Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Oral (Radiology and Diagnosis)

External root resorption could be found in both primary and deciduous dentition, it is considered as a physiological process when it is found in primary dentition and results in the exfoliation of a deciduous tooth and the eruption of its permanent successor. However, it is considered as a pathological lesion when it is found in the permanent dentition. Many etiological factors were found to cause external root resorption as: mechanical damage caused by sharp injuries, physiological process after tooth replantation, iatrogenic factors as caused by applying too much orthodontic forces to the teeth and the pressure caused by impacted or a nearby pathological lesion. External root resorption can be found in any root third (cervical, middle and/or apical). Several classifications had been suggested, but, the classification according to the stimulatory factors is the most dependable one where it was classified into; pulpal infection root resorption, periodondal infection root resorption, orthodontic pressure root resorption, impacted tooth or tumor pressure root resorption and ankylotic root resorption. Its early diagnosis is mandatory as it could be reversible after the irritant is removed, so called transient resorption, however, it is one of the difficult pathological lesions to diagnose as it usually doesn{u2019}t have any signs or symptoms; and depends mainly on the radiographic imaging. Several studies had been made to determine the best radiographic imaging modality to detect the external root resorption, and it was found that a 3D imaging modality is superior to the 2D imaging modality in detection of this lesion

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