4th Book- Mixed Dentistion Space Analysis.pdf

2. i
MIXED DENTITION
SPACE ANALYSIS
Shilpa Hiremath
Rahul VC Tiwari
Nupur Rishabh Shah
Dentomed Publication House,
Amritsar, Punjab

3. ii
Published
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Amritsar-143001, Punjab,
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Phone: 09501544877
Authors: Shilpa Hiremath
Rahul VC Tiwari
Nupur Rishabh Shah
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Mixed Dentition Space Analysis - First Edition 2021
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PREFACE
During mixed dentition period discrepancy between spaces available and required in the arch is
predicted so that teeth can erupt freely with good alignment. Mixed dentition space analysis is done for this
purpose in which size of unerupted canine and premolars is predicted. Accurate prediction is very important
regarding correct orthodontic diagnosis and treatment planning.
Overall, space analysis allows for the estimation of a child's treatment need in relation to crowding and
provides a quantitative guideline for the decision to space maintain or extract, depending on the clinical scenario.
Present book is an attempt to provide clinically relevant information to facilitate the prediction of the
space requirement for unerupted permanent teeth, thus aiding in the diagnosis, treatment planning and
management of crowding in the mixed dentition in children.
Shilpa Hiremath
Rahul VC Tiwari
Nupur Rishabh Shah

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DEDICATION
This Book is dedicated to
My family and teachers

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MIXED
DENTITION SPACE
ANALYSIS
- Dr Shilpa Hiremath
- Dr Nupur Rishabh Shah

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ABOUT THE AUTHOR
Dr Shilpa Hiremath is a Pediatric dentist with more than eight years of specialist
experience, a native of Bengaluru India, she completed her Bachelor in Dental
Surgery from M R Ambedkar Dental College in 2008 and Master of Dental Surgery
from AECS Maaruthi dental college in 2012 .She balances her interest in specialist
practice with her passion for research and innovation in dentistry. Dr Shilpa has
served as the unit head of pediatric dentistry in AIMST university Malaysia for four
years and has been actively involved in development of pediatric dentistry as a
subject in various colleges in India and Malaysia, she has many international and
national publications involving a wide range of topics in dentistry. Dr Shilpa had
been instrumental in development and implementation of the ICDAS dental caries
classification system in Malaysia and had also secured awards for innovation of new
products and concepts in dentistry, a life member of the Indian society of
pedodontics and preventive dentistry she is also a reviewer and member of editorial
boards in many national and international journals.

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CONTRIBUTING AUTHOR
Dr Nupur Rishabh Shah is a Pediatric & Preventive Dentist who has 8 years of
experience in clinical practice. Dr Nupur is from Ahmedabad, Gujarat , India and
she has done bachelor & Master of Dental Surgery from K.M Shah Dental College
& Hospital, Sumandeep Vidyapeeth Deemed to be University, Vadodara, Gujarat.
She has undergone training for Conscious sedation and Naso alveolar moulding
( NAM ) in cleft & Craniofacial anomalies patients from Internationally recognised
Institute. Currently she is Associate professor in Department of Pediatric &
Preventive Dentistry, K.M. Shah Dental College & Hospital, Sumandeep
Vidyapeeth Deemed to be University, Vadodara, Gujarat, India. She is a Co- Project
Director of Ahmedabad Cleft Centre Which is supported by ABMSS – Deutsche
Cleft Kinderhife e. v. . She has many National & International Publications.

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DECLARATION
This book contains information obtained from authentic and highly regarded sources.
Whileall reasonable efforts have been made to publish reliable data and information,
neither the author[s] nor the publisher can accept any legal responsibility or liability for
any errors or omissions that may be made. The publishers wish to make clear that any
views or opinions expressed in this book by individual editors, authors or contributors are
personal to them and do not necessarily reflect the views/opinions of the publishers. The
information or guidance contained in this book is intended for use by medical, scientific
or health-care professionals and is provided strictly as a supplement to the medical, dental
or other professional’s own judgement. The authors and publishers have also attempted to
trace the copyright holders of all material reproduced in this publication and apologize to
copyright holders if permission to publish in this form has not been obtained. If any
copyright material has not been acknowledged please write and let us know so we may
rectify in any future reprint.

