1. Arch space analysis methods estimate tooth size and jaw size relationships. Space analysis compares available space to required space for proper tooth alignment.
2. Methods are classified by tooth size estimation method, arch length estimation method, developmental stage, and estimation/digitization method.
3. Common methods include measurements from radiographs, prediction tables using erupted tooth sizes, and combinations of methods. Nance analysis accounts for space changes between deciduous and permanent dentitions.
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INTRODUCTION:-
Arch space analysis are methods by which
orthodontist can estimate and predict
tooth size/jaw size relationship. Since
malaligned and crowded teeth usually
result from lack of space, this analysis is
primarily of space within the arches. Space
analysis requires a comparison between
the amount of space available for the
alignment of the teeth and the amount of
space required to align them properly.
3. Classification:-
I
II Classification according to the method of arch length
estimation
III
Classification according to the developmental stage of
dentition.
Numerous methods have been proposed for arch length
analysis. These methods could be classified to:-
IV
Classification according to the method of estimation and
digitizing.
Classification according to the method of tooth size
estimation
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3. Combination of these methods.
2. Prediction based upon the correlation between the
mesiodistal dimensions of the erupted and non erupted teeth .
1. Methods which depend on the measurements from radiographs
I- Classification
according to the
method of tooth
size estimation
Classification
5. 3. Total space analvsis
these method include the use of cephalometric correction
, soft tissue modification and curve of occlusion
2. Cephalometric correction methods
the incisor reduction(IR) measurement is either add or
subtracted from the previous available space obtained
with the brass wire. This will Correct any labial or lingual
deviation of the lower incisors from the true basal bone.
e.g. Tweed's analysis
1. Conventional methods
these methods does not include the use of cephalometric
correction or soft tissue modification.
II- Classification
according to the
method of arch
length estimation.
Classification
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2. Methods used in permanent dentition stage
1. Methods used in mixed dentition stage
III- Classification
according to the
developmental
stage of dentition.
Classification
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2. Manual measurements and estimation.
1. Computerized arch length analysis
Arch length analysis methods also include Computer arch
length analysis which can be used to the variations from
the mean tooth size, actually set up the teeth, arch form
and treatment plan.
IV. Classification
according to the
method of
estimation and
digitizing
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Tooth size or Arch length Measuring Devices:-
Nance measured the arch perimeter on the
cast using 0.010 inch soft brass wire. He
adapted it on the middle third of the tooth and
called this the outside measurement. He also
used a divider to obtain the inside
measurements.
9. Sliding caliper (Helios style) used by
Hunter and Priest 1960 and compared
it with divider. They concluded that
divider gave larger readings than
sliding caliper.
10. Arch Length Analysis in Mixed
Dentition :-
1- Measurements of teeth on radiographics; this
#requires an undistorted radiographic image which is
so difficult even with individual films (periapical films)
specially with the canines.
So 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 the radiograph and on the casts.
,Usually a primary molar tooth, So this relationship
can be setup:
True width of primary maolar E1 = True width of Unerupted premolar E2
Apparent width of primary molar M1 Apparent width of unerupted premolar M2
Accuracy is fair to good depending on the quality of the
radiographs and their position in the arch.
11. 2- Estimation from proportionality tables
(1963):
There is a good correlation between the
size of the erupted permanent incisors
and the unerupted canines and
premolars. There data have been
tabulated by Moyers.
13. To utilize moyers prediction tables, The
mesiodistal width of the lower incisors is
measured and this number is used to
predict the size of both the lower and
upper unerupted canines and premolars.
The size of the lower incisors correlates
better with the size of the upper canines
and premolars more than the size of the
upper incisors because upper lateral
incisors are extremely variable teeth.
Accuracy with this method is fairly good.
14. Tanaka and Johnston,
Tanaka and Johnston have developed anther way
to use the width of the lower incisors to predict
the size of unerupted canines and premolars.
One half of the M.D Width of the four lower incisors
+ 10.5 → Estimated width of mandibular canine and premolars in one quadrant.
+ 11 mm → Estimated width of maxillary canine and premolar in one quadrant.
The method has good accuracy despite a small
bias toward overestimated of the unerupted
tooth sizes. It requires no radiographs or
reference tables which makes it very
convenient.
15. The estimated widths in millimeters of the unerupted
canines and premolars correspond to the 75%
level of probability in Moyers prediction table. For
example, if the width of the lower incisors was 23
mm, divide by 2 and add 10.5 mm for the lower
arch. The result is 22 mm compared with 22.2 mm
obtained from Moyers table. The corresponding
values for the maxillary arch are 22.5 turn for the
Johnston and Tanaka analysis and 22.6 from
Moyers table. It is then possible to take these
tooth mass predictions and compare them with the
total measured arch length and obtain any
redundancies or inadequacies in the arch length.
16. 3-Combination of
radiographic and prediction
table:
Since the major problem with using
radiographic images comes in
evaluating the canine teeth, it would
seem reasonable to use the size of
permanent incisors measured from the
dental casts and the size of unerupted
premolars measured from the films to
predict the size of unerupted canines.
17. 3-Combination of radiographic
and prediction table:
Since the major problem with using
radiographic images comes in evaluating
the canine teeth, it would seem reasonable
to use the size of permanent incisors
measured from the dental casts and the
size of unerupted premolars measured
from the films to predict the size of
unerupted canines.
18. The graph provided by Stalely and
Berber allows canine width to be read
directly from the sum of incisor and
premolar widths. This method can be
used only for the mandibular arch and
of course requires perapical
radiographs.
19. -Measurement of size of unerupted first and
second premolars in one mandibular
quadrant from periapical radiograph.
-Determination of mesiodistal tooth width of
the lower central and lateral incisors on
the study cast corresponding to the side of
radiograph.
-Formula:
S. 3+4+5= {(s.1+2+ x4+x5) 0.7158}+ 2.1267
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Hixon and Oldfather:-
They measured the mesiodistal widths
of unerupted bicuspids on the x-ray
film. Then added to them the size of
lower permanent incisors from the
casts. They termed the resultant "the
measured value" which is used to
determine the "estimated value" from
their prediction charts.
21. 4- Estimating method:
Sim (1972) pointed out that various tooth size charts
indicated that the mesiodistal width of a first bicuspid
is very nearly one third of the combined mesiodistal
widths of the cuspid and bicuspid in a quadrant. This
held true for both maxillary and mandibular arches.
So if the width of the first bicuspid could be
determined radiographically using the long cone
parallel technique with central ray perpendicular to the
first bicuspid to obtain accurate measurement and
multiplying this MD value x3 gives a reasonably
accurate estimation of the total space requirement for
that cuspid-bicuspid segment.
22. 5- Fouda's method: (1989)
This method based on the use of the
buccolingual width of the first permanent
molar to predict the mesiodistal dimension of
the unerupted cuspid and bicuspids.
Upper arch: M.D dimension of 345 = (B.L dimension of 6 x2) -1
Lower arch: M.D dimension of 345 = (B.L dimension of 6 x2)
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Procedures:
The B.L dimension of the first permanent molar
was measured as the maximal distance
between the buccal and lingual surfaces
perpendicular to the mesiodistal diameter of
the tooth and parallel to the occlusal plane
down to the border of gingival on the cast.
All the measurement were made to the teeth
with well ground poly-gauge, then apply the
equation.
24. 6-Nance Analysis:-
Nance concluded, as a result of comprehensive
studies, that the length of the dental arch
from the mesial surface of one 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.
25. Nance further observed that in the average
patient's mandibular arch a leeway of 1.7 mm
per side exists between the combined
mesiodistal widths of the primary mandibular
canine and first and second primary molars and
the mesiodistal widths of the corresponding
permanent teeth, the primary teeth being larger.
This difference between the total mesiodistal
widths of the corresponding three primary teeth
in the maxillary arch compared with the three
permanent teeth that succeed them is only 0.9
mm per side.
26. Procedures:
1- Measure with a pair of dividers the mesiodistal
widths of two deciduous molars and the deciduous
canine or the amount of space which these teeth
occupy in the dental arch.
2- using the dividers measure the greatest
mesiodistal width of the premolars and permanent
canine as shown on long cone X-ray film
technique as the central ray of the X-ray tube
should be focused to pass directly between the
contact points of the teeth.
3- Compare the two dimensions; the difference
between them is the lee way space of Nance.
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Currently the Nance arch-length analysis is seldom
used, partly because the involved procedures for
this analysis require a complete set of periodical
radiographs. The clinical reliability of other analyses
that do not utilize radiographs is sufficient for
determining major arch-length inadequacies.
By Nance method the available space should be
equal to mesiodistal width of the permanent incisors
+ the mesiodistal width of unerupted canine and
premolars + 1.7 mm in the mandibular arch and 0.9
mm maxillary arch in each quadrant.
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Cephalometnc correction methods :-
Tweed's analysis (Tweed's triangle):-
Tweed triangle is formed by the Frankfort horizontal
plane, mandibular plane and a line drawn through
the long axis of the most protrusive lower incisor.
The Frankfort mandibular incisor angle (FMIA): Is
Formed by the Frankfort plane and the line drawn
through the long axis of the mandibular incisor. .
Tweed's belief that the ideal relationship of the lower
incisors to the Frankfort plane should give an
angle of 65°.
29. Available space is obtained directly from the mouth.
Required space, the teeth are individually measured
and all lost space occasionally by rotations or
blocked out teeth recorded.
For the required space, the mesiodistal breadths of
the four lower incisors are transferred from the
mouth.
The mesiodistal breadths of the unerupted
mandibular cuspid, first and seconds bicuspids
are taken from X-ray.
A lateral head plate is made of the patient and the
triangle is down on the head plate with white ink.
Tweed method: (1954)
30. dotted line starting at the apex of the mandibular incisor is
drawn upward intercept the Frankfort plane at angle of 65º.
The distance between the solid line which is the existing
inclination of the mandibular incisor and the dotted line
(measured at the incisal edge) is the distance in mms that the
mandibular incisors must be tipped lingually.
Or, multiply the difference of FMIA of the patient from the ideal
measurement (65º) by 0.4 mm, i.e 1º = 0.4 mm.
Arch length will be decreased the difference of the 2 angles (in
mm) and multiplied by 2 (for both sides).
31. -If the discrepancy reach an amount as much as
the mesiodistal breadths of both mandibular first
bicuspid teeth this means that the malocclusion is a
clear cut extraction case of a most severe nature and that
perhaps it might be best to start some treatment on the
near future and that perhaps maybe serial extraction.
This may prevent the development of a serious
malocclusion and minimizing the mechanics of
treatment to a great extent when all the permanent teeth
have erupted.
32. -If the difference was only 4 mm
inclinations of the mandibular first permanent
molars is noted, if they are mesially tipped, it
would be possible to regain 2 mm of space on
either side by tipping them distally.
-If the discrepancy turns out to be 10 – 15
or 20 mm on realize that the patient must loose
four bicuspids
33.
