Study casts are considered an essential diagnostic aid in diagnosis and treatment planning.Most of the information obtained by a careful study of the plaster casts serve to delineate more sharply and corroborate the observations made during the oral examinationn

1. DR. ABY AUGUSTINE
PG STUDENT
KVGDC SULLIA

2.  INTRODUCTION
 DIAGNOSTIC AIDS
 REQUISITES & USES OF MODEL
 TYPES & PRINCIPLE
 PERMANENT DENTITION ANALYSIS
 MIXED DENTITION ANALYSIS
 RECENT ADVANCES
 CONCLUSION

3.  Orthodontic treatment planning poses
significant challenges for clinicians with
respect to their ability to provide the most
predictable results for patients
 Teeth in well aligned arches are one of the
objectives of orthodontic treatment
 Success in orthodontic treatment – Diagnosis
 Different diagnostic aids are available
 Orthodontic casts – oldest

4.  ESSENTIAL AIDS
◦ CASE HISTORY
◦ CLINICAL EXAMINATION
◦ STUDY MODELS
◦ RADIOGRAPHS (OPG)
◦ FACIAL PHOTOGRAPHS
 NON ESSSENTIAL AIDS
◦ DESIRABLE RADIOGRAPHS
 CEPHALAMETRC
RADIOGRAPH
 OCCLUSAL RADIOGRAPH
 TMJ VIEW
◦ ELECTROMYOGRAPHY
◦ HAND WRIST
RADIOGRAPH
◦ BASAL METABOLIC RATE
ESTIMATION
◦ DIAGNOSTIC SET UP
◦ PHYSIO PRINTS
◦ OCCLUSOGRAMS

6.  Model analysis is
the study of
maxillary and
mandibular dental
arches in all the
three planes of
spaces using study
models and
radiographs which
is a valuable tool in
orthodontic
diagnosis and
treatment planning.

7.  Positive replica of tooth and surrounding
supporting structures
 Essential diagnostic aids

8.  Anatomic part
 Artistic part

9.  Should accurately reproduce all the teeth and
soft tissues without any distortion
 Should be symmetrical
 Models should be trimmed in such a way that
when placed on back, the accurately
reproduce the occlusion
 Should have a clean, smooth and nodule free
surface
 Should depict as much alveolar process as
possible

10.  Study of occlusion from all aspects
 Enables accurate measurements – arch
length, width and tooth size
 Educating the patient on the nature and
severity of malocclusion
 Motivation of patient
 Explain the treatment plan
 Assessment of treatment progress
 Mock surgery
 Transfer of records in case if the patient is to
be treated by another clinician

11.  Space analysis requires a comparison
between the amount of space available for
the alignment of the teeth and the amount of
space required to align them properly.
 First step-calculation of space available
 Second step-calculate the amount of space
required for alignment of the teeth

12.  Mixed dentition
analysis
◦ Moyer’s analysis
◦ Huckaba’s analysis
◦ Hixen and Old Father
analysis
◦ Nance analysis
◦ Tanaka Johnson
analysis
 Permanent
dentition analysis
◦ Ponts analysis
◦ Carey’s analysis
◦ Arch perimeter
analysis
◦ Ashley Howe’s
analysis
◦ Bolton’s analysis
◦ Linder Harth analysis
◦ Korkhaus analysis

14.  PRINCIPLE:
◦ Many malocclusion occurs as a result of discrepancy
between arch length and tooth material.
◦ This discrepancy is calculated using Arch perimeter
in maxilla and Careys analysis in mandible

15.  Determination
of arch length.
Arch length
anterior to the
first permanent
molar is
measured using
a soft brass
wire.
The wire is placed contacting the mesial surface
of the first permanent molar of one side and is
passed over the buccal cusps of the premolars
and along the anteriors and is continued on the
opposite side in the same way upto the mesial
surface of the opposite first permanent molar.

17.  Determination of
tooth material.
The mesio-distal
width of the teeth
anterior to the first
molars (second
premolars to second
premolars) is
measured and
summed up.

18.  Determination of the Discrepancy.
The discrepancy refers to the difference
between the arch length and tooth material.
 Inference.

