A study on horizontal reference planes in lateral cephalogram in Korean children

kim, Kyung Ho; Choy, Kwang Chul; Lee, Ji Yeon

Abstract

Various types of horizontal reference planes are used for diagnosis, treatment planning and evaluation of treatment results. But these reference planes lack accuracy and repro- ducibility, and are mainly for Caucasian. Unlike the adult patients who have completed growth, the horizontal reference planes for growing children may change continuously during growth, Therefore this must be considered in selecting the horizontal reference plane. The purpose of this study was to investigate the angle formed by the Sella-Nasion(SN) plane and Frankfort-Horizontal(FH) plane and evaluate the angle formed by FH plane and other horizontal reference planes in relation to different skeletal maturity and malocclusion types. 540 subjects with no orthodontic treatment history were chosen, and hand wrist X-rays and lateral cephalometric X-rays were taken, According to SMA(Skeletal maturity Assessment)of hand -wrist X-rays, the subjects were classified into 3 skeletal maturity groups ; SMI 1-2 for group A, SMI 5-7 for group B and SMI 8-11 for group C. A second classification was made according to cephalometric analysis of lateral cephalograms. The subjects were classified into 3 malocclusion group ; Skeletal Class I,II and III malocclusion group. 10 measurements were evaluated. The results were as follow. 1. The angle formed by the SN plane and FH plane showed no difference among skeletal maturity groups, malocclusion groups, and between sexes. 2. The angles formed by the SN plane and FH plane were 8.27degrees+/-2.31degrees for males and 8.59degrees+/-2.24degrees for females. The average value for females and males was 8.42degrees+/-2.28degrees. 3. The angle formed by the FH plane and palatal plane was almost constant showing no difference among skeletal maturity groups, malocclusion groups, and between sexes( 1.0 9degrees+/- 3.21degrees).