Automated three-dimensional quantification of external root resorption following combined orthodontic-orthognathic surgical treatment. A validation study

Three-dimensional (3D) quantitative assessment of external root resorption (ERR) following combined orthodontic-orthognathic surgical treatment is vital for ensuring an optimal long-term tooth prognosis. In this era, lack of evidence exists applying automated 3D approaches for assessing ERR. Therefore, this study aimed to validate a protocol for 3D quantification of ERR on cone-beam computed tomography (CBCT) images following combined orthodontic-orthognathic surgical treatment.Twenty patients who underwent combined orthodontic-orthognathic surgical treatment were recruited. Each patient had CBCT scans acquired with NewTom VGi evo (NewTom) at three time-points i.e., 4-weeks prior to surgery (T0), 1-week (T1) and 1-year after surgery (T2). Patients were divided into two groups, group A (surgical Le Fort I osteotomy group: 10 patients) and group B (orthodontic group without maxillary surgical intervention: 10 patients). Root resorption was assessed by measuring length and volumetric changes of maxillary premolar to premolar teeth (central and lateral incisors, canines, 1st and 2nd premolars= 10 teeth) at T0-T1 and T0-T2 time intervals in both groups. The protocol consisted of convolutional neural network based segmentation followed by surface-based superimposition and automated 3D analysis.The intra-observer intra-class correlation coefficient (ICC) was found to be excellent (1.0) with an average error of 0 mm and 0 mm3 for assessing root length and volume, respectively. The entire protocol took 56.8 ± 7 s for quantifying ERR. Both group of patients showed negligible changes in length and volumetric ratio at T0-T1 time-interval. Furthermore, group A had lower ERR ratio with decreased root volume and length compared to group B at T0-T2 time-interval.The proposed protocol was found to be time efficient, accurate and reliable for 3D quantification of ERR on CBCT images. It could act as a viable automated option for assessing ERR.The automated protocol could provide a time efficient method to allow a reliable and accurate 3D follow up root resorption after orthognathic and orthodontic treatment procedures. These new insights could allow clinicians to implement strategies for minimizing the risk of root resorption and to further enhance treatment predictability.