Diagnostic Aids {Study cast, Cast analysis} Part (2) Prepared by Dr. Mohammed Alruby Study cast Definition: it is a positive replica of the teeth and their supporting structure, it should be reproducing accurately all the anatomical details of the teeth, alveolar process, mucobuccal folds, palate, frenal attachment as well as the exact relationship of the mandibular to the maxillary dental arch Good models begin with good impression, orthodontic impression should displace the lips and cheeks, so that, the full depth of mucobuccal sulci is recorded. This over extension of impression is obtained by building up the tray periphery with wax or by using special orthodontic trays The position of maximum intercuspation should be recorded by getting the patient to bite through softened wax, that is important for: 1- Recording the proper intercuspation specially in cases of poor occlusal fit due to extraction or tongue thrust. So it is wise to check the occlusion in the mouth and compare it to the occluded cast to insure that the model is correctly articulated 2- Trimming of the upper and lower cast together without change in occlusal relationship or fracture of teeth Occlusal registration of wax bite: = the position of maximum intercuspation as well as the centric relation must be registered = a piece of soft wax large enough to cover the occlusal surface of maxillary teeth is shaped to the form of maxillary arch, then gently pressed against the maxillary teeth = the patient instructed to relax and mandible is guided to most posterior and superior position of condyle within the glenoid fossa, while the teeth come into occlusion = if there is shifting during closure due to cuspal interference, this mean that the occlusal position is not coincide with centric occlusal position, in this case, in this case two bites are taken one for usual occlusal position, and the other for centric occlusion Ideal requirements of orthodontic study models: 1- They are symmetrical and pleasing to the eye and so that a symmetrical arch form can be readily recognized 2- The dental occlusion shows by setting the models on their backs 3- Clean, smooth, bubble free, with sharp angles where the cuts meet 4- Glossy in finish. Trimming of study models: There are two types of trimming: a- Angle trimming: The purpose of angle trimming is to added an appropriate proportional bases to the anatomical portion of dental casts which is important in: - Registration of centric occlusion by having the posterior and lateral border of both casts on the same plane, so that cast may place on any side without change in its relationship - Giving an idea about the relationship of the teeth to the alveolar process and basal bone - Giving harmonizing appearance of the right and left sides of the cast which any a symmetry can be detected - Detection of occlusion from any side, anterior as well as lateral sides Principles: 1- The floor of the base is trimmed

1. 1
Dr. Mohammed Alruby
Diagnostic Aids
{Study cast, Cast analysis}
Part (2)
Prepared by
Dr. Mohammed Alruby
Study cast

2. 2
Dr. Mohammed Alruby
Definition: it is a positive replica of the teeth and their supporting structure, it should be
reproducing accurately all the anatomical details of the teeth, alveolar process, mucobuccal folds,
palate, frenal attachment as well as the exact relationship of the mandibular to the maxillary dental
arch
Good models begin with good impression, orthodontic impression should displace the lips and
cheeks, so that, the full depth of mucobuccal sulci is recorded. This over extension of impression
is obtained by building up the tray periphery with wax or by using special orthodontic trays
The position of maximum intercuspation should be recorded by getting the patient to bite through
softened wax, that is important for:
1- Recording the proper intercuspation specially in cases of poor occlusal fit due to extraction
or tongue thrust. So it is wise to check the occlusion in the mouth and compare it to the
occluded cast to insure that the model is correctly articulated
2- Trimming of the upper and lower cast together without change in occlusal relationship or
fracture of teeth
Occlusal registration of wax bite:
= the position of maximum intercuspation as well as the centric relation must be registered
= a piece of soft wax large enough to cover the occlusal surface of maxillary teeth is shaped to the
form of maxillary arch, then gently pressed against the maxillary teeth
= the patient instructed to relax and mandible is guided to most posterior and superior position of
condyle within the glenoid fossa, while the teeth come into occlusion
= if there is shifting during closure due to cuspal interference, this mean that the occlusal position
is not coincide with centric occlusal position, in this case, in this case two bites are taken one for
usual occlusal position, and the other for centric occlusion
Ideal requirements of orthodontic study models:
1- They are symmetrical and pleasing to the eye and so that a symmetrical arch form can be
readily recognized
2- The dental occlusion shows by setting the models on their backs
3- Clean, smooth, bubble free, with sharp angles where the cuts meet
4- Glossy in finish.
Trimming of study models:
There are two types of trimming:
a- Angle trimming:
The purpose of angle trimming is to added an appropriate proportional bases to the anatomical
portion of dental casts which is important in:
- Registration of centric occlusion by having the posterior and lateral border of both casts
on the same plane, so that cast may place on any side without change in its relationship
- Giving an idea about the relationship of the teeth to the alveolar process and basal bone
- Giving harmonizing appearance of the right and left sides of the cast which any a symmetry
can be detected
- Detection of occlusion from any side, anterior as well as lateral sides
Principles:

