Orthodontic study models

Orthodontic study model are presented

1. Orthodontic
Study Models
Dr. Maher Fouda
Professor of orthodontics
Mansoura Egypt

2. Orthodonticstudymodelsareessential
diagnosticrecords,whichhelptostudythe
occlusionanddentitionfromallthree
dimensions.Theyareaccurateplaster
reproductionsoftheteethandtheir
surroundingsofttissues.

3. REQUIREMENTS OF ORTHODONTIC
STUDY MODELS
1. Models should accurately reproduce the teeth and
their surrounding soft tissues.
2. Models are to be trimmed so that they are symmetrical
and pleasing to the eye and so that an asymmetrical arch form
can be readily recognized .
3. Models are to be trimmed in such a way that the dental
occlusion shows by setting the models on their backs.
4. Models are to be trimmed such that they replicate the
measurements and angles proposed for trimming them.
5. Models are to have clean, smooth, bubble-free surfaces
with sharp angles where the cuts meet.
6. The finished models should have a glossy mar proof Finish.

4. Importance of models
1. They are invaluable in planning treatment, as they are the only three
dimensional records of the patient’s dentition.
2. Occlusion can be visualized from the lingual aspect.
3. They provide a permanent record of the intermaxillaryrelationships and
the occlusion at the start of therapy: this is necessary for midicolegal
considerations.
4. They are a visual aid for the dentist as he monitors changes taking place
during tooth movement.
5. Help motivate the patient, as the patient can visualize the treatment
progress.
6. They are needed for comparison at the end of treatment and act as a
reference for posttreatmentchanges. .
7. They serve as a reminder for the parent and the patient of the condition
present at the start of treatment.
8. In case the patient has to be transferred to another clinician, study models
are an important record.

5. USES OF STUDY MODELS
1. Assess and record dental anatomy
2. Assess and record intercuspation
3. Assess and record arch form
4. Assess and record the curves of occlusion
5. Evaluate occlusion with the aid of articulators
6. Measure progress during treatment
7. Detect abnormality, e.g. localized enlargements, distortion
of arch form, etc.
8. Calculate total space requirements/discrepancies
9. Provide record before, immediately, after and several years
following treatment for the purpose of studying treatment
procedures and stability.

6. Thestudymodelscanbedividedintotwopartsforthe
purposeofdescription.
Theanatomicportion
2.Theartisticportion
.Theanatomicportionisthatpartwhichistheactual
impressionofthedentalarchanditssurroundingsoft
tissuestructures.Thisisthepart,whichmustbe
preservedwhentrimmingthemodel
.Theartisticportionisthestonebasesupportingthe
anatomicportion.Thisportionistrimmedinamanner,
whichdepicts,inageneralway,thedentalarchform
andispleasingtotheeye.
PARTS OF THE STUDY MODELS

7. FABRICATION AND TRIMMING OF
STUDY MODEL
Preliminary procedures in the fabrication of study
models are:
1. Remove any excess flash or obviously excessive
bulk on the periphery of the models.
2. Remove any nodules that may be present on the
occluding surfaces of the teeth.
3. Remove any extensions in the posterior areas
that prevent occluding of the models.
4. Using the wax bite, occlude the models.

8. STEPS IN ART PORTION FABRICATION
1-Determinetheocclusal
planeofthedentition.
Oncethishasbeen
determined,thebaseof
thelowermodelis
trimmedparalleltothe
occlusalplane.The
occlusalplane is
consideredtobethe
highestthreepointsof
theeruptedteeth.

9. 2.Trimthebackofthelowermodel
perpendiculartothebase.Thisisdone
onanearsymmetricalmodelby
measuringthedistancefromthedistal
ofthefirstmolarsorsecondbicuspids
tothebackofthemodelonboththe
leftandrightsides.Onamodelthatis
notsymmetrical,compensationmust
bemadetokeepthebackasnear
perpendiculartothemidlineas
possible.Themidlineofthelower
modelshouldnormallycorrespond
favorablywiththeuppermid-palatal
raphae.Itisgenerallyeasiertolocate
themidlineinthemaxillarycast.The
backistrimmedsothatitis90degrees
tothebaseofthemodel.

10. Theposteriorsurfaceshouldnotbetrimmed
tooclosetotheposterioraspectofthe
mandibularteeth,asthehamularnotchofthe
uppermodelgovernsthedistance,thissurface
'shouldbefromtheteeth.
3.Totrimthebackoftheuppermodel,occludethe
modelsutilizingthewaxbite.Thewaxbitenot
onlymaintainsthecorrectinterrelationshipbut
willalsohelptopreventfracturingoftheteeth.
Carefullytrimtheposteriorsurfaceofthe
occludedmodelssothattheuppermodel
matchesthatofthelowermodel.Thebackof
theupperandlowermodelsshouldnowbe90°
tothebaseofthelowermodel.Trimthe
posteriorsurfacesofbothmodelsuntilyouare
justposteriortothehamularnotchwhich
shouldbeseveralmillimetersposteriortothe
lasttooth.

11. 4.Trimthebaseoftheuppermodelso
thatitisparalleltothebaseofthe
lowermodel.Trimuntilthetopbaseis
flat,butleaveseveralmillimetersof
extraheightsotheocclusalplaneof
themodelscanbecenteredandthe
modelsfinishedtothespecified
dimension.
Theocclusalplaneshouldbecentered
betweenthetopofthemaxillary
modelandthebaseofthemandibular
model,whenthemodelsareoccluded
withoutthewaxbite,themodels
beingviewedfromthebuccaI.

12. 5.Nowwehavetwobases
paralleltoeachotherandto
theocclusalplane.Thebacks
ofboththeupperandlower
basesareatrightanglestothe
bases,theocclusalplaneand
to the mid-palatal
aponeurosis.
Fromhereonwards,theupper
andlowermodelsshallbe
trimmedindependentlyof
eachother.

13. The Lower Model
1.Makethebuccalcutsontheedgeof
thevestibuleat60°angletobalk.
Theedgeofthevestibuleistakenas
apointapproximately5to6mm
awayfromthemostprominentpoint
ofthelowercanineorfirstbicuspid
tooth(whicheverismoreprominent).
Themodelistrimmedtothispoint
providedthatthisdoesnotcut
beyondthedeepestpointofthe
vestibuleintheregionofthefirstor
secondmolar.Ifthisguidelinewould
placethecutbeyondthedepthof
thevestibule,thenitisadvisableto
usethedepthofthevestibuleto
determinethedepthofthebuccal
cuts.

14. 2.Theanteriorsegmentofthe
lowerarchistrimmedintoa
curve,whichshouldfollowthe
arcofacircle.Theradiusof
thissegmentofthecircleshou
Idrepresentthegeneral
curvatureoftheloweranterior
teeth.Thefinishedmodel
shouldhavethiscurve
trimmedtowithin5to6mm
oftheanteriorteeth.

15. 3.Theheelsofthelowermodel
arecutatapproximately115°to
thebackofthemodel.Thefloor
ofthemouthshouldbeleveled
andsmoothedtoformaflat
surface.
Theidealsetofmodelswillhave
theartportionrepresenting
approximatelyl/3rdofthetotal
heightandtheanatomicportion
approximately2/3rdofthe
height.

16. The Upper Model
1.Makethebuccalcutstothe
edgeofthevestibuleatan
angleof60°tothebackofthe
model.
2.Maketheanteriorcutssothat
theendsareatthemidline
andapproximatelyinthe
caninearea.Thiscutshould
beapproximately5to6mm
fromthelabialsurfaceofthe
anteriorteeth,withbothsides
ofequallengthandtheir
intersectiononthemidline.
Make buccal cuts. at the edge of the vestibule 60°
to back of the model
Make anterior cuts. the ends of which should be at
the midlineand the middle of each canine

