Model Analysis
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.indiandetalacad...
Contents
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Introduction
Definition
Model analysis
1) Permanent Dentition 2) Mixed Dentition
- Pont’s Index
- Moy...
Introduction





Success in orthodontic treatment – Diagnosis.
Many diagnostic aids are available today but study
mode...
Clinical
Examination

Functional
Analysis

Case History

Comprehensive diagnosis
Study Cast
Analysis

Radiographic
Examina...
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5
Definition


Model analysis is the study
of maxillary and mandibular
dental arches in all the
three planes of spaces
usin...
Study Model Fabrication

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7
OBJECTIVES OF IDEAL
ORTHODONTIC STUDY MODELS






Models accurately reproduce the teeth and their
surrounding soft tis...






Models are to be trimmed in such a way that the
occlusion shows by setting the models on their
backs.
Models are ...
USES OF STUDY MODELS








They enable the study of occlusion from all
aspects.
They enable accurate measurements to...








It makes possible to simulate treatment
procedures on the cast such as mock surgery.
Study models are useful t...
PARTS OF THE STUDY MODELS


Study models can be divided into two
parts:



The anatomic portion.



The artistic portio...
TOOTH SIZE-ARCH WIDTH
DISCREPANCY
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PONT’S ANALYSIS.
LINDERHARTH ANALYSIS
KORKHAUS ANALYSIS
ASLEY–HOWE ANALYSIS
E...
TOOTH SIZE-ARCH LENGTH
DISCREPENCY
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ARCH-PERIMETER ANALYSIS
NANCE-CAREY’S ANALYSIS
IRREGULAR INDEX
REE’S...
MIXED- DENTION ANALYSIS
(Estimating the size of unerupted teeth)
 MOYER’S ANALYSIS.
 TANAKA-JOHNSTON ANALYSIS.
 HIXON-O...
UPPER/LOWER TOOTH SIZE
DISHARMONY


BOLTON’S TOOTH RATIO ANALYSIS

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16
TOOTH-SHAPE DISHARMONY


PECK & PECK INDEX.

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17
PHOTOGRAPHIC ANALYSIS
OF STUDY MODEL
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STEROPHOTOGRAMETRY
OCCLUSOGRAMS
HOLOGRAPHIC IMAGE ANALYSIS

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COMPUTERIZED ANALYSIS
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OSCOPO
REFLEX METROGRAPHY

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19
Armamentarium
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

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a) Divider
b) Ruler
c) Wedge Ruler
d) Vernier Caliper
e) Brass Wire

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...
Measurements Required

a)
b)
c)
d)
e)
f)

Tooth Measurements
Centrals
Laterals
Canines
First Premolars
Second Premolars
F...
Pont’s Analysis




In 1909, Pont devised a method of predetermining
an “ideal” arch width based on the mesio-distal
wid...



a)

b)

c)

Pont also suggested that the maxillary arch be
expanded 1 to 2mm more during treatment
than his ideal to ...


Determination of sum of
incisors (S.I)



Determination of
measured premolar value
(M.P.V)



Determination of
measur...


Determination of
calculated premolar
value (C.P.V)



Determination of
calculated molar value
(C.M.V)

www.indiandetal...
Inference




If measured value is less than the calculated value,
then arch is narrow for the sum incisors width and
ne...
Drawbacks






Analysis is based on study of French population
and hence, its universal validity is questionable.
Maxi...




Mandibular arch form and mandibular intercanine
diameter have been repeatedly found to be more
reasonable treatment ...
Linder Harth analysis







Similar to Pont’s analysis.
A variation has been proposed to determine the
calculated pre...
Korkhaus Analysis





This analysis is similar to Pont’s analysis.
Korkhaus uses Linder Harth’s measurements.
An orth...


Introduces a third measurement from the
midpoint of inter- premolar line of upper arch to
a point in between the two ma...


For a particular width of incisors there is a
specific value of distance from the incision to the
inter premolar line a...
Korkhaus www.indiandetalacademy.com
Measurements.

33


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

w...
Arch perimeter Analysis






Many malocclusions are as a result of discrepancy
between arch length and tooth material....


Determination of arch
length.
Arch length anterior to
the first permanent
molar is measured
using a soft brass
wire.
Th...






In case of proclined anteriors, the wire is
passed along the cingulum of anterior teeth.
If the anterior teeth ar...


Determination of tooth
material.
The mesio-distal width
of the teeth anterior to
the first molars
(second premolars to
...
Determination of the Discrepancy.
The discrepancy refers to the difference between
the arch length and tooth material.
 I...
Drawbacks




This procedure of accessing arch length does not
appear to be clear-cut in border line cases.
The visualiz...
Peck and Peck Index




Tooth shape (mesio distal and faciolingual) is
determining factor in the presence and absence of...









