• Imaging Science in Dentistry
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• 제39권2호
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• pp.89-92
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• 2009

Purpose: To assess the angle between mandibular canal and occlusal plane at each posterior tooth region and location of mental foramen on the panoramic radiographs. Materials and Methods: This study analysed 46 half-mandibles of panoramic radiographs. Inferior border of mandibular canal was traced. Occlusal plane was drawn from lingual cusp tip of the first premolar to distolingual cusp tip of the second molar. Perpendicular line from occlusal plane was drawn at each tooth region and then tangential lines were drawn from the crossing points at canal. the angle between occlusal plane and tangential line was measured. The location of mental foramen was also studied. According to the location of mental foramen, radiographs were divided into M (mesial) group and D (distal) group on the basis of the second premolar. and then inter-group analysis about mandibular canal angle was done. Results: The angles of mandibular canals were -17.7$^{\circ}$, -9.5$^{\circ}$, 8.2$^{\circ}$, 22.3$^{\circ}$, and 39.2$^{\circ}$at first premolar, second premolar, first molar, second molar, and third molar, respectively. The commonest position of the mental foramen was distal to the second premolar. Inter-group comparison showed statistically significant difference at the second premolar and the first molar(p<0.001). Conclusion: The knowledge of mandibular canal angle and location of mental foramen can help understanding the course of mandibular canal. (Korean J Oral Maxillofac Radiol 2009; 39: 89-92)

• 대한소아치과학회지
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• 제6권1호
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• pp.43-52
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• 1979

The purpose of this study was to finding out the relationship between the tooth calcification and eruption of the mandibular permanent teeth in Korean. This study was undertaken in 592 children at ages from 3 to 13 years who had good oral condition by means of panoramic roentgenographic analysis. The following results were obtained. 1. The mean ages of crown completion were as follows; Canine 1st. Premolar 2nd. Premolar 1st. Molar Male 6yrs. 4mos. 6yrs. 8mos. 7yrs. 6mos. 7yrs. 6mos. Female 5yrs. 11mos. 6yrs. 5mos. 7yrs. 2mos. 3yrs. 3mos. 2. Each tooth started to move toward occlusion at approximately stage 6 or after crown completion. 3. The highest increment in eruption rate was at about 1/3~1/2 completion of root and ages at 10-11 years in male, 9-10 years in female. 4. Eruption period of both sexes were as follows; Canine: 6-12years 1st. Premolar: 7-12 years 2nd. Premolar: 7-13 years 1st. Molar: 3-7 years 5. The eruption was completed before the root completion. 6. The sequence of eruption and calcification was 1st. Molar-Canine-1st. Premolar-2nd. Premolar in both sexes.

• 대한소아치과학회지
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• 제30권3호
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• pp.495-501
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• 2003

매복은 임상적 또는 방사선학적으로 인식할 만한 맹출로의 장애물이나 잘못된 치배의 위치로 인하여 치아의 맹출에 진전이 없는 것을 말한다. 제 3 대구치와 상악 견치를 제외하고 제 2 소구치에서 가장 흔히 매복이 발생하며, 소구치의 매복은 전체 매복의 0.5%를 차지한다. 소구치 매복의 치료에는 교정적 견인과 외과적 재위치가 필요할 수도 있지만, 만기 잔존된 유구치에 의해 발생한 소구치 매복은 유구치의 발거 및 공간 유지로서 소구치의 맹출을 유도할 수 있다. 본 증례는 제 2 소구치의 미맹출을 주소로 경북대학교병원 소아치과에 내원한 환아에서 만기 잔존된 제 2 유구치를 발거하고 공간 유지를 하여 제 2 소구치의 자발적 맹출을 시도하였는 바 다음과 같은 결과를 얻을 수 있었다. 1. 만기 잔존된 제 2 유구치와 연관된 매복된 제 2 소구치는 유치 발거를 통한 최소한의 치료로 양호한 결과를 얻을 수 있다. 2. 제 2 소구치가 맹출할 때까지 적절한 공간 유지와 정기적인 방사선 검사가 필요하다. 3. 교정적 견인 또는 외과적 재위치를 시도하기 전 치아의 이동을 확인하기 위한 충분한 시간이 허용되어야 한다. 4. 치근이 미완성된 치아에서 좀 더 성공적인 결과를 얻을 수 있다.

