JOURNAL OF OSAKA DENTAL UNIVERSITY

Vol. 42 No. 1      APRIL - 2008

ISSN: 0475-2058      UBIC: 172

SUMMARY

When treating skeletal mandibular prognathism in pediatric patients in the period of active growth, appropriate consideration must be given to the amount and direction of development. However, because the exact prediction of structural changes in a growing patient is difficult, no standardized treatment modality is now available. The subjects of this study were children with comparatively prognathic mandibles chosen among schoolchildren who had not received orthodontic treatment. The subjects were further subdivided into two groups according to the magnitude of the anteroposterior discrepancy between the maxilla and mandible. Longitudinal observation of changes in the occlusal plane were made and the two groups were compared. Lateral cephalograms of 60 boys and 60 girls who were in Hellman's developmental stages IIC through IIIC and who had never received orthodontic treatment were studied. Seventeen children of each gender who showed skeletal mandibular prognathism with an ANB angle of 5.5 degrees or more were chosen as subjects for this study. Among these subjects, one boy and 4 girls, who had negative ANB angles were chosen as subjects for Group 2. Angular and linear measurements were performed on all subjects for longitudinal analysis of the degree of change. Alveolar changes were also monitored in the group with negative ANB angles. Over four years the mean of the angle formed between the occlusal and mandibular planes, decreased 4.9 degrees in the boys in Group 1, increased 0.9 degrees in the girls in Group 1, and increased 2.6 degrees in Group 2. These results show the diversity of development and the changes in the occlusal plane among children with skeletal mandibular prognathism, and indicate the importance of longitudinal monitoring of these changes and consideration of the maxillary relationship compensation mechanism of the occlusal plane when treating children with skeletal mandibular prognathism.(J Osaka Dent Univ 2008; 42: 57-62) Key words: Longitudinal study; Maxillary protrusion; Occlusal plane.

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