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The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B5. Beijing 2008 
After the described 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. In order to achieve 
correct spatial placement of sections, each pair of opposite 
dental arches was oriented with respect to a given plane in a 
manner similar to their position in an adjustable articulator - a 
device to which dental arch models can be attached according 
to their position in the scull and which is used in occlusion 
studies and prosthesis construction. 
As a further step, it is possible to carry out tooth preparation on 
plaster casts and to obtain 3D model of prepared teeth for 
treatment planning. The 3D model of prepared teeth is also 
placed on it real position applying the developed technique. 
Later, the 3D model of constructed prostheses for the prepared 
teeth is obtained and combined with the dental arch 3D models. 
3.2 Separate tooth registration procedure 
Prosthetic dentistry is aimed at restoring the structure and the 
function of human dentition. It uses simulation and 
reproduction of natural features of human dentition for 
prosthesis manufacturing. For the purpose of the research some 
individuals with intact chewing teeth is selected. Silicone 
impressions of their dental arches are made for getting plaster 
casts; silicone records of different occlusal positions are made 
for positioning plaster casts; facial bow registrations are 
performed for mounting plaster casts on an articulator. 
After performing tooth preparation on plaster casts restorations 
are designed on them. In order to obtain the required sections, 
precise 3D models of dental arches are obtained using plaster 
casts. Consequently, two opposite 3D dental arch models (upper 
and lower) are oriented in three positions (centric, one right and 
one left lateral) determined by silicone occlusal position 
registrations (Fig 5). Thus it is possible to observe and study 
relations of opposite occlusal surfaces in different positions. 
Figure 7. Separate tooth positioning 
In order to achieve correct spatial placement of sections, each 
pair of opposite dental arches is oriented with respect to a given 
plane in a manner similar to their position in an adjustable 
articulator - a device to which dental arch models can be 
attached according to their position in the skull and which is 
used in occlusion studies and prosthesis construction. Spatial 
orientation of 3D models is carried out with the help of 
reference points on one of the parts of the articulator. As a 
further step, tooth preparation is carried out on plaster casts and 
3D model of prepared teeth is obtained (Fig 7). 
Then the 3D models of the dental arch with those of the 
prepared teeth are matched. As a result the 3D models are 
spatially oriented in a correct manner. Each of these models 
consisted of one upper dental arch 3D model, three lower dental 
arch 3D models (showing three different occlusion positions) 
and 3D models of prepared teeth (typically two or four prepared 
teeth). Prostheses were constructed for the prepared teeth at a 
later stage and their 3D models were obtained and combined 
with the dental arch 3D models. 
3.3 Face - teeth arch 3D models positioning 
The next step needed for visualization and documentation of 
treatment planning and results is to setup teeth arch 3D models 
in proper position relatively patient face 3D model. For this task 
solving a special reference object is required because teeth 
arches of a patient could not be seen enough even when wide 
smiling. 
A dentistry tool for making silicon impression of teeth arches is 
slightly modified for this purpose by adding a special silicon 
reference surface on its front (Figure 8.). This reference surface 
has spatial features for its identifying and matching in different 
3D models. 
/ 
A 
Figure 8. Patient with special reference object for upper teeth 
arch position registration 
For correct position of teeth arch 3D models relatively face 3D 
model patient face 3D model is acquired in two conditions: 
1) normal (smiling) 
2) with the reference object in patient mouth (Figure 8.) 
Then upper teeth arch plaster cast is also scanned in two 
conditions: alone and with special reference object. Then 
positioning procedure includes the following steps: