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.

An electromyographic study of muscle activity in normal occlusion and skeletal Class III malocclusion in adult / 대한치과교정학회지

The purpose of this study was to investigate the relationship among the activity of the craniofacial muscle and craniofacial form and occlusal state. In this study, subjects were consisted of 23 male adults with skeletal Class III malocclusion and 30 male adults with normal occlusion. The measurements in oral exam, lateral cephalograrn, and F.M.G. recordings of anterior temporal, masseter, and upper lip muscles at rest position, clenching in centric occlusion, chewing of gum, swallowing of juice, were analyzed with SPSS system. The results were as follows: 1. At rest position upper lip muscle activity of skeletal Class III group was significantly higher than that of normal group. 2. Both clenching and chewing masseter and temporal muscle activity of normal group were significantly higher than that of skeletal Class III group. 3. During swallowing of juice, upper lip muscle activity of skeletal Class III group were significantly higher than that of normal group. 4. The activities of masseter and anterior temporal muscle during clenching and chewing were significantly correlated with hypodivergent facial form and number of occluded teeth. 5. The activity of upper lip during swallowing had positive correlation with mandibular prognathism.

A study of root resorption and alveolar bone changes during tooth movement after treatment with etidronate disodium / 대한치과교정학회지

Many studies has been conducted concerning prevention of unnecessary complications such as root resorption during orthodontic tooth movement under various mechanical forces. Nowadays, the cause of the root resorption is not thought to be confined only to mechanical forces. But the factor that affects bone metabolism are thought to be major one of the predisposing factors. The light microscope and scanning electron microscope were used to the effects of 60gm, and 100gm of tipping force on root resorption of cats, which were treated with Etidronate disodium. The results were as follows: 1. In the 60gm control group, hyalinization on the compression site of periodontal ligament appeared after first week and second week. In the 60gm experimental group, it appeared after first week with low frequency. In the 100gm control group it appeared with high frequency by first and second week while in 100gm experimental group, it appeared with low frequency. 2. In the 100gm control group, resorption of the cementum and the alveolar bone rapidly increased after second week. In the 60gm experimental group, resorption or formation of alveolar bone and cementum didn't appear all through the experimental period. 3. In the 100gm control group. formation of cementum and alveolar bone appeared after first week while in the 100gm experimental group, formation of cementum and alveolar bone appeared after second week and fourth week respectively. In the 60gm control group, formation of the cementum didn't appear all through the experimental period. 4. In the control group, the root resorption of 100gm group was higher than that of 60gm group after second week, while in experimental group, root resorption didn't appear regardless of the forces.

A longitudinal study of the changes in the anteroposterior apical base relationship between 6 and 13 years of age / 대한치과교정학회지

To help arrive at a more accurate diagnosis of anteroposterior apial base relationship on each individual case, it is important to compare the interpretation in the same population on a longitudinal basis. The author studied on the changes of the anteroposterior apical base relationship using serial lateral cephalometric roentgenograms of 15 boys and 27 girls aged from 6 to 13 years of Korean children. Fallowing results were obtained: 1. Norms of Korean boys and girls were established. 2. With ages, there was a gradual decrease of ANB, AXB angle, and there was a gradual increase of Facial angle, A-B plane angle, APDl. 3. Wits appraisal does not change significantly with ages. 4. No significant differences were observed in the changes between male and female subjects for all absolute values between the ages of 6 years and 12 years, but significant differences were observed in ANB, AXB, A-B plane angle of the age of 13 years. No significant differences were observed in the changes between male and female subjects for all incremental values between the ages of 6 years and 13 years.