3. 3
Dr. Mohammed Alruby
1- The floor of the base is trimmed first, so that the base is 15mm un height and is parallel to
the occlusal plane, the lower base is trimmed first
2- Trim the lower back perpendicular to the midline
3- With the models in occlusion, trim the upper back until flush with the lower back, the upper
back should be perpendicular to the median palatal raphe
4- Place the occluded models on their backs and trim the upper base until become flat, cheek
upper and lower bases with the casts in occlusion for parallism and backs for flush plane
5- The buccal margin of the lower cast is trimmed until the edge of the vestibule, so that it
parallels to the molar – canine occlusal line
6- The anterior portion of lower cast is trimmed to a smooth curve from canine to canine, while
that of upper cast is trimmed to a point at midline
7- The heel is trimmed so that, it is perpendicular to a line bisecting the cusp of canine on the
opposite side of the heel
8- The models are occluded then the buccal border and the heels of upper cast are trimmed
until flush with that of lower cast
Requirements of finished casts:
1- The height of the model is about 7cm and the height of each base is about 15mm
2- The angle between the heels and back is 130 -135 degree
3- The angle between the lateral borders and base is 65 degree for upper and lower
4- The angle between the lateral side and anterior side of upper at canine area is 30 degree
5- The bases should be parallel to each other and to the occlusal plane which should centered
between upper and lower bases
6- The angle between the base and back is 90 degree
** rubber molds that allows reproduction of the base according to angle trimming is now available
in different sizes
** the cast should be polished and soaped, also talc powder is used for polishing
** the cast is marked by stamping the name, code number, DOB and date of examination of the
case
b- Sassoni trimming:
Objectives:
The dental arches are related to basal bone and facial skeleton, so the diagnosis will be accurate
if the teeth is relating to their supporting structures
Procedure:
1- Lateral and PA cephalometric radiograph are taken
2- Cephalometric tracing:
- The outline of the teeth is traced with special attention to the incisors and molars
- In mandible locate: menton, Gonion, pogonion
- In maxilla locate: ANS, PNS
- In upper face trace: superior and inferior outline of the orbit and locate the orbital and
sella turcica and anterior clinoid process
- Draw the following planes:
a- Mandibular plane
b- Perpendicular to MP through pogonion
c- Palatal plane

4. 4
Dr. Mohammed Alruby
d- Palatal plane parallel: 5mm above PP
e- Perpendicular from ANS to optic plane
f- Optic plane:
Draws the superior orbital plane tangent to the roof of the orbit and superior part of
anterior clinoid process
Draws the inferior orbital plane tangent to the inferior margin of orbit and lower margin
of sella turcica
The optic plane bisect the angle formed by supra-orbital and infra-orbital planes
Optic plane is used instead of the FH because it is more accurate since it is based on
fixed land marks
g- The posterior base line: draws 5mm posterior to PNS perpendicular to the optic plane
and intersect the palatal plane, palatal parallel and mandibular planes
3- Pouring the models:
After impression taking, the alginate impression is filled with stone also 8x8x5cm container is filled
with stone, the impression tray is gently pressed against the stone in the container, all excess
around the anatomic portion is removed before setting. After setting the trays and alginate is
removed carefully avoiding fracture of the teeth and also the cast is removed from the container
4- Gross reduction and orientation of the bases:
a- Trim both sides parallel to the mid-palatal suture at least 5mm buccal to the most lateral
molar
b- Superimpose the tracing paper over the maxillary and mandibular casts in occlusion in such
manner that both incisors and molars also occlusal plane should be coincide with each
other
c- Transfer the exact cephalometric tracing including:
Palatal plane
Palatal plane parallel
Mandibular plane
Posterior base line
Perpendicular to MP through pogonion into the models by drawing these planes on models
d- Then reduce the excess stone taking these planes as a guide then finish and polish
Information obtained from the study models:
1- To examine the occlusion from lingual aspect as well as from labio-buccal aspects
2- To explain the treatment plane to the patient and his parents
3- To detect the direction to which teeth should be moved
4- To determine:
the individual teeth malposition
rotation
axial inclination
midline shifting
occlusal fitness
degree of overjet and over bite
5- Mixed dentition and arch length analysis
6- Construction of diagnostic set up
7- As a pre-treatment record to which results of treatment can be compared and as a post
treatment record to which stability of occlusion can be checked

5. 5
Dr. Mohammed Alruby
8- Model surgery
9- Determination of transverse and anterior posterior a symmetry of the arch
10-Classification of malocclusion
11-Help in evaluate the case during and post treatment
Orientation of study cast models:
3 reference planes lie at right angles to one another:
1- Mid palatal raphe: assessment of transverse discrepancy
2- Tuberosity plane: for analysis of anterior and posterior malposition
3- Occlusal plane: assessment of vertical malposition
N: B:
Mid palatal raphe: is constructed with the help of two points:
1- Anterior point: cross section of the 2nd
palatine rugea with palatine raphe
2- Posterior point: border of hard and soft palate on the raphe
Pont’s index:
Pont in 1909 conceived the idea that broad teeth need broad arch for normal alignment and
that narrow teeth can be aligned in normal narrow arch
= He proposed a method of predetermining the ideal dental arch width known as Pont’s index.
=However, he felt that, the method of measuring teeth to determine arch width not only the factor
that consider in orthodontic treatment and stressed to the other factors that must be considered as:
- Assessment of facial profile
- Determination of Angle classification
- Relationship of jaws to each other
- Midline
= Pont noted that, the mesio-distal width of U1,2 could be used to predict the mesio-distal width
of U 3 in normal dental arch, he suggests that half of mesio-distal width of U 1 plus the mesio-
distal width of U2 equal mesio-distal width of U3
= he suggests that, there is a constant relationship exist between the width of upper anterior
incisors and the width of dental arch at premolar and molar region
= all these prediction and measurements are for upper arch and did not include assessment of
lower arch
= in ideal dental arch he concluded that, the ratio of combined incisors width was 80 in premolar
and 64 in molar region, this ratio has been translated into a table after referred as Pont’s index
as: in which the M D width of incisors are in 1st
column, the ideal width at premolar in second
column, and the width of molar region at third column
= In orthodontic procedure Pont suggested that, maxillary dental arch should be expanding one
or two mm more than that found in normal occlusion to allow for relapse and he included this
factor in his ratio.
Pont’s analysis helps in the following:
1- Determining whether the dental arch is narrow or wide
2- Determining the need for dental arch expansion
3- Determining how much expansion is possible at the premolar molar region
- Obtaining the mesio-distal width of upper incisors right and left SI: measured by a caliper
and recorded in mm (SI)

