part 5 appliance choices

BRITISH DENTAL JOURNAL VOLUME 196 NO. 1 JANUARY 10 2004 9

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Orthodontics. Part 5: Appliance choicesD. Roberts-Harry1 and J. Sandy2

There are bewildering array of different orthodontic appliances. However, they fall into fourmain categories of removable, fixed, functional and extra-oral devices. The appliance has tobe selected with care and used correctly as inappropriate use can make the malocclusionworse. Removable appliances are only capable of very simple movements whereas fixedappliances are sophisticated devices, which can precisely position the teeth. Functionalappliances are useful in difficult cases and are primarily used for Class II Division Imalocciusions. Extra-oral devices are used to re-enforce anchorage and can be an aid inboth opening and closing spaces.

1Orthodontic Department, Leeds DentalInstitute, Clarendon Way, Leeds LS2 9LU;2Division of Child Dental Health, Universityof Bristol Dental School, Lower MaudlinStreet, Bristol BS1 2LY

Refereed Paperdoi:10.1038/sj.bdj.4810872© British Dental Journal 2004; 196:9–18

● The correct appliance choice is essential for optimum treatment outcome● Removable appliances have an important but limited role in contemporary orthodontics● Fixed appliances are usually the appliance of choice● Functional appliances are helpful in difficult cases but may not have an effect on

facial growth● Extra-oral devices include headgear, face-masks and chin-caps

I N B R I E F

There are four main types of types of appliancethat can be used for orthodontic treatment.These are removable, fixed, functional and extraoral devices.

REMOVABLE APPLIANCES In general these are only capable of simple toothmovement, such as tipping teeth. Bodily move-ment is very difficult to achieve with any degreeof consistency and precise tooth detailing andmultiple tooth movements are rarely satisfactory.These appliances have received bad press overthe past few years because studies have shownthat the treatment outcomes achieved can oftenbe poor.1,2 In these studies as many as 50% ofcases treated with removable appliances wereeither not improved or worse than at the start oftreatment. When faced with evidence such asthis, one might be justified in discarding remov-able appliances completely. However, providedthey are used in properly selected cases they stillcan be very useful devices and the treatmentoutcome can be satisfactory.3 In general, remov-able appliances are only recommended for the following:

• Thumb deterrent• Tipping teeth• Block movements• Overbite reduction• Space maintenance• Retention

Thumb deterrentDigit sucking habits which persist into theteenage years can sometimes be hard to breakand may result in either a posterior buccal crossbite or an anterior open bite with proclination ofthe upper and retroclination of the lower inci-sors. In general, if the habit stops before facialgrowth is complete then the anterior open biteusually resolves spontaneously and the overjetreturns to normal.4

Figs. 1a–c show a case with an anterioropen bite associated with an avid digit suck-ing habit. A simple upper removable appliancewas used successfully to stop the habit. Theappliance simply makes the habit feel less of acomfort and acts as a reminder to the patientthat they should stop sucking the thumb.Complex appliances with bars or tongue cribsare rarely needed. In this patient once thehabit had stopped the open bite closed downon its own without the need for further ortho-dontic treatment.

TippingOne of the major uses of removable appliancesis to move one incisor over the bite as shown inFigs 2a–d. A simple upper removable applianceutilized a ‘T’ spring constructed from 0.5 mmwire activated 1–2 mm which delivered a forceof about 30 g to the tooth. After only a fewweeks the cross bite was corrected without theneed for complex treatment. Note the anterior

5

ORTHODONTICS1. Who needs

orthodontics?2. Patient assessment and

examination I3. Patient assessment and

examination II4. Treatment planning5. Appliance choices6. Risks in orthodontic

treatment7. Fact and fantasy in

orthodontics8. Extractions in

orthodontics9. Anchorage control and

distal movement10. Impacted teeth11. Orthodontic tooth

movement12. Combined orthodontic

treatment

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10 BRITISH DENTAL JOURNAL VOLUME 196 NO. 1 JANUARY 10 2004

retaining clasp that prevents the appliancefrom displacing downwards when the spring isactivated.

