Cervical Bone Age Mandibular Growth Prediction Of Adolescent Females

Objective: Taking cervical vertebral bone age as standard, establish mandibular growth graph for adolescent girls of China, and discuss growth and development course and morphologic characters in various cervical vertebral bone age stages for mandibula, according which we can predict peak growth velocity and development potential of mandibula, and provide theoretic bases for diagnosis of mandibular abnormity and curative effect of orthodontics or maxillofacial surgery, and the time of maxillofacial surgery operation.Method: 1.A study on accuracy in repeated measurements of digital cephalometric radiograph. The author identified and measured 5 landmarks of mandibula two times according to ten digital cephalometric radiographs selected randomly, then the mean error of measurements were determined.2.Drawing mandibular growth graph as cervical vertebral bone age for basis. Using digital cephalometric radiographs of 288 girls (ages 10.0-17.9), we measured targets of C3,C4, and obtained cervical vertebral bone ages(CBAYK,CBAMito)by computer, according which we separated all the objects for eight groups (10.0—10.9;11.0—11.9;12.0—12.9;13.0—13.9;14.0—14.9;15.0—15.9;16.0—16.9;17.0—17.9). Then we drawed growth graphs of mandibular length, ramus height and mandibular body length according to CBAYK,CBAMito, and compared P50 graphs of them.Results: 1.The mean error of digital cephalometric radiograph was lower than 0.5mm in length repeated measurements and lower than 0.2°in angle repeated measurements, and there was no significant differences in statistics. These results suggest that the selected landmarks of mandibula are identified easily and the error of repeated measurement can be neglected.2. The adolescent Chinese girls'mandibular growth enters accelerated stage at 10.0 years old, peak growth velocity stage is in 11~12 age, and after 15 years old the velocity is decelerated obviously. We can also find that the mandibular length is increased mostly throughout the adolescent, and the mandibular peak growth velocity stage of Japanese girls is one year earlier than Chinese girls. Through the mandibular growth graph, we can decide the most proper orthodontics and operative time or method, at the same time it also provide bases of comprehending mandibular growth of adolescent Chinese girls and evaluating individual development more accurate.Conclusion: The mandibular growth graph of adolescent Chinese girls which is according to cervical vertebral bone age is a reasonable and reliable method for prediction of mandibular growth and development.