The Study Of Safe Zones Of The Maxillary Posterior Area For Mini-implant Insertion In Adolescents With Skeletal Class Ⅱ Malocclusion By Cone Beam Computed Tomography

PURPOSEThe purpose of this study was to measure the interradicular spaces between the maxillary second premolar and first molar of adolescents with skeletal Class II malocclusion so as to obtain scientific knowledge for conducting mini-implants.METHODS44 Cone-beam computed tomography(CBCT)images were selected in our Hospital,which consisted of 23 males and 21 females(12-16)years,average age,14.07 years with skeletal class II malocclusion.CBCT was used to measure the closest interradicular distances and the shortest distances from cortical bone surface to the narrowest interradicular space apically in 1-mm intervals in 9 axial images from the cemento-enamel junction(CEJ).SPSS 20.0 software was used for statistical analysis of the measurement data,and the Pearson correlation analysis was carried out between the measurement data and SNA angle,SNB angle and ANB angle.RESULTS1.There was no significant difference in the closest interradicular distances between the left and right side(P>0.05),and no significant difference was found between males and females(P>0.05).There were significant differences between the 9 sections of the measurement value(P<0.05).The closest interradicular distances became wider toward the apical area.The closest interradicular distances had no correlation with SNA angle,SNB angle and ANB angle.2.There was no significant difference in the shortest distances 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).There were significant differences between the 9 sections of the measurement value(P<0.05).The average distances of the shortest distance from cortical bone surface showed an increasing trend in the 2-4mm section from CEJ,and reaching the maximum in the 4mm section from CEJ,and decreasing after the 4mm section from CEJ.The mean value of each section was greater than 5mm.The shortest distances from cortical bone surface to the narrowest interradicular space of the left apical area(7-9mm from CEJ)had positive correlation with SNA angle,but the measurement value had no correlation with SNB angle and ANB angle.CONCLUSIONSThe distribution of interradicular spaces between the maxillary second premolar and first molar of adolescents with skeletal class II malocclusion was obtained by CBCT.These data might provide a reference for conducting mini-implants...