Formulation of a reference coordinate system of three-dimensional head and neck images: Part II. Reproducibility of the horizontal reference plane and midsagittal plane / 대한치과교정학회지

This study was performed to investigate the reproducibility of the horizontal and midsagittal planes, and to suggest a stable coordinate system for three-dimensional (3D) cephalometric analysis. Eighteen CT scans were taken and the coordinate system was established using 7 reference points marked by a volume model, with no more than 4 points on the same plane. The 3D landmarks were selected on V works (Cybermed Inc., Seoul, Korea), then exported to V surgery (Cybermed Inc., Seoul, Korea) to calculate the coordinate values. All the landmarks were taken twice with a lapse of 2 weeks. The horizontal and midsagittal planes were constructed and its reproducibility was evaluated. There was no significant difference in the reproducibility of the horizontal reference planes. But, FH planes were more reproducible than other horizontal planes. FH planes showed no difference between the planes constructed with 3 out of 4 points. The angle of intersection made by 2 FH planes, composed of both Po and one Or showed less than 1 degrees difference. This was identical when 2 FH planes were composed of both Or and one Po. But, the latter cases showed a significantly smaller error. The reproducibility of the midsagittal plane was reliable with an error range of 0.61 to 1.93 degrees except for 5 establishments (FMS-Nc, Na-Rh, Na-ANS, Rh-ANS, and FR-PNS). The 3D coordinate system may be constructed with 3 planes; the horizontal plane constructed by both Po and right Or; the midsagittal plane perpendicular to the horizontal plane, including the midpoint of the Foramen Spinosum and Nc; and the coronal plane perpendicular to the horizontal and midsagittal planes, including point clinoidale, or sella, or PNS.

Cephalometric norms of the hard tissues of Korean for orthognathic surgery

This study was performed to evaluate hard tissue cephalometric norms for Korean adults which can be implemented in surgical orthodontic treatment planning using selected horizontal reference plane especially for Koreans (Male: SN-7.5degreeC, Female: SN-9.0degreeC) and a simplified analytical method. 70 males and 70 females consisting of freshmen of Yonsei University from 1996 to 1997 and students from the Dental College of Yonsei University were chosen according to clinical examination and cephalometric analysis. The samples had normal profiles, normal anteroposterior skeletal relationship(ANB angle of 0degreeC to 4degreeC and Wits appraisal of -4.0mm to 0mm) , and Class I molar and canine relationship. They had no missing or supernumerary teeth and had no experience of orthodontic or prosthetic treatment. After the selection of 23 landmarks and the construction of horizontal and vertical reference lines, 22 skeletal and 12 dental measurements were taken. These consisted of vertical and horizontal linear measurements and angular measurements. The results were as follows. 1. Mean and standard deviation of the measurements were calculated for males and females. 2. Most of the skeletal vertical measurements, and maxillary and mandibular length were bigger in males than females. Whereas anterior facial height ratio(N-ANS/ANS-Me) as well as maxillary and mandibular antero-posterior position in relation to the vertical reference line(N-perpendicular) showed no signigicant difference between sexes. 3. Maxillary and mandibular dental antero-posterior position in relation to the vertical reference line(N-perpendicular) showed no significant difference between sexes. 4. The upper incisor show(U1-Stms) was 2.1+/-1.7mm in males and 3.3+/-1.7mm in females. In this study, hard tissue cephalometric norms of Korean adults for orthognathic surgery were obtained.

Cephalometric norms of the soft tissues of Korean for orthognathic surgery

This study was performed to evaluate soft tissue cephalometric norms for Korean adults which can be implemented in surgical orthodontic treatment planning using selected horizontal reference plane especially for Koreans (Male: SN-7.5degreeC, Female: SN-9.0degreeC) and a simplified analytical method. 70 males and 70 females consisting of freshmen of Yonsei University from 1996 to 1997 and students from the Dental College of Yonsei University were chosen according to clinical examination and cephalometric analysis. The samples had normal profiles, normal anteroposterior skeletal relationship(ANB angle of 0degreeC to 4degreeC and Wits appraisal of -4.0mm to 0mm), and Class I molar and canine relationship. They had no missing or supernumerary teeth and had no experience of orthodontic or prosthetic treatment. After the selection of 15 soft tissue landmarks and the construction of horizontal and vertical reference lines, 25 measurements were taken. These consisted of vertical and horizontal linear measurements and angular measurements. The results were as follows. 1. Mean and standard deviation of the measurements were calculated in males and females. 2. Vertical measurements were comparably bigger in males than females whereas anterior facial height ratio(sN-Sn/Sn-sMe) and lower anterior facial height ratio(Sn-Stms/Stmi-sMe) showed no significant difference between sexes. 3. Most of the horizontal measurements in relation to the vertical reference line(G-perpendicular) showed no significant difference between sexes. 4. Nasofacial angle, columellar angle, nasolabial angle and facial contour angle showed no significant difference between sexes. 5. The upper and lower lip were positioned about -1.0+/-2.0mm and +1.0+/-2.0mm in relation to the Ricketts' esthetic line in both sexes. In this study, soft tissue cephalometric norms of Korean adults for orthognathic surgery were obtained.

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

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).

A study on horizontal reference planes in lateral cephalogram in Korean adults / 대한치과교정학회지

The purpose of this study was to investigate the angle formed by the Sella-Nasion(SN) plane and Frankort-Horizontal(FH) plane and evaluate the correlation and difference of the FH plane to other horizontal reference planes. Through this study we hope to present a basis for selecting a horizontal reference plane which can be implemented in cephalometric studies and in surgical orthodontic treatment planning. 600 subjects were chosen following a clinical examination and lateral cephlometric X-rays were taken. According to cephalometric analysis the subjects were classified into 3 groups; Skeletal Class I malocclusion or normal occlusion group(male 50, female 50), Skeletal Class II malocclusion group(male 50, female 65) and Skeletal Class III malocclusion group(male 50, female 50). The results were as follows. 1. The angle formed by the SN plane and FH plane showed no difference among the malocclusion groups, but there was a significant sex difference. For males the angle measured was 7.47degrees+/-2.40degrees whereas for females it was 8.93degrees+/-2.72degrees. 2. The angle formed by the SN plane or FH plane and Mandibular plane was higher in females for all malocclusion groups. This angle in the Skeletal Class I malocclusion group was 1 awer than in the other two groups. 3. There was no difference among the sexes or malocclusion groups con ,idering the angle formed by the FH plane and Palatal plane. 4. The gonial angle in the Skeletal Class III malocclusion group was higher than in the Skeletal Class I and Class II malocclusion groups- in both sexes.