Digital imaging of film-based cephalograms using a digital camera / 대한치과교정학회지

As computer programs for cephalometric analysis were developed in diagnosis & treatment planning, digital imaging of film-based cephalograms came to be needed. When a digital camera is used, a problem encountered is the image distortion produced according to the focal length, which causes errors in indentifying landmarks. In addition, changes in the image size and compression ratio will inevitably produce a low quality image, causing errors in identifying landmarks. Hence, we have found the focal length producing the least image distortion when digital imaging the film-based cephalograms and the minimal digital camera setting which helps to identify the correct landmarks using the COOLPIX4500 digital camera (Nikon, Japan). The results were as follows: The image distortion was minimized at a focal length of 16.4mm (79.4mm when converted into a 35mm film camera) when digital imaging the film-based cephalograms. When wide imaging, with a focal length of under 16.4mm, barrel distortion was found and when tele imaging, with a focal length of over 16.4mm, pincushion distortion was found. The minimal digital camera setting was 2272 X 1704 pixel at normal (1/8) compression from which we can identify the correct landmarks at the same level as tracing the film-based cephalograms manually. As a result, when digital imaging the film-based cephalograms, using a COOLPIX4500 digital camera (Nikon, Japan), the focal length should be 16.4mm, the pixel image size over 2272 X 1704, and the compression ratio over normal (1/8).

The effect of treatment timing on maxillary protraction treatment response: A comparison of prepubertal and pubertal patients / 대한치과교정학회지

Treatment timing is a very important factor to consider in treating skeletal Class III patients by means of maxillary protraction. According to the literature maxillary protraction should be carried out at an early age before puberty. However, no scientific data were presented to support this statement and recent studies supported by statistical data showed disagreement concerning the optimum treatment time of maxillary protraction. Therefore, there is no agreement about the optimum treatment time of maxillary protraction. In this study hand-wrist X-rays were taken from 119 patients and subjects were grouped into prepubertal and pubertal group according to their skeletal maturity. Pretreatment and posttreatment lateral cephalometric X-rays were taken and treatment effects were compared. The average treatment time was 6.5 months for the prepubertal group and 6.1 months for the pubertal group. The obtained results were as follows; 1. The amount of maxillary forward movement was the same for prepubertal and pubertal group. 2. The amount of maxillary downward movement was the same for prepubertal and pubertal group. 3. The amount of mandibular downward and backward rotational movement was the same for prepubertal and pubertal group. 4. Dental effects were the same for prepubertal and pubertal group.

Cephalometric analysis of skeletal Class II malocclusion in Korean adults / 대한치과교정학회지

This study was performed to evaluate horizontal and vertical characteristics according to lateral cephalometry of adult Korean skeletal Class II patients using a selected horizontal and vertical reference planes of Koreans. 60 males and 60 females consisting of freshman of Yonsei University from 1996 to 1997 and patients with history of orthognatic surgery at the Dental Hospital of Yonsei University with a skeletal Class II profile were chosen and compared with 70 males and 70 females with normal occlusion. The skeletal Class II group had the following conditions: 1. Profile composed of a retrognathic mandible or protrusive maxilla; 2. Class II molar and canine key; 3. ANB-greater than 4o; 4. Wits appraisal-greater than 1.0 mm; Cephalometric analysis consisted of 22 skeletal, 25 soft tissue, 12 dental measurements. The results were as follows. 1. There was no considerable vertical measurement difference between the skeletal Class II malocclusion group and the normal occlusion group in skeletal analysis. But, some variations were found between the two groups in soft tissue analysis. 2. Mandibular length of the skeletal Class II malocclusion group was smaller than that of the normal occlusion group. Mandible was more posteriorly positioned in the Class II malocclusion group than in the normal occlusion group. 3. The length and antero-posterior position of the maxilla were not different between the Class II malocclusion and the normal occlusion group. 4. The antero-posterior position of the nose, upper lip and maxillary soft tissue, and nasolabial angle were not different between the two groups. 5. Mandibular soft tissue of the Class II malocclusion group was more posteriorly positioned than that of the normal. 6. The vertical measurements of the incisors(U1-HP, L1-MP) were bigger in the Class II malocclusion group than in the normal, but those of the molars(U6-HP, L6-MP) showed no significant difference between the two groups. 7. Classifying the skeletal Class II malocclusion group according to the antero-posterior position of both jaws, normally positioned maxilla and retruded mandible was 43.3%, both normally positioned maxilla and mandible 28.3%, both retruded maxilla and mandible 20.0%..

