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Expansion WITH REMOVABLE APPLIANCES INDIAN DENTAL ACADEMY Leader in continuing dental education

Historical background Narrow maxilla was recognizes for thousand years and Hippocrates referred to it A number of crude techniques may be gleaned from the works of early dental practitioners Fauchard (1728), Fox (1803), Delabarre (1819), and many others until Walter coffin demonstrated the expansion of the maxillary arch using a spring which caused separation of the mid palatal suture in children.

In 1860 Emerson c . Angell placed a screw between maxillary premolars of a girl aged 14 years and widen her arch in two weeks. The essential passage read “ this apparatus was placed in the mouth. when the shaft was made to revolve until the fixture was made uniformly firm, when the patient was provided with the key and instructed to keep the shaft as uniformly tight as possible. These instructions were industriously followed and at the end of two weeks ,the jaw was widened as to leave a space between two front incisors ,as indicated in diagram no 2, showing conclusively that the maxillary bone had been separated whilst the upper left lateral incisor had been brought outside the inferior teeth� This bold statement introduced what was to go down as a landmark in dental science and placed Angell ahead of his time.

Great debate of twentieth century With this started great debate for slow expansion or rapid expansion. Dr E.H.Angle stood for expansion but was against the use of plates which he said was unhygienic. His dogmatic approach and such was his influence that all plated appliance was left for the banded ones even in American south where crozat were commonly used . Although fixed plates continued in Europe which was away from his influence. In 1939 A.M.Schwarz wrote a textbook on removable appliances providing others how to use fixed plates . America was unaware of ad Vance's on removable appliances as was Europe was to fixed ones.


On The Basis Of Direction Expansion Expansion in lateral direction (unilateral / bi-lateral) e.g. in treatment of the buccal crossbites

Expansion in the antero-posterior region (unilateral /bi-lateral )e.g. treatment in anterior cross-bite cases.

Expansion in the antero-posterior as well as in lateral direction.e.g. “Y� shaped expansion screw Expansion for distalization of segment of the teeth e.g. of canine and molars











Treatment with them will not provide the best answer to every orthodontic problem. Some small degrees of irregularity are impossible to treat and some severe malocclusions respond well. Easily designed to produce tooth movements labio- and buccolingually and mesio-distally.

Active plates Functional activators

Removable appliances can be designed easily to produce tooth movements labio- and bucco-lingually and mesiodistally. Removable appliances have many advantages they exert minimal interference with dentoalveolar growth. They are useful during the developing stages of dentition. Treatment with them at early stages is attractive as it offers early completion dtes and little inconvenience during socially and educationally busy years for the growing child.

Orthodontic Force The objective of orthodontic force is to move teeth individually or in units, using other teeth, both supported and unsupported, for anchorage . Orthodontic forces are ideally measured in grams and ounces, optimum tooth movement occurs with relatively mild forces, whether they are continuous or intermittent. They are usually directed toward a small area, such as the periodontal membrane of a tooth or teeth.

Orthodontic forces are always applied directly to the teeth, the kineses being supplied by arch wires, intermaxillary elastic, intramaxillary elastics, light extraoral force, bite plates, and other auxiliaries. It is intended that certain teeth move while others, hopefully, remain stationary.

Maxillo-Thorax -Myotherapy. These expanding exercises in conjunction along with macary activator have been forgotten but should be reconsidered when using functional methods

Disadvantages Require precise design and accurate construction. Patient co-operation is must. Difficult to obtain two point contact on tooth to obtain complex tooth movements.

Factors important for design of active plates

Pressure sources. Clasps. Anchorage . Base plate.

Coffin spring Indications :1. upper arch expansion where lateral expansion is indicated. it can be used in cases of unilateral as well as bi lateral crossbites. 2. Antero-posterior expansion required 3. Differential expansion in anterior or posterior region is desired .controlled movement can be obtained. 4. When space requirement is less than 3 mm.

Design Constructed from 1.25mm wire. Two types can be prepared i.e. Tear shaped Diamond

• With the help of universal pliers a generous loop in the shape of tear or a diamond shape is prepared. It is kept 1 mm away from the palate.

Tags are prepared at the end of the wire to be embedded in the acrylic. Four Adams clasps are prepared on the first molars and first molars for retention. Acrylization can be done with direct method. Originally the base plate was made in one piece and cut with fine saw after vulcanization. Present day practice is to make the base plate in two small segments, large enough to make contact all the teeth to be moved and contain the tags of the of the clasp and the wire

It should be seated high up on the palatal vault to increase acceptance in patients. Anterior bends may not be incorporated in acrylic to permit full range of action . As an alternate to screws plates it is cheaper and less bulky but unless precise construction and adjustment these may be rather unstable.


