Study model

STUDY MODELSSTUDY MODELS
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Contents.Contents.
 Introduction.Introduction.
 Diagnostic Aids.Diagnostic Aids.
 Study Models (Defn).Study Models (Defn).
 History.History.
 Purpose of Making Study Models.Purpose of Making Study Models.
 Objectives ofObjectives of IdealIdeal Orthodontic Study Models.Orthodontic Study Models.
 Uses of Study Models.Uses of Study Models.
 Steps in fabrication of Study Models.Steps in fabrication of Study Models.
- Impression Making.- Impression Making.
- Disinfection of Impression.- Disinfection of Impression.
- Taking a Wax Bite.- Taking a Wax Bite.
- Casting.- Casting.
- ABO requirements for trimming Study Models.- ABO requirements for trimming Study Models.
- Trimming Procedure with Finishing.- Trimming Procedure with Finishing.
- Care and Storage of Study Models.- Care and Storage of Study Models.www.indiandentalacademy.comwww.indiandentalacademy.com

 Model AnalysisModel Analysis..
-- PontsPonts Analysis.Analysis.
-- Linder HarthLinder Harth Analysis.Analysis.
-- KorkhausKorkhaus Analysis.Analysis.
- Mixed Dentition Analysis.- Mixed Dentition Analysis.
Moyer's.Moyer's.
Tanaka-Johnston.Tanaka-Johnston.
Huckaba.Huckaba.
Hixon and OldfatherHixon and Oldfather..
-- Sanin-SavaraSanin-Savara Analysis.Analysis.
-- CareysCareys Analysis.Analysis.
-- BoltonsBoltons Analysis.Analysis.
-- Peck and PeckPeck and Peck Analysis.Analysis.
-- HowesHowes Analysis.Analysis. www.indiandentalacademy.comwww.indiandentalacademy.com

 Methods to determine Asymmetry of Arch dimension andMethods to determine Asymmetry of Arch dimension and
Tooth Position.Tooth Position.
- Using Divider.- Using Divider.
- Using Symmetrograph.- Using Symmetrograph.
 Diagnostic Set Up.Diagnostic Set Up.
 Digital Study Models.Digital Study Models.
- e-models.- e-models.
- Ora-scanner.- Ora-scanner.
- OrthoCAD.- OrthoCAD.
 References.References.

INTRODUCTION.INTRODUCTION.

Diagnostic Aids.Diagnostic Aids.
 Comprehensive orthodontic diagnosis isComprehensive orthodontic diagnosis is
established by use of certain clinicalestablished by use of certain clinical
implements calledimplements called DIAGNOSTIC AIDS.DIAGNOSTIC AIDS.
 They are of two types:They are of two types:
 1) ESSENTIAL DIAGNOSTIC AIDS1) ESSENTIAL DIAGNOSTIC AIDS
 2)SUPPLEMENTAL DIAGNOSTIC AIDS.2)SUPPLEMENTAL DIAGNOSTIC AIDS.

ESSENTIAL DIAGNOSTICESSENTIAL DIAGNOSTIC
AIDSAIDS
SUPPLEMENTALSUPPLEMENTAL
DIAGNOSTIC AIDSDIAGNOSTIC AIDS
1)CASE HISTORY.1)CASE HISTORY. 1)SPECIALIZED RADIOGRAPHS.1)SPECIALIZED RADIOGRAPHS.
OPGOPG
LATERALLATERAL
PA VIEWPA VIEW
2)CLINICAL EXAMINATION.2)CLINICAL EXAMINATION. 2)ELECTROMYOGRAPHY.2)ELECTROMYOGRAPHY.
3)STUDY MODELS.3)STUDY MODELS. 3)HAND-WRIST RADIOGRAPHS.3)HAND-WRIST RADIOGRAPHS.
4)RADIOGRAPHS.4)RADIOGRAPHS.
PERIAPICALPERIAPICAL
BITE-WINGBITE-WING
PANORAMICPANORAMIC
4)ENDOCRINE TESTS.4)ENDOCRINE TESTS.
5)FACIAL PHOTOGRAPHS.5)FACIAL PHOTOGRAPHS. 5)BMR ESTIMATION.5)BMR ESTIMATION.
6)OCCLUSOGRAMS.6)OCCLUSOGRAMS.

STUDY MODELS.STUDY MODELS.
 Orthodontic study models are essentialOrthodontic study models are essential
diagnostic records, which are accurate plasterdiagnostic records, which are accurate plaster
reproductions of the teeth and their supportingreproductions of the teeth and their supporting
soft tissues and which help to study thesoft tissues and which help to study the
occlusion and dentition from all the threeocclusion and dentition from all the three
dimensions.dimensions.

 ““No matter how astute you are, no matter howNo matter how astute you are, no matter how
carefully you look into your dental mirror,no mattercarefully you look into your dental mirror,no matter
how you bend your head to get a better view of thehow you bend your head to get a better view of the
patients mouth as he sits in the dental chair with hispatients mouth as he sits in the dental chair with his
jaws spread apart, you cannot achieve the degree ofjaws spread apart, you cannot achieve the degree of
accuracy and attain the completeness that an analysisaccuracy and attain the completeness that an analysis
of study casts will permit. An additional “plus” isof study casts will permit. An additional “plus” is
that you have a time linked, a longitudinal ,threethat you have a time linked, a longitudinal ,three
dimensional record that establishes the status of thedimensional record that establishes the status of the
teeth and investing tissues at that particular time.”teeth and investing tissues at that particular time.”
- GRABER.- GRABER.www.indiandentalacademy.comwww.indiandentalacademy.com

History.History.
 PFAFFPFAFF IN 1756 FIRST TIME OBTAINED AIN 1756 FIRST TIME OBTAINED A
NEGATIVE PRODUCED FROM WAX ANDNEGATIVE PRODUCED FROM WAX AND
FROM IT A POSITIVE MODEL WASFROM IT A POSITIVE MODEL WAS
OBTAINED THROUGH PLASTEROBTAINED THROUGH PLASTER
CASTING.CASTING.

Purpose of Making StudyPurpose of Making Study
Models.Models.
 1) Invaluable in planning treatment as they are three-1) Invaluable in planning treatment as they are three-
dimensional records of patients dentition.dimensional records of patients dentition.
 2)Occlusion can be visualized from all aspects.2)Occlusion can be visualized from all aspects.
 3) Provide a permanent record of the intermaxillary3) Provide a permanent record of the intermaxillary
relationships and the occlusion at the start ofrelationships and the occlusion at the start of
therapy;this is necessary for medico-legaltherapy;this is necessary for medico-legal
considerations.considerations.
 4) Help us to monitor changes taking place during4) Help us to monitor changes taking place during
tooth movements.tooth movements.

Contd.Contd.
 5)Helps to motivate the patients as they can visualize5)Helps to motivate the patients as they can visualize
the treatment progress.the treatment progress.
 6)They are needed for comparison purposes at the6)They are needed for comparison purposes at the
end of treatment and act as a reference for postend of treatment and act as a reference for post
treatment changes.treatment changes.
 7) Serve as a reminder for the parent and the patient7) Serve as a reminder for the parent and the patient
of the condition present at the start of treatment.of the condition present at the start of treatment.
 8)In case the patient has to be transferred to another8)In case the patient has to be transferred to another
clinician ,study models are an important record.clinician ,study models are an important record.