19.  PRINCIPLE:
◦ Measurement of 4 maxillary incisors
establishes the width of the arch in the
premolar and molar region
◦ suggested that the ratio of combined
incisor to arch width ( as measured from
the center of the occlusal surface of the
teeth) was ideally 0.8 in the bicuspid area
and 0.64 in the first molar area

20.  HELPS IN:
◦ Determining whether the dental arch is
narrow or normal
◦ Determining the need for lateral arch
expansion
◦ Determining how much expansion is
possible at the molar and premolar region

21.  Determine the sum of M-D width of 4
maxillary incisors : SI

22.  Measure the width of the arch in the
premolar region from the distal pit of
one upper 1st premolar to distal pit of
the opposite 1st premolar: MPV

23.  Measure the width of the arch in the
molar region from the mesial pit of the
upper 1st molar to the mesial pit of the
opposite 1st molar: MMV

24.  Calculated premolar value/ expected
premolar value:
CPV= SI * 100
80
 Calculated molar value/ expected molar value
CMV = SI * 100
64

25.  If measured value is less than the calculated
value, it indicates the need for expansion.
 It is possible to know how much expansion is
needed in the premolar and molar region
respectively.
 Ponts 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 tooth in perfect alignment.

26.  Maxillary laterals are the commonly missing
from the oral cavity.
 Maxillary laterals may undergo morphogenic
alterations like peg shaped laterals.
 It does not take skeletal malrelationships into
considerations.
 Analysis is based on study of French
population and hence, its universal validity is
questionable.

27.  Similar to Pont’s analysis.
A variation has been proposed to determine
the calculated premolar value and calculated
molar value.
Calculated premolar value : S.I X 100
85
Calculated molar value : S.I X 100
64

28.  Similar to PONT’S analysis
 Uses LINDER HARTH formula
 PRINCIPLE:
◦ For a given width of upper incisors a specific value
of the distance between the midpoint of inter
premolar line to the point between the two incisors
should exist
◦ Introduces a third measurement from the
midpoint of inter- premolar line of upper arch to
a point in between the two maxillary incisors.

29.  SIMILAR TO PONT’S

30.  For the values noted, the mandibular value
(Ll) should be equal to the maxillary value
(Lu) in millimeters minus 2mm.

32. This analysis tells about the arch width.
 If the perpendicular distance is more
than ideal, then anterior teeth are
proclined.
 If the perpendicular distance is less than
the ideal, then the anterior teeth are
retroclined.

33.  PRINCIPLE:
◦ There exists a relationship between total width of 12
teeth anterior to the second molars and the width of
the dental arch in the first premolar region.

34.  Determination of total
tooth material.
The mesio distal
width of all the teeth
mesial to the second
permanent molars is
measured with the
help of dividers and
the values are
summed up. This
value is called Total
Tooth material (TTM).

35.  DETERMINATION OF
PREMOLAR DIAMETER(
P.M.D)
◦ Arch width from the tip
of the buccal cusp of
one 1st premolar to the
tip of the buccal cusp of
the opposite 1st
premolar

36.  Determination of
premolar basal arch
width:
◦ The measurement of the
width from canine fossa
of one side to the other
gives us the width of the
dental arch at the apical
base or the junction
between the basal bone
and alveolar process
The canine fossa is
found diatal to the
canine eminence

37. If the canine fossa is
not clearly
distinguishable then
the measurement is
made from a point
8mm below the crest of
inter dental papilla
distal to the canine

38.  If PMBAW > PMD arch expansion
is possible
 If PMBAW < PMD arch expansion
is not possible
 Howe’s believed that the premolar basal
arch width ( B.A.W) which he called as the
canine fossa diameter should equal
approximately 44% of the mesio distal
widths of the 12 teeth in the maxilla, if it is
to be sufficiently large enough to
accommodate all the teeth.
 When the ratio is less than 37%, he
considered this to be a basal arch deficiency
necessitating extraction of premolars.

39.  PMBAW% = PMBAW * 100
TTM
IF PMBAW% < 37% Need for extraction
IF PMBAW % > 44% Treated without
extraction
If PMBAW% 37-44% Borderline cases

40.  Howe’s analysis is useful in treatment planning of
problems with suspected apical base deficiencies
and deciding to whether to,
1) Extract teeth,
2) Widen the dental arch, or
3) Expand rapidly the palate.
 Howe’s analysis is applicable to each arch.