Orthodontic Odontometry.
Crown dimensions more frequently reported are
the mesio distal diameter.
No curentl...




According to Peck and Peck, persons with ideal
incisal arrangement had smaller mesiodistal width
and comparatively l...


Index = M.D X 100
F.L/L.L



MD/FL index as a
numerical expression
of crown shape as
viewed incisally is
confined to t...
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45






Mean value for lower central incisor should be
88% to 92%.
Mean value for lower lateral incisor should be
90% to ...
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47






The reference table provides the computed value
of the MD/FL index, given the MD and FL crown
dimensions.
Example...




Reproximation: Tooth reproximation is a clinical
procedure involving the reduction, anatomic
recontouring, and prote...
Sanin and Savara Analysis


a)

b)

c)

Mesio distal crown-size relationships are decisive
variables in the search for,
F...




There is a direct relationship between the
magnitude of the crown-size
differences( regardless of the number of teet...




The purpose of their study was to examine the
possibility of using a norm of mesio distal size of
the permanent teet...
Mesio distal crown sizes of 51 boys and 50 girls of north west European
53
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ancestry selected fr...
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54


a)

b)

c)

Some of the characteristics that may be studied
with the assistance of the tables are,
The size of the maxi...






This analysis presents an effective way of
locating and analyzing crown-size discrepancies.
Crown size patterns d...
Ashley Howe’s Analysis




Ashley Howe considered tooth crowding to be
due to deficiency in arch width rather than arch
...
Howe’s analysis measurements.
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58


Determination of total
tooth material.
The mesio distal width
of all the teeth mesial to
the second permanent
molars is...


Determination of first
bicuspid coronal arch
width.( BIC.W)
This measurement is
the distance between
the summits of the...




Determination of basal
arch width( B.A.W)
above the maxillary first
bicuspids and below of
mandibular first
bicuspid...




The canine fossa is found diatal to the canine
eminence. The measurement of the width from
canine fossa of one side ...
The percentage
relationship of first
bicuspid width to tooth
material.
BIC.W = %
TTM
 The percentage
relationship of firs...


Determination of Basal
arch length.( B.A.L)
In the maxilla the
median line
measurement from
Downs A point
perpendicular...


In the mandibular arch
the measurement is
made from downs B
point to a mark on the
lingual surface of cast
as was incas...




Determination of the percentage of arch length
to the tooth material.
B.A.L = %
TTM
The percentage relationship is m...
Inference




Howe’s believed that the premolar basal arch
width ( B.A.W) which he called as the canine
fossa diameter s...


If the premolar basal
arch width is greater
than the premolar
coronal arch width
(B.A.W>BIC.W),
expansion of the
premol...
Advantages

3)

Howe’s analysis is useful in treatment planning
of problems with suspected apical base
deficiencies and de...
Wayne A. Bolton Analysis




Bolton pointed out that the extraction of one
tooth or several teeth should be done accordi...




To attain an optimum inter- arch dental
relationship, the maxillary tooth material should
approximate desirable rati...
Measurements





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Sum of mandibular 12.
Sum of maxillary 12.
Sum of mandibular 6.
Sum of maxillary 6.
Overall Rati...


1)

2)

Determination of overall Ratio.
According to Bolton, the sum of mesio distal
widths of the mandibular teeth ant...


1)

2)

Determination of anterior ratio.
The sum of mesio distal width of the
mandibular anteriors to the mesio distal ...
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75
Advantage & Disadvantages





When contemplating the extraction of four
premolars, it is useful, before selecting the ...
Irregular Index





Given by Robert M. Little.
Anterior dental crowding is perhaps the most
frequently occurring chara...
Method




The proposed scoring method involves
measuring the linear displacement of anatomic
contact points, of each ma...


Each of five
measurements
represents, in horizontal
linear distance between
the vertical projection of
the anatomic con...
Calculations/ Inference








The results of the irregularity index can be
correlated with the scale ranging from ...
Rees Analysis





Given by Denton J. Rees.
All the measurements are made on study
models which should be essentially a...
Method






A ruler is placed against the
side of the cast, at right
angles to the occlusal surface,
and a line is dra...






A piece of scotch tape 5 inches long is cut into strips
approximately 1/8th inch wide and a thin strip of tape is...
Calculations


Following chart permits a quick analysis on any
sets of casts.
UB to UT =1.5 to 5 - mean 3.5 - range 3.5
L...
Inference


1)

By comparing the average normals to the
measurements taken on the set up casts,
following points of diagn...
2)

3)

UB to LB.
If discrepancy exists, reduction of teeth and
base may be necessary in one arch, or if not
indicated, ex...
Diagnostic Set up






HD Kesling introduced the diagnostic set up
which is made from an extra set of trimmed
study mo...
Steps




Obtain an accurate
wax bite. Trim
posterior portion of
the bases of the casts
with the wax bite
interposed so ...




