• The korean journal of orthodontics
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• v.40 no.6
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• pp.398-410
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• 2010

Objective: The purpose of this study was to investigate the changes in dentofacial morphology of non-orthodontically treated female patients with TMJ disk displacement. Methods: The sample consisted of 25 Korean female patients with bilateral TMJ disk displacement who visited the Department of Orthodontics, Seoul National University Dental Hospital from 1996 to 2006. Disk displacements were diagnosed using the magnetic resonance imaging (MRI) of both TMJs. Baseline (T1) and follow-up (T2) lateral cephalograms were analyzed. The mean age of samples at T1 was $18.1{\pm}3.5$ years (range 14.2 - 25.8 years) and at T2, $21.1{\pm}3.5$ years (range 16.2 - 28.0 years). The mean observation period was $3.0{\pm}1.9$ years. Descriptive statistics for each variable were calculated at baseline (T1) and follow-up (T2) stages, and during the observation period (T2-T1). Results: Skeletal changes were found in 64% of the non-orthodontically treated female patients with TMJ disk displacement during the observation period. The L1 to Mandibular plane distance (mm) increased significantly by 0.8 mm (p < 0.01). But there were no significant differences in the other dental relationship variables (overjet, overbite, U1 to palatal plane) during the observation period. Most patients with skeletal changes showed a backward rotation of the mandible. The ratio of the rotation was a decrease of SNB by $0.43^{\circ}$ for every $1^{\circ}$ increase of FMA (Spearman rho = -0.660, P < 0.01). A few patients showed a distal shift of the mandible without rotation or significant changes in the vertical dimension. Conclusions: During observation periods without orthodontic treatment, non-growing patients with TMJ disk displacement showed dentoskeletal changes, mainly backward rotation of the mandible.

• The korean journal of orthodontics
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• v.32 no.4 s.93
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• pp.275-291
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• 2002

Of various factors indicated for effective use of straight wire appliances, there was a great lack of studies both domestic and international about the curvatures of tooth crowns. This study was performed to investigate the labio/buccal clinical crown curvatures of Korean permanent teeth. For this study, three-dimensional laser scanning was performed on 36 dental casts with normal anatomic structures. Andrews plane and Facial axis of clinical crown (FACC) were designated as horizontal and vertical reference planes respectively. 2 or 3 lines, 1mm apart, were drawn superior, inferior, left and right of these reference planes. A three-dimensional coordinate table was made for points formed by crossing these lines, and averages of each coordinate point on the 36 dental casts were obtained. The curvature equation was made using three-dimensional coordinate points (x,y,z) and by this curvature equation, the curve ratio of each tooth was obtained. Curve ratio changes of each section of teeth were calculated by curve ratios of simplified curves. These two dimensional curves were simplified horizontally and vertically Conclusions for this study are as follows. 1. The basic data of labial and buccal clinical crown curvatures were obtained about Korean permanent teeth. 2. No significant difference was found between male and females. 3. Individual tooth characteristics 1) In maxillary central incisors, the difference in the curve ratio between the gingival and incisal sides was greater than for the other teeth. And the gingival side showed a greater curve ratio. 2) Maxillary canines showed more curvatures in the mesio-occlusal surface than the other surfaces. 3) In maxillary $1^{st}$ premolars, more curvatures were found in mesio-occlusal and disto-gingival surface, thus showing a twisted crown surface, but in maxillary $2^{nd}$ premolars, the crown curvatures of mesial and distal ends became parallel to each other. 4) No significant difference in crown curvatures was found between mandibular central and lateral incisors. 5) Occluso-gingival curvatures of mandibular$2^{nd}$ premolar turned out to be more rounded than mandibular $1^{st}$ premolars or maxillary $2^{nd}$ premolars. From the above conclusions, it can be deduced that the same bracket bases can be used for mandibular central and lateral incisors. But for maxillary $1^{st}\;and\;2^{nd}$ premolars and for mandibular $1^{st}\;and\;2^{nd}$ premolars, because crown curvatures showed significant differences, when making bracket bases there is ample reason to make bracket base curves differently for each type of tooth.

• The korean journal of orthodontics
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• v.34 no.1 s.102
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• pp.1-11
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• 2004

Predicting the arch length discrepancy by simply comparing the available arch perimeter with tooth materials is merely a 2-dimensional analysis of the teeth movement. However, the real teeth movement takes place 3-dimensionally and is affected by various factors such as, the arch fen the curve of Spee and the axis of the incisors. The purpose of this study is to clarify the relationship between the decrease in the arch perimeter and the horizontal positional change of the incisors after extraction of the 1st bicuspids, for more analytic evaluation of the arch length discrepancy at pre-treatment model analysis stage. In addition to that to evaluate the effect of the curve of Spee, teeth axis to the basal plane, and the incisional crowding to the treatment outcome. All patients were treated at the department of orthodontics, dental hospital, Yonsei university. Inclusion criteria for patients selection were as follows. $\cdot$ Angle classification I malocclusion with bialveolar protrusion $\cdot$ Extraction of 4 1st bicuspids $\cdot$ No tooth anomaly or prosthesis $\cdot$ No abnormal attrition $\cdot$ No ectopically erupted teeth $\cdot$ Angle classification I canine and molar relationship $\cdot$ Less than 3mm of crowding Model analysis of the above patients was performed and the following conclusions were obtained. 1. When the intercanine distance was maintained, the available space for the distal movement of the mandibular incisors after the extraction of the 4 1st bicuspids was larger than the space provided by the extraction of the 4 1st bicuspids. However the difference was less than 1mm. The more tapered the anterior arch form, the larger the difference. 2. Compared to the situation in which the intercanine distance was maintained, when the intercanine distance was expanded to meet the width of the Posterior teeth, the incisors could move about 3mm more distally. 3. The positional difference of the incisal tip was insignificant whether the central incisors were moved by tipping or bodily movement. 4. When the anterior crowding was solved without changing the intercanine distance, the larger the anterior arch length was, the more the anterior movement of the incisors. 5. When the curve of Spee was levelled, the increase in the arch perimeter was less than half of the deepest curve of Spee.

• The korean journal of orthodontics
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• v.27 no.2
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• pp.335-347
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• 1997

Vitamin D is known to exert its action by activating DNA and RBA within target cells to produce proteins and enzymes that can be used in bone resorption process. Particularly, the active form of vitmain D, 1,25-dihydroxycholecalciferol $[1,25-(OH)_2D_3]$, is considered to be one of the most potent stimulators of osteoclatic acitivity in vitro. The purpose of this study was to evaluate the effect of 1,25-Dihydroxyvitamin $D_3$ on the avtivity of periodotal ligament cells and, the experimental tooth movement. Human periodontal ligament cells were collected from the first premolar tooth extracted for the orthodontic treatment, and were incubated in the environment of $37^{\circ}C$, 5% $CO_2$ and 95% humidity. Microtitration(MIT) assay was done at 10, 25, 50 and 100ng/ml of 1,25-Dihydroxyvitamin $D_3$. 21 Sprague-Daft rats were divided into a control gmup(3), and experimental groups(18) where 100g of force from helical spring was applied across the maxillary incisors 1,25-Dihydroxyvitamin $D_3$ was injected into periodontal ligament at the mesial or distal surface of maxillary incisors so that we can compare the control side and the experimental side. Expreimental groups were sac rifled at 12, 24, 36, 48, 72hours and 7 days after force application, respectively. And the obtained tissues were evaluated histologically. The observed results were as follows. 1. The activity of periodontal ligament cells in l0ng/ml or 25ng/ml of 1,25-Dihydroxyvitamin $D_3$ 1,25-Dihydroxyvitamin $D_3$ was not significantly different to the control at the cultivation of 1, 2 and 3 days. 2. The activity of periodontal ligament cells was significantly increased at 3 days in 50 ng/ml of 1,25-Dihydroxyvitamin $D_3$ and 2, 3 days in 100g/ml of 1,25-Dihydroxyvitamin $D_3$. 3. Up to 7 days after force application, there was no difference in osteoblastic activity, tearing of periodontal ligament and proliferation of capillary at tension side between 1,25-Dihydroxyvitamin $D_3$ injection side and the control side. 4. The osteoclastic activity and the resorption of alveolar bone was greater in 1,25-Dihydroxyvitamin $D_3$ injection side than the control side at 36 hours after force application.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.16 no.3
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• pp.321-347
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• 1994

Muscle spindle afferents from masseter muscle were labelled by the intra-axonal HRP injection and were processed for light microscopic reconstruction. Regions containing terminal arbors scattered in the central portion of the masseteric motor neuron pool (type I a) and those restricted to 2-3 small portion of it (type II) were selected and processed for electronmicroscopic analysis with serial sections. The shape of the labelled boutons was dome or elongated shape. Scalloped or glomerulus shape with peripherial indentation containing pre or postsynaptic neuronal propiles, which is occasionally found in the trigeminal main sensory nucleus and spinal dorsal horn, was not observed. Both type Ia and type II boutons had pale axoplasm and contained clear, spherical vesicles of uniform size(dia : 49-52nm) and occasionally large dense cored vesicles(dia : 87-118nm). The synaptic vesicles were evenly distributed throughout the boutons although there was a slight tendency of vesicles to accumulate at the presynaptic site. The average of short and long diameter(short D. + long D./2) of type I a bouton was smaller than that of type II bouton. All the labelled boutons, which showed prominent postsynaptic density, large synaptic area and multiple synaptic contact, made asymmetrical synaptic contact with postsynaptic neuronal propiles. Most of the type Ia and type II boutons made synaptic contact with only one neuronal propile and boutons which shows synaptic contact or more neuronal propiles was not observed. Most of the type Ia boutons(87.2%) were presynaptic to the soma or proximal dendrite and a few remainder(12.8%) made synaptic contact with dendritic shaft or distal dendrite. In contrast, majority of type II boutons showed synaptic contact with dendritic shaft and remainder with soma or proximal dendrite. In conclusion, terminal boutons which participate in the excitatory monosynaptic jaw jerk reflex made synaptic contact with more proximal region of the neuron, and showed very simple synaptic connection, compared with those from the primary afferenst in the other region of the central nervous system such as spinal dorsal horn and trigeminal main sensory nucleus which assumed to be responsible for the mediating pain, tactile sensation, sensory processing or sensory discrimination.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.234-238
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• 2016