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CONTENTS
Sr.No. Topic Page No.
1. Introduction 8
2. Mixed dentition period and its importance 11
3. Importance of Model analysis 13
4. Methods of Mixed dentition space analysis 15
5. Predictions based on measurements of already
erupted permanent teeth -on dental casts
 GV Black [1897]
 Seipel [1946]
 Ballard & Wylie [1947]
 Moorres [1959]
21
22
23
24

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 Singh & Nanda [1972]
 Tanaka and Johnston prediction value
[1974]
 Moyers analysis [1976]
 Rani & Goel [1989]
 VV Subbareddy [1996]
 Boston University Analysis [1997]
25
26
28
32
33
34
6. Measurements of unerupted teeth on radiographs
[ combinations of 1&2]
 Nance Analysis [1947]
 Foster & Wylie [1958]
 Hixon and Oldfather Analysis [1958]
 Bull [1959]
 Huckaba Analysis [1964]
 Ingrevall& Lennart [1978]
35
39
40
42
43
44

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 Levern& Merrifield Analysis [1978]
 Bernabé and Flores‑Mir Method
 Tweed’s Analysis
45
46
49
7. References 51

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INTRODUCTION
Pedodontist has a great opportunity to come across patient in their developing stages of
life. Malocclusion is one of the major problems faced during dento-facial development.
Early intervention of this problem can be done by a proper space assessment in mixed
dentition phase. An important aspect of diagnosis and treatment planning in mixed
dentition is a determination of the relationship of tooth size to arch length. Hence mixed
dentition space analysis form an essential part of an early orthodontic evaluation. An
accurate analysis is an important criteria in determining whether to involve serial
extraction, guidance of eruption, space maintenance, space regaining or just periodic
observation of the patient.
Dental occlusion is the way in which maxillary and mandibular teeth come into contact
with each other. It can be static when the jaw is in rest position or centric in which
maxillary and mandibular teeth are in maximum intercuspation position. For all
orthodontic patients achievement ideal dental occlusion is the main therapeutic goal.

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An orthodontic assessment has to be performed before treating an orthodontic patient. In
the mixed dentition (temporally and permanent dentition) patients, spacing or crowding
of the developing dentition is of prime concern. The accumulated sizes of each child’s
teeth may not be in perfect relationship to the amount of space in the child’s dental arches
to accommodate the dentition.When the accumulated sizes of the teeth and the perimeter
of the arch are not closely correlated a spaced or a crowded dentition results.
It is believed in orthodontic circles that a large number of cases of malocclusion start
during the mixed dentition stage. Mixed dentition is a transition period of occlusion that
has both primary and permanent teeth, usually lasts from 6 to 12 years, and is associated
with maximum orthodontic problems due to the inadequacy of space for erupting
permanent teeth. An early assessment of available space may permit early intervention or
minimize the developing malocclusion.
The assessment of spacing or crowding of teeth is frequently associated with
measurements in the mixed dentition stage because accurate and specific prediction of
future dental developmental events can be made at that stage . Mixed dentition analysis
thus forms an essential part of an orthodontic assessment. This is because it helps to
determine the amount of space available (whetherin the mandibular or the maxillary arch)

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for accommodation of the incremental permanent teeth and for the transitional changes
occurring in the mixed dentition stage.
The dental literature is replete with investigations focusing on the comparative accuracy,
reliability and reproducibility of various mixed dentition space analysis techniques. Early
diagnosis and successful treatment of developing malocclusions can have both short and
long term benefits while achieving the goal of occlusal harmony, function and dental
facial aesthetics.
In order to analyze a case comprehensively, predictive methods should be accurate, safe,
simple, rapid and should not require any special equipment. Different methods of
predicting size of permanent canine and premolar have been mentioned in literature.
Space analysis in mixed dentition can be grouped into three categories; (1) Use of
regression equations (2) Radiographs or (3) Combination of both methods. Out of all the
mixed dentition analysis, the regression equation based on already erupted permanent
teeth are used most widely, especially the Moyer’s probability charts and Tanaka-
Johnston equation.