Insert a fine saw blade
through the hole and cut
up to the crest of the
gingival margin between
two of the teeth.
Cu...




Repeat this for all the
teeth to be cut off the
cast. Do not cut
through the contact
points. Cutting up to
the gingi...






It is best not to cut off all the teeth so that the
bite relationship can be kept.
A more accurate method involve...
Uses






Aids in treatment planning as it helps to visualize
tooth size arch length discrepancies and
determine wheth...
Space Analysis






To quantify the amount of crowding within the
arches.
Because treatment varies depending on the
se...




It requires a comparison between the amount
of space available for the alignment of
crowded teeth and amount of spac...
Method




1.

Space available
Accomplished by
measuring arch perimeter
from first molar to the other,
over the contact...
2.



By contouring piece
of wire to the line of
occlusion and then
straightening it out for
measurement.
The first metho...



Space Required
Done by measuring the
mesiodistal width of
each tooth from contact
point to point, and then
summing th...
Inference




If the sum of widths of the permanent teeth is
greater than the amount of available space,
there is an arc...


1.

2.



Space analysis carried out in this way is based
on two important assumptions:
The anteroposterior position o...
References


ORTHODONTICS
PRINCIPLES AND PRACTICE,
- GRABER T.M.







Handbook of orthodontics.
- ROBERT E. MOYERS.
...


Index for assessing toothe shape deviations.
Am. J. Orthod April 1972.



A method of assessing the proportional relat...





Disharmony in tooth size and its relation to the
analysis and treatment of malocclusion. Angle
orthod (28) 1958.
A...
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103
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Model analysis in orthodontics /certified fixed orthodontic courses by Indian dental academy

