• Journal of Oral Medicine and Pain
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• v.16 no.1
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• pp.73-84
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• 1991

저자는 연령을 추정하기 위한 기본자료를 얻기 위하여 상하악의 대구치, 소구치의 발육정도를 평가하였다. Orthopantomograph를 촬영한 722명의 3,464개 치아를 대상으로 crown-root ratio를 측정하여 발육정도를 평가하였으며, 다음과 같은 결론을 얻었다. 1. 완전히 형성된 치아의 crown-root ration에는 남녀간에 유의한 차이가 없었다. 2. 발육중인 치아의 crown-root ratio에는 좌우측간에 유의한 차이가 없었다. 3. 각 치아의 crown-root ratio를 이용한 연령추정의 회귀방정식은 다음과 같다. 남자: 여자 : 하악좌측 제 2대구치 : Y=4.599X+7.832(r=0.8337) 하악 좌측 제 2대구치 : Y=4.857X+7.429(r=0.8975) 제 1대구치 : Y=5.179X+2.324(r=0.7948) 제 1대구치 : Y=5.919X+2.018(r=0.8144) 제 2소구치 : Y=3.863X+7.432(r=0.8638) 제 2소구치 : Y=3.679X+7.275(r=0.8819) 제 1소구치 : Y=3.472X+7.120(r=0.8352) 제 1소구치 : Y=4.001X+6.544(r=0.9024) 하악우측 제 2대구치 : Y=4.447X+7.938(r=0.8045) 하악 우측 제 2대구치 : Y=4.653X+7.365(r=0.8598) 제 1대구치 : Y=5.954X+1.495(r=0.7777) 제 1대구치 : Y=5.449X+2.012(r=0.7553) 제 2소구치 : Y=3.894X+7.253(r=0.8689) 제 2소구치 : Y=3.772X+7.025(r=0.8719) 제 1소구치 : Y=4.189X+6.717(r=0.8370) 제 1소구치 : Y=4.327X+6.193(r=0.8524) 상악좌측 제 2대구치 : Y=4.430X+7.722(r=0.7538) 상악 좌측 제 2대구치 : Y=4.876X+7.606(r=0.8311) 제 1대구치 : Y=4.645X+2.886(r=0.6894) 제 1대구치 : Y=6.754X+1.891(r=0.5378) 제 2소구치 : Y=4.391X+6.686(r=0.7700) 제 2소구치 : Y=1.245X+10.575(r=0.1908) 제 1소구치 : Y=5.564X+6.037(r=0.9032) 제 1소구치 : - 상악우측 제 2대구치 : Y=4.587X+7.966(r=0.7882) 상악 우측 제 2대구치 : Y=4.454X+7.803(r=0.8443) 제 1대구치 : Y=4.047X+4.124(r=0.6352) 제 1대구치 : Y=6.336X+2.911(r=0.4688) 제 2소구치 : Y=2.920X+8.089(r=0.7277) 제 2소구치 : Y=3.105X+8.082(r=0.6381) 제 1소구치 : Y=3.264X+6.970(r=0.7292) 제 1소구치 : - 4. Orthopantomograph상의 crown-root ratio를 이용한 연령의 추정에는 상악치아들 보다 하악치아들이 더 정확하게 사용될 수 있다.

• Journal of dental hygiene science
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• v.7 no.4
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• pp.275-279
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• 2007

The purpose of this research, which was executed with 200 patients whose chief complaint was the extraction of the mandibular third molar, was to examine the effect that eruption state of the mandibular third molar has on the growth of pericoronitis. The conclusion about distribution of left and right mandibular third molar, angulation, impaction degree, anterior border of mandibular ramus and the interval from mandibular second molar to mandibular third molar was drawn by chi-square test. 1. There was correlation between pericoronitis and position of the mandibular third molar according to age. 2. In angulation of mandibular third molar, mandibular third molar most likely to be afflicted with pericoronitis is mesioangular. 3. The impaction degree between mandibular third molar and the growth of pericoronitis was given in the order of Level a, Level c and Level b. 4. In the anterior border of mandibular ramus with mandibular third molar, pericoronitis was easily generated in the order of Class II, Class I and Class III. 5. The shorter the interval from distal cementoenamel junction of mandibular second molar to mesial cementoenamel junction of third molar became, the more easily pericoronitis was generated.

• The Journal of the Korea Contents Association
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• v.10 no.7
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• pp.285-296
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• 2010

This study was implemented among 100 students of C College of Public Health who have healthy permanent dentition in order to measure the morphology and sizes of clinical crowns of permanent maxillary molars. The following are conclusions of this study. 1. The cusp height, crown width, crown thickness of clinical crowns appeared to be bilaterally symmetrical. 2. The strong development of the buccal groove showed to be superior in the right first molar. The appearance rate of the buccal pit was high in the right first molar also. 3. The type 4th cusp appeared as 100% in the left and right first molars, and 78%, 75% in the left and right second molars respectively. 4. The distal lingual cusp(DLC) size were bilaterally symmetrical in the type 4th cusp. 5. As for the distance between two cusp tips, it was large between mesial cusp tips in all of the first and second molars at both sides. 6. Development of the Carabelli's cusp was high in both the left and right first molars. 7. The appearance rate of the oblique ridge was 87.0% in the right first molar, 73.0% in the right second molar, 88.0% in the left first molar, and 73.0% in the left second molar. This is considered to be caused by people who have mild dental crown caries in their first molars. 8. The appearance rate of the mesial marginal ridge tubercle(DMRT) was high in both of the left and right first molars. That of the distal tubercle was 16.0% in the right first molar, 26.0% in the right second molar, 14.0% in the left first molar, and 21% in the left second molar.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.1
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• pp.25-33
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• 2017

The lower $2^{nd}$ molar eruption is beginning to mesiolingually, then rotate to distobuccally so it has a tendency to be tilted and impacted mesially. Signs and symptoms of impacted $2^{nd}$ molar are similar to impacted $3^{rd}$ molar's. However, treatment plan for impacted $2^{nd}$ molar is different from that of impacted $3^{rd}$'s. The former is the preservation and uprighting of $2^{nd}$ molar so that it could act to recovery of mastication, symmetrical facial growth, maintaining the symmetry of dental arch, stable occlusion, while the latter is the extraction of tooth. If the uprighting treatment is planned, most proper protocol of treatment and the additional treatment opition should be applied with consideration for it's crown exposure, present of $3^{rd}$ molar which interrupt the uprighting process, extrusion of opposite tooth. Although it could not improve the esthetic result, it could prevent many dental problems. Therefore, uprighting for impacted lower $2^{nd}$ molar is meaningful treatment.

• The korean journal of orthodontics
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• v.34 no.5 s.106
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• pp.394-407
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• 2004

The Purpose of this study was to evaluate the effect of the lower third molar on treatment time and distal en masse movement of the lower dentition in Giass III malocclusions. Thirty subjects (9 males and 27 females) were selected, all of whom were diagnosed as Glass III malocclusion and treated by fixed appliances without premolar and/or molar extraction. They were divided into three groups Group 1 consisted of 12 subjects. whose lower third molars were not extracted during the whole orthodontic treatment. Group 2 consisted of 8 subjects. whose lower third molars were extracted after WEAW application and before removal of the orthodontic appliances. Group 3 consisted of 10 subjects whose lower third molars were extracted before MEAW application. For each subject. overall treatment time and duration of MEAW application were determined. In addition. pre-treatment and post-treatment lateral cephalometric radiographs were analyzed. All data were Processed statistically with ANOVA, and the conclusions were as follows: There was no significant difference among the groups in overall treatment time However, duration of MEAW application was longer in Group 2 than in Group 1 or Group 3. The overjet that was established after orthodontic treatment was largest in Group 3, in which the lower third molars were extracted befor MEAW application. After orthodontic treatment, IMPA decreased in Group 3. but increased in Group 1 and Group 2. There was no significant difference among the three groups in the translation of lower second molars However the tipping movement of lower second molars was significantly different, highest in Group 2 and lowest in Group 1 Therefore. it is thought to be better for the orthodontic treatment of Class III malocclusions to extract the lower third molars before MEAW application. In Group 2, the mandibular plane angle was decreased as a result of forward rotation of the mandible This skeletal change was thought to bring about the difficulty of treatment.

• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.299-310
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• 1995

The purpose of this study is to know about the positional change of second molar when orthodontic treatment is performed. To know about it, we andlysed cephalogram pre. and post treatment for 54 adult patients who werefinished orthodontic treatment by banding to the first molar and classify them into 4 groups Class I extraction group 15, Class I nonextraction group 12, Class II group 13, class Class III group 14. The following conclusions were obtained : 1. In the extraction group of Class I , mandibular second molar showed less extrusion and mon distal inclination than first moarl. But maxillary second molar showed more or less extrusive and mesial inclination to much the same degree of first molar. 2. Inthe non-extractio group of Class I, mandibular second molar in intrusive to first molar, it showed smilar distal inclination to first molar. But maxillary second molar is extrusive similarly to first molar. 3. In the group of Class II , mandibular second molar is less extrusive than first molar and maxillary second molar is more extrusive than first molar. 4. In the group of Class III, mandibular second molar showed similar extrusion to first molar and more distal inclination than first molar. But maxillary second molar showed less extrusion than first molar. 5. A comparision of the positional change of second molar among groups : The change of distance from FH plane to funcation point of maxillary second molar is the difference between Class I extraction group and Class II group, Class I extraction group and Class III group. The change of maxillary second molar to palatal plane and occlusal plane is the difference between Class I extraction group and Class III group. And the change of distance from mandibular plan to furcation point of mandibular second molar is difference between Class I extraction group and non-extraction group, Class I non-extraction group and Class II group, Class I non-extraction group and Class III group. But the change of angle of mandibular second molar to mandibular plane and occlusal plane is make no difference in among groups.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.4
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• pp.540-548
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• 2000

The aim of this study was to evaluate the timing of sequence of tooth calcification in current Korean growing children. The Calcification stage of permanent teeth of Korean children was investigated by classifying them into 10 stages by the criteria of Nolla, using the panoramic radiographs of 258 healthy Korean children, 149 males and 109 females, between the ages of 4 years and 13 years, with normal growing tendency and no orthodontic treatment experience. The obtained results were as follows: 1. Timing of calcification of permanent teeth by Nolla stage was established with mean values. Among the mean value, results of Nolla stage 7 were as follows: Calcification timing of male in the maxilla was 6 year 9 month on central incisor, 7 year 4 month on lateral incisor,7 year 9 month on canine, 8 year 8 month on the first premolar, 9 year 4 month on the second premolar, 6 years 3 month on the first molar and 10 year 8 month on the second molar, calcification timing of male in the mandible was 5 year 11 month on central incisor, 6 year 4 month on lateral incisