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.
Arm ; Cervix Uteri ; Esthetics ; Female ; Periodontal Ligament ; Tooth

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.
Adolescent ; Adult* ; Congenital Abnormalities ; Diagnosis ; Female ; Humans ; Male ; Skull Base

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.
Animals ; Cats ; Causality ; Dental Cementum ; Etidronic Acid* ; Hyalin ; Metabolism ; Periodontal Ligament ; Root Resorption* ; Tooth Movement* ; Tooth*

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.
Child ; Diagnosis ; Female ; Humans ; Longitudinal Studies* ; Male

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.
Child* ; Female ; Humans ; Mandible* ; Maxilla* ; Molar*

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.
Edible Grain ; Corrosion ; Elastic Modulus ; Elasticity ; Hot Temperature ; Orthodontic Wires ; Stainless Steel* ; Tensile Strength

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.
Finite Element Analysis* ; Head ; Humans* ; Maxilla* ; Orthopedics ; Skull ; Spine ; Sutures

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.
Tooth

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.
Axis, Cervical Vertebra ; Female ; Humans ; Male ; Molar ; Prosthodontics

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.
Adhesives ; Bicuspid ; Dental Enamel* ; Ethanol ; Hand ; Microscopy, Electron, Scanning* ; Rubber ; Tooth ; Tungsten