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A FEM analysis for initial stress on the upper canine by orthodontic force of intrusion arch wire activation.

Jeong Weon KANG ; Kyung Suk CHA ; Jin Woo LEE

Korean Journal of Orthodontics.1998;28(3):391-398.

The purpose of this study was to find the distribution and measurement of compressive and tensile stress when intrusi- on arch wire is forced engage with upper canine and to analysis stress at each section through FEM. And we compare compressive and tensile ratio at each section. The results were as follows. 1. At FA point and cemento-enamel junction of upper canine, compressive and tensile force ratio is about the same. 2. At apex, compressive force is the four times as tensile force. ; In intrusion, we show root resorption at apex. 3. At Cemento-enamel junction, the compressive and tensile force show the maximun value except FA point.
Root Resorption

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A study on the effect of the chincap by finite element analysis in juvenile skeletal Class III patients.

Jeong Ho CHOI ; Won Sik YANG

Korean Journal of Orthodontics.1998;28(3):353-370.

This study was conducted to investigate the changes in the structural parts of the craniofacial skeleton subsequent to chincap therapy in the juvenile skeletal Class Ill Patients. The subject consisted of 29 Korean children(14 males, 15 females) who had skeletal Class M malocclusion and were undergone chincap therapy from the beginning of the treatment (and an auxiThary upper removable appliance, if necessary). The control group was composed of 21 children(10 males, 11 females) with skeletal Class Ill malocclusion who had no orthodontic treatment. Cephalometric data at the mean age of 7 and 2 years later were analyized by finite element method, and compared between groups by independent group t-test(p<0.05). The results of the present study were as follows; 1. There were no significant changes in the cranial base, posterior face, upper anterior face, ramus, chin and soft tissues by the chincap therapy. 2. The mandibular body showed significant differences in the minimum extention ratio and the overall shape ratio. This means that the vertical direction of growth was retarded by the chincap therapy. 3. The major direction of the growth in the maxillary basal bone was significantly more horizontal in the experimental group, which suggests that the vertical growth of maxilla was inhibited. 4. There was statistical difference in the major direction of the growth of the anterior face between groups. This may be due to the significant difference in the major direction of growth of the lower anterior face, supposed to be resulted from the mandibular rotation and/or displacement by the chincap therapy. The change in the oral functional space seemed to be caused by the same reason. 5. From the standpoint of these results, the retardation of growth, the changes of the growth direction and the morphological changes could be accepted partly, but the major effect of the chincap seems to be the rotation and the displacement of the mandible.
Chin ; Finite Element Analysis* ; Humans ; Male ; Malocclusion ; Mandible ; Maxilla ; Skeleton ; Skull Base

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The morphologic characteristics of Class I, non-extraction patients.

Young Il CHANG ; Soo Jung SHIN

Korean Journal of Orthodontics.1998;28(3):343-351.

The purpose of this study was to investigate the pretreatment and posttreatment dentofabial characteristics of non-extraction patients with Class I malocclusion. And to compare this result with matched non-orthodontic normal occlusion and Class I premolar extraction patients. Such comparison might help identify morphologic characteristics of the non-extraction patients. Initial and final cephalometric evaluation were compared in a sample of 22 patients with Class I malocclusions treated in non-extraction manner with edgewise appliance and MEAW. The mean age of the total population was 14 years 9 months and the average treatment time was 2 years 8 months. 32 landmarks were located and digitized on each cephalogram. From these landmarks, 24 linear and angular dimension were obtained Student's t-test were used to compare the pretreatment - posttreatment results, Nonextraction - Normal groups, and nonextraction - Extraction groups. Significance was predetermined at p < or = 0.05. The results were gas follows. 1. Before treatment, the mean value of the ODI was 69.9degrees, APDI was 82.1degrees, CF was 152degrees, and El was 152degrees in the non-extraction groups. 2. The skeletal pattern of the non-extraction groups were similar with non-orthodontic normal group3, but the non-extraction groups had larger interincisal angle. 3. Comparison between groups treated with and without extraction indicated at pretreatment, the extraction groups had more protrusive lips, smaller interincisal angle, and El. 4. After treatment, there was no significant changes in the skeletal pattern of the non-extraction groups, but uprighting of the maxillary and mandibular first molar and decrease of the interincisal angle were seen.
Bicuspid ; Humans ; Lip ; Malocclusion ; Molar

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A new approach to use overbite depth indicator in orthodontic diagnosis.

Won Sik YANG ; Young Il CHANG ; Tae Woo KIM

Korean Journal of Orthodontics.1992;22(1):17-30.