If teeth are to be pushed over the bite withremovable appliances, a stable result is morelikely to be achieved if the tooth is retroclined inthe first instance, the overbite is deep and there

is an anterior mandibular displacement associ-ated with a premature contact. Tipping teethtends to reduce the overbite because the tip ofthe tooth moves along the arc of a circle asshown in Figure 3a. Excessive tipping may alsomake the tooth too horizontal which can be notonly aesthetically unacceptable but may also

Fig. 1a–c A 9 year-old patient with an anterioropen bite caused by a thumb sucking habit. Notethe wear on the thumb as a result of this. Shewas fitted with a simple upper removableappliance and gently encouraged to stop thehabit. She did so successfully and the open biteclosed down spontaneously in 6 months

Fig. 2a an anterior cross bite involving the upperleft and lower left central incisors

Fig. 2c The appliance in place. The T spring isactivated 1–2 mm every 4 weeks

Fig. 2d The completed case. Active treatment took12 weeks

Fig. 2b An upper removable appliance with Adamscribs for retention made from 0.7 mm wire on thefirst permanent molars and the upper left centralincisor. A ‘T‘ spring made from 0.5 mm wire isused to push the tooth over the bite. The anteriorretention is to prevent the front of the appliancebeing displaced as the spring is activated

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result in excessive non-axial loading of thetooth as illustrated in Figure 3b.

Overbite reduction when teeth are over pro-clined is illustrated in Figures 4a–d. In this caseboth the upper lateral incisors were pushed overthe bite with an upper removable appliance. Thecross bite was corrected but note the reductionin overbite on the lateral incisors. Six monthsafter completion of treatment the upper rightlateral had relapsed back into cross bite.

Block movementsIf a cross bite involves a number of teeth, forexample a unilateral buccal cross bite, remov-able appliances can be used to correct this. The

sequence of events is shown in Figures 5a–f.Adams cribs are generally placed on the firstpremolars and the first permanent molars and amidline expansion screw is incorporated intothe base plate. This midline screw is opened0.25 mm (one quarter turn) twice a week untilthe cross bite is slightly overcorrected. Posteri-or buccal capping can also be used to disen-gage the bite and prevent concomitant expan-sion of the lower arch. Once the cross bite iscorrected the buccal capping can be removedand the appliance used as a retainer to allowthe buccal occlusion to settle in. Occasionallytwo appliances will be needed if a considerableamount of expansion is needed.

Fig. 3a The effect of tipping anteriorteeth on the overbite. As the teethmove around a centre of rotation theincisal tip moves along the arc of acircle. By the laws of geometry, asthe tooth is proclined the overbitereduces once it moves past thevertical

Fig. 3b Excessive tipping not onlyreduces the overbite but also makesthe axial inclination of the teeth too horizontal. In thesesituations stability is reduced, theappearance is poor and the tooth maysuffer from unwanted non-axial loading ➠

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Fig. 4a Both the upper lateral incisors are in crossbite

Fig. 4c The cross bites have been corrected. Notethe reduction in the overbite

Fig. 4d 6 months later the upper right lateral hasrelapsed into cross bite due to the reducedoverbite

Fig. 4b An upper removable appliance was used totip the laterals over the bite

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Fig. 5a Narrowness of the upper arch can produce a traumatic bite

Fig. 5c An upper removable appliance with a mid line expansionscrew can be used to correct the cross bite. The screw is opened one-quarter turn twice a week by the patient

Fig. 5d The corrected cross bite. The treatment time varies with theamount of expansion needed but usually takes about twelve weeks

Fig. 5b To avoid painful cuspal contact the patient may move themandible to one side producing a mandibular deviation and a crossbite

Fig. 5e Once active treatment is completed the appliance can beworn as a retainer. The posterior capping can be reduced to allowinterdigitation of the buccal teeth thus helping to prevent anyrelapse

Fig. 5f The completed case

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Overbite reductionRemovable appliances are very effective in cor-recting a deep overbite, especially in a growingpatient. An upper removable appliance with ananterior bite plane is used which disengages themolars by 2–3 mm whilst at the same timeestablishing lower incisor contact with the biteplane (Fig. 6). Eruption of the posterior teethproduces a reduction in the overbite. It is essen-tial that the inter-incisor angle is corrected atthe completion of treatment so that an occlusalstop between the upper and lower incisors isproduced preventing re-eruption of the incisorsand a relapse of the overbite. Bite planes areusually used in conjunction with fixed appli-ances to help the overbite reduction (Figures7a–d) or can be used as an aid to restoration of the anterior teeth. Figures 8a–d show a patient with a deep bite who had marked enamelerosion. Porcelain crowns were to be placed onthe anterior teeth to restore them, but the deepbite made this technically difficult. The overbite

was therefore reduced with a bite plane to makeroom for the crowns.

