[Safe zones of the maxillary posterior area for mini-implant insertion in adolescents with skeletal Class II malocclusion].

PURPOSE: The purpose of this study was to measure the interradicular spaces between the maxillary second premolar and first molar in adolescents with skeletal Class Ⅱ malocclusion, so as to obtain scientific knowledge for placing mini-implants. METHODS： Forty four cone-beam computed tomography(CBCT) images were selected, which consisted of 23 males and 21 females (average age, 14.07 years) with skeletal Class II malocclusion. CBCT was used to measure the closest interradicular distance and the shortest distance from cortical bone surface to the narrowest interradicular space apically at 1-mm intervals in 9 axial images from the cementoenamel junction(CEJ). SPSS 20.0 software package was used for statistical analysis.

RESULTS

There was no significant difference in the closest interradicular distance and the shortest distance from cortical bone surface to the narrowest interradicular space between the left and right side (P>0.05), and no significant difference was found between males and females (P>0.05); The shortest distance from cortical bone surface to the narrowest interradicular space of the left apical area had positive correlation with SNA angle; The closest interradicular distance became wider toward the apical area，and the average distance of the shortest distance from cortical bone surface to the narrowest interradicular space was over 5mm in all sections.

CONCLUSIONS

The distribution of interradicular spaces between the maxillary second premolar and first molar of adolescents with skeletal Class II malocclusion is learned using CBCT. These data might provide a reference for placing mini-implants.