Introduction

Dental study models are essential for implant treatment planning, for fixed and removable prosthesis and for orthodontic diagnosis, planning, and treatment evaluations. Many methods are available for digital model production.

Objective:
To assess the validity and reliability of three-dimensional (3D) virtual or digital models generated from CBCT scanning of stone casts or impressions.

Methodology:
Two techniques were used to obtain 3D virtual model files including scanning of impressions by CBCT machine besides scanning of the corresponding casts by the same CBCT machine (N=36). Six linear measurements (canine to molar, inter-canine, inter-molar and vertical dimensions) were measured in all virtual models and compared with the calliper measurements of the stone model. Additionally, Stereolithography (STL) files from the two techniques were registered with that obtained from a desktop scanner by using a best-fit matching in a 3D modelling software. Mean deviations between the virtual meshes were measured by the software and color maps were checked for qualitative assessment.
Results:
Some linear measures and the 3D deviation analysis revealed statistically significant differences but all were considered clinically accepted.Virtual models created by CBCT scanning of casts exhibited less differencesranging from (0.17/ -0.02 mm), whereas CBCT scan of impressions revealed mean discrepancies with a range (0.16/ -0.04 mm).


Conclusion:
CBCT scanning of the impressions and stone casts provided acceptable results but with decreased surface texture of the 3D mesh. Both techniques can be used in clinical practice providing the use of highly accurate machines.