• The korean journal of orthodontics
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• v.24 no.4 s.47
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• pp.841-849
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• 1994

This study was conducted on 342 patients(male 157, female 185)aged 8 to 15 years old, who visited Dankook University Dental Hospital. Pre-orthodontic treatment orthopantomograms were used to assess the dental calcification stages of mandibular 3rd molar, 2nd molar, 2nd premolar and 1st premolar by 8 stages.(by Demirjian) Hand-wrist radiogrms were used to evaluate the skeletal maturity in 11 stages.(by Fishman) Following results were obtained after investigating the correlationship between dental calcification and skeletal maturity 1. Chronologic age showed high correlation to dental calcification and skeletal maturity. 2. Dental calcification and skeletal maturity showed high correlation and no statistical difference was observed between male and female. 3. SMI stages 1 to 4 showed high statiscal significance to mandibular 2nd molar, 2nd premolar and 1st premolar. SMI stages 5 to 8 showed high stastical significance to mandibular 2nd molar, 2nd premolar. SMI stages 9 to 11 showed high statistical significance to mandibular 3rd molar.

• The korean journal of orthodontics
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• v.20 no.2
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• pp.267-280
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• 1990

The purpose of this study was to investigate the force mechanism of Multiloop Edgewise Arch Wire and the intensity and distribution of stresses with vertical and intermaxillary elastics. The obtained results were as follows. 1. When plain wires were inserted and vertical and intermaxillary elastics were used in the upper and lower arch, the stresses of the anterior and posterior ends of wires were observed greatly but the stresses of the premolar were very small. 2. When MEAW were inserted in upper and lower arch, the upper 1st and 2nd premolar and the lower 1st premolar were extruded greatly. 3. In the area of the upper 1st molar and the lower 2nd premolar and the lower 1st molar, any stresses were not observed. 4. The vertical elastic counteracted the intrusion force of the MEAW in the anterior teeth but could not affect on posterior teeth. Using with the Class II elastics, the distal tipping force and extrusion force were exerted in the upper anterior teeth and the intrusion forces of the lower anterior teeth were relieved. Using with the Class III elastics, the extrusion force were exerted in the upper and lower anterior teeth, the distal tipping force were increased in the lower posterior teeth. 5. The Class II elastic counteracted the anterior intrusion force of the MEAW and extruded and tipped mesially the lower 2nd molar. The intrusion force of the MEAW also could not overcome the extrusion force of the class II elastics. 6. When the Class III elastics were engaged, the upper 2nd molar was extruded in spite of the intrusion forces of the MEAW and the extrusion forces of the lower anterior teeth and distal tipping forces in the posterior teeth were observed.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.10 no.1
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• pp.41-46
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• 1980

The mandibular canal must be considered carefully during the surgical treatment, especially surgical extraction of the impacted tooth and intraosseous implant, because it contains the important inferior alveolar nerve and vessels. The author investigated the curvature of the mandibular canal and its relation to the mandibular molars and positional realtion between the mental foramen and the mandibular premelors in orthopantomogram. The materials consisted of 441 orthopantomograms divided four groups; Group Ⅰ consisted of 56 males and 44 females from 1 to 6 years of age, Group Ⅱ consisted of 58 males and 45 females from 7 to 12 years of age, Group Ⅲ consisted of 65 males and 33 females from 13 to 18 years of age, Group Ⅳ consisted of 86 males and 54 females over 19 years of age. The results were as followings; 1. The curvature of mandibular canal was 144.50° in Group Ⅰ, 144. 29° in Group Ⅱ, 148.11° in Group Ⅲ, 147.33° in Group Ⅳ. 2. The curvature of mandibular canal was located most frequently on the area between mandibular 1st molar and mandibular 2nd molar in Group Ⅰ (42%) and on the mandibular 2nd molar area in Group Ⅱ (54%), Group Ⅲ (59%), Group Ⅳ (53%). 3. The position of mental foramen was most frequently below the mandibular 1st premolar in Group Ⅰ (58%), between the mandibular 1st premolar and the 2nd premolar in Group Ⅱ (62%), Group Ⅲ (47%), and below the mandibular 2nd premolar in Group Ⅳ (58%).

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.2
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• pp.409-422
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• 1995

The purpose of this study was to investigate the effects of radiation on the formation of rat molar enamel at the developmental stage. The experimental animals were divided into five groups and were irradiated single dose of 396cGy ; 1 st group on 14th day of gestation, 2nd group on 19th day of gestation, 3rd group on 3 days after birth, 4th group on 8 days after birth, 5th group on 28 days after birth. The control and 1, 2, 3, and 4th experimental groups were sacrificed on 2, 4, and 6 weeks and the 5th groups were sacrificed on 1 day and 2 weeks after irradiation. Distal 1/2 and occlusal 1/3 enamel surface of lingual side of lingual cusp, and fractured surface of lingual side of lingual cusp in a longitudinal direction of the mandibular first molar were examined using scanning electron microscope. The following results were obtained. 1. The roughness of enamel surface and enamel hypoplasia were increased in a sequence of 4th, 1st, 2nd, and 3rd experimental group, and the enamel cracks were increased in the 1st and 2nd experimental group. 2. The pattern of enamel hypoplasia had a network form on the 1st and 2nd experimental group, and appeared a linear shape on the 3rd experimental group, and then the crator-like enamel defects were observed in all experimental groups (especially 1st and 2nd experimental group) except 5th. 3. Dentinoenamel junction showed the clear-cut and straight appearance except 5th experimental group. 4. There was no significant difference between 5th experimental and control group.

• Journal of Periodontal and Implant Science
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• v.23 no.3
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• pp.635-645
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• 1993

This study was perfomed to investigate the prosthodontic and periodontal status of the abutment teeth in distally extending bridges(DEBs) (78 cases) and removable partial dentures(RPDs) (43 cases) for 122 patients (55 males and 57 females) visiting department of Periodontology, Seoul National University Hospital. The average wearing periods were 67.8 months for DEBs and 66.4 months for RPDs. 38.4% of the patients in DEBs and 35.9% in RPDs complainted of chewing discomfort and 22.6% and 24.4% were not chewing on the prosthodontically - treated sides, respectively. In DEBs, when the restoration for 2nd molar supported by 1st molar & 2nd premolar was grouped to type 1, 1st molar supported by 1st & 2nd premolars was type 2, and 1st & 2nd molars supported by 1st & 2nd premolars was type 3, there was a significant differences only in the tooth mobility score among clinical parameters (type 2>type 1>type 3). In RPDs, when bilateral free-end case was grouped to type 1, and unilateral case was type 2, there was a significant difference in the Gingival index (type 1>type 2). In DEBs, 62.8% of restoration were overcontoured, 72% had interproximal space closures, 30.5% overextended pontics and 86.6% overhanging margins. In RPDs, 24.4% of the restorations were overcontoured, 45.5% had interproxinal space closures and 58.3% overhanging margins. From these results of this study, periodontal problems caused by prosthodontic defects were considered to be contributing factors in chewing discomfort.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.26 no.2
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• pp.181-189
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• 1996

Ameloblastic odontoma is a mixed odontogenic tumor, which is characterized as being extremely rare, displaying aggressive clinical behavior, resembling a mixed radiopaque and radiolucent radiographic appearance and containing both ameloblastoma and a composite odontoma. Seven-year-old boy complaining of delayed eruption of the left lower permanent 1st molar came to the department of Oral & Maxillofacial Radiology at Chonbuk National University Hospital. The list of our radiographic differential diagnosis included the dental follicle, compound odontoma, complex odontoma and cystic odontoma. The microscopic analysis showed the lesion with the characteristics of an ameloblastic odontoma. The obtained results were as follows; 1. The area was asymptomatic, but the delayed eruption of the left lower permanent 1st molar was observed. Radiographically, well-defined widened pericoronal radiolucency containing several tooth-like radiopacities involving the impacted left lower permanent 1st molar and well-defined round radiolucency containing irregular radiopaque mass were observed. 3. Histopathologically, several tooth-like structures, odontoma components with the area of typical enamel, dentin and pulp, and ameloblastic components with typical follicular ameloblastoma were observed.

• Journal of the korean academy of Pediatric Dentistry
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• v.11 no.1
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• pp.1-6
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• 1984

The author studied the prevalence of proximal dental caries of deciduous molar by observing intraoral radiographies of 478 children aging from 2 to 5 who visited the Dep. of Pedodontics, Seoul National University Hospital. The following results were obtained; 1. The prevalence of proximal caries of deciduous molar did not show significant difference between male and female, right and left side. 2. Mandibular deciduous molar had higher prevalence than maxillary deciduous molar. 3. The prevalence was increased with age. 4. The prevalence was highest in the distal surface of lower 1st deciduous molar and lowest in the distal surface of upper 2nd deciduous molar.

• Journal of Oral Medicine and Pain
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• v.8 no.1
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• pp.121-126
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• 1983

This study is conducted with a view to make correct sexual differentiation by the utilization of discriminant functions. For that purpose were randomly sampled out 148 young adults testes, comprising 67 males and 81 females, ranging from 15 through 18 years fo age. Based on the values made available from the measurement of 6 items corresponding to the maxillary cast models, a statistical analysis was made to abstract feasible discriminant functions. The results findings are as follows: 1. The mean value by sex indicates, in all items, higher one in male group than in female group. 2. Through the measurement were defined as singnificant items in sexual differentiation the bucco-lingual dimensions of canine, 1st-molar, 2nd molar, and 1st bimolat width. 3. Derived from the value from measurement items were discriminant functions with the intention of applying them to sexual differentiation, as follows: 1) Y=-25.4112+0.7513BL3+0.3298BL4-0.2854BL5+0.7350BL6-0.3482BL7+0.2893AW (as tested by Method I) 2)Y=-25.0628+0.7737BL3+0.7468BL6-0.3885BL5+0.2951AW(as tested by Method II) BL3 : Bucco-lingual dimension of upper canine BL4 : Bucco-lingual dimension of upper first prmolar BL5 : Bucco-lingual dimension of upper second premolar BL5 : Bucco-lingual dimension of upper first molar BL6 : Bucco-lingual dimension of upper second molar AW : Upper first bimolar width 4. Sexual defferentiation in terms of descriminant functions represented a probility of 74.6%.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.675-694
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• 2000

The purpose of this study was to investigate the displacement of and the stress distribution on the prosthesis, abutment, and its supporting tissues under functional load, and the effect of alteration in root length of 2nd abutment. The 3-dimensional finite element method was used and the finite element models were prepared in which the abutments of left mandibular 5 unit axed partial denture were canine, the 1st pre-molar and the 2nd molar, and the root lengths of canines were as follows. Model I : Root length of canine was 2mm longer than the 1st premolar Model II : Root length of canine was 2mm shorter than the 1st premolar Static compressive force of 300N was applied to connector between 2nd premolar & 1st molar, and then von Mises stress, displacement and reaction force were obtained. The results were as follows : 1. In fixed partial denture, prosthesis under load on pontic was rotated around mesio-distal long axis of it from longual side to buccal, and simultaneously bended in buccal and gingival direction with mesial end deformed in gingival direction and distolingual end in occlusal. 2. Clinical crowns of abutments were bended in the same directions with those in which prosthesis deforms. Due to that, roots of anterior abutments were twisted in counterclockwise with concentration of shear stress on distal or distobuccal sides of their cervices, and that of posterior was in clockwise with concentration of shear stress on mesiobuccal side of it in the same level with anterior abutments. 3. In case that root length of the 2nd abutment was longer than that of the 1st abutment, its displacement and reaction force which means the force tooth exerts on the surrounding periodontal tissues were smaller but shear stress on itself was larger than in the case root length of 2nd abutment was shorter.

• Journal of Periodontal and Implant Science
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• v.27 no.1
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• pp.235-248
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• 1997

The purpose of this study was to investigate the width of attached gingiva of 414 subjects with healthy gingiva, or early stage of gingivitis. We compared the differences according to the tooth location, age (Yonger group : $14{\sim}30$, Older group : $31{\sim}67$) and gender. In addition, we compared the width of attached gingiva in the subjects with less than 2 sites of gingival recession($Re{\leq}2$) and the subjects with more than 3 sites of gingival recession($Re{\geq}3$) to study the relationship between the gingival recession and the width of attached gingiva. The results were as follows : 1. The width of keratinized gingiva was widest in maxillary incisors($5.3{\pm}1.4mm$) and narrowest in mandibular right 1st bicuspid and mandibular right and left 2nd molars($3.5{\pm}1.1mm$). 2. The width of attached gingiva was widest in maxillary right central incisor($3.8{\pm}1.5mm$) and narrowest in mandibular right 2nd molar($1.2{\pm}1.0mm$). 3. In the comparison between the age groups, the width of keratinized in older group was significantly (p<0.05) wider than that in younger group in maxillary right and left 1st bicuspids, mandibular right and left 1st and 2nd molars, maxillary right and left cuspids and mandibular right 1st bicuspid. There was no significant difference in the width of attached gingiva between the two groups except for maxillary right and left 1st molars and maxillary left 2nd molar. 4. In the comparison between male group and female group, in maxillary right and and left lateral incisors and cuspids, mandibular right and left cuspids and 1st bicuspids, the width of attached gingiva in female was significantly(p<0.05) wider than that in male group. 5. In the comparison between the Re 3 group and Re 2 group, there was no significant difference except for maxillary right and left 2nd molars and maxillary left 1st molar. 6. The frequency of gingival recession was m the order of mandibular right 1st bicuspid(16.6%), maxillary right 1st bicuspid(13.7%), maxillary and mandibular left 1st bicuspids (13.4%), mandibular left cuspid (10.5%), maxillary left and mandibular right cuspids(10.1%) and maxillary right cuspid(7.9%).