Diagnosis and space analysis in orthodontics

1. DIAGNOSIS ON STUDY CASTS
AND SPACE ANALYSIS
GROUP D

2. CONTENTS
1. INTRODUCTION
2. REQUIREMENTS OF STUDY CASTS
3. USES OF STUDY CASTS
4. IMPORTANCE OF STUDY CASTS
5. PARTS OF STUDY CASTS
6. TYPES OF STUDY CASTS
7. FABRICATION OF STUDY CASTS
8. DIAGNOSIS ON STUDY CASTS
9. SPACE ANALYSIS
10.REFERENCES

3. INTRODUCTION
• Orthodontic study casts are essential diagnostic records which help to
study the occlusion and dentition from all three dimensions.
• They are accurate plaster reproductions of the teeth and the surrounding
structures.

4. REQUIREMENTS OF STUDY CASTS
1. Should accurately reproduce teeth and their surrounding structures.
2. Should be trimmed so that they are symmetrical and pleasing to the
eye and so that any asymmetrical arch form can be easily recognized.
3. Should be trimmed in a such a way that the dental occlusion shows by
setting the models on their backs.
4. Should be trimmed such that they replicate the measurements and
angles proposed for trimming them
5. Should have a clean, smooth, bubble free surface with sharp angles
where the cuts meet.
6. Finished models should have a glossy mar proof finish.

5. USES OF STUDY CASTS

6. IMPORTANCE OF STUDY MODELS

7. PARTS OF STUDY CASTS
• Made up of 2 parts;
1. Anatomic portion- has the actual impression parts
of the dental arch and the surrounding structures.
2. Artistic portion- is the base of the casts that gives
a pleasing and symmetrical appearance of the
models
• In a good fabricated model, ratio of anatomic
portion to artistic portion is 3:1

8. TYPES OF CASTS AND STEPS
OF FABRICATION
COLLINS TOO

9. Types of Orthodontic Study Models
Plaster Models
Traditional orthodontic study
models made from dental
plaster provide high accuracy
and detail, making them ideal
for precise treatment
planning.
Digital Models
Advanced technology allows
orthodontists to create digital
study models using intraoral
scanners, providing efficient
and convenient access to
patient data.
Clear Aligner Models
Invisalign and other clear
aligner systems use custom-
made removable plastic
aligners, which serve as both
orthodontic treatment
appliances and study models.

10. Types of Orthodontic Study Models
Digital Models Clear Aligner Models

11. Materials Used to Create Orthodontic
Study Models
Dental Plaster
Traditional plaster is still
commonly used due to its
accuracy, ability to
reproduce fine details, and
relative affordability.
3D Printing Resins
With the advent of 3D
printing, orthodontists can
use specialized dental
resins to create precise
and durable study models
rapidly.
Thermoplastics
Clear thermoplastic
materials, such as
polyethylene terephthalate
glycol, are growing in
popularity for creating
transparent study models.

12. Materials Used to Create Orthodontic
Study Models
3D Printing Resins
With the advent of 3D
printing, orthodontists can
use specialized dental
resins to create precise
and durable study models
rapidly.

13. The Process of Creating Orthodontic
Study Models
1 Impression Taking
An impression of the patient's teeth
and oral structures is created using
alginate or silicone materials.
2
Plaster or Resin Casting
The impression is filled with dental
plaster or 3D printing resin, allowed to
set, and carefully removed to create a
detailed replica of the patient's teeth.
3 Trimming and Finishing
Excess material is trimmed, and the
study models are polished to ensure
accuracy and promote a smooth
surface.
4
Articulation and Mounting
If necessary, the study models are
mounted on an articulator, allowing
orthodontists to simulate the patient's
jaw movements during treatment
planning.

14. The Criteria for Study Models
Models have 2 distinct portions:
A) Art portion : the base of the model
B) Anatomic portion : the teeth, alveolar process and palate

15. Important criteria when taking
impression for a study model:
All detail is reproduced, including the complete peripheral turn and a
portion of retromolar pads or tuberosities.
Detail is sharp, not blurred or indistinct.
Free of voids in critical areas and free of large folds of alginate.
No areas where alginate has pulled away from the tray.
Free of rips and tears except in interproximal areas.
Alginate thoroughly covers the tray, no tray visible through alginate
.
Free of bulges or depressions that indicate a subsurface bubble.

