model analysis in mixed dentition

1. MIXED DENTITION ANALYSIS
Preceptor:-
Dr.Rakesh Sharma
Presented by:-
Kumar Adarsh

2. CONTENTS
1.Introduction
2.Classification
3.Methods of mixed dentition
analysis
4. Referenes

3. INTRODUCTION
 Model analysis is the study of dental casts, which helps to
study the occlusion & dentition from all three dimensions &
analyze the degree & severity of malocclusion , to derive
the diagnosis & plan for treatment.

4. ADVANTAGES
 They are three dimensional records of the patient’s
dentition.
 Occlusion can be visualized from the lingual aspect.
 They provide a permanent record of the intermaxillary
relationship.
 Helps to motivate the patients,as they can visualized the
treatment progress.
 They are needed for comparison purposes at the end of
treatment & act as a reference for post treatment changes.
 They serve as reminder for the parent & the patient of the
condition present at the start of treatment.
 In case the patient has to be transferred to another
clinician, study model are an important record.

5. DISADVANTAGES
 Vertical skeletal jaw discrepancy can’t be ascertained
from cast.
 Dental cast simply provide an idea of the relative
anteroposterior relationship of the jaws to each other.
 Wheather the maxilla is retrusive or protrusive can’t be
ascertained from casts i.e.anteroposterior status of jaw
to skeletal craniofacial complex can’t be determined
from study cast.
 Degree of labial/lingual inclination of incisors observed
on cast can be misleading because one tends to judge in
relation to the artistic portion of the dental cast base.
Ref:-Jacobson A.,Jacobson R.L;Radiographic
cephaometry from basics to 3-D imaging.2nd ed;2-4

6. Mixed dentition period
Second transitional period (9-10 yrs)
Correction of ugly duckling
Utilization of leeway space (1.8mm
in mx & 3.4mm in Mn arch)
Emergence of permanent
canine,premolar,second molar
Inter transitional period
1to 1.5 yrs Relatively stable
First transitional period
Emergence of first
permanent molar
Exchange of primary
incisor with permanent
incisor (incisor liability)
Establishment of
occlusion
Ugly duckling
stage/Broadbent
phenomenon (8-9 yrs)

7. CLASSIFICATION
Radiographic
 Nance analysis,1940
 Huckaba’s,1964
NONRADIOGRAPHIC SPACE ANALYSIS
 Ballard and Willie,1947
 Moyer’s, 1973
 Tanaka Johnston,1974
COMBINATION OF RADIOGRAPHS & PREDICTION CHARTS
 Hixon and Old father,1956
 Staley kerber-combination,1980

8. AIM OF MIXED DENTITION
ANALYSIS
 To evaluate the amount of space available
in the arch for succeeding permanent
teeth and necessary occlusal adjustment.
Handbook of Orthodontics – Robert E Moyers – 4th edition;235

9. SPACE ANALYSIS
 Space analysis , using the study casts is valuable in
evaluating the likely degree of crowding for a child in the
mixed dentition ; and in that case,it must include the
prediction of the size of the unerupted permanent teeth.

10. Nance’s mixed dentition analysis
(radiographic method),1947
 This analysis is similar to arch perimeter
analysis of the permanent dentition
Armamentarium
 Dental cast
 Boley gauge, millimeter ruler
 Peri-apical radiograph

11. PROCEDURE
 Actual width of four
mandibular incisors
measured on the cast.
 The width of unerupted
canine,premolars is
measured from the
radiograph.
 In case one of the
premolar is rotated,the
width of the premolar on
the opposite side may be
used.

12.  The total value indicates the amount of the
space needed to accommodate all the
permanent teeth anterior to first
permanent molar.
 The space available for the permanent
teeth is determined with a brass wire
passing over the buccal cusp and incisal
edges of teeth from first molar to first
molar.

13.  Substract 3.4mm(in mandibular
arch) and 1.8mm(in maxillary
arch)from the total space available
to accommodate a decrease in the
archlength as a result of the mesial
drift(late mesial shift-leeway’s
space)of the permanent first
molars.
 Space required - space available =
amount of discrepancy

14. ADVANTAGES
 It results in minimal errors
 It can be performed with reliability
 It allows analysis of both arches
LIMITATION
 It is time consuming
 Complete mouth radiograph is needed.

