Acephlalometricstudyof32NorthAmericanblack patientswithanterioropenbite OsmondG.Jones* Washington,D.C. Thepiirposeofthis researchprojectwas,toinvestigateagroupof32NorthAmericanblackpatients wittianterioropetibitea,nd comparethemtoth& Noti,Americanblacknormsestablishedby AltemusandDrummond2andtowhitepopulatiqnnormsMablishedbySteiner.3 In addition,values weke establitihedforblaCk patientsbquseof ,theoverbitedepthindicatorofKim. Themethod involvedthetracingofIa~eral e&ptialdmetricradiugraphsof32patientswithanterioropenbiteusing theanalysesofTtieed,*,Steiner,3andKim. Theresultingangleswereaddedandthemeansand standarddeviationscalculated.0r1 thebasis. of thecriteriaus&d forthisstudy,thesignificantfindings wereas follows:(1) themaxillawasnormallypositionedtothecranialbase;(2) theupperandlower incisors w&eprocumberitwithanacuteinteri,ncisal reltitionship;(3) themandibularpositiontended toberetrllsivetothecranialbase;(4) thelowerfacialheightwasgreaterandthemandibularplane angle(GoGn-SN)wassmallerthanwhitepopulationstandards;and(5) theoverbitedepthindicator ofKim4 wassmallerforthisgroup thanforthewhitepopulationstudied.(AMJORTHODDENTOFAC ORTHOP1$89;95:289-96.) T hepatientwithananteridropenbitehas oneofthemostdifficultorthodonticproblemstocor- rect.Thecause oftheanterioropenbitemaybeboth complexanddifficulttoestablishtindyetis criticaliri developingatreatmentiegimen-thatwillproduceSt&- bilityandsatisfactorycosmeticresults.Althoughnor- malfacesaredifferentforthevtiousracialgroups, cephalonietricstand&rdsareavailableforbothblacks andwhites..fHowever,ourknowledgelargelyrepre- sents thewhitepopulation. Thetreatmentofpatients.withanterioropenbite raisesasmanyproblemsasdeterminingthecalfse. HellmanS(in1931)andNahouri-~~-~(in1974)foundas manysuccesses;as therewerefailuresinthetreatment ofopenbitecases. In1969,Richardson,statedthat theprognosisforthesecases was -either goodorpoor. In197 1,Kim4reportedthatthestate ofcephalometric analysisandknowledgeofthesubjectwasinadequate todiagnoseanopenbit& ordeepbitetendency. Thepurposeofthisstudywasto evaluatetheceph- alometricfeituresofa group ofNorthAmericanblack patientswithanterioroijenbite.These datawereCOT- paredtostandardsestablishedforbothwhiteandblack racialgroupswiththehopethatthesefindingswould beusefulindifferentialdiagnosisandtreatmentplan- ningfororthodonticpatients. *AssistantProfessor,HowardUniversityCollegeofDentistry,Departmentof Orthodontics. METHOD Thisresearchinvolvedtheuseoflateralcephalo- metricradiographsof32blackpatients,aged8to39 years,withclinicallydiagnosedanterioropenbite.The groupwas dividedinto25femaleandseven malesub- jects.Tracingswere madeofx-rayfilmsand landmarks wereidentifiedbyuseoftheanalysesofSteiner,3 Tweed,andKima(Figs.1 through3).Theocclusal planes (Fig.i)andthe A-Bplane(Fig.3) weredrawn. Totalfacialheightandlowerfacialheightweremea- sured accordingtoRichardson,and Nahoum69 (Fig. 2),ahdthe relevantangles fortheSteinerandTweed analyses wererecorded.Thesample was dividedfurther intoskeletalanddentalgroupsbyarbitrarilyusihg GoGn-SNangleof32.5as a division.Anteriorskeletal openbiteswereclassifiedabovethisdivision. Tracingsweredonewithahardpencilon0.003 matteacetate tracingpaperand measurementswere ob- tainedusingcephalometrictracingequipment.