Space maintenance Space maintainers are rarely indicated in ortho-dontic treatment but occasionally can be used,particularly if the upper canine is buccally crowd-ed. Whilst the extraction of the first premolarswill often create space for the canines, there is a danger that the space will close before thecanine erupts as the buccal teeth drift mesially.Figures 9a–e illustrate such a case where the fit-

ting of a space maintainer proved useful. Theappliance was fitted just prior to the emergenceof the permanent canines. The four first premo-lars were then extracted and the appliance left inposition until the canines erupted. This tookabout 6 months and saved a considerableamount of extra treatment for the patient byallowing spontaneous alignment of the canines.

RetentionMany orthodontists use various types of remov-able appliances to act as retainers, usually at the

2-3mm

Fig. 6 Overbite correction with a removable appliance. The posterior teethshould be separated by about 2–3 mm

Fig. 7a A case with a deep bite and retroclinedupper incisors

Fig. 7c Once the overbite is fully reduced theupper fixed appliance can be placed

Fig. 7d The completed case with good overbitereduction

Fig. 7b An upper removable appliance is used tohelp the overbite reduction whilst palatal springssimultaneously move the first permanent molars distally

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Fig. 8a, b A patient with severe erosion of theteeth

Fig. 8c A bite plane was used to reduce theoverbite

Fig. 8d Strip crowns were placed on the incisorsonce the overbite was reduced

Fig. 9a, b A case with severe upper arch crowding. The upperpermanent canines were unerupted, buccally positioned andvery short of space

Fig. 9c An upper removable space maintainer. Adam cribs havebeen placed on the first permanent molars and a Southend claspon the upper central incisors

Fig. 9d,e The first premolars have been extracted and the upper caninesare erupting into a good position

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completion of fixed appliance treatment.Removable retainers are usually held in positionwith Adams Cribs on the first permanent molarswith a labial bow and possible acrylic coverageof the anterior teeth (Fig. 10).

FIXED APPLIANCESThese appliances are attached to the crowns ofteeth and allow correction of rotations, bodilymovements of teeth and alignment of ectopicteeth. They have increased in sophisticationenormously over the past 10–15 years andtogether with advancements in arch wire tech-nology are capable of producing a very highlevel of treatment result. Simultaneous multiple

tooth movements can be achieved, invariablycreating a better treatment outcome than can beachieved with removable appliances. Althoughthere are a variety of fixed appliances availablethey all operate in a similar way producing afixed point of attachment to control the positionof the teeth. Brackets are attached to the teethand wires (arch wires) are placed in the bracketslots to move the teeth. The closer the fit of rec-tangular arch wires in a rectangular slot on thebracket the greater the control of the teeth(Fig 11). As treatment progresses, thicker rectan-gular wires are used to fully control the teeth inthree dimensions. Fixed appliances are theappliances of choice for most orthodontic treat-

ment because the results are far more predictableand of a higher standard achieved than by othermeans. However, they are relatively complexappliances to use and further training in thesedevices is essential. An example of a case treatedwith fixed appliances is shown in Figure 12a–j.The anchorage requirements for the bodilymovement of teeth are considerably greater thanfor tipping movements (Fig. 13).

FUNCTIONAL APPLIANCESThese are powerful appliances capable of impres-sive changes in the position of the teeth. Theyare generally used for Class II Division I maloc-clusions although they can be used for the

Fig. 10 One exampleof the manydifferent types ofremovable retainers

Fig. 11 Rectangular arch wire in rectangular bracketslots allows three-dimensional control of the teeth. The tighter the fit of the wire in the slotthe greater the control of the teeth

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Fig. 12a, b Pre treatment photographs of a patient with palatallyimpacted canine, a buccal cross bite, an increased overjet andcrowding in both arches

Fig. 12c Upper first and lower secondpremolars were extracted and the caninessurgically exposed

Fig. 12d A tri-helix was used to expand the upperarch and a sectional fixed appliance used to pullthe canine into the line of the arch

Fig. 12e Full fixed appliances were then used to reduce the over biteand overjet, move the apex of the canine into the line of the arch andcorrect all the other features of the malocclusion. The initial archwire was a very thin flexible wire. If a thick wire is used at this stageexcess force will be applied to the teeth that can produce rootdamage and be very painful for the patient

Figs 12f,g Once initial alignment of the teeth is producedprogressively thicker, stiffer wires are employed. Because these fitthe bracket slot more closely they control tooth position moreprecisely than the thinner aligning wires

Fig. 12h,i Thecompleted case.The canine is fullyaligned and theoverjet reducedwithout anyunwanted tippingof the teeth

Fig. 12j Appropriate extractionsand treatment mechanics havenot been detrimental to the facialappearance

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correction of Class II Division II and Class IIImalocclusions on occasion. They are eitherremovable from the mouth or fixed to the teeth,and work by stimulating the muscles of mastica-tion and soft tissues of the face. This produces adistalising force on the upper dentition and ananterior force on the lower. Whilst they are capa-ble of substantial tooth movement, like allremovable appliances they are not capable ofprecise tooth positioning and cannot deal effec-tively with rotations or bodily tooth movement.