  1. 1. Model Analysis INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandetalacademy.com 1
  2. 2. Contents      Introduction Definition Model analysis 1) Permanent Dentition 2) Mixed Dentition - Pont’s Index - Moyer’s - Linder Harth’s - Hixon & Old Fathther’s - Korkhaus - Nance carey’s - Arch Perimeter - Huckaba’s - Bolton’s - Total Space analysis etc. - Ashley Howe’s etc. Recent Advances Conclusion www.indiandetalacademy.com 2
  3. 3. Introduction    Success in orthodontic treatment – Diagnosis. Many diagnostic aids are available today but study models are oldest. Model analysis is an adjunct in diagnosis and treatment planning. It should hence be correlated with the other data in the diagnosis before formulating any treatment plan. www.indiandetalacademy.com 3
  4. 4. Clinical Examination Functional Analysis Case History Comprehensive diagnosis Study Cast Analysis Radiographic Examination www.indiandetalacademy.com RoentgenoCephaloMetricAnalysis Photographic Analysis 4
  5. 5. www.indiandetalacademy.com 5
  6. 6. Definition  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. www.indiandetalacademy.com 6
  7. 7. Study Model Fabrication www.indiandetalacademy.com 7
  8. 8. OBJECTIVES OF IDEAL ORTHODONTIC STUDY MODELS    Models accurately reproduce the teeth and their surrounding soft tissues. Models are to be trimmed so that they are symmetrical and also the asymmetrical arch form can be readily recognized. Models should trimmed so to meet the proposed ideal measurement. www.indiandetalacademy.com 8
  9. 9.    Models are to be trimmed in such a way that the occlusion shows by setting the models on their backs. Models are to have clean, smooth, bubble free surfaces with sharp angles where the cuts meet. The finished models will be treated with a soap solution to give a glassy mar-proof finish. www.indiandetalacademy.com 9
  10. 10. USES OF STUDY MODELS     They enable the study of occlusion from all aspects. They enable accurate measurements to be made in a dental arch. They help in assessment of the treatment progress. They help in motivation of the patient and to explain the treatment plan. www.indiandetalacademy.com 10
  11. 11.     It makes possible to simulate treatment procedures on the cast such as mock surgery. Study models are useful to transfer records in case the patient is to be treated by another clinician. Study models helps to determine the midline discrepancy. It also helps in assessment of surrounding tissue. www.indiandetalacademy.com 11
  12. 12. PARTS OF THE STUDY MODELS  Study models can be divided into two parts:  The anatomic portion.  The artistic portion. www.indiandetalacademy.com 12
  13. 13. TOOTH SIZE-ARCH WIDTH DISCREPANCY      PONT’S ANALYSIS. LINDERHARTH ANALYSIS KORKHAUS ANALYSIS ASLEY–HOWE ANALYSIS ETC . www.indiandetalacademy.com 13
  14. 14. TOOTH SIZE-ARCH LENGTH DISCREPENCY          ARCH-PERIMETER ANALYSIS NANCE-CAREY’S ANALYSIS IRREGULAR INDEX REE’S ANALYSIS. DIAGNOSTIC SET UP LAARRY WHITE ANALYSIS SANIN & SAVARA ANALYSIS TOTAL SPACE ANALYSIS TWEED METHOD www.indiandetalacademy.com 14
  15. 15. MIXED- DENTION ANALYSIS (Estimating the size of unerupted teeth)  MOYER’S ANALYSIS.  TANAKA-JOHNSTON ANALYSIS.  HIXON-OLD FATHER METHOD.  HUCKABA ANALYSIS. www.indiandetalacademy.com 15
  16. 16. UPPER/LOWER TOOTH SIZE DISHARMONY  BOLTON’S TOOTH RATIO ANALYSIS www.indiandetalacademy.com 16
  17. 17. TOOTH-SHAPE DISHARMONY  PECK & PECK INDEX. www.indiandetalacademy.com 17
  18. 18. PHOTOGRAPHIC ANALYSIS OF STUDY MODEL    STEROPHOTOGRAMETRY OCCLUSOGRAMS HOLOGRAPHIC IMAGE ANALYSIS www.indiandetalacademy.com 18
  19. 19. COMPUTERIZED ANALYSIS   OSCOPO REFLEX METROGRAPHY www.indiandetalacademy.com 19
  20. 20. Armamentarium      a) Divider b) Ruler c) Wedge Ruler d) Vernier Caliper e) Brass Wire www.indiandetalacademy.com 20
  21. 21. Measurements Required  a) b) c) d) e) f) Tooth Measurements Centrals Laterals Canines First Premolars Second Premolars First Molar  a) b) c) d) e) f) g) Other measurements Sum of 2 to 2 Tooth material ( Sum of 5 to 5 ) Total Tooth Material ( Sum of 6 to 6 ) Arch Width Arch Perimeter PMD PMBAW etc. www.indiandetalacademy.com 21
  22. 22. Pont’s Analysis   In 1909, Pont devised a method of predetermining an “ideal” arch width based on the mesio-distal widths of the crowns of the maxillary incisors. Pont 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. A clinical evaluation. Angle, Orthod ; 1970. www.indiandetalacademy.com 22
  23. 23.   a) b) c) Pont also suggested that the maxillary arch be expanded 1 to 2mm more during treatment than his ideal to allow for relapse. Pont’s analysis helps in, Determining whether dental arch is narrow or is normal. Determining the need for lateral arch expansion. Determining how much expansion is possible at the premolar and molar regions. www.indiandetalacademy.com 23
  24. 24.  Determination of sum of incisors (S.I)  Determination of measured premolar value (M.P.V)  Determination of measured molar value (M.M.V) www.indiandetalacademy.com 24
  25. 25.  Determination of calculated premolar value (C.P.V)  Determination of calculated molar value (C.M.V) www.indiandetalacademy.com 25
  26. 26. Inference   If measured value is less than the calculated value, then arch is narrow for the sum incisors width and needs expansion. If measured value is greater than the calculated value, then the arch is wider and there is no scope for the expansion. www.indiandetalacademy.com 26