*The datawerepresentedintabularformandthemean, range,andstandarddeviationwerecalculated. RESULTS TablesIthroughVincludedatacollectedwithout dividingthesampleintoskeletalanddentalanterior openbiteS;TablesVIandVIIdividethesampleinto skeletalanddentalanterioropenbites. Acomparison(TableI)betweenthepresent *UnitekCorporation.Monrovia,Calif. 289 290Jones Am.J.Orthod.Dentofac.Orthop. April1989 KEY S-nidpointoiPituitaryFoisa NaNaiion SN=Cranialbaseplane 60.Gonion Gn=Gnathion A=Pointofgreatestconvexityon theanteriorofthrmaxilla B=Pointofgreatestconvexityon theanteriorofthemandible Fig.1.Steinersanalysis. studyandnormsestablishedbyAltemu?showedthe following: i .TheopenbitepatientsdidnotdemonstrateSNA anglesthatweiesignificantlydifferentfrom blacknorms. 2.TheSNBvalueS usuallyw&eless thantheblack norms. 3.SNDanglewasgreaterinopenbitecases, but was considerablyless in thoseidentifiedaiskel- etalopenbites. 4.Theupperandlowerincisorsweremorepro- cumbentwithopen bitecases and the interincisal anglewassignificantlysmillerthanthenorm. 5.Openbitepatientshadlarg&GoGn-SNangles. Standarddeviationsforthenormsestablished. by AltemuswereriotavailableandpreventedstatiStica comparisonwiththefiguresfromtheopenbitevalues. IncomparingthesefindingstotheTweed*norms establishedby&ummond*(TableII),theFMAand IMPAangles werenot foundto be significantlydifferent fromthenorm.TheopenbiteFMAanglewaslarger andIMPAanglewassmallerthantheblacknorms. Whenthe blackopen bitecases were comparedwith thewhiteopenbitecases (TableIII),itwasseen that bothracialgroupshad$NAvaluessimilartotheirre- spectivenotis.However,SNBs and interincisalangles weresmallerandGoGn-SNvalueswerelargerthan normal.ThewhitedatahadlargerGoGn-SNvalues. TableIVshows thatthemean openbiteFMAangle wassmallerfortheblacksubjectsthanthatforwhite subjects. Bothopenbiteracialgroupshadincreasedlower facialheight,butoverallblacksubjects hadthelarger value.Theoverbitedepthindicator(ODI)waslower forblacksubjectsthanforwhitesubjects(TableV). Thesamplewasdividedintotwogroupsfo;the iteine?analysis (Table VI).GroupI (skeletal open bite) hadGoGn-SNangleabove32.5andgroupII(dental openbite)hada GoGil-SNanglebelowthispoint. Thereweredifferencesbetweenthegroups.The skeletaltypeshowednomaxillaryprotrusion(SNA, 85=norm).Themandible@ND,74.9)displayed downwardand backwardrotationor retrusion.Ttieskel- etalgroupalsohadmaxillaryincisalprocumbency (&NA,25.5),butthiswasless thanthedentalgroup (I-NA,27;3).Thedentaltypes exhibitedmaxillaryand Volume95 Number4 Cephdometricstudyofblackpatientswithanterioropenbite291 KEY ANS=Anteriornasalspine PNS=Posteriornasalspine ANS-PNS=Palatalplane Ii-Nanton N-N=Totalfacialheight N-ANS-Upperf&J81height ANSM=Lowerfacialheight LA=Longaxis6fthelowerIncisor FrankfurtPlrne=Llnairolathe