6. 6
Dr. Mohammed Alruby
- Determine measured premolar value MPV: measure the width of the arch at premolar
region from the distal end of occlusal groove of one side to the distal end of occlusal groove
in other side --- (MPV)
- Determine measured molar value MMV: measure the width of the arch at molar region from
the mesial pit of upper 1st
molar to the mesial pit of 1st
molar in opposite side (MMV)
- Calculated PV: The expected arch width in premolar region is calculated by: SI X 100 / 80
- Calculated MV: the expected arch width at molar region is calculated by: SI X 100 / 64
- If calculated value is more than measured it indicate the need for expansion, so it is possible
to determine how much expansion is needed in molar and premolar region
** the points used for measurements in lower arch are: disto-buccal marginal angle on the
1st
premolar
= Korkhaus proposed index values of 84 and 65 rather than Pont’s index original value of 80 and
64.
Drawbacks of Pont’s index:
1- Maxillary lateral incisors are the teeth most commonly missing from the oral cavity
2- Peg shaped lateral can be seen
3- It is difficult to achieve corresponding mandibular dimension that are necessary to
maintain a balanced occlusal relationship
4- It does not take skeletal mal-relationship into consideration
5- The analysis was done from the casts of French population
Rees analysis of the apical base:
Rees in 1953 assessed the relationship that exist among the maxillary and mandibular tooth
materials, and the maxillary and mandibular apical bases.
The analysis is carried out as follow:
1- Erasing the lip and check frenum on the cast
2- Construction of three perpendiculars to the occlusal plane (mesial to 1st
permanent molar
and at the contact point of central incisors), these lines extended by 8 -10mm from the dental
papilla toward the vestibular fold
3- Measuring the distance from mesial of the 1st
permanent molar on one side to that on the
other side through the tips of the vertical lines with the aid of a piece of thin adhesive tap
4- Determining dental arch width by measuring the arch perimeter mesial to the 1st
permanent
molars using a piece of brass wire
He measured 20 normal cases and found:
- Upper tooth material exceeds lower by: ----------------- 7.37mm
- Upper apical base exceeds lower base by: --------------- 6.34mm
- Upper apical base exceeds upper tooth materials by: ----3.20
- Lower apical base exceeds lower tooth materials by: -----4.47mm
He also concluded that analysis would determine accurately whether a malocclusion is an
extraction, non-extraction or border line cases
== Faten H Eid: make another study on a group of Egyptian individuals with normal occlusion
(34 males and 30 females), the results revealed that,
- Upper apical base exceeds than lower apical base by: ----------------- 8.6mm
- Upper apical base exceeds than upper tooth material by: --------------8.1mm
- Upper tooth material exceeds than lower tooth material by: -----------7.7mm
- Lower apical base exceeds than lower tooth material by: ---------------7.1mm

7. 7
Dr. Mohammed Alruby
Linder Harth index: 1961
Linder Harth proposed an index similar to that of Pont’s index, he made a variation in formula to
determine the calculated premolar and molar values:
Calculated premolar value: CPV: SI x 100 / 85
Calculated molar value: CMV: SI x 100 / 65
Korkhaus analysis: 1939
This analysis is similar to Pont’s index. Only difference that it uses the Linder Harth
formula to determine the ideal arch width at premolar and molar region. In addition, this analysis
also utilized a perpendicular measurement was made from the point in between the two maxillary
incisors to the midpoint of the inter-premolar line
= according to Korkhaus for a given width of upper incisors a specific value of the distance
between the midpoint of inter-premolar line to the point between the two maxillary incisors should
exist
= an increase in this perpendicular measurement denotes proclination in upper anterior teeth,
while decrease in this value denotes retroclined upper anterior
Arch perimeter analysis:
Analysis to determine the difference between space available and space required for tooth
alignment and will done in upper arch
Procedure:
1- Calculation of space required for alignment of teeth by measuring the mesiodistal
dimension of all teeth mesial to first molar in both sides (5 to 5)
2- Calculation of space available by measuring the arch perimeter by using brass wire along
the buccal cusps and incisal edges of anterior teeth in both sides and then measure the
length of the wire that give the space available
In case of proclined anterior teeth, pass the wire on the cingulum region and if the anterior
teeth are retroclined pass the wire on the labial surface on a smooth curve
3- The difference between the space required and space available are the arch discrepancy or
excess
Carey’s arch analysis: 1949
This analysis is carried out in lower arch and it is analogous to the arch perimeter in upper arch
Procedure:
1- Measure the total mesiodistal dimension of all teeth mesial to 1st
molar in both sides (5 to
5) and added, this is a space required for alignment
2- Calculation of space available by using 0.20 brass wire along the buccal cusps of buccal
teeth in one side and incisal edge of anterior teeth and continuing to the other side
In case of proclined anterior teeth, the brass wire passing through the cingulum region and
if the teeth are retroclined, the wire passing on the labial surface on a smooth curve
3- The difference between the space required and space available are the arch discrepancy or
excess
Lundstrom segmental analysis:1960