16. Steps in pouring the study
model
1. Mix the mixture of orthodontic plaster (50% stone; 50% plaster of paris)
2. Pour the alginate impressions with orthodontic plaster.
• Flow into the tooth portions from the palate in maxilla
• Flow into the tooth position from the posterior aspect and around the
arch in mandible

17. Steps in pouring the study
model
3. Fill the base formers with orthodontic plaster.
• Ensure a degree of centralization
• Do not push the impression tray too deeply
• Make sure the bottom of impression tray, the occlusal surface of
impression, and the bottom of the base former are all parallel
4. Allow the time for orthodontic plaster to set.
5. Once it sets, remove the tray and alginate carefully to avoid fracture.

18. Steps in trimming preparation
1. Remove all nodules and imperfections with sharp instrument.
2. Soak the models in water for 5-15 minutes. Use the gentle trimmer and
firm pressure.

19. Trimming Technique
• Starting with upper model
1. Occlude upper model on rubber pad.
2. Trim the base until case exhibit 1/3 art portion and 2/3
anatomic portion.

20. Trimming Technique
3. Check the paralellism of the occlusal plane
by placing the teeth on the horizontal surface and comparing the base
of cast to the horizontal surface.

21. Trimming Technique
4. Occlude the upper and lower models with wax bite in place.
5. Check the relationship of the last molars to each other. If the lower molars
extend significantly further than the upper molar, mark a line the distance of
the extension to the 1 cm distance from the last molar of the lower molar.

22. Trimming Technique
• Upper model posterior side
1. Mark a light pencil line down the midline suture of the model for reference.
2. Mark the line of posterior side perpendicular to midline suture of the model.
3. Trim the posterior side following the line.

23. Trimming Technique
• Upper model lateral sides
1. Mark the line of lateral sides at 60° from posterior side at the right and left side of the model.
2. The line should be 1 cm from buccal surfaces of the teeth (the side should not be trimmed beyond the depth
fold).
3. Trim the lateral sides following the line.

24. Trimming Technique
• Upper model anterior sides
1. Mark the line of anterior sides at 30° from the lateral sides to a point beginning at the midline and ending at the cuspids-preserving the anterior buccal
fold.
2. The line must be equal on both sides of the cast.
3. Trim the anterior sides following the line.

25. Trimming Technique
• Upper model heel sides
1. Mark the line of heel sides at 120° from posterior side.
2. The line must be equal on both sides of the cast.
3. Trim the heel sides follow the line.
* All the trimming procedures,
anatomy extensions should be
equidistant around the entire
arch for both model.

26. Trimming Technique
• Establishing the base of mandibular cast
1. Occlude the mandibular cast with the maxillary cast using the wax.
2. With the base against the grinding wheel, cut the base of mandibular cast (parallel to maxillary cast)
3. Trim the base until case exhibit the 1/3 art portion and 2/3 anatomic portion.

27. Trimming Technique
• Lower model posterior sides
1. With the wax bite still in place, position the models in a vertical position on the trimming table.
2. Place the base of maxillary cast on the trimming table.
3. Trim until the posterior borders of mandibular cast.
4. Preserve the retromolar pad of mandibular cast and tuberosity of maxillary cast.

28. Trimming Technique
• Establish lower model
heel sides and lateral
sides according to the
upper cast

29. Trimming Technique
• Lower model anterior side
1. With the occluded models, trim the anterior sides
of the model.
2. Maintained the same amount of anatomy
extension as on the upper model.
3. Both sides the same length and angulations of the
corners.

30. Trimming Technique
4. Take the mandibular cast, trim the anterior region
3-3 cuspid to within 7 mm of the most protruded
anterior tooth or from the mucobuccal fold,
whichever most labial.

31. Trimming Technique
5. Carefully, round off the anterior borders of the
cast. There is no tool to assist you in rounding the
anterior border, you must use your dexterity.

32. Trimming Technique
6. Lightly touch all trimmed surfaces of both models on the fine
wheel until heavy scratches are removed.