Objectives ofObjectives of IdealIdeal OrthodonticOrthodontic
Study Models.Study Models.
 1)Models accurately reproduce the teeth and their1)Models accurately reproduce the teeth and their
surrounding soft tissues. Soft tissues must not besurrounding soft tissues. Soft tissues must not be
altered.altered.
 2)Models are to be trimmed so that they are2)Models are to be trimmed so that they are
symmetrical and pleasing to the eye and so that ansymmetrical and pleasing to the eye and so that an
asymmetrical arch form can be easily recognized.asymmetrical arch form can be easily recognized.
 3)Models are to be trimmed in such a way that the3)Models are to be trimmed in such a way that the
dental occlusion shows by setting the models on theirdental occlusion shows by setting the models on their
backs.backs.
 4)Models are to be trimmed so that they meet the4)Models are to be trimmed so that they meet the
measurements and angles as proposed for trimmingmeasurements and angles as proposed for trimming
them.them.

Contd.Contd.
 5)Models are to have a clean, smooth, bubble5)Models are to have a clean, smooth, bubble
free surfaces with sharp angles where the cutsfree surfaces with sharp angles where the cuts
meet.meet.
 6)The finished models will be treated with a6)The finished models will be treated with a
soap solution to give it a glassy, mar-proofsoap solution to give it a glassy, mar-proof
finish.finish.

Uses of Study Models.Uses of Study Models.
 1)To assess and record the dental anatomy.1)To assess and record the dental anatomy.
 2)To assess and record the intercuspation.2)To assess and record the intercuspation.
 3)To assess and record the arch form.3)To assess and record the arch form.
 4)To carry out various space analysis.4)To carry out various space analysis.
 5)To assess and record the curves of occlusion.5)To assess and record the curves of occlusion.
 6)To evaluate occlusion with the aid of articulators.6)To evaluate occlusion with the aid of articulators.
 7)To measure progress during treatment.7)To measure progress during treatment.
 8)To detect abnormalities. (eg: localized8)To detect abnormalities. (eg: localized
enlargements,distortion of arch form)enlargements,distortion of arch form)
 9)To provide a record before ,immediately after, and9)To provide a record before ,immediately after, and
several years following treatment for the purpose ofseveral years following treatment for the purpose of
studying treatment procedures.studying treatment procedures.www.indiandentalacademy.comwww.indiandentalacademy.com

Parts of the Study Models.Parts of the Study Models.
 ANATOMIC portion.ANATOMIC portion.
 ARTISTIC portion.ARTISTIC portion.

Anatomic portion.Anatomic portion.
 Anatomic portion is that part of the studyAnatomic portion is that part of the study
model which is the actual impression of themodel which is the actual impression of the
dental arch and its surrounding structures.dental arch and its surrounding structures.
 Usually made of stone plaster.Usually made of stone plaster.
 Must be preserved while trimming the model.Must be preserved while trimming the model.

Artistic portion.Artistic portion.
 The artistic portion of study model is a plasterThe artistic portion of study model is a plaster
base that supports the anatomic portion.base that supports the anatomic portion.
 Helps in depicting the actual orientation andHelps in depicting the actual orientation and
the occlusion of study models.the occlusion of study models.
 Gives a pleasing and symmetrical appearanceGives a pleasing and symmetrical appearance
to the models.to the models.

In a well fabricated set of study modelsIn a well fabricated set of study models
the ratio of the anatomic portion tothe ratio of the anatomic portion to
artistic portion should be 3:1.artistic portion should be 3:1.

Steps in construction of studySteps in construction of study
models.models.
 Impression making.Impression making.
 Taking a wax bite.Taking a wax bite.
 Disinfection of the impression.Disinfection of the impression.
 Casting the impression.Casting the impression.
 Basing and trimming.Basing and trimming.
 Finishing and polishing.Finishing and polishing.
 Care of the study models.Care of the study models.

Impression making.Impression making.

Impression making.Impression making.
 Irreversible hydrocolloids(Irreversible hydrocolloids(alginatealginate) are widely used.) are widely used.
 Advantages of alginate:Advantages of alginate:
1)easy to manipulate.1)easy to manipulate.
2)comfortable for the patient.2)comfortable for the patient.
3)relatively inexpensive as it does not require elaborate3)relatively inexpensive as it does not require elaborate
equipment.equipment.
4)has pleasant taste.4)has pleasant taste.
5)able to displace blood and saliva.5)able to displace blood and saliva.
6)they are hydrophilic.6)they are hydrophilic.
7)they are compatible with stone so it is easy to pour and7)they are compatible with stone so it is easy to pour and
retrieve the cast.retrieve the cast.
8)they can be used with stock trays.8)they can be used with stock trays.

Orthodontic impression trays.Orthodontic impression trays.
 Orthodontic trays are used as their rim in labialOrthodontic trays are used as their rim in labial
region is about ¾ inch (20 mm) and their edges areregion is about ¾ inch (20 mm) and their edges are
beaded.beaded.
 Strips of soft utility wax or mortem can be added toStrips of soft utility wax or mortem can be added to
tray periphery.tray periphery.

Disinfecting the impression.Disinfecting the impression.
 First rinse with water.First rinse with water.
 Immerse it in a disinfectant solution approvedImmerse it in a disinfectant solution approved
by O.S.H.A such as Biocide or Chlorhexidine.by O.S.H.A such as Biocide or Chlorhexidine.
 Be sure to rinse it again with water to removeBe sure to rinse it again with water to remove
the residual disinfectant solution.the residual disinfectant solution.

Taking a wax bite.Taking a wax bite.
 It should always be taken as it helps the dentistIt should always be taken as it helps the dentist
to relate the upper and lower casts into relate the upper and lower casts in
occlusion.occlusion.
 Also helps to hold the casts flushed with eachAlso helps to hold the casts flushed with each
other while trimming.other while trimming.

wax bite.JPG
White and Gardiner:White and Gardiner:

Taking a wax bite.Taking a wax bite.
 Phillip Adams:Phillip Adams:
Wax bite should consist of only a bar ofWax bite should consist of only a bar of
moderately softened wax across the premolarmoderately softened wax across the premolar
region.region.

Graber:Graber:
Two layers of soft base-plate wax roughlyTwo layers of soft base-plate wax roughly
shaped to arch form and warmed in water mayshaped to arch form and warmed in water may
be used.be used.

Casting the model.Casting the model.

Casting the model.Casting the model.
 The models may be cast inThe models may be cast in
Plain dental plaster.Plain dental plaster.
Stone plaster.Stone plaster.
Mixture of plain plaster and stone plaster.Mixture of plain plaster and stone plaster.
Or the anatomic portion may be cast in stoneOr the anatomic portion may be cast in stone
plaster and and bases in plain plaster.plaster and and bases in plain plaster.

RUBBER MOULD BASERUBBER MOULD BASE
FORMERS.FORMERS.

Cross Section of Plaster Casts in RubberCross Section of Plaster Casts in Rubber
Mould Base Formers:Mould Base Formers:
 Occlusal plane shouldOcclusal plane should
be parallel with top andbe parallel with top and
bottom cast surfaces.bottom cast surfaces.
 The back surfaces of theThe back surfaces of the
casts should be relatedcasts should be related
in exactly the samein exactly the same
plane ,perpendicular toplane ,perpendicular to
top and bottom casttop and bottom cast
surfaces.surfaces.

Broussard cast former.Broussard cast former.
(Rocky Mountain Dental Products Co.)(Rocky Mountain Dental Products Co.)