The relationship between menarche and the ossification stages of the phalanx of the first and third finger / 대한치과교정학회지

Among many maturation indicators of growing patients, menarche and skeletal maturity are useful to assess growth and development, and the changes of the first and third finger are relatively important in hand-wrist X-rays. The objective of this study was to evaluate the relationship between menarche and the changes of the phalanx of the first and third finger and compare skeletal maturation among different malocclusion types. The sample used in this study was 29 Class I, 27 Class II and 27 Class III females whose hand-wrist X-rays had been taken with 6 month interval before the appearance of ulnar sesamoid ossification till the phalanges of the fingers were almost fused. The results were as follows. 1. There was no skeletal maturity difference among malocclusion types. 2. There was no difference in the mean chronologic age of menarche among different malocclusion types and that was 12.30+/-0.98 years. 3. The ulnar sesamoid was observed at 10.35+/-1.01 years, and on distal phalanx of the first finger, epiphyseal capping appeared at 11.26+/-1.04 years and fusion at 13.12+/-1.06 years. The epiphyseal capping on middle phalanx of the third finger was observed at 11.57+/-1.02 years and fusion at 13.72+/-1.04 years. 4. The timing of menarche occurred around the same time as the fusion process of distal phalanx of the first finger(p<0.001, r=0.82) and the initiation of fusion of middle phalanx of the third finger(p<0.001, r=0.78). Therefore, we can give the aid when we evaluate the growth and development of growing females seeing the changes at phalanx of the first and finger.

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.

An experimental study on the stress distribution in the periodontal ligament / 대한치과교정학회지

In order to achieve a desirable tooth movement, it is of great importance to control the M/F ratio and to know the location of the center of resistance. The purpose of this study was to locate the center of resistance and the axis of rotation, and to estimate the stress distribution in the periodontal ligament with experimental model. After preparing a model of an upper canine with a simulated periodontal ligament and alveolar bone, the force and moment were applied. The tooth movement was traced using measuring device with LVDTs(Linear variable differential transformers) that can measure three dimensional tooth movement in real time. The results were as follows. 1. The location of center of resistance by transverse force was 29% of root length measured from alveolar crest to apex regardless of force magnitude. The position of the center of resistance is more coronal than that of two-dimensional model(42%). 2. The center of resistance and the axis of rotation coincide when couple moment was applied. 3. As the magnitude of moment increases, tooth tends to extrude irrespective of the direction of the moment. 4. The relationship between location of force and axis of rotation (a x b =49.6mm2) was obtained. A tooth movement can be predicted through this formula. 5. The centers of rotation by transverse force were plotted linearly.

Torsional moment of orthodontic wires / 대한치과교정학회지

system may include bending force in first and second orders and a torsional force in third order. Analytical and experimental studies on bending force have been introduced, but information about torsion is still lack. The purpose of this study was to estimate the torsional moment in the force system of rectangular arch wires through theoretical and experimental studies. Wires most frequently used for third order control were selected as study materials. Cross sections of 0.016X17.022, 0.0174.025, 0.0194.025 inch rectangular wires in four different materials such as stainless steel (O mco), TMA (Ormco), NiTi (Ormco), and braided stainless steel (DentaFlex, Dentaurum) were used. The torque/twist rate of each test material was calculated using the torsion fotiuula Torque/twist rate, yield torsional moment, and ultimate torsional moment were measured with a torque gauge. The torsion formula assesses that the torque,/twist rate (T/theta) is proportional to the characteristics of material(G) and cross section (J), and is inversely proportional to the length of wire (L). Most experimental results conesponded with the formula. The relative stiffness was calculated for reference to a logical sequence of wire changes.

The vertical changes of the lip and perioral soft tissue resulting from incisor retraction / 대한치과교정학회지

Patients who want to reduce their lip protrusion usually estimate the severity of the lip protrusion on the frontal aspect. Most orthodontists have a perplexed experience of a reduced thin line of vermilion border on the frontal aspect as incisors are retreated, even though the lip protrusion is thought to be reduced favorably on the sagittal aspect. Some patients, also look older after orthodontic treatment because of severe lip thinning. This unaesthetic reduction of vermilion border urges us to study the vertical lip change during orthodontic procedure. The purpose of this study was to evaluate the vertical lip and perioral soft tissue changes in respect to incisor retraction in an effort to analyze which factors might be responsible for their vertical changes, using the multiple regression analysis. The results were as follows. 1. Upper and lower lip philtrum length(SnLs, LiB') were increased after retraction of anterior teeth, were as upper and lower vermilion height(LsStms, StmiLi), and vermilion length(LsLi) were decreased. 2. Upper and lower lip length(SnStms, StmiB'), and soft tissue lower anterior facial height(SnMe') did not show any significant difference after treatment. 3. The increase of the upper lip philtrum length was mainly influenced by the extrusion of upper anterior teeth(U1V), and the increase of the lower lip philtrum length was mainly influenced by the initial overjet before treatment. 4. The decrease of the upper and lower lip vermilion height was mainly influenced by the decrease of upper lip thickness.