A study on initial changes during canine retraction by the finite element method / 대한치과교정학회지

Retraction of canines represents a fundamental stage in a considerable number of orthodontic treatment. Correct position of the canine after retraction is most important for function, stability, and esthetics. The purpose of this study was to investigate the stress in the periodontal tissue at the initial phase during canine retraction using various types of sectional retraction springs, by finite element method. Three dimensional model of tooth, periodontal ligament, bone and eight springs were simulated and tested. The following results were obtained. 1. In sectional retraction springs, increasing number of helix and the closed loop in preference to the open loop provided an decrease in horizontal force. Without angulating the arms of spring, the T-loop revealed the highest Moment-to-force ratio. 2. The Moment-to-force ratio raised by angulating mesial and distal arms of spring, but very large horizontal force was applied to canine. 3. When optimal force and optimal moment was applied to canine, the stress induced was homogeneous and the difference of stress value from cervix to the apex was little.

A study on growth changes of maxilla and mandible and position changes of first permanent molars of growing children / 대한치과교정학회지

The purpose of this study was to investigate the growth changes of maxilla and mandible and position changes of first permanent molars of growing children. The author analyzed the data using cephalometric roentgenogram of 43 boys and 39 girls age of 6 to 11 with normal occlusion. The obtained results were as follows 1. The eruption path of maxillary and mandibular first permanent molar superimposed on TM-ANS and mandibular plane shows individual variation. 2. There was no correlation between horizontal and vertical changes of maxillary first permanent molar, but positive correlation in mandibular first permanent molar. 3. As the eruption, the forward changes of mandibular first permanent molar was significantly greater than that of maxillary first permanent molar. 4. As the ages were increased, there were irregular growth changes of maxilla and mandible. 5. Growth changes of lower anterior facial height was relatively stable. 6. N-S-6 was stable after age 7.

A study on the cyclic AMP in the alveolar bone of rats applied by orthodontic forces in experimental diabetes and insulin treatment / 대한치과교정학회지

The physical tooth movement by orthodontic force is based upon alveolar bone resorption at compression site and new bone formation at tension site of the alveolar socket. The function of the cyclic AMP is to participate not only in initial action of bone cells by mechanical forces but also in the continuous cellular response leading to bone remodelling. This experiment was performed to clarify the role of cyclic AMP in bone remodelling by mechanical force In the NORMAL group, the DIABETES group and the INSULIN TREATED group. The 72 rats were divided into the NORMAL group, the DIABETES group and the INSULIN TREATED group. The same orthodontic forces were applied to the rats of 3 groups. These rats were treated for periods of time ranging from 1 hour, 1 day, 7 days, 14 days, 21 days and 28 days. The samples of alveolar bones were obtained from compression and tension sites surrounding the tipping teeth from NORMAL, DIABETE and INSULIN TREATED rats. The samples were assayed for cyclic AMP by the cyclic AMP RIA kit. The results were as follows 1. The cyclic AMP levels of alveolar bone in compression and tension sites showed initial decrease, then increased and remained elevated by the time consuming. 2. The highest cyclic AMP level showed in the DIABETES group and the lowest level was In the NORMAL group. 3. The cyclic AMP levels In the INSULIN TREATED group was similar with the NORMAL group in control and tension sites, but in the compression sites it was similar with the DIABETES group.

A study of the crown inclination in normal occlusions / 대한치과교정학회지

Recently, straight-wire appliance is widely used with great concern in clinical orthodontic field. The purpose of this study was to collect the information of the straight-wire appliance and to determine the crown inclination in clinical orthodontics. The author analyzed the study model of 78 individuals with normal occlusion. The obtained results were as follows. 1. Mean, maximum value, minimum value and standard deviation of crown inclination of upper and lower teeth were obtained. 2. The lingual crown inclination of upper tooth had constant value from first premolar through second molar, the lingual crown inclination of lower tooth progressively increased from canine through second molar 3. As Howes' ratio was decreased, the crown inclination of upper incisors was increased. 4. Narrowing the upper arch, the crown inclination of upper incisors was increased.