34. LOGO
Determining the tooth mass discrepancy:
a- Available space:
The Linear measurement from the mesial of the first molar on
one side to the mesial of the first molar on the opposite side is
measured with a brass wire. The wire is easy contoured so that
it runs along the buccal cusps of the premolars and the incisal
edges of the anterior teeth. This wire is laid along a millimeter
ruler and the measurement is recorded.
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An assessment- of the relations between the
axial inclination of the mandibular incisors and
the basal bone was made on a tracing of the
lateral cephalogram. The amount of
alveolodental protrusion or retrusion was
assessed and incorporated into the mixed
dentition analysis.
A line drawn from the apex of the most
procumbent lower incisor to a point 65° on the
Frankfort plane is known as the incisal
reduction.(IR),
36. LOGO
Tweed Foundation research has established the following
relationships:
When the FMA is between 21° and 29°, the FMIA should be
68° degrees.
When the FMA is 30° or greater, the FMIA should be 65°.
When the FMA is 20° or less, the IMPA should not exceed
92°.
• When the line falls lingual to the mandibular incisor or if
FMIA less than 65°, the reading is a minus and indicated
the lower teeth are in procumbent relationship to the basal
bone.
• When the IR line lies labial to the lower incisors, or if FMIA
greater than 65~, the reading is a plus and indicates, the
mandibular incisors are in a lingual axial relationship to the
basal bone.
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If for a specific FMA '(30°) the FMIA (49o) did not
correspond, an objective line was traced to form
the required FMIA (65°). Then the distance
between this objective line and the line that passed
through the actual axial inclination of the
mandibular incisors was measured on the occlusal
plane with pointed calipers to the nearest 0.1 mm
(6 mm). This figure was multiplied by 2 to include
right and left sides (12 mm).
• The IR number must be multiplied by 2 because
the mandible is elliptical in shape (on either side of
the dental arch).
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b-Correcting the available space:
The IR measurement is either adds or
subtracted from the previous
available space obtained with the
brass wire. This will Correct any
labial or lingual deviation of the lower
incisors from the true basal bone.
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c- The required space:
The sum total of the mesio-distal widths of each
tooth mesial to the first molars.
-If the required space is less than the corrected
available space: The tooth mass discrepancy is
recorded a plus figure.
-When the required space is greater than the
corrected available space: The tooth mass
discrepancy is recorded as a minus figure.
A minus tooth mass discrepancy indicates a lack of
the clinical linear measurement.
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Note; In Permanent dentition ,Tweed's
analysis for permanent teeth is the same
as that of the mixed dentition except that
one measures directly in the mouth of the
patient the extent of the loss in arch
length.
41. - Huckaba:-
Provides a technique for mixed dentition analysis that compensates
nicely for radiographic enlargement of tooth images in periapical
films is available
It is based on the assumption that the degree of imagination for
primary tooth will be the same as that for its underlying permanent
successor on the same film
Procedures
Measure the width of the primary tooth on the x-ray film (y') and the width of its
underlying permanent successor on x-ray film.
Measure the primary tooth (Y) directly in the mouth or on the dental cast.
The width of the unerupted permanent tooth (x) can then be
calculated by simple mathematical proportion
x: x'= y:y' or x= X'Y
Y‘
- This procedure is particularly useful when planning treatment for
space supervision problems in which every fraction of a millimeter
must be accounted for.
42. - Kaplan, Smith and Keriark:-
Modified Hixon and Oldfather method by
excluding the lower incisors. This method
necessitate only measuring the sum of
lower central incisors and mesiodistal
widths of first and second bicuspids from
x-ray film. To overcome Hixon-old father's
overprediction they have suggested
adding 0.3 mm to value below 20 mm and
0.4 mm to values 20-22 mm and 0.5 mm
to values 23 mm and above.
43. Ingervall and Lennartsson1978):-
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proposed a method for prediction the size
of unerupted canine and bicuspids. They
measured the buccolingual width of upper
permanent first molar on the casts and
correlate this value with the size of
unerupted canine and premolars
measured in radiograph.
44. -El-Kattan and Eid:-
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tried to overcome the over or under
prediction of other ways for mixed
dentition analysis by producing an
Egyptian probability charts. These charts
entailed the use of each lower incisor and
the upper incisors to predict the unerupted
canines and premolars.
45.
46. 1-Nance Analysis:-
One of the methods that has been used
traditionally to obtain perimeter is a brass
wire contoured over the buccal cusps and
incisal tips of lower teeth from molar to
molar and then straightened out to be
measured.(called this outside measurements
47. Nance(1947) measured the arch perimeter on the
cast using 0.010 inch soft brass wire. He
adapted it on the middle third of the tooth and in
order to held the wire stable on the cast in this
position he bent the ends of the wire into the
embrasure between the first permanent molar
and the second deciduous molar tooth .
He also used a divider to obtain the inside
measurement the distance of which was from
the lingual aspects of the teeth gingivally.
**the anterior extreme of this measurement was
between the mandibular centrals while the
posterior one was at the mesiolingual line angle
of the lower first molar.
48. ARCH CIRCUFERENCE
ANALYSIS OF THE DENTITION & OCCLUSION
By Debora Priestap, Michelle J. Thornberg, Michael L. Riolo From Riolo, M. and Avery, J. Eds., Essentials for Orthodontic Practice,
EFOP Press of EFOP, LLC. Ann Arbor and Grand Haven, Michigan, U.S.A., 2003. CHAPTER 13 Pages 315-370
49. As currier (1969) pointed out however
using the cusp tips ,the central fossa line
or that are described by lingual cusps of
the teeth produces different geometric
forms and different arch length so the
wire should be contoured along the line
of occlusion (centeral fossa line of the
upper and the B cusp line of the lower).
