Optical modeling of extra oral defects/ dentistry jobs

OPTICAL MODELING
OF EXTRA ORAL
DEFECTS.
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Introduction.
 The combination of medical imaging and
rapid prototyping is a fast expanding field with
a large application potential in medicine and
related fields.
 Typical applications include the making of 3-
dimentional copies of anatomical structures,
the production of individually designed
prosthesis models and the replication of
anatomical objects for educational purposes.

 This presentation highlights about recent
imaging technology and its application in the
field of maxillofacial prosthesis.

Steps in the fabrication of
Maxillo facial prosthesis.
 1) Impression making.
 2) Preparing a physical model
 3) Fabricating a prosthesis pattern.
 4) Final prosthesis.

conventional impression materials such as
Silicones
-Irreversible hydrocolloid
have been used in the fabrication of Maxillo
facial prosthesis.

Conventional Impression
Procedure.

Disadvantages of using the
impression materials
 -Discomfort to the patient.
 -Testing the ability of the clinician.
 -Structural variability of the material leads
to inaccuracies of the fitting of the prosthesis.

 The next generation CT & MRI over come the
difficulties encountered while using the
impression materials.

 CT & MRI scan the defective area & a CAD
model of the defective area is reproduced,
from which a CAD model of the prosthesis
pattern is designed & we get the prosthesis
pattern by a procedure known as rapid
prototyping.

CT SCAN
 Computed Tomography is based on the x-ray
principal:
 x-rays pass through the body they are
absorbed or attenuated (weakened) at
differing levels creating a matrix or profile of
x-ray beams of different strength.
 This x-ray profile is registered on film, thus
creating an image.
 In the case of CT, the film is replaced by a
detector which measures the x-ray profile.

 But the only disadvantage is, the patient is
exposed to radiation

 This disadvantage is overcome by optical 3-
dimentional scanner, which uses optical light
as the source.

 The optical 3-dimentional scanner is a newer
device used to scan the facial defects and
reproduce a CAD model which is used in the
fabrication of Maxillo facial prosthesis.

 It is a mobile, multiview 3-D measuring
system based on self-calibrating fringe
projection technology
 It facilitates the fully automatic recording of
the body part from various direction in one
measuring process
 The maximum field diameter of the system is
650 mm. Therefore, the complete human
face can be recorded in a single operation.

 The face is illuminated by two grating
sequences (grey code combined with four,
90-degree phase-shifted sinusoidal
intensities).

 The observing cameras capture these fringe
pictures simultaneously, resulting in at least 4
phase values for each pixel of the camera.
 Using these phase values, the 3-D
coordinates are calculated.
 In the “kolibri-mobile” system, the object is
illuminated from different directions by means
of a network of fixed mirror.(M1, M2, M3, M4,
M5)
 The switching of the projection direction is
done by the rotating central mirror M1.

 Optimum measurements of an extraoral
defect involves 4 cameras and 5 projection
directions.
 Using this technique, the whole body view is
obtained automatically without any additional
software manipulations.

 The duration time of recording up to the 3-D
point cloud is approximately 20 seconds.
 The measuring accuracy as by the
manufacturer to be less than 100um.

 The body part is exposed to structural light
and is recorded optically.
 The data is transferred and saved as an arg-
file. These data is changed into ASC2 format
on the computer.
 Process the data with software (SURFACER,
version 10.5).
 And a CAD model is generated.

RAPID PROTOTYPING
 The generated CAD model is converted into
a physical model by means of a rapid
prototyping procedure using a 3-D model
printer.

 3-D model printer used
for rapid prototyping to
obtain the physical
model

Uses of physical model
 The pattern of the prosthesis is designed
digitally and the accurate physical model is
obtained

Optical modeling of extra oral defects/ dentistry jobs

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