upperborderoftheexternal auditorynertustothelower borderoftheorbit MandibularPi@no=Linetangential ttithelowerborderofthe mandible Fig.2.Tweedsanalysis. TableI.Comparisonofnormalandopenbitedatabyuse ofSteinersanalysis Blacknorm(Altemus)Blackopenbite(presentsrudyj MeanSD(2)MeanSD(2) SNA85.50 - 85.704.79 SNB81.00 - 79.00Q4.78 ANB4.505.723.57 SND77.00 - 78.605.31 LNA23.00 - 26.037.50 A-NA7.00mm - 8.25mm2.97 LT 119.00 - 111.1011.57 T-NB34.0037.907.82 T-NB10.00mm - ll.OOmm3.36 GoGn-SN32.50 - 35.605.72 mandibularprotrusion(SNA,87;SNB,83,respec- tively)andhadagreaterprocumbencythanthenorm forthemaxillaryincisors(A-NA,27.3). Patientswithskeletalopenbiteexhibiteda greater lowerincisorprocumbency(T-NB,38.5)thanthose withdentalopenbite,and hada moreacute interincisal angle(A-T, 110.8)thaneitherskeletal(blackpatients, 1-T,119;whitepatientsA-T,120)ordentalQ-T, 1i2.20)norms. ComparisonofgroupIandgroup11 fortheTweed 292Jones Am.J.Orrhod.Dentofac.Orthop. April1989 KEYd. 1 A-BPlane=LineJoiningpointsA(LB 9 fromSteinersanalysis c!DI=Thesti.oftheangieformedby8 1.TheHondibular&dA&BPlaner 2.TheFr.arikfUrtandPdlat?lPlanesa, Fig.3.Kimsanalysis(overbitedepthindicator[ODI]). TableII. Comparisonofnormalandopenbitedatabyuse ofTweedsanalysis FMA IMPA FMIA Blacknorm(Drummomf)Blackopenbite(presentstudy) MeanSD(2)MeanSD(*) ;0.6&4.7031.566.67 100.005.0099.507.90 49.405.7049.209.70 analysesindicatedthatFh4Aanglewaslargerforpa- tientswithskeletalopenbiteandtheIMPAanglewas largerforpatientswithdentalopenbite(TableVII). (Thisimpliedthatthe skeletalgroupshoweddownward andbackwardrotationofthemandible.)Thedental groupgenerallyhadsignificantlylowerincisalprocum- bency.Upperfacialheightswerelowerforskeletal open bitecases thanforthedentalcases. ForKimsoverbitedepthindicator,4theskeletal grouphadasmallerODIthanthedentalgroup.Both groupswerebelowthewhitenormof74.50. Dl!$ZUSSlON TableIcomparesthenormaldataestablishedby AltemuswiththeopenbitedatafortheSteinetianal- ysisestablishedbythecurrentstudy.Allthenormal values werewithinone standarddeviationofthe means fortheopenbitevaluesinthestudy.Astatisticalcom- parisonwasnotpossiblesincestandarddeviationsfor thenormalmeans werenotavailable.Instead,theclin- icalsignificanceofthedatawascompared. Therelationshipof.-pointA(seeFig.1)onthe maxillatothe cranialbase (asindicatedbyangleSNA) didnotchangesignificantlyfromthenormalmean. SimilarfindingswerereportedbyHapak13 inastudy of52whitepatientsin1964.Therelationshipofthe mandibleto the cranialbase as shownby theSNB angle indicatedthat the mandiblerotateddownwardand back- ward.ThiswascontradictedbytheSNDmeanvalue, whichincreased.Theincreasewasattributedtothe inclusionofbothskeletalanddentalopenbitecases in thegroupsused forthe study.WhenincludingtheSND Volume9s Number4 Cephnlometricstudyofblackpatientswithanterioropenbite293 TableIII.Comparisonofblackandwhiteopenbitedatabyuse ofSteinersanalysis Blackopenbite(presentstudy)Whiteopenbite(Hapak)* MeanSD(?IMeanSD(*i SNA SNB ANB AT GoGn-\SN ___- *Otherdataunavailable. 