Model analysis in orthodontics presentation

this presentation gives a brief overview of model analysis

1. Model
Analysis
Dr Ridhi Kothari Tyagi

2. Introduction
•Model analysis is one of the essential diagnostic aids in
orthodontic practice.
•Help us to visualize the patient’s occlusion from all
aspects.

3. Armamentarium for model analysis

4. Analysis used in permanent dentition
•PONTS ANALYSIS
•LINDER HARTH INDEX  
•KORKHAUS ANALYSIS
•ARCH PERIMETER ANALYSIS (upper cast)
•CAREY’S ANALYSIS
•BOLTON'S ANALYSIS
•ASHLEY HOWE'S ANALYSIS
•PECK AND PECK INDEX
•SANIN – SAVARA ANALYSIS

5. Analysis used in mixed dentition

• MOYERS MIXED DENTITION ANALYSIS
• HUCKBA’S ANALYSIS
• HIXON AND OLDFATHER’S METHOD
• NANCE CAREY’S ANALYSIS
• TANAKA AND JOHNSTON

6. PONTS ANALYSIS
Ponts (1909)
Helps in:
a. Determining dental arch width.
b. Determining the need of arch expansion.
c. Determining amount of possible expansion.

7. Procedure 
a. Determination of sum of incisors (SI)
Sum of mesio-distal width of the 4 maxillary incisors

8. b. Determination of calculated premolar value (CPV)
CPV or the expected arch width in the premolar region is
determined by the formula
S.I. x 100
80
c. Determination of calculated molar value (CMV)
CMV or the expected arch width in the molar region is determined
by the formula
S.I. x 100
64

9. d. Determination of measured premolar value (MPV)
Width of the arch in the premolar region from the distal pit of
one upper first premolar to the distal pit of the opposite first
premolar

10. 4. Determination of measured molar value (MMV)
The width of the arch in the molar region from the mesial pit
of one upper first molar to the mesial pit of the opposite first
molar

11. Inference
•calculated value is greater than the measured value
then the arch is narrow and arch needs expansion.
•If the measured value is greater than the calculated
value then the arch is wider and there is no scope for
expansion.
 

12. Draw back of Pont’s analysis 
A) Analysis is based on the study of French population.
B)
 Analysis does not consider the alignment of teeth.
C) Analysis does not consider malformations of tooth.

13. LINDER HARTH INDEX
This analysis is very similar to Pont's analysis except that
a new formula has been proposed to determine the
calculated premolar value.
The calculated premolar value is determined using the
formula,
S.I. x 100
85

14. KORKHAUS ANALYSIS
This analysis is also similar to Pont's analysis.
lt makes use of the Linder Harth's formula to determine the
ideal arch width in the premolar and molar region.
In addition with this Korkhaus analysis uses a new third
measurement

15. That is from the midpoint of the inter-premolar line to a
point in between the incisal edges of two maxillary
incisors called incision.

16. According to Korkhaus, for a given width of upper incisors a
specific value of the distance between the midpoints of
inter- premolar line to the point between the two maxillary
incisors should exist.
Inference
An increase in this measurement denotes proclined upper
anterior teeth while a decrease in this value denotes
retroclined upper anteriors.
 

17. Arch perimeter analysis
(Carey’s analysis)
Many malocclusions occur as a result of discrepancy
between arch length and tooth material. Carey’s analysis
helps in determining the extent of discrepancy. It is
performed on the lower cast.
The same analysis on the upper arch called Arch
Perimeter Analysis.

18. Procedure
a. Determination of arch length
measured using a soft brass wire.From the mesial surface of the
first permanent molar of one side to the opposite first permanent
molar.

19. In case of proclined anteriors the wire is passed along the
cingulum of anterior teeth.
If the anterior teeth are retroclined, the brass wire in the
anterior segment passes labial to the teeth.
If the anterior teeth are well aligned the wire passes over the
incisal edge of anteriors.
 

20. b. Determination of tooth material
The mesio-distal width of the teeth anterior to the first molars is
measured and summed up.

21. Inference
If tooth material is more than the space available then there
can be crowding due to space shortage.
If tooth material is less than the space available then there
can be spacing due to excess space.

22. Depending on this suggested treatment planning is,
a.If the discrepancy is 0 to 2.5 mm, it indicates minimum
tooth material excess. In such cases proximal stripping
can be carried out to reduce the tooth material.

b. If the discrepancy is between 2.5 to 5mm it indicates the
need to extract the second pre molars.
c.
  If the discrepancy of more than 5mm indicates the need to
extract the first pre molars.

23. BOLTON'S ANALYSIS

Tooth size is an important factor to be taken into
consideration in orthodontic diagnosis and treatment
planning.
According to Bolton there exists a ratio between the
mesio-distal widths of maxillary and mandibular teeth. The
Bolton's analysis helps in determining disproportion in size
between maxillary and mandibular teeth.

