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Retentionwiththermoplasticretainers:whatyouneedtoknowDrSimonJLittlewood

Consultant&SpecialistOrthodontist,UKAmericanAssociationofOrthodonticsAnnualCongress,Washington2018

HistoryThermoplasticretainerswerefirstdevelopedinthe1950’sandfamouslydescribedas“InvisibleRetainers”byPonitzin1971.1Theyfelloutoffavourduetoreliabilityissueswiththeirmechanicalproperties,butthischangedin1990’swiththeintroductionofthe“Essix”materials,usingplasticsbettersuitedtothepropertiesrequiredofretainers.2Thislecturewilldescribeacontemporary,evidence-basedapproachtouseofthermoplasticretainers.

DesignTheusual,preferred,contemporarydesignisfullcoverageoftheocclusion,evencoveringteeththathavenotbeenalignedduringthetreatment,topreventunwanteddifferentialeruptionofteeth.Ifteetheruptaftercompletionoforthodontictreatmentthennewthermoplasticretainersshouldbemadetoensureallteetharecovered.Theborderoftheretainershouldbejustbeyondthegingivalmargin,ensuringthatplasticflowsintotheareabetweenthecontactpointandpapillatoretainitinposition.Typeofmaterial&thicknessThereareessentially3typesofplasticusedasclearplasticretainers:3

• Polyethylene• Polypropylene• Polyurethane

DrLittlewoodwilldiscusstheevidencesupportingtheuseofthesedifferentplasticsindifferentsituations,4includingtheadvantagesanddisadvantagesofeach.Thereissomeevidencetosuggestthatretainersmadefrom1mmblanks(ratherthan0.75mm)willcrackless.5Evidenceforuse–justbulletpointareasthatwillbecoveredThecurrentbestevidenceinthefollowingareaswillbediscussed:6

• Howoftenthermoplasticretainersshouldbeworn?• Howtoimprovesettlingwiththermoplasticretainers• HowthermoplasticretainerscomparewithHawleyandbondedretainers

ResponsibilityandretentionWearingremovableretainersrequiresgoodcompliance.DrLittlewoodwilldiscusshowpatientsneedtobeeducatedtotakeresponsibilityfortheirremovableretainers,7,8aswelldescribingaUKnationalcampaigntoimproveretainerwearcalled“Holdthatsmile”.9

SimonJLittlewood,April2018

www.littlewoodortho.com

References1. Ponitz RJ. Invisible retainers. American Journal of Orthodontics 1971; 59: 266-272. 2. Sheridan JJ, LeDoux W, McMinn R (1993). Essix retainers: fabrication and supervision for permanent retention. J Clin

Orthod 1993; 27: 37-45. 3. LittlewoodSJ(2019–inpress).Chapter7:Clearplasticappliancesasretainers.InEliadesTandAthanasiouAE

(eds),OrthodonticAlignerTreatment:AReviewofMaterials,ClinicalManagementandEvidenceRetentionandrelapseinclinicalpractice.Stuttgart,Germany,ThiemePublishers,2019.

4. RajaTA,LittlewoodSJ,MunyombweM,andBubbNL.Wearresistanceoffourtypesofvacuum-formedretainermaterials:Alaboratorystudy.TheAngleOrthodontist2014;84:656-664.

5. ZhuY,LinJ,LongH,YeN,HuangR,YangX,etal(2017).Comparisonofsurvivaltimeandcomfortbetween2clearoverlayretainerswithdifferentthicknesses:Apilotrandomizedcontrolledtrial.AmJOrthodDentofacOrthop2017;151:433-439.

6. LittlewoodSJ,MillettDT,DoubledayB,BearnDR,WorthingtonHV(2016).Retentionproceduresforstabilisingtoothpositionaftertreatmentwithorthodonticbraces.CochraneDatabaseofSystematicReviews2016,Issue1.Art.No.:CD002283.DOI:10.1002/14651858.CD002283.pub4.

7. LittlewoodSJ.Responsibilitiesandretention.APOSTrendsOrthod2017;7:211-4.8. LittlewoodSJ(2019–inpress).Chapter16:Retention.InLittlewoodSJ&MitchellL(eds),AnIntroductionto

Orthodontics.OxfordUniversityPress,Oxford,UK2019.9. BritishOrthodonticSociety.Orthodonticretentionforpatients.Availableathttps://www.bos.org.uk/Public-

Patients/Orthodontic-Retention-for-Patients(accessedApril2018)