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MIXED DENTITION PERIOD AND
ITS IMPORTANCE
Mixed dentition period is between six to twelve years of age during which both
deciduous and permanent teeth are present. During this period one can make accurate and
specific prediction of future dental development and also can assess whether there will be
spacing or crowding of teeth in the dental arch. In interceptive orthodontics treatment
planning, it is important to predict space required and available for unerupted canine and
premolars in the arch and this determination of tooth size must be done before eruption of
canine and premolars by a method called Mixed Dentition Space Analysis (MDSA).
Mixed Dentition / Eruption Guide
Permanent teeth start to erupt when children are about 6 years of age. Deciduous teeth
will gradually wobble and fall out as child grows and develops. All deciduous teeth will
be replaced by permanent teeth before the child is 12 or 13 years old. This transition
period is called the "Mixed Dentition Stage".

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Below is the typical guide you can use to prepare for permanent teeth in your children:
 Central Incisor: 6 to 8 years
 Lateral Incisor: 6.5 to 9 years
 Canine: 8.5 to 12.5 years
 First Premolar: 8 to 12 years
 Second Premolar: 8.5 to 13 years
 First Molar: 5 to 7 years
 Second Molar: 10 to 14 years
 Third Molar (Wisdom tooth): 17 to 25 years
When children enter the tooth transition period, their deciduous teeth will loosen and will
fall out. The permanent teeth will gradually erupt into the space left by the deciduous
teeth. Altogether 32 permanent teeth come in. During this time an orthodontic specialist
is recommended to monitor the growth and alignment of the new teeth. This will help to
ensure the various problems to be avoided down the road. It's also easier to correct teeth
while they are fresh and new as opposed to when they've had time to deteriorate and wear
down.

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IMPORTANCE OF MODEL
ANALYSIS
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. Model analysis is an essential diagnostic record that helps
to study the occlusion and the dentition from a three dimensional aspect. The study
ranges from the metric analysis of the arch form to the prediction of 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 dimensions.
ADVANTAGES
 They are three dimensional records of the patient’s dentition.
 Occlusion can be visualized from the lingual aspect.

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 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.
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.

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METHODS OF MIXED DENTITION
SPACE ANALYSIS
In mixed dentition space analysis, mesiodistal width of unerupted canine and premolars is
predicted so that discrepancy between space available and space required for these teeth
in the dental arch can be determined. This also helps to determine whether sufficient
space is available for posterior teeth in the arch so that they can erupt freely with good
alignment. This analysis is very important regarding orthodontic diagnosis and treatment
planning. It helps in determining whether treatment plan is going to involve serial
extractions, eruption guidance, regaining of space, space maintenance or simple
observation of patient for the time period is required. Accurate prediction of size of
unerupted posterior teeth is important in order to establish a good orthodontic treatment
plan.
Purpose of mixed dentition analysis is to evaluate the amount of space available in the
arch for succeeding permanent teeth and necessary occlusal adjustments. A quantitative

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assessment of crowding may be obtained by mixed dentition analysis. In mixed dentition
analysis mainly three factors are considered.
1. The sizes of all permanent teeth which determine – “space required’ for the alignment
of the teeth.
2. The arch perimeter which indicates space available for teeth alignment.
3. The expected changes in the arch perimeter which may occur with growth and
development of occlusion.
Tooth size – Arch Length Discrepancy
 Tooth size - Actual MD width measured on the model using Vernier Caliper.
 Arch length -The length of the dental arch from the distal of the last erupted tooth on
one side to the distal of the last erupted tooth on the other side.
Assumptions are made in calculating a space analysis:
 All permanent teeth are developing normally & not congenitally missing
 Correlation between the size of the erupted mandibular incisors & the remaining
succedaneous teeth

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 Prediction tables are valid for a broad population. e.g.; most of the studies is from
northwest European analysis.
 Arch dimensions remains stable throughout growth. But the intercanine width,
intermolar width & arch length do change with age & eruption.
 Incisors are neither protrusive nor retrusive.
To predict whether there is sufficient space in the dental arch for the unerupted
canines and premolars.
1] Predictions based on measurement of already erupted permanent teeth -on dental
casts.
2] Measurements of the unerupted canine & premolars on radiographic images
3] Combination of 1 and 2
1] Predictions based on measurements of already erupted permanent teeth -on
dental casts;
A. GV Black [1897]
B. Seipel [1946]
C. Ballard & Wylie [1947]
D. Moorres [1959]

