[A clinical study of traumatic injuries to deciduous teeth. (3). The influence on their permanent successors].
To study the influence of traumatic injuries to deciduous teeth on their permanent successors, we investigated 126 traumatized deciduous incisors of 66 children who had visited our clinic regularly after traumatic injuries, and whose permanent successors had erupted. The results are summarized as follows. 1) Some developmental disturbances on permanent successors, such as concerning their eruption, or crowns, roots and pulp, were found in 72 teeth. Among these, influences on crown formation and calcification were most often found, and white discoloration in the enamel was recorded in 55 teeth, yellow discoloration in 4 teeth and hypoplasia in 11 teeth. 2) One successor erupted one and a half years after the eruption of its opposite, and two teeth erupted in torsiversion. Three successors had root angulation, while arrest of root formation was found in one tooth. Pulp canal obliteration appeared in two teeth before their eruption. 3) Developmental disturbances of the crowns tended to be more severe and had a higher ratio when traumatic injuries occurred at a younger age. The range of the ages of the children at the time of injury was limited in cases of hypoplasia and yellow discoloration. 4) According to the diagnoses at the first visit, the severity of periodontal injury and the dislocational directions of deciduous incisors might relate to the disturbances of crown formation and calcification of successors. 5) According to the type of treatment, enamel hypoplasia was observed more frequently in the observation group and the extraction group. Yellow and relatively large white discolorations were found more frequently in the reposition group than in the fixation group. 6) In the endodontic therapy group, only relatively small white discolorations were found, but white discoloration was observed more frequently in the extraction after endodontic therapy group than in the extraction without endodontic therapy group after first visit. 7) White discoloration in the enamel was most often located in the both upper and lower teeth at the incisal third position on the labial surface.