  27. 27. Drawbacks    Analysis is based on study of French population and hence, its universal validity is questionable. Maxillary laterals are the most commonly missing and malformed teeth (i,e Peg shaped). Does not consider skeletal mal-relationships and relationship of teeth to the supporting bone. www.indiandetalacademy.com 27
  28. 28.   Mandibular arch form and mandibular intercanine diameter have been repeatedly found to be more reasonable treatment guides for both maxillary and mandibular ultimate arch widths than the pont’s index. Pont’s index is naive in concept and of little use in rational treatment planning. www.indiandetalacademy.com 28
  29. 29. Linder Harth analysis     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 Where S.I is sum of mesio distal widths of incisors. www.indiandetalacademy.com 29
  30. 30. Korkhaus Analysis     This analysis is similar to Pont’s analysis. Korkhaus uses Linder Harth’s measurements. An orthometer was devised by Korkhaus and from that ideal arch width in premolar region and molar region can be determined. The perpendicular distance from the interpremolar line to the incision for a given S.I can be determined. www.indiandetalacademy.com 30
  31. 31.  Introduces a third measurement from the midpoint of inter- premolar line of upper arch to a point in between the two maxillary incisors. Measurements. a) Arch width in premolar region & b) in molar Region. c) Perpendicular distance from the midpoint of inter premolar line to incision. www.indiandetalacademy.com 31
  32. 32.  For a particular width of incisors there is a specific value of distance from the incision to the inter premolar line according to Korkhaus.  Inference : a) This analysis tells about the arch width. b) If the perpendicular distance is more than ideal, then anterior teeth are proclined. c) If the perpendicular distance is less than the ideal, then the anterior teeth are retroclined. www.indiandetalacademy.com 32
  33. 33. Korkhaus www.indiandetalacademy.com Measurements. 33
  34. 34.  For the values noted the mandibular value (Ll) should be equal to the maxillary value (Lu) in millimeters minus 2mm. www.indiandetalacademy.com 34
  35. 35. Arch perimeter Analysis    Many malocclusions are as a result of discrepancy between arch length and tooth material. This analysis helps us to find the difference between the basal bone and the tooth material i,e in determining the extent of Discrepancy. The same analysis is called “Carey’s Analysis” in the lower cast. www.indiandetalacademy.com 35
  36. 36.  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. www.indiandetalacademy.com 36
  37. 37.    In case of proclined anteriors, the wire is passed along the cingulum of anterior teeth. If the anterior teeth are retroclined, the brass wire is passed labial to the teeth. If the anterior teeth are well aligned, the wire is passed over the incisal edges of the anterior teeth. www.indiandetalacademy.com 37
  38. 38.  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. www.indiandetalacademy.com 38
  39. 39. Determination of the Discrepancy. The discrepancy refers to the difference between the arch length and tooth material.  Inference.  www.indiandetalacademy.com 39
  40. 40. Drawbacks   This procedure of accessing arch length does not appear to be clear-cut in border line cases. The visualized form will vary with the individual who is contouring the wire. www.indiandetalacademy.com 40
  41. 41. Peck and Peck Index   Tooth shape (mesio distal and faciolingual) is determining factor in the presence and absence of lower incisor crowding. Harvey peck and Sheldon Peck present a new method of detecting and evaluating tooth shape deviations of the mandibular incisors. Index for assessing tooth shape deviations. Am. J. Orthod April 1972 www.indiandetalacademy.com 41
  42. 42.      Orthodontic Odontometry. Crown dimensions more frequently reported are the mesio distal diameter. No curently used clinical analysis employs or even takes into consideration the facio lingual tooth dimension. Both MD and FL dimensions appear to be related to incisor alignment. This index incorporates both dimensions for orthodontic tooth size analysis. www.indiandetalacademy.com 42
  43. 43.   According to Peck and Peck, persons with ideal incisal arrangement had smaller mesiodistal width and comparatively larger faciolingual width than in persons with incisal crowding. On the basis of this observation, Peck and Peck suggested certain clinical guidelines. www.indiandetalacademy.com 43
  44. 44.  Index = M.D X 100 F.L/L.L  MD/FL index as a numerical expression of crown shape as viewed incisally is confined to the mandibular incisors. www.indiandetalacademy.com 44
  45. 45. www.indiandetalacademy.com 45
  46. 46.    Mean value for lower central incisor should be 88% to 92%. Mean value for lower lateral incisor should be 90% to 95%. Inference : a) Lower incisors within or below these ranges are considered favorably shaped. b) Lower incisors with MD/FL index above these ranges considered to have crown shape deviations contributing to crowding phenomenon. www.indiandetalacademy.com 46
  47. 47. www.indiandetalacademy.com 47
  48. 48.    The reference table provides the computed value of the MD/FL index, given the MD and FL crown dimensions. Example: Mandibular right lateral incisor having MD=6.0 and FL=6.3, will have MD/FL index of 95. In a given case if the value is more, then authors recommend Proximal stripping or Tooth Reproximation. www.indiandetalacademy.com 48