33. Trimming Technique
• Model finishing.
1. With a lab knife or other suitable instrument, even up irregularities of the maxillary cast and
lingual portion.
2. Remove the bubbles and other artifacts
3. Make the depth of the vestibule visible.
4. Fill in and patch air bubbles in models where needed any small holes while the models are still
wet with a thin mix of plaster.
5. Set models aside to dry.

34. Trimming Technique
• Model finishing.
6. After models have dried, using a wet-dry grade of fine-grit sandpaper wet sand the casts to
remove the scratches left by grinding wheel.
7. When sanding the posterior borders, the sides and the heels of the models, it must be in centric
occlusion and the borders made smooth at the same time.
8. Allow models to thoroughly dry (at least 24 hours).
9. Soak 20 minutes in warm concentrated soap solution.
10. Permit models to dry and rub with chamois skin or nylon until glossy.

35. Trimming Technique
• Label the casts
Label the upper and lower casts with the following
details:
i) Patient’s name
ii) Registration number
iii) Patient’s date of birth
iv) Date of impression
v) Dental officer’s name

36. DIAGNOSIS ON STUDY CAST
IVY MUDAKI

37. CASTS APART
• Arch form
• Palatal vault
• Arch symmetry
• Teeth present
• Crowding
• Spacing
• Buco/linguoversion
• Supra/infraversion
• Torsiversion
• Transpositioning
• Proclined
Linguoversion of 11 Torsiversion of 21

38. CASTS IN OCCLUSION
• Incisor relationship
• Overjet
• Overbite
• Canine relationship
• Molar relationship
• Dental midline
• Cross bites
Deep bite and upper
anterior crowding
Anterior cross bite

39. SPACE ANALYSIS
IVY MUDAKI BDS/1001/17

40. DEFINITION AND INDICATIONS
• It is the procedure of quantifying the space in each arch which helps
with:
• Treatment planning- to extract or not to extract, which teeth to extract
and obtaining space for the same.
• If it is mild <4mm, moderate 5-9mm and severe crowding>10mm
• It helps to determine the mechanics to be used and plan anchorage
accordingly

42. ARMAMENTARIUM FOR SPACE ANALYSIS
• Ruler/Wedge ruler
• Divider
• Vernier Calipers or Boley
gauge
• Brass wire

43. CLASSIFICATION OF SPACE ANALYSIS INDICIES
1. Based on Technique and Parameters
A. Tooth size-Arch width discrepancy
1. Pont’s Analysis
2. Linderharth Analysis
3. Korkhaus Analysis
4. Ashley-Howe Analysis
B. Tooth shape disharmony
1. Peck and Peck Index
C. Photographic Analysis of study model
1. Sterophotogrametry
2. Occlusograms
3. Holographic Image Analysis
D. Computerized analysis
1. Oscopo
2. Reflex metrography
D. Tooth size-Arch length discrepancy
1. Arch perimeter analysis
2. Nance Analysis
3. Carey’s Analysis
4. Ree’s Analysis
5. Larry White Analysis
6. Total Space Analysis
7. Tweed analysis
E. Tooth-size disharmony
Bolton’s Analysis
F. Estimating Size of unerupted teeth
1. Moyer’s Analysis
2. Tanaka and Johnston’s Analysis
3. Huckaba’s Analysis

44. 2. Based on Type of Dentition

45. 1. ARCH PERIMETER ANALYSIS
• Tooth material and arch length discrepancy
• It is done in the upper arch
• Two measurements are required for intra maxillary analysis of
space requirements :
1. Space available calculations
2. Space required calculations
45
study model

46. • Arch perimeter is the geographical dental arch formed by teeth incisal
/ cuspal edges.
• Procedure
1. For space available : measures the arch circumference from mesial
of FPM to mesial of FPM.
If the teeth are proclined (cingulum), if they are retroclined (labial)
2. For space required : a combined MD width of the permanent teeth
from 5 to 5.
3. Difference = arch discrepancy /excess.
46

47. 47
study model

48. DETERMINATION OF THE DISCREPANCY
• The difference between space required and the space
available gives a space discrepancy /excess.
• If the tooth material is more than the arch length then
the space available for alignment is insufficient, results
in Crowding.
• If the tooth material is less than the space, then there
will be spacing.
48
study model