There is some controversy as to the precisemode of action of functional appliances. Someclinicians feel they have an effect on this facialskeleton, promoting growth of the mandibleand/or maxilla. Others feel that the effects aremainly dento-alveolar and that the resultsachieved are accomplished by tipping the upperand lower teeth. Unfortunately many of the stud-ies relating to functional appliance treatmenthave been poorly constructed and their conclu-sions should be treated with caution. A large-scale, prospective, randomized clinical trialcurrently being undertaken in United Kingdomstrongly suggests that 98% of the occlusal

Fig. 13 Bodily movement of the teeth requires a greater degree offorce than tipping movements

Fig. 14c A functionalappliance was used tocorrect the saggitalrelationship

Fig. 14d The final resultafter detailing of theocclusion with fixedappliances

Fig. 14e,f Thefacial appearancefollowingtreatment

Fig. 14a,b Pre-treatmentphotographs of a 12-year-old girl with an increasedoverjet and a class II skeletalpattern associated with aretrognathic mandible

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correction is by tipping of the teeth with analmost negligible effect on the skeletal pattern.5

Nevertheless, dramatic occlusal changes are pos-sible with these appliances and they can aid thecorrection of some quite severe malocclusions.Figures14a–f show a case treated with a function-al appliance that had a marked effect not only on the occlusion but also on the patient's facialappearance.

EXTRA-ORAL DEVICESThese are headgear devices, chin caps and facemasks, which are used to provide an externalsource of anchorage or traction for teeth in one orboth arches. The commonest type is headgear forthe distal movement of the buccal teeth. A metalface bow is attached to either a removable or afixed appliance inside the mouth and elastic trac-tion applied to it. As well as force being applieddistally to either the maxilla or the mandible itcan be applied mesially via a facemask. This istypically used in Class III cases to correct an ante-

rior cross bite or in cases where the buccal seg-ments are being moved forward to close spaces inthe arches. Examples of extra oral tractiondevices are shown in Figures 15, 16a and b. Chincaps have been used to try and restrain mandibu-lar growth in Class III malocclusions. However,the evidence from the literature suggests that theyare not terribly effective and their use hasdeclined in recent years.

1. Richmond S, Shaw W C, O'Brien K D et al. The development ofthe PAR index (Peer Assessment Rating): reliability and validity.Eur J Orthod 1992; 14: 125-139.

2. Richmond S, Shaw W C, Roberts C T, Andrews M. The PAR index(Peer Assessment rating): methods to determine the outcomeof orthodontic treatment in terms of improvements andstandards. Eur J Orthod 1992; 14: 180-187.

3. Kerr W J S, Buchanan I B, McColl J H. The use of the PAR index inassessing the effectiveness of removable orthodonticappliances. Br J Orthod 1993; 20: 351-357.

4. Leighton B C. The early signs of malocclusion. Trans EuropOrthod Soc 1969; 353-368.

5. O'Brien K, Wright J, Conboy F et al. Effectiveness of treatmentfor Class II malocclusion with the Herbst or twin-blockappliances: a randomized, controlled trial. Am J OrthodDentofacial Orthop 2003; 124: 128-137.

Fig. 16a,b A facemask or reverse headgearFig. 15 Extra-oral tractionapplied via an Interlandiiheadgear

A letter to the BDJ highlighting the concerns of one of its members.

Sir, - There is a movement on foot to establish a “Section” of Dental Surgery in theBritish Medical Association, of which membership is only possible to those members ofthe British Dental Association who are on the Medical register.

I beg you most emphatically to protest against any new section, or society of dentalsurgeons being formed to which every member of the British Dental Association is noteligible. I am strongly in favour of every dentist being a surgeon as well (if possible), butI protest against a revival of the “Association of Surgeons practising Dental Surgery” inthis insidious form.

Yours trulyS. J. Hutchinson, M. R. C. S., LDS.Eng

BR Dent J, 1903; 24: 828

One Hundred Years Ago

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usha

Rectangle

part 5 appliance choices

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