Pits are drilled into the base plates allow the initial width of the appliance to be checked with calipers .the spring is expanded anteriorly first, then posteriorly by pulling it apart, care being taken not to twist the appliance. This easier and quicker than adjustment with pliers. An expansion of 2-3 mm will generally be appropriate


Activating upper plate


Open activators of Klammt it is combination of the original activator and bite former. it is particularly important in cases of a narrow maxilla with a distal bite. Schmuth incorporated a coffin spring in original Balters bionator and was known as functional kybernator it was small and could be worn full time thus all the more effective.

Crozat appliance George crozat developed a removable appliance fabricated entirely of precious metal in 1920 that is still used effectively. Fabrication is simple but handling appreciably hard It consisted of an effective clasp for first molar teeth modified from the Jackson design. heavy gold wire for framework and lighter gold finger spring for tooth movement.

It was flexible and superior than other alternatives available that time. Specialist with crozat appliance can achieve dental arch expansion Distal movement of canine, premolar and molars. Single tooth movement including bodily movement Correction of anterior crowding and protrusion Required great effort and skill.

Expansion screw The expansion screw is a very small metallic appliance which may be designed to move a single tooth or a group of teeth or the skeletal bases as required. This screw as a source of force together with the acrylic segment of the plate effect the teeth and the alveolar process. Different type of screws may be used advantageously for certain procedure during treatment with removable appliance .

The screw normally transmits its forces by means of acrylic. Which comes in contact with the teeth. The patient usually activates the screw once or twice a week. Fairly high force is generated but it is intermittent in nature. Desirable features in screw are adequate travel, stability and minimal bulk. Screws can be used for various tooth movements but they add up to the bulk of the appliance making it bulky. Screws are useful in antero-posterior and transverse arch expansion and also in contracting a wide arch.

Expansion screw

Single and double guide pin screws are available the latter are more stable but requires more space . Problems tend to occur with screws, some tend to turn back under load. If the appliance is left out it will not be possible for the patient to re insert it and treatment may be delayed As activation at any time is small (0.2mm) large force generated is acceptable .tooth moves within the limits of the periodontal ligaments and excessive hyalinization will not be produced . Spring loaded screws are available but they offer few clinical advantages.

According to desired action of screw Expansion screw appliance used to widen a dental arch.

Appliance with screw to move individual teeth or small group of teeth in a buccal or a labial direction . Appliance with screw to move individual teeth or small group of teeth in a mesial or a distal direction

Positioning of screw Rules and guidelines for screw positioning: It is positioned in three dimensions accurately. It should be placed in the mid line oriented to median raphe when bi-lateral expansion is to be planned .screw lies on a imaginary line passing between the first and second premolar. In a narrow arch it should be positioned more posteriorly

The horizontal plane of the screw is placed parallel to the plane of the occlusal surface. Orientation determines the line of force not the cut in the acrylic. With the tag it is positioned with the arrow pointing in the right direction. wax is added to prevent its dislodgement

Key is inserted in the hole and when turned .metal end plates move apart or closer if closing screw is used Guide pins prevent the end plates from rotating and enhance appliance stability The screw is not placed parallel to the palatal vault, rather it should be turned about 45* forward so that child can activate it himself

It is adjusted by only a small amount at one time due to its rigidity. otherwise appliance cannot be inserted. After teeth move it can be moved again. Pitch of the screw is set so that the tissue does not get harm during expansion a complete turn of 360* will produce a separation of 0.8 -1mm .

The screw when turned 90* will produce separation of 0.2mm. That means the periodontal ligaments gets narrower by 0.1mm on each side. this is a mil reduction thus do not cause excessive hyalinization and also creates ideal orthodontic condition for the transformation of the bone.

In children when expanding 90*turn at each adjustment is sufficient and adjustment is made twice a week. In adults tooth movement has to be carried out more slowly so a 45* turn or1/4th turn per week is suffiecent .

Advantages Controlled movement can be achieved. Activation can be done at home. Various types of tooth movement possible. . It is easily available commercially do not require skill of the clinician Can be added to suffix the fuctional appliances

Disadvantages Reliance on the patient for the activation. May cause difficulty in cleaning. Does not applies a constant force. Requires excellent retention . Over- activation may cause problem.

