Mixed Dentition Analysis Relationships

Mixed Dentition Analysis
Relationships of Tooth size and
available space during the Mixed
dentition

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Factors noted to Complete the Analysis
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1.The size of all the Permanent teeth anterior
to the first permanent molar.
2.The arch perimeter,
3.Expected changes in the arch perimeter
which may occur with growth and
development.


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The Mixed Dentition Analysis helps one to
estimate the amount of spacing or crowding
which would exist for the patient if all the
primary teeth were replaced by their
successors the very day the analysis is done.
It does not predict the amount of natural
decrease in perimeter which may occur
during the transitional period without the loss
of teeth.

Two Strategic Categories



1.Those in which the size of the unerupted
Cuspids and Premolars are estimated from
measurement of the radiographic image.
2. Those in which the sizes of the Cuspids
and Premolars are derived from knowledge of
the sizes of the permanent teeth already
erupted in the mouth.


Profitt’s Three basic Approaches
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1. Estimation from Proportionality Table
Moyers (1967), Tanaka and Johnson.
2. Radiographic Method
Huckaba G.W Analysis(1964).
3. Combined Radiographic–Prediction Table
Hixon and Oldfather (1956)
Modified by Staley and Kerbers (1980)


Moyers Analysis
Best known prediction table is Moyers(1967)

Moyers follow the second strategic condition



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1.It has minimal systematic error and the range
of such error is known.
2.It can be done with equal reliability by the
beginner and the expert as it does not presume
sophisticated clinical judgement.
3.Not time consuming.

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4.Requires no special equipment or
radiographic projections.
5. Although best done on dental casts, it can
be done with reasonable accuracy in the
mouth,
6.May be used for both dental arches


Mandibular Incisor have been choosen a.Eruped early in the mouth.
 b.Easily measured accurately.
 c. Are directly in the midst of most space
management problems.
Maxillary Incisors are not chosen Variability in size and their co-relation with
other group of teeth are of lower predicted
value.

Procedure in Mandibular Arch


Measure with tooth measuring gauge or a
pointed gauge,the greatest mesiodistal width
of each of the four mandibular incisors.




Record these values on the mixed dentition
analysis form


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Determine the amount of space needed for
alignment of the incisors.
Set the Boleys guage to a value equal to the
sum of the widths of the left central & lateral
incisors .


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Place one point of the midline of the crest b/w
the central incisors & let the other point lie
along the line of the dental arch on the left
side.
Mark on the cast the precise point where the
distal surface of the lateral incisor will be
when it has been aligned.


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Compute the amount of space available after incisor
alignment.
Measure the distance from the point marked in the
line of the arch to the mesial surface of the first
permanent molar.
This distance is the space available for the Cuspids
& two Bicuspids and for any necessary molar
adjustment after the incisors have been aligned.




Predict the size of the combined width of the
mandibular Cuspids and Bicuspids.

Long method



An experienced clinician can use 50%
Prediction since it is more precise estimate.
For inexperienced clinicians, they should use
the 75% Prediction for combined widths of
Canines and two Premolars.

Probability table for predicting the sizes of
unerupted Cuspids and bicuspids

Handbook of Orthodontics 4th edition Robert E Moyers

Contd..
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Short Methodless precise method
Add the width of the mandibular incisors and
divide by two.
To the value obtained add
10.5mm Mandibular Cuspids and Bicuspids
11.0mm Maxillary Cuspids and Bicuspids


Whether using the long or short method,
record the estimated values for the combined
cuspids and bicuspids widths in the mixed
dentition analysis form for both sides and
each arch.
Compute the amount of space left in the
arch for molar adjustment by subtracting the
estimated Cuspid and Bicuspids size from
the measured space available in the arch
after alignment of the incisors.
Record these values for each side.




Procedure For maxillary Arch
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Procedure is similar to lower arch except1. A different probability chart is used for
predicting the upper cuspid and two
Bicuspids sum[ widths]
2. Allowance must be made for Overjet
correction when measuring the space to be
occupied by the aligned incisors.


Probability Table for prediction

Handbook of Orthodontics 4th edition Robert E Moyers



Although various methods of estimation have
been proposed, Moyers regression scheme
[utilizing the buccal segments and the
mandibular incisors] is widely used because
of its simplicity and ease of application.
Prediction of the size of unerupted canines & Premolars
in a contemporary orthodontic population.
Marvin M Tanaka, Lysle E Johnston

JADA vol 88 April 1974

Tanaka And Johnston Prediction
One half of the
+ 10.5mm
mesiodistal
width
of the four
lower incisors + 11.0mm


Estimated width of
mandibular Canine &
Premolars in one
quadrant
Estimated width of
maxillary Canine &
Premolars in one
quadrant

Tanaka And Johnston Prediction




This method has good accuracy despite a
small bias toward overestimating the
unerupted tooth sizes.
Requires neither radiographs nor reference
tables, which makes it very convenient.


Huckaba Analysis

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Recommended by Huckaba.G.W in 1964.
Compensates for radiographic enlargement
of tooth image in periapical film.
It is based on the assumption that degree of
magnification for a primary tooth will be the
same as that of its underlying permanent
successor on the same film.


Method
Measure 1. Width of the primary teeth
on the x-ray film: y
 2. Width of its underlying
permanent successor x on
the x ray film
 3. Primary tooth on the cast
:y
 4. Width of unerupted
permanent tooth is
calculated by
x=xy
y





The value obtained for the mandibular incisors on
the cast and those for canines and premolars on
the radiographs were added to provide the space
required.
Space available is obtained by extending the
brass wire from the mesio buccal of 1st
permanent molar on one side, passing through
the incisal edge of anterior teeth, and to the
buccal cusps of 1st molar on the opposite side.




The difference in the value obtained for
space required and space available is the
amount of discrepancy.


Hixon & Oldfather Analysis




This procedures combines measuremnts
from the dental casts and width
measurements from the peri apical
radiographs.
This method (1956); modified by Staley &
Kerbers(1980) is restricted to the analysis of
the supporting zone in the mandible.


Procedure




Measure the size of unerupted 1st & 2nd
premolar in one mandibular quadrant from a
peri apical radiograph.
Determination of mesio distal tooth width of
the lower central and lateral incisors on the
study cast to the side of the radiograph.




After adding together both figures, the probable
width of the permanent canine and 1st & 2nd
premolars for the corresponding quadrant can be
read off in the prediction graph under the column of
the calculated sum total.




X-axis : Mandibular incisor width measured
on the dental cast + total width of 1st & 2nd
premolar on the peri apical radiograph.



Y-axis : Predicted total width of permanent
mandibular canine and 1st & 2nd premolar.



The formula for calculationΣ3+4+5=[(Σ 1+2+x4+x5) X 0.7158]+2.1267


Stereophotogrammetric:
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A Stereophotogrammetric camera was
developed for non topographic
photogrammetry.
To derive 3 D information from serial cast in
either a graphic or mathematical manner and
to permit the use of computer for analytic
procedure.
Suitable computer programs were designed
for the comparative analysis of geometric
data such as Vault space, Tissue mass,
Surface area, Internal vault slope & Linear
dimensions.

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The basic principle of Stereophotogrammetry
is that of binocular vision.
When 2 photographs of the same object are
taken from slightly separated points, they can
be viewed in a manner that will give a 3D
model surface.
It permits a mathematic and geographic
analysis of solid object such as casts.
It can also supply more analytical information
than graphic tracing methods.


Stereophotographic system
showing two model stages and
windows for the placement of
casts on the stage plane .
The stage plane moves laterally
5 inches.
The film magazine accepts a 9 x
9 inch glass plate.
A precise grid is placed on the
face of the stage plane.

The optic of a schnieder Super
Angulon lens with a principle
distance of 152.73mm and an
equivalent focal length of 95mm.




Three problems particularly suitable for this
analysis are:
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Cast of patient with unoperated complete
unilateral cleft lip and palate.
Serial cast of patient with Apert‟s syndrome.
Comparison of casts treated by rapid expansion
and those treated by conventional full banded
orthodontic appliance therapy.


Occulsograms:
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Developed by Burstone in 1969.
Occlusograms are actual sized photographs
of occlusal surface of dental casts.
Tracings of these occlusograms allows the
orthodontist to simulate treatment in occlusal
view.


Techniques:


Photographic method:
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Occlusal surface of U & L dental casts are
photographed in a 1:1 ratio and a tracing of the
photograph is made.

Photocopying method:


The casts are photocopied on a photocopier
machine and the occlusal photocopy is used to
obtain a tracing.


Occlusogram procedure:
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An occlusogram is a 1:1 reproduction of
occlusal surface of plaster models on a sheet
of acetate tracing paper.
4x5 inch positive film transparencies are
ideal.
These allows occlusograms to be held one
over the other to examine cuspal relationship.
The photographs can be taken either with 35
mm camera and enlarged to 1:1
magnification or with a 4x5 inches Polaroid
camera for 1:1 instant photographic prints.

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Photographic prints are ideal for tracing
purposes.
Problem with producing 4x5 inch
transparencies or photographic print is
maintaining the accurate orientation of the
dental cast which must be accurately trimmed
in the centric relation position.


Once

the dental cast is trimmed in centric
relation, registration grooves are made.
Both

the casts are seated in registration
track in centric relation.




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Cast is placed on the registration track on the
Occlusostat as soon as it is ready for
photograph.
Occlusal surface of teeth are flushed with the
leading edge of the occlostat which is also
the focal length of the camera.




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For photographing both the upper and lower
dental cast, the recommended lens has a
focal length of 210mm. and can be stopped
down to f :45 for the best depth of the field.
The distance from the leading edge to the
camera lens and from the camera lens to the
film is 42cms. At these settings no
enlargement is found at the level of occulsal
plane.
Exposure time varies from 5-30 secs.
depending on the lighting ( incandescent and
fluorescent ) and the film can then be
processed with X-ray developer and fixer.

Occlusogram tracing:
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A sheet of tracing paper is placed over the
photocopy of the cast, rough side up and is
secured at the corners using masking tape.
Tracings are made of both U & L
occlusograms.
R & L should be marked to avoid confusion.
Tracings can be separated by cutting
between the registration lines.

With the U & L occlusogram tracing
registered and secured on the sides, the mid
sagittal registration line can be copied on the
lower tracing.
Growing denture bases can be adjusted so
that they‟ll be in their predicted relationship
at the end of treatment periods.


Uses of occlusograms:
Micheal R. Marcotte –demonstrated the
uses of occlusograms in planning orthodontic
treatment.
Determine arch form and width.
Solution to arch length discrepancies.
Presence and extent of skeletal asymmetries.
Anchorage requirements in each quadrant for
extraction cases.
Presence and extent of tooth mass
discrepancies.

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To estimate final occlusal relationship.
Estimate tooth movements in all 3 planes.
Determine changes in the cant of occlusal
plane.
Aid in arch wire construction.
Growth prediction with the help of tracing.
Quantifying the treatment progress and
discovering the exact nature of many
orthodontic problem.

Disadvantages:
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Time consuming.
Not very precise.
Because of difference in magnification, the
combination of occlusogram with a head
film has been considered difficult and
unreliable.


3 D Occlusogram Software:
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When performing analysis on a scanned
image, the differences in magnification can
easily be accounted for by the computer,
increasing speed, easiness and accuracy.
It was therefore, determined to develop a
user- friendly software that , in addition to
the advantages mentioned by Marcotte, can
also provide the basis for the computerized
appliance design.

The procedure includes :
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Image scanning & setting.
Occlusal view processing
Lateral cephalometric
processing
Occlusogram construction


Advantages
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Combination of lateral cephalometric image with
the occlusal views of the upper & lower dental
casts complete the 3 dimensional set up of the
patient.
Demonstrates all the treatment possibilities. All
the needed movements of the teeth are clearly
visible on the occlusal views in the 3 planes of
space allowing the design for the “custom made
appliance” & the lateral cephalogram shows the
planned displacement for the molars & the
incisors.
The software can simulate the results of standard
surgical procedures.
Ease in using
Accurate & precise
Rapid

Holograms
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The first Hologram was produced by Leith and
upatnieks in 1964.
Holography is a photographic technique for
recording and reconstructing images in such a way
that the 3D aspect of an object can be obtained. The
recorded images is called a “Hologram”.
Holography uses laser light to reproduce very high
quality 3D images of a cast.
It permits 3D model analysis, super impositions and
storage.

Holograms in Orthodontist:
AJODO oct 1995
SYSTEM:
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1. Holocamera
2. Automatic Developer
3. illumination and measuring system


Holocamera
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Easy to handle.
The model being
photographed is
placed on glass plate
for exposure.
The laser beam used
in the camera is
divergent.


Automatic Developer
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Developed to expose
plates without assistance.
Consists of series of trays
that contain the various
chemicals used, a
mechanical engine that
controls the movements of
the holder in which plates
can be placed.
30 plates can be
developed simultaneously.
The holder carries the
plate from tray to tray
each having a different
function during exposure.

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Developing, Water rinsing ,Bleaching and
Wetting procedure are required to develop an
exposed holographic plate.
During each steps ,the holder is kept inside the
corresponding tray as long as time indicates.
The finished hologram will be either red or green
depending on the bleach used.


Measurement System
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Illumination element:
Halogen lamp: to
illuminate the hologram.
Analysis or
measuring element:
Plate holder mounted
on an x-y-z positioner.
The z micropositioner
has an optical fiber
which is connected to a
laser diode that projects
a small red spot light
used for depth
measurement.

Orthodontic Applications
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Measurement of incisor intrusion.
Study the effects of high pull headgear.
Tooth position measurements.
Study the effect of max. expansion on facial
skeleton.
Study the effect of class2 elastics on bone
displacement.
Study the effect of cervical headgear on
maxilla.
Facial & dental arch symmetry.
Determine the centre of rotation produced by
orthodontic forces.
Lower incisor space analysis.

Advantage
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Convenient, low bulk
Resistant to almost all destructive agents apart
from fire. These films may be scratched or bent
or covered in dust without interfering with the
latent image.
Superimposition of images is possible, thus
detection of any changes & tooth movement are
possible.
Holographic image can be measured in 3
dimensions.
Ease in storage, transportation
Cost similar to conventional photography.

Disadvantage
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


Inability to place the holograms immediately
next to the patient‟s mouth to make side by
side comparisons.
Cannot be adjusted once made.
Incorrect occlusion of the models when the
holograms are being made.


Photocopies of the study models
Can be used for :
 1) Comparing pre and post treatment arch forms
 2) Checking original tooth rotations or the initial
arch form during treatment
 3) Communicating with other practitioner about
characteristic of the malocclusion .
 4) Producing occlusograms for demonstration
purpose


These photocopies may be less
precise for :
 1) Measuring arch length

2) Producing occlusograms for
space analysis.


COMPUTERIZED ANALYIS DENTAL CASTS

OSCOPO






Oscopo is a computer program for the
Oscilloscopic Simulation for Correcting
Orthodontically , Problems in Occlusion.
It was developed by Robert H. Biggerstaff in
1970.
It is based on a two dimensional
representation of the upper and lower
dentition as photographed from an occlusal
view.

OSCOPO is the computer method for
measuring, analyzing and evaluating the
dimensional vectors involved in
orthodontic correction.
 It is a visual method for realigning the
dental elements involved in the translation
from a malocclusion to a normal occlusion
in the individual case.





OSCOPO gives a top view of the tooth images
of the mandibular and maxillary dental casts as
projected to the occlusal plane while recording
the patients usual occluding relationship.
Other portions of the program permit
translational, rotational simulations of the image
of a tooth or a group of tooth changing the
occlusal pattern as originally seen on the dental
casts or oscilloscope.






OSCOPO does not have the potential for
discriminating between Apical or Tilting
movement.
It does however represent graphically the
end result of movements produced in the
two defined planes of space.


Digital Study Models
Computerized software are now capable of
scanning study models and storing the
scanned data as 3D images.
3D digital study models are designed to
over come the problems –
 Storage and Retrieval
 Diagnostic Versatility
 Transferability
 Durability



Application Of 3D Imaging Of Teeth




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

Archiving Study Cast
Documentation of treatment progress and
communication between professional
colleagues is made easy.
Can examine intra & inter arch and
transverse relationships between U&L arches
Treatment objectives and planning can be
created by using “Virtual set-up” of
orthodontic appliance.





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Simulation of space following extraction,
tooth uprighting or incisor retraction can be
easily shown.
3D prefabrication of archwires using specific
robotics after setting up brackets position on
the dental arches.
Construction of 3D “ Aligners”- The Invisalign
technology.


e-MODELS-3D Digital dental models
using laser technology- J.C.O (2)-2003
Three dimensional digital study model.
Methods of producing digital models:
 Destructive imaging: Removes the part of
the cast ,a little at a time ,while it is being
imaged.
 Non destructive imaging: Uses structural
light ,laser light or x-rays to image while
leaving the original cast intact.



e - models:


Constructed through a laser
scanning process that
digitally maps the geometry
of a patient‟s dental
anatomy to a high resolution
3D digital image with an
accuracy of +. 01mm.A laser
stripe is projected onto the
surface of the plaster cast &
a digital camera is used to
analyze distortions in the
stripe. The plaster cast is
oriented on all axes to
expose all its surfaces for
scanning.






This process produces 3D vertices that
are connected into thousands of
triangles to form the 3D image.
The software then displays the e-model
on the computer screen by assigning
color shades to each triangle based on
its relative orientation to a digital light
source. This results in a high-resolution
3D image that can be viewed measured
& manipulated on the computer screen
as if the cast is in your hand.

ADVANTAGES OF e-model
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Measurements can be made in any plane or orientation.
Various analysis such as Bolton‟s analysis, arch width &
length analysis can be done.
Cross-sectional tools allow e-models to be sliced in any
vertical or horizontal plane to check symmetry, overjet,
overbite & complete measurements at any location.
Permits analysis of occlusal relationships.
Improves accuracy & efficiency of orthodontic diagnosis,
treatment planning & bracket placement.
Midline analysis (skeletal or dental asymmetries can be
evaluated).
Mock surgeries & presurgical evaluation can be done.
Record keeping
Ease in storage

e-plan






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

Latest innovation in 3D
treatment planning.
Simulates multiple treatment
options to help determine the
most effective treatment plan.
Enables the clinician to simulate
tooth rotations ,movements &
extractions with a click of the
mouse.
They allow pts. to watch the
movement of their own teeth
from a malocclusion view to a
post treatment view.
Effective communication tool for
pts., their families & referring
dentists.


Ortho CAD TM Technology






OrthoCADTM software has been developed by
CADENT, Inc. (Computer Aided DENTistry,
Fairview, NJ) to enable the orthodontist to view,
manipulate, measure and analyze 3D digital study
models easily and quickly.
Alginate impressions of the maxillary and
mandibular dentitions are then downloaded
manually or automatically from the world wide
website using a utility called OrthoCAD
downloader.
The average file size for each 3D model is 3 Mb.



The operator can
browse and view the
models separately
and together from
any direction and in
any desired
magnification on
screen.










The software comes with
several diagnostics tools
such as:
Measurement analyzes
(e.g. Bolton analysis, arch
width and length analysis )
Midline analysis (The
ability to split the model
sagittally or transversely for
better compressions)
Overbite and Over jet
analysis.


The step in orthoCADTM virtual
set-up
1. Choose your preferred brackets,
bands and wires from the available
straight wire systems listed.
 2. Incisors are positioned, as well as
molars.
 3&4. The orthodontists should slide
maxillary and mandibular teeth into
their proper positions or correct the
position of the brackets themselves
to achieve better inter-and intra-arch
relationships.
 5. The sagittal inter-arch relationship
should be double-checked.
 6. Evaluate the transverse
relationship.
 7. Molar position and jaw closure are
adjusted to make sure that the
correct form of treatment is chosen.

Align Technology




The Invisalign appliance for Orthodontic tooth
movement was developed in 1998.
It is the „invisible‟ way to straighten teeth into
a perfect occlusion using thin, clear, overlay
sequential appliance.


Procedure




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

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(A) Initial treatment planning with patients’
photographs and radiographs are sent to
Invisalign lab.
(b) Impressions are converted into plaster
models.
(c ) In lab, models are first coated with
protective shells, & encased in a mixture of
resin and a hardener.
(d) After chemical setting, the become blocks
of the hardened resin with many plaster
models inside. Each tray is placed in a
destructive scanning machine.
(e) Each 3D models is constructed from about
300 2D scans.
(f) Once the teeth are separated and reassembled back into the arches, the designers
create a final set-up of what the patient’s teeth
will look like when the treatment is completed.
(g) For each stereolithographic constructed
model a clear invisalign aligner is created by
heat.
(h) These aligners are trimmed, polished,
cleaned and finally sent to the www.indiandentalacademy.com
prescribing
orthodontist.

Conclusion






There are numerous model analysis based on
different criterias.
Now it is left to the orthodontist to accept which
ever analysis he feels best suits his group of
population and his diagnosis and treatment
planning.
The basis remains the same only the ways to
express it differs. So it does not matter which
analysis you follow but what matter is that how
efficiently you imply the results of it to your treatment
planning and do justice to your patient.

References
 ORTHODONTICS
PRINCIPLES AND PRACTICE,
- GRABER T.M.






Handbook of orthodontics.
- ROBERT E. MOYERS.
Contemporary orthodontics.
- WILLIAM R. PROFFIT.
Orthodontics
current principles and concepts.
- THOMAS M. GRABER & Vanarsdall

Thank You

Mixed Dentition Analysis Relationships

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