  49. 49.   Reproximation: Tooth reproximation is a clinical procedure involving the reduction, anatomic recontouring, and protection of the mesial and/or distal enamel surfaces of a permanent tooth. A consideration of tooth shape and the MD/FL index appears essential for the successful orthodontic management of the incisor irregularities. www.indiandetalacademy.com 49
  50. 50. Sanin and Savara Analysis  a) b) c) Mesio distal crown-size relationships are decisive variables in the search for, Factors associated with the development of occlusal and facial irregularities. The possible effects of discrepancies upon interdigitation during after orthodontic treatment, The isolation of discrepant teeth of minor tooth malocclusions that may be treated in part by selective mesio distal grinding and minor tooth movement. An analysis of permanent mesio distal crown size. Am.J.Orthod (59) 1971. www.indiandetalacademy.com 50
  51. 51.   There is a direct relationship between the magnitude of the crown-size differences( regardless of the number of teeth involved) and the presence of occlusal irregularities. There is also a direct relationship between number of discrepant teeth( regardless of the magnitude of the crown size differences) and the presence of occlusal irregularities. www.indiandetalacademy.com 51
  52. 52.   The purpose of their study was to examine the possibility of using a norm of mesio distal size of the permanent teeth for locating and analyzing crown-size discrepancies. The analysis proposed would contribute to a more complete evaluation of intra-oral etiologic factors and a more precise diagnosis and prognosis of the dental problem. www.indiandetalacademy.com 52
  53. 53. Mesio distal crown sizes of 51 boys and 50 girls of north west European 53 www.indiandetalacademy.com ancestry selected from the university of Oregon dental school.
  54. 54. www.indiandetalacademy.com 54
  55. 55.  a) b) c) Some of the characteristics that may be studied with the assistance of the tables are, The size of the maxillary teeth as a whole relative to the size of the mandibular teeth as a whole, The size of the individual teeth or groups of teeth relative to individual teeth or groups of antagonist teeth, and Discrepancies between right and left sides and, in all cases, the direction of the discrepancy if present( small, average or large) and their magnitude. www.indiandetalacademy.com 55
  56. 56.    This analysis presents an effective way of locating and analyzing crown-size discrepancies. Crown size patterns differ greatly, even among good occlusions. The complexity of interdigitation in orthodontic treatment is emphasized. www.indiandetalacademy.com 56
  57. 57. Ashley Howe’s Analysis   Ashley Howe considered tooth crowding to be due to deficiency in arch width rather than arch length. He found 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. A Polygon Portrayal of coronal and basal arch dimensions in the horizontal plane. Am. J. Orthod. Nov,1954. www.indiandetalacademy.com 57
  58. 58. Howe’s analysis measurements. www.indiandetalacademy.com 58
  59. 59.  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). www.indiandetalacademy.com 59
  60. 60.  Determination of first bicuspid coronal arch width.( BIC.W) This measurement is the distance between the summits of the buccal cusps of the first bicuspids. www.indiandetalacademy.com 60
  61. 61.   Determination of basal arch width( B.A.W) above the maxillary first bicuspids and below of mandibular first bicuspids. Basal arch width will be greater than the coronal arch. www.indiandetalacademy.com 61
  62. 62.   The canine fossa is found diatal to the canine eminence. The measurement of the width from canine fossa of one side to the canine fossa of other gives the premolar basal arch width ( P.M.B.A.W). 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. www.indiandetalacademy.com 62
  63. 63. The percentage relationship of first bicuspid width to tooth material. BIC.W = % TTM  The percentage relationship of first bicuspid basal arch width to tooth material. B.A.W = % TTM  www.indiandetalacademy.com 63
  64. 64.  Determination of Basal arch length.( B.A.L) In the maxilla the median line measurement from Downs A point perpendicular to the occlusal plane , then to the median point on a line connecting the distal surface of the first molar. www.indiandetalacademy.com 64
  65. 65.  In the mandibular arch the measurement is made from downs B point to a mark on the lingual surface of cast as was incase of the maxilla. www.indiandetalacademy.com 65
  66. 66.   Determination of the percentage of arch length to the tooth material. B.A.L = % TTM The percentage relationship is more important than the actual measurement. www.indiandetalacademy.com 66
  67. 67. Inference   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. www.indiandetalacademy.com 67
  68. 68.  If the premolar basal arch width is greater than the premolar coronal arch width (B.A.W>BIC.W), expansion of the premolars may be undertaken safely. www.indiandetalacademy.com 68
  69. 69. Advantages 3) Howe’s analysis is useful in treatment planning of problems with suspected apical base deficiencies and deciding to whether to, Extract teeth, Widen the dental arch, or Expand rapidly the palate.  Howe’s analysis is applicable to each arch.  1) 2) www.indiandetalacademy.com 69