Bertoni screw for selected arch expansion and for labial movement of upper incisor

Special screws for circular expansion

Screw for symmetrical expansion

Distal screw for upper right posterior segment

Maxillary plate combined with the three special screws attempt at anterior movement, distal movement, and segmental expansion

Appliances Active plate It is an horse shoe shaped and covers only anterior and lateral parts of the palate contain a expansion screw in the middle. The limits of lower plate is determined by the height of the alveolar process. This is not so critical as retention depends on clasps and appurtenances of the appliance. These make use of the forces that are in second degree of efficiency.

To obtain the effect the plate should be secured in place against the palatal tissue. An important general rule is that difference between the force and the counteracting resistance must be large as possible in favor of the resistance. As the screw is turned the plate act as true orthographic –jaw orthopaedics appliance not only against the teeth themselves but also against the lateral walls of the palate. This capacity of plate appliance to carry pressure directly to the bony parts of the arches as well as the teeth may even provide stimulation to the center of growth along median palatal suture.

With adjustment of the active plate sore spots are likely to appear they must be removed by selective grinding. To effect minor tooth movement with active plate, it is important to remove the peripheral margin off the appliance next to the coronal portion of the teeth, usually at the gingival margin. One must keep in mind that only does the tooth move , but so do the gingival tissue and the contiguous alveolar bone It is wise therefore to reduce the appliance sufficiently to permit all the tissues to move when n there is doubt it is always better to remove too much that too little

A removable appliance impinging on gingival tissue cause hypertrophy, edema and pain this need not happen with proper adjustment if it is desired to maintain contact after the movement achieved , restore the exact periphery in contact with the tooth by adding self curing acrylic. In actually the active plate is limited only by the imagination of the operator . It may carry locks, tubes, arches, rotating springs, habit preventing appliances or other appurtenances ordinarily considered to be in the realms of fixed appliances.

Nords plate

Lower Schwarz Appliance

This is specific type of active plate used in early stages of the mixed dentition period, to produce orthodontic tooth movement in the mandible mainly uprighting the posterior dentition and increasing anterior arch length anteriorly

It is rare to use lower Schwarz appliance as sole appliance to produce tooth movement. It is used in patients who have arch length deficiency and/or posterior teeth that have an abnormal lingual inclination.

McNamara recommends the completion of or near completion of Schwarz activation prior to onset of RME , he found that greater expansion transversely possible if lower teeth were in proper position at the initiation of RME . It is cardinal rule of the orthodontics that the lower canine expansion is relatively unstable, so why is treatment with this appliance is advocated? Studies carried out by Brust have shown that that average increase of 2.3mm more in arch perimeter at the end of therapy in RME/Schwarz group. Schwarz appliance may be useful in patients with mild to moderate lower incisor crowding but will not satisfy the arch length requirements of a patient with severely crowded incisor region.

Parts This is made from wire and acrylic Simple ball end clasps are placed in the embrasures between the lower deciduous molars and lower first molars. Adams can be used for additional retention usually not required. Expansion screw is located in the midline and embedded almost in acrylic. Additional acrylic also can be placed on the occlusal surface of the posterior teeth in case in which a posterior bite block effect is desired.

Advantages It is easily manageable clinically. Usually delivered without adjustment. Appliance is worn full time first 3-5 month as an active plate ( one mm expansion each month can be expected i.e. mm every 4 turns) and then as passive one for additional period of time for retention. Additional arch length of 3-4mm(mcnamara) can be gained on routine basis . Simple and a straight forward technique. Disadvantages Not recommended in the treatment of gross tooth size/arch length discrepancy problem.

SAGGITAL DIRECTION Saggital appliance develop arches mainly in antero posterior direction, by moving teeth in groups or singly. Screws are placed parallel to the antero posterior plane or parallel to crest of the crest of the alveolar ridges. If second molar is missing the expansion can be 80% in posterior region and presence of second molar makes the expansion 80 % anteriorly. When such appliance is used for distalizing there is slight increase in arch width but this is extremely stable.

Appliance design

a) b) c)

The design is dependent on distortion present in the arch . Appliance has a basal plate sectioned into three component parts One braced against prevail and midpalatal area Two braced against posterior teeth and lingual gingival areas along posterior teeth on each side Clasp on posterior teeth for retention generally Adams on first molars and ball clasp in canine region.

The pull screw

“ Y “ Plate It is an active removable type of appliance that moves the teeth under certain conditions its appearance is similar to that of the bite plate and it is anchored on the maxillary arch with Adams or arrowhead clasps. The labial bow inserts into the acrylic in the lateral incisor –canine embrasure The plate has two jack screws exerts a distalizinz force

The opening of the jackscrews exerts a distalizing component on the buccal segment teeth and a reciprocal force is delivered to the anterior palatal contour and maxillary incisors. To reduce the mesial force component, which tend to tip the incisor labialy and dislodge the appliance, the screws are activated alternately and unilaterally. INDICATION: First premolars erupted, giving increased anchorage. Upright incisors and slight tipping not undesirable. No extensively bodily movement are required. The second premolar have not yet erupted.

