Model analysis in orthodontic

1. Model analysis
Dr.Mohammed Maliha

4. Uses of study models
1. Study occlusion .
2. Measurements .
3. Motivate pt. and explain ttt plane .
4. Treatment progress .

5. 5. Stimulate ttt procedure .
6. Transfer records .

6. •Model analysis allows us to carefully examine
several parameters such as dentition, jaw
relationships and make objective
measurements for detailed evaluation and
treatment planning.

7. Armamentarium
•Well prepared study models
•Vernier calipers
•Divider
•Ruler
•0.033” Soft Brass wire ,
Or dental floss .

8. MEASURMENTS USED IN ANALYSIS
The arch length:
Is measured by using a soft
brass from the mesial aspect of
lower first permanent molar,
then passed along the buccal
cusps of premolars incisal
edges of the anteriors.

9. MEASURMENTS USED IN ANALYSIS
Arch perimeter: is the
geometrical dental arc formed
by teeth at their incisal / cuspal
edges. =tooth material .

10. MEASURMENTS USED IN ANALYSIS
Sum of Incisors (SI).
The sums of measured greatest
width of the incisors is recorded
in millimeters.

11. MEASURMENTS USED IN ANALYSIS
Measured Molar Value (MMV).
The distance between the upper right
first molar and upper left first molar ( the
mesial pits on the occlusal surface).
 Measured Premolar Value
(MPV)
The distance between the upper right
first premolar and upper left first
premolar ( the distal end of the
occlusal groove) .

12. MEASURMENTS USED IN ANALYSIS
Anterior arch length :
Made from the midpoint of the
inter-premolar line to a point in
between the two maxillary
incisors.
mandibular value (Ll) .
maxillary value (LU).

13. CLASSIFICATION
PERMANENT DENTITION MODEL
ANALYSIS
MIXED DENTITION MODEL ANALYSIS
Pont’s analysis Moyer’s Mixed dentition analysis
Linder Harth analysis Tanaka and johnston analysis
Korkhaus analysis Nance mixed dentition analysis
Arch perimeter analysis Huckaba’s mixed dentition analysis
(Radiographic method)
Bolton’s analysis
Ashley Howe’s analysis

14. PONT’S ANALYSIS
Pont in 1909, proposed a method of determining the ideal
dental arch width in premolar and first molar area based on the
sum total of mesio-distal widths of maxillary incisors .

15.  Sum of Incisors (SI).
:
 Measured Molar Value
(MMV).
 Measured Premolar Value
(MPV).
PONT’S ANALYSIS

16. Pont suggested that :
The ratio of the combined upper incisor width to
transverse arch width was ideally:
 0.80 in the premolar area .
0.64 in the molar area.
He also suggested that the maxillary dental arch should
be expanded 1-2 millimeters more during treatment than
that found in normal occlusion to allow for relapse.

17. Depending on this ratio we can
Determine :
I. Whether the dental arch is narrow or is
normal in the premolar and molar region for
a given sum of widths of incisors.
II. The need for lateral arch expansion.
III. How much expansion is possible at the
premolar and molar regions.

18. ANALYSI
S
• DETERMINATION OF SUM OF INCISORS (SI)
• DETERMINATION OF MEASURED
PREMOLAR VALUE (MPV) .
• DETERMINATION OF MEASURED
MOLAR VALUE (MMV) .

19. •CALCULATED PREMOLAR VALUE (CPV): or the expected
arch width in the premolar region is determined by:
CPV = SI X 100
80
•CALCULATED MOLAR VALUE (CMV): or expected arch
width in the molar region is determined by:
CMV = SI X 100
64
ANALYSI
S

20. INFERENCE
•If the measured value is less than the
calculated value, then the arch is narrow for
the given sum of incisors width and expansion
can be done.
•If the measured value is greater than the
calculated value, the arch is wider and there is
no scope for expansion.

21. LINDER HARTH ANALYSIS
• Linder Harth proposed an index very similar to that
of Pont’s analysis.
• He made variation in the formula to determine the
calculated premolar and molar values.
• The calculated premolar value (CPV):
CPV = SI X 100
85
• The calculated molar value (CMV):
CMV = SI X 100
64

22. KORKHAUS ANALYSIS
• This analysis is similar
to Pont’s analysis.
• Differe in that it make use of
Linder Harth’s formula to
determine the ideal width in
the premolar & molar
regions.
• And he use additional
measurement Anterior arch
length .

23. • Anterior arch length:
from the midpoint of the
inter-premolar line to a point
in between the two maxillary
incisors.
• mandibular value (Ll) .
• maxillary value (LU)

24. •According to Korkhaus for a given width of the
upper incisors a specific value of the
perpendicular distance between the mid point
of the inter premolar line to the point between
the two maxillary central incisors should exist.

25.  An increase in this
measurement denotes
proclination of the upper
anterior teeth .
 while a decrease in this
value denotes retroclined
upper anteriors.