17. 3.Theheelsoftheupper
modelareformedby
occludingboththe
modelsandfinishing
themsuchthattheyare
flushwiththeheelsof
thelowertothebiteof
themodelthattheyare
flushwiththeheelsof
thelowermodelsat115°
.Theheelsoftheupper
modelmaynotbethe
samelengthasthoseof
thelowermodel.
Occlude models. Trim upper heels so they are flush
with lower heels

18. 4. The finished height of the occluded models
should be 7 cm .
Occluded models should have a sharp 90°angle between
their base and back

19. Commerciallyavailableplastic
basesarenowavailable
whichcanbeusedtobase
theupperandlowermodelin
articulation.Thesebasesoffer
theadvantagethattheyhave
astandardsize,madeof
plasticandhenceareeasyto
store.Theprocedureinvolved
forusingpreformedplastic
basesforbasingofmodelsis
asfollows:

20. 1.Usingapencilandthe
mid-palatalrapheasa
reference,markthe
midlineofthemaxillary
cast.Matchthemid
palatalplanetothe
symmetricscribelineon
thepositioningplate.
Securethemodelinthis
positionagainstthe
speciallyprovidedhooks
usingelastics
The positioning plate stabilized using elastics

21. 2.Nowtaketheupperplasticmodelbaseand
placethedovetailsintotherearguiderails
withtherestpointoutwardsandthebeveled
edgeupwards.Theuppermodelbaseiseasily
recognizablebytheanteriorintercanine
squareshape.Poursufficientquantityofwell
spatulatedplasterintotheuppermodelbase
andinsertthepositionplatealongwiththe
stabilizeduppermodelintotheguiderails
untilthefootofthepositioningplatetouches
thetabletop.Theexcessplastershouldbe
removedandthesurfacesmoothened.The
elasticscanbecutandremovedafterthe
initialsettingoftheplasterhastakenplace.
Oncetheplasteriscompletelyset,the
positionplateandtheguiderailscanbetaken
.off
The stabilized upper model placed in the
upper model base loaded with plaster

22. 3.Theguidesmustbeseatedagain
intotheseatsoftheupper
modelplasterbasewiththerest
pointdirectedtowardsthe
modelandtheedgeupwards.
4.Placethelowermodelinto
articulationwiththeupper
modelandstabilizeitwith
elastics.Thelowerbaseisnow
loadedwithasuitablequantity
ofwellspatulatedplasterand
seatedoverthelowermodel
withtheguiderailsintothe
seatsofthelowerplasticmodel
base,untiltheyareincontact
withtherestpoint.
Lower model stabilized in articulation using
elastics
Guides seated into the seats of the upper model
plaster base with the rest point directed towards the
model and the edge upwards

23. 5.Theexcessplastercanbe
removedandthemodels
finished.
6.Therailscanbereplacedwith
thehingeswhichkeepthe
modelsinocclusionandactas
hingejointsfordemonstration
purpose
The based models in occlusion
The based models with hinges act as
joints for demonstration

24. FinishingtheModels
Thesurfacemustbemadesmooth,remainingatthesame
timeabsolutelyflatandatrightanglestothebasesofthe
models.Thefinishingprocessshouldnotchangethe
dimensionsoranyoftheangulationsofthemodels.Inthe
carborandumstonetechnique,themodelisrubbedoverthe
stonewithanevenpressureunderastreamofwateruntila
smoothsurfaceresults.Themethodistorubthemodelona
frostedglasssurface.Afterthesurfaceshavebeenfinished,
andtheexactdimensionsachieved,themodelissetasideto
dryfor48hoursordriedovernightinanorthodonticoven.At
thispointthemodelshouldbelabeledwiththepatient's
nameanddateonthebacksofboththeupperandlower
models.

