[Impacted bilateral first permanent molars induced by the migrated second permanent molars].

It is a relatively common clinical experience to see an impacted permanent tooth. In most cases, the cause is considered to be the existence of a supernumerary tooth or developmental crowding, but occasionally, the impacted tooth may occur with no apparent cause. The tooth most frequently impacted in the dental arch is a maxillary permanent canine or the third permanent molar, but the occurrence of the first permanent molar is an extremely rare situation. The patient, an eight-year, seven-month-old male was referred to the Pediatric Dentistry Clinic at the Higashi-Nippon-Gakuen University, School of Dentistry, for a detailed dental examination of his impacted lower permanent first molars. The oral findings through dental examination revealed that the bilateral upper first permanent molars were erupted, while the lower ones showed no clinical signs of eruption. Radiographic examination revealed that the lower second permanent premolars placed under the distal root of the second deciduous molars, and the first molars, inclined to the mesial position, placed at the under the second premolars bilaterally. There was nothing particular in his medical and dental history during the "teething" period. The authors determined that the cause of this impacted condition for the first molars seemed to be induced by a migration of an unerupted second permanent premolars. After extraction of the second deciduous molars and second permanent premolars, orthodontic therapy was undertaken in an attempt to move the impacted first molars into the arch.(ABSTRACT TRUNCATED AT 250 WORDS)