3D CBCT assessment of root resorption: EARR during orthodontic treatment

Objectives: The majority of the knowledge regarding external apical root resorption (EARR) in orthodontic patients is built upon assessment made with 2D radiographs. Each 2D radiographic technique has significant inaccuracy in assessing EARR that have been previously described in the literature. CBCT eliminates much of the inaccuracy and magnification problems of conventional 2D radiographic techniques in assessing EARR. We aimed to assess EARR resulting from orthodontic treatment as it related to specific alveolar bone characteristics, incisor movements, as well as in different ethnic and treatment groups. Methods: CBCT volumes were taken on patients initially (T1) and at 1 to 2 years into treatment (T2). 49 subjects were included in the study. EARR was assessed by subtracting the total tooth length at T1 from the total tooth length at T2. Results: Bone thickness change, palatal distance change, horizontal incisal change and horizontal and vertical apical change were directly correlated with root resorption. Class II upper bicuspid extraction patients had higher root resorption than other classes and extraction patterns. Maxillary incisor intrusion, lingualization of crown associated with controlled tipping, and lingualization of root apex closer to the palatal cortex are found to be associated with higher EARR. Conclusions: Our findings indicate that incisor position and direction of movement as well as other alveolar bone characteristics are correlated with EARR in patients undergoing orthodontic treatment. Our findings demonstrate that CBCT can create an improved standard of care by offering a more accurate method for clinicians to diagnose, monitor, and study root resorption. Further investigation will be essential to build an EARR evidence base that utilizes CBCT to eliminate the inaccuracy in measurement created by traditional radiographic techniques.