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E. Regression eqn. by Ono [1960]
F. Singh & Nanda [1972]
G. Tanaka and Johnston prediction value [1974]
H. Moyers analysis [1976]
I. Rani &Goel [1989]
J. VV Subbareddy [1996]
K. Boston University Analysis [1997]
2] Measurements of unerupted teeth on radiographs [ combinations of 1&2]
A. Nance Analysis [1947]
B. Foster & Wylie [1958]
C. Hixon and Oldfather Analysis [1958]
D. Bull [1959]
E. Huckaba Analysis [1964]
F. Ingrevall& Lennart [1978]
G. Levern& Merrifield Analysis [1978]
H. Bernabé and Flores‑Mir Method
I. Tweed’s Analysis

24. 19
Space available can be measured by dividing the dental arch into 4 straight line segments;
each segment is measured individually with a sharp pointed measuring instrument. Space
available can also be measured by using a flexible scale. Individual teeth dimensions can
be measured using a divider or a Boley’s gauge.
Vernier caliper

25. 20
Armamentarium for model analysis Measurement of
mesiodistal dimension of primary molars on study models
using Vernier caliper.

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ARCH-LENGTH ANALYSIS
Predictions based on measurements of already erupted permanent teeth -on dental
casts:
1. G. V. BLACK ANALYSIS.
Black in 1897, determined the average mesio-distal crown widths of all primary and
permanent teeth, though he did not indicate the population from which the data were
derived. The figures for the primary canine and molar teeth, and for the permanent canine
and premolar teeth, have been referred to by subsequent workers. This was followed by
further attempts by different investigators to estimate the mesiodistal widths of unerupted
permanent teeth.
PRIMARY TEETH MANDIBULAR MAXILLARY
CANINES 5.0 7.0
FIRST MOLAR 7.7 7.3
SECOND MOLAR 9.9 8.2
PERMANENT TEETH MANDIBULAR MAXILLARY
CANINES 6.9 7.6
FIRST MOLAR 6.9 7.3
SECOND MOLAR 7.1 8.2

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2. SEIPEL ANALYSIS.
Seipelattempted to predict the mesio-distal width of mandibular permanent canine and
premolar teeth based on the mesio-distal width of the corresponding mandibular central
incisor. The correlation coefficient was found to be low in all three cases.

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3. BALLARD & WYLIE ANALYSIS.
Ballard & Wylie conducted an investigation to evaluate the assumption that there is
harmony in tooth size in any one individual; that is, if the incisors are larger than average,
the canines, premolars and molars are also correspondingly larger than average. They
examined the casts of 441 individuals who had permanent incisors, canines, premolars
and first molars fully erupted. The correlation coefficient between the sum of the mesio-
distal widths of the mandibular incisors and that of the canines and premolars was +0.64.
Though this figure was low they felt the correlation to be sufficiently high to be of
practical use in the development of a predictive formula: x = 9.41 + 0.527y, in which x =
sum of mesio-distal widths of canine and premolars, and y=sum of mesio-distal widths of
the mandibular incisors. They found that the average error using this formula was 0.6 mm,
or 2.670, and concluded that this equation was of some value in the prediction of the
combined width of unerupted mandibular permanent canine and premolar teeth.

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4. MOORREES ANALYSIS.
Moorrees investigated, by measurements on dental casts of 184 North American children
of European ancestry, the relationship between the mesio-distal crown widths of primary
and permanent teeth. The correlation coefficient was low, reflecting great individual
variation within the population. A sex difference was noted, males having larger teeth
than females; therefore the results were analysed for males and females separately. He
found that permanent incisor and canine teeth were larger than their predecessors,
whereas premolar teeth were smaller. He concluded that measurement of unerupted
permanent canines and premolars on radiographs was more accurate than estimation by
measurement of the primary dentition.

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5. SINGH & NANDA ANALYSIS.
Singh & Nanda measured the mesio-distal width of permanent teeth on the dental casts
of 104 Indian children aged 11-18 years who had varying severities of malocclusion.
Since there were no significant differences between the sexes or types of malocclusion,
the results were pooled. Multiple correlations were performed between different teeth,
between each tooth in a quadrant and between teeth in different quadrants. Teeth of the
same morphological class showed the highest correlation coefficients. The sum of the
mesiodistal widths of mandibular incisors showed a strong relationship with the mesio-
distal width of other teeth, indicating their usefulness as predictors of tooth size. A high
correlation was found between teeth in different quadrants, and from this a prediction
scale was developed in which the sum of the mesio-distal widths of the mandibular
incisors enabled the prediction of the width of unerupted canines and premolars.
Singh & Nanda, though not publishing the widths of the teeth they examined, compared
their data with those obtained by Ballard & Wylie and Bolton, and discovered that the
values for the Indian children were very different from those of Caucasian children, from
which they concluded that there were racial discrepancies in tooth size, and therefore that
data collected from one ethnic group were not transferable to another.