Since 1984, many patients have been treated with Multiloop Edgewise Archwire (MEAW) Technique and diagnosed with ODl (Overbite Depth Indicator) and APDl (Anteroposterior Dysplasia Indicator) by the authors. 234 samples of them were selected randomly for the statistical analysis (age, sex, Angle's classification, treatment period, extraction, ODI etc.). Especially, ODI was analysed statistically and its application methods were reviewed. The results and conclusions were as follows: 1. On the 150 patients with normal overbite, the mean values of Class I, II, III malocclusion were 67.5degrees, 72.2degrees and 59.0degrees. They were significantly different on the level of p<0.01. 2. In normal overbite samples, ODI decreased with the increase of APDI and the correlation coefficient was - 0.54. It seems that this result reflects the characteristics of AB to mandibular plane angle. 3. The regression equation was Y=-0.57X + 114.64, where X is APDl and Y is ODI. In cases of small or large APDI, it seems to be absurd that the patient's ODI is compared with the mean ODI to differentiate diagnostically the open bite or deep bite tendency from the normal.
Diagnosis* ; Humans ; Malocclusion ; Open Bite ; Overbite*

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Cephalometric study on the profile differences in adult Class I malocclusion relative to overbite.

Kwon Hong OH ; Dong Seok NAHM

Korean Journal of Orthodontics.2000;30(5):521-533.

This study was investigated to evaluate the morphologic characteristics of openbite and deep bite in Class I malocclusion patients and to find skeletodental factors which contributed to vertical discrepancy in Class I malocclusion. The subjects were consisted of 40 control subjects (male 20, female 20) and 40 Class I openbite patients and 40 Class I deep bite patients. Lateral cephalograms in centric occlusion were taken, traced and digitized for each subjects. The computerized statistical analysis were carried out with SPSS program. The results were as follows. 1. The pattern of vertical discrepancy in Class I malocclusion is mainly influenced by the skeletodental factors under palatal plane. 2. In openbite group, vertical discrepancy is prominent on anterior lower face and is closely related with skeletal factors such as mandibular form and inclination. 3. In deep bite group, dental factors such as curve of Spee, vertical height of maxillary molar and skeletal factor such as articular angle were contributed to the vertical discrepancy. 4. The multiple regression analysis showed that overbite in Class I molar relationship was determined mainly by dental factors such as lower incisor to occlusal plane angle, curve of Spee, interincisal angle, and ODI.
Adult* ; Dental Occlusion ; Discriminant Analysis ; Female ; Humans ; Incisor ; Malocclusion* ; Molar ; Open Bite ; Overbite*

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A longitudinal positional changes of hyoid bone in Koreans with normal occlusion.

Hyo Sang PARK

Korean Journal of Orthodontics.1996;26(6):677-689.

The positional changes of the hyoid bone over entire growth period were studied by cephalometric method in order to determine the average position and average growth changes of the hyoid bone in koreans with normal occlusion. The materials included cephalometric radiographs obtained on twenty six males and twenty two females over the period from 8.7 years to 16.7 years of age in average. The results of this study might be summarized as follows: . The mean value and standard deviation of each measurement were obtained in each age and gender. . The hyoid bone tended to positioned forwardly in female at the age of 12.7, 14.7, and 16.7 years of age as compared with male. . The hyoid bone positioned more downwardly in male than in female.
Female ; Humans ; Hyoid Bone* ; Male

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The effects of changes of mandibular position on temporomandibular joint in adult rabbits whose retrodiscal tissues were incised.

Hyeon Shik HWANG ; Byung Wha SOHN

Korean Journal of Orthodontics.1992;22(2):345-372.

The purpose of this experiment was to study the effects of changes of mandibular position on temporomandibular joint in internal derangement patients. Twenty-four female New Zealand White Rabbits, weighing over 3.5kg, were utilized in this study. Bilateral temporomandibular joint surgery was performed in twenty one of the rabbits to displace disc anteriorly through incising the retrodiscal tissue 1-2mm posterior to the disc, thus inducing internal derangement. They were divided into three groups: nine were left untreated after surgery, six were fitted with functional protrusive appliances 4 weeks after surgery, and six wore collar appliances to apply 4 ounces of mandibular retractive force per side 4 weeks after surgery. The remaining three served as the control group. Histologic examinations were performed after sacrificing them by threes at 4-week intervals. The results were as follows: 1. Histologic findings similar to internal derangement were observed in the rabbits whose retrodiscal tissues had been incised. 2. In the rabbits untreated after surgery, articular surface on condylar process and articular eminence showed severe erosion and deformation, and displaced disc manifested changes in both shape and internal architecture. 3. Functional protrusion after surgery resulted in progressive remodeling on posterosuperior portion of condyle and glenoid fossa, while it also brought about erosion on articular eminence and anterior portion of condyle. 4. Mandibular retraction after surgery resulted in compression of retrodiscal tissue and regressive remodeling of posterior portion of condyle.
Adult* ; Female ; Humans ; Rabbits* ; Temporomandibular Joint*

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Growth of mandibular condylar cartilage of the rat in vitro.