41.  BOLTON’S TOOTH SIZE RATIO ANALYSIS
 PRINCIPLE:
◦ There exists a ratio between the M-D width of
maxillary and mandibular teeth
◦ To attain an optimum inter arch relationship, the
maxillary tooth material should be proportionate to
the mandibular tooth material thereby creating a
normal overjet and overbite

42.  Bolton pointed out that the extraction of one tooth
or several teeth should be done according to the
ratio of tooth material between the maxillary and
mandibular arch, to get ideal interdigitation,
overjet, overbite and alignment of teeth.
 Helps in determining disproportion in size
between maxillary and mandibular teeth

43.  Sum of mandibular 12.
 Sum of maxillary 12.
 Sum of mandibular 6.
 Sum of maxillary 6.
 Overall Ratio.
 Anterior Ratio.

44.  DETERMINATION OF OVERALL RATIO:
◦ ACCORDING TO BOLTON, the sum of M-D
widths of the mandibular teeth mesial to the
2nd permanent molar is 91.3% the M-D width
of maxillary teeth mesial to 2nd molar
Overall ratio = sum of mand 12 * 100
sum of max 12
◦ If ratio < 91.3% maxillary tooth excess
 Max excess = max 12 – mand 12 * 100
91.3

45.  If ratio > 91.3% mandibular tooth
excess
 Mandibular excess= mand 12 – max 12 *91.3
100

46.  DETERMINATION OF ANTERIOR RATIO:
according to BOLTON, The sum of mesio
distal width of the mandibular anteriors to
the mesio distal width of the maxillary
anteriors should be 77.2%.
Anterior Ratio = Sum of mandibular 6 *100
Sum of maxillary 6
If ratio < 77.2% maxillary anterior
excess
Maxillary excess = max 6 – mand 6 * 100
77.2

47.  If ratio > 77.2% mandibular anterior
excess
 Mandibular excess=
mand 6 – max 6 *77.2
100

49.  OBJECTIVE:
◦ Evaluation of the size of the unerupted
canines and premolars
◦ The Mixed Dentition Analysis helps one
to estimate the amount of spacing or
crowding which would exist for the
patient if all the primary teeth were
replaced by their successors the very
day the analysis is done.

50.  Premature loss of canines
 Rotation of lateral incisors
 Ectopic eruption of molars
 Distal terminal plane relationship
 crossbite

51.  Estimation from proportionality table:
◦ moyers(1967)
◦ Tanaka and Johnson
 Radiographic method
◦ Huckaba G.W analysis(1964)
◦ Nance analysis
 Combined method
◦ Hixon and Oldfather (1956)
◦ Modified by Staley and Kerbers (1980)

52.  Principle:
◦ High correlation between different teeth in same
individual
◦ Possible to predict the size of unerupted teeth by
looking at the teeth present in oral cavity
◦ Size of unerupted permanent canine and premolars
are predicted from the knowledge of the size of
certain permanent teeth already erupted in the oral
cavity – permanent mandibular incisors

53. Mandibular Incisor have been choosen-
 Erupted early in the mouth.
 Easily measured accurately.
 Are directly in the midst of most space
management problems.
Maxillary Incisors are not chosen-
 Variability in size and their co-relation with other
group of teeth are of lower predicted value.

54.  Dental cast
 Boley’s gauge
 Moyer’s probability chart

55. •Measure the width of each of 4 mandibular
permanent incisors
•Total the M-D width of the mandibular
incisors

56.  Calculate the space available for
mandibular cuspids and bicuspids from
the distal aspect of aligned lateral
incisor to mesial aspect of 1st
permanent molar

57.  Using Moyer’s probability chart the sum
total of total width of upper and lower
cuspids and bicuspids for the given sum
width of lower central and lateral incisors
are calculated
 An experienced clinician can use 50%
Prediction since it is more precise
estimate.
 For inexperienced clinicians, they should
use the 75% Prediction for combined
widths of Canines and two Premolars

