age healthy people: Influence of sex and 3D analysis of smiling function in ARTICLE IN PRESS

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JournalofPlastic,Reconstructive&AestheticSurgery(2019)000,1–4

Correspondence and Communications

3D analysis of smiling function in healthy people: Influence of sex and age

DearSir,

Smilinghasaspecialimportancefromaesthetic,psycho- logicalandsocialpointsofview.Smilingmaybealteredor deletedbyseveralpathologicalconditions,includingsurgi- calprocedures.Partialorfullrestorationofmimicryisthe taskofreconstructivesurgery,usuallythroughfacialreani- mationprocedures¹.Three-dimensional(3D)imageacquisi- tionsystemscanquantifytheresidualfunctioninpatients affectedbyfacialpalsy¹,andthedegreeofmimicryrestora- tionafterfacialreanimationsurgery,butnormalstandards fromhealthysubjectsareneeded^1,2.Ascurrentliteratureis dividedabouttheeffectofsexandageonfacialmovements inhealthyadults^2–5,theaimofthepresentstudywastode- fineasetofreferencevaluesforsmilingfunctioninhealthy malesandfemalesinawideagerange.

3D surface analysis of smiling movements was applied to30malesand30femalesagedbetween40and82years (meanage54.4years,SD10.5years),equallydividedamong threeagegroups(40–49years;50–59years;≥60years).Ex- clusioncriteriawerefacialscarsanddeformities,facialsur- gicaltreatments,traumasandlocalorsystemicneuromus- cular pathologies affecting facial mimicry. The study was performedaccordingtotheDeclarationofHelsinkiandwas approved by the local ethic committee (Università degli StudidiMilano,92/2014).Allthevolunteersreadandsigned an informed consent.Foreach subject, two3Dfacial im- ages wereobtained at few seconds of distance througha stereophotogrammetricsystem(VECTRA® M3:CanfieldSci- entificInc.,Fairfield,NJ):oneinrestposition(neutralex- pression)andoneinsmilingposition(corner-of-the-mouth, or Mona Lisa smile)¹. The subjects were shown the re- questedfacialexpressionandpracticedbeforeacquisitions.

A facialareaof interestwasdefinedbetween trichion, frontotemporale,zygion,tragion,gonionandgnathionland- marksinbothneutralandsmiling3D facialdigitalimages.

Thefacialareaincludedwithintheselectedperimeterwas automaticallysegmented(VectraAnalysisModule,Canfield Scientific Inc.,Fairfield,NJ),anddividedintofacialthirds definedaccordingtothetrigeminalterritoriesdistribution¹. Foreach subject,the3D digitalimage ofthesmiling face was then automatically registered on the neutral one to reach the least point-to-point distance between the two

Figure1 Superimpositionbetweenthetwofacialsurfacesin neutral position and insmiling expression andillustration of point-to-pointdistancesthroughachromaticanalysis(ingreen, areasthatdonotmove;inred–posteriordirection-andblue –anteriordirection-areas ofmovement). The subjectis a40 yearsoldman.

surfaces. The point-to-point root mean square (RMS) dis- tancebetweenthetwosurfaceswascalculatedseparately foreachfacialthird:thelargerthefacialmovementsdur- ingsmiling,thelargertheRMSvalue.Theamountofmove- ment during smiling was visualized using chromatic maps (Figure1).In addition,mouthwidth(cheilion–cheiliondis- tance)inrestpositionwascalculated.

RMSvaluesdidnotdiffersignificantlybetweentheright and the left side of the face, independently from sex or age group (Student’s t, p>0.05; Table 1). A two-way AN- COVAfound nosignificant differences according tosex or age,independentlyfromthesideandfacialthird(covariate cheilion–cheiliondistance,p>0.05).

In healthyadult subjects, point-to-pointRMS distances between the rest and the smiling facial images do not change significantly according to side, sexor age (among the5thandthe8thdecadesoflife).

Literatureaboutsexualdimorphisminsmilingisdivided:

from a morphological point of view, facial expressions in

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Table1 RMSvaluesdividedaccordingtosex,age,sideandfacialthirds,andwidthofthemouth(ch–ch)distance.

Males(n=30) Females(n=30)

40–49years 50–59years ≥60years 40–49years 50–59years ≥60years

R L R L R L R L R L R L

Upperthird Mean 0.53 0.48 0.61 0.63 0.70 0.72 0.60 0.58 0.59 0.57 0.61 0.67

SD 0.29 0.27 0.35 0.34 0.32 0.31 0.29 0.29 0.27 0.22 0.24 0.20

Middlethird Mean 1.67 1.62 1.75 1.81 1.63 1.81 1.46 1.44 1.34 1.36 1.57 1.60

SD 0.85 0.89 0.55 0.59 0.83 0.91 0.57 0.60 0.50 0.60 0.78 0.79

Lowerthird Mean 1.22 1.19 1.39 1.42 1.30 1.36 1.07 1.01 0.95 1.04 1.23 1.29

SD 0.58 0.53 0.42 0.33 0.58 0.62 0.42 0.42 0.35 0.44 0.58 0.62

ch–ch Mean 55.2 54.5 54.7 48.3 50.6 48.8

SD 2.7 4.8 4.6 4.4 3.2 3.0

Allthevaluesareexpressedinmm.R:right;L:left.

malesaremoreextensivethaninfemalesbecausethefacial skeletonandsofttissuesaremoreexpanded²,withthicker and larger facialmuscles, containing proportionally more fibres³.DifferencesinRMSvaluesaccordingtosexwerere- portedforasurpriseexpression,forcheeksinflatingandin thepronunciationofthe/u/sound,whilethesmileanima- tionhad similardisplacementsin both sexes^3,4.In studies basedontheassessmentof3Dlandmarkdisplacement,the sexualdimorphismdisappearedaftercorrectingforthedif- ferentfacialdimensions inthetwosexes².Accordingly,in the current study we usedcovariate analysistolimit this possiblebias.