25. Thefinalglazingisputonthemodelsbyimmersingthemina
commercialgloss.Themodelsareallowedtoremaininthis
solutionforone-halfhour.Holdingeacharchundercold
water,themodelsarepolishedandsoapsolutionremovedby
buffingwithcotton.Themodelsaresetontheirocclusal
surfacestodryforanothertwelvehours,thenbuffedwitha
verylightbutrapidmotionusingcotton.Themodelsshould
assumeahigh,evenlusterwhichwillthenresistsoilingwhile
handling.
Themodelsshouldbeplacedonaflatsurfacewiththeirbacks
down.Theyshouldbepickeduptogetherandalways
returnedtogether.Individualhandlingofthemodelsismore
likelytoresultindamagetothemodels.

26. CastTrimmingtoIndicateOcclusalPlaneRelationships
Thegnathostatictechnique,wasintroducedbySimonin1962.
Itreproducestheinclinationoftheocclusalplanewith
referencetotheeye-ear(Frankforthorizontal)plane.
Trimmedinthisfashion,thecastsshowtheapproximate
inclinationoftheocclusalplaneinthefaceofthepatient.This
informationisvaluable,butcanbegainedmoreaccurately
withtheuseofcephalogram.Alsothecastssoproducedare
notestheticallypleasingastheylacksymmetry.

27. MODEL ANALYSIS
Pont’sAnalysis
In1909Pontpresentedtothe
professionasystemwhereby
themeremeasurementof4
maxillaryincisorsautomatically
establishedthewidthofthe
archinthepremolarandmolar
region.Thegreatestwidthof
theincisorsismeasuredwith
calipersrecordedonaline,and
theirsumsthenrecordedin
millimeters(SumofIncisors)
Sumofthemesiodistalwidthsofindividualincisor
teethisaddedtocalculatethearchwidthinthe
posteriorregion

28. Thedistancebetweenthe
upperrightfirstpremolarand
upperleftfirstpremolar(i.e.
thedistalendoftheocclusal
groove)isrecordedandcalled
asMeasuredPremolarValue
(MPV).
Thedistancebetweenthe
upperrightfirstmolarand
upperleftfirstmolar(i.e.the
mesialpitsontheocclusal
surface)isrecordedandis
termedasMeasuredMolar
Valuewhereasonthe
mandibularteeththepoints
usedarethedistobuccalcusps
ofthefirstpermanentmolar
Measured molar value (MMV) in the maxillary arch

29. Calculated premolar value (CPV) The expected arch width in
the premolar region is calculated by the formula:
SI x 100
80
Calculated molar value (CMV) The expected arch width in the
molar region is calculated by the formula:
SI x 100
64
The difference between the measured and calculated values
determines the need for expansion. If measured value is less,
expansion is required.
Pont's index gives an approximate indication of the degree of
narrowness of the dental arches in a case of malocclusion and
also the amount of lateral expansion required for the arch to
be of sufficient size to accommodate the teeth in perfect
alignment.

30. DrawbackofPant'sAnalysis
1.Maxillarylateralsaretheteethmostcommonlymissingfromtheoral
cavity.
2.Maxillarylateralsmayundergomorphogeneticalterationlike'peg'shaped
latera1.
3.ThisanalysisisderivedsolelyfromthecastsoftheFrenchpopulation.
4.Itdoesnottakeskeletalmalrelationshipsintoconsideration.
5.Itmaybeusefultoknowthedesiredmaxillarydimensionforacase,butit
ismoredifficulttoachievethecorrespondingmandibulardimensionsthat
arenecessarytomaintainabalancedocclusalrelationship.
6.Pont'sindexdoesnotaccountfortherelationshipoftheteethtothe
supportingbone,orthedifficultiesinincreasingthemandibular
dimensions.Itshouldalwaysberememberedthatthepatient'soriginal
mandibularandmaxillaryarchformshouldbeconsideredastheultimate
guideforarchwidthratherthanthevaluesarrivedatbyusingthePont's
index.

31. LINDER HARTH INDEX
Linder Harthproposed an analysis, which is very similar to
Pont's analysis. However he made a variation in the
formula to determine the calculated premolar and molar
value. The calculated premolar value is determined using
the formula:
SI x 100
85
The calculated molar value is determined using the
formula:
SI x 100
64
where SI = sum of mesiodistalwidth of incisors.

