PURPOSE: The purpose of this study was to evaluate the effect of mesiodens on adjacent permanent anterior teeth according to mesiodens characteristics. METHODS: To evaluate complications associated with mesiodens, according to its characteristics, a total of 107 children were studied who had a chief complaint of mesiodens. The number, morphology, direction of eruption, position of mesiodens, root developmental stage and complications related to adjacent permanent maxillary central incisors (APMCIs) were evaluated by radiographic imaging. RESULTS: The final sample was 107 children and total number of mesiodens was 153. Among these patients, 67 percent showed clinical complications. The primary morphologic type was conical (96.1 percent) and the most common direction of eruption was inverted (56.2 percent). Most mesiodens (80.4 percent) were located on the palatal side of the APMCIs. CONCLUSIONS: The direction of mesiodens and the eruption period of adjacent permanent incisors affected the complication rate. The positional relationship between mesiodens and adjacent permanent central incisors had the strongest influence on both eruption disturbance and displacement of permanent central incisors.