STUDY MODELSTUDY MODEL
TRIMMING.TRIMMING. (Lawson)(Lawson)

American Board of OrthodonticsAmerican Board of Orthodontics
requirements for study models.requirements for study models.
(American Board of Orthodontics(American Board of Orthodontics: Specific Instructions for: Specific Instructions for
Candidates,Candidates, St Louis,1998, The Board)St Louis,1998, The Board)

American Board of OrthodonticsAmerican Board of Orthodontics
requirements for study modelsrequirements for study models

Study model trimming…Study model trimming…
 Accurate detailedAccurate detailed
impressions are essential toimpressions are essential to
the production of highthe production of high
quality study models.quality study models.
Before the mandibular castBefore the mandibular cast
is poured the tongue spaceis poured the tongue space
must be filled in withmust be filled in with
alginatealginate..

 Casting material is carefullyCasting material is carefully
proportioned according toproportioned according to
the manufacturersthe manufacturers
instructions.generally , theinstructions.generally , the
ratio of 30 ml of water toratio of 30 ml of water to
100g of stone will be100g of stone will be
sufficient to pour onesufficient to pour one
model. This should bemodel. This should be
spatulated for 20 to 30spatulated for 20 to 30
seconds by a vacuum mixerseconds by a vacuum mixer
to produce a smooth, dense,to produce a smooth, dense,
bubble free mix.bubble free mix.

 Vibrate the mix into theVibrate the mix into the
impression so that it flowsimpression so that it flows
slowly from one posteriorslowly from one posterior
end around to the anteriorend around to the anterior
and then the other posteriorand then the other posterior
end. Avoid incorporating airend. Avoid incorporating air
bubbles. Fill its base in abubbles. Fill its base in a
like manner. Carefullylike manner. Carefully
invert the impression ontoinvert the impression onto
its base and add stone to theits base and add stone to the
heel areas so that theyheel areas so that they
extend smoothly into theextend smoothly into the
model base surface. Repeatmodel base surface. Repeat
this procedure for thethis procedure for the
opposing model.opposing model.

 Cast are allowed to dryCast are allowed to dry
thoroughly .thoroughly .
 Now one electric plaster-Now one electric plaster-
trimming machine with atrimming machine with a
medium grit,carborundummedium grit,carborundum
wheel,grit no. 60 is used forwheel,grit no. 60 is used for
trimming.trimming.
 Trimmer has dual wheels.Trimmer has dual wheels.

 A template(or degreeA template(or degree
plate) on the modelplate) on the model
trimmer platform istrimmer platform is
used as a reference forused as a reference for
holding the casts at aholding the casts at a
proper angle whileproper angle while
trimming.trimming.

 In addition to no.600In addition to no.600
wet and dry sandwet and dry sand
paper,small and mediumpaper,small and medium
scrapers,lab knife andscrapers,lab knife and
some special equipmentsome special equipment
will be used.will be used.
 Angle guide.Angle guide.
 Squaring tool.Squaring tool.

 Allow the models to dryAllow the models to dry
for one hour afterfor one hour after
pouring.remove the basepouring.remove the base
formers and then theformers and then the
impression.impression.
 Inspect.Inspect.

 The casts are soaked inThe casts are soaked in
water for atleast 10water for atleast 10
minutes before they areminutes before they are
trimmed. Never attempttrimmed. Never attempt
to trim a dry model.to trim a dry model.

 Trim the maxillary cast first.Trim the maxillary cast first.
Remove excess stone fromRemove excess stone from
the heel areas so that thethe heel areas so that the
incisors and terminal molarincisors and terminal molar
cusp tips will be able tocusp tips will be able to
touch the flat plane of thetouch the flat plane of the
squaring toolsquaring tool
simultaneously.simultaneously.

 Position the occlusalPosition the occlusal
plane against theplane against the
squaring tool .squaring tool .
 Check to be sure properCheck to be sure proper
contact is being made.contact is being made.

 Turn on the water supply beforeTurn on the water supply before
switching on the model trimmer.switching on the model trimmer.
 While holding the occlusal planeWhile holding the occlusal plane
of the cast firmly against theof the cast firmly against the
squaring tool, slide the whole unitsquaring tool, slide the whole unit
toward the rough cut wheel. Trimtoward the rough cut wheel. Trim
away the excess base material soaway the excess base material so
that the remaining base portion isthat the remaining base portion is
about one third the total castabout one third the total cast
height.height.

 Draw a line over theDraw a line over the
median palatine raphe.median palatine raphe.

 A perpendicular line isA perpendicular line is
drawn, about ½ inch distaldrawn, about ½ inch distal
to the hamular notches.trimto the hamular notches.trim
the back of cast to this line.the back of cast to this line.
 The back of the cast formsThe back of the cast forms
right angles with the medianright angles with the median
palatine raphe.palatine raphe.

 The buccal segments areThe buccal segments are
trimmed at a 70 degreetrimmed at a 70 degree
angle to the back of the cast.angle to the back of the cast.
 To accomplish this, rotateTo accomplish this, rotate
the degree plate and slidethe degree plate and slide
the angle guide into place.the angle guide into place.
 Press the cast against thePress the cast against the
angle guide and trim toangle guide and trim to
about 5mm from the buccalabout 5mm from the buccal
surfaces of teethsurfaces of teeth
 Reset the degree plate toReset the degree plate to
trim the other side.trim the other side.

 Use even, steadyUse even, steady
pressure against thepressure against the
wheel,but let the modelwheel,but let the model
trimmer do the work.trimmer do the work.
 Both buccal segmentsBoth buccal segments
have been trimmed at ahave been trimmed at a
70 degree angle.70 degree angle.

 Change the degree plateChange the degree plate
to indicate a 30-degreeto indicate a 30-degree
setting and repositionsetting and reposition
the angle guide.the angle guide.
 Trim the maxillaryTrim the maxillary
anterior portion.anterior portion.
 Carefully preserve theCarefully preserve the
mucobuccal fold area.mucobuccal fold area.

 Both anterior angles areBoth anterior angles are
complete.complete.
 Note that each angleNote that each angle
begins at a point at thebegins at a point at the
middle of the canine.middle of the canine.
 The two angles intersectThe two angles intersect
at a point that is anat a point that is an
extension of the medianextension of the median
palatine raphe line.palatine raphe line.

 The maxillary posteriorThe maxillary posterior
segments are trimmed atsegments are trimmed at
130-135 degrees angle.130-135 degrees angle.
 They should be about ½They should be about ½
to 5/8 inches wide.to 5/8 inches wide.

 Occlude the maxillary andOcclude the maxillary and
mandibular casts, trimmingmandibular casts, trimming
excess stone from theexcess stone from the
mandibular heels if needed.mandibular heels if needed.
 The wax bite registrationThe wax bite registration
wafer should be in placewafer should be in place
when trimming occludedwhen trimming occluded
models because themodels because the
vibration may abrade thevibration may abrade the
tooth surfaces.tooth surfaces.

Use the squaring tool toUse the squaring tool to
trim the mandibulartrim the mandibular
base so that it is parallelbase so that it is parallel
to the maxillary base.to the maxillary base.
The height of the baseThe height of the base
should be about 1/3 rdshould be about 1/3 rd
the total height of thethe total height of the
cast.cast.