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6. TANAKA & JOHNSTON
ANALYSIS.
Tanaka & Johnston measured teeth on 506 casts of patients of probable European
ancestry. The correlation coefficient between the sum of the mesio-distal width of the
mandibular permanent incisors and the permanent canine and premolar teeth was similar
to that found by Ballard & Wylie and by Hixon & Oldfather. In few of the subjects was
the sum of widths of mandibular incisors outside the range 20.5-27.0 mm, and they
developed an equation similar that of Ballard & Wylie [3]: Y = A + B(X), in which Y =
predicted sum of widths of canine and premolars in a quadrant, X=sum of widths of the
four mandibular incisors, and A and B=constants for each arch being 0.41 and 0.51,
respectively, for the maxilla and 9.18 and 0.54 for the mandible. (The values of A and B
for Ballard & Wylie were 9.41 and 0.527, respectively.) From this Tanaka & Johnston
produced simplified equations for each segment: (i) Sum of widths of maxillary canine
and premolar teeth =half sum of width of mandibular incisors + 11.0 mm. (ii) Sum of
widths of mandibular canine and premolar teeth = half sum of width of mandibular
incisors +10.5 mm.

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Advantages:
• Technique involves simple easily repeated procedures & minimal material needed.
• Does not use prediction charts.
Limitation:
• Prediction equations derived by Tanaka and Johnston is based on data derived from
Northern European Ancestry
• Tends to over-predict slightly the width of unerupted teeth.

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7. MOYER’S ANALYSIS.
Moyers produced a table giving the predicted mesio-distal widths of maxillary and
mandibular permanent canines and premolars on the basis of mandibular incisor widths,
using data obtained from an unspecified number of North American white children. The
analysis allowed for the space required for tooth alignment and retroclination of the labial
segment, if necessary. It was claimed that this analysis was accurate at the 50%
probability level when used by experienced clinicians and at the 75% level by beginners.
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.The analysis advocated by Moyers (1969), has a number of advantages. It can
be completed in the mouth as well as on casts, and it may be used for both arches.
Advantages:
1. It has minimal error and the range of possible error is precisely known.
2. It can be done with equal reliability by the beginner and by the expert.
3. It is not time consuming.
4. It requires no special equipment.
5. It can be done in the mouth as well as one the cast.
6. It may be used for both the arches.

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Basis for Moyer’s Mixed Dentition Analysis:
There is a high correlation among groups of teeth. Thus by measuring one group
of teeth, it is possible to make a prediction on the size of other groups of teeth with a fair
degree of accuracy.
Why mandibular incisors are chosen?
1. They erupt first and offer the earliest opportunity of measurement.
2. They are less variable and more reliable than maxillary incisors.
Procedure:
1. The mesiodistal crown width at the contact points of the four permanent lower
incisors are measured individually.
2. Divide the sum of incisors width in half.
3. Note that the incisors are somewhat crowded and thus some of the space needed to
properly align them is occupied by deciduous canines. This is known as incisor
liability or space needed to allow for incisors alignment
4. The space remaining that is between the spot on the deciduous canine and mesial
surface of permanent first molar – is the space available for the unerupted permanent

35. 30
canine and premolars. The space available in each quadrant of arch is usually
recorded to nearest 0.1 mm
5. Having determined the space available by direct measurement on the cast, now
determine the space needed – ie the combined mesio-distal crown width of unerupted
permanent canines and pre-molars. Locate the sum of four mandibular incisors width
in the topline. Beneath can be seen a 75% prediction line for maxillary and
mandibular arches. The number in these lines represent the predicted sum of
permanent canine and pre-molar in each half of the arch. This is space needed in the
arch and is recorded to nearest 0.1mm
6. Compared the measured space available with the space needed, and the needs of total
space in each quadrant can be readily determined. Ordinarily more than adequate
space is recorded as plus value and less than adequate is minus.

