Outlinethesignificanceofthepre-adjustedEdgewiseappliance

systemandusefulbracketvariationsinorthodontics

DrMJRowland-WarmannBScBDS(Manc)MScAes.Med.(Lond)MJDFRCS(Eng)

GDC:178642

WordCount(excludingreferences):1680

Module4:FundamentalsofOrthodonticTreatmentofSkeletalProblemsinPreadolescence

andAdolescence

SubmissionDecember2017

StudentIDBP0150715

Contents

Page

Introduction 3

Modernbracketprescriptionsandtheirevolution 3

Andrews 4

Roth 4

MBT 4

Bracketvariationsfordifferentscenarios 6

Palatallyplacedlateralincisors 7

Absentlateralincisors 8

Class3canineangulation 8

Labialmovementofpalatalcanine 9

Caninegingivalrecession 9

Absentuppercentralincisor 9

Incisorsinclass3 10

Upperpremolarsubstitutingcanine 10

Casefinishing 10

Doestheprescriptionmatter? 11

Conclusion 13

References 14

Outlinethesignificanceofthepre-adjustedEdgewiseappliancesystemand

usefulbracketvariations(suchaschangingbracketposition,orientationor

locationinthearch)

________________________________________________

Introduction

Andrewsintroducedthepre-adjustededgewiseapplianceinthe1970sandrevolutionised

orthodontics(Andrews,1979).Thisreplacedtheedgewiseappliancewhereallbrackets

wereidenticalandtherewasgreatneedforwirebending(Johnson,2013).Andrews

introducedtipthroughslotangulationandtorquethroughslotinclination,alongwith“in-

out”throughbracketbasevariation(Thickett,Taylor,&Hodge,2007).

Modernbracketprescriptionsandtheirevolution

Theinceptionofthepre-adjustededgewiseappliancewashailedassignificant,reducing

wirebending,allowingforthemovementofgroupsofteethandthusshortertreatment

times,yetmoreconsistenttreatmentoutcomes(Thickettetal.,2007).Thisincreasedfocus

onprecisebracketplacement,andstraightwiresplacedmorestrainonanchorage(Singh,

2017).

Therehavebeenmanymodificationsintipandtorqueinpre-adjustededgewisesince

Andrews(Mittal,Thiruvenkatachari,Sandler,&Benson,2015).MBTandRotharethemost

commonlyusedtoday.

Andrews

Theoriginalstraightwireapplianceusedsiamesebracketsplacedonthefacialaxisofthe

clinicalcrownwithheavyforcestocontroltoothmovementinthreedimensions

(McLaughlin,Bennett,&Trevisi,2002;Mohammadi&Moslemzadeh,2011).

Prescriptionvaluestookaveragevaluesfrom120models(Andrews,1972,1979).Andrews’

prescriptionhaddifferentsetsforvariousmalocclusions,degreeofcrowdingand

extraction/non-extractioncases(Singh,2017),incorporatinganti-rotationandanti-tipinto

extractioncases(Andrews,1979).Thisresultedinalargenumberofbrackettypes.

Roth

Tominimiseheplethoraofbrackettypesandnecessaryinventory,Rothdevisedonesetof

bracketsapplicableformostcases,combiningAndrews’setCupperincisor,setSlower

incisors,minimumtranslationupperposteriorandlowercaninebrackets,andmaximum

translationuppercanineandlowerposterior(Thickettetal.,2007).Healsoincreasedtipto

assistcanineguidance,anddistalcrowntiptolowerbuccalsegmentsashisprescriptionwas

moreanchoragedemanding.Furthermore,uppermolartorqueincreasedtopreventpalatal

cuspdrop(McLaughlinetal.,2002;Singh,2017;Thickettetal.,2007).

MBT

DevisedbyMcLaughlin,BennettandTrevisiinthe1990s,thisprescriptionisbasedarounda

numberofprinciples.Bracketversatility,lightcontinuousforces,anchoragecontrol,group

movementofteethandasinglefinishingwirearekeyelementsoftheMBTtheory.

Accuratebracketplacementissignificant,andbracketplacementchartsweredevised

(Figure1)(McLaughlinetal.,2002).

Figure1:MBTbracketplacementcharts;from(McLaughlinetal.,2002)

MBTreducedanteriortipcomparedwithRothandAndrews.Itsaimwastoreducestrainon

molaranchorageandavoidin-treatmentarchlengthincrease(Thickettetal.,2007);

undertorquingteethrequiresspace,soforevery5°ofanteriorinclination,1mmofarch

lengthisgenerated,resultinginlackofstability(Badawi,Toogood,Carey,Heo,&Major,

2008;Fleming,DiBiase,Sarri,&Lee,2009).Increasedpalatalroottorquecounteracts

torquelossduringoverjetreductionandspaceclosureandlabialroottorqueincreasedto

limitlowerincisorproclineonlevelling.Furthermore,caninetipwasreducedtoupright

rootsandpreventcanineandpremolarrootproximity(Moesi,Dyer,&Benson,2013;

Thickettetal.,2007).

ThetipandtorquevaluesofAndrews,RothandMBTareillustratedinFigures2and3.

Figure2:Andrews/Roth/MBTtorquevalues;from(Thickettetal.,2007)

Figure3:Andrews/Roth/MBTtipvalues;from("Erratum,"2014)

Bracketvariationsfordifferentscenarios

Astheprescriptiononanindividualbracketisknown,variationscanbeemployedwhen

thereisalocaltoothpositioningproblemormissingtoothbychangingtheorientationor

usingabracketonatoothotherthantheoneforwhichitwasintended(Singh,2017;

Thickettetal.,2007).Inversionresultsinatorquechangebutnottip.Swappingtheright

andleftbracketschangesthetipvaluewithoutchangingtorque(Thickettetal.,2007).

Palatallyplacedlateralincisors

Thelateralincisorbracketwillnotsupplyenoughlabialroottorque.Inversionofthelateral

incisorbracketreversesslotinclination,graduallyintroducingtorquewiththewire

sequence,improvingcomfortovertheuseoftorqueingpliers(Singh,2017;Thickettetal.,

2007)

Appliedinpractice,ananAndrewsbrackethasa6°difference,Roth16°andMBT20°

(Figure4-6).

Figure4&5:Managementofpalatallyplacedlateralincisors;from(McLaughlinetal.,2002)

Figure6:clinicalpresentationofbracketforpalatallateralincisors;from(McLaughlinetal.,

2002)

Absentlateralincisors

Thecaninebracketisunsuitablewhenreplacingalateral,asitgivesgraterlabialroottorque

whenpalatalroottorqueisrequiredforlateralincisors–thecrownanatomiesofthetwo

teetharevastlydifferent.Alateralbracketwouldpositionthetoothpalatallyandthefitis

poor;afurtheroptionwouldbetorecontourthecanine,thenplacethebracket,although

thismayresultinpoortoothangulation.Asimplemeasureisinversionofthecanine

bracket,maintainingthebracketfitandin-out(Figure7).MBTandAndrewsgivespalatal

roottorquechangesby14degrees;tipvaluesforlateralsandcaninesinMBTareidentical,

withRoththereisasmalldifference(McLaughlinetal.,2002;Thickettetal.,2007).

Figure7:Positioningcaninebracketforabsentlateralincisor;from(McLaughlinetal.,2002)

Class3canineangulation

Whencamouflaging,theunderlyingmalocclusionisacceptedandincisorsarecompensated.

Toanglelowercaninesfavourably,thecontralateralcaninebracketscanbeswitchedto

encouragedistaltipandreduceanchoragerequirements(Figure8)(Singh,2017;Thickettet

al.,2007).Someclinicianspreferusingthecorrectbracket,angulatingitforcrowntipto

leavethepowerarmavailablebutthismaycauseapoorfittothetooth(Arun&Kallur,

2008).

Figure8:contralateralcaninebracketforclass3;from(Thickettetal.,2007)

Labialmovementofpalatalcanine

Palatalcaninemovementresultsincrownmovementwithouttheroot,causingunattractive

tip.Inordertoincreaselabialroottorque,thelowercontra-lateralcaninebracketcanbe

invertedtotheupper.ThisisrelevantinRothwherethereis9°change;inMBTthereare

similartorquevalues(Thickettetal.,2007).

Caninegingivalrecession

Incaseswherethegingivaehasrecededorthecanineisveryprominent,invertingthe

bracketgivespalatalroottorque,whichcanhelpreducefurtherrecession(McLaughlinet

al.,2002).

