• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.488-495
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• 2001

Treatment of class II malocclusions require distalization of maxillary molars into class I relationship. Intraarch distal molar movement techniques have recently assumed an important role in young patients. In this study, the dental and skeletal effects of the pendulum appliance were evaluated by means of cephalometric radiographs. The samples were consisted of 19 patients: 11 females and 8 males, mean age $11.68{\pm}1.52$ years. Measurements were obtained from cephalometric prior to and the day of removal of the pendulum appliance. Treatment changes were analyzed. The following results were obtain. 1. The pendulum appliance produced $2.94{\pm}1.54mm$ distal molar movement with a mean intrusion of $1.17{\pm}0.97mm$, mean period $18.13{\pm}7.95$ weeks. 2. The anchor tooth was $1.34{\pm}1.40mm$ forward movement and $0.48{\pm}0.99mm$ extrusion, and labial tilting of incisors. 3. The angle between palatal plane and mandibular plane increased significantly. 4. There was no significant difference in according to 2nd molar position. 5. Total movement was consisted of 74% distal movement of 1st molar and 26% forward movement of the anchor tooth.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.169-179
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• 2004

The purpose of this study was to discriminate clinically and radiographically among the three groups of dentigerous cysts studied. First, Group I, involved area of dentigerous cyst was successive permanent tooth area beneath deciduous tooth. Second, Group II, involved permanent molar area, and the last, Group III involved maxillary anterior supernumerary tooth area. The author observed and compared the clinico-radiographic features of 49 cases of Group I, 36 cases of Group II, and 15 cases of Group III of dentigerous cyst and this observation and comparison had been done by based on the charts and panoramic films. The obtained results were as follows: 1. The cases of Group I were 29 cases and, those of Group II were 36 and those of Group III were 15. 2. The incidence of dentigerous cyst is high in first decade. In Group I, before first decade and early first decade was 87.8%, in Group II and Group III, was discovered more lately. 3. The frequency of dentigerous cyst is 2.5 times higher in male than in female. 4. The sequence of chief complaint was swelling(50%), routine examination(32%), and pain(9%). 5. When considering the type of the cyst, lateral type is many most in Group I (71.4%) and central type is many most in Group II (94.4%) and Group III (100%). 6. The most size of dentigerous cyst was 2 crown size in Group I, 1 crown size in Group II, above of 4 crown size in Group III. 7. Almost involved teeth showed displacement and some tooth of displaced teeth showed delayed root development and dilaceration of root. 8. The most many response of alveolar bone was buccal bone expansion in Group I (67.3%), no bone expansion in Group II(66.7%) and palatal bone expansion in Group III (60.0%). 9. The percentage of involved teeth were as follows : The mandibular third molar was 31% and many most. The mandibular second premolar was 30%. Mesiodens of maxillary anterior area was 15%. The maxillary canine was 8%. The mandibular first premolar was 5%. 10. In the Group I, causes suggesting of dentigeous cyst are pulpotomized deciduous tooth(59.2%), severe dental caries of deciduous tooth, untreated traumatic history on the deciduous tooth etc. 11. The treatment method of dentigerous was marsupialization in 61.2% of cases of Group I and that was enucleation in 61.1% of cases of Group II and in 80.0% of cases of Group III.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.1
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• pp.16-22
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• 2014

Purpose: The purpose of this study was to assess the marginal and mesial fitness of zirconia single copings and 3-unit fixed partial dentures (FPDs) manufactured with an identical model. Materials and Methods: An epoxy model in which the maxillary right 2nd premolar is lost and maxillary 1st premolar and 2nd molar are formed as abutments was manufactured and scanned by using a laser scanner. A ten units of zirconia single copings were manufactured for maxillary 1st premolar and 2nd molar, respectively and the same number of 3-unit FPDs were manufactured. For the measurements of fitness, the manufactured silicone replicas were divided into four parts and the fitness were measured by digital microscope at measurement points (P1, P2, P3, P4 and P5) of each plane. The measured gaps were classified into three categories: marginal gap (MG, P1), axial gap (AG, average of P2 and P3), occlusal gap (OG, average of P4 and P5). Results: The ranges of MG, AG and OG for single copings were 18.47 - 40.54 ${\mu}m$, 39.73 - 73.61 ${\mu}m$ and 116.90 - 134.69 ${\mu}m$, respectively. The ranges of MG, AG and OG for 3-unit FPDs were 45.95 - 87.44 ${\mu}m$, 23.78 - 57.00 ${\mu}m$ and 99.89 - 131.06 ${\mu}m$, respectively. Conclusion: The result of the study shows that the MGs for 3-unit FPDs were higher than those of single copings, though they are within the range of clinical acceptance, indicating that the use of more homogeneous zirconia block and modification of sintering processes are needed to ensure the prevention of increase of gap in 3-unit FPDs.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.4
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• pp.437-448
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• 2021

The purpose of this study is to analyze morphological characteristics of maxillary primary molar's root and root canal. 268 children aged 3 - 7 years (175 boys, 93 girls) who had CBCT (152 children) and 3D CT (116 children) taken in Seoul National University Dental Hospital from January 2006 to April 2020 were included. The number of roots and root canals were analyzed in 1002 teeth without any root resorption or periapical pathologies. Curvature, angulation, length of root and root canal, as well as cross-sectional shapes of the root canal were analyzed in 218 teeth. By using Mimics and 3-Matics software, volume, surface area, and volume ratio of root canal was analyzed in 48 teeth. More than half of maxillary primary molars have 3 roots and 3 root canals. The degree of symmetry of root canal type was about 0.63 (Cohen's kappa coefficient). The most frequent shape of roots and canals was linear in 1^st primary molars and curved in 2^nd primary molars. Angulation, length of root and root canals was the largest on palatal roots. Most teeth showed ovoid or round shapes at apex. The largest root canal volume, surface area, volume ratio was found in the palatal roots.

• The korean journal of orthodontics
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• v.30 no.5 s.82
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• pp.553-563
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• 2000

Horseshoe Expander is one of Slow Maxillary Expansion(SME) which aims to accommodate the contra- lateral expansion and midpalatal suture expansion or the palate. The appliance consists of skeleton type strew embedded in split Horseshoe appliance. It is the objectives of the presentation to manifest the changes in dental & craniofacial components subsequent to the application of Horseshoe Expander. The subjects for this study consisted of 32 patients (mean age : 12.7). frontal, lateral cephalometric headfilm were taken and study casts were fabricated before and after expansion. 24 items were measured, compared preexpansion with postexpansion. Especially, palatal volume was measured by means of 'Hydro-measurement method'. Tooth axis measurement on the dental casts were made with Universal bevel protractor, and Horseshoe Expander group were compared with RME group. This study of changes to maxillary expansion with Horseshoe Expander revealed the following significant results. 1. Triangular-shaped expansion pattern appeared in frontal cephalometric headfilm. 2. Palatal plane, occlusal plane, mandibular plane and upper incisor to FH increased in lateral cephalometrir headfilm. 3. Palatal volume increased significantly. A slight bite opening, reduction of occlusal contact points showed in dental casts. 4. A 2.2:1 ratio of the amount of intermolar width in maxilla(orthodontic movement) to maxillary width (orthopedic movement) was determined. 5. Horseshoe Expander group has less buccal tipping tendency than RME group, by taking high correlation coefficients in the upper second premolar and first molar. It was suggested that Horseshoe Expander showed less orthodontic changes, less buccal tipping tendency. In addition, it was effective in maxillary expansion.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.2
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• pp.253-261
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• 2009