36. 31
Moyer’s probability table

37. 32
8. VV SUBBA REDDY ANALYSIS:
A probability chart similar to Moyers was developed by a study done on population
selected from Kerala, Karnataka, Andra Pradesh and Tamilnadu. - Prediction of
mesiodistal width of 3, 4, 5 using sum of mesiodistald width of 42,41,31,32 same as in
Moyers analysis.
Conclusion
 The mesiodistal width of teeth in males > Females, with difference highly
significant for canines and premolars
 Combined width of mandibular incisors, canine, premolar and max canine and
premolar when compared were found to be similar for AP and Karnataka and that
of Tamilnadu and Kerala.

38. 33
9. M.S. RANI ANALYSIS.
• She applied Moyers probability table to South Indian population. 35% level was more
applicable than 75% as observed by Moyers.

39. 34
10. BOSTON UNIVERSITY
PREDICTION (GIANELLY AA, 1997)
The Boston University Prediction method is based on adding the sum of the width of the
mandibular deciduous canines and twice the width of the first deciduous molars. The
Boston University approach can be used when the deciduous canines and first molars are
still present. Depending on the stage of dental development, i.e. whether deciduous or
permanent teeth were present, the Tanaka & Johnston approach could be used when the
four mandibular permanent incisors have completely erupted, whereas the Boston
university approach can be used when all the deciduous canines & first molars are still
presented. They concluded that all the analysis showed good prediction.

40. 35
MEASUREMENTS OF UNERUPTED TEETH ON
RADIOGRAPHS [COMBINATIONS OF 1&2]
1. HAY NANCE’S ANALYSIS.
Nance (1940), concluded, as a result of comprehensive studies, that the length of the
dental arch from the mesial surface of the mandibular first permanent molar to the mesial
surface of the corresponding tooth on the opposite side is always shortened during the
transition from the mixed to the permanent dentition. The only time the arch length can
be increased even during orthodontic treatment is when the incisors show an abnormal
lingual inclination or when the first permanent molars have drifted mesially after the
untimely loss of second primary molars.
For a mixed – dentition arch length analysis similar to that advocated by Nance,
the following materials are needed. Sharp dividers, a set of periapical radiographs that
have been taken with a meticulous technique, a millimeter rule, a piece of 0.026-inch
brass ligature wire, a ruled 3 x 5 inch card for recording measurements, and a set of study
models. The width of the erupted four mandibular permanent incisors is first measured.

41. 36
The actual width should be determined rather than the space the incisors occupy in the
arch. The individual measurements are recorded. The width of the unerupted mandibular
canines and both premolars on the radiographs should be measured next. The estimated
measurement is then recorded. If one of the premolars is rotated, the measurement of the
corresponding tooth on the opposite side of the mouth may be used. This will give an
indication of the space needed to accommodate all the permanent teeth anterior to the
first permanent molars. The next step is to determine the amount of space available for
the permanent teeth. This may be accomplished in the following manner. A piece of
0.026 – inch brass ligature wire, contoured to arch from, is placed on the lower cast
extending form the mesial surface of the first permanent molar on one side of the arch to
the mesial surface of the first permanent molar on the opposite side. The wire should pass
over the buccal cusps of the posterior teeth and the incisal edge of the anterior teeth.
From this measurement 3.4 mm must be subtracted, the amount by which the arch length
may be expected to decrease as a result of the mesial drifting of the first permanent
molars unless the leeway space is being held. Thus by comparing the two measurements
the dentist can predict with a fair degree of accuracy the adequacy or inadequacy of the
arch circumference.

42. 37
Advantages:
1. It results in minimal error.
2. It can be performed with reliability.
It can be seen both in radiograph and on the casts, usually a primary molar tooth. The
following formula was used to correct the radiograph errors
X1/X2 = Y1/Y2 or,
Y1 = X1 X Y2/X2
Where, X1 = true width of premolars.
Nance space analysis

43. 38
X2 = apparent width of premolars.
Y1 = true width of unerupted premolar.
Y2 = apparent width of unerupted premolar.
Accuracy is fair to good, depending on the quality of the radiographic and their position
in the arch. This technique can be used in maxillary and mandibular arches for all ethnic
groups.
3. It allows analysis of both arches.

