has been activated the patient cannot close in centric relation during the therapy stage. In order to obtain the best possible results with a goal of skeletal movement, the author proposes a philosophy of using muscular pre-stimulation before the placement of the fixed appliance. This is in conjunction with a treatment plan based on an individualized pattern model. (The subject of the individualized pattern model will be presented in a subsequent article in this journal. A general inconvenience with rigid fixed functional appliances is the fact that the fixed appliance needs to be placed as a whole, to establish the necessary anchorage. Also, control of the vestibular movement of the lower incisors is important. In such cases it is sometimes necessary to resort to other anchorage appliances. As such, it can be rather difficult to use these appliances in mixed dentition.
THE CALIBRATED FORCE MODULE
It was a fixed appliance designed to substitute Class II elastics and it was developed in 1988 by the CorMar Inc. Available in three sizes, it was applied to the inferior arch close to the molars and fixed by a screw, and mesial or distal to upper cuspids, and also fixed to the arch. Its coil spring produced a force between 150 and 200 gm (Fig.31).
The same company proposed a Herbst appliance with an exterior coil spring, attached to the inferior tube. That system generated tooth movement by employing gentle and continuous force 24 hours a day (Fig.32).
This appliance appeared on the market in 1996 and it was developed by DeVicenzo and Steve Prins. 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. A detailed userís manual with all the indications and instructions for its use accompanies the appliance. The appliance has an open coil spring that is placed inside of a part of the system. Interestingly the authors caution in the manual that the appliance does not create any orthopedic effect, but underline that the correction is totally dentoalveolar. The placement system is relatively simple, and the patient can open his or her mouth widely without any difficulties due to the telescopic effect of the appliance. It is available in two sizes: 20 and 23 mm long. The appliance is universal and it can be applied both to the right as well as to the left side (Fig.33).
THE TWIN FORCE BITE CORRECTORTM
This appliance differs from others in form and constitution because it has two internal coil springs. It consists of two joint telescopic systems. At the superior level it is fixed with a ball pin that is fitted into the buccal tube of a molar band. The placement in the lower arch is slightly different; it involves a fitting-in system that is later fixed with a screw to the inferior arch. Normally it is placed distal to the lower cuspid. Generally this type of fixing allows for rapid placement and removal of the appliance. It is available in two sizes and accompanied by a screwdriver to fix the screw in the lower arch. Such as in the previous appliance its application vary between Class II and Class III treatment, and it may be also used as an anchorage system. In our opinion, due to its original configuration, these appliances are suitable for cases where there is a need to carry out correction that requires predominantly dentoalveolar movement. In order to avoid protrusion of the lower incisors it is recommended to use stronger steel wires or to resort to other accessories.
The major drawback of this appliance is the difficulty to control the force. If we want less force, we should bend the mesial part of the ball pin in order to have more wire distal to the tube. This situation, however, may create discomfort and impingement problems (Fig.34, 35).
The other disadvantage lies in the fact that the lower the lower dentition needs to be already aligned as it is recommended to use 016"x.022, or 017"x.025" stainless steel wires that guarantee necessary anchorage. In this way the device is in principle recommended for permanent dentition.
For Class III correction it is necessary to put a lip bumper tube (LBT) on the lower molar band.
Recently the third modernized version of the appliance has been presented under the name "Twin Force Bite Corrector - Double Lock" (Fig.36). It is reduced in size and both the lower and upper placement is based on the system of lock-on screws. This new version facilitates the use of the appliance for Class III correction and it allows for a slightly better control of the force although it still falls short of the full control.
FORSUSTM - FATIGUE RESISTANT DEVICE
This is an innovative three telescopic appliance with a coil spring in its exterior part. This feature makes it resemble some flexible functional appliances (AFF).
In comparison with AFF its great advantage lies in coil spring resistance to breaking. The coil spring is applied by its sliding on a rigid surface avoiding in this way angulations at the fixing points.
It is sold in kits that include different length sizes for left and right side (Fig.37).
In the original presentation the appliance is placed in the mandible on the round-segmented arch that is included in the kit. The appliance slides along the arch and facilitates opening of the mouth and lateral movements. The resulting force concentrates more on the anterior and inferior sectors.
In this way there is no interference with continuous arches used during the treatment, which offers wide application independently of the method applied.
The appliance may be fixed in various ways according to the needs of the patient (Fig38, 39).