15. Hukaba’s mixed dentition
analysis,(radiographic method)1964
 Principle-If we measure an object,which
can be seen both in the radiograph as
well as on a cast, then we can
compensate for the enlargement of the
radiographic image.
 The amount of distortion can be
calculated and the correct mesiodistal
width of the crown of the unerupted
tooth can be calculated by using the
formula:-

16.  X1/X2=Y1/Y2
X1=width of the unerupted tooth whose width
is to be determined
X2=width of the unerupted tooth on the
radiograph
Y1=width of erupted tooth as measured on the
cast
Y2=width of erupted tooth as measured on a
radiograph.

17. Advantage
 Very easy,practical and relatively accurate
method.
 Not require any prediction table.
 Can be used in maxillary and mandibular
arches.
Disadvantage
 Inherent distortion of radiographic image
causes error.

18. MOYER’S MIXED DENTITION
ANALYSIS(1973)
 Basis- high co relation among groups of
teeth , thus measuring one group of teeth,
prediction of size of other group of teeth
can be done.
 Armamentarium-
1. Dental cast
2. Boley’s guage
3. Probability chart

19. Procedure:
 Measure the greatest mesiodistal widths of each of four
permanent mandibular incisors .
 The mandibular incisors have been chosen for measuring,since
a) they are erupted into the mouth early in the mixed dentition,
b) are easily measured accurately, and
c) are directly in the midst of most space management
problems.
 The maxillary incisors are not used in any of the predictive
procedures, since
i. they show too much variability in size (especially max. lat
incisor), and
ii. their correlations with other groups of teeth are,of lower
predictive value. Therefore, the lower incisors are measured
to predict the size of upper as well as lower posterior teeth.

20.  Total the M-D widths of mandibular incisors.
 Using prediction chart for space available in mandibular
arch,locate the value closest to the sum of four mandibular
incisors.
 On the study cast, determine and mark the midline of
mandibular arch.
 Total the M-D widths of right mandibular incisors & set the
boley’s gauge to this value.
 Measure from midline to right side. Place one point of the
gauge at the midline between the central incisor and let the
other end lie along the line of the dental arch on the right side.
 Mark on the point where the precise point where the distal tip
of boley’s gauge touched.
 Repeat for the left side.

21.  Measure the distance
between the point
marked on the cast to
the mesial surface of
permanent 1st molar
 Record that value and
calculate the difference
 Repeat the process on
the maxillary arch.
 Compute the amount of
space available.
Measure the distance
from the point marked
on the cast to mesial
surface of the 1st
molar, and calculate
space difference.

24. Advantages
 It has minimal error.
 Can be done with equal reliability by the beginner and by an
expert.
 Not time consuming
 No special equipment required
 Can be done in mouth as well as on cast
 Can be used for both arches
 No radiograph required
Handbook of Orthodontics – Robert E Moyers – 4th edition;235

25. Limitations
1. Moyer’s analysis is probability analysis.
2. It does not account for tipping of mandibular
incisor either lingually or facially.
3. Moyers advised caution in using any analysis, as
none was able to compensate for the biological
variation in individuals during the transition from
primary to permanent dentition
4. Moyers equation does not mention the population
group from which they were calculated
5. Moyer’s method of prediction may have population
variations. For one to be sure of the accuracy while
using Moyer’s method it may be safer to develop
prediction tables for specific populations. Thus
Moyer’s method cannot universally be applied.

26. TANAKA JOHNSTON ANALYSIS,1974
Armamentarium
 Boley guage
 Study cast
 The prediction of the size of the unerupted
canines and the premolars in contemporary
orthodontic population can also be done with the
Tanaka Johnston analysis.
 Tanaka and Johnston conducted a study on 506
orthodontic patients in Cleveland.
Ref:-Tanaka MM, lohnston LE: The prediction of the size of the
unerupted canines and premolars in a contemporary orthodontic
population. J Am Dent Assoc 1974; 88:798.

27.  They believed that the Moyer’s
equations and the size of his
confidence intervals have never
been validated on any other
samples.
 Also that the possibility of secular
changes during the past 20 years
cannot be ruled out.
 Hence they undertook the study in
the Orthodontic Department of Case
Western University school of
dentistry

28. Tanaka & Johnston prediction
values
 One half of the mesiodistal width of the four lower
incisor
+10.5mm=estimated width of
mandibular canine and
premolar in one quadrant.
+11.0 mm=estimated width of
maxillary canine and
premolar in one quadrant.
Contemporary Orthodontics – William Proffit – 5th edition;428-29

29.  Advantages-
• Technique involves simple, easily repeated
procedure with minimum material
requirement
• Prediction chart and radiograph is not
required
Limitations
• Error in predicted size if patients are not
from North western European descent.•
*John Y. K. Linga; Ricky W. K. Wong
concluded constants for males (upper-11.5;
lower-10.5) or females (upper-11.0; lower-
10.0) for southern Chinese population

