Root resorption patterns of primary mandibular molars and location of the premolar successors: a radiographic evaluation.

PURPOSE: The purpose of this study was to investigate root resorption patterns of primary mandibular molars and to describe the premolar successors' location throughout the resorption. METHODS: A total of 271 radiographs of primary mandibular molars (56 first molars and 171 second molars) of 187 5- to 12-year-old patients were reviewed, and the patterns of root resorption and the premolars' location were evaluated. RESULTS: In the primary first molar, approximately 55 percent of the root resorption occurred in the distal root, and 41 percent of the root resorption was symmetrical. In the primary second molar, approximately 56 percent of the root resorption was symmetrical, and 36 percent was in the distal root. More mesial root resorption (~71 percent) occurred when the second premolar was mesial. CONCLUSIONS: Primary mandibular first molars begin to resorb at seven years old. The premolars' location between the primary roots is associated with root resorption. Distal root resorption should be expected when caries is present in the distal aspect of a primary second molar.