Computer vision and image processing for dental products

Discussion on Computer
Vision and Image Processing:
Applying data mining in
aesthetic dentistry
Boyan Yankov, PhD

About me
Web developer
Co-founder of Web Motion
Co-founder of VisagiSMile
Actively working on innovative
dental software during the last 2
years
PhD in Informatics, Technology
Entrepreneurship

VisagiSMile - our first dental product
2000+ dentists
4000+ clinical cases

The Visagism Concept - Facial Perception
and Teeth Structure
Do you believe these designs
represent the following effects? YES /
NO / MAYBE

The Visagism Concept - Facial Type
Example:
Patients who have
rectangular faces, formed
by well-defined angles and
vertical and horizontal lines,
have a visual expression of
strength and power, are
generally related to the
strong facial type.
Dynamic / Strong

The Visagism Concept - Facial Type
Facial shapes
Strong
Dynamic
Delicate
Calm
The facial type depends on
the facial shapes, which are
defined with a facial map. Delicate / Dynamic

The Visagism Concept - Personality
Hippocrates, 460-370 BC Dr. Susan Dellinger’s test and Eysenk’s personality
questionnaires
StrongDynamic Calm Delicate

The Visagism Concept
The dental visagism theory relates:
Facial type
and
personality
Teeth
structure

Problem: Classifying the Facial Type
A skilled dental technician can subjectively determine the
facial type.
How to automate this process with a high accuracy?

Classifying the Facial Type - Data Collection
A dental visagism
professional has classified
the types of 91 faces
manually.
And has selected the
corresponding facial
shapes.

Software tool for manual facial shape selection

Automated facial shape selection
1. Facial image is uploaded by the user
2. API call to Betaface is made (with JavaScript)
3. Betaface identifies the Face - provides the positions of
the landmark points
4. The face is calibrated by using the bipupilar line (with
JavaScript)
5. The facial map is calculated (with Javascript)
6. ...

Classifying the Facial Type - by Geometrical
Approximation
The shapes of different facial types look the same until
overlapped.

Classifying the Facial Type - by Geometrical
Approximation
Which shape does the facial
contour fit best
(geometrically)?
Disadvantages:
Do all points matter?
Are all points equally
important?
56% successful classifications
(initial algorithm)

Classifying the Facial Type - by Applying
Machine Learning

Classifying the Facial Type - IBM SPSS
Modeler Testing Setup

Modeler Results

Modeler Results
C5.1 Classification tree model - top
fragment:

Classifying the Facial Type - Weka Results
=== Run information ===
Scheme:weka.classifiers.functions.Logistic -R 1.0E-8 -M -1
Correctly Classified Instances 46 49.4624 %
Incorrectly Classified Instances 47 50.5376 %
Kappa statistic 0.3066
Mean absolute error 0.2874
Root mean squared error 0.4376
Relative absolute error 78.6179 %
Root relative squared error 102.3622 %
Total Number of Instances 93

Product Validation and Clinical Cases
BEFORE
PORCELAIN VENEERS
DESIGN
AFTER

Problem: From 2D projection to 3D models
FROM
THIS...

Problem: From 2D projection to 3D models
...TO
THIS

From 2D projection to 3D models
● 60 cases
● All pictures and measurements taken according to
clinical protocol
● Analysis of upper teeth:
○ Central incisors (11, 21)
○ Lateral incisors (12, 22)
○ Canines (13, 23)
● Goal: Width in projection (photo) to width of 3D scan
● Goal: Height in projection (photo) to height of 3D scan

From 2D projection to 3D models

From 2D projection to 3D models -
conclusions
Central incisors
● Height can be determined from
the model. (R Square = 0,648)
● Width can be determined from
the model, but less accurately (R
Square = 0,464)
Lateral incisors
● Width can be determined from
the model, but less accurately (R
Square = 0,294)
Canines
● Width can not be accurately
determined from the model (R
Square = 0,054)
Best R square values for all teeth
types have been calculated for the
quadratic model,
y = a + b1*x + b2*x^2

From 2D projection to 3D models - Software
● Chooses tooth shape according
to the tooth type and to the
personalized smile design
● Calculates the width and height
of the tooth in 3D from the
width and height in projection
● Resizes the 3D model by using
a custom 3D library
● Visualizes the tooth with
controls for zoom and rotation
● Exports the 3D model in STL
format

REBEL.DENTAL - Coming soon
1. Provides seamless and inexpensive digital
smile design
2. Produces a realistic 3D teeth mock-up - ready
for 3D printing
3. Works with local digital labs
4. Fully automates the digital smile design
process

Product Validation and Clinical Cases - Design

Product Validation and Clinical Cases - Intraoral
scan

Product Validation and Clinical Cases - Mock up

Product Validation and Clinical Cases
BEFORE TREATMENT AFTER TREATMENT

Product Validation and Clinical Cases - Another
Case
AFTER TREATMENT

Free trial
Register a account at visagismile.com
Rebel.dental is coming soon!

Thank you for your attention!
I will be happy to answer any questions you may have.
Contacts:
Boyan Yankov
boyan@webmotion.bg
www.webmotion.bg

Computer vision and image processing for dental products

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