 With the casts occluded,With the casts occluded,
trim the back of thetrim the back of the
mandibular cast so that it ismandibular cast so that it is
parallel and flush with theparallel and flush with the
maxillary cast.maxillary cast.
 This will allow the casts toThis will allow the casts to
remain in occlusion whenremain in occlusion when
placed on their backs on aplaced on their backs on a
flat surface.flat surface.

 The backs of theThe backs of the
maxillary andmaxillary and
mandibular casts aremandibular casts are
trimmed evenly.trimmed evenly.
 The mandibularThe mandibular
posterior cornerposterior corner
segments are trimmed tosegments are trimmed to
130-135 degree130-135 degree
angles,flushed with theirangles,flushed with their
maxillary counterparts.maxillary counterparts.

 The buccal segments areThe buccal segments are
trimmed at 65-degreetrimmed at 65-degree
angles to the deepestangles to the deepest
part of the buccalpart of the buccal
vestibule.vestibule.
 Do not trim closer thanDo not trim closer than
5mm from the buccal5mm from the buccal
surfaces of the teeth.surfaces of the teeth.

 Make a semicircularMake a semicircular
mark from the center ofmark from the center of
one canine to the centerone canine to the center
of the other. This willof the other. This will
indicate the anteriorindicate the anterior
trim line.trim line.
 It should be no closerIt should be no closer
than 5mm from thethan 5mm from the
labial tooth surfaces.labial tooth surfaces.

 Carefully trim theCarefully trim the
anterior segment to theanterior segment to the
mark.mark.
 It should have aIt should have a
smooth,symmetricalsmooth,symmetrical
shape.shape.

 Gently carve any excessGently carve any excess
material from sulcusmaterial from sulcus
areas.areas.
 Use a laboratory knifeUse a laboratory knife
and scraper to removeand scraper to remove
blebs and define detail.blebs and define detail.

 Use extra-fine no.600Use extra-fine no.600
sandpaper to smoothsandpaper to smooth
sulcus areas by hand.sulcus areas by hand.
 The tongue area mustThe tongue area must
also be sanded smooth.also be sanded smooth.

 Use the fine sandingUse the fine sanding
wheel on the modelwheel on the model
trimmer to smoothtrimmer to smooth
scratches left by thescratches left by the
rough wheel.rough wheel.
 Fill any small voids inFill any small voids in
the models with a thinthe models with a thin
mix of orthodonticmix of orthodontic
stone.stone.
 Lightly sand again ifLightly sand again if
necessary.necessary.

 Allow the models to dryAllow the models to dry
for 24 hours before puttingfor 24 hours before putting
them in finishing soapthem in finishing soap
solution. They should besolution. They should be
soaked for about 20soaked for about 20
minutes but not more thanminutes but not more than
30, or the models will30, or the models will
dissolve.dissolve.
 Rinse off the excess soapRinse off the excess soap
and buff with a soft cottonand buff with a soft cotton
cloth.cloth.

 After the models haveAfter the models have
dried they must bedried they must be
labelled.labelled.
 Use an indelible markerUse an indelible marker
to print the patientsto print the patients
name and the date thename and the date the
impressions were taken.impressions were taken.

 The study model set isThe study model set is
complete.complete.
 Note the sharp,Note the sharp,
symmetric angles.symmetric angles.
 The surfaces are sandedThe surfaces are sanded
and polished to aand polished to a
smooth,attractive luster.smooth,attractive luster.

 The base of each modelThe base of each model
is parallel and flushis parallel and flush
with the base of thewith the base of the
other.other.
 The set will remain inThe set will remain in
occlusion when restingocclusion when resting
on the heels, or on theon the heels, or on the
right or left posteriorright or left posterior
corners.corners.

Cast trimming to indicate theCast trimming to indicate the
occlusal plane relationships.occlusal plane relationships.
 Gnathostatic technique.Gnathostatic technique.
 Simon in 1926.Simon in 1926.
 Reproduces the inclination of the occlusalReproduces the inclination of the occlusal
plane with reference to FH-plane.plane with reference to FH-plane.

Care of study modelsCare of study models.. (White and(White and
Gardiner)Gardiner)
 Record casts should be kept in boxes holdingRecord casts should be kept in boxes holding
5-6 sets of models,each pair held together by a5-6 sets of models,each pair held together by a
light elastic band.light elastic band.
 A square of thin plastic foam should be keptA square of thin plastic foam should be kept
between the occlusal surfaces of the teeth.between the occlusal surfaces of the teeth.
 The wax bite should not be left between theThe wax bite should not be left between the
teeth, however it should be stored as it will beteeth, however it should be stored as it will be
of help in finding the occlusal relationship at aof help in finding the occlusal relationship at a
later date.later date.

Orthodontic model boxes.Orthodontic model boxes.
((J. of Cl. OrthoJ. of Cl. Ortho.,1991)..,1991).
 Orthodontic model boxes can be used for systematicOrthodontic model boxes can be used for systematic
storage, identification and coding of study models.storage, identification and coding of study models.
 BARGER model boxBARGER model box: lid style. Stores 8 models per: lid style. Stores 8 models per
box.box.
 FUNT model boxFUNT model box: drawer style. Stores 4 models per: drawer style. Stores 4 models per
drawer, 8 models per box.drawer, 8 models per box.
 ARTICULATED model boxARTICULATED model box: drawer style. For tall: drawer style. For tall
mounted models.mounted models.
 Space maintainer lab, Indiana.Space maintainer lab, Indiana.
North Western paper box company,Washington.North Western paper box company,Washington.
The Board foot, Texas: Model display cabinets.The Board foot, Texas: Model display cabinets.

Model Analysis.Model Analysis.

PontsPonts analysis.analysis.
 In 1909,In 1909, PontPont devised a method ofdevised a method of
predetermining an “ideal”arch width based onpredetermining an “ideal”arch width based on
the mesiodistal widths of the crowns of thethe mesiodistal widths of the crowns of the
maxillary incisors.maxillary incisors.
 PontPont suggested that the ratio of combinedsuggested that the ratio of combined
incisor to transverse arch width was ideallyincisor to transverse arch width was ideally
0.8 in the bicuspid area and 0.64 in the first0.8 in the bicuspid area and 0.64 in the first
molar area.molar area.

1)Sum of mesio-distal widths of incisors.1)Sum of mesio-distal widths of incisors.
2)Measured premolar value.2)Measured premolar value.
3)Measured molar value.3)Measured molar value.

PontsPonts analysis, contd..analysis, contd..
 Expected arch width at premolar region:Expected arch width at premolar region:
sum of incisorssum of incisors * 100* 100
8080
Expected arch width at molar region:Expected arch width at molar region:
sum of incisorssum of incisors * 100* 100
6464

PontsPonts analysis contd..analysis contd..
 PontsPonts also suggested that maxillary archalso suggested that maxillary arch
should be expanded 1-2mm more duringshould be expanded 1-2mm more during
treatment than his value to allow for relapse.treatment than his value to allow for relapse.
 Thus, amount of expansion that can be doneThus, amount of expansion that can be done
on molar and premolar region is estimated.on molar and premolar region is estimated.

Drawbacks ofDrawbacks of PontsPonts analysis:analysis:
 Researchers at University of WashingtonResearchers at University of Washington (Dent(Dent
Clin North Am 1978)Clin North Am 1978) found very poor correlationfound very poor correlation
between combined maxillary incisor widthsbetween combined maxillary incisor widths
and the ultimate arch width in the bicuspid andand the ultimate arch width in the bicuspid and
molar areas.molar areas.
 Does not take skeletal mal-relation intoDoes not take skeletal mal-relation into
consideration.consideration.
 Analysis is derived solely from casts of FrenchAnalysis is derived solely from casts of French
population,so it can’t be applied globally.population,so it can’t be applied globally.