8. 8
Dr. Mohammed Alruby
Used to perform the indirect assessment of arch perimeter segmentally on both arches, the
dental arch is divided into six straight line segments including two teeth per segment starting from
the distal aspect of 1st
permanent molar from one side to the distal aspect of 1st
on the other side
The space required of each segment is calculated and also the space available is calculated for
each segment
The difference between the space available and space required for each segment determine the
position of the teeth (negative value indicate crowding)
Bolton analysis:
Wayan A Bolton presented his analysis in 1958, as in well aligned upper and lower arches
with normal overjet and over bite relationship there is a definite proportionality of tooth size
between two arches. If the proportionality is met, the maxillary dentition is fit well with mandibular
teeth. the presence of disproportionality sized teeth in either arch can make it difficult to obtain:
- an occlusion with good alignment
- ideal overbite
- ideal overjet
- class I molar relationship
objective:
1- Studied the inter-arch effects of discrepancies in tooth size to device a procedure for
determining the ratio of mandibular versus maxillary tooth size and anterior mandibular
versus maxillary tooth size
2- Study of these ratios helps in estimating the overbite and overjet relationship that will obtain
after treatment is finished
3- Study of the effects of contemplated extraction on posterior occlusion and incisors
relationship and the identification of occlusal misfit produced by inter-relation tooth size
incompatibilities
Procedures:
Over all ratio:
Sum of widths of 12 mandibular teeth / sum of widths of maxillary 12 teeth x 100 = 91.3%
The main ratio result in ideal overbite and overjet relationships
== If the overall ratio is increased than 91.3%, this discrepancy is due to excessive mandibular
tooth material. The amount of this mandibular excess can be determined by:
- Using this formula: sum of mandibular 12 – sum of maxillary 12 x 91.3 / 100
- Using the chart, as one locates the figure corresponding to the patient’s maxillary tooth size
and opposite is the desired mandibular measurement. The difference between actual and
desired mandibular measurement is the amount of excessive mandibular teeth
== If the overall ratio is decreased than 91.3% this discrepancy is due to increased maxillary
tooth material. The amount of this excess can be determined by:
- Using this formula: sum of maxillary 12- sum of mandibular 12 x 100 / 91.3
- Using the chart of Bolton, as the difference of between actual and desired maxillary tooth
material measurement is the amount of excessive maxillary tooth material
Anterior ratio:
Sum of widths of 6 mandibular anterior teeth / sum of widths of 6 maxillary anterior teeth x 100
= 77.2%
The desired ratio is 77.2% which provide ideal overjet and overbite relationships, if the angulation
of incisors is correct and the labio-lingual thickness of the edges are not excessive.
== If the anterior ratio is more than 77.2% indicate excessive mandibular tooth material. The
amount of this excess can be determined by:

9. 9
Dr. Mohammed Alruby
- Using formula: sum of mandibular 6 – sum of maxillary 6 x 77.2 / 100
- Using Bolton chart as the difference between actual and desired mandibular 6 tooth
material is the amount of excessive 6 mandibular teeth
== If the anterior ratio is less than 77.2 indicate excessive in maxillary tooth material. The amount
of this excess can be determined by:
- Using formula: sum of 6 maxillary teeth – sum of sum of 6 mandibular x 100 / 77.2
- Using Bolton chart as the difference between actual and desired maxillary tooth material
measurements is the amount of excessive maxillary tooth material
*** A quick check for anterior tooth size discrepancies can be done by comparing the size of the
upper and lower lateral incisors and quick check for posterior segment discrepancies by
comparing the size of upper and lower second premolars which should be equal size
*** Care must be taken in the use of this analysis since Bolton formula do not take into account
quantitatively the incisors angulation
Disharmony between the widths of upper and lower teeth can be improved by:
1- Alter the normal extraction plane to compensate for size of discrepancies
2- Interdental stripping
3- In extreme cases
4- Changing the angulation of the incisors
5- Accept a small space in one arches. (usually distal to the lateral incisors)
((tooth size discrepancy of less than 1.5mm is rarely significant))
Drawbacks:
- Study was done on a specific population and ratio obtained need not to be applicable to the
other population group
- This analysis not take into account the sexual dimorphism in the maxillary canine width
Ashley Howe analysis: 1947
He reported that the fact that crowding could result not only from excessive tooth size but also
from inadequate apical base, so Howe’s formula for determination whether the apical base could
accommodate the teeth:
TM: tooth material: sum of MD diameter of the teeth anterior to 2nd
molar from one side to the
other side.
PMD: premolar diameter: measured from the tip of 1st
premolar buccal cusp of one side to the tip
of buccal cusp of 1st
premolar on other side.
PMD / T M: ratio of premolar diameter to tooth material
PMBAW: premolar basal arch width measured by the end of Boley gauge of diameter of the apical
base on the cast at apices of the first premolars in both sides
BAL: basal arch length is measured at the midline from the estimated anterior limits of the apical
base (estimated Downs A point on the cast) to perpendicular that tangent to the distal surface of
the two 1st
molars in both sides
BAL / TM: ratio of basal arch length to tooth material.
PMBAW%: ratio of premolar basal arch width to total tooth material,
PMBAW% = PMBAW x 100 / teeth material.
== for normal occlusion Howe believed that PMBAW should equal approximately 44% of
mesiodistal width of 12 teeth if it is sufficient to accommodate all the teeth

10. 10
Dr. Mohammed Alruby
37% or less: it indicates the need for extraction
37% - 44%: border line cases
44% or more: non extraction and according to other factors
== when PMBAW is greater than PM coronal arch width, expansion of the premolars may be
undertaken safely
But when PMBAW is lesser than PM coronal arch width, expansion is contraindicated, teeth move
distally, and extraction is indicated.
== when BAL / TM ratio is less than 37%, Howe considered that is due to basal arch deficiency
necessitating extraction of premolars
== it is useful in planning treatment of problem with suspected apical base deficiency whether to
be: extraction, OR, expansion. Or, split of the palate
Kesling diagnostic set up:
1953, Harold D Kesling, after developing tooth positioner as an aid in finishing orthodontic
treatment, suggested that cutting and repositioning of the teeth in duplicate study models of the
malocclusion would allow simulation of the results before starting the orthodontic treatment.
Objectives:
1- It is useful in difficult space management problems to ascertain before orthodontic
treatment is begun, the amount and direction of each tooth must be move.
2- It is best mathematical representation of the problem during the mixed dentition
3- It is popular practical technique for visualizing space problem in three dimensions in
permanent dentition is that of cutting off the teeth from a set of casts and resting them in a
more desirable position, this procedure is called diagnostic set up or kesling set up, or
prognostic st up.
4- It will demonstrate the amount of space created by the extraction and the tooth movement
necessary to that space
5- It also aids in choosing which tooth is extracted
6- Type of anchorage used in treatment
N: B:
The recording casts are not used for this technique since they must be saved for comparison with
diagnostic set up
Procedure:
The ideal position of lower central incisors is determined by using tweed’s analysis. With
the help of lateral cephalometric tracing the desired position of the lower central incisor is
determined by FMA or FMPA and IMPA angles. The long axis of mandibular incisors MI is set at
90 degree to mandibular plane MP, as FMPA is 25 degree in those cases.
= As the FMPA is increased by 1 degree, incisors are set 1 degree lingual or 89 degree to
MP, this was maintained until the angle reached about 33 degree, at which point the incisors would
be placed at -8 degree or 82 degree to MP
= as FMPA exceed than33 degree, the -8 degree was maintained because Kesling conviction,
that -8 degree was the maximum lingual position possible for incisors, similar limitation was
observed in the labial positioning using +5 degree as maximum labial position, SO:
FMPA 20 = +5 IMA
FMPA 21 = +4 IMA

11. 11
Dr. Mohammed Alruby
FMPA 22 = +3 IMA
FMPA 23 = +2 IMA
FMPA 24 = +1 IMA
FMPA 25 = 0 IMA
FMPA 26 = - 1 IMA
FMPA 27 = - 2 IMA
FMPA 28 = - 3 IMA
FMPA 29 = - 4 IMA
FMPA 30 = - 5 IMA
FMPA 31 = - 6 IMA
FMPA 32 = - 7 IMA
FMPA 33 = - 8 IMA
In the lateral cephalometric radiograph, a dotted line is drawn from the apex of lower
incisors to make 65 degree angle with FH and then measure the horizontal distance from the incisal
edge of the lower incisors to this line
= The occlusal plane should have 15 degree to MP, SO when put the incisors on 90 degree to MP
it should make 90 degree +15 with the occlusal plane
1- the mandibular model is taken first, the teeth on left side of the model are dissected out
leaving only the most distal tooth, the right side is left untouched that serve as a guide for
repositioning of the teeth on the other side
2- A horizontal cut is made deep into the base of the model with spiral saw blade (cut is made
at A point and B point on the arch)
3- Using ribbon saw blade, vertical cuts are made between the incisors down to the original
horizontal cut, allowing two incisors to removed
4- A sufficient amount of root portion is removed to resemble the normal length of the root
5- The remaining teeth is also removed separated and carved
6- Wax is poured on the model at the area which teeth are removed
7- The incisors are set according to cephalometric analysis, then the canines set up
8- The teeth are set in normal position eliminating any crowding or rotation
9- If the space is sufficient the remaining posterior teeth are set but if there is lacking of space,
some of dental units need to be removed, So 1st
premolar is removed
10-If the 1st
permanent molar is not in correct position in the lower arch, should cut off and
reset in its correct position
11-Reset the upper arch in relation to the lower arch
12-The teeth are set in normal relationship with normal overjet and overjet and overbite
13-Compensation can be made for incisors inclination depending on the skeletal relationship
of maxilla and mandible, as in class II skeletal relationship the maxillary incisors may be
slightly retroclined
14-If the 2nd
molar are erupted they are removed from the casts and placed in contact with the
1st
molars and in good occlusion
15-Red wax or pink wax is flown around the set teeth, the wax is trimmed polished and carved
so as simulate the gingiva
Peck and Peck analysis:

12. 12
Dr. Mohammed Alruby
Harvey Peck and Sheldon Peck 1971 stated that well aligned mandibular incisors possess
distinctive dimensional characteristic (smaller MD and larger FL diameter)
MD FL index = MD diameter / FL diameter x 100
Lower central: 88% - 92%
Lower lateral: 90% - 95%
If the index within this norm or less, ------- perfect alignment
If the index is higher than norm ------------ crowding (MD is more than FL so proximal stripping
can be done to relief crowding and correct tooth shape deviation)
For Egyptian people:
Lower central: 88.2% -+ 0.5
Lower lateral: 92.3% -+ 0.6
Harvold’s symmetrograph:
The symmetrograph is transparent plastic device with an inscribed grid, may be purchased or
made
Objectives:
1- Quickly determination of arch a symmetry (anterior posterior and transverse)
2- Determination of drifting, tipping and rotation of individual teeth
3- Useful in planning individual tooth movements
4- Determination of appliance design
Steps:
- Place the maxillary cast on its base and carefully
mark the median palatine raphe with a series of tiny
dots
- Orient the symmetrograph so that its midline
is directly superimposed over the midline raphe
and parallel to the occlusal surface
- Total and partial arch symmetry are quickly visualized
and localized as are drifting, tipping and rotation
of individual teeth
- A similar analysis of the mandibular dentition
is likely to be bit less precise since the mandibular
lingual frenum is not as reliable a median structure
as the median palatine raphe
Mixed dentition analysis:
The purpose of mixed dentition analysis is to evaluate the amount of space available in the arch
for eruption of permanent teeth and occlusal adjustment
To complete an analysis of the mixed dentition these factors must be noted:
1- The sizes of all permanent teeth anterior to 1st
molar
2- Arch perimeter
3- Expected changes in arch perimeter
Many methods of mixed dentition analysis have been suggested, however, all fall into two
strategies:
1- Those in which the sizes of the unerupted cuspids and premolars are estimated from
measurements of the radiographic image

13. 13
Dr. Mohammed Alruby
2- Estimation from the proportionality tables, those in which the sizes of the cuspids and
premolars are derived from knowledge of the size of permanent teeth already erupted in
mouth
3- Combination of the radiographic and prediction table methods
Nance mixed dentition analysis:
Nance concluded as a result of comprehensive studies, that, the length of the dental arch
from the mesial surface of 1st
mandibular permanent molar to the mesial surface of the
corresponding tooth on the opposite side is shortened during the transition from mixed to
permanent dentition
The average Leeway space is 1.8mm in upper arch exists between the MD width of primary canine,
1st
, 2nd
primary molar and the corresponding permanent teeth and 3.4mm in lower arch
Technique:
Space needed:
Space to accommodate all the permanent teeth anterior to the 1st
molars
- The width of the erupted four mandibular incisors is measured (actual width not the space
occupies in the arch)
- The width of unerupted mandibular canine and premolars on the radiographs is measured
- The estimated measurement is recorded
If one of the premolars is rotated, the measurements of the corresponding tooth on the opposite
side of the mouth may be used
Space available:
- A piece of 0.026-inch brass ligature wire contoured to arch surface from the mesial surface
of 1st
permanent molar to the other in opposite side
- The wire should pass over the buccal cusps of posterior teeth and incisal edges of anterior
teeth
Advantages:
1- The results with minimal error
2- It can be performed with reliability
3- It allows analysis of both arches
Limitations:
1- Time consuming
2- Need complete mouth radiograph
G W Huckaba analysis:
Introduced by George W Huckaba 1964.
With any type of radiograph, it is necessary to compensate for enlargement of the radiographic
image, this can be by measuring an object that can be seen both in radiograph and on the casts
usually a primary molar tooth.
Advantages:
1- Very easy, practical & relatively accurate method
2- Does not require any prediction table
3- Can be used in maxillary & mandibular arches
Disadvantage:
= Inherent distortion of radiographic image causes error
A simple proportional relationship can then be established as follow

14. 14
Dr. Mohammed Alruby
True width of primary molar X1 true width of unerupted premolar Y2
----------------------------------------- = ----------------------------------------------
apparent width of primary molar X2 apparent width of unerupted premolar Y2
OR:
Y1 = X1 x Y2 / X2
Accuracy is fair good depending on the quality of the radiographs and their position in the arch
SPACE AVAILABLE:
the arch is divided into segments which are approximately straight lines. The dimensions in each
of the segments is measured and added up.
SPACE REQUIRED:
for the un-erupted teeth is calculated from the radiographs. The discrepancy is calculated segment
wise
Moyers analysis:
There is a high degree of correlation between the sizes of different group of teeth in a
particular individual, by measuring one group of teeth it is possible to predict the sizes of the other
group with a fair degree of accuracy
Introduced by Moyers 1967, he estimates the sizes of unerupted cuspids and premolars from the
sizes of the permanent teeth that already erupted in the mouth by using a prediction tables for
upper and lower
He measures the MD widths of lower incisors and the predict the sizes of the unerupted premolar
and canines in both upper and lower arches by using two probability charts one for upper and the
other for lower
He used the lower incisors because:
1- They erupt early in the mouth in mixed dentition stage
2- Upper incisors have much variability in sizes
3- The upper incisors correlation with other group of teeth have a low prediction values
He recommended the use of 75% level of probability for prediction
Procedure:
The following procedure has been suggested by Moyers to determine the space available of
unerupted teeth
- Measure the greatest mesiodistal width of arch of four mandibular incisors with the aid of
Boley gauge and record the value
- Determine the amount of space needed for the alignment of the incisors as follow:
Set the boley gauge to a value equal to the sum of the widths of right central and lateral
incisors
Place one point of the gauge at midline between the central incisors and let the other point
of the gauge lie along the line of the dental arch on the right side
Mark on the tooth or the cast at precise point where the distal end of boley gauge has
touched, the marked point represents the point where the distal surface of lateral incisors
will be when it has been aligned properly.
Repeat the procedure for the opposite side of the arch
- Determine the space available for the permanent canine and premolars after incisors
alignment. This may be accomplished by measure the distance from the point mark on the
line of arch to the mesial surface of 1st
permanent molar.
This distance is the space available for permanent canine and premolar as well as the 1st
permanent molar adjustment
- Determine the amount of space remaining in the arch for 1st
permanent molar adjustment