49. Interpretation of arch perimeter analysis
Arch length discrepancy
• 0-4mm
• 4-8mm
• >8mm
Inference
• Proximal stripping
• Pt can be treated with or without
extractions depending on lip
procumbency and other factors.
• Extraction of first pm
49 study model

50. 2. CAREY'S ANALYSIS
• Performed on the lower cast
• Upper cast: arch perimeter analysis.
• How?
– Determine arch length: brass wire passed from mesial of FPM across
buccal cusps of premolars and on the incisal edges of incisors to the
mesial of the opposite FPM.
• If the teeth are proclined (cingulum), if they are retroclined (labial)
– Determine tooth material
– Determine the discrepancy
50
study model

51. CAREY'S analysis inference
Discrepancy
• 0-2.5mm
• 2.5-5mm
• >5mm
Inference
• Proximal stripping
• Extraction of second pm
• Extraction of first pm
51 study model

52. 3. PONT'S ANALYSIS
• Pont in 1909 proposed a method of determining the ideal
dental arch width in the premolar and first Molar area
based on the sum total of M-D widths of maxillary
incisors.
• Pont suggests that: the combined upper incisors width to
transverse arch width was ideally 0.80 in the premolar
area and 0.64 in the Molar area.
52
study model

53. Pont's analysis helps in
1. Determining dental arch width
2. Determining the need for lateral arch expansion
3. Determining how much expansion is possible at the premolar
and Molar region.
Measurements:
a. Determination of Sum of Incisors (SI)
b. Determination of Calculated Premolar Value (CPV)
c. Determination of Calculated Molar Value (CMV)
d. Determination of Measured Premolar Value (MPV)
e. Determination of Measured Molar Value (MMV)
53
study model

54. STEPS IN PONT’S ANALYSIS
1. Determine SI (mesiodistal widths)

55. STEPS IN PONT’S ANALYSIS
2. Determine CPV
(SI x 100)/80
3. Determine CMV
(SIx100)/64
4. Determine the MPV – width of arch
measured from distal pit of upper first premolar
to distal pit of opposite first premolar
5. Determine the MMV – width of arch from
mesial pit of upper 1st permanent molar to
mesial pit of opposite 1st permanent molar

56. PONT’S ANALYSIS INFERENCE
• If the Calculated value is greater than measured value then the
arch is narrow for the given sum of the incisors width then
expansion can be done.
• When calculated value is less than the measured value then
the arch is wider and therefore there is no scope of expansion.
56
study model

57. DRAWBACKS OF PONT’S ANALYSIS
• Analysis is based on the study of French population
• Analysis does not consider alignment of teeth
• Analysis does not consider malformations of teeth

58. 4. LINDERHARTH ANALYSIS
• Linder harth proposed an index very similar to that of
Pont's analysis.
• He made variations in the formula to determine the
calculated premolar and Molar value.
• It is calculated using this formula :
• CPV =SI*100/85
• CMV =SI *100/64
58
study model

59. 5. BOLTON'S ANALYSIS
• Wyne Bolton considered the ratio of the tooth
material of the maxillary arch to the mandibular arch
to be by nature have predetermined proportions to
maintain normal occlusal relationships.
• An alteration of this balance will lead to improper
intercuspitation, overjet or spacing.
59
study model

60. 60

61. 61

62. 62

63. AMOUNT OF ANTERIOR EXCESS
• Amount of Mandibular anterior excess is determined by:
Sum of Mandibular 6 – ((Sum of maxillary 6 x 77.2)/100)
• Amount of Maxillary anterior excess is determined by:
Sum of Maxillary 6 – ((Sum of Mandibular 6 x 100)/77.2)

64. 64

65. Disadvantages of Bolton's analysis
• Does not take into account the sexual dymorphism of
maxillary canine widths.
• Study done on specific population.
65
study model