60.  if the predicted value is greater than available
arch length, crowding of the teeth can be
expected

61.  It has minimal systematic error and the range of such error is known.
 It can be done with equal reliability by the beginner and the expert as
it does not presume sophisticated clinical judgement.
 Not time consuming
 Requires no special equipment or radiographic projections.
 Although best done on dental casts, it can be done with reasonable
accuracy in the mouth

62.  This approach generally can be used to predict the
combined widths of a group of unerupted teeth but
cannot be used to estimate the size of any single
unerupted tooth
 The Moyer's analysis is a probability diagnosis.
 The Moyer's analysis does not account for tipping
of the mandibular incisor, either lingually or
facially.

63.  Considered as a modification of Moyer’s
analysis
 Conducted studies on 506 orthodontic
patients in cleaveland.
 Proposed a regression formula for obtaining
the expected widths of unerupted permanent
canine and premolars

64.  PREDICTED WIDTH OF MAX. CANINE TO
PREMOLAR = SUM OF MAND. INCISORS + 11
2
PREDICTED WIDTH OF MAND. CANINE TO
PREMOLAR = SUM OF MAND. INCISORS+10.5
2

65.  Radiographic method – 1947
 Similar to Carey’s arch perimeter analysis for
permanent dentition
 Armamentarium
◦ Dental cast
◦ Boley gauge
◦ Millimeter ruler
◦ Periapical radiograoph

66.  Measure the M-D
width of the
mandibular
permanent incisors
 Measure the width of
unerupted
mandibular canine
and premolars from
the radiograph
 Gives the space
needed to
accommodate
permanent teeth
anterior to first
permanent molars

67.  Measure the space
available for
permanent teeth using
a brass wire
 From the
measurement 3.4 mm
is reduced to
compensate for the
mesial drift of the 1st
molar
 This gives the space
available for
permanent teeth
anterior to 1st molar
 By comparing the two
measurements, space
available and space
required can be
predicted

68.  Advantages:
◦ Can be performed with reliability
◦ Allows analysis of both the arches
 Disadvantages:
◦ Time consuming
◦ Full mouth radiograph is required
◦ Depends on the skills of the practitioner

69.  Huckaba G.W 1964
 Uses both study casts and radiographs for
determining the width of unerupted teeth
 Compensates for the radiographic
enlargement of tooth image

70.  degree of magnification for a primary tooth
will be the same as that of its underlying
permanent successor on the same film
 Can be used in both maxillary and
mandibular arches

71.  Measure the Width of primary teeth in x-
ray
 Measure the width of underlying
permanent successor in x-ray
 measure the width of the primary tooth on
the cast
 Width of unerupted permanent tooth can
be obtained

actual width of primary molar(X1) actual width of
= permenent premolaR(Y1)
apparent width of primary molar (X2) apparent width of
permanent premolar(Y2)
Y1 = X1 * Y2
X2

72.  1958
 Modified by ( STANLEY AND KERBER – 1980)
 This procedures combines measurements
from the dental casts and width
measurements from the periapical
radiographs
 Used only for mandibular arch

73.  Measure the size of unerupted 1st & 2nd
premolar in one mandibular quadrant
from a peri apical radiograph.
 Determination of mesio distal tooth
width of the lower central and lateral
incisors on the study cast to the side of
the radiograph

74.  X-axis :
Mandibular
incisor width
measured on
the dental
cast + total
width of 1st &
2nd premolar
on the peri
apical
radiograph.
 Y-axis :
Predicted
total width of
permanent
mandibular
canine and 1st
& 2nd
premolar.

75.  The formula for calculation-
Σ3+4+5=[(Σ 1+2+4+5) X 0.7158]+2.1267
 After adding together both figures, the
probable width of the permanent canine
and 1st & 2nd premolars for the
corresponding quadrant can be read off in
the prediction graph under the column of
the calculated sum total.

