Incidence and relationship of an additional root in the mandibular first permanent molar and primary molars

ObjectivesThe mandibular first permanent and primary molars occasionally have an additional root located distolingually. This study aimed to determine the incidences of an additional root in these molars and their relationship.Study designThis study involved 4050 children for whom periapical radiographs of the mandibular molar area were available. The incidence of an additional root for each molar was calculated and the pattern of concurrent additional roots in different molars was also investigated.ResultsAdditional roots were present in 33.1%, 27.8%, and 9.7% of the first permanent, second primary, and first primary molars, respectively. When an additional root was present in a primary molar, the probability of the posterior adjacent molar also having an additional root was greater than 94.3%.ConclusionThe presence of an additional root in a primary molar can be used to predict the presence of an additional root in molars posterior to it.