Tooth resorption is a physiological or a pathological process involving the destruction and loss of mineralized tissues of the tooth, and sometimes also alveolar bone. The basic classification of resorption distinguishes two types: internal tooth resorption, when the pathological process starts in the dentine, and external tooth resorption, which has its onset in the cementum continuing towards dentine and the pulp. In the permanent dentition it is always a pathological phenomenon. Teeth diagnosed with resorption require thorough clinical and radiographic diagnostics and appropriate method of treatment. Cone beam computed tomography is extremely useful in diagnosis of root resorption. In the treatment process, non-surgical or surgical (invasive) methods can be applied. To fill in the resorption defects, the application of calcium-silicate cements, which ensure seal and stimulate regeneration processes, seems most beneficial. The aim of the study is to postulate that properly conducted non-surgical treatment of the teeth with diagnosed external inflammatory resorption might be sufficient for healing of even extensive inflammatory lesions, eliminating the necessity of invasive endodontic microsurgery procedures.