77. 1. Computerised analysis of
dental casts
2. Digital Study Models
3. Occulsograms
4. e-MODELS-3D Digital
dental models using laser
technology
5. Ortho CAD TM
Technology

78.  The purpose of the computer program, MODELS,
is to carry out routine analysis of dental models
for all patients who are treated in the orthodontic
clinic.
 It is used in various research studies related to
assessing changes in the dentition as a result of
orthodontic treatment.
 Data for the program are obtained by means of
digitizing a set of standardized two-dimensional
photographic views of the dental models.
A COMPUTER PROGRAM FOR THE ANALYSIS OF DENTAL MODELS:
COMPUTER PROGRAM IN BIOMEDICINE 10 (1979) 261-270

79.  Computerized software are now capable of
scanning study models and storing the
scanned data as 3D images.
3D digital study models are designed to over
come the problems –
 Storage and Retrieval
 Diagnostic Versatility
 Transferability
 Durability
DIGITAL MODELS - AN INTRODUCTION: SEMIN ORTHO 10:236-238 (2004)

80.  Archiving Study Cast
 Documentation of treatment progress and
communication between professional
colleagues is made easy.
 Can examine intra & inter arch and
transverse relationships between U&L arches
 Treatment objectives and planning can be
created by using “Virtual set-up” of
orthodontic appliance.

81.  To estimate final occlusal relationship.
 Estimate tooth movements in all 3 planes.
 Determine changes in the cant of occlusal
plane.
 Aid in arch wire construction.
 Growth prediction with the help of tracing.
 Quantifying the treatment progress and
discovering the exact nature of many
orthodontic problem.

82.  Developed by Burstone in 1969.
 Occlusograms are actual sized photographs
of occlusal surface of dental casts.
 Tracings of these occlusograms allows the
orthodontist to simulate treatment in occlusal
view.

83.  Photographic method:
◦ Occlusal surface of U & L dental casts are
photographed in a 1:1 ratio and a tracing of the
photograph is made.
 Photocopying method:
◦ The casts are photocopied on a photocopier
machine and the occlusal photocopy is used to
obtain a tracing.

84.  An occlusogram is a 1:1 reproduction of
occlusal surface of plaster models on a sheet
of acetate tracing paper.
 4x5 inch positive film transparencies are
ideal.
 These allows occlusograms to be held one
over the other to examine cuspal
relationship.
 The photographs can be taken either with
35 mm camera and enlarged to 1:1
magnification or with a 4x5 inches Polaroid
camera for 1:1 instant photographic prints.

85.  Photographic prints are ideal for tracing
purposes.
 Problem with producing 4x5 inch
transparencies or photographic print is
maintaining the accurate orientation of the
dental cast which must be accurately trimmed
in the centric relation position

86. Once the dental cast is trimmed in centric
relation, registration grooves are made.
Both the casts are seated in registration
track in centric relation.

87.  Cast is placed on the registration track on the
Occlusostat as soon as it is ready for
photograph.
 Occlusal surface of teeth are flushed with the
leading edge of the occlostat which is also the
focal length of the camera.

88.  A sheet of tracing paper is placed over the
photocopy of the cast, rough side up and is
secured at the corners using masking tape.
 Tracings are made of both U & L
occlusograms.
 R & L should be marked to avoid confusion.
 Tracings can be separated by cutting
between the registration lines.

89. With the U & L occlusogram tracing registered
and secured on the sides, the mid sagittal
registration line can be copied on the lower
tracing.
Growing denture bases can be adjusted so that
they’ll be in their predicted relationship at the end
of treatment periods.

90. Micheal R. Marcotte –demonstrated the uses of
occlusograms in planning orthodontic
treatment.
 Determine arch form and width.
 Solution to arch length discrepancies.
 Presence and extent of skeletal asymmetries.
 Anchorage requirements in each quadrant for
extraction cases.
 Presence and extent of tooth mass
discrepancies.

91.  Time consuming.
 Not very precise.
 Because of difference in magnification, the
combination of occlusogram with a head
film has been considered difficult and
unreliable.

92.  Simulation of space following extraction,
tooth uprighting or incisor retraction can be
easily shown.
 3D prefabrication of archwires using specific
robotics after setting up brackets position on
the dental arches.
 Construction of 3D “ Aligners”- The Invisalign
technology.

93.  Three dimensional digital study model.
Methods of producing digital models:
 Destructive imaging: Removes the part of the
cast ,a little at a time ,while it is being
imaged.
 Non destructive imaging: Uses structural light
,laser light or x-rays to image while leaving
the original cast intact.
LASER IN ORTHODONTICS: INTERNATIONAL JOURNAL OF CONTEMPORY DENTAL
AND MEDICAL REVIEWS (2014) ARTICLE ID: 041014

94.  Constructed through a
laser scanning process
that digitally maps the
geometry of a patient’s
dental anatomy to a high
resolution 3D digital
image with an accuracy of
+. 01mm.
e - models:

95.  A laser stripe is projected onto the
surface of the plaster cast & a digital
camera is used to analyze distortions
in the stripe.
 The plaster cast is oriented on all
axes to expose all its surfaces for
scanning.
95

96.  This process produces 3D vertices that
are connected into thousands of
triangles to form the 3D image.
 The software then displays the e-model
on the computer screen by assigning
color shades to each triangle based on
its relative orientation to a digital light
source. This results in a high-resolution
3D image that can be viewed measured
& manipulated on the computer screen
as if the cast is in your hand.

97.  Measurements can be made in any plane or
orientation.
 Various analysis such as Bolton’s analysis,
arch width & length analysis can be done.
 Cross-sectional tools allow e-models to be
sliced in any vertical or horizontal plane to
check symmetry, overjet, overbite & complete
measurements at any location.

98.  Permits analysis of occlusal
relationships.
 Record keeping
98

99. 99
 Improves accuracy & efficiency of
orthodontic diagnosis, treatment
planning & bracket placement.
 Midline analysis (skeletal or dental
asymmetries can be evaluated).
 Mock surgeries & presurgical
evaluation can be done.
 Ease in storage

100.  It is a system to produce 3D digital study models.
 Software has been developed by CADENT(USA).
 The ability to rotate, tilt and section models, and
hold them in any position, potentially allows for far
more detailed analysis, with the added advantage
of bringing the models up instantly, along with the
other clinical information, chairside.
 It gives the orthodontist a virtual 3D set of models,
which can be manipulated in all planes of space;
sectioned in any plane and measured along any
plane with considerable accuracy.
CURRENT PRODUCTS & PRACTICES ORTHO CADTtm :
JOURNAL OF ORTHODONTICS , Vol. 31, 2004 344-347

101. Computer screen visualization of ‘virtual’ study models
by OrthoCADtm

102.  a simpler and more effective method of
measuring and storing data taken from the
‘virtual’ model.
 simpler storage and integration into the
patients ‘digital’ file, along with the digital
photographs, x-rays and clinical notes.
 simpler retrieval and viewing along with the
patients other clinical data especially at the
chairside.
 easy transferral to others in the patient’s
healthcare circle via prints or email
attachment

103.  ‘virtual models’ cannot be mounted and
articulated in reference to the patient’s
tempero-mandibular joint functions.
 High cost.

104.  There are numerous model analysis based
on different criteria. It is left to the
orthodontist to accept which analysis he
feels best suites his diagnosis and
treatment planning.
 The basis remains the same only the ways
to express it differs so does not matter
which analysis one follows but what matters
is that how efficiently one imply the results
to the treatment planning and do justice to
the patient.

105.  Handbook of orthodontics.
- ROBERT E. MOYERS.
 Textbook of orthodonttics. – BHALAJHI
 Textbook of orthodontics.
– GURKEERAT SINGH
 Textbook of orthodontics.
- WILLIAM R. PROFFIT
 Textbook of orthodontics – SRIDHAR PREMKUMAR
 Comparison of mixed dentition analysis methods
and to evaluate the most reliable one. JIOS-
volume 49, 2015.

106.  Journal of Orthodontics , vol. 31, 2004 344-
347
 Laser in orthodontics: international journal of
contempory dental and medical reviews
(2014) article id: 041014
 Current products & practices ortho cadt
:journal of orthodontics , vol. 31, 2004 344-
347
 Digital models - an introduction: semin ortho
10:236-238 (2004)
 A computer program for the analysis of
dental models: computer program in
biomedicine 10 (1979) 261-270
 The use of occlusograms in planning
orthodontic treatment: ajo 69(6) july 1976;
655-657