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

27. Korkhaus’ Measurements

28. •Many malocclusions occur due to discrepancy
between ,
ARCH PERIMETER ANALYSIS
arch length
tooth material.
&

29. ARCH PERIMETER ANALYSIS
It is done in the upper arch.
The analysis is carried out in the lower arch.
 Hay's Nance analysis:
 Careys analysis:

30. 1. Arch perimeter:
Is the geometrical dental arc formed by teeth
at their incisal / cuspal edges.
ARCH PERIMETER ANALYSIS MEASURMENTS :

31. 2. The arch length:
Is measured using a soft brass touching the mesial
aspect of lower first permanent molar, then passed
along the buccal cusps of premolars incisal edges
of the anteriors.
ARCH PERIMETER ANALYSIS MEASURMENTS :

32. Arch length
= space available
Tooth material
=space required
&
ARCH PERIMETER ANALYSIS MEASURMENTS :

33. PROCEDURE
1- DETERMINATION OF SPACE REQUIRED :
Measure the mesiodistal dimension of all the teeth mesial to the
first molar (54321 12345) .│

34. 2- DETERMINATION OF SPACE AVAILABLE:
Measure the arch perimeter using brass wire. From
mesiobuccal line angle of maxillary right first molar , pass
the wire along the buccal cusp and incisal edges in the
anterior region.
PROCEDURE

35. •In case of proclined incisors, pass the brass
wire in the cingulum region, and if the anterior
teeth are retroclined, pass the wire labial to
them like a smooth curve.

36. THE DISCREPANCY :
• space required space available
gives the arch discrepancy or excess.
•If the tooth material > arch length, the space
available for alignment is not sufficient results
in crowding.
•If the tooth material < the space then there
can be spacing.

37. INTERPRETATION OF ARCH PERIMETER
ANALYSIS
ARCH LENGTH DISCREPANCY INFERENCE
0 to 2.5 mm
Proximal stripping can be carried
out to reduce the minimal tooth
material excess
2.5 to 5 mm
Extraction of second premolar is
indicated
Greater than 5mm
Extraction of first premolar is
usually required

38. BOLTON’S ANALYSIS
•Wayne Bolton considered the
ratio of the tooth material of
the maxillary arch to the
mandibular arch .

39. •To get ideal interdigitation, overjet, overbiteand
alignment of teeth ,
Themaxillary tooth material should approximate
desirableratios, ascompared to themandibular
tooth material.
 An alteration in this balance will lead to improper
intercuspation, overjet or spacing.

40. Measurements
• Sum of maxillary 12
• Sum of mandibular 12
• Sum of maxillary 6
• Sum of mandibular 6
• Overall ratio
• Anterior ratio

41. •Anterior ratio =
The sum of the mesiodistal diameter of the 6 mandibular
anterior teeth should be 77.2 % of the mesiodistal widths of
the 6 maxillary anterior teeth.
•Overall ratio =
The sum of the mesiodistal widths of the 12 mandibular
teeth should be 91.3 % the mesiodistal widths of the 12
maxillary teeth, according to Bolton.

42. •If the anterior ratio is greater than 77.2 percent,
then the mandibular anterior tooth material is
excessive.
Determination of Anterior Ratio :

43. Determining Overall Ratio
• If the overall ratio is less than 91.3%, it indicates maxillary
tooth material excess.
• If the overall ratio is greater than 91.3%, then the
mandibular tooth material is excessive.

44. •Bolton said that extraction of one/several tooth
should be done acc. to the ratio of tooth material
b/w upper & lower arch to get ideal overjet &
overbite .
•So Bolton’s analysis helps to determine the
disproportion between the size of the maxillary
and mandibular teeth.

45. Disadvantages of Bolton’s Analysis
• Does not take into account the sexual dimorphism in the
maxillary canine widths.
• Study done on specific population.
• Bolton prefers to do proximal stripping on the upper arch if
the upper anterior tooth material is excess .
• Extraction of a lower incisor, if necessary, to reduce tooth
material in the lower arch.

46. MIXED DENTITION
ANALYSIS

47. AIM
•The purpose of mixed dentition analysis is to
evaluate the amount of space available in the
arch for succeeding permanent teeth and
necessary occlusal adjustments.

48. MOYER’S MIXED DENTITION ANALYSIS
•It is based on the premise that there is a
reasonably good correlation b/w the size of
erupted permanent incisors and the unerupted
canines & premolars.
• This is because a person with large teeth in
one part of the mouth will have large teeth
elsewhere also, as their development is
controlled by the same genetic mechanism.

49. •The lower permanent incisors are measured and
the mesio-distal widths of unerupted permanent
upper and lower canines and premolars is derived
from the probability chart.
•The mandibular incisors are chosen for measuring
as they are the first teeth to erupt in the mixed
dentition period.

50. PROCEDURE
•STEP I: SPACE REQUIRED-
• measure the mesio-distal dimension of all four lower
incisors and sum it up.
• Using the Moyer’s probability chart find the total
mesio-distal width of upper and lower canine and
premolars from the upper and lower charts at 75%
probability for the given lower incisor dimension.

51. •STEPII: SPACE AVAILABLE-
 Determine the amount of space needed for
alignment of the incisors.
PROCEDURE

52. STEPII: SPACE AVAILABLE-
Measure the distance between the distal surface
of permanent lateral incisors and mesial surface
of permanent first molar.


53. Moyer’s Probability Tables

54. CONCLUSION
Mixed dentition analysis forms an integral aspect
of orthodontic diagnosis to determine whether
the treatment plan is going to involve serial
extraction, space maintenance, space gaining or
simply periodic observation of the patient.