32. KORKHAUS ANALYSIS
Thisanalysismakesuseofthe
LinderHarth'sformulato
determinetheidealarchwidthin
thepremolarandmolarregion.An
additionalmeasurementismade
fromthemidpointoftheinter-
premolarlinetoapointinbetween
thetwomaxillaryincisors.
AccordingtoKorkhaus,foragiven
widthofupperincisorsaspecific
valueofthedistancebetweenthe
midpointofinterpremolarlineto
thepointbetweenthetwo
maxillaryincisorsshouldexist.
Measurement of anterior arch length (occlusal view)

33. Incaseofproclinedupperanteriors,
anincreaseinthismeasurementis
seenwhileadecreaseinthisvalue
denotesretroclinedupperanteriors.
Forthevaluesnotedthe
mandibularvalue(LI)shouldbe
equaltothemaxillaryvalue(Lu)in
millimetersminus2mm.
Measurement of anterior arch length (lateral view)

34. ASHLEY HOWE'S ANALISIS
AshleyHoweconsideredtoothcrowdingtobedueto
deficiencyinarchwidthratherthanarchlength.He
foundarelationshipbetweenthetotalwidthofthe
mesiodistaldiametersofteethanteriortothesecond
permanentmolarsandthewidthofthedentalarch
inthefirstpremolarregion.

35. Definitions
Totaltoothmaterial(TIM)Referstothesumof
themesiodistalwidthoftheteethfrom
firstmolartofirstmolar(inclusiveofthe
firstmolars),takenoncastsofthedental
arches,measuredwithdividersora
Boley'sgauge.
2. Basal arch length (BAL)In the maxilla the
median line measurement from Downs A
point is projected perpendicularly to the
occlusalplane, then to the median point on
a line connecting the distal surface of first
molars .
In the mandibulararch the measurement is
made from Downs B point to a mark on the
lingual surface of the cast in the same
manner as in the maxilla
Total tooth material
Maxillary basal arch length

36. 3.Premolardiameter(PMD)Isthe
archwidthmeasuredatthetopof
thebuccalcuspofthefirst
Premolar
4.Premolarbasalarchwidth
(PMBAW) Isobtainedby
measuringthediameterofthe
apicalbasefromcaninefossaon
onesidetothecaninefossaonthe
othersideorelse8mmbelowthe
chestofinterdentalpapilla
betweenlOPbelowthecanineand
firstpremolarwiththelowerendof
theBoley'sgauge.
Premolardiamete
Mandibularbasal arch length

37. According to Ashley Howe, to determine whether the apical bases of the patient could
accommodate the
patients' teeth, the following measurements have to be obtained:
1. Percentage of premolar diameter to tooth material is obtained by dividing the PMD
by the total tooth
material.
PMD x 100
TTM
2. Percentage of premolar basal arch width to tooth material is obtained by dividing
the premolar basal arch width by the total tooth material.
PMBAW x 100
TTM
Percentage of basal arch length to tooth material is obtained by dividing the basal arch
length by total tooth material.
=BAL x 100
TTM
Comparison between PMBAW and PMD gives an idea of the need and the amount of
expansion required and PMBAW% gives an indication towards an extraction or
non-extraction treatment plan.

38. Inference
a.Ifthewidthbetweenthecaninefossaisgreaterthan
thewidthofthepremolars(PMBAW>PMD),itisan
indicationthatbasalarchissufficienttoallow
expansionofthepremolars.Ifthecaninefossawidth
orPMBAWislessthanPMDtherecanbe3
possibilities:
•Don'ttreat.
•Moveteethdistallytowiderpartofthearch.
•Extractsometeeth.