Linder HarthLinder Harth index.index.
 Similar toSimilar to PontsPonts analysis.analysis.
 Variation in formula to determine the expected archVariation in formula to determine the expected arch
widths at molar and premolar regions.widths at molar and premolar regions.
 Expected arch widths at premolar region:Expected arch widths at premolar region:
Sum of incisorsSum of incisors * 100.* 100.
8585
Expected arch width at molar region:Expected arch width at molar region:
Sum of incisorsSum of incisors * 100.* 100.
6565

KorkhausKorkhaus analysis.analysis.
 It makes use ofIt makes use of Linder HarthLinder Harth
formula to determine the idealformula to determine the ideal
arch width in the premolar andarch width in the premolar and
molar region.molar region.
 A measurement is also made fromA measurement is also made from
the midpoint of inter-premolarthe midpoint of inter-premolar
line to a point in between twoline to a point in between two
maxillary incisors.maxillary incisors.
 According toAccording to KorkhausKorkhaus “For a“For a
given width of upper incisors, agiven width of upper incisors, a
specific value of the distance betweenspecific value of the distance between
the midpoint of inter-premolar line tothe midpoint of inter-premolar line to
the point between the two maxillarythe point between the two maxillary
incisors should exist.”incisors should exist.”
 An increase in this measurementAn increase in this measurement
indicates proclined upper incisorsindicates proclined upper incisors
while a decrease in this valuewhile a decrease in this value
indicate retroclined upperindicate retroclined upper
incisorsincisors..

Sanin-SavaraSanin-Savara tooth size analysis.tooth size analysis.
((Am J OrthodAm J Orthod 1971)1971)
 Scholars at University of Oregon devised aScholars at University of Oregon devised a
simple and indigenous procedure tosimple and indigenous procedure to identifyidentify
individual and group tooth sizeindividual and group tooth size
disharmoniesdisharmonies..
 It makes use of precise mesio-distalIt makes use of precise mesio-distal
measurements of the crown size of eachmeasurements of the crown size of each
tooth,appropriate tables of tooth sizetooth,appropriate tables of tooth size
distribution in the population, and a chart fordistribution in the population, and a chart for
plotting the patients measurements.plotting the patients measurements.

HowesHowes analysis.analysis.
((Am J OrthodAm J Orthod 1954,1954, Am J OrthodAm J Orthod 1960)1960)
 Ashley HoweAshley Howe devised the formula to determinedevised the formula to determine
whether the apical bases could accommodate thewhether the apical bases could accommodate the
patients teeth.patients teeth.
 He considered tooth crowding to be due to deficiencyHe considered tooth crowding to be due to deficiency
in arch width rather than arch length.in arch width rather than arch length.
 Determination of total tooth material.(TM)Determination of total tooth material.(TM)
 Determination of premolar diameter(PMD)Determination of premolar diameter(PMD)
 Determination of premolar basal archDetermination of premolar basal arch
width(PMBAW)width(PMBAW)
 Determination of BAL.Determination of BAL.

HOWESHOWES ANALYSIS.ANALYSIS.

HowesHowes analysis, contd..analysis, contd..
 If PMBAW is greater than PMD, arch expansion is possible.If PMBAW is greater than PMD, arch expansion is possible.
 HowesHowes believed that the PMBAW should equal approximatelybelieved that the PMBAW should equal approximately
44%of the TTM if it is sufficiently large to accommodate all44%of the TTM if it is sufficiently large to accommodate all
the teeth.the teeth.
 When the ratio between PMBAW and TTM is less thanWhen the ratio between PMBAW and TTM is less than
37%,37%,HoweHowe considered this to be a basal arch deficiencyconsidered this to be a basal arch deficiency
necessitating extraction of premolars.necessitating extraction of premolars.
 HowesHowes analysis is useful in planning treatment of problemsanalysis is useful in planning treatment of problems
with suspected apical base deficiencies and deciding whetherwith suspected apical base deficiencies and deciding whether
to;to;
1)extract teeth.1)extract teeth.
2)widen the dental arch, or2)widen the dental arch, or
3)expand rapidly the palate.3)expand rapidly the palate.

BoltonBolton tooth ratio analysis.tooth ratio analysis.
((Angle OrthodAngle Orthod 1958,1958, Am J OrthodAm J Orthod 1962)1962)
 BoltonBolton studied the interarch effects of discrepanciesstudied the interarch effects of discrepancies
in tooth size to devise a procedure for determining thein tooth size to devise a procedure for determining the
ratio of total mandibular versus maxillary tooth sizeratio of total mandibular versus maxillary tooth size
and anterior mandibular versus maxillary tooth size.and anterior mandibular versus maxillary tooth size.
 Study of these ratios help inStudy of these ratios help in
1)estimating the overjet and overbite relationships that1)estimating the overjet and overbite relationships that
will likely obtain after the treatment is finished.will likely obtain after the treatment is finished.
2)estimating the effects of contemplated extractions2)estimating the effects of contemplated extractions
on posterior occlusion and incisor relationships,andon posterior occlusion and incisor relationships,and
3)the identification of occlusal misfit produced by3)the identification of occlusal misfit produced by
interarch tooth size incompatibilities.interarch tooth size incompatibilities.

Procedure.Procedure.
 Sum of mandibular 12.Sum of mandibular 12.
 Sum of maxillary 12.Sum of maxillary 12.
 Sum of mandibular 6.Sum of mandibular 6.
 Sum of maxillary 6.Sum of maxillary 6.
are measured.are measured.

Determination of Overall ratio:Determination of Overall ratio:
 According toAccording to BoltonBolton, a mean ratio of 91.3 will, a mean ratio of 91.3 will
result in ideal overjet-overbite relationships, asresult in ideal overjet-overbite relationships, as
well as posterior occlusion.well as posterior occlusion.
 Overall ratio=Overall ratio=sum of mandibular12*100.sum of mandibular12*100.
sum of maxillary12.sum of maxillary12.
If it is less than 91.3%,it indicates maxillaryIf it is less than 91.3%,it indicates maxillary
tooth material excess and it indicatestooth material excess and it indicates
mandibular tooth material excess if it is moremandibular tooth material excess if it is more
than 91.3%.than 91.3%.

Contd..Contd..
 Amount of maxillary excess:Amount of maxillary excess:
sum of maxillary12-sum of maxillary12- sum of mand.12*100.sum of mand.12*100.
91.3.91.3.
Amount of mandibular excess:Amount of mandibular excess:
sum of mandib.12-sum of mandib.12- sum of max.12*100.sum of max.12*100.
91.3.91.3.

Contd..Contd..
 A similar ratio is computed for six anterior teeth.A similar ratio is computed for six anterior teeth.
 An anterior ratio of 77.2 will provide ideal overjetAn anterior ratio of 77.2 will provide ideal overjet
and overbite relationshipsand overbite relationships ifif the angulations ofthe angulations of
incisors are correct andincisors are correct and ifif the labio-lingual thicknessthe labio-lingual thickness
of the incisal edge is not excessive.of the incisal edge is not excessive.
 If anterior ratio exceeds 77.2,there is excessiveIf anterior ratio exceeds 77.2,there is excessive
mandibular tooth material and if it is less thanmandibular tooth material and if it is less than
77.2,there is excess maxillary tooth material.77.2,there is excess maxillary tooth material.
 BoltonBolton analysis predictions do not take into accountanalysis predictions do not take into account
the sexual dimorphism in maxillary cuspid widths.the sexual dimorphism in maxillary cuspid widths.

