tion for 
[gorithm 
  
ed using 
escribed 
es, The 
nsist of 
arch 3D 
yaz V., 
d lower 
canning 
aptured. 
per and 
  
rch 3D 
The first step is to install 3D models of upper and lower teeth 
arches in a given position according their location and 
orientation in a mouth. For this purpose plaster models are 
installed in given posture using a dental articulator or silicon 
mould for setup (Fig. 4). Dental articulator is used for 
registering central (normal) occlusion. Silicon mould is made by 
dentist in a mouth, jaws being in given position according left 
or right side occlusion. 
The first developed technique for occlusion registration used a 
set of reference point on teeth observing by stereo system and 
virtual teeth arches were installed in occlusion position 
according to calculated 3D coordinates of this set of reference 
points. The new technique based on front teeth surface 
registration gives better accuracy and is chosen as general 
method for occlusion registration. 
After the virtual setup procedure a dentist has teeth arches 3D 
models installed in a position according given occlusion, so he 
can perform all necessary investigations of the occlusion which 
he needs. A dentist can observe and study relations of opposite 
occlusion surfaces in different positions. 
4. VIRTUAL TEETH SET UP 
4.1 3D model segmentation 
For planning orthodontic treatment and individual wire design 
teeth arch 3D model is segmented into separate teeth and gum 
3D models (Fig. 5). 
  
Figure 5. Results of teeth arch 3D model segmentation 
The segmentation process is performed in semi-automatic mode 
using combined  curvature-watershed ^ algorithm. After 
segmentation teeth 3D models are transformed to watertight 
form. This form is needed for solving the collision detection 
problem during teeth shifting planning to avoid producing 
wrong-directed forces. 
4.0 Positioning teeth 3D models in a required (correct) 
position 
Segmentation allows calculating a set of tooth dimensions 
required for determining correct teeth position. Usually for 
calculating the perfect teeth arch curve mesio-distal dimensions 
of several teeth are used. 
  
567 
Figure 6. Perfect teeth arch shape calculation 
Different method for determining perfect teeth arch curve could 
be applied in developed system. Figure 6. demonstrates the 
result of Hawley-Herber-Herbst curve determination based 
mesio-distal dimensions of three frontal teeth. 
After perfect teeth arch shape determination virtual perfect teeth 
arch is generated so as all teeth would be in a correct position. 
Now brackets slots correspond to individual wire which is to 
move teeth into perfect position. 
5. INDIVIDUAL WIRE DISIGN 
5.1 Determining slot position for every bracket 
The next task is to find spatial position of every slot and to 
design individual wire. Image-based technique for this problem 
is developed. It uses special slot probes with coded targets 
which allow finding with high accuracy the position and 
orientation of every slot in given coordinate system. 
  
  
Figure 7. Image-based slot position determination 
Slot position is estimated in automated mode.