The purpose of this study was to present new data on the timing and sequence of permanent teeth emergence and to compare these findings with the results of earlier studies. The dental examinations had been performed to E-elementary school students, who visited the Yonsei University Dental Hospital between 1998 and 2005; 1,307 boys and 1,312 girls with the age ranging from 6 to 12 years old. The followings were concluded. 1. Eruption time of the maxillary permanent teeth is as follows. It was 6.81 years in male and 6.73 years in female for the central incisor, 7.78 years in male and 7.65 years in female for the lateral incisor, 10.48 years in male and 9.92 years in female for the canine, 9.76 years in male and 9.63 years in female for the first premolar, 10.66 years in male and 10.49 years in female for the second premolar, 6.39 years in male and 6.26 years in female for the first permanent molar, and 12.13 years in male and 12.03 years in female for the second permanent molar. 2. Eruption time of the mandibular permanent teeth is as follows. The central incisor could not be determined in this study, but it is assumed to erupt before the age of 6.08. In the mandible, eruption time was 6.78 years in male and 6.65 years in female for the lateral incisor, 9.76 years in male and 9.05 years in female for the canine, 9.82 years in male and 9.59 years in female for the first premolar, 10.67 years in male and 10.52 years in female for the second premolar, 6.22 years in male and 6.12 years in female for the first permanent molar, and 11.58 years in male and 11.14 years in female for the second permanent molar. 3. The eruption sequence is as follows. In the maxilla, the first permanent molar erupted first, followed by the central incisor, the lateral incisor, the first premolar, the canine, the second premolar, and the second permanent molar. In the mandible, the central incisor erupted first, followed by the first permanent molar, the lateral incisor, the canine, the first premolar, the second premolar, and the second permanent molar. 4. Tooth eruption occurred earlier in female compared to male by average of 0.19 year in the maxilla and 0.29 year in the mandible. 5. In both male and female, the hiatus (interval of rest) occurred between the emergence of lateral incisor and first premolar in the maxilla while it was observed between the lateral incisor and canine in the mandible. Male had a hiatus of 1.98 years in the maxilla and 2.90 years in the mandible, while the female's were 1.98 years and 2.40 years, respectively.

• The korean journal of orthodontics
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• v.38 no.3
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• pp.175-186
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• 2008

Objective: To evaluate the discrepancies between initial STO and final STO in Class III malocclusions and to find which factors are related to the discrepancies. Methods: Twenty patients were selected for the extraction group and 20 patients for the non-extraction group. They were diagnosed as skeletal Class III and received presurgical orthodontic treatment and mandibular set-back surgery at Pusan National University Hospital. The lateral cephalograms were analyzed for initial STO (T1s) at pretreatment and final STO (T2s) after presurgical orthodontic treatment, and specified the landmarks 3s coordinates of the X and V axes. Results: Differences in hard tissue points (T1s-T2s) in the X coordinates of upper central incisor edge, upper first molar mesial end surface, lower central incisor apex, lower first molar mesial end surface and mesio-buccal cusp and Y coordinates of upper central incisor edge, upper central incisor apex, upper first molar mesio-buccal cusp were statistically significant in the extraction group. Differences in hard tissue points (T1s-T2s) in the X coordinates of upper central incisor edge, lower central incisor apex, lower first molar mesial end surface and Y coordinates of lower central incisor apex were statistically significant in the non-extraction group. In the extraction group, the upper arch length discrepancy (UALD) had a statistically significant effect on maxillary incisor and first molar estimation. Lower arch length discrepancy and IMPA had statistically significant effects on mandibular incisor estimation in both groups. Conclusions: Discrepancies between initial STO and final STO and factors contributing to the accuracy of initial STO must be considered in treatment planning of Class III surgical patients to increase the accuracy of prediction.

• The korean journal of orthodontics
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• v.31 no.1 s.84
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• pp.25-38
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• 2001

