External inflammatory root resorption is a common complication of dental trauma, affecting up to 18 % of patients after luxation injuries of all types [19] and up to 30 % of replanted avulsed teeth. External inflammatory resorption after trauma is a well-known complication after intrusive luxation injuries and replantation of avulsed teeth, progresses quickly, and is radiographically distinguished by cavitation-like areas of low density along the root surface and surrounding alveolar bone.

CBCT provides improved assessment of the presence and type of root resorption, especially in the apical third of the root [20] (Fig. 7.2). Simulated external resorption in 131 cavities using single-slice CT scans showed higher sensitivity and excellent specificity in the detection of resorption in small cavities in the apical 1/3 of extracted human incisors [21]. Laboratory studies using extracted teeth with simulated resorptive lesions [12, 22] suggest that CBCT provides high sensitivity and specificity in the detection of simulated resorptive lesions on mandibular incisors. However, these ex vivo studies do not exactly replicate the clinical situation, where changes in the supporting structures such as the periodontal ligament and surrounding bone may have influenced the result. In addition, the synthetic resorption cavities in the teeth studied were created with round burs that may not have accurately replicated the irregular nature of some resorptive lesions, which may have influenced detection.

The advantages of serial cross-sectional imaging have been well documented in the orthodontic and endodontic literature [23]. Several ex vivo studies in the orthodontic literature have demonstrated the advantages of CBCT in the detection of root resorption in maxillary teeth in close proximity to impacted canines [24]. External apical root resorption in orthodontics is estimated to affect at least one root in 94 % of patients investigated [25].

Diagnosis and management of external cervical resorption (Fig. 7.3) is challenging to diagnose and manage and is most commonly associated with orthodontic treatment, dental trauma, cervical restorations, and/or bleaching [26]. This type of resorption is characterized by a circular lesion that progresses in a coronal and apical direction (Fig. 7.4). The root canal is not invaded in the early phases. External cervical resorption may be distinguished from caries by a “non-sticky” feel upon exploration. A pink area may be noticed by the patient or clinician, a result of vascular granulation tissue visible through the resorbed dentin. Two-dimensional radiographs may not show the full extent of the lesion nor the portal of entry, complicating treatment. CBCT shows the extension of the lesion and assists with the determination of the expected outcome and location of important anatomic structures to facilitate a surgical approach, if indicated. According to Heithersay, orthodontic treatment was potentially related to 24.1 % of external cervical resorption cases studied, with a time to diagnosis of between 1.5 years and 33 years and predilection for maxillary canines, maxillary incisors, and mandibular molars. External cervical resorption was also associated with trauma and bleaching, with 15.1 % and 7.4 % of teeth involved, respectively [26]. Many case reports of multiple idiopathic external cervical resorption have been published, with the number of teeth involved ranging from 5 to 24 per patient. While there was no unique region of the mouth that was affected, 13 of the 18 patients were female [27].