Three-dimensional prediction of roots position through cone-beam computed tomography scans-digital model superimposition: A novel method.

OBJECTIVES: To introduce a new, fast, reliable, and free from software-related bias method to predict three-dimensionally the root position and angulation during and after orthodontic treatment. The final goal is to keep to a minimum the use of ionizing radiation by eliminating the necessity of multiple radiation exposure for checking root alignment.

SETTING AND SAMPLE POPULATION: Pre- and post-treatment digital models and cone-beam computed tomographic (CBCT) scans from a patient were retrieved.

MATERIAL AND METHODS: The post-treatment digital model (post-model) was set as the reference; pre- and post-treatment CBCT scans were pre-aligned to the post-model with a point set registration; iterative closest point algorithm was then employed for final adjustments. The accuracy of the proposed method was assessed by comparing the average distance between the expected root position setup with the true position of the roots, as from the post-treatment CBCT.

RESULTS: After crown superimposition, 3D colour maps showed that the accuracy of the root prediction was below 0.1 mm.

CONCLUSION: The proposed digital workflow allows to predict in an accurate and truly three-dimensional way the final position of roots, when an initial CBCT is available, without the need of an extra X-ray examination for the patient at the end of treatment. The limitation of the exposure to mid- and post-treatment X-rays is in accordance with the ALARA (As Low As Reasonably Achievable) principle and it is even more relevant in growing patients.