50. The brass wire method requires considerable
judgment as to the proper arch from.
Another method is to use a bow divider to
measure segments along the arch at the
alveolar crest and add the segments.
51. used the cast only using a vernier caliper with
sharp points, He divided the arch of each jaw
into sex segments that is (1, 2 - 3, 4 - 5, 6
segments at both sides) he measured median
diastema if present separately and added it to
the previously gained six measurements.
The measurements was made at the contact
points of the teeth, ended at the distal
surfaces of the first permanent molar.
Landstrom (1949)
52. Murich and Ackerman (1973)
have suggested the use of
a hanging chain which
automatically establishes
a catenary curve for arch form
as a rapid and reliable method
for establishing mandibular dental arch perimeter.
A catenary curve beginning from the mesiobuccal
cusps of molars, buccal cusps of premolars,
cuspids and incisal edges of incisors till reaching
the opposite molar.
53. After calculating the require space to establishing the
space analysis another aspect that must be considered
in this analysis is the curve of spee.
If the curve of spee is basically flat, there is no influence
on the space analysis.
If however there is a deep curve of spee which the
orthodontist plans to flatten, additional arch perimeter
is needed for each mm of leveling of the curve of
spee. A deep curve of spee is frequently accompanied
by mandibular posterior teeth that are tipped mesially.
55. A) Relationship of groups of teeth:
1-Peck 2 Peck (1972): #They suggest a method for determining
whether lower incisor teeth are excessively wide mesiodistally.
They suggest that the ratio between the faciolingual dimension of
the mandibular incisor and its mesiodistal dimension should be
approximately one to one (1:1).
If the mesiodistal is considerably greater than the faciolingual
dimension they recommend stripping.
Since the greatest faciolingual dimension is likely to be subgingival
this measuremeat should be made intraorally rather than on the
casts.
The chief rationale for the Peck concept is stability of rotational
corrections of lower incisors rather than tooth size
considerations.
56. 1- Peck and Peck analysis :-
•It is used for determining whether lower
incisor teeth are excessively wide
mesiodistally.
•They suggest that the ratio between the faciolingual
dimension of the mandibular incisor and its
mesiodistal dimension should be approximately 1:1.
-If the mesiodistal dimension is greater than the faciolingual, they
recommend stripping. Since the greatest faciolingual dimension
is likely to be subgingival, this measurement should be made
intraorally rather than on the casts.
The chief rationale for the peck concept is stability of rotational corrections of
lower incisors rather than tooth size considerations. If the Bolton analysis
and the peck analysis both indicate a need to reduce the width of the
lower incisors, this is strong evidence for the necessity of performing
interproximal stripping.
A) Relationship of groups of teeth:
57. For good occlusion, the teeth must be
proportional in size. If large upper
teeth are combined with small lower
teeth, as in a denture setup with
mismatched sizes, there is no way to
achieve ideal occlusion.
Contemporary Orthodontic 2007
2- Bolton analysis
58. In order to achieve a good occlusion
with the correct overbite and overjet,
the maxillary and mandibular teeth
must be proportional in size. The
mesio-distal widths of teeth were
first formally investigated by G.V.
Black in 1902. He measured a large
number of human teeth and set up
tables of mean dimensions, which
are still used as references today.
Journal of Orthodontics, Vol. 33, 2006, 45–51
59. Bolton in 1958 studied the tooth-size disharmony
(TSD) in relation to treatment of malocclusion.
He evaluated 55 cases with excellent
occlusions. Bolton developed 2 ratios for
estimating TSD by measuring the summed
mesio-distal (MD) widths of the mandibular to
the maxillary anterior teeth.
Overall ratio=
Sum of MD widths of mandibular 12 teeth (first molar-first molar) x100
Sum of MD widths of maxillary 12 teeth (first molar-first molar)
Anterior ratio=
Sum of mandibular anterior 6 teeth x100
Sum of maxillary anterior 6 teeth
60. It is used to indicate the deviation from
the ideal of any measured ratio and
thus the size of the discrepancy.
Bolton concluded that these ratios
should be 2 of the tools used in
orthodontic diagnosis, allowing the
orthodontist to gain insight into the
functional and aesthetic outcome of
a given case without the use of a
diagnostic setup.
61. In a subsequent paper, Bolton
expanded on the clinical
application of his tooth size
analysis. Bolton’s standard
deviations from his original
sample have been used to
determine the need for reduction
of tooth tissue by interdental
stripping or the addition of tooth
tissue by restorative techniques.
62. The traditional methods of measuring mesio-
distal widths of teeth on dental casts can be
described as manual methods and have either
employed needle-pointed dividers or a Boley
gauge (Vernier callipers).
63. Tooth size analysis is carried out by
measuring the mesiodistal width of
each permanent tooth. A standard
table (Table A) is then used to
compare the summed widths of the
maxillary to the mandibular anterior
teeth and the total width of all upper
to lower teeth (excluding second and
third molars).
Contemporary Orthodontic 2007
64.
65. If the overall ratio exceeds 91.3, the discrepancy
is in excessive mand. Arch length.
The difference between the actual and correct
mand. Measurement is the amount of excessive
mand. Arch length.
If the overall ratio exceeds 91.3;
Actual mand. ”12” _ correct mand. “12” = excess mand. ”12”.
If the overall ratio is less than 91.3;
Actual maxi. ”12” _ correct maxi. “12” = excess maxi.”12”.
If the anterior ratio exceeds 77.2 ;
Actual mand. “6” _correct mand. “6” =excess mand. “6”
If the anterior ratio is less than 77.2;
Actual maxi. “6” _ correct maxi. “6” = excess maxi.”6”
66. A quick check for anterior tooth
size discrepancy can be done by
comparing the size of upper and
lower lateral incisors. Unless the
upper laterals are larger,
a discrepancy almost surely exists.
A quick check for posterior tooth size
discrepancy is to compare the size of upper
and lower second premolars, which should be
about equal size. A tooth size discrepancy of
less than 1.5 mm is rarely significant, but
larger discrepancies create treatment
problems and must be included in the
orthodontic problem list.
Contemporary Orthodontic 2007
67. In his second paper, Bolton discussed the
effect of premolar extraction on the overall
ratio. Bolton correctly stated that premolar
extraction would mathematically reduce
the suggested overall mean ratio value of
91.3%. After the extraction of 4 premolars,
patients in whom no TSD existed would
have an overall mean ratio of 88%.
Journal of Orthodontics, Vol. 33, 2006, 45–51
73. 3- Sanin-Savara tooth analysis:
Sanin and Savara and colleagues devised a
simple and ingenious procedure to identify
individual and group tooth size disharmonies.
It makes use of precise mesiodistal
measurements of the crown size of each tooth,
appropriate tables of tooth size distributions in
the population and a chart for platting the
patient's measurements.
The teeth should be measured with a finely
pointed Boley gauge.
74. B) Relationships of tooth size to size of supporting structures
ASHLEY HOWE'S ANALYSIS
Howes devised a formula for determining
whether the apical bases could
accommodate the patient's teeth.(reported
that crowding not result from excessive tooth
material only, but also from inadequate
apical base.)
75. Procedures:
Tooth material (TM) equals the sum
of the mesiodistal width of the
teeth from the first permanent
molar to the first molar (12 teeth).
Premolar diameter (PMD) is the
arch width measured at the top of
the buccal cusps of the first
premolars.
Premolar diameter to tooth material
ratio (PMD/TM) is obtained by
dividing the premolar diameter by
the sum of the widths of the 12
teeth.
76. Basal arch length (BAL) is
measured at the midline
from the estimated
anterior limits of the apical
base to a perpendicular
that is tangent to the
distal surfaces of the two
first molars.
The ratio of basal arch
length to tooth material
(BAL/TM) is obtained by
dividing the arch length by
the sum of the widths of
the teeth.
77. #Premolar basal arch width (PMBAW) is
obtained by measuring with the bowed
end of the Boley gauge the diameter of
the apical base on the dental casts at the
apices of the first premolar.
The ratio of the premolar basal arch to tooth
material (PMBAW/TM) is obtained by
dividing the premolar basal arch width by
the sum of the width of the 12 teeth.
78. Howes believed that the (PMBAW) (he called it
the canine fossa diameter) Should equal
approximately 44% of the mesiodistal widths of
the 12 teeth in the maxilla if it is to be
sufficiently large to accommodate all the teeth
(i.e no extraction).
79. When the ratio between basal arch width is
less than 37%, Howes considered this to
be a basal arch deficiency necessitating
extraction of premolars.
When the ratio between basal arch width is greater
than the premolar coronal arch width, expansion
of the premolars may be undertaken safely.
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80. Since this method was introduced, rapid
palatal expansion has come into more
common use.
Howes analysis is useful in planning
treatment of problems with suspected
apical base deficiencies and deciding
whether to:
1-Extract teeth 2-Widen the dental arch
3-Expand rapidly the palate
81. According to Ashley Howe, to determine whether the
apical bases of the patient could accommodate the
patients' teeth, the following measurements have to
be obtained:
1. Percentage of premolar diameter to tooth
material is obtained by dividing the PMD by
the total tooth material.
PMD
--------- x 100
TTM
82. 2. Percentage of premolar basal arch width
to tooth material is obtained by dividing the
premolar basal arch width by the total
tooth material.
PMBAW
----------- x 100
TTM
83. Percentage of basal arch length to tooth material is
obtained by dividing the basal arch length by
total tooth material.
BAL x 100
---------
TTM
Comparison between PMBAW and PMD gives an
idea of the need and the amount of expansion
required and PMBAW% gives an indication
towards an extraction or non-extraction
treatment plan.
84. a. If the width between the canine fossa is
greater than the width of the premolars
(PMBAW > PMD), it is an indication that
basal arch is sufficient to allow expansion of
the premolars. If the canine fossa width or
PMBAW is less than PMD there can be 3
possibilities:
• Don't treat.
• Move teeth distally to wider part of the arch.
• Extract some teeth.
Inference
85. b. According to Howe, to achieve a normal
occlusion with a full complement of teeth
the canine fossa measurement (PMBAW)
should be 44 percent of the sum of the
maxillary tooth diameter. When this ratio is
between 37 percent and 44 percent,
extraction of first premolars is doubtful,
and the case is considered to be in the
borderline category.
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86. When it is less than 37 percent, then it
is considered to be definitely a case for
first premolar extraction as it is a basal
arch deficiency. Any value, 44 percent or
above indicates a non-extraction case.
Therefore, this analysis is a useful
treatment planning tool and helps to
determine whether to extract or expand.