15. 15
Dr. Mohammed Alruby
- The estimated canine and premolars size value from the chart is subtracted from the
measured space. It must be assumed that the 1st
permanent molar will be move mesially on
each side unless restrained with holding appliance
- After all values are recorded, complete assessment of the space situation in both arches is
possible
- This analysis can be completed in the mouth or on the cast and also for both arches
Advantages of the probability charts:
1- It has minimal systemic error and range of error is unknown
2- It is not time consuming
3- It is not requiring special equipment or radiographic projection
4- It used for both arches
5- It can be done with equal reliability by the beginner and experienced people
Limitations:
• It’s a probability analysis
• It does not account for tipping of mandibular incisors
• Maxillary teeth size is predicted by mandibular teeth
• It may have population variations, thus it cannot universally be applied
Johnston and Tanaka analysis: 1974
This method of arch analysis is a variation of Moyers analysis except that a table or chart
is not needed. The estimated widths in millimeters of the unerupted canines and premolars
correspond to the 75% level of probability in Moyers table
Procedure:
- The sum of the widths of the mandibular permanent incisors is measured and divided by 2
- For the lower arch add 10.5mm to estimate the mandibular canine and premolars for one
quadrant
- For the upper arch add 11mm to estimate the maxillary canine and premolars for one
quadrant
- As: if the width of lower incisors was 23mm, divided by 2 and add 10.5mm for lower arch,
so the result is 22mm and compared to 22.2mm from Moyers table
And for upper arch are 22.5mm for this analysis and 22.6 for Moyers analysis
== If the patient is not of the Northwestern European descent, Tanaka and Johnston space analysis
will either over-predict or under-predict the size of the unerupted teeth, this could cause serious
treatment planning problems
Ballard and Wylie analysis:
In 1902 Black measured a large number of human teeth and setup tables of mean figures for
each tooth in the dental arch. Ballard (1944) compared the mesiodistal width of teeth of one side
with those of corresponding teeth on the other side. The author concluded that lack of harmony
between tooth mass and the amount of supporting base was manifested in rotations and blocked
anterior teeth.
Ballard and Wylie (1947):
Studied the relationship of the mandibular incisors and the sum of the mandibular canine,
first and second premolars on plaster model of 441 cases. They found a moderate coefficient of
correlation. They made a formula to predict the sum of the mandibular canine, first and second
premolars.

16. 16
Dr. Mohammed Alruby
== The formula was X = 9.41+ 0.525 Y,
- where x equals the sum of the mandibular canine, first and second premolars of one side,
- Y equals the sum of the four mandibular incisors.
- The researchers found the estimated error from the use of their predictive formula about
2.6% or 0.6mm
Hixon and Old father analysis: 1956
= study was made on 41 children (15 males and 26 females)
= Developed a method of predicting the mesiodistal width of mandibular canine and premolars,
based on measurement of persons who participated in the Iawa facial Growth Study Subjects.
= The researchers measured the mesiodistal widths of the lower incisors on the cast for left side
and the mesiodistal widths of the first and second premolars from periapical radiographs. They
did not measure the width of lower canine from the radiograph, as they found it was difficult to be
measured on the radiograph.
= They predicted the mesiodistal widths of lower canines and premolars for one side from a
predicting chart using the sum of lower incisors and premolars
= repeat the step again for the other side
= it is very accurate technique but it is limited to lower arch
Staley and Kerber analysis: 1980
This method used both radiograph and measurements on dental casts
Do a revision on Hixon and Oldfather analysis on the same group of subjects
A radiograph was made of clinical use in the prediction of mandibular canine and premolar in
mixed dentition patients
This prediction graph is accurate to the nearest 0.1mm
Procedure:
1- Measure and add up widths of lower 1,2 incisors in one side
2- Measure width of unerupted premolars on same side
3- Sum of both together
4- Use the prediction graph to calculate widths of unerupted canine and premolar
= 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
Advantages:
1- Olfather’s measurements were taken on one side of the arch only, most commonly used left
side whereas measurements were taken on both sides of the arch for Staley anf Berker
method.
2- Hixon and Oldfather used only boley gauge that read to the nearest 0.1mm, whereas Helio
dial calipers read to the nearest 0.05mm were used in Staley and Kerber method
3- Premolars that were rotated on the radiograph were not measured in Staley and Kerber
method but were measured by Hixon and Oldfather
Metric analysis of arch form:
The standard values (often referred to as normal values) of the transverse arch width in the
premolar and molar region depend on the mesiodistal size of the four upper incisors. Comparing
the ideal values to the actual values the following deviation from the norm may occurs: narrowness
or broadness of dental arches
The correlation analysis is inaccurate if the SI is very large or very small and is influenced by
morphologic variabilities of upper incisors