44. 39
2. FOSTER & WYLIE.
Examined 72 children at 18- month intervals over a period of 10 years, 14 children being
available at the end of the study. They found that the reduction in arch length was
variable, but generally less than that reported by Nance. They also estimated the size of
unerupted permanent canines and premolars by two methods: the Ballard & Wylie
method, and by measuring the teeth on radiographs taken by the long-cone technique.
They compared these estimates with the actual sizes of the teeth after they had erupted.
Both methods showed inaccuracies, ranging from overestimates of 3.9 and 4.0 mm and
underestimates of 5.7 and 1.6 mm by the Ballard & Wylie and radiographic methods,
respectively.

45. 40
3. HIXON & OLDFATHER.
Examined the dental casts and periapical radiographs of 41 children in the mixed
dentition, and the casts of the same children taken following the eruption of canines and
premolars. Utilizing a 16 in. target-film distance they found a weak correlation between
the mesiodistal widths of the primary and permanent teeth. The correlation coefficient
between the sum of the widths of mandibular permanent incisors and that of mandibular
permanent canines and premolars, measured on the casts, was similar to that reported by
other authors (0.69). The strongest correlation (0.88) was between, on the one hand, the
sum of the widths of the central and lateral incisors in one quadrant, measured on the
casts, added to the sum of the widths of the two premolars in the same quadrant,
measured on radiographs, and, on the other, the sum of the widths of the canines and
premolars after their eruption. From these results the authors devised a table for
prediction of the mesio-distal widths of unerupted canines and premolars, which is shown
in Table.

46. 41
Sum of mesio-distal widths of central and lateral incisors in
a quadrant (measured on dental casts) plus sum of mesio-
distal widths of first and second premolars in the same
quadrant (measured on radiograph) (mm)
Predicted sum of mesio-
distal widths of unerupted
canine and premolars in
the quadrant (mm)
23
24
25
26
27
28
29
30
18.4
19.0
19.7
20.3
21.0
21.6
22.3
22.9
Hixon Oldfather’s probability table

47. 42
4. BULL.
Measured the mesiodistal width of erupted permanent first molars on periapical
radiographs and compared them with measurements of the same teeth on dental casts.
With the target-film distance set at 8 in., radiographic measurement was 3.3% greater
than the direct measurement; with a target-film distance of 16 in. it was 2.3% greater.
From this was produced a mathematical formula: Y = d x c / [2d- c], in which Y =
estimated mesiodistal width of the tooth, d=mesio-distal width of the tooth on the
radiograph taken at a target-film distance of 8 in., and c = mesio-distal width of the
tooth on the radiograph taken at a target-film distance of 16 in.

48. 43
4. HUCKABA ANALYSIS:
He uses both study casts and radiographs for determining the width of un-erupted 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. Due to the possibility of
radiographic elongation or shortening, the author recognized the need to compensate for
radiographic distortion. He developed the procedure on the basis that the degree of
magnification on a given film is approximately the same for a primary tooth as for its
permanent successor. He also determined that the rnandibularpermanent incisors were the
most reliable indices of the size of the remaining permanent teeth of both arches. 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

49. 44
6. INGERVALL & LENNARTSON.
Utilized a stepwise regression in the selection of mixed dentition variables capable of
predicting the sum of mesiodistal widths of unerupted canines and premolars. Stone casts
were made before and after the eruption of canines and premolars. On first examination
at age 10, intra-oral radiographs were obtained using a modified bisecting angle
technique. For prediction of the sum of widths of maxillary canines and premolar teeth,
they recommended the use of the buccolingual width of the maxillary permanent first
molar, and the sum of widths of the maxillary canines and premolars measured on
radiographs. For the sum of widths of mandibular canines and premolar teeth they
recommended measurement of the unerupted canines and premolars on radiographs.

50. 45
7. BERNABÉ AND FLORES‑MIR
METHOD:
The mesiodistal widths of permanent canine and premolars were predicted by using the
following equation:
Y = 3.763 + (0.37 × X0) + (1.057 × X1) + (0.366 × X2),
Where Y is the mesiodistal widths of the unerupted permanent canine and premolars to
be predicted,
X0 is the sum of the upper and lower permanent central incisors plus the widths of the
upper permanent first molars,
X1 is 0 for mandible and 1 for maxilla, and
X2 is 0 for female and 1 for male.