24. Procedure
a. Sum of mandibular 12
The mesio-distal width of all the teeth mesial to the
mandibular second permanent molars is measured and added

25. b. Sum of maxillary 12
The mesio-distal width of all the teeth mesial to the maxillary
second permanent molars is measured and summed up.

26. c. Determination of overall ratio
The overall ratio of maxillary tooth to mandibular tooth is
determined by using the formula
Sum of mandibular 12 x 100
Overall ratio =
Sum of maxillary 12

27. According to Bolton, the sum of mesio-distal widths of the
mandibular teeth anterior to the second permanent molars
is 91.3% the mesio-distal width of the maxillary teeth mesial
to the second molars.

28. If overall ratio is less than 91.3%, it indicates maxillary tooth
material excess. The amount of maxillary excess is determined
using the formula :
 
Sum of mandibular 12 x 100
Sum of maxillary 12 - .
91.3
If the overall ratio is more than 91.3%. It indicates mandibular
tooth material excess. The amount of excess can be determined
by the formula
: . Sum
of maxillary 12 x 91.3
sum of mandibular 12-
.
100

29. d. Sum of mandibular 6
The mesio-distal width of all the teeth mesial to the
mandibular first premolars is measured and summed up.

30. e. Sum of maxillary 6
The mesio-distal width of all the teeth mesial to the maxillary
first premolars is measured and summed up.

31. f. Determination of anterior ratio
The anterior ratio is determined using the following formula:
Sum of mandibular 6 x 100
Anterior ratio = Sum of maxillary 6
 
According to Bolton sum of mesio-distal width of the
mandibular anteriors should be 77.2% of mesio-distal width of
the maxillary anteriors.

32. If the anterior ratio is less than 77.2% it indicates maxillary
anterior excess. The amount of maxillary anterior excess is
determined by
Sum of maxillary 6= sum of mandibular 6 x 100
77.2
 
If the anterior ratio is more than 77.2 %, it indicates mandibular
anterior excess. The amount of mandibular anterior excess is
determined by
 
Sum of mandibular 6= sum of maxillary 6 x 77.2
100

33. 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 the total width of the 12 teeth
anterior to the second molars and the width of the dental arch
in the first premolar region.

34. Procedure
a. Determination of total tooth material (T.T.M.)
The mesio-distal width of all the teeth mesial to the maxillary
second permanent molars is measured and added

35. b. Determination of premolar diameter (P.M.D.)
The premolar diameter refers to the arch width from the tip of
the buccal cusp of one first premolar to the tip of buccal cusp
of the opposite first premolar.

36. c. Determination of premolar basal arch width
(PMBAW)
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 distal to canine eminence.
If the canine fossa is not clearly distinguishable the
measurement is made from a point that is 8 mm below the
crest of the inter-dental papilla distal to the canine.

37. Inference
The P.M.B.A.W. and the P.M.D. are compared.
If the P.M.B.A.W is greater than the P.M.D., then it is an
indication that arch expansion is possible.
If on the other hand the P.M.B.A.W is less than P.M.D.,
then arch expansion is not possible.

38. According to Ashley Howe, to achieve normal occlusion with a
full complement of teeth the basal arch width at the premolar
region should be 44% the sum of mesio-distal widths of all the
teeth mesial to the second permanent molar (total tooth
material).
This ratio is called the premolar basal arch width percentage.
It is determined using the formula:
P.M.BA.W% = P.M.BA.W x 100
T.T.M.

39. a. If P.M.B.A.W % is 37% or less, it indicates a need
for extraction.
b. If P.M.B.A.W % is 44% or more, the case can possibly
be treated without extracting any teeth.
c. If P.M.B.A.W % is 37 - 44%, the case is referred to as a
borderline case.

40. Peck and Peck analysis index
It is done in lower arch in persons with incisal crowding. On
basis of observation, Peck and Peck suggested certain
clinical guidelines.
Procedure
1. calculate mesio-distal widths of mandibular incisors
individually called (M.D.).
2. calculate labio-lingual width of mandibular incisors
individually called (L.L.).

41. 3. Mean value is calculated by the formula
M.D. X 100
L.L.
According to peck and peck
•Mean value for lower central incisor should be 88 to 92%.
•Mean value for lower lateral incisor should be 90 to 95%.
Inference
If the value for a given case is more than the mean value
proximal stripping is indicated.

42. Sanin-Savara tooth size analysis
It makes use of precise mesio-distal measurements of the
crown size of each tooth by appropriate tables of tooth size
distribution in the population and a chart for plotting patient’s
measurements.
The teeth should be measured with a tooth measuring gauge
i.e finely pointed Boley gauge and compared.

43. MIXED DENTITION
ANALYSIS

44. Mixed dentition period is the best time to analyse and predict
the future dental arch condition thereby preventing any
malocclusion that may occur in permanent dentition.
 
For this purpose various authors have suggested
different techniques to determine the space available and the
space required for the permanent dentition to erupt and this is
called mixed dentition space analysis.
 

45. Indications for a mixed dentition analysis

Premature loss of primary canine
Rotation or blocking of permanent teeth
Ectopic eruption of permanent first molars.
Distal terminal plane relationships
Cross bite

46. The purpose of a mixed dentition analysis is to evaluate the
amount of space available in the arch for the erupting
permanent canines and premolars.

47. MOYERS MIXED DENTITION ANALYSIS
In this analysis the size of the unerupted permanent cuspids
and premolars are predicted from the knowledge of the sizes
of certain permanent teeth already erupted in the mouth.
The Moyer's mixed dentition analysis predicts the combined
mesio-distal width of 3, 4 and 5 based on the sum of the
widths of the four lower permanent incisors.

48. The mesio-distal width of the four lower incisors are measured
and summed up.
The amount of space available for the 3, 4 and 5 after incisor
alignment is detetmined by measuring the distance between
the distal surface of lateral incisor and the mesial surface of
first permanent molar.

49. Based on the mesio-distal width of the four mandibular
incisors, the expected width of the canines, first and second
premolars are predicted by referring the probability chart.
While doing so, the 75% level of probability is considered
reliable.

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

51. Reason for choosing the mandibular incisors
1. They erupt first and offer the earliestopportunity of
measurement.
2. They are less variable and more reliable
than maxillary incisors.
 

52. Advantage
1. It has minimal error and the range of possible error
is precisely known.
2. It can be done with equal reliability either by a
beginner or by an expert.
3. It is not time-consuming.
4. It requires no special equipment.
5. It can be done in the mouth as well on the cast.
6. It may be used for both the arches.

53. HUCKABA’S ANALYSIS
He uses both study casts and radiographs for determining the
width of unerupted tooth.
Principle
With any type of radiograph, it is necessary to compensate for
enlargement of the radiographic image. This can be done by
measuring an object that can be seen both in radiograph and
on the cast, such as primary molar tooth.

54. A simple proportional relationship can then be established as
follows:
Actual width of primary molar (Xl)
Apparent width of primary molar (X2)
Actual width of unerupted premolar (YI)
Apparent width of unerupted premolar (Y2)
Xl xY2
YI =
X2

55. Accuracy of this method of determining the width of the
unerupted tooth is fair to good, depending upon the quality of
the radiographs and their position in the arch.
This technique can be used in maxillary and mandibular
arches for all ethnic groups.

56. HIXON AND OLDFATHER’S METHOD
Procedure
The mesio distal width of the mandibular central and lateral
incisor is obtained from the casts.
Determine the width of the premolars from the intra-oral
periapical radiographs made using long cone technique.

57. Sum up the width of the central and lateral incisor along with
the width of unerupted premolars of that particular side.
The estimated sum total width of the cuspids and bicuspids of
that particular side can be obtained from the given chart.
Every measured sum width of incisors and bicuspids has a
corresponding sum width of the cuspids and bicuspids in the
chart.

58. Tanaka and Johnston (1974)
Calculated by measuring teeth on 506 casts of European
patients.
Advantages:
This analysis is considered the easiest and quickest way and
most clinically useful as no additional tables or x-rays are
required (Moyers, 1988; Gardner, 1979).

59. It gives a simplified equation from their study for prediction
that,
Sum of widths of maxillary canine and premolars =
½ sum of width of mandibular incisors + 11.0 mm
 
Sum of widths of mandibular canine and premolars =
½ sum of width of mandibular incisors + 10.5 mm

60. Procedure
Determine the available arch length by measuring distance
from mesial of permanent first molar to the mesial of the
contralateral permanent first molar by dividing the arch into
several segment. Each segment is measured over the
contact points and incisal edges of the teeth. The
segments are added together to provide an approximation
of total arch length.

61. Second step is measurement of the width of the four
mandibular incisors.
Then with the use of the equation we can find the space
available.
The final step in the space analysis is to subtract the width of
the lower incisors and 2 times the calculated premolar and
canine width (both sides) from the total arch length
approximation.

62. If the result is positive there is more space available in the
arch than is needed for the unerupted teeth. If the result is
negative, the unerupted teeth require more space than is
available to erupt in ideal alignment.
 

63. CONCLUSION
•Model analysis is a valuable tool in orthodontic diagnosis and
treatment planning as it helps to study the occlusion & dentition
from all three dimensions & analyze the degree & severity of
malocclusion.
•Thus a proper understanding of the various analyses is
important.