30. HIXON-OLDFATHER PREDICTION
METHOD FOR THE MANDIBULAR ARCH
(1956)
 Iowa Facial Growth Study.
 41 children 15 male,26 female)
 The original equation was primarily obtained from the
measurements of the teeth on the left side of the arch of
each subject whereas the revised equation was derived from
the means of measurements taken from both right and left
side teeth in each subject.
 Armamentarium-
• Boley guage
• Study cast
• Periapical radiograph
• Hixon- old father prediction chart
Ref:-Hixon EH,OldFather RE ,Estimation of the sizes of the
unerupted cuspid and the bicuspid teeth : Angle Orthod :
1958:28:236-240

31. Procedure
 From the casts, on one side, measure the m-d
widths of the permanent mandibular central and
lateral incisor.
 From the periapical radiographs, measure the
m-d width of unerupted first and second
premolars
 Total the m-d widths of four(4) teeth. Compare
the measured value to estimated tooth size
from the Hixon- Oldfather chart.
 Repeat steps 1 to 3 for the other side of the
arch.
 Advantage- it is very accurate technique
 Limitation- Can be used only for lower arch.
Measured value Estimated tooth
size
23mm 18.4mm
24mm 19.0mm
25mm 19.7mm
26mm 20.3mm
27mm 21.0mm
28mm 21.6mm
29mm 22.3mm
30mm 22.9mm

32. Staley and Kerber method,1980
 This method uses both IOPA X-rays and measurements on
dental casts.
 A revision of Hixon and Oldfather mixed dentition prediction
method (1958) was undertaken by Staley and Kerber on the
same group of subjects used originally by Hixon and Oldfather
to develop their prediction.
 These subjects were among those who participated in Iowa
Facial Growth Study.
 Based on equations and computerised data
analysis,significantly improved prediction equations were
developed.
 Staley and Kerber in a later study conducted at the Iowa,
significantly reduced the standard error of estimate when they
generated a revised Hixon and Oldfather prediction equation.
 The co-efficient of correlation of the revised equation was
significantly higher than that of the original equation.
Ref.-Staley RN, Kerber PE. A revision of the Hixon and Oldfather
mixed-dentition prediction method. Am J Orthod 1980; 78(3):
296-302.

33.  A graph was made for clinical use in the prediction of
mandibular canine and premolar widths in mixed
dentition patients.
 This prediction graph is accurate to the nearest 0.1mm.
 Their method requires measurement of the incisors on
models/clinically and of mandibular premolars on
radiographs.

34.  Step by step procedure
for analysis
 1. Measure and add up
widths of mandibular
central and lateral incisors
on one side
 2. Measure widths of
unerupted premolars from
IOPA radiograph of the same
side.
 3. Sum of 1+2
 4. Use the prediction graph
to calculate widths of
unerupted canine and
premolars.

35.  If measurements were available for only one side of the
arch, it can be reasonably assumed that the prediction for
one side would be very similar to that of the opposite side
of the arch.
 Measurement of severely rotated premolars on
radiographs is best avoided.
 A long-cone periapical radiographic technique should be
used in conjunction with this method.

36.  The simple computations and the convenient graph make this prediction
method suitable for clinical use.
 The standard error of estimate for the prediction graph is 0.44 mm .
 All the methods used to predict the widths of unerupted premolars and
canines in the mixed-dentition patient are subject to some error.
 Methods and estimates with minimal error are obviously preferable to
those with larger errors.
 Staley and Kerber method was comparatively more accurate than Hixon
and Oldfather.
 The reasons of improvement were:
a) • Use of a computer, which employed 16 significant digits in its
computations. Hixon and Oldfather did not have the use of an electronic
computer.
b) • Oldfather’s measurements were taken on one side of the arch only most
commonly the left side whereas measurements were taken on both sides
of the arch for Staley and Kerber method.
c) • Hixon and Oldfather used a Boley gauge that read to the nearest 0.1
mm, whereas Helios dial calipers read to the nearest 0.05 mm were used
in Staley and Kerber method.
d) • Premolars that were rotated on the radiographs were not measured in
Staley and Kerber method but were measured by Hixon and Oldfather.