The purpose of this study was to compare the force, the displacement and the stress distribution on the maxillary first molars altered by the application of various asymmetric head-gear. For this study, the finite element models of unilateral Cl II maxillary dental arch was made. Also, the finite element models of asymmetric face-bow was made. Three types of asymmetric face-bow were made : each of the right side 15mm, 25mm and 35mm shorter than the left side. We compared the forces, the displacement and the distribution of stress that were generated by application of various asymmetric head-gear, The results were as follows. 1. The total forces that both maxillary first molars received were similar in all groups. But the forces that mesially positioned tooth received were increased as the length of the outer-bow shortened, and the forces that normally positioned tooth received were decreased as the length of the outer-bow shortened. 2. In lateral force comparison, the buccal forces that normally positioned tooth received were increased as the length of the outer-bow shortened, and the buccal fortes that mesially positioned tooth received were decreased as the length of the outer-bow shortened. Though the net lateral force moved to the buccal side of normally positioned tooth as the length of the outer-bow shortened, both maxillary first molars received the buccal force. That showed 'Avchiai Expansion Effect' 3. The distal forces, the extrusion forces and the magnitudes of the crown distal tipping that mesially positioned tooth received were increased as the length of the outer-bow shortened, and the forces that normally positioned tooth received were decreased as the length of the outer-bow was shortened. 4. The magnitude of the distal-in rotation that normally positioned tooth received were increased as the length of the outer-bow was shortened. But, mesially positioned tooth show two different results. For the outer-bow 15mm shortened, mesially positioned tooth showed the distal-in rotation, hut for the outer-bow 25mm and 35mn shortened, mesially positioned tooth showed the distal-out rotation. Thus, the turning point exists between 15mm and 25mm. 5. This study of the initial stress distribution of the periodontal ligament at slightly inferior of the furcation area revealed that the compressive stress in the distobuccal root of the normally positioned tooth moved from the palatal side to the distal side and the buccal side successively as the length of the outer-bow shortened. 6. This study of the initial stress distribution of the periodontal ligament at slightly inferior of the furcation area revealed that the magnitudes of stress were altered but the total stress distributions were not altered in the mesiobuccal root and the palatal root of normally positioned tooth, and also three roots of mesially positioned tooth as the length of the outer-bow shortened.

• Imaging Science in Dentistry
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• v.32 no.3
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• pp.167-173
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• 2002

Purpose : To evaluate clinical and radiographic differential diagnosis between ameloblastoma and odontogenic keratocyst (OKC) using clinical data, plain radiographs, and CT. Materials and Methods: 25 cases of ameloblastoma and 44 cases of OKC diagnosed in biopsy, were selected from the files stored in Department of Oral and Maxillofacial Radiology, Seoul National University Dental Hospital from 1999 to 2001, and evaluated using following criteria: sex and age, location, shape, border to normal bone tissue, effect to adjacent tissues, homogeneity in the lumen of the lesion, response of the cortical bone, long-to-short length (LIS) ratio of the lesion, and expansion angle of the cortex. Results: Ameloblastoma and OKC were seen most frequently in third decades and no statistical significance was noted between both sexes. Ameloblastoma occurred most frequently in mandibular angle and ramus area (68%) and OKC at the maxillary molar (34.1 %), and mandibular angle and ramus area (43.2%). The root resorption of the adjacent teeth, mandibular canal displacement, and the impaction of teeth were seen more frequently in ameloblastoma than in OKC. The LIS ratio measured in CT was largest in maxillary OKC cases, followed by mandibular ameloblastoma, and mandibular OKC (1.2, 1.8 and 2.4 respectively). The expansion angle of the cortex shows a statistically significant difference between ameloblastoma (48.8°) and OKC (31.5°). Conclusion : The numeric morphology (LIS ratio) and expansion angle of the cortical bone of the lesion measured in computed tomography can be used to differentiate the ameloblastoma and odontogenic keratocyst.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.248-261
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• 1999

In order to define a current set of Korean children norm with mixed dentition, following study was done. The subjects were 102 healthy dentition contestants(48boys, 54girls). Standardized lateral head roentgenograms were taken, and Ricketts analysis was done. Results were as follows: 1. Length of anterior cranial base, posterior facial height, corpus length were longer in male than in female(p<0.05), and Porion was located posteriorly in male than in female(p<0.01). 2. Through facial depth, Pogonion of male was more forwardly positioned(p<0.05), mandible was significantly steeper in female, and maxillary anterior teeth were significantly tipped forward in male(p<0.05). 3. Variables such as length of anterior cranial base, upper molar position(p<0.01) and corpus length(p<0.05) were significantly changed by age. 4. Maxillary height, facial depth, mandibular plane angle, convexity were changed by age, but not significantly(p>0.05).