CareysCareys analysisanalysis
..
 Determination of arch length.Determination of arch length.
 Determination of tooth material.Determination of tooth material.
 Determination of discrepancy.Determination of discrepancy.
 Inference;Inference;
1)If discrepancy is 0-1)If discrepancy is 0-
2.5mm,proximal stripping.2.5mm,proximal stripping.
2)If discrepancy is between 2.5-52)If discrepancy is between 2.5-5
mm,extract the second premolars.mm,extract the second premolars.
3)If discrepancy is more than 5mm,3)If discrepancy is more than 5mm,
extract first premolarsextract first premolars..

Peck and PeckPeck and Peck Index.Index.
 It is done in lower arch.It is done in lower arch.
 Peck and PeckPeck and Peck suggested certain clinicalsuggested certain clinical
guidelines on the basis of observation thatguidelines on the basis of observation that
:Persons with ideal incisal arrangement had:Persons with ideal incisal arrangement had
smaller mesio-distal width and comparativelysmaller mesio-distal width and comparatively
larger labio-lingual width than in persons withlarger labio-lingual width than in persons with
incisal crowding.incisal crowding.

Procedure:Procedure:
 Measure the mesio-distal width(M.D) and the labio-Measure the mesio-distal width(M.D) and the labio-
lingual width(L.D) of each of mandibular incisors.lingual width(L.D) of each of mandibular incisors.
 Calculate the proportion of the mesiodistal width ofCalculate the proportion of the mesiodistal width of
each tooth to the labio-lingual width of the tooth byeach tooth to the labio-lingual width of the tooth by
using the formula:using the formula:
M.D.M.D. *100.*100.
L.L/F.LL.L/F.L
 Mean value for lower central incisor should be 88-Mean value for lower central incisor should be 88-
92%.92%.
 Mean value for lower lateral incisor should be 90-Mean value for lower lateral incisor should be 90-
95%.95%.

Inference.Inference.
 If the value for a given case is more than theIf the value for a given case is more than the
mean value then, mesio-distal width of themean value then, mesio-distal width of the
tooth is more than the labio-lingual width andtooth is more than the labio-lingual width and
hence proximal stripping is indicated in suchhence proximal stripping is indicated in such
cases.cases.

Mixed Dentition Analysis.Mixed Dentition Analysis.
 The purpose of mixed dentition analysis is to evaluateThe purpose of mixed dentition analysis is to evaluate
the amount of space available in the arch forthe amount of space available in the arch for
succeeding permanent teeth and necessary occlusalsucceeding permanent teeth and necessary occlusal
adjustments.adjustments.
 This analysis helps one estimate the amount ofThis analysis helps one estimate the amount of
spacing or crowding which would exist for the patientspacing or crowding which would exist for the patient
if all the primary teeth were replaced by theirif all the primary teeth were replaced by their
successors.successors.

Contd..Contd..
 Methods fall in two categories:Methods fall in two categories:
1)sizes of un-erupted cuspids and premolars are estimated from1)sizes of un-erupted cuspids and premolars are estimated from
measurements of the radiographic image.measurements of the radiographic image.
2)sizes of un-erupted cuspids and premolars are derived from2)sizes of un-erupted cuspids and premolars are derived from
knowledge of the sizes of permanent teeth already erupted inknowledge of the sizes of permanent teeth already erupted in
the mouth.the mouth.
 Moyer'sMoyer's advocated type 2 because:advocated type 2 because:
1)it has minimal systematic error and range of such errors is1)it has minimal systematic error and range of such errors is
known.known.
2)it can be done with equal reliability by beginners and expert, as2)it can be done with equal reliability by beginners and expert, as
it does not presume sophisticated clinical judgment.it does not presume sophisticated clinical judgment.
3)it is not time consuming.3)it is not time consuming.
4)it does not require special equipments for radiographic4)it does not require special equipments for radiographic
projections.projections.
The mandibular incisors have been chosen for measuring.The mandibular incisors have been chosen for measuring.

Procedure in the mandibularProcedure in the mandibular
arch:arch:
 Measure with a tooth measuring guage or a pointedMeasure with a tooth measuring guage or a pointed
Boley guage, the greatest m-d width of each of theBoley guage, the greatest m-d width of each of the
mandibular incisors.mandibular incisors.

Mixed dentition analysis..Mixed dentition analysis..
 Determine theDetermine the
space needed forspace needed for
alignment ofalignment of
incisors.incisors.
 Compute the amountCompute the amount
of space availableof space available
after incisorafter incisor
alignment.alignment.

 Now,predict the size of the combined widthsNow,predict the size of the combined widths
of cuspid, first bicuspid, and second bicuspids.of cuspid, first bicuspid, and second bicuspids.
 Long method-(Moyer's)Long method-(Moyer's)
 Prediction of the combined widths ofPrediction of the combined widths of
cuspid,first bicuspid and second bicuspidiscuspid,first bicuspid and second bicuspidis
done by use of probability charts.done by use of probability charts.

 No one figure can indicate the precise cuspid-No one figure can indicate the precise cuspid-
bicuspid sum for all people, since there is abicuspid sum for all people, since there is a
range of posterior tooth widths seen evenrange of posterior tooth widths seen even
when the incisors are identical.when the incisors are identical.
 The value at 75% is chosen as the estimate.The value at 75% is chosen as the estimate.
 Theoretically, one should use the 50% level ofTheoretically, one should use the 50% level of
probability, since any errors would thenprobability, since any errors would then
distribute equally.distribute equally.

 Short methodShort method :(:(Tanaka and Johnston, J Am Dent AssocTanaka and Johnston, J Am Dent Assoc
1974).1974).
 Add the widths of mandibular incisors and divideAdd the widths of mandibular incisors and divide
by 2.by 2.
 To the value obtained add 10.5 mm to predictTo the value obtained add 10.5 mm to predict
the combined widths of the mandibular cuspidthe combined widths of the mandibular cuspid
and bicuspids and 11.0 mm to predict theand bicuspids and 11.0 mm to predict the
combined widths of maxillary cuspid andcombined widths of maxillary cuspid and
bicuspids.bicuspids.
 This is a less precise method which does notThis is a less precise method which does not
allow for sexual dimorphisms with equalallow for sexual dimorphisms with equal
accuracy.accuracy.

 Now, compute the amount of space left in theNow, compute the amount of space left in the
arch for molar adjustment by subtracting thearch for molar adjustment by subtracting the
estimated cuspid and bicuspid size from theestimated cuspid and bicuspid size from the
measured space available in the arch aftermeasured space available in the arch after
alignment of incisors.alignment of incisors.

Procedure for maxillary arch:Procedure for maxillary arch:
 Similar to that of lower arch with twoSimilar to that of lower arch with two
exceptions:exceptions:
1) a different probability chart is used for1) a different probability chart is used for
predicting the upper cuspid and bicuspid sum.predicting the upper cuspid and bicuspid sum.
2) allowance must be made for overjet2) allowance must be made for overjet
correction when measuring the space to becorrection when measuring the space to be
occupied by the aligned incisors.occupied by the aligned incisors.