Influenceofagingonfacialmimicryisalsodebated:fa- cialmovementswerereportedtobewiderafter50yearsof age⁴ andin 60–70yearsoldsubjects⁵,possiblyasaconse- quence oftheincreasein facialsurfaceareainagedpeo- ple⁴. Aprevious study analyzedlandmark displacement in healthysubjectsanddidnotobservedifferencesaccording toage,butpersonsagedover50yearswerenotincluded². Thepresentinvestigationincludedvolunteersaged60years or more, but no significant differences according to age werefoundinbothsexes,althoughRMSvaluesweresome- howhigher insubjects aged60 yearsor more thanunder 60years.Thedifferentexperimentalprotocolmayexplain thesediscordances:inthepresentcase,calculationofRMS point-to-pointdistances between tworegistered surfaces, geometricmorphometryanalysisforVeleminskà etal.⁴.

Inconclusion,thepresent studyprovidescontrolrefer- encevaluesfor3Dsurfacemodificationsduringsmiling.The movementsdonotdependupon sexorage,thus simplify- ingthedefinitionofreferencevalues.Datacanbeusedto evaluate the residualmimicfunction of patients affected by facialpalsyandto calculatethe amount of movement restoredbysurgicalintervention.

Conflict of interest statement

None.

Role of funding sources

Nospecificfundingwasobtained.

References

1.CodariM,PucciarelliV,StangoniF,ZagoM,TarabbiaF,BiglioliF, SforzaC.Facialthirds-basedevaluationoffacialasymmetryus- ingstereophotogrammetricdevices:applicationtofacialpalsy subjects.JCranio-MaxillofacSurg2017;45:76–81.

2.SforzaC,Mapelli A,GalanteS,MoriconiT,IbbaM,Ferraro L, FerrarioVF.Theeffectofageandsexonfacialmimicry:athree- -dimensionalstudyinhealthyadults.IntJOralMaxillofacSurg 2010;39:990–9.

3.Jandovà M,Urbanovà P.Sexualdimorphisminhumanfacialex- pressionsby3Dsurfaceprocessing.Homo2018;69:98–109. 4.Veleminskà J,Dankovà S,Brizovà M,Cervenkovà L,KrajicekV.

Variabilityoffacialmovementsinrelationtosexualdimorphism and age: three-dimensional geometric morphometric study.

Homo2018;69:110–17.

5.Giovanoli P, Tzou CH, Ploner M, Frey M. Three-dimensional video-analysisoffacialmovementsinhealthyvolunteers.BrJ PlastSurg2003;56:644–52.

DanieleGibelli¹ LaboratoriodiAnatomiaFunzionaledell’Apparato Stomatognatico(LAFAS),DipartimentodiScienze BiomedicheperlaSalute,Università degliStudidiMilano, viaMangiagalli31,20133Milano,Italy

FilippoTarabbia¹ Maxillo-FacialSurgicalUnit,OspedaleSanPaolo, DipartimentodiScienzedellaSalute,Università degli StudidiMilano,viaDiRudinì 8,20142Milano,Italy DivisionofMaxillofacialSurgery,Departmentof Neurosciences,ReproductiveandOdontostomatological Sciences,UniversityofNaples“FedericoII”,viaPansini5, 80138Napoli,Italy

SofiaRestelli LaboratoriodiAnatomiaFunzionaledell’Apparato Stomatognatico(LAFAS),DipartimentodiScienze BiomedicheperlaSalute,Università degliStudidiMilano, viaMangiagalli31,20133Milano,Italy Maxillo-FacialSurgicalUnit,OspedaleSanPaolo, DipartimentodiScienzedellaSalute,Università degli StudidiMilano,viaDiRudinì 8,20142Milano,Italy

CorrespondenceandCommunications 3

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GiovanniDell’AversanaOrabona DivisionofMaxillofacialSurgery,Departmentof Neurosciences,ReproductiveandOdontostomatological Sciences,UniversityofNaples“FedericoII”,viaPansini5, 80138Napoli,Italy

ClaudiaDolci LaboratoriodiAnatomiaFunzionaledell’Apparato Stomatognatico(LAFAS),DipartimentodiScienze BiomedicheperlaSalute,Università degliStudidiMilano, viaMangiagalli31,20133Milano,Italy

LuigiCalifano DivisionofMaxillofacialSurgery,Departmentof Neurosciences,ReproductiveandOdontostomatological Sciences,UniversityofNaples“FedericoII”,viaPansini5, 80138Napoli,Italy

FedericoBiglioli Maxillo-FacialSurgicalUnit,OspedaleSanPaolo, DipartimentodiScienzedellaSalute,Università degli StudidiMilano,viaDiRudinì 8,20142Milano,Italy

ChiarellaSforza LaboratoriodiAnatomiaFunzionaledell’Apparato Stomatognatico(LAFAS),DipartimentodiScienze BiomedicheperlaSalute,Università degliStudidiMilano, viaMangiagalli31,20133Milano,Italy E-mailaddress:chiarella.sforza@unimi.it

1Drs.GibelliandTarabbiaequallycontributedtothis paper.

© 2019BritishAssociationofPlastic,ReconstructiveandAesthetic Surgeons.PublishedbyElsevierLtd.Allrightsreserved.

https://doi.org/10.1016/j.bjps.2019.05.036