66. 6. ASHLEY HOWE’S ANALYSIS
• Hypothesis: crowding is due to deficiency in arch width not
perimeter
• Procedure:
• Determine Total Tooth Material (TTM) mesial to 7s using
dividers
• Determine Premolar Diameter (PMD) – buccal cusp to buccal
cusp of the 4s’
• Determine Premolar Basal Arch Width (PMBAW)
– Measure width from canine fossa to canine fossa. Canine fossa is
distal to the canine eminence.
– IPMBAW gives the width of the dental arch at the apical base or
junction between basal bone and alveolar process.
– If the canine fossa is not clearly distinguishable, the measurement
is made from one point 8mm below the crest of the IDP distal to
the canine

67. ASHLEY HOWE’S INFERENCE
• The PMBAW and the PMD are compared.
• If PMBAW is greater than PMD, then it is an indication for possible arch
expansion
• If PMBAW is less than PMD then arch expansion is not possible
• To achieve normal occlusion, PMBAW should be 44% of the sum of
mesiodistal widths of all teeth mesial to 7s (TTM)
PMBAW% = (PMBAW x 100)/TTM
If PMBAW% is 37% or less, need for extraction
If PMBAW% is 44% or more, no need for extraction
If PMBAW% is 37-44%, borderline case

68. MIXED DENTITION ANALYSIS
There are two approaches:
1. Those in which the sizes of unerupted cuspids and premolar are
estimated from radiographic images.
2. Those in which the sizes of unerupted cuspids and premolars
are derived from the knowledge of already erupted permanent
teeth in the mouth from probability tables.
68
study model

69. 1. MOYER’S MIXED DENTITION ANALYSIS
Principle:
Size of unerupted permanent cuspids and premolars are predicted
from the knowledge of the sizes of certain permanent teeth already
erupted in the mouth.
It predicts the combined mesio-distal width of 3, 4 and 5 based on
the sum of the four lower permanent incisors.
69
study model

70. STEPS IN MOYER’S ANALYSIS
• The sum of mesio-distal width of lower 4 incisors is obtained.
• The amount of space available for the 3,4 and 5 after incisor alignment is
determined by measuring the distance between the distal surface of lateral
incisor and the mesial surface of first permanent molar.
• The expected width of the 3, 4 and 5 is the predicted by referring to the
probability chart. (75% level of probability is considered reliable)
• The predicted tooth size of 3, 4 and 5 is compared with the arch length
available for them so as to determine the discrepancy.
• If predicted value is greater than the available arch length, crowding is
expected

71. 71
study model

72. 72

73. 2. HUCKABA ANALYSIS
• Principle: With any type of radiograph, it is necessary to compensate for
enlargement of radiographic image. This is done by measuring an object
that can be seen both in radiograph and on the cast, such as primary
molar tooth
• Proportional relationship should be established

74. PROCEDURE
• Obtain sum of mandibular incisors on cast
• Measure:
– Width of primary tooth on xray film – Y1
– Width of underlying permanent successor – X1
– Width of primary tooth on cast – Y
– Width of unerupted tooth - X
X = (X1*Y)/Y1
• The sum of the value obtained for the mandibular incisors on the cast and calculated
value for canines and premolars give Space required.
• Space available is obtained by measuring from mesial of 1st permanent molar to
mesial of 1st permanent molars
• Discrepancy is the difference

75. 3. TANAKA AND JOHNSTON ANALYSIS (1974)
• They developed a method to predict the width of the unerupted
canine and premolar using the width of lower incisors.
• This method has good accuracy despite a small bias of
overestimating the size of the unerupted tooth size.
• They have simplified the Moyer's 75% prediction table into
formulas.
75
study model

76. 76
study model

77. RECENT ADVANCES IN MODEL ANALYSIS
Cast analysis by E-models /3D digital models
Advantages : more accurate
: easy
:more information in relation to
1. Arch form
2. Determine asymmetric arch
3. Space analysis
4. Rotation and prediction.
77
study model

79. References
• Bhalagi-textbook of orthodontics
• Contemporary –textbook of orthodontics
• Bishara –textbook of orthodontics
79
study model

80. References:
• Singh, G. 2008. Textbook of Orthodontics. 2nd
edition. New Delhi: Unipress.
• Bhalaji – Textbook Of Orthodontics
• Contemporary – Textbook Of Orthodontics
• Bishara – Textbook Of Orthodontics