Factors affecting force system of orthodontic loop spring / 대한치과교정학회지

The shape of orthodontic retraction spring was varied and force system of each case was obtained using numerical analysis and verified with spring tester. The factors for obtaining biomechanically efficient spring under anatomic limitation were suggested as follows. 1. M/F ratio increases and L/D rate decreases as loop height increases. 2. M/F ratio increases and L/D rate decreases as incorporating more wire above bending moment area. 3. M/F ratio decreases and L/D rate decrease as incorporating more wire above bending moment area. 4. M/F ratio can not be greater than spring height no matter how much wire is incorporated at the apex of the loop. 5. Additional moment is necessary to obtain enough M/F ratio for translation under anatomical limitation. 6. Additional moment should be incorporated at every part of the spring because M/F ratio and L/D rate decreases as horizontal spring length increases. 7. Material, cross section, and shape of the spring influence L/D rate, whereas M/F ratio is influenced by the shape of the spring independent from material and cross section.

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).

Orthodontic traction of impacted tooth / 대한치과교정학회지

Tooth impact on may lead to malocclusion, root resorption, cyst or aberrant changes in adjacent teeth Clinical and radiographic examinations are used to locate the impaction, and appropriate treatment plans must be made to relocate the impacted tooth. When surgically exposing the impacted tooth, periodontal considerations to conserve maximum amount of soft and hard tissue are used Oral hygiene instructions are emphasized to maintain sound periodontal health. Securing enough space for .the impacted tooth and proper anchorage is important. Proper use of force and mechanics is crucial to prevent such complications as root resorption. Various patterns of orthodontic traction may be employed as situation permits. Most impaction cases can be managed with orthodontic traction to restore function and esthetics, provided that early detection and proper diagnosis and treatment planning are made.

Malocclusion with congenital missing of lower incisors / 대한치과교정학회지

Positions, angulation and mesiodistal dimension of lower incisors are important in esthetics, occlusion and post-treatment stability of lower arch. When lower incisor is congenitally missing, problems such as increased overjet and overbite, closing in of adjacent teeth and size/space discrepancies may occur. When creating treatment plans, incisor position and angulation, lip support, anteroposterior skeletal relationship canine-molar relationship, overjet, overbite, remaining growth potential, crowding and anterior tooth ratio have to be considered. For an accurate analysis of incisal size discrepancy, diagnostic model set-up may be helpful. The two patients in this presentation both had two lower incisor missing, but the degree of crowding, skeletal relationship, lip support, molar relationship are different, and therefore treatment plan was different as well. Long term follow-up may be necessary for stability and retention.

Semi-longitudinal study of growth and development of cranio-facial soft tissue of children aged from 3 to 11 / 대한치과교정학회지

Today's orthodontic treatment goals lie in functional esthetics, and the importance of the latter is increasing gradually in trend. Considering such, study on growth and development of soft as well as hard tissues becomes inevitable. Early studies emphasize mainly plays a critical role in determining data. However, more recent studies report that maxillofacial soft tissue, which plays a critical role in determining facial eathetics, is influenced by underlying hard tissue, and yet close relationship between them was not noticed. Cephalometric x-rays were taken of 137 Korean boys and 106 girls with no systemic disease, fair developmental status and normal occlusion for two consecutive years; afterwards, soft tissue analysiss, which was divided into four parts, facial form, lip position & posture, nose, and thickness, was done to correlate tham with general growth.

Analysis of force system developed by continuous straight archwire / 대한치과교정학회지

Determination of force system and prediction of side effects from unbent straight wire engaged in edgewise bracket is clinically very difficult because it is statically indeterminate system. This study is to develop a linear beam theory that explains the force system for straight wire engaged in edgewise bracket regardless of geometry(a/b), material, cross section of wire, and interbracket distance. 1. Formula for force system of bilateral fixed end beam was derived. 2. It is possible to calculate force system of each tooth engaged in continuous straight wire. 3. The possibility and location of permanent deformation can be predicted.