The article expores currently available ways of differential diagnosis of external and internal resorption in the presence of a related developmental abnormality, dens invaginatus (DI), to the maximum extent possible; whereas DI genuine etiology is still open to debate. In different regions, the DI prevalence varies to a considerable exten t. The nonoccurrences are attributed to flawed diagnosis; therefore, not all DI cases are included in the statistics. Me anwhile, such an invagination may lead to complications developing in the pulp and periapical tissues, and thereby it may significantly impede endodontic treatment. Objective: The current study aims to study the intricacies of the dens invagination (DI) abnormality in routine dental practice. An attempt has been made to better understand the clinical signs of invagination and their impact on complications, and to systematize the criteria for diagnosing this abnomality.