External root resorption in mandibular second molars associated with mesial, impacted third molars on CBCT images

Objectives: The study aimed to investigate the condition of the external root resorption (ERR) of the distal surface of the root of the second molars when the third molar are impacted, mesial on CBCT images and the relationship between the ERR and the morphological characteristics of third molars Methods: A descriptive cross-sectional study was performed on a sample consisting of 215 CBCT images of the third molars impacted of 145 patients who visited and treated at the Department of Odonto-Stomatology, University of Medicine and Pharmacy. Ho Chi Minh City from March 2016 to June 2022. On the CBCT image, the morphological characteristics of third molars were examined, including: mesial angulations, vertical and horizontal positions, impaction depth, degree of root formation, contact position between second and third molars. ERR of the distal surface of the root of the second molars assessed according to the Ericson and Kurol criteria. Results: The rate of ERR on the distal surface of the second molar was 21.39%, in which the cervical was the most frequent position, followed by the middle of the root and finally the apex; most of the cases were slight resorptions. There was no statistically significant difference between the rate, location and degree of ERR by age and sex. There was no statistically significant relationship between the rate of ERR and the morphological characteristics of third molars except the vertical position of third molars. Conclusion: The second RCL root resorption related to impacted third molars is not uncommon and can be accurately determined by CBCT.