Dong Yul LEE ; Dong Seok NAHM

Korean Journal of Orthodontics.1992;22(2):309-321.

The purpose of this study was to evaluate the effect of intrinsic factor and extrinsic factor for growth of the mandibular condylar cartilage of 4 day-old rats In a serum-tree medium for 1, 4, 7,14 days. They were compared with normal growth in vivo and with growth of spheno-occipital synchondrosis in serum-free medium. The cellular kinetics of cartilages were evaluated by autoradiography of tritiated thymidine. 1. Condylar cartilage was enlarged with rounded head on day 14 of experiment while in vivo the rounded-headed shape changed into functionally flattened appearance. 2. On day 14 of experiment, a severe reduction of the proliferative zone and a considerable increase of the hypertrophic zone were observed while in normal control group endochondrol bone formation and bone marrow were observed. 3. The proliferative activity in the proliferative zone of condylar cartilage detected by 3H-thymidine incorporation was lower than that of normal control group and decreased more than that of spheno-occipital synchondrosis, but it continued during the 14 days of culture. 4. The continued maintenance of condylar cartilage and morphologic change were disturbed in this culture system, but cell division within the proliferative zone was continued and probably linked to intrinsic factor.
Animals ; Autoradiography ; Bone Marrow ; Cartilage* ; Cell Division ; Head ; Intrinsic Factor ; Kinetics ; Organ Culture Techniques ; Osteogenesis ; Rats* ; Thymidine

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Shear bond strength of rebonded ceramic brackets.

Ji Young SUNG ; Kyung Hwa KANG

Korean Journal of Orthodontics.2009;39(4):234-247. doi:10.4041/kjod.2009.39.4.234

OBJECTIVE: The purpose of this study was to evaluate the shear bond strength of rebonded ceramic brackets according to each condition and find an appropriate method to rebond ceramic brackets with proper shear bond strength in clinical practice. METHODS: The study consisted of 12 experimental groups, according to the types of brackets, debonding methods, and treatment methods of the bracket base. Shear bond strength was measured, and adhesive residues left on the tooth surface were assessed. The base of the bracket was examined under scanning electron microscopy. RESULTS: The shear bond strength of the monocrystalline ceramic bracket group was significantly higher than thatof the polycrystalline bracket group with only sandblasting (p < 0.05). There was no significant difference in shear bond strength between groups that used rebonded brackets which were debonded with shear force and debonded with laser (p > 0.05). The shear bond strength of the sandblasted/silane group was significantly higher than that of the selectively grinded group with a low-speed round bur and the sandblasted only group (p < 0.001). The retentive structure was more presented in groups where laser was applied than in groups where shear force was applied to debond brackets prior to rebonding. The bracket bases which were treated before rebonding presented smoother surfaces than new brackets. CONCLUSIONS: Shear bond strength could be increased by applying a silane coupling agent after sandblasting before rebonding. Also, the bond strength of the selectively grinded group with a low-speed round bur and the sandblasted group showed acceptable bond strength for clinical orthodontic treatment.
Adhesives ; Ceramics ; Microscopy, Electron, Scanning ; Tooth

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The effects of posterior retraction on the displacement of the maxilla.

Bo Yeong YOO ; Jong Chul KIM

Korean Journal of Orthodontics.1996;26(6):691-703.

Three-dimensional finite element model was made from adult skull to find desirable direction of retraction force to treat skeletal class II malocclusion. The retraction force of 400g was applied to the first molar. The direction of the force application was 23degrees downward, parallel, 23degrees upward and 45` upward to the occlusal plane. The stress distribution and the displacement within the maxilla were analyzed by three-dimensional finite element method. The findings obtained were as follows: 1. Maxillary first molar was displaced posteriorly and inferiorly in 23degrees downward, parallel, 23degrees upward retraction but it was displaced posteriorly and superiorly in 45degrees upward retraction. 2. ANS, A point and prosthion were moved posteriorly and inferiorly and pterygornaxillary fissure was moved posteriorly and superiorly. Clockwise rotation of maxilla occurred when retraction force was applied. 3. The degree of clockwise rotation of maxilla was greatest when the force was applied 23degrees upward to the occlusal plane and was least when the force was applied 23degrees downward to the occlusal plane. 4. Large tensile stress appeared in maxillary first molar and alveolar bone and the infraorbital region of maxilla when the force was applied 23degrees downward to the occlusal plane. Tensile stress was smaller as the direction of force move upward. 5. Large compressive stress was appeared in maxillary first molar and infraorbital region in 45degrees upward case and large compressive stress occurred in the posterior part of maxilla as the retraction force was upward.
Adult ; Dental Occlusion ; Humans ; Malocclusion ; Maxilla* ; Molar ; Skull

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