A finite element analysis on the effect of the headgear in human maxilla / 대한치과교정학회지

The pufpose of this study was to analyze the stress distribution and the displacement in the maxillary complex after the application of the three kinds of the head gear.(high pull head gear, straight pull head gear, cervical pull head gear.) Orthopedic force, 200 gram, was applied to the maxilla of the dry human skull in a high, straight and cervical direction. The stress distribution and the displacement within the maxillary complex was analyzed by a 3-dimensional finite element method. The results were as follow: 1. In corwn, the stress of cervical pull head gear was the greatest stress and straight pull head gear was the medium stress and high pull head gear was the least stress. 2. The compressive stress was observed on the anterior portion of premaxilla, especially anterior nasal spine area, when the three kinds of head gear were applied to the dry kuman skull. 3. In apeared that the stress of the anterior portion of thr zygomatic bone was greater than the posterior portion in the case of three kinds of head gear application and compressive stress was noted only at the below of the frontozyomatic suture of the zygomatic bone. 4. The backward, upward, sideward displacement of the alveolar area was observed in a high pull head gear application but in the case of straight pull head gear and cercical pull head gear application, the backward, downward, sideward displacement was observed. 5. The forward, downward, sideward displacement was observed on the midpalatine suture and premaxilla on the sagittal plane and transverse palatine suture in the case of three kinds of headgear application.

A comparative study on physical properties of orthodontic stainless steel wires / 대한치과교정학회지

The requirements of orthodontic wire should include chemical stability, non-discoloration and non-corrosion in oral environment. Ability to be soldered, ease of fabrication and elasticity should be also considered. The purpose of this study was to compare and analyze the physical properties of Tru-chrome. The results were as follows: 1. Tru-chrome wire and E.S.S. wire were SUS 304 which was 18 Cr-8Ni austenite stainless steel. There was not significant difference in each composition between two wires. 2. There were not significant differences in ultimate tensile strength, yield strength, elongation and modulus of elasticity between Tru-chrome and E.S.S. wires. 3. There was not significant difference between flexure modulus of elasticity of Tru-chrome and E.S.S. wires. 4. Micro-hardness value of E.S.S. wire was more than that of Tru-chrome wire and they were softened significantly by solution heat reatment. 5. Micro-structure of Tru-chrome and E.S.S, wires showed fibrous interlocking grains, and an austenite structure after solution heat treatment. 6. There was significant difference between corrosion rate of Tru-chrome and E.S.S wires.

A cephalometric study of dentofacial morphology in relation with facial growth pattern / 대한치과교정학회지

The author compared patients with extreme variations in MP-SN angle with normal group in order to examine the relationship between the MP-SN angle and other skeletal and dental parameters. The results were as follows; 1. The OP-SN angle and OP-MP angle decreased as the MP-SN angle decreased. 2. As the MP-SN angle decreased, the skeletal and dental components became more anteriorly situated. 3. In high MP-SN group, TFH, UFH, LFH, OP-MP, ADH increased nore than those in average MP-SN group. 4. The RH/TFH ratio decreased as the MP-SN increased.

Enamel surface evaluation on various removal technique of bracket (DBS): a study with the scanning electron microscopy / 대한치과교정학회지

With modification of the acid etch technique and improvements of the physical and mechanical properties of the acrylic reain, the removal of directly bonded attachments and the finishing of the underlying enamel have become an acute clinical problem. This study was to evaluation the efficacy of recently introduced instrumentation and techniques to remove bonded brackets and residual resin, and restore the affected enamel surface to an acceptable clinical condition. Fortyeight premolar which were scheduled for extractio for orthodontic purposes were bonded with brackets usion super-C oftho. Four additional premolars with untreated surfaces were used as controls. After one weak the grackets were removed and the residual resin removed by hand scaler, green stone, green rubber wheel, sandpaper disc, tungsten carbide bur, Sof-lex disc. Half the experimental teeth were given a final pumicing and then all were extracted and stored in 50 percent ethanol. The scanning electron microscopy was used to evalusted the enamel surface. Following results were obtained; 1. A satisfactory result was obtained by means of the Sof-lex disc. 2. The order of the scratch formation was the procedure using hand scaler, green stone, tungsten carbide bur, sandpaper disc, green rubber wheel, and Sof-lex disc. 3. The procedures using green stone and tungsten carbide bur showed many groove formations and the other procedures showed none. 4. Final pumicing serves effectively to remove residual adhesive and restore the enamel surface.