39. b.AccordingtoHowe,toachieveanormalocclusionwithafull
complementofteeththecaninefossameasurement
(PMBAW)shouldbe44percentofthesumofthemaxillary
toothdiameter.Whenthisratioisbetween37percentand44
percent,extractionoffirstpremolarsisdoubtful,andthecase
isconsideredtobeintheborderlinecategory.Whenitisless
than37percent,thenitisconsideredtobedefinitelyacase
forfirstpremolarextractionasitisabasalarchdeficiency.
Anyvalue,44percentoraboveindicatesanon-extraction
case.
Therefore,thisanalysisisausefultreatmentplanningtooland
helpstodeterminewhethertoextractorexpand.

40. WAYNE A. BOLTON ANALYSIS
Boltonpointedoutthattheextractionofonetoothorseveral
teethshouldbedoneaccordingtotheratiooftoothmaterial
betweenthemaxillaryandmandibulararch,togetideal
interdigitation,overjet,overbiteandalignmentofteeth.To
attainanoptimuminter-archdentalrelationship,the
maxillarytoothmaterialshouldapproximatedesirableratios,
ascomparedtothemandibulartoothmaterial.Bolton's
analysishelpstodeterminethedisproportionbetweenthe
sizeofthemaxillaryandmandibularteeth.

41. ProcedurefordoingBoltonAnalysis
The sum of the mesiodistal diameter of the 12 maxillary teeth
(sum of maxillary 12 )and the sum of the mesiodistal diameter
of the 12 mandibular teeth (sum of mandibular 12) including
the first molars are determined. In the same manner, the sum
of 6 maxillary anterior teeth (sum of maxillary 6) and the sum
of 6 mandibular anterior teeth from canine to canine (sum of
mandibular 6) is determined .
Overall ratio The sum of the mesiodistal widths of the 12
mandibular teeth should be 91.3 percent the to Bolton. This
ratio is calculated using the following formula:
Overall ratio = sum of mand. 12 x 100
sum of max.12

42. Sum of the mesiodistal widths of the maxillary
and mandibular teeth

43. The sum of the 12 maxillary and 12 mandibularteeth for a
given patient is inserted into the formula and the overall ratio
is determined. If the overall ratio is greater than 91.3 percent,
then the mandibulartooth material is excessive. The amount
of mandibulartooth material excess is calculated by using the
formula:
Mandibularoverall excess =
sum of mand.12 -{sum of max.12 x 91.3}
100

44. If the overall ratio is less than 91.3 percent, then the maxillary
tooth material is excessive. The amount of maxillary tooth
material excess is calculated by using the formula:
Overall maxillary excess =
sum of max. 12{sum of mand.12 x 100}
19.3

45. Anterior ratio This ratio can be found out using the formula:
Anterior ratio= sum of mand. 6 x 100
sum of max. 6
If the anterior ratio is greater than 77.2 percent, then
the mandibularanterior tooth material is excessive.
The amount of mandibulartooth material excess is
calculated by using the formula:
MandiIbuIaranterior tooth materiaIexcess = sum of
mandibuIar6 -{sum of max. 6 X77.2}
100

46. If the anterior ratio is less than 77.2 percent,
then the maxillary anterior tooth material is
excessive. The amount of maxillary tooth
material excess is calculated by using the
formula:
Maxillaryanteno..rtoothmatenalexcess=
sumofmax6-{sumofmax.6x100}
77.2

47. CAREY'S ANALYSIS
Thearchlength-toothmaterial
discrepancyisthemaincausefor
mostmalocclusions.This
discrepancycanbecalculatedwith
thehelpofCarey'sanalysis.This
analysisisusuallydoneinthelower
arch.Thesameanalysiswhen
carriedoutintheupperarchis
calledasarchperimeteranalysis.
Methodology;
DeterminationofarchlengthThe
archlengthismeasuredanteriorto
thefirstpermanentmolarusinga
softbrasswire.
Brass wire measurement and actual
mesiodistal widthsof the teeth
mesialto the firstpermanentmolars

48. Thewireisplacedtouchingthe
mesialaspectoflowerfirst
permanentmolar,thenpassed
alongthebuccalcuspsofpremolars,
incisaledgesoftheanteriorsand
finallycontinuedthesamewayup
tothemesialofthefirstmolarof
thecontralateralside.
Brass wire measurement and actual mesiodistal Widths of the
teeth mesial to the first permanent molars