51. 46
8. TOTAL SPACE ANALYSIS:
The total space analysis (TSA) was developed by Levern Marrifield (1978).
This method was divided into three areas. Anterior middle and posterior and the
resulting values for each area were added together to yield the final deficit.
FMA - Frankfort mandibular plane angle
FMPA – Incisor mandibular plane angle
FMIA – Frankfort mandibular incisor angle
Anterior area: For this area the calculation of the difference between space required and
space available was done as before. [Using tooth dimension and brass ligature wire].
Toothmeasurement: Measurements of mandibular incisor widths on the casts were
added to the values obtained from the radiographic measurements of the canine.
CephalometricCorrection: The actual FMIA (in degrees) is subtracted from proposed
angle and the difference (in degrees) is multiplied by a constant (O.S) to give the
difference in millimeters.
Soft tissue modification: The soft tissue modification was derived by measuring the ‘Z’
angle of Merrifield and adding Cephalometric correction (in degrees) to it. If the
corrected Z angle is greater than 800
the mandibular incisor inclination was modified as

52. 47
necessary (upto an IMPA of approximately 920
). If the corrected angle was less than 750
,
additional up righting of incisor is necessary.
Upper lip thickness was measured from the vermilion border of the lip to the greatest
curvature of the labial surface of central incisor.
Total chin thickness was measured from the soft tissue chin to the N-B line. If the lip
thickness is greater than chin thickness, the difference in mm is determined by
multiplying by 2 and adding it to the space required. If it is less than or equal to chin
thickness, no soft tissue modification was necessary.
Middle area: In this area calculations are made of the difference between space required
and space available.
Tooth measurement: The crown widths of the permanent mandibular first molar are
measured at their greatest mesiodistal diameter on the cast. These values are added to the
measurements of the premolars obtained from the radiographs.
Curve of occlusion: The space required to level the mandibular curve of occlusion was
determined. A flat object was placed on the occlusal surface of the mandibular teeth
contacting the permanent first molars and the incisors. The deepest point between the flat
surface and the occlusal surfaces of the primary molar is measured on both sides.
RT side depth + Lt Side depth
Curve of occlusion formula = + 0.5
2

53. 48
This value is added to tooth measurements. Space available was determined by placing
two brass wires (0.033 inch) from the mesiobuccal line angle of permanent first molar on
one side to the other side.
Posterior area: For this area determinations were made of the space required and space
available. The space required consisted of sum of the mesiodistal widths of the two
second and third molars. [Radiographic enlargement was calculated]. In cases where third
molar is not visible wheeler’s dimensions were used and calculation is as follows.
Space available consisted of the space presently available plus the estimated increase or
prediction. (The estimated increase was 3mm/yrs. 1.5mm each side until 14years age in
girls and 16 yrs in boys). The space needed was obtained by measuring the distance on
the occlusal plane between perpendiculars drawn from the occlusal plane tangent to the
distal surface of permanent first molar to the anterior border of the ramus on the lateral
Cephalometric tracing.

54. 49
9. TWEED’S METHOD.
The Tweed diagnostic facial triangle was concerned as a basis for diagnosis and
treatment planning. It consists of
FMA – Frankfort mandibular plane angle
FMPA – Incisor mandibular plane angle
FMIA – Frankfort mandibular incisor angle
Tweed Estd. 250
as norm for FMA
900
for IMPA
650
for FMIA
The value for space required and space available was assessed according to conventional
method. The Tweed foundation research established the following relationships.
When FMA is between 210
- 290
FMIA should be 680
.
When FMA is 300
or greater – FMIA = 650
When FMA is 200
or less – IMPA should not exceed 920
If the cephalometric tracing did not correspond to the above objectives, an objective line
was traced to form the required FMIA. Then the distension between this and the line that
passed through the actual axial inclination of mandibular incisors was measured on the
occlusal plane. The figure is multiplied by 2 to include right and left sides. The total is

55. 50
the cephalometric correction which is added to the difference got by conventional method
to give the total discrepancy.
Analysis for Symmetry:
A symmetry analysis is a technique of examining the arches for symmetry and of
visualizing our changes and disharmonies. Pencils marks placed on the art (carved and
trimmed) portion to identify the dental midline of the upper and lower incisors. When
these midlines do not relate one another, an arch may be deviating or there may be a
combination of deviation of both arches. Such may occur as functional deviation in
mandibular path of closure or may be merely an alteration in tooth position.

56. 51
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Occlusal Developmrnt. Monograph 5, Craniofacial Growth Series. Ann Arbor,

57. 52
Michigan, Center for Human Growth and Development, University of Michigan,
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