• Journal of Periodontal and Implant Science
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• 제31권1호
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• pp.243-258
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• 2001

Gingival recession is exposure of the root surface with apical shift in the position of gingiva. The incidence of gingival recession is 8% in children and 100% after the age of 50. Recession tends to be found in patients with healthy gingiva, but more frequentely found in patients with periodontal disease, and it often causes mucogingival defects. Buccal surface of premolar is the area not only for severe gingival recession and cervical abrasion, but also the area of numbers of buccal frenum and less keratinized gingiva. Threrfore, the goal of this study was to observe the patients with periodontitis and examine whether there are clinical relations between gingival recession and cervical abrasion of premolar and other factors related with the condition of periodontal health. Generally healthy 218 patients who had periodontitis, aged between 18 and 78, were examined for depth of periodontal poket, width of attached gingival, gingival recession, cervical abrasion, and frenum of mid-buccal surface of premolar at the Department of Periodontics in Dankook University Dental Hospital and following is the result. 1. The average gingival recession and cervical abrasion of premolar with periodontal disease was 0.76mm and 0.29mm and each has 43% and 14% of incidence. Also the width of attached gingiva of mid-buccal surface was 1.77mm. the average periodontal pocket depth is 2.0mm and 47% of frequently seen was narrow single shaped frenum, and the interdistance of the frenum was mostly over 4mm. 2. With statistical significance(P<0.05), the incidence of gingival recession increased with age and was related much more with female than male, the first premolar than the second premolar, and with narrow attached gingiva and frenum. 3. With statistical significance(p<0.05), the incidence of cervical abrasion increased with age and was related with the area of the first premolar and narrow attached gingiva, but the sexual and frenum differences were not statistically significant (p>0.05). 4. The severity of gingival recession increased with age and was more related with female than male, the first premolar than the second premolar. And the area of narrow attached gingiva and frenum showed more gingival recession and the distance of frenum was more highly related than shape, and they were statistically significant (p<0.05). 5. With statistical significance(p<0.05), the severity of cervical abrasion increase with age and was observed at the first premolar and narrow attached gingiva. But the sexual and frenum differences were not statistically significant (p>0.05).

• Journal of Oral Medicine and Pain
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• 제6권1호
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• pp.23-34
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• 1981

In order to evaluate the correlation of age with development stage on permanent lower posterior teeth. the author exmined the roentgeregrams in standard films taken by intraoral technic and analysed the development phases of 1358 teeth of 500 males ranging from 9 to 15 years. The development was divided into 7 phases : Crown complete (Cr. C.). Root length 1/4(R. 1/4) Root length /2 (R. 1/2) Apical closure complete (A.C) The obtained results were as follows : 1. The formation of roots in full length on posterior teeth was complete as follow : a. Roots of 1st premolar : 12.72 years b. Roots of 2nd premolar : 12.94 years c. Meral Roots of 2nd molar : 13.38 years d. Distal Roots of 2nd molar : 13.46 years 2. The formation of apical forman of premolar was closured as follows : a. Apical foramen of root of 1st premolar : 13.64 years b. Apical foramen of root of 2nd premolar : 13.93 years 3. As a general rule. the mesial roots of second molar were developed earlier than distal roots of second molar. 4. In the correlation of age with the development stage, the regression equations. the correlation coefficents. and the sample numbers were “Y = 0.8370x + 10.2160, r = 0.71(p<0.01), n = 318”on lower first premolar, “Y = 0.6984x + 10.2148, r = 0.71(p<0.01), n = 385”on lower second premolar, “Y = 0.8810x + 10.2040, r = 0.65(p<0.01), n = 344”on mesial Root of lower second molar, and “Y = 0.7310x + 10.7940, r = 0.66(p<0.01), n = 311”on Distal Root of lower second molar respectively.

• 대한치과교정학회지
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• 제35권5호
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• pp.371-380
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• 2005

제1소구치 또는 제2소구치 발치 후 발치공간 폐쇄 시 치아이동의 양상 즉, 치아이동방향과 이동량을 구명하는 것이 본 연구의 목적이었다. 상악 우측 인공 치조골부에 제1소구치 또는 제2소구치를 제외한 중절치부터 제2대구치 까지 실험용 치아들을 식립하고 bull loop이 형성된 반쪽 호선에 15도의 gable bend를 부여한 후 전치부를 후방견인하여 발츠공간을 폐쇄시켰다. 실험 전후에 교합면 방사선사진과 시상면 방사선사진을 촬영하고 인공치조골부 하단에 식립된 기준표지점에 중첩하여 이동방향 및 이동량을 계측하였다. 그 결과 제2소구치 발치군의 전치부후방이동량이 제1소구치 발치군에 비해 더 적었으며 구치부의 고정원 소실 및 고정원의 근심설측회전량은 제2소구치 발치군에서 더 크게 나타났다.

