4. 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
Model analysis is an essential diagnostic record that
helps to study the occlusion and the dentition from
a three dimensional aspect.
5. The study ranges from the metric analysis of the arch
form to the prediction of the sizes of the unerupted
permanent teeth during the mixed dentition.
They have been the “gold standard” in orthodontic
diagnosis with the advantages ranging from being a
routine dental technique, ease of production,
inexpensiveness and ease in measurement to plaster
casts being able to be mounted on an articulator for
study in three – dimensions14.
6. Model analysis can be classified in the following ways
1.Based on whether the analysis is on the permanent
dentition or on the mixed dentition
a) PERMANENT DENTITION ANALYSES
Carey’s / Arch perimeter
Hixon and Old father
Ballard and Willie
8. 2.Based on the arch in which the analysis is carried out
,they can be classified as
Hixon and Old father
Peck and peck
Total space analysis
9. 3.Based on the Parameter determined by the analysis2
TOOTH SIZE ANALYSES
Bolton’s tooth ration analysis
Sanin Savara analysis
RELATIONSHIP OF TOOTH SIZES TO THE
10. SPACE ANALYSES DURING MIXED DENTITION
Ballard and willie
Hixon and Old father
11. 4)Based on principles of space analysis
NON –RADIOGRAPHIC SPACE ANALYSES
Ballard and Wylie
COMBINATION OF RADIOGRAPHS AND PREDICTION CHARTS
Hixon and Old father
12. After completion of the dental cast review, depending upon the age
of the pt, a mixed dentition analysis can be completed.
An early assesment of available space may permit early
intervention /minimise development of malocclusion.
Prediction of the M-D widths of the unerupted canines and the
premolars is an essential part of the tooth size-arch length analysis
during the mixed dentition period.
13. Following the eruption of the permanent incisors, the mandibular
arch length and the width have achieved the adult dimensions for
all practical purposes.
A meaningful mixed dentition tooth size-arch length analysis
depends on an accurate prediction of the mesio-distal widths of the
unerupted permanent canines and the premolars1
14. 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
15. Mixed dentition period
a. Premature loss of primary canine.
b. Rotation or blocking of lateral incisor because of lack of
c. Ectopic eruption of permanent first molars.
d. Distal terminal plane relationships.
16. a) 1st permanent molar and permanent incisors are erupted.
b) The succedaneous permanent teeth are forming.
c) Size relationship between unerupted permanent teeth and
d) There is size difference in primary canines and molars and
the succedaenous teeth.
e) M-D width of primary canines and molars is greater than perm’
sucessors (leeway space of nance) 2
18. Basis- high co relation among groups of teeth , thus
measuring one group of teeth, prediction of size of other
group of teeth can be done1.
1. Dental cast
2. Boley’s guage
3. Probability chart
1. Measure the widths of each of four permanent
mandibular incisors .
2. Total the M-D widths of mandibular incisors
3. Using prediction chart for space available in mandibular
arch,locate the value closest to the sum of four
20. 3)On the study cast, determine and mark the midline of
4)Total the M-D widths of right mand’ incisors & set the boley’s
gauge to this value.
Measure from midline to right side. Place one point of the gauge at
the midline bet’n 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. 5) Measure the dist betw the point marked on the
cast to the mesial surface of perm’ 1st
molar.Record that value and calculate the
6) Repeat the process on the maxillary arch.
23. 6)Compute the amt of space available.
Measure the dist’ from the point marked on the
cast to mesial surface of the 1st molar, and
calculate space difference.
24. It is advocated for foll’ reasons:
Has minimal systemic errors and the range of such errors is known.
Can be done with equal reliability by the beginner and the expert as it
does not presume sophisticated clinical judgement.
Not time consuming, simple and easy to perform.
Requires no special equipment or radiographic projections.
It can be done with reasonable accuracy in the mouth although it is
best done on the dental casts.
It may be used for both the arches.
It has minimal error.
Can be done with equal reliability
Not time consuming
No special equipment required
Can be done in mouth as well as on cast
Can be used for both arches
1. Moyer’s analysis is probability analysis
2. It does not account for tipping of mandibular incisor either lingually or
3. Maxillary tooth size is predicted by mandibular teeth
27. 4. 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 dentition3.
