Introduction/Objective Digital 3D modeling is slowly becoming an everyday orthodontic practice, and after two decades of research and development it is a basic element of e-orthodontics. The aim of this study was development and use of geometric entities on 3D digital models for diagnosing, planning and monitoring of orthodontic therapy, by using CAD (computer aided design) systems. Methods Statistical analysis and synthesis of 54 orthodontic parameters (28 in the upper and 26 in the lower jaw), defining three hypotheses and their testing, the application of the t-test. Results All three hypotheses are confirmed, convenience of using geometric entities, higher accuracy of 3D digital models, and more substantial displacement of teeth in the first six months of therapy (Student's t-test). After the first six months, distances in the x-y plane (occlusal plane) were bigger in both the upper and the lower jaw; additionally, the distances in the y-z plane (medial plane) decreased on the left and right side, so we can say that the first phase of therapy had success and that both jaws are wider. At the next four controls, parameters showed slight progress that was not statistically significant. Overall, after 11 months of therapy, there was a considerable improvement in the x-y plane, while changes in distances of clinical crown heights were very small. This could be explained by the fact that, during therapy, by using different arches, upper molars were pushed inside, toward the palate. Analyzing 3D computer models, we could notice that in this plane displacement of the upper left first molar was larger. Conclusion The use of geometric entities for defining orthodontic parameters gives us new possibilities for accurate and reliable analysis of patient's orthodontic condition.