87. LOGO
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Diagnostic setup: (kesling diagnostic method 1956)
HD Kesling introduced the diagnostic set-up
which is made from an extra set of trimmed
study models . The diagnostic helps the clinician
in treatment planning as it simulates various
tooth movements, which are to be carried out in
the patient.
88. LOGO
Diagnostic setup: (kesling diagnostic method 1956)
It is useful in difficult space management
problems to accertain before orthodontic
treatment is begun precisely the amount and
direction each tooth must be moved.
It is a popular practical technique since they
must be saved for comparison with the
diagnostic setup and with progressive record
casts.
89. LOGO
Procedures:
1-Obtain an accurate wax bite, trim the posterior portion
of the bases of the casts with the wax bite interposed so
the bases are flush.
2-Drill a hole through the alveolar portion of the cast well
below the gingival margin of the teeth.
90. LOGO
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3-Insert a fine saw blade through the hole and cut
up to the crest of the gingival margin between two
of the teeth. Cut along the line of the arch well
beneath the gingival margin of the teeth and come
up again at the point of the gingival crest below the
contact point on the opposite side of the tooth.
Repeat this for the teeth to be cut off the cast.
92. LOGO
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Do not cut through the contact points, cutting up to the
gingival crest will permit gentle breaking of the plaster
without damage.
Align the teeth and wax them into the desired positions, it
is best not to cut off all of the teeth so that the bite
relationship can be kept.
One may combine the cephalometric analysis and
prediction of incisal positioning and angulation with
prognostic setup as a means of visualizing incisor profile
relations and as an aid in the selection of teeth for
extraction.
94. LOGO
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A more accurate method involves taking a wax bite
in the retruded contact position mounting the casts
on an adjustable articulator and finishing the
diagnostic setup within the limits of the jaw
relationships thus imposed.
When extractions are contemplated as part of the
orthodontic treatment, the diagnostic setup will
demonstrate vividly the amount of space created
by the extractions and the tooth movements
necessary to close the space. it will also aid in
choosing which teeth to extract.
95. *The procedure is as follows :
• Dental cast is related to FMlA
• Constant FMIA = 65° and find ideal position
of mandibular incisors mesiodistally.
• Align both the lower central and lateral
incisors on the lower cast at FMTA= 65°
• Mandibular incisors are placed at right
angles to mandibular plane.
• Canines are the next teeth to be positioned.
*KESLlNG DIAGNOSTIC SET-UP
96. • First and second premolars are then set on
the model.
• If the remaining space on each side is
adequate to receive the permanent first
molars, then extraction is not required.
• If space is inadequate and amounts to
more than can be gained by uprighting the
permanent second molars, then some
teeth must be removed usually the first
premolar.
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97. When the mandibular set-up is completed,
the maxillary teeth are cut from their base
and repositioned, then articulated to the
mandibular set-up.
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98. Company Logo
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*Uses of Diagnostic Set-up
1. Aids in treatment planning as it helps to
visualize tooth size-arch length
discrepancies and determine whether
extraction is required or not.
2. The effect of extraction and tooth
movement following it, on occlusion can
be visualized.
3. It also acts as a motivational tool as the
improvements in tooth positions can be
shown to the patient.
99. PONT'S ANALYSIS
*In 1909 Pant presented to the profession
a system whereby the mere
measurement of 4 maxillary incisors
automatically established the width of the
arch in the premolar and molar region.
The greatest width of the incisors is
measured with calipers recorded on a
line, and their sums then recorded in
millimeters. This is termed as Sum of
Incisors (SI) .
100. The distance between the upper right first premolar and upper left
first premolar (i.e. the distal end of the occlusal groove) is
recorded and called as Measured Premolar Value (MPV).
The distance between the upper right first molar and upper left first
molar (i.e. the mesial pits on the occlusal surface) is recorded
and is termed as Measured Molar Value (MMV).
whereas on the mandibular teeth the points used are the
distobuccal cusps of the first permanent molar.
101. Calculated premolar value (CPV) The expected
arch width in the premolar region is calculated
by the formula:
SI x 100
-------
80
Calculated molar value (CMV) The expected
arch width
in the molar region is calculated by the formula:
SI x 100
-------
64
102. The difference between the measured and calculated
values determines the need for expansion.
If measured value is less, expansion is required.
Pont's index gives an approximate indication of the
degree of narrowness of the dental arches in a case
of malocclusion and also the amount of lateral
expansion required for the arch to be of sufficient
size to accommodate the teeth in perfect alignment.
103. *Drawback of Pant's Analysis
1. Maxillary laterals are the teeth most commonly
missing from the oral cavity.
2. Maxillary laterals may undergo morphogenetic
alteration like 'peg' shaped latera1.
3. This analysis is derived solely from the casts of the
French population.
4. It does not take skeletal malrelationships into
consideration.
104. 5. It may be useful to know the desired maxillary
dimension for a case, but it is more difficult to
achieve the corresponding mandibular dimensions
that are necessary to maintain a balanced occlusal
relationship.
6. Pont's index does not account for the relationship
of the teeth to the supporting bone, or the
difficulties in increasing the mandibular
dimensions.
*Drawback of Pant's Analysis
105. %- LINDER HARTH INDEX:-
Linder Harth Proposed an analysis, which is
very similar to Pont's analysis. However he
made a variation in the formula to determine
the a calculated premolar and molar value.
The calculated premolar value is
determined using the formula:
the calculated molar values is detained using
the formau;
where SI= sum of mesiodistal width of
incisors.