Roentgenocephalometric study of craniofacial growth by Ricketts analysis on teen-ager with normal occlusion in Korean / 대한치과교정학회지

This study was performed to establish the cephalometric standards and growth change of Korean teen-age group by Ricketts analysis. A roentgrnocephalometric study was made from 365 subjects, that consist of 159 males, 206 frmales with normal occlusion, acceptable profile and no history of otrhodntic and prosthodontic treatment. The results were as follows: 1. The tables of means, standard deviation from measured values were made, (male, female, both sex). 2. The tables of regression rquations from measured values were made to establish the relationship between age and each item. (male, female, both sex). 3. All linear measurements of each item m male were treater than m females. 4. Items which show more linear than any other items were condyle axis, facial axis length, corpus length and uppwe molar position.

A finite element analysis of the stress distribution and displacement in human maxilla to rapid palatal expansion / 대한치과교정학회지

Recently, rapid palatal expansion technique is widely used for the correction of the skeletal imbalance in Cl III malocclusion patients. There were many studres about the cephalometric changes to rapid palatal expansion but quantitative analysis were small. The purpose of this study was to analysis the stresses and displacement of the maxilla in human dry skull to rapid palatal expansion. The results were as follows. 1. The anterior portion of palate show more lateral and inferior displacement than the posterior portion. But the posterior portion show more anterior displacement. 2. In transpalatal suture area, the medial portion show more lateral displacement than the medral portion. 3. In mid-sagittal plane, the power portion (palatal area) of maxilla show more anterior, lateral, inferior displacement than the upper portion (forntamaxillary stuture area). 4. In zygomatic arch, the abjacent area to maxilla show tensile stresses and the abjacent area to forntal bone show compressive stresses. 5. The sequence of stress bearng area to R.P.E is upper retromolar area, upper 1st molar, 1st premolar, 2nd premolar, anterior segment of teeth.

A finite element analysis on the effect of the reverse headgear to the maxillary complex / 대한치과교정학회지

The purpose of this study was to analyze the stress distribution and the displacement in the maxillary complex after the application of the reverse headgear. The direction of force was parallel to the occlusal plane. Orthopedic force, 300gm, was applied to the maxilla of the dry human skull in a forward direction. The stress distribution and the displacement within the maxillary Complex was analyzed by a 3-dimensional finite element method. The results were as follows: 1. The stress distribution at the molar regron was greater than that at the anterior. 2. The stress distribution at the lateral side of the premaxilla was greater than that at the middle side, especially high stress was noted at the canine eminence. 3. Compressive stress was noted only at the forntozygomatic suture of the zygomatic arch. 4. A forward, upward, and sideward displacement was noted at the entire nodal points of the zygomaticomaxillary suture portion. A displacement with a slight rotation was observed on the transverse palatine suture. 5. The maximum stress was observed at the lateral side of the maxillary tuberosity area, and generally the forward and downward displacement was noted at all this area.

Cephalometric analysis of maxillofacial normals in Korean adults / 대한치과교정학회지

This study was performed to aid for the case analysis and diagnosis of the maxillofacial deformities. A cephalometric analysis was made form 101 subjects over 18 years old, that consisted of 46 males and 55 females with normal occlusion, acceptable profile. The results of this study were obtained as follows: 1. The tables of normals in adult male and female were made. 2. The angles of SNO were 65.5degrees in male and 65.3degrees in female and the horizontal linear measureaments from 0 to NA(O-NA) were 9.0mm in male and 8.9mm in female. 3. The cranial base angles (SN-FH) were 8.2degrees in male and 10.3degrees in female and the mandibular plane angles (OP-HP) were 28.1degrees in male and 26.2 in female. 4. The correlation of (O-NA) to S-O/S-A and S-O/S-N were higher than SNO, and the correlation of (N-A) to SNA and (N-B) were high.

Frankel appliance / 대한치과교정학회지

No abstract available.