Purpose: Increasing use of computer aided design-computer aided manufacturing (CAD-CAM) system and number of design software made design of restoration easy and quick. Outcome of restoration has been dependent on dental technician's wax up proficiency, dentists can design restoration for themselves now. This study aims to investigate the outcome of restoration designs, according to handling skill of CAD-CAM design tool. Materials and methods: A patient's mandibular right 1st molar was prepared. After taking impression, stone model was made, scanned the stone model with 3 shape intra-oral scanner, stereolithography (STL) file was extracted. With 3shape dental designer, one dental technician with more than 5 years work experience (designer 0) and three dental technicians with less than 2years work experience (designer 1, 2, 3-group DT) and 4 1st year residents (designer 4, 5, 6, 7-group RT) designed gold crown on the same STL file. Designed crown's MD (mesio-distal) and BL (bucco-lingual) diameter, height of crown, inter-cuspal distance, number of occlusal contact points were compared. Statistical analysis was carried out, test of normality within each group, using independent t-test. Number of contact points were compared, using Wilcoxon signed-rank test. Results: There was no significant difference between group DT and group RT. Number of contact points also resulted in no significant difference. Conclusion: The outcome of each designed crowns showed no statistical differences, in values which can be expressed as numbers. Subjective factors were different. With increasing proficiency in handling designing software, fabrication of restorations according to each designer's occlusal concept can be made easy.

• The korean journal of orthodontics
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• v.29 no.2 s.73
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• pp.183-195
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• 1999

Growth and development evaluation of patients with growth potential is of great importance for orthodontic treatment planning. Timing of orthodontic intervention greatly depends on one's developmental status, thus if there is a difference in skeletal maturation among malocclusion types different treatment timing should be applied. The objective of this study was to evaluate and compare skeletal maturation among different malocclusion types. The samples used in this study was 38 Class I, 36 Class II and 33 ClassIII females aging from 8 to 10 years. Handwrist X-rays were taken with 6 month interval till 12-13 years of age. The results were as follows. 1. There was no skeletal maturity difference among different malocclusion types. 2. The hamular process of hamate was observed at $9.16{\pm}0.72$ years, pisiform bone at $9.13{\pm}0.71$ years and the ulnar sesamoid at $10.34{\pm}0.84$ years. 3. The timing of epiphyseal capping on the third finger was $10.96{\pm}0.80$ years for distal phalanx and $11.27{\pm}0.87$ years for middle phalanx, $11.12{\pm}0.85$ years for proximal phalanx of the first finger, $11.21{\pm}0.82$ years for radius and $11.62{\pm}0.85$ years for middle phalanx of the fifth finger. 4. The appearance of pisiform bone showed high correlation with appearance of hamular process of hamate(r=0.91) and ulnar sesamoid bone appearance showed high correlation with advanced ossification of hamular process(r=0.86). Timing of epiphyseal capping among different parts showed high correlation(r=0.80-0.90). 5. The shape of middle phalanx of the fifth finger showed the highest variability ($20.6\%$).

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.3
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• pp.373-384
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• 2003