85
100
x
SI
64
100
x
SI
106. 7- KORKHAUS ANALYSIS:-
This analysis makes used of the Linder Harth's
formula to determine the ideal arch width in the
premolar and molar region. An additional
measurement is made from the midpoint of the
inter- premolar line to a point in between the two
maxillary incisors. According to Korkhaus, for
given width of upper incisors a specific value of
the distance between the midpoint of
interpremolar like to the point between the two
maxillary incisors should exist. In case of
proclined upper anteriors, an increase in this
measurement is seen while a decrease in this
value denotes retrolined upper anterior.
107. A comparison between sonic digitization (DigiGarph TM Workstation) and the
digital caliper
EJO 20 (1998) 653-661 space analysis; a comparison between sonic digitization (DigiGarph TM Workstation) and the digital caliper
Arch perimeter was measured, in 45 sets of
plaster casts of southern Chinese children(mean
age 12.5 years), using calipers in six segments
from the distal of the first permanent molar to it’s
antimere in each arch. The total Mesiodistal
width of all teeth, excluding second and third
molars, were also measured. Sonic digitization
of the study casts was completed according to
the instructions of the DigiGraoh TM software.
110. EJO 20 (1998) 653-661 space analysis; a comparison between sonic digitization (DigiGarph TM Workstation) and the digital caliper
Preparation of the study cast using the
pendix machine
Digitization using the modified platform
111. EJO 20 (1998) 653-661 space analysis; a comparison between sonic digitization (DigiGarph TM Workstation) and the digital caliper
112. EJO 20 (1998) 653-661 space analysis; a comparison between sonic digitization (DigiGarph TM Workstation) and the digital caliper
113. Compared with manual measurement , there
was en over estimation of the total tooth
width by 1mm in the mandible and 0.5mm in
the maxilla and an arch perimeter
discrepancy of 1.6mm in the mandible and
0.4mm in the maxilla when using the sonic
method.
The sonic digitization was not as reproducible as the
digital caliper and it’s clinical usefulness in evaluting
the space problem of an individual malocclusion
should be interpreted with caution.
EJO 20 (1998) 653-661 space analysis; a comparison between sonic digitization (DigiGarph TM Workstation) and the digital caliper
114. Company Logo
A Quick and Easy Diagnostic Setup Technique
JCO-Online Copyright 2003 - VOLUME 35 : NUMBER 5 : PAGES (328-329) 1998
MELISSA D. WILSON, DDS, MS, PRAMOD K. SINHA, DDS, BDS, MS, and HARI S. PRASAD, BS, MDT
The traditional method of fabricating a diagnostic setup
is to saw through the root areas, separate the teeth by
hand, and affix them in their new positions with wax.
This article presents a simpler technique that shortens
fabrication time and still produces a reliable setup,
without the need for additional trimming.
115. 1. Pour and trim the upper and lower casts as usual.
2. Vacuum-form duplication stents over the casts.
JCO-Online Copyright 2003 - VOLUME 35 : NUMBER 5 : PAGES (328-329) 1998 A Quick and Easy Diagnostic Setup Technique
Procedure
116. 3. Fill the stents with
orthodontic stone to the
level of the gingival
margins.
Remove any excess
stone from the inner
edges of the stents.
JCO-Online Copyright 2003 - VOLUME 35 : NUMBER 5 : PAGES (328-329) 1998 A Quick and Easy Diagnostic Setup Technique
117. 4. Once the stone has set, apply a layer of soap or tinfoil
substitute.
5. Fill the stents to the top with orthodontic stone.
6. After setting, remove the new casts from the stents.
7. Number the teeth in each arch (Fig. 3).
JCO-Online Copyright 2003 - VOLUME 35 : NUMBER 5 : PAGES (328-329) 1998 A Quick and Easy Diagnostic Setup Technique
118. 8. Remove the dental arches from the bases, and break the
individual teeth apart.
9. Using a thin layer of wax, replace any teeth that are to
remain in their original positions.
10. If any teeth need vertical repositioning, carve down the
ridge accordingly. Position the remaining
teeth according to the treatment plan. Add prosthetic teeth if
necessary.
JCO-Online Copyright 2003 - VOLUME 35 : NUMBER 5 : PAGES (328-329) 1998 A Quick and Easy Diagnostic Setup Technique
119. Because no sawing is
required, this technique
greatly reduces the time it
takes to make a diagnostic
setup. If the repositioning
involves only one arch, the
heel of the diagnostic setup
should still line up with that
of the original opposing
base, allowing reliable
interdigitation.
JCO-Online Copyright 2003 - VOLUME 35 : NUMBER 5 : PAGES (328-329) 1998 A Quick and Easy Diagnostic Setup Technique
121. Procedures and use of the occlusogram:-
Many of orthodontists have elected not to get an
occlusogram camera and have used a piece of plastic
over the occlusal surface of the model and made tracings
manually. Some still think it is preferable to use
a.photographic record, since it eliminates the step of
tracing and gives a permanent record.
The occlusograph uses a view camera with a Polaroid back.
By changing the bellows distance, you can make a 1:1
photo. Once the groove is oriented on the stage, we know
that the models are in a centric relation relationship.
Some think the occlusal view is the key to planning and
useful than the lateral view as you can see your width
problems and your asymmetries.
122. Disitizing points
Digitizing the points of the occlusal photograph of the model gives
us 1- Measurements and a diagram of the tooth positions.
2- A printout of tooth size discrepancy.
3-The computer does a setup.
Points are digitized at the mesial and distal contacts and the tips of
the buccal cusps of the lower, and the functional cusps on the
upper(tips of the lingual cusps). The computer draws the teeth.