85.654.7980.IO3.23 79.904.7875.903.79 5.723.574.202.88 111.1011.57120.0010.49 35.605.7238.567.19 TableIV. Comparisonofblackandwhiteopenbitedatabyuse ofTweedsanalysis Blackopenbite(presentstudy)Whiteopenbite(Hapak) MeanSD(2)MeanSD(2) FMA IMPA FMIA 31.566.67 99.507.90 49.209.70 33.40 - Unavailable Unavailable TableV. Comparisonofblackandwhitedata:Overbitedepthindicator(ODI)andupperfacialheight/total facialheight(IJFH/TFH)byuse ofKimsanalysis Blackopenbite(presentstudy)Whitedata MeanSD(2)MeanSD(?) ODI66.146.7814.506.07norm(Kim4) UFHiTFH40.90%3.5842.80%-Openbite(Hapal?)* *NormUFHITFHunavailableforblacksubjects. valuesforthedentalopenbites,themeanvaluefor SNDanglewouldbeelevatedbecausetheskeletalre- lationshipswereclosertothenorm. Thevaluesfortherelationshipoftheupperincisor tothemaxillaryI-NAangleandmillimetermeasure- mentindicatedthattheupperincisorswerenoticeably moreprocumbentinopenbitecases. Thiswas reported in previousstudies such as the onebyHapak13 in1964. Thediminishedinterincisalanglealso indicatedthatthe incisorsweremoreprocumbent.Theanglemadeby thelowerincisorandthemandible(T-NB)showeda markedprocumbencyofthelowerincisors. Themandibularplaneangle(GoGn-SN)showedan increase abovet.he normalmean.Mizrahi,14Hellman, Nahoum,6-and others.indicatedin theirstudies that the mandibularplaneangle increased in open bitecases. TableIIshowsthefindingsofthe presentstudyfor theTweedIanalysis.Theresultswereunexpected. ComparedwiththenormsestablishedbyDrummond (TableII),theanglebetweentheFrankfortplaneand themandibularplane(FMA)increasedsignificantlyat the0.01level.TheIMPAand FMIAanglesshowedno significantdifferencefromthenorms.Thiswassome- whatsurprisingsinceareviewoftheliteraturehad indicatedthatchangesinthelowerincisorangulation shouldhavebeenexpected. Ina comparisonbetweenblackandwhitepatients withanterioropenbite(TablesIIIandIV),significant numericaldifferenceswerenoted.Bothgroupsalso exhibitedthesame trends.For example,bothhadSNA valuesthatwerevirtuallythesame as normalandSNB anglewasreducedinbothgroups.Thedataforwhite patientsweretakenfromresearchbyHapakin1964 onan openbitesampleof52cases. Thearticledidnot specifywhetherthegroupwasskeletalordentalin nature. 294Jones Am.J.Orthod.Dentofac.Orrhop. April1989 TableVI.ComparisonofgroupIskeletalandgroupIIdentaldatabyuse ofSteinersanalysis SNA SNB ANB SND I-NA A-NA 1T T-NB T-NB GoGn-SN Skeletalopenbite,groupIDentalopenbite,groupII (presentstudy)(presentstudyJ MeanSD()MeanSD(2) 85.004.1087.303.50 78.703.9683.003.00 6.303.105.602.29 74.904.7279.303.30 25.507.6027.307.60 7.90mm2.809.20mm3.50 110.8010.37112.2014.90 38.507.7036.109.19 11.80mm3.269.00mm2.69 38.303.7928.703.57 TableVIIA.ComparisonofgroupIskeletalandgroupIIdentaldatabyuse ofTweedsanalysisand KimsODI Tweedsanalysis FMA IMPA FMIA Kimsoverbitedepthindicator(ODI) ODI GroupIopenbite (presentstudy) MeanSD(2) 33.305.50 99.107.20 47.719.10 65.506.60 GroupIIopenbite (presentstudy) MeanSD(2) 27.507.70 100.609.78 53.0010.60 67.807.20 TableVIIB.UFH/TFHdata(meanfSD) UFIWTFH GroupIopenbite (presentstudy) 40.40%*3.90 GroupIIopenbite (presentstudy) 42.20%i 2.20 Steinersdata3 forthetworaces werecomparedin TableIIIand the differencesweresignificantat the 0.05 level.Thedifferencesin theSNA,SNB,and 1: T values weresignificantat the 0.001level.The GoGn-SNangle of38.56t7.19inwhitedentalopenbitesubjects was higherthan thatof blacksubjects-35.6?5.72; it was approximatelythesame as thatforblacksubjects intheskeletalgroup-38.3+3.79.Thiswasan unusualfinding;possiblyHapak13 studiedagroupof predominantlyskeletalopenbitepatients.Thismight explainthesimilaritybetweentheraces intheskeletal cases. OnlyangleFMAwasavailableforracialcompar- isonswiththeTweedanalysis(TableIV)andasta- tisticalcomparisonwasnotpossiblebecause ofincom- pletedata. TableVindicatesthattheblackopenbitepatients hadlonger,lowerfacesthanthewhitepatients.This was an expectedfindingsince studies on normalpatients byAltemusalreadyhas displayedthistrend. Theblackpatientsampleevaluatedinthisstudy showedthefollowing: 1.Upperfacialheighttototalfacialheight- 40.9-+3.58 2.Kimsoverbitedepthindicator(OD1)4- 66.14f6.78;thenormestablishedbyKim Volume95 Number4 Cephalometricstudyof blackpatientswithanterioropenbite295 on119whitepatientswas74.5+6.07.The differencebetweenthesetwofigureswassig- nificantatthe0.001level. Throughouttheliteratureithadbeenstatedthat openbitepatientshadsignificantlylargerGoGn-SN anglesthanthenorm(32.5)establishedbyAlte- mus(HellmaqsNahoum,6-9andMizrahi14).Na- houm6-9 statedthatthereweretwotypesofopenbite cases-namely,skeletal(groupI)anddental(group II).Themeanmandibularplaneangle(GoGn-SN)pro- ducedbythisstudy,althoughlargerthanthe norm,was notas largeas, mighthavebeenexpected.Itwasbe- lievedthatthecases includedbothskeletalanddental types.Aneffortwasmadetoidentifythetwogroups bydividingthe cases intoonegroup(groupI,skeletal), whichhadGoGn-SNangleshigherthanthenorm (32.5,Altemus),and anothergroup(groupII,dental) withGoGn-SNangles 32.5and below.The mandibular planeangle(GoGn-SN,32.5)wastakenfromthe normsestablishedforblacksbyAltemus(TableI). InTableVIthetwogroupswerecomparedand Studentsttestappliedtocheckthenumericaldiffer- encesforstatisticalsignificance.Thedifferencebe- tweentheSNAvaluesforbothgroups(skeletaland dental)wasnotsignificantatthe0.1level,norwas theremuchdifferencebetweentheoverallfigurefor openbitesfor1:his studyandthenormestablishedby Altemus.Thereforeit seemedthattheSNAanglewas notsignificantlychangedbytheopenbitecondition. ThiswasalsoafindingofHapakinhisstudyof52 openbitewhitepatients. TheSNBvaluesforthetwogroups(skeletaland dental)weresignificantlydifferentatthe0.01level. The skeletal openbite groupI had a reducedSNBangle. Thedentalopen1bitegroupIIdisplayedlittledifference fromthenorm.whiletheskeletalgrouphada signifi- cantlyreducedSNBangle.TheANBdifferencebe- tweenthetwogroupswasnotstatisticallysignificant atthe0.1level.Itcanbe concludedthatskeletalopen bitecases hadsignificantlyreducedSNBandSNDan- gles.Thiswascaused bybackwardanddownwardro- tationofthemandible. Thepositionoftheupperincisorsin