49. Thebrasswireshouldbepassed
alongthecingulumofanteriorteethif
anteriorsareproclinedandalongthe
labialsurfaceifanteriorsare
retroclined.Themesiodistalwidthof
teethanteriortothefirstmolarsare
measuredandsummedupasthe
Totaltoothmaterial.
Thedifferencebetweenthearch
lengthandtheactualmeasuredtooth
materialgivesthediscrepancy.

50. The amount of discrepancy between arch length and
tooth material is calculated.
If the arch length discrepancy is
• 0 to 2.5 mm-Proximal stripping can be carried out
to reduce the minimal tooth material excess.
• 2.5 to 5 mm-Extraction of 2nd premolar is
indicated
• Greater than 5 mm-Extraction of first premolar
is usually required.

51. MOVER'S MIXED DENTITION ANALYSIS
Thepurposeofamixeddentitionanalysisistoevaluatetheamountof
spaceavailableinthearchforsucceedingpermanentteethandnecessary
occlusaladjustments.Manymethodsofmixeddentitionsanalysishave
beensuggested;however,allfallintotwostrategiccategories:
1.Thoseinwhichthesizesoftheuneruptedcuspidsandpremolarsare
estimatedfrommeasurementsoftheradiographicimage,and
2.Thoseinwhichthesizesofthecuspidsandpremolarsarederivedfrom
knowledgeofthesizesofpermanentteethalreadyeruptedinthemouth.
Thecorrelationbetweenthesizesofthemandibularincisorsandthe
combinedsizesofcuspidsandbicuspidsineitherarchishighenoughto
predicttheamountofspacerequiredfortheuneruptedteethduring
spacemanagementprocedures.Themandibularincisorshavebeen
chosenformeasuring,sincetheyeruptintothemouthearlyinthemixed
dentition.Themaxillaryincisorsarenotusedinanyofthepredictive
procedures,sincetheyshowtoomuchvariabilityinsize,andtheir
correlationswithothergroupsofteethareoflowerpredictivevalue.

52. Procedure
a.Procedureinthemandibulararch
1.Measurewiththetooth-measuringgaugeora
pointedBoley'sgauge,thegreatestmesiodistalwidth
ofeachofthefourmandibularincisors.
2.Determinetheamountofspaceneededfor
alignmentoftheincisors.SettheBoley'sgaugetoa
valueequaltothesumofthewidthsoftheleftcentral
incisorandleftlateralincisor.Placeonepointofthe
gaugeatthemidlineofthealveolarcrestbetweenthe
centralincisorsandlettheotherpartliealongtheline
ofthedentalarchontheleftside.

53. Markonthetoothorthecasttheprecisepointwherethe
distalsurfaceofthelateralincisorwillbewhenithasbeen
aligned.Repeatthisprocessfortherightsideofthearch.
3.Computetheamountofspaceavailableafterincisor
alignment.Todothis,measurethedistancefromapoint
markedinthelineofthearchtothemesialsurfaceofthefirst
permanentmolar.Thisdistanceisthespaceavailableforthe
cuspidandtwobicuspidsandforanynecessarymolar
adjustmentaftertheincisorshavebeenaligned.Recordthe
dataforbothsidesonthemixeddentitionanalysisform.