The purpose of this study was to evaluate the eruption pattern of a cyst-associated mandibular premolar after marsupialization of a dentigerous cyst in children. The result from the twenty two pairs of normalized panoramic radiographs of twenty two patients who underwent neither extraction nor orthodontic traction of the cyst-associated mandibular after marsupialization were as follows. 1. The eruption speed of a cyst-associated premolar was 3.5 times faster than that of the normal contra-lateral premolar(p<0.05). The angulation change of test group was an average of $2.7^{\circ}$ per month. 2. In the change of the level of root formation, the group which had a little root maturity tended to be faster in the eruption speed(p>0.05) and the R1/4 group had a great change in the angulation change(p>0.05). 3. In the change to be with the cusp position index, the eruption speeds were increased to the 30% deviation groups. But, the eruption speed was decreased above that(p>0.05). 4. Group with cyst diminishment rate of more than $80mm^2$ per month showed the fastest eruption speed of all(p<0.05). 5. The mesial angulated teeth in the test group were decreased more rapidly than the distal angulated teeth in the eruption speed(p>0.05). But, increased in the angulation change(p<0.05). 6. There was a tendency of faster tooth eruption with less deviation of tooth axis. Group with tooth axis deviation of less than $15^{\circ}$ showed the fastest angulation change of all(p<0.05). 7. The eruption speed and the angulation change rapidly decreased during the first 6 months following marsupialization. Based on the results of this study, a cyst-associated mandibular premolar erupted more rapidly after marsupializaton. We thought so that it's prognosis was good if the tooth had a little root maturity, a little devitation and cyst lesion healed faster. We recommend that if there is enough space for eruption, orthodontic traction and surgical treatment of the cyst-associated tooth should be postponed 6 months after marsupialization.

• The korean journal of orthodontics
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• v.28 no.1 s.66
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• pp.17-27
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• 1998

Study on growth change of dental arch is considered to both an important data in orthodontic diagonsis and treatment planning as well as analysis of treatment results , also, arch form is important in anthropology and dentistry, even more so in prosthodontics and orthodontics. In the field of orthodontics, studies on the functional aspect of upper and lower teeth and maintenance of stability of dentition and occlusion were carried out from the early days. Some of the early studies include explanation of growth change in dental arch from measuring directly fom human stroll, and afterwards, cephalometrics x-rays were introduced; accordingly, studies using cephalometric measurement and linear measurements of study models were often performed. By this method, arch width, arch depth and perimeters were measured, and growth change or dental arch was studied. The subject ror this study were sn children(boys and girls or ages from 3 yens to 12 years from Kang-won district and Seoul, who has no history of orthodontic treatment and who show healthy status and normal growth and development. Cephalometric x-ray, panoramic x-ray, and study model were taken for each subject consecutively for 2 years, and the subjects are still followed up. 400 pairs of study models from the past two years were used in this study; mesio-distal diameater of each tooth, intercanine width, intermolar width, canine depth, molar depth and arch perimeters were measured. Afterwards, mean value and each standard deviation of each age group and each gender were obtained, and representation graph were drawn. The following conclusion were obtained. 1. Intercanine width showed gradual increase until the age of 10-years and after that, showed no increase. 2. Intermolar width in upper arch showed gradual increase : intermolar width in lower arch showed no significant chang, and after the age of 9-years, showed increase. 3. Cainine arch depth showed relatively rapid increase after the age of 6-years, and this pattern was more obvious in lower arch. 4. Molar arch depth increased gradually in both archs and it decrease after the age of 10-years : this phenomenon was more prominent in the lower arch. 5. Arch perimeter showed gradual inerease and convert to plateau at the age of 10-years, after that, it decreased. this pattern was more prominent in lower arch.

• The korean journal of orthodontics
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• v.30 no.2 s.79
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• pp.127-142
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• 2000

This study have been carried out to find out the mechnical effect of Multiloop Edgewise Arch Wire(MEAW) making use of the finite element method. The tip back bend of MEAW taken in this analysis is $5^{\circ},\;10{\circ}\;and\;15{\circ}$. In addition, Class II or up & down elastic is applied to find out stress distribution and their values in PDL. A adult male of normal occlusion was selected to create the models of teeth and PDL. And the model of MEAW was also created using commercial finite element code (ANSYS version 5.2). The MEAW is forcibly engaged with a class II or up & down elastic, to determine the initial stress generated in PDL. Comparing the compressive and tensile stress at each reference-planes, following results are obtained. 1. When a MEAW of $5^{\circ},\;10{\circ}\;15{\circ}$ tip back bend was engaged with Class II or up & down elastic, the distribution of compressive, tensile stress in entire PDL is similar in each case. 2. The values of compressive and tensile stress in PDL is higher in $15{\circ}$ tip back bend case than in $10{\circ}\;or\;15{\circ}$ tip back bend case. 3. In the distal PDL of 1st and 2nd molar, compressive stress appears. The compressive area is more wide and its values is higher in PDL of 2nd molar than those in 1st molar. The compressive area and its values become more wide and higher according to the increase of the tip back bend. 4. The values of compressive stress are comparatively smaIIer in PDL of molars than those in premolars. 5. Comparing class II and up & down elastic case, tensile stress values in anterior teeth PDL are smaller md their distribution is more wide in up & down elastic case than class If elastic case. On another hand, there is no difference in distribution and stress values in PDL of posterior teeth between two cases. 6. Comparing the tensile area in PDL of anterior teeth, tensile stress values are maximum in PDL of canine.