• 대한치과교정학회지
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• 제24권2호
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• pp.479-508
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• 1994

This study was designed to investigate the reciprocal movement which was derived form application of active torque in ideal archwire by computer-aided three-dimensional finite element analysis of maxillary teeth and surrounding periodontal ligament composed of 2617 elements and 3725 nodes. Ideal archwire model was also made using the beam elements and the contact between the wire and the bracket slot was made using the gap element. In this study non-linear elastic behaviors of contact between the wire and the bracket slot were considered on. We put the active torque between the lateral and cenral incisor and between the second premolar and the first molar with/without cinch-back. The results were expressed by quantitative and visible ways. The findings of this study were as follows: 1. Reciprocal actions to active torque were complex system consisting of a combination of counter-torque, bucco-lingual linear displacement and tipping, rotation of the teeth, occluso-gingival linear displacement. 2. When active anterior crown labial torque was applied, crown labial tippings of the lateral were the greatest, and those of the central incisor was the next, Crown lingual tippings of the canine and the first premolar, mesial rotations and extrusion of the lateral and distal rotations and intrusion of the canine occurred. When anterior torque with the cinch-back was applied, amount of crown labial tippings of the lateral and central incisor were reduced. Amount of crown lingual tipping of the canine and the first premolar were increased. Mesial tippings and mesial rotations of the second molar occurred. 3. When active posterior crown lingual torque was applied, crown lingual tippings of the first moalr were the greatest, and crown labial tippings of the second premolar and the first premolar were the next, the crown lingual tipping of the second molar were a little. Mesial rotations of the second premolar occurred but those of the first premolar didn't occurred.

• 대한치과보철학회지
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• 제37권2호
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• pp.185-199
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• 1999

This study was peformed to investigate the distribution and magnitude of stress at supporting tissue of abutment teeth and residual ridge tissue with remaining unilateral posterior teeth. Four types of removable partial dentures that included clasp retained removable partial denture, attachment retained removable partial denture, telescopic removable partial denture, and swing-lock partial denture were designed, and strain gauge was used for stress analysis. Each prosthesis was subjected to simulated vertical and oblique load. The following conclusions were drawn from this study. 1. The clasp retained removable partial denture generally distributed simulated vertical force more evenly to the supporting structure. 2. The stress at buccal side of 1st premolar was the lowest in swing-lock partial denture and that was highest in attchment retained removable partial denture. The stress at lingual side of 1st premolar was the lowest in telescopic partial denture. 3. In clasp retained removable partial denture, stress was lower at load site and ridge crest at mid-line, but it was higher at 1st premolar area on vertical load. 4. In attachment removable partial denture, stresses at buccal side of 1st premolar. lingual side of 1st premolar on vertical load, and ridge crest at midline on oblique load were higher. 5. In telescopic removable partial denture, stress at lingual side of 1st premolar was the least in all removable partial dentures, but the stress at load site was higher. 6. In swing-lock removable partial denture, stress at buccal side of 1st premolar was the lowest, and stresses at load site and distal end of residual ridge crest were higher.

• 대한소아치과학회지
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• 제7권1호
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• pp.33-40
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• 1980

The author observed the eruption pattern of the mandibular premolars. For this study the author took 406 cases of oblique cephalographs of 6 to 12 year old children. The measurement were with regard to the vertical and horizontal dimensional changes and tooth axis changes to the occlusal plane. The following results were obtained. 1. At stage V the tooth axis of 1st premolar inclined mesially to the occlusal plane, as the tooth erupt toward vertically the angulation changed that at stage X the tooth axis almost right angle to the occlusal plane. 2. The distance from the root apex of premolars to the lower border of mandible were slightly increased to the stage VII, while after stage VII rapid increasing appeared. At stage X the distance of 1st premolar was more longer than 2nd premolar. 3. The distance from the mesial surface of 1st molar to the mesial surface of premolars were decreased slightly to the stage VII, but this distances were decreased rapidly after stage VII. 4. The distance between distal surface of 1st premolar and mesial surface of 2nd premolar was almost constant before stage VIII, at stage IX this distance was little presented because the premolars were contacted.

• 대한치과교정학회지
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• 제24권4호
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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.