  70. 70. Wayne A. Bolton Analysis   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. Bolton’s analysis helps to determine the disproportion between the sizes of the maxillary and the mandibular teeth. Disharmony in tooth size and its relation to the analysis and treatment of malocclusion. Angle orthod (28) 1958. www.indiandetalacademy.com 70
  71. 71.   To attain an optimum inter- arch dental relationship, the maxillary tooth material should approximate desirable ratios, as compared to the mandibular tooth material. Average proportion between upper and lower teeth in overall and anterior region helps to create a normal overjet and overbite. www.indiandetalacademy.com 71
  72. 72. Measurements       Sum of mandibular 12. Sum of maxillary 12. Sum of mandibular 6. Sum of maxillary 6. Overall Ratio. Anterior Ratio. www.indiandetalacademy.com 72
  73. 73.  1) 2) Determination of overall Ratio. According to Bolton, the sum of mesio distal widths of the mandibular teeth anterior to the second permanent molar is 91.3% the mesio distal widths of the maxillary teeth mesial to the second molars. Overall Ratio = Sum of mandibular 12 X 100 Sum of maxillary 12 If ratio is less than 91.3%, maxillary tooth material excess. If ratio is more than 91.3%, Mandibular tooth material excess. www.indiandetalacademy.com 73
  74. 74.  1) 2) Determination of anterior ratio. 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 X 100 Sum of maxillary 6 If ratio is less than 77.2%, maxillary anterior excess. If ratio is more than 77.2%, Mandibular anterior excess. www.indiandetalacademy.com 74
  75. 75. www.indiandetalacademy.com 75
  76. 76. Advantage & Disadvantages    When contemplating the extraction of four premolars, it is useful, before selecting the teeth for extraction, to ascertain the effects of various extraction combinations on these ratios. Study done on specific population. Does not take into account the sexual dimorphism in the maxillary canine widths. www.indiandetalacademy.com 76
  77. 77. Irregular Index    Given by Robert M. Little. Anterior dental crowding is perhaps the most frequently occurring characteristics of malocclusion. Adjectives such as mild, moderate and severe etc. are descriptively helpful but still allow a wide range of interpretation. The irregularity index ; A quantitative score of mandibular anterior alignment. AJO, Vol. 68 : 1975. www.indiandetalacademy.com 77
  78. 78. Method   The proposed scoring method involves measuring the linear displacement of anatomic contact points, of each mandibular incisors from the adjacent tooth anatomic points. The sum of these five displacements represent the degree of anterior irregularity. www.indiandetalacademy.com 78
  79. 79.  Each of five measurements represents, in horizontal linear distance between the vertical projection of the anatomic contact points of adjacent teeth. www.indiandetalacademy.com 79
  80. 80. Calculations/ Inference       The results of the irregularity index can be correlated with the scale ranging from 0 to 10 formed by the subjective ranking. 0 – Perfect Alignment. 1,2,3 - Minimum irregularity. 4,5,6 - Moderate irregularity. 7,8,9 – Severe irregularity. 10 to 20 – Very severe irregularity. www.indiandetalacademy.com 80
  81. 81. Rees Analysis    Given by Denton J. Rees. All the measurements are made on study models which should be essentially accurate. Special attention given to the extension into the mucobuccal fold in order to approximate basal bone to at least the distal of first permanent molar. A method of assessing the proportional relation of apical bases & contact diameters of teeth. AJO, VOL: 39: 1953. www.indiandetalacademy.com 81
  82. 82. Method    A ruler is placed against the side of the cast, at right angles to the occlusal surface, and a line is drawn at the mesial contact point of each first permanent molar. The third line is drawn through the midline contact of upper and lower central incisor. This line is extended to a point 8-10mm from the gingival margin in the apical direction. www.indiandetalacademy.com 82
  83. 83.    A piece of scotch tape 5 inches long is cut into strips approximately 1/8th inch wide and a thin strip of tape is then placed so that one end is superimposed on the molar mark. The tape is pressed firmly to the cast to pass through the incisor point, and then trough the opposite molar point. The teeth on each cast from second premolar to second premolar are recorded at their greatest mesio distal diameter. www.indiandetalacademy.com 83
  84. 84. Calculations  Following chart permits a quick analysis on any sets of casts. UB to UT =1.5 to 5 - mean 3.5 - range 3.5 LB to LT =2 to 7 - mean 4.5 - range 5 UB to LB =3 to 9.5 - mean 6.5 - range 6.5 UT to LT =5 to 10 - mean 7.5 - range 5 Where U = MAXILLA; L= MANDIBLE; B= APICAL BASE; T= TOOTH CROWN www.indiandetalacademy.com 84
  85. 85. Inference  1) By comparing the average normals to the measurements taken on the set up casts, following points of diagnostic importance can be derived. UB to UT or LB to LT. If discrepancy exists, in borderline cases, internal and external muscular forces, facial esthetics, and other factors will determine the treatment plan. www.indiandetalacademy.com 85
  86. 86. 2) 3) UB to LB. If discrepancy exists, reduction of teeth and base may be necessary in one arch, or if not indicated, expansion of other arch is the only alternative. UT to LT. If discrepancy beyond normal range are present, tooth mass is reduced in one arch or increased in the other by judicious placement of crown or inlays. www.indiandetalacademy.com 86