5. Moyers equation does not mention the population group from
which they were calculated 13
6. 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 applied12.
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.
29. 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
30. They simplified the Moyer’s results and gave regressive equations of
Y = A+B(X)
Where Y = sum of the mesio distal widths of the unerupted canines
X = sum of the mesio distal widths of the lower incisors
A & B are constants.
For the maxillary arch , Y = 11 + 0.5 ( X )
For the mandibular arch, Y = 10.5 + 0.5 ( X )
• Technique involves simple, easily repeated procedure with minimum
• Prediction chart and radiograph is not required
• Error in predicted size if patients are not from North western
• *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
32. Iowa Facial Growth Study.
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.
33. 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.
• Boley guage
• Study cast
• Periapical radiograph
• Hixon- old father prediction chart
34. Procedure( Stanley and Kerber, 1980)
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-
Repeat steps 1 to 3 for the other side of the arch.
35. Advantage- it is very accurate technique
Limitation- Can be used only for lower arch.
Measured value Estimated tooth size
37. This analysis is similar to arch perimeter analysis of the
Boley gauge, millimeter ruler
38. SPACE REQUIRED:
◦ measure the mesio distal width of the erupted
◦ Measure the width of each unerupted tooth, cuspids
and bicuspids from the IOPA.
◦ The total mesiodistal width of all the teeth in each
quadrant will indicate space required to accommodate
the permanent teeth.
40. SPACE AVAILABLE:
◦ using brass wire, measure the arch perimeter
from the mesial surface of permanent first molar
to the mesial surface of the permanent first molar
on the other side.
◦ Compare the space required and space available
to arrive at the arch length discrepancy
It results in minimal errors
It can be performed with reliability
It allows analysis of both arches
It is time consuming
Complete mouth radiograph is needed.
42. 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
43. 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.
44. This analysis makes use of a radiograph and study cast to
determine the width of unerupted teeth
Boley gauge, millimeter ruler
45. With any type of radiograph, it is necessary to
compensate for enlargement of radiographic image.
This can be done by measuring an object that can be
seen both in the radiograph and on the cast, such as
primary molar tooth.
It is possible to determine the measurements of un-
erupted teeth by studying the teeth that have already
erupted in a radiograph and on a cast
46. A simple proportional relationship can be established as
47. Hixon and Oldfather: most accurate
Tanaka and johnston : most practical
Radiographic Radiographic method: for
population other method: for population other than
48. 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.
49. 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
Y = dependent variable (sum of canine and
For mandibular teeth-
Y = 10.830 + 0.563 (X)
For maxillary teeth-
Y = 12.143 + 0.481 (X)
50. They concluded that
a) Both Tanaka Johnson and moyers have comparable
standard errors of estimate,thus their accuracy is fairly
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
c) Sugessted the use of newly developed regression
equations is suggested.
52. 1) Mathewson R, Primosch R. Fundamentals of pediatric dentistry.3rd
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 – 4th edition
53. 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
9) Textbook of Orthodontics-Hitchkock , Perry H
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
The best known prediction tables for estimating the required space of unerupted permanent canines , first and second premolars is that of Moyer’s. The mandibular incisors have been chosen for measuring , since they erupt into the oral cavity early in the mixed dentition, they are easily and accurately measured and directly measured amidst of most of the space management problems.
Using probability chart(75% level), locate the closest value to sum of four mand’ incisors.In the presence of the incisor crowding, the distance of the incisor width in the line of the arch for each quadrant from the contact point of the lower central incisor is marked
This method given by Moyer’s is the most commonly used mixed dentition space analysis and it is this method that is advocated for the following reasons
John Y. Linga K, Ricky W.,Wong K. Tanaka–Johnston Mixed Dentition Analysis for Southern Chinese in Hong Kong 2006. Angle Orthodontist;76:632-636
Hixon and Oldfather were the first to develop an equation to predict the mesio-distal widths of the uneruptedmandibular canines and premolars in children who participated in the Iowa Facial Growth Study.