A Clinical Study of Eruption Disturbance of the Mandibular Second Premolar by the Ectopic Position of the Tooth Germ

TAKAGI Junichiro, SANO Tomiko, TAGUCHI Yo, MITOMI Tomoe

doi:10.11411/jspd.47.3_433

The aims of this retrospective study were to examine the eruption disturbances of the mandibular second premolar caused by abnormal inclination of the tooth germs and to discuss and demonstrate the recommended treatment for these cases.The subjects comprised of 11 patients (eight girls and three boys) in whom the eruption of 15 mandibular second premolars was disturbed by aberrant direction of the tooth germs. The patients were treated at the Pediatric Dental Clinic of Niigata University Medical and Dental Hospital during 28years from September 1979 to January 2008. The ages of the patients at the time of diagnosis ranged from 8 years exactly to 13 years and 11 months.The eruption disturbance occurred unilaterally in seven cases (five on the right side and two on the left) and bilaterally in four cases. In 14 of 15 affected premolars, the tooth germs exhibited distal inclinations. A strong correlation between the degree of distal inclination and the delay in formation of the tooth germ was observed (correlation coefficient : R＞0.70) ; the more significant the delay in formation of the tooth germ, the higher the degree of distal inclination.In unilateral cases, the tilting degree was very high, and the formation of the tooth germ was significantly delayed. In bilateral cases, however, both the tilting degree and delay in formation were not severe, and were almost the same on both sides. A comparison between the unilateral group and the bilateral one revealed that the degree of distal inclination was considerably higher in the unilateral group (P＜0.01).In the cases of 14 teeth among 10 patients (all but one unilateral case, in which the patient was very young), the primary second molars were removed soon after diagnosis. The cases that had serious tilting, however, showed only slight improvement of the aberrant tilting even after their predecessors were extracted early, and additional complex treatments such as bone fenestration or traction of the affected tooth were required at the developing stage of initiation or one-fourth of the tooth root formation.If a predecessor is extracted at an early stage of tooth germ formation, long-term space maintenance is required. It was concluded that in cases with a markedly severe distal inclination, eruption disturbance of the mandibular second premolar should be treated after the root formation of its tooth germ is initiated.

A Clinical Study of Eruption Disturbance of the Mandibular Second Premolar by the Ectopic Position of the Tooth Germ

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