relationtothe NAlinewasmoreprocumbent;thedifferencebetween thetwogroupswas statisticallysignificantand theden- talopenbitegroupshowedgreaterprocumbency.This wasnotunexpectedsinceincreasedprocumbencyof theincisorswas necessary to producean openinginan otherwiseskeletallynormalfaceanddentition. Theinterincisalangleshowednostatisticallysig- nificantdifferenfzebetweenthetwogroups;theangle wasmoreacutethanthenorminbothgroups.Itwas expectedthattheinterincisalanglewouldhavebeen even moreacute in dentalopenbite cases. Skeletal open bitescausedbywhatSchudyhas describedas a hy- perdivergentskeletalpatternwouldneedlessdental procumbencytoproduceanopenbite. Thelowerincisorposition(T-NB)forbothgroups showednostatisticaldifferencebetweenthegroups. Bothhadgreaterprocumbencythanthenorm. ThedatafortheTweedanalysisforbothgroups werecomparedinTableVII.Ofthethreeparameters, onlyone-theFMAangle-showedasignificantdif- ferencebetweenthegroupsatthe0.1level.Thiswas expectedsincethebasisonwhichthetwogroups weredifferentiatedwasaGoGn-SNangleabove normalandGoGn-SNbelownormal,normaltakento be32.5. Theratioofupperfacialheightto totalfacialheight showednosignificantdifferencebetweenthe groupsat the0.1level.Thiswas a particularlysurprisingfinding becauseoneofthepointsemphasizedintheliterature byMizrahi14wasthatskeletalopenbitepatientshad greaterfacialheights.Thereasonthetwogroups showedlittledifferencemayhave been the samplesize. Morestudies need tobe undertakenonopenbitecases. Itispossiblethattheextremeswithinthetwogroups caused thevalues toaverageout.Thevalues produced bythetwogroupsfromKimsODPwerenotstatisti- callydifferentatthe0.1level. CONCLUSIONS Thefollowingconclusionsweredrawnfromthis study. 1.Blackanterioropen bite patientshad SNAangles close tothe norm;SNBangles wereless thanthenorm. Interincisalanglesweremoreacutethannormaland bothupperandlowerincisorsweremoreprocumbent thanthenorm. 2.Dentalanterioropenbitecases (groupII)had maxillaryprotrusionandagreaterupperincisalpro- cumbency.However,skeletalopenbitepatients(group I)showedbackwardanddownwardrotationofthe mandible,greaterlowerincisalprocumbency,and GoGn-SNvaluesabovethenorm. 3.A comparisonof anterioropenbite data forblack andwhitesubjects showedthatblacksubjects hadlon- gerlowerfacialheightsandwhitesubjectshadnu- mericallylargerGoGn-SNvalues. REFERENCES 1.AltemusLA.Acomparisonofcephalometricrelationships.An- gleOrthod1960;30:223-40. 2.DrummondRA.Adeterminationofcephalometricnormsforthe Negrorace.AMJORTHOD1968;54:670-82. 3.SteinerCC.Cephalometricsinclinicalpractice.AngleOrthod 1959;29:8-28. 296Jones Am.J.Orrhod.Dentojac.Orthop. April1989 4.KimYH.Overbitedepthindicatorwithparticularreferenceto anterioropen-bite.AMJORTHOD1974;65:586-611. 5.HellmanM.Open-bite.INTJORTHOD1931;17:421. 6.NahoumH.Verticalproportionsandthepalatalplaneinanterior open-bite.AMJORTHOD1971;59:273-82. 7.NahoumH.Varietiesofanterioropen-bite.AMJORTHOD 1972;61:486-92. 8.NahoumH.Anterioropen-bite:acephalometricanalysisand suggestedtreatmentprocedures.AMJORTHOD1975;67:513-21. 