These are schematic representations of the upper and lower
teeth.
The computer calculates
1- The variations from the mean tooth size. The reason for seeing
this on the screen at this time is to find out if there are major
tooth size differences. This is used if we want to make a
decision on extraction, or to point out a mistake in digitizing.
2- Later, we will actually set up the teeth on the computer to see
how they are going to fit.
123. The computer asks if you would like to move one buccal segment
back in respect to the other,'just to equalize their axial
inclination or their position. It will then calculate where the
center of the arch is — the geometric midline.
Next, to determine where the midline should be on the patient, we
use all our knowledge as an orthodontist. We consider the
facia) midline based on esthetic considerations, anterior apical
base discrepancies, and the geometric midline which we just
established.
Now the computer will first of all draw the original ma (occlusion
on which you see certain control points which the orthodontist
decides. He decides what the width should be. He digitizes
where he wants the lower incisor to be. This is all
individualized. AH the computer does is make it easy to handle.
Now, we have the new arch form constructed. Both the original
and final arches are shown on the screen.
Geometric midline
124. Treatment plot
In case of arch length deficiency (ALD) the
computer asks what we would like to do
about it. Do we want to remove teeth? We
can choose to extract and see the "treated
case" on the screen. If we don't like the
results, we can go back and go through
another treatment plot. We can try one
with different extractions or nonextraction.
A number of different treatment plans can
be tried to arrive at the best possible one.
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125. We decided to take out upper first bicuspids. A double
check of tooth dimensions on the hard copy shows that
the upper bicuspids were over 7 mm in width. Therefore,
this becomes a reasonable solution. We treated the
lower arch on the computer and established the lower
arch form. The computer now fits upper arch to lower.
We have already instructed the computer to give us a set
amount of overjet We used 1 mm for the incisor and for
the cuspid. We could have used 2 mm for the incisor and
2 mm for the cuspid if we wanted more cuspid rise. In
fitting the upper arch to the lower, the computer
calculates the arch length inadequacy based on the two
arches. Once again, the decision about what the clinician
wants in overjet and overbite is left to him.
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Treatment plot
126. The computer tells.us that, in the upper
arch, on the left side of the buccal
segments can come forward 2.7 mm and
on the right side they can go back 1.7 mm.
based on the repositioning of the incisors.
This becomes a severe anchorage
problem. The computer once again asks
you if you have any other solutions to try.
The final upper arch fits the final lower.
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Treatment plot
127. comparing to average tooth sizes
Average tooth size is not the most important
factor, because you can have teeth that
are uniformly much larger than average
and no problem. The comparison between
the standard and the individual gives us a
way of checking our digitization for big
discrepancies. The other way that it is
used is that it let's you know the sizes of
teeth in case you plan to extract teeth or
do some atypical extraction.
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128. Digitizing errors in comparison with other methods of
tooth size measurement
BURSTONE stated that in digitizing, we figure
operator error is between % mm and 1/2 mm.
Most of our devices are accurate to a quarter of
a millimeter. I find it far superior to dividers,
which have a certain amount of give to them.
With a Vernier gauge, it is hard to get exact
mcsiodistal diameters of teeth. Provided axial
inclinations are fairly normal, the use of a
photograph is more accurate than other
methods of measurement; atypical axial
inclinations are compensated for in our system.
129. Summary of the computer procedures for the occlusosram
Orthodontist makes the major decisions in our program.
He starts with a photograph of his models and
determines how far backward or forward he wants the
lower incisor to be. He determines what his cuspid and
first and second molar widths should be. The dental
assistant will then digitize all of the teeth by landmarks
on the teeth. The computer will then determine the arch
length inadequacy per quadrant. The orthodontist will
then decide how he is going to solve the problem —
either by extraction or posterior movement of teeth. The
computer will then report the position of the teeth and
determine where the posterior segments should be at
the end of treatment.
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130. In an extraction case, it will tell us how many millimeters
forward the buccal segments can come in each
quadrant. The computer also makes calculations along
the way that are useful to the orthodontist in arriving at
his decision. It measures the mesiodistal diameters of
the teeth, compares them to standards, sees if there is a
tooth size discrepancy, compares right and left sides for
discrepancy It also gives consideration to the posterior
segments and determines where the correct midline
should be. Finally, the computer will set the teeth with
detailed intercuspation, similar to a wax setup, to see if
there are any tooth size discrepancies. At any stage, the
orthodontist can cycle back and try another solution.
132. CAREV'S ANALYSIS
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Methodology
Determination of arch length The arch
length is measured anterior to the first
permanent molar using a soft brass
wire. The wire is placed touching the
mesial aspect of lower first permanent
molar, then passed along the buccal
cusps of premolars, incisal edges of
the anteriors and finally continued the
same way up to the mesial of the first
molar of the contralateral side. The
brass wire should be passed along the
cingulum of anterior teeth if anteriors
are proclined and along the labial
surface if anteriors are retroclined.
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The mesiodistal width of teeth anterior to the
first molars are measured and summed up as
the Total tooth materia!. The difference
between the arch length and the actual
measured tooth material gives the
discrepancy.
134. Interpretation
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The amount of discrepancy between arch length and
tooth material is calculated.
If the arch length discrepancy is:
• 0 to 2.5 mm-Proximal stripping can be carried out to
reduce the minimal tooth material excess.
• 2.5 to 5 mm-Extraction of 2nd premolar is indicated
• Greater than 5 mm-Extraction of first premolar is
usually required.