Absentuppercentralincisor

Inordertofacilitaterestorativetreatment,thepreferentialmesialrootmovementoverthe

crownshouldoccur.Bondingthecontralateralcentralincisorbrackettotiltthetooth

allowsthis(Figure9)(Thickettetal.,2007);however,somecliniciansprefercentringthe

lateralincisorinthespaceforrestorativepurposesclaimingthisimprovesforce

transmissionthroughtheroot(Arun&Kallur,2008)

Figure9:managementofmissingcentralincisor;from(Thickettetal.,2007)

Incisorsinclass3

Inclass3cases,thereisaneedforupperincisorproclination.Itispossibletoinvertincisor

bracketsforlabialroottorque,MBTgivingthegreatestchangeat34°(Thickettetal.,2007)

althoughthereareconcernsthatthisamountoftorquerisksrootresorption(Arun&Kallur,

2008).

Upperpremolarsubstitutingcanine

Incaseswherethecanineisabsentorreplacingthelateralincisor,placementofthebracket

moredistallyonthepremolarmovesthepalatalcuspoutoftheway(Singh,2017).

Smoothingthepalatalcuspofthefirstpremolarmayberequiredtofurtherhideitor

improveocclusalinterference.

Casefinishing

InordertoachievegoodfinishingandocclusioninMBTprescription,lowersecondmolar

tubescanbeusedonthecontralateralupperfirstandsecondmolarstoresultinzerotip

andzerorotation,resultinginmesio-palatalrotationofuppermolars,asshowninfigure10

(McLaughlinetal.,2002).

Figure10:casefinishingmolars,from(McLaughlinetal.,2002)

Doestheprescriptionmatter?

MoesietalandMittaletaldemonstratedthattherewasnodifferenceinsubjective

aestheticjudgementoranteriortoothangulationbetweenMBTandRothbracket

prescriptions,andsmallchangesintheprescriptiondonotmakeclinicallydetectableresults

(Kattner&Schneider,1993;Mittaletal.,2015;Moesietal.,2013).

Theconceptoftorsional(slot)playmustbeaddressed.Theengagementanglebetweenthe

bracketandwireisvariable,sosmallchangesinbracketsmaynotfullyexpressasthe

workingwireonlyengagesthebracketatfewpointsandfullprescriptionexpressionmay

neveroccur(Figure11)(Archambaultetal.,2010).

Figure11:theconceptoftorsionalplay;from(Johnson,2013)

Prescriptionexpressionisdependentontheworkingarchwireandthevariationin

engagement.Figure12showsincreasingthethicknessofarchwiresindifferentbracket

slotsdecreasestorsionalplay;achangeinarchwireisasimilardifferencetotheprescription

differenceindegreesbetweenRothandMBT(Archambaultetal.,2010;Badawietal.,2008;

Moesietal.,2013).Usingawiresequencethatgraduallyexpressestheprescriptionand

finishingcasesinthethickestwirepossibleisthereforeessential(Badawietal.,2008;Moesi

etal.,2013).Errorsinprescriptioncanalsostemfromimpropermachining(Cash,Good,

Curtis,&McDonald,2004).Inanattempttoexpressmoreofthedesiredvalues,high

torqueprescriptionshavebeenadvocated(Gioka&Eliades,2004).

Figure12:changeinwiresizeversusslop;from(Johnson,2013)

Conclusion

Cliniciansmustunderstandprescriptionstoachieveidealtoothposition.Evenwithpre-

adjustedappliances,achievingallsixkeysofocclusionisstilldifficult(Davies,Gray,Sandler,

&O'Brien,2001;Kattner&Schneider,1993).Thereisaneedforabracketinventoryto

includeavarietyofprescriptionsandtheknowledgetoapplythemindifferentscenariosfor

individualpatientneeds.Whilstthepre-adjustedapplianceiseconomicalandefficient,and

hasnodoubtrevolutionisedorthodontictreatment,itreliesheavilyonaccuracyofbracket

placement,andnosingleprescriptiontotallyeliminateswirebending.Theoutcomeof

orthodontictreatment,however,doesnotrelyontheprescriptionalone(Kattner&

Schneider,1993;Lotzof,Fine,&Cisneros,1996;Thickettetal.,2007).

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