  87. 87. Diagnostic Set up    HD Kesling introduced the diagnostic set up which is made from an extra set of trimmed study models. Also called as Prognostic Set Up, as it helps to ascertain precisely the amount and direction of each tooth to be moved. For visualizing space problems in three dimensions in the permanent dentition, the teeth are cut off from the cast and reset in a more desirable position. The Diagnostic Set-up with consideration of third dimension Am. J. Orhtod, 42 ; 740-748, 1956 www.indiandetalacademy.com 87
  88. 88. Steps   Obtain an accurate wax bite. Trim posterior portion of the bases of the casts with the wax bite interposed so that the bases are flush. Drill a whole trough the alveolar portion of the cast well below the gingival margin of the teeth. www.indiandetalacademy.com 88
  89. 89.   Insert a fine saw blade through the hole and cut up to the crest of the gingival margin between two of the teeth. Cut along the line of the arch, well beneath the gingival margin of the teeth, and come up again at the point of the gingival crest below the contact point on the opposite side of the tooth. www.indiandetalacademy.com 89
  90. 90.   Repeat this for all the teeth to be cut off the cast. Do not cut through the contact points. Cutting up to the gingival crest will permit gentle breaking of plaster without damage. Align the teeth and wax them into the desired positions. www.indiandetalacademy.com 90
  91. 91.    It is best not to cut off all the teeth so that the bite relationship can be kept. A more accurate method involves taking a wax bite in the retruded contact position, mounting the casts on the adjustable articulator, and finishing the diagnostic set up within the limits of the jaw relationships thus imposed. One may combine the cephalometric analysis and prediction of incisal positioning and angulations with the prognostic set up. www.indiandetalacademy.com 91
  92. 92. Uses    Aids in treatment planning as it helps to visualize tooth size arch length discrepancies and determine whether extraction is required or not. The effect of extraction and tooth movement following it on occlusion can be visualized. It also acts as a motivational tool as the improvements in tooth positions can be shown to the patient. www.indiandetalacademy.com 92
  93. 93. Space Analysis    To quantify the amount of crowding within the arches. Because treatment varies depending on the severity of the crowding. Principle : Since malaligned and crowded teeth usually result from lack of space, this analysis is primarily of space within the arches. www.indiandetalacademy.com 93
  94. 94.   It requires a comparison between the amount of space available for the alignment of crowded teeth and amount of space required to align them properly. Analysis can be done either directly on the dental casts or computer after appropriate digitization of the arch and tooth dimensions. www.indiandetalacademy.com 94
  95. 95. Method    1. Space available Accomplished by measuring arch perimeter from first molar to the other, over the contact points of posterior teeth and incisal edges of anteriors. There are two basic ways: By dividing the dental arch into segments that can be measured as straight line approximations of the arch. www.indiandetalacademy.com 95
  96. 96. 2.  By contouring piece of wire to the line of occlusion and then straightening it out for measurement. The first method is preferred for manual calculation because of its greatest reliabilty. www.indiandetalacademy.com 96
  97. 97.   Space Required Done by measuring the mesiodistal width of each tooth from contact point to point, and then summing the widths of individual teeth. www.indiandetalacademy.com 97
  98. 98. Inference   If the sum of widths of the permanent teeth is greater than the amount of available space, there is an arch perimeter space deficiency and crowding would occur. If space available is larger than the space required (excess space), gaps between some teeth would be expected. www.indiandetalacademy.com 98
  99. 99.  1. 2.  Space analysis carried out in this way is based on two important assumptions: The anteroposterior position of the incisors is correct ( i,e the incisors are neither excessively protrusive nor retrusive), and The space available will not change because of growth. Neither assumptions can be taken for granted. www.indiandetalacademy.com 99
  100. 100. References  ORTHODONTICS PRINCIPLES AND PRACTICE, - GRABER T.M.    Handbook of orthodontics. - ROBERT E. MOYERS. Contemporary orthodontics. - WILLIAM R. PROFFIT. Orthodontics current principles and concepts. - THOMAS M. GRABER & Vanarsdall www.indiandetalacademy.com 100
  101. 101.  Index for assessing toothe shape deviations. Am. J. Orthod April 1972.  A method of assessing the proportional relation of apical bases & contact diameters of teeth. AJO, VOL: 39: 1953.  Accurate arch – Discrepancy measurements. AJO, Vol. 72: 1977.  The irregularity index ; A quantitative score of mandibular anterior alignment. AJO, Vol. 68 : 1975. www.indiandetalacademy.com 101
  102. 102.    Disharmony in tooth size and its relation to the analysis and treatment of malocclusion. Angle orthod (28) 1958. A Polygon Portrayal of coronal and basal arch dimension in the horizontal plane. Am. J. Orthod. Nov,1954. An analysis of permanent mesio distal crown size. Am.J.Orthod (59) 1971. www.indiandetalacademy.com 102
  103. 103. www.indiandetalacademy.com 103

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