9.NahoumH.Verticalproportions:aguideforprognosisandtreat- mentinanterioropen-bite.AMJORTHOD1975;72:128-46. 10.RichardsonA.Skeletalfactorsinanterioropen-biteanddeep overbite.AMJORTHOD1969;56:114-27. 11.RichardsonA.Dento-alveolarfactorsinanterioropenbiteand deepoverbite.DentPratt1970;21:53-7. 12.TweedCH.TheFrankfort-mandibularplaneangleinorthodontic diagnosis,classification,treatmentplanning,andprognosis.AM JORTHODORALSURG1946;32:175-230. 13.HapakFM.Cephalometricappraisaloftheopenbitecase.Angle Orthod1964;34:65-73. 14.MizrahiE.Areviewofanterioropenbite.BrJOrthod1978;s: 21-7. 15.SchudyFF.Thecontrolofverticaloverbiteinclincialortho- dontics.AngleOrthod1968;38:19-39. 16.AthertonJD.Theinfluenceofthefaceheightupontheincisor occlusionandlipposture.DentPratt1965;15:227-31. 17.BaumeL.Uniformmethodsfortheepidemiologicassessment ofmalocclusion.AMJORTHOD1974;66:251-72. 18.BjorkA.Thefaceinprofile.Lund,Sweden:BerlingskaBok- tryckeriet,1947. 19.DeCosterL.Open-bite.INTJORTHOD1936;22:912-38. 20.GershaterMM.Theproperperspectiveofopenbite.AngleOr- thod1972;42:263-72. 21.HelmS.MalocclusioninDanishchildrenwithadolescentden- tition:anepidemiologicstudy.AMJORTHOD1968;54:352-66. 22.JohnsonEL.TheFrankfort-mandibularplaneangleandthefacial pattern.AMJORTHOD1950;36:516-33. 23.KandilE,FahmyMS.Openbiteandthumbsucking.JMed Liban1974;27:219-22. 24.LemerHI.Thumbsuckinganddentalocclusion.AMJORTHOD 1955;41:640. 25.MillsLF.Theprevalenceofmalocclusioninapopulationof 1,455schoolchildren.JDentRes1966;45:332-6. 26.MossML.Differencesbetweenthefunctionalmatricesinan- terioropen-biteandindeepbite.AMJORTHOD1971;60:264- 80. 27.PrakashP,MargolisH.Dento-craniofacialrelationsinvarying degreesofoverbite.AMJORTHOD1952;38:657-73. 28.RickettsRM.Theinterdependenceofthenasalandoralcapsules. In:McNamaraJAJr,ed.Naso-respiratoryfunctionandcranio- facialgrowth.CraniofacialGrowthSeries.AnnArbor:1979. CenterforHumanGrowthandDevelopment,Universityof Michigan. 29.SassouniV,NandaS.Analysisofdentofacialverticalpropor- tions.AMJORTHOD1964;50:801-23. 30.SubtelnyJ,SakudaM.Open-bite:diagnosisandtreatment.AM JORTHOD1964;50:337-58. 31.SwinehartEW.Relationofthumb-suckingtomalocclusion.AM JORTHODORALSLRG1938;24:509. 32.WylieW,JohnsonE.Rapidevaluationoffacialdysplasiainthe verticalplane.AngleOrthod1952;22:165-82. 33.SassouniV.Aclassificationofskeletalfacialtypes.AMJORTHOD 1969;55:109-23. 34.SwindlerD,SassouniV.Openbiteandthumbsuckinginrhesus monkeys.AngleOrthod1962;32:27. 35.KincaidRM.Frequencyofdeglutitioninitsrelationshipto overbite.AngleOrthod1951;21:34. 36.LearCS.Variabilityofheadpostureduringsleepandconsid- erationsrelatingtopalateanddentalarchform.ArchOralBiol 1967;12:1229-40, 37.KazmierczakD.Roleofabnormalitiesofdeglutitionintheetiol- ogyofinfraclusion.RevStomat1966;67:29-35. 38.RuttleA,QuigleyW,CrouchJ,DwanG.Aserialstudyofthe effectsoffingersucking.JDentRes1953;32:739-48. Reprintrequeststo: Dr.OsmondG.Jones DepartmentofOrthodontics CollegeofDentistry HowardUniversity 600WStreet,NW Washington,DC20059