54. 4. Predict the size of the combined widths of the mandibularcuspidand
bicuspids. Prediction of the combined widths of cuspid, first bicuspid,
and second bicuspid is done by use of probability charts. Locate in
the left column of the mandibularchart the value that most nearly
corresponds to the sum of the widths of the four mandibular
incisors. To the right is a row of figures indicating the range of values
for all the cuspidand bicuspids sizes that will be found for incisors of
the indicated size. The value at the 75 percent level of probability is
chosen as the estimate, since it has been found to be the most
practical from a clinical standpoint.
Procedure in the maxillary arch. The procedure is similar to that for
the lower arch, with two exceptions
1. A different probability chart is used for predicting the upper cuspid
and bicuspid sum.
2. Allowance must be made for overjetcorrection when measuring
the space to be occupied by the aligned incisors. Remember that the
width of the lower incisors is used to predict upper cuspidand
bicuspid widths

55. TANAKA AND JOHNSON ANALYSIS
Thepredictionofthesizeofuneruptedcaninesand
prernolarsincontemporaryorthodonticpopulationcan
alsobedonewiththeTanakaandjohnsonanalysis.
TanakaandJohnsondidastudytorepeatMoyers
observationtovalidateitsequationonanewsample.The
possibilityofsecularchangeswithinthepast20yearswas
tobeexaminedandtheyfoundMover'spredictiontableto
beequallyappropriateforcontemporarypopulation.
HowevertheyhavesimplifiedMoyers75percentlevelof
thepredictiontableintoaformula.
Predictedwidthofmaxillarycanineandpremolar
{Misiodistalwidthoffourlowerincisors}+11
2
= estimated width of maxillarycanine and premolar in one
quadrant

56. Predicted width of mandibular canine and
premolar
{Mesiodistal width of four lower incisors} +
2
10.5
= estimated width of canine and premolar in
one quadrant

57. KESLlNG DIAGNOSTIC SET-UP
Keslingintroducedthe
diagnosticset-upwhichis
madefromanextrasetof
trimmedstudymodels.The
diagnostichelpstheclinicianin
treatmentplanningasit
simulatesvarioustooth
movements,whicharetobe
carriedoutinthepatient.The
individualteethalongwith
theiralveolarprocessare
sectionedofffromthemodel
usingasawandreplacedback
inthedesiredfinalposition.

58. The procedure is as follows
Dental cast is related to FMlA
• Constant FMIA = 65°and find
ideal position of mandibular
incisors mesiodistally.
• Align both the lower central
and lateral incisors on the
lower cast at FMTA= 65°
• Mandibularincisors are placed
at right angles to mandibular
plane.
• Canines are the next teeth to
be positioned
Mark the labial position of the
anterior teeth and the canine
width on the artistic portion of
the model
Section individual teeth using a saw-
starting with a vertical cut

59. Firstandsecondpremolarsare
thensetonthemodel.
•Iftheremainingspaceoneach
sideisadequatetoreceivethe
permanentfirstmolars,then
extractionisnotrequired.
•Ifspaceisinadequateand
amountstomorethancanbe
gainedbyuprightingthe
permanentsecondmolars,then
someteethmustberemoved
usuallythefirstpremolar.
Accordingtothelower
incisorstheposterior
teetharesetwithor
without extracting
certainteethdepending
onspacerequirements
Section individual teeth using
a saw

60. When the mandibular
set-up is completed, the
maxillary teeth are cu t
from their base and
repositioned, then
articulated to the
mandibular set-up .
The finished set-up with ideal/proposed changes visible

61. Base the models to be used for Kesling setup
Mark the labial position of the
anterior teeth and the canine
width on the artistic portion of
the model
Section individual teeth
using a saw-starting with a
vertical cut
Section individual teeth using
a saw

62. Section the teeth molar to molar
Mandibular incisors are
placed with an ideal inclination
and position
Accordingtothelower
incisorstheposterior
teetharesetwithor
withoutextractingcertain
teethdependingon
spacerequirements
The maxillary teeth are set
according to the mandibuiar teeth

63. The finished set-up with ideal/proposed changes visible

64. UsesofDiagnosticSet-up
1.Aidsintreatmentplanningasithelpsto
visualizetoothsize-archlengthdiscrepanciesand
determinewhetherextractionisrequiredornot.
2.Theeffectofextractionandtoothmovement
followingit,onocclusioncanbevisualized.
3.Italsoactsasamotivationaltoolasthe
improvementsintoothpositionscanbeshownto
thepatient.

65. THANKS