Problems:Problems:
 A problem arises when considering the space left forA problem arises when considering the space left for
molar adjustment.molar adjustment.
 Perhaps the most severe limitation of MixedPerhaps the most severe limitation of Mixed
Dentition analysis is their inability to reflect theDentition analysis is their inability to reflect the
position of the incisors with respect to the skeletalposition of the incisors with respect to the skeletal
profile.profile.
 A problem is imposed when the occlusal curve isA problem is imposed when the occlusal curve is
assumed to be a flat plane. Here it becomes obviousassumed to be a flat plane. Here it becomes obvious
that mixed dentition analysis is a two-dimensionalthat mixed dentition analysis is a two-dimensional
visualization of a complex three-dimensionalvisualization of a complex three-dimensional
problem.problem.

Hixon and Oldfather’sHixon and Oldfather’s method.method.
((Am J OrthodAm J Orthod 1980)1980)
 The mesio-distal width of the mandibular central andThe mesio-distal width of the mandibular central and
lateral incisor is obtained from the casts.lateral incisor is obtained from the casts.
 Determine the width of the un-erupted premolarsDetermine the width of the un-erupted premolars
from the intra-oral peri-apical radiographs madefrom the intra-oral peri-apical radiographs made
using long cone technique.using long cone technique.
 Add the width of central and lateral incisors with theAdd the width of central and lateral incisors with the
width of un-erupted premolars of that particular side.width of un-erupted premolars of that particular side.
 The estimated sum total width of the cuspids andThe estimated sum total width of the cuspids and
bicuspids of that particular side can be obtained frombicuspids of that particular side can be obtained from
the given chart.the given chart.

Hixon andHixon and
OldfatherOldfather
values.values.
 Every measured sumEvery measured sum
width of incisors andwidth of incisors and
bicuspids has abicuspids has a
corresponding sumcorresponding sum
width of the cuspids andwidth of the cuspids and
bicuspids in the chart.bicuspids in the chart.
Measured values inMeasured values in
mm.mm.
Estimated toothEstimated tooth
size in mm.size in mm.
2323 18.418.4
2424 19.019.0
2525 19.719.7
2626 20.320.3
2727 21.021.0
2828 21.621.6
2929 22.322.3

A revision of theA revision of the Hixon and OldfatherHixon and Oldfather
mixed-dentition prediction methodmixed-dentition prediction method..
 By Robert Staley andBy Robert Staley and
Paul Kerber.Paul Kerber.
 Graph showsGraph shows
relationship betweenrelationship between
size of lower incisorssize of lower incisors
measured from cast plusmeasured from cast plus
lower first and secondlower first and second
premolars measuredpremolars measured
from radiographs (from radiographs (xx--
axis) and size of canineaxis) and size of canine
plus premolars. (plus premolars. (yy-axis).-axis).

Huckaba’sHuckaba’s analysis.analysis.
((Dent Clin North AmDent Clin North Am 1964)1964)
 Both study models as well as radiographs areBoth study models as well as radiographs are
used for determining the width of un-eruptedused for determining the width of un-erupted
tooth.tooth.
 With radiograph, it is necessary to compensateWith radiograph, it is necessary to compensate
for the enlargement of the radiographic image.for the enlargement of the radiographic image.
 This can be done by measuring an object thatThis can be done by measuring an object that
can be seen both on radiograph and and on thecan be seen both on radiograph and and on the
study model, such as a primary molar tooth.study model, such as a primary molar tooth.

Contd..Contd..
 After the measurement, a proportional relationship can then beAfter the measurement, a proportional relationship can then be
established as follows:established as follows:
Actual width of primary molar(X1)Actual width of primary molar(X1) ==
Apparent width of primary molar(X2)Apparent width of primary molar(X2)
Actual width of unerupted premolar(Y1)Actual width of unerupted premolar(Y1)
Apparent width of unerupted premolar(Y2)Apparent width of unerupted premolar(Y2)
Or Y1=Or Y1= X1-Y2X1-Y2..
X2X2
This technique can be used for all ethnic groups.This technique can be used for all ethnic groups.

Functional analysis andFunctional analysis and
Equilibration of Occlusion.Equilibration of Occlusion.
 Study of patterns of attrition and facets ofStudy of patterns of attrition and facets of
wear.wear.
 A functional mandibular displacement can beA functional mandibular displacement can be
discovered by looking at the inclined planesdiscovered by looking at the inclined planes
and cusps of the teeth on the casts.and cusps of the teeth on the casts.
 Return to the mouth to check for prematurities,Return to the mouth to check for prematurities,
tooth guidance,tooth guidance,
cuspal interferencecuspal interference
and possible trauma.and possible trauma.

Contd…Contd…
 Study casts enable the dentist to study theseStudy casts enable the dentist to study these
things much more clearly and to correct them.things much more clearly and to correct them.
 One of the most valuable service the dentistOne of the most valuable service the dentist
can render is equilibration of patientscan render is equilibration of patients
occlusion . Without a set of study casts this isocclusion . Without a set of study casts this is
a hazardous procedure.a hazardous procedure.

Thank You.Thank You.

Methods to determineMethods to determine
Asymmetries of arch dimensionAsymmetries of arch dimension
and tooth position.and tooth position.

Method of using dividers to measure fromMethod of using dividers to measure from
the median raphe to estimate asymmetriesthe median raphe to estimate asymmetries
of the dental arches.of the dental arches. (Graber)(Graber)

Use of a symmetrograph to determineUse of a symmetrograph to determine
asymmetry in the dental arch.asymmetry in the dental arch. (Graber)(Graber)

Diagnostic set up.Diagnostic set up.
 Proposed byProposed by H.D.Kesling.H.D.Kesling.
 A popular practical technique for visualizing spaceA popular practical technique for visualizing space
problems in three dimensions in the permanentproblems in three dimensions in the permanent
dentition is that of cutting of teeth from a set of castsdentition is that of cutting of teeth from a set of casts
and resseting them in a more desirable positions isand resseting them in a more desirable positions is
called acalled a Diagnostic or Prognastic set upDiagnostic or Prognastic set up..
 Record casts are not used, since they must be used forRecord casts are not used, since they must be used for
comparison with the diagnostic set up and withcomparison with the diagnostic set up and with
progressive record casts.progressive record casts.

Technique.Technique.
 Obtain an accurate wax bite. Trim the posteriorObtain an accurate wax bite. Trim the posterior
portion of the bases of the casts with the wax biteportion of the bases of the casts with the wax bite
interposed so the bases are flush.interposed so the bases are flush.
 Drill a hole through the alveolar portion of the castsDrill a hole through the alveolar portion of the casts
well below the gingival margin of teeth.well below the gingival margin of teeth.
 Insert a fine saw blade through the hole and cut to theInsert a fine saw blade through the hole and cut to the
crest of gingival margin between two teeth. Repeatcrest of gingival margin between two teeth. Repeat
this for all the teeth to be cut off the cast.this for all the teeth to be cut off the cast.
 Align the teeth and wax them into the desiredAlign the teeth and wax them into the desired
positions. It is best not to cut all the teeth so that thepositions. It is best not to cut all the teeth so that the
bite relationship can be kept.bite relationship can be kept.

