29416650 Study Cast Analysis

7/30/2019 29416650 Study Cast Analysis

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Study Cast Analysis


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Study casts are the essential diagnostic aids.They provide a 3-D view of the maxillary and mandibular dental arches


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What is Study Cast Analysis ?

Involves the study of maxillary and mandibular dental arches

in all the three planes of space

Valuable tool in orthodontic diagnosis and

treatment planning


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Proper alignment of the teeth requires harmony between the

tooth sizes and the space required within the dental arch.

Sometimes the space available is not similar to the space

required for the alignment of the teeth.


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Space available = the length of the arch

Space required = the total of the mesio distal width of teeth

If space available = space required , then the arch is well aligned

If the space available is less than space required , then the arch is

crowded

If the space available is more than space required , then the arch is

spaced

Spaced dentition


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It is thus important for the clinician to determine

prior to the onset of the orthodontic treatmentthe space requirements necessary forfavorable results.

To accomplish this, a space (study cast) analysis

must be done.


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Measurements: 1. ARCH LENGTH = ARCH PERIMETER = ARCH CIRCUMFERENCE

2. MESIO-DISTAL WIDTH OF TEETH

S1

S2 S3

S4

Arch length = S1 +S2 + S3 +S4OR

Length of the brass wire


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3. ARCH WIDTH Inter premolar width

Inter molar width


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Permanent Dentition study cast analysis

1. Careys Analysis / Arch Perimeter Analysis

2. Ponts Analysis

3. Ashley Howes Analysis

4. Bolton Tooth Size Analysis (Ratio)


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This analysis helps to determine the extent of the space discrepancy.

It is performed on the lower cast.Same analysis on the upper cast is called Arch Perimeter Analysis.

CAREYS ANALYSIS

Space analysis requires a

comparison between the amountofspace availablefor the

alignment of the teeth

and the amount ofspace required

to align them properly


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STEP 1: Calculation of Space Available

This is accomplished by measuring arch

perimeter from the mesial of one first molar to the other,

over the contact points of posterior teeth and incisal edge of

anteriors.

There are two basic ways to accomplish this

manually:(1) by dividing the dental arch into segments

that can be measured as straight line

approximations of the arch or

(2) by contouring a piece of wire to the line of

occlusion and then straightening it out for

measurement.

S1

S2 S3

S4


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STEP 2: calculate the amount of space required

The mesio-distal width of the teeth

anterior to the first molars (secondpremolar to second premolar) is

measured and summed up.

If the sum of the widths of the permanent teeth is greater than the amount of space

available, there is an arch perimeter space deficiency and crowding would occur. I

f available space is larger than the space required (excess space), gaps between some teeth

would be expected.

SPACE REQUIRED GREATER THEN SPACE AVAILABLE = CROWDING (in mm),

negative discrepancy

SPACE REQUIRED LESSER THEN SPACE AVAILABLE = SPACING (in mm)


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The type of discrepancy is noted, i.e., whether positive (spacing)or negative (crowding).

Any of the following methods will have to be adopted

if there is a negative discrepancy between arch length

and tooth material.

a) Proximal stripping...discrepancy up to 2.5mm

b) Extraction of second premolars.... discrepancy between

2.5mm & 5 mm

c) Extraction of first premolars - discrepancy more than 5 mm.


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Example:


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BOLTONS ANALYSIS

There exists a ratio between the mesio-distalwidths ofmaxillary

and mandibular teeth

Malocclusions occur as a result of

abnormalities in tooth size

The Boltons analysis helps in determining disproportion in size

Between maxillary and mandibular teeth.


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Bolton Tooth Size Analysis

(Ratio)

Overall ratio:

Add the mesio-distal width of themaxillary incisors, canines, premolars

and the first permanent molars =

maxillary tooth size.Add the mesio-distal widths of the

mandibular incisors, canines,

premolars

and the first permanent molars =

mandibular tooth size.

Overall ratio= Mandibular 12 X100

Maxillary 12

The mean value is 91.3%


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If the calculated overall ratio is greater than the mean value (91.3 %)

It indicates that the mandibular tooth size is in excess

To find the mandibular excess, subtract the correct mandibular tooth size (X) from

the calculated mandibular tooth size

Where X = sum of maxillary 12 X 91.3

100

i.e. Sum of mandibular 12 - sum of maxillary 12 X 91.3

100

If the calculated overall ratio is smaller than the mean value than it implies

that the maxillary tooth size is in excess compared to the mandibular tooth

size.

To find the maxillary excess, subtract the correct maxillary tooth size (X) fromthe calculated maxillary tooth size.

where X = Mandibular tooth size X 100

91.3


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Anterior ratio: The mesio-distal width of the maxillary and mandibularincisors and canines, are taken into account.The calculations are done in the same manner as

in the overall ratio. The mean value for the anterior ratio is 77.2%

Inference :If the discrepancy value exceeds 2mm (overall or anterior)

suitable measures should be adopted to correct the discrepancy.

PONTS ANALYSIS


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Method:

a. Measure the mesio-distal width of the upper central and lateral incisors. .,

b. sum of the above = SI

c. Measure the width of the arch in the region of the first premolari.e., the width from the distal pit of the first premolar to the same point on the otherside

d. Measure the width of the arch in the molar region

i.e., the width from the mesial pit of the first permanent molar of one side to the other.

e. The arch width is calculated, for a given mesio-distal width of the

upper incisors, in the premolar and molar region

using the' formulaSI X 100/80and SI X 100/64 for the premolar and molar regions respectively.

f. The measured and calculated widths are compared.

Conclusion:

If the measured arch width is less than calculated width then the arch is

narrow and needs expansion.

PONTS ANALYSIS

Determines whether the dental arch

is narrow or normal


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Mixed Dentition space Analysis

To evaluate the amount of space available in the arch for the

erupting permanent canines and premolars

Mixed Dentition


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MOYERS MIXED DENTITION ANALYSIS

In this analysis size of the cuspids and premolars are

derived from the knowledge of the size of permanent teeth

already erupted in the mouth.

The lower incisors are measured to predict the size of upper

as well as lower posterior teeth.

The Moyers analysis predicts the combined mesio-distal

width of 3,4, and 5 based on the Sum of the widths of the

four lower permanent incisors


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Tanaka and Johnston prediction values


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Measurement from Radiograph


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HIXON AND OLDFATHER PREDICTION

This method of prediction uses both theradiographs and prediction tables. 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 casts and the size of

unerupted premolars measured from the

periapical films to predict the size of unerupted

canines.


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From the prediction table, the predicted size

of the unerupted canines and premolars are

found against the measured value. This

method is restricted to the mandible.


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measured value Estimated tooth

size

23 18.4

24 19.0

25 19.7

26 20.327 21.0

28 21.6

29 22.330 22.9


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Graph showing relationship between size of lower incisors measured

from cast plus lower first and

second premolars measured from radiographs (x-axis) and size of

canine plus premolars (y-axis)

Digital Cast Analysis


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Digital Cast Analysis

Documents

29416650 Study Cast Analysis