The device gives you the power to control the amount of force, whether through various available sizes, or through the direct attachment to the lower arch and the use of a stop for activation. Thus the appliance may be used in cases of mixed dentition and it allows for dental asymmetry correction when higher force on both sides is needed.
The device allows your patient to open and move their jaw freely.
Another device from the same company is the FORSUSTM NITINOL FLAT SPRING which presents a Nitinol flat wire instead of the coil (Fig.40,41).
The applianceís flat surface is more esthetically acceptable and it offers more comfort. It is available in various sizes for different patients or to get more activation. Forsus Nitinol Flat Spring requires no laboratory setup, making chairside installation quick and easy. The Forsus Nitinol Flat Springs, available in three different bypass designs, accommodate a variety of molar attachments making it compatible with your current appliance system. This flexibility eliminates your need for specialty molar attachments and reduces your inventory of bands and tubes. The Forsus Nitinol Flat Spring is slim, flat and made of Super-Elastic Nitinol. Nitinol is always at work, delivering consistent forces. Force levels remain constant from the initial setup to the time of removal. The result is faster, more efficient treatment.
ALPERN CLASS II CLOSERS
This appliance is slightly different from the preceding ones and it is also the most recent. It is predominantly applied in Class II correction and as a substitute for elastics. It consists of a small telescopic appliance with an interior coil spring and two hooks for fixing (Fig. 42).
It functions in the same way as elastics and, similarly, is fixed to the lower molar and to the upper cuspid. It is available in three different sizes. Its telescopic action enables a comfortable opening of the mouth.
Relying on published articles to date, we can state that FFFAs as well as Hybrid appliances produce greater dental movement during treatment than RFFAs. This is due to the type of force they produce. They also allow the patient to close in centric relation during the therapy stage. In our opinion, these appliances are suitable for cases where there is a need to carry out correction that requires predominantly dento-alveolar movement.
When RFFAs initially appeared, they were intended for the correction of Class II retrusive mandibles. They are considered to be excellent functional appliances and are considered as non-invasive orthopedic appliances similar to rapid maxillary expanders. Their method of activation is quite different from that of FFFAs given that the patient cannot close in centric relation during treatment. The mandible is in a forward position for 24 hours a day and the type of force exerted by the appliance is a postural variable force. Their main indication is Class II skeletal cases, where it is necessary to advance the mandible to stimulate growth and harmonize skeletal defects. Dental movement with both appliances is always achievable. If in some cases we can take advantage of this benefit, in others we have to try and impede more common dental movements, especially movement related to the labial version of the lower incisors. For many years now various methods have been suggested to increase anchorage with a view toward avoiding unwanted dental movements. Lingual arches, the thickness of the arch wires, the introduction of torque in the arch wires and the use of lower incisor brackets with lingual torque are some examples. The evolution of support systems is, in our opinion, a backward step in the scientific and technological progress that is foreseen for the next century. Initially, appliances were supported on bands, then came the use of rigid bands, connections welded to the bands, the introduction of crowns on the upper molars and then on the crowns on all molars and sometimes on the lower pre-molars. The introduction of the cantilever increased further still the thickness of the wires that were being used as means of support.
In our 11 years of experience with the Ritto Appliance, we have come to the conclusion that the "devolution" of the other systems is not the functional philosophy for the next century. In addition to considerable time lost in the laboratory and the associated cost, it also means an increase in treatment time and discomfort for the patient. Too much time is spent fitting crowns, cementing, waiting in the lab, removing the appliance for repairs and refitting and recementing bands for finishing. This is a highly uncomfortable experience for the patient. We have found with the Ritto appliance that to avoid breakage problems and unwanted dental movements, and to be successful with the treatment, it is extremely important to prepare the patient and stimulate the musculature with the mini splint before fitting the RFFAs. This can be achieved in 6 weeks.
The qualities that functional appliances should present can be summarized as follows:
- Patient comfort and acceptance are excellent
- They promote better compliance
- They offer an extensive range of motion
- They are simple and inexpensive
- They are easier to fit
- They are adaptable to either Class II or III
- They can be used for mandibular positioning or dentoalveolar movement
- They cause less breakage of archwires and appliances and thus fewer emergency appointments
- Inventory requirements are minimal - The appliance can be used on either side of the mouth and there is only one size
- They can be used at any stage of treatment - mixed or permanent
- Their low profile results in considerably less buccal irritation
- They produce good results without the need for patient cooperation.
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