Study models /certified fixed orthodontic courses by Indian dental academy

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

Orthodontic

study models are
accurate plaster reproductions of
the teeth and their surrounding soft
tissues.
They provide three dimentional
view of the dentition.


Requisites of study model
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Should accurately reproduce the teeth and
soft tissues without any distortion.
Should be trimmed symmetrical on either
side .
Posterior surface should be trimmed ,such
that when placed on their back, they should
reproduce the occlusion .
Should reproduce alveolar process as much
as possible.

Parts of a study model
 Anatomic

portion:- It is the actual
impression of dental arches and surrounding
soft tissue structures.

 Artistic

portion:- plaster base that supports
the anatomical portion.


Steps in construction of study models
1.
2.
3.
4.
5.

Impression making.
Disinfection of the impression.
Casting the impression.
Basing and trimming of the cast.
Finishing and polishing of study models.


1.Impression making
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Should record hard and soft tissues completely.
Should extend to limits of the sulcus.
Maxillary impression should not extend to the soft
palate.
Patient should be asked to rinse the mouth before and
after impression.
Use high flange orthodontic trays and it should include
last erupted molars and 3mm distal to it.
Irreversible hydrocollids are widely used for
impression making.(alginate)

2. Impression disinfection
 Impressions

rinsed thoroughly in water.
 Disinfection is done by soaking in a 2%
gluteraldehyde(Biocide) or ethyle alcohal or
isopropyle alcohol.

 Impressions

are again rinsed in water.

3. Casting the impression
 Casted

using orthodontic stone.

 eliminate

air bubbles


4. Basing and trimming of the cast

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


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Fill the area occupied by tongue in mandibular
impression with alginate.
The stone is first poured in to tooth portion of the
impression.
Next stone is added to complete anatomical
portion of impression.
Remaining stone poured in to base former and the
poured impression tray is turned upside down and
pushed in to the stone in base former.
Impression trays removed from poured stone after
it is hardened.

Study cast analysis:- Gnathostatic model
by SIMON, 1926

 These

plaster models are oriented to the midpalatal
raphe, tuberosity plane and the occlusal plane for
study cast analysis .these model analysis helps in a
three dimensional assessment of the maxillary and
mandibular dental arches and there occlusal
relationships.
 The upper surface of the maxillary study model
corresponds to frankfurt horizontal plane.

According to ABO (1990)
Frontal view of study model
13mm



Base of maxillary cast
trimmed parallel to
frankfort horizontal
plane
13mm


Lateral view of study model

7.07.5cm

3.54.0cm

3.54.0cm



The posterior surface
of max & mandibular
cast should be
trimmed to flush
terminal plane.


Maxillary occlusal view of
study model
5-6mm
25º

5mm

70º

90º

13mm


90º

5mm

Mandibular occlusal view of study
model
5-6mm

5-6mm

13mm

65º


90º

5. Finishing and polishing
 Artistic

portion of study model should be
polished using fine grained sand paper.
 Care should be taken not to round off the
edges of model.
 Final polishing done by placing in soap
solution , than dried followed by buffing to
acquire a smooth and shiny surface.


Study models are used for
 To calculate total space analysis.
 To assess and record the dental anatomy.
 To assess and record the intercuspation.
 To assess and record arch form.
 To assess and record curves of occlusion.
 To evaluate occlusion, with aid of articulator.
 To measure progress during treatment.
 To detect abnormalities ( distorted arch form)
 To provide a record before, immediately after,
and several years following treatment for the
purpose of studying treatment procedures.

Digitalizing study models using OrthoCAD

 OrthoCAD

- It is a digital study model capture, assessment
and storage system.
 It provides a 3D record of the original malocclusion, any
stages during treatment and the outcome of the treatment.

Digital study models
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Advantages
Virtual casts can be kept in
digital format & hence
eliminating storage problems.
Immediate data transmission.
Measurements on digital casts is
easy, accurate & automatic.
Digital images can be made
bigger and hence localizing
anatomic points easily.
Digital study casts can be used
for patient motivation.
Stores original malocclusion in
3D formate.

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Disadvantages
If the plaster dental casts
are poor, than the obtained
digitalized images will be
altered during
digitization .
Dental images in mixed
dentition are difficult to
recognize and measure.
Digitalizing dental casts is
a laborious process that
has always to be made
under the same conditions.


Study models /certified fixed orthodontic courses by Indian dental academy

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