The Longitudinal Sagittal Growth Changes of Maxilla and Mandible According to Quantitative Cervical Vertebral Maturation

To investigate the longitudinal sagittal growth changes of maxilla and mandible according to the quantitative cervical vertebral maturation （QCVM） for adolescents with normal occlusion, mixed longitudinal data were used. The samples included 87 adolescents aged from 8 to 18 y old with normal occlusion （32 males, 55 females） selected from 901 candidates. Sequential lateral cephalograms and hand-wrist films were taken once a year, lasting for 6 y. The longitudinal sagittal growth changes of maxilla and mandible according to QCVM were measured. There were some significant differences between maxilla and mandible according to QCVM. The sagittal growth change of maxilla showed a trend towards high velocity→decelerating velocity→completing velocity from QCVM stage Ⅰ to stage Ⅳ. The sagittal growth change of mandible showed a trend towards accelerating velocity→high velocity→decelerating velocity→completing velocity from QCVM stage Ⅰ to stage Ⅳ. With sagittal relationship, growth magnitude was almost the same between maxilla and mandible at QCVM stage Ⅰ . At stage Ⅱ the growth of mandible exceeded that of maxilla and growth in mandible continued at stages Ⅲ and IV, while the maxilla ceased to grow. Growth magnitude was greater and the growth duration was longer with male mandible. It is concluded that the longitudinal sagittal growth changes of maxilla and mandible on the basis of QCVM is of value in the orthodontic practice.

Accuracy and Repeatability of Computer Aided Cervical Vertebra Landmarking in Cephalogram

The accuracy and repeatability of computer aided cervical vertebra landmarking (CACVL) were investigated in cephalogram.120 adolescents (60 boys,60 girls) aged from 9.1 to 17.2 years old were randomly selected.Twenty-seven landmarks from the second to fifth cervical vertebrae on the lat-eral cephalogram were identified.In this study,the system of CACVL was developed and used to iden-tify and calculate the landmarks by fast marching method and parabolic curve fitting.The accuracy and repeatability in CACVL group were compared with those in two manual landmarking groups [orthodon-tic experts (OE) group and orthodontic novices (ON) group].The results showed that,as for the accu-racy,there was no significant difference between CACVL group and OE group no matter in x-axis or y-axis (P>0.05),but there was significant difference between CACVL group and ON group,as well as OE group and ON group in both axes (P<0.05).As for the repeatability,CACVL group was more reli-able than OE group and ON group in both axes.It is concluded that CACVL has the same or higher ac-curacy,better repeatability and less workload than manual landmarking methods.It’s reliable for cervi-cal parameters identification on the lateral cephalogram and cervical vertebral maturation prediction in orthodontic practice and research.