The Diagnostic Set Up.The Diagnostic Set Up.
(before and after)(before and after)

Uses of Diagnostic set up.Uses of Diagnostic set up.
 Useful in difficult space management problems toUseful in difficult space management problems to
ascertain ,before orthodontic treatment is begun ,ascertain ,before orthodontic treatment is begun ,
precisely the amount and direction each tooth must beprecisely the amount and direction each tooth must be
moved.moved.
 When extractions are contemplated as part of theWhen extractions are contemplated as part of the
orthodontic treatment ,the diagnostic set up willorthodontic treatment ,the diagnostic set up will
demonstrate vividly the amount of space created bydemonstrate vividly the amount of space created by
extractions and the tooth movements necessary toextractions and the tooth movements necessary to
close the space.close the space.
 Will also aid in choosing which teeth to extract.Will also aid in choosing which teeth to extract.
 Useful in patient motivation.Useful in patient motivation.

Digital study models.Digital study models.

Obtaining a 3-d study cast image.Obtaining a 3-d study cast image.
 Standard dental impressions of upper and lowerStandard dental impressions of upper and lower
arches using a Thixotropic Vinyl Polysiloxane crownarches using a Thixotropic Vinyl Polysiloxane crown
and bridge material.and bridge material.
 Impression scanning with an Ora-scanner.Impression scanning with an Ora-scanner.
 Create anCreate an e-e-model Digital Orthodontic Model usingmodel Digital Orthodontic Model using
proprietary technology available fromproprietary technology available from GeodigmGeodigm
Corporation.Corporation.
 The laser sensor accuracy is 0.01mm , whichThe laser sensor accuracy is 0.01mm , which
result in anresult in an ee-model 3D surface accuracy of-model 3D surface accuracy of
0.1mm with a Polygonal Mesh size of 30,0000.1mm with a Polygonal Mesh size of 30,000
polygons per jaw.polygons per jaw.

Ora-scanner.Ora-scanner.

OrthoCAD software(OrthoCAD software(Fairview,NJFairview,NJ).).
 Capable of capturing and presenting 3-D studyCapable of capturing and presenting 3-D study
models.models.
 With OrthoCAD digital models clinicians canWith OrthoCAD digital models clinicians can
easily store, retrieve, diagnose andeasily store, retrieve, diagnose and
communicate cases electronically, saving allcommunicate cases electronically, saving all
the hassles associated with plaster casts.the hassles associated with plaster casts.

Contd..Contd..
 Take alginate impressions of maxillary andTake alginate impressions of maxillary and
mandibular dentition and a bite registration.mandibular dentition and a bite registration.
 Send these to an OrthoCAD processing facilitySend these to an OrthoCAD processing facility
and within few hours,3-D study models areand within few hours,3-D study models are
downloaded to orthodontic office.downloaded to orthodontic office.
 The process requires an Internet connection, aThe process requires an Internet connection, a
download utility, and analyzing software.download utility, and analyzing software.

OrthoCAD allows for variousOrthoCAD allows for various
views of study casts for diagnosticviews of study casts for diagnostic
purposes.purposes.

Diagnostic tools included withDiagnostic tools included with
OrthoCAD.OrthoCAD.
 Measurement analysis:Measurement analysis:
recorded and saved.recorded and saved.
 Midline analysis: studyMidline analysis: study
models can be virtuallymodels can be virtually
split.split.
 Overjet and overbiteOverjet and overbite
analysis.analysis.

Diagnostic tools contd..Diagnostic tools contd..
 Occlusogram.Occlusogram.
 Magnification.Magnification.

Diagnostic tools contd..Diagnostic tools contd..
 Antero-posterior andAntero-posterior and
transverse adjustments.transverse adjustments.
 Notes.Notes.

OrthoCAD.OrthoCAD.
 In addition to diagnostic tools, software provides theIn addition to diagnostic tools, software provides the
orthodontist the ability to print various views, and toorthodontist the ability to print various views, and to
ee-mail files to other practitioners directly from the-mail files to other practitioners directly from the
program.program.
 Efficient magnetic and optical storage.Efficient magnetic and optical storage.
 200 3-D study models can be stored on a CD-200 3-D study models can be stored on a CD-
ROM with 650 MB storage space.ROM with 650 MB storage space.
 A 30 gigabyte hard drive can store 10,000 3-DA 30 gigabyte hard drive can store 10,000 3-D
study models.study models.
 Cost effective.Cost effective.

At last an adviceAt last an advice::
 GRABER- ‘ Take study casts of every patient; learn to lookGRABER- ‘ Take study casts of every patient; learn to look
for the variations of the normal and the departures from thefor the variations of the normal and the departures from the
normal. Make a check list so that you don’t miss anything.normal. Make a check list so that you don’t miss anything.
On each subsequent visit, take out the study casts andOn each subsequent visit, take out the study casts and
compare the present status of the mouth with that of thecompare the present status of the mouth with that of the
study casts taken earlier.study casts taken earlier.
What changes have occurred?What changes have occurred?
Are they favourable or unfavourable?Are they favourable or unfavourable?
Is there any drifting, over-eruption, prematurities, abnormalIs there any drifting, over-eruption, prematurities, abnormal
facets of wear, overbite problems?facets of wear, overbite problems?
Catch these before they develop.Catch these before they develop.
This is dentistry at its best- a preventive andThis is dentistry at its best- a preventive and
interceptive service.’interceptive service.’www.indiandentalacademy.comwww.indiandentalacademy.com

ReferencesReferences..
 Graber TM, Swain BFGraber TM, Swain BF: Orthodontics; Current: Orthodontics; Current
Principles and Techniques, Mosby, 1985.Principles and Techniques, Mosby, 1985.
 Proffit WRProffit WR: Contemporary Orthodontics, Mosby,: Contemporary Orthodontics, Mosby,
1986.1986.
 Graber, VandersdallGraber, Vandersdall: Orthodontics; Current: Orthodontics; Current
Principles and Techniques, Mosby, 1994.Principles and Techniques, Mosby, 1994.
 White TC, Gardiner JH, Leighton BCWhite TC, Gardiner JH, Leighton BC : Orthodontics: Orthodontics
for Dental Students, 1985.for Dental Students, 1985.
 MoyersMoyers : Handbook of Orthodontics.: Handbook of Orthodontics.
 LawsonsLawsons: Bench Top Orthodontics.: Bench Top Orthodontics.
 Phillip Adams, John KerrPhillip Adams, John Kerr : The Design, Construction: The Design, Construction
and Use of Removable Orthodontic Appliancesand Use of Removable Orthodontic Appliances..

 Bolton WABolton WA: Disharmony in tooth size and its relation: Disharmony in tooth size and its relation
to the analysis and treatment of malocclusion.to the analysis and treatment of malocclusion. AngleAngle
OrthodOrthod 1958;28:113.1958;28:113.
 Howes AEHowes AE: A polygon portrayal of coronal and basal: A polygon portrayal of coronal and basal
arch dimensions in the horizontal plane.arch dimensions in the horizontal plane. Am J OrthodAm J Orthod
1954;40:811.1954;40:811.
 Sanin C, Savara BSSanin C, Savara BS : Analysis of permanent: Analysis of permanent
mesiodistal crown size.mesiodistal crown size. Am J OrthodAm J Orthod 1971; 59:488.1971; 59:488.
 OrthoCAD :OrthoCAD : Seminars in OrthodonticsSeminars in Orthodontics, 1997., 1997.
 Orthodontic Model Boxes,Orthodontic Model Boxes, J Cl OrthodJ Cl Orthod, 1991., 1991.

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