PASSIVE EXPANSION When the forces of the buccal and labial musculature are shielded from the occlusion , a widening of the dental arches often occurs. This expansion is not produced through the application of extrinsic bio-mechanical but rather than by intrinsic forces in the dental arch such as those produced by the tongue.

In the growing child rigid removable appliance should be avoided, and attempt to use elastic bi maxillary appliance which stimulate the activity of oro facial musculature. Balters in this context states “ It is unnecessary to use active forces for arch expansion as interplay of muscle takes care of dental arch formation, it should be realized that the orthodontics should lead to jaw orthopaedics i.e.. reforming the jaw and the dental arches on a functional basis . �

Frankel has emphasized on the use of labial and buccal vestibule. Using lip pads and the buccal shield effectively hold the buccal and labial musculature away from the teeth and investing tissue eliminating any restrictive influence that this functional matrix might have. Another possible mechanism of arch expansion involves an aspect of the appliance that has been continually stressed by frankel. He has stated that the vestibular shields should be extended into the vestibular reflex so that the tension produced on the soft tissue and this pull on the soft tissue is transferred to the periosteunm and results in deposition of new bone on the facial aspect of the alveolus.

VESTIBULAR SCREEN AND LIP BUMPERS These can be used during deciduous and mixed dentition. Philosophy of these appliances are similar to the frankel appliance. The change in balance of the forces between the tongue and peri-oral musculature causes expansion of the jaws.

Bionator Originally developed by Balters in early 1950 . Buccinators loops eliminates the tension of the strong buccinator muscle thus there is marked arch expansion . Coffin spring is not active but stimulator for the tongue function

Activator and headgear Treating anterior protrusion with spacing and disto occlusion. A combination of extra oral force must be considered. It prevents vicious habits and reorient physiological forces. Act as space maintainer . Expand not actively but as the teeth move distally the expansion of the arch takes place because they move to wider part so to maintain contact the screw is added. Starts to correct deep bite.( within Freeway space limits) Helps correct class II relationship in three plane of space.

Design not very different from ordinary appliance. Four clasps on teeth usually required, if claspable teeth not present accessory arrowhead clasp to produce retention, and allowed to seat firmly to avoid levering and tipping effect.

Bimler appliance This appliance is dynamic functional elastic syste, activated by muscl energy in transverse and saggital development of the arches. It is only indicated in certain cases of narrow arch with anterior croeding, because the coffin spring is upper part is not suffiecent to correct the severe arch compression. but incorporating a screw makes it more rigid so that the relative forces of the mandible are not utilized which is why a coffin spring is used.

Bimler Appliance

Tongue activates the elastic bite former with coffin spring

Types of corrections using coffin spring in Bimler appliance Type A ( Class II/I )

Type C ( Class III )

Proffit has compared the effects of rapid maxillary expansion with slower one.

Outlook looks similar after two months

RELAPSE It is maintained that the crowding is attributed to the lack of arch width. Expansion of arches will produce the space for proper alignment of anterior teeth . Without extraction alignment tends to arrange anterior teeth into wider circle by means of proclination of these teeth. These placements of dental arches are not stable and from them more or less degree of relapse takes place in absence of new stabilizing factor.

The main role of expansion is the possibility of correcting discrepancies in bucco-lingual occlusion. Removable appliance should be regarded for producing expansion of the buccal segment. It is important to regard this movement as intended for correction buccolingually of the occlusal relationship.

Summary Chance of major relapse after expansion decreases if done slowly during mixed dentition that brings about the adjustment if the musculature and tongue space. Amount of retention is different for different cases, better to overestimate. Younger the age more stable the result. Treatment with removable appliances will not provide the best answer to every orthodontic problem. Ideal rate of expansion : - 1mm /week . Collapsing forces are prevalent for approximately 6 months . Over expansion . Maxillary arch more stable than the lower arch to maintain space achieved.

Some small degrees of irregularity are impossible to treat with removable appliances, and some severe malocclusions respond well. Nevertheless they are cheap to construct and hence treatment cost cut down appreciably. Decision to acquire space by expansion or other means should be based on the meticulous assessment of the diagnostic data and understanding of the underlying etiology and possible growth mechanism.

As for expansion it has tested the deep waters of time to be completely trusted and accepted as a respected treatment modality in the field of orthodontics.

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