37. Ballard & wylie’s
modification,1947
 Ballard and Wylie were so concerned about the
distortions of the X- ray films that they devised a scheme
for estimating the widths of the mandibular canine and
the premolars on the basis of the combined widths of the
four lower incisors.
 Using the plaster models of 441 cases, they measured
and recorded the widths of all the mandibular teeth
including the first molars.
 On the average, the sum of the four permanent lower
incisors were 23.84 +/- 0.08 mm.
 The average sum of the canine,first and the second
premolars turned out to be 21.97 +/- 0.06mm
Ref.-Ballard,Murray L and Wylie, Wendell L : Mixed dentition case
analysis :Estimating the size of the unerupted permanent teeth : Am Jol
Ortho & Oral Surg : 1947 : 33: 754-759

38.  Although not particularly high, the co-efficient of
correlation of +0.64 seemed sufficiently high to justify a
predicton. They modified the equation as Y = 9.41 +
0.527 ( X )
 Testing these calculations on 60 cases , Ballard and
Wylie came to a conclusion that their method had only
2.6% error as compared to the 10.5% error when using
only the X-rays.
 They do indicate that good X rays should be used and
suggest that their method was an adjunct to the Nance’s
method.

39. Irwin r herold j,richardson a
(1995)
 They did a review of Methods that have been proposed
for mixed dentition analysis , Studies comparing the
different methods have shown that the method of Hixon &
Oldfather (1958), as refined by Staley & Kerber (1980), is
the most accurate.
 * 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.
Ref:-Irwin R, Herold J, Richardson A. Mixed dentition analysis: a review
of methods and their accuracy. IJPD 1995;5:137-142

40. Sushma Sonawane,Asha
Bettigiri,Vivek Soni,2008
 Examine and compare the accuracy of the Moyers and
Tanaka & Johnston mixed dentition analyses and to
evaluate its applicability to Indian Marathi population.
 Developed regression analysis-
 Y = a + b (X) where ,
 X= independent variable (mandibular incisors
measurements)
 Y = dependent variable (sum of canine and premolars).
 For mandibular teeth- Y = 10.830 + 0.563 (X)
 For maxillary teeth- Y = 12.143 + 0.481 (X)
Ref:-Sonawane S, Bettigiri A, Soni V. Comparison of two non-radiographic
techniques of mixed dentition analysis and evaluation of their applicability
for marathi population; Scientific Journal 2008;vol 2.

41.  They concluded that
 a) Both Tanaka Johnson and moyers have comparable
standard errors of estimate,thus their accuracy is fairly
comparable.
 b) Moyers chart at 50% confidence level gives more
realistic estimate of width of unerupted canine and
premolars as compared to 75% confidence level for
Marathi population.
 c) Sugessted the use of newly developed regression
equations is suggested.

42.  None of the Mixed Dentition Analyses are as precise as one might
like, and all must be used with judgment and knowledge of
development.
 Hixon and Oldfather: most accurate
 Tanaka and johnston : most practical
 Radiographic Radiographic method: for population other method: for
population other than Caucasians
 Inaccuracy in radiographic tooth size measurements is not the
dentist's fault.
 It occurs because the developing teeth are not always placed
exactly at right angles to the central ray;therefore, the
radiographic image of the tooth, when slightly rotated or tipped, is
significantly larger than the actual size of the tooth.
conclusion

44. 1) Mathewson R, Primosch R. Fundamentals of pediatric
dentistry.3rd ed;30-33
2) Marwah N. Textbook of pediatric dentistry. Jaypee. 299-
307
3) Irwin R, Herold J, Richardson A. Mixed dentition analysis:
a review of methods and their accuracy. IJPD 1995;5:137-
142
4) Orthodontics-the art and science- S.I. Bhalajhi – III edition
5) Textbook of Pedodontics-Shoba tandon I edition
6) Handbook of Orthodontics – Robert E Moyers – 4th
edition
7) Contemporary Orthodontics – William Proffit – 5th edition

45. 8) Ballard,Murray L and Wylie, Wendell L : Mixed dentition
case analysis :Estimating the size of the unerupted
permanent teeth : Am Jol Ortho & Oral Surg : 1947 : 33: 754-
759
10)Text book of orthodontics- Samire E Bishara
11)Hixon EH,OldFather RE ,Estimation of the sizes of the
unerupted cuspid and the bicuspid teeth : Ang Ortho :
1958:28:236-240
12) Buwembo W, Luboga S.Moyer’s method of mixed
dentition analysis: a meta-analysis.African Health
Sciences2004;4: 63-66
13) Sonawane S, Bettigiri A, Soni V. Comparison of two non-
radiographic techniques of mixed dentition analysis and
evaluation of their applicability for marathi population;
Scientific Journal 2008;vol 2.
14) Textbook of Orthodontics-Gurkeerat Singh – 2nd edition