17. 17
Dr. Mohammed Alruby
In these cases, the SI has to be correlated with the help of the Tonn formula using the sum of the
lower incisors width
The principle, the so called Pont relation discrepancies are only to be taken into account if larger
differences are present and should not be interpreted in isolation but only together with other
finding. These measurements are a guide not a goal
Sum of upper incisors SI:
The maximal mesiodistal width of each maxillary incisors are measured and the single values are
added together
If the upper central incisors are missing, determination may be made based on the sum of the lower
incisors width using the Tonn formula of all four upper incisors which calculates the appropriate
width
SIl X 4
SIu ------------ + 0.5 ----------------- Tonn Formula
3
Anterior and posterior arch width:
Measurements of dental arch after eruption of the 1st
premolars, the reference points for
measurements in the maxillary and mandibular arch are defined so that in an anatomically correct
occlusion, the upper and lower points are directly opposed
Definition of reference points:
Maxilla anterior: lower most point of the transverse fissure of the 1st
premolar
Maxilla posterior: point of intersection of the transverse fissure with the buccal fissure of the 1st
permanent molar
Mandible anterior: facial contact point between 1st
and second premolars
Mandible posterior: top of the middle buccal cusp of the lower 1st
permanent molar
The anterior arch width: the distance between the anterior reference point (premolar region)
The posterior arch width: the distance between the 1st
molars
The ideal values of anterior and posterior arch width are determined by using the Pont index
Measurement of dental arch width in the early mixed dentition:
The anterior arch width is measured in the region of the 1st
deciduous molars when primary teeth
are still present in the supporting zones
Definition of reference points:
Maxilla: posterior groove of 1st
deciduous molar
Mandible: disto-buccal cusp tip of 1st
deciduous molar
The posterior arch width is measured exclusively in the region of 6 years molar
The correlation between the ideal arch width and sum of upper incisors:
Ideal value anterior arch width: = SI x 100 / 85
Ideal value posterior arch width: = SI x 100 / 65
The deviation in the transverse development of the arch width is represented by the difference
between the actual and the standard value (normal)
Palatal height:
The palatal height according to Korkhus is defined as: a vertical line perpendicular to mid palatal
raphe which runs from the surface of the palate to the level of the occlusal plane
This is measured between the reference point of the Pont index for the posterior arch width
Korkhus 1939 evaluates palatal shape according to the index:
Palatal height index: = palatal height x 100 / posterior arch width = 42%
The index figure is increased when the palatal vault relative to the transverse arch development is
high and decreased when the palate is shallow

18. 18
Dr. Mohammed Alruby
A high palate is a principle features of apical narrowing of maxillary alveolar process which often
in cases of chronic mouth breathing, rickets, and in certain types of sucking habits
N: B:
= the measuring points are the distal end of the occlusal groove of the 1st
premolars
= and mesial pits on the occlusal surface of the maxillary 1st
molars
= distobuccal marginal angle on the 1st
premolars and highest point in the middle cusp of the
buccal cusps of the permanent molars in lower arch
Discrepancy calculations:
The difference between space required and the amount of space available for alignment of teeth is
determined by space required and the amount of space available for alignment of teeth is
determined by two different parameters:
1- Amount of dental crowding
2- Anterior posterior position of the incisors in relation to facial skeleton
Comprehensive space analysis must therefore consist of a combined analysis including
measurements from the cephalogram and study casts, the steps in this over all discrepancy
calculation in upper and lower arch are:
1- Determination of dental discrepancy: DD
On the study cast calculated:
a- The difference between the ideal and actual dental arch length
b- The amount of curve of spee separately on the right and left side
(to level the curve of spee by 1mm requires 1mm of arch length)
The sum of the measurements of a and b is known as the dental discrepancy DD
2- Determination of sagittal discrepancy: SD
The distance from the incisal edge of the central incisors to the N-pog line is measured on
the lateral cephalogram
The degree to which incisors position varies from the standard value represent the sagittal
discrepancy SD
A forward position of the incisors signifies need of dental arch length; retro position
signifies an increase in dental arch length (1mm change in incisors position on the lateral
cephalogram needs 1mm arch length)
3- Determination of total discrepancy: TD
Total discrepancy TD: is the sum of the dental arch and sagittal discrepancy. Since the
measurements is for both sides of the dental cast but for only one side on the radiograph, it
is calculated as: TD per side = SD + ½ DD
The amount of the total discrepancy is a significant parameter for deciding whether
extractions are necessary
If the discrepancy calculation is carried out in the mixed dentition growth related changes
in the position of the N-pog line must be taken into account, the type of mandibular rotation
N: B:
Symptoms of mesial position of posterior teeth:
1- Crowding and space loss
2- Dental midline shifts with crowding and space loss
3- Mesial tipping of premolars
4- Rotation of 1st
permanent molars
5- Relation of 1st
palatine rugea to canine according to Hausser ( 1st
palatine rugea distal to
canine = mesial position

19. 19
Dr. Mohammed Alruby
anterior arch length:
perpendicular from the most anterior labial surface of central incisors to the connecting lines of
the reference points of anterior arch width.
= anterior arch length altered by:
1- Malposition of anterior teeth
2- Migration of 1st
premolars
Anterior arch length in the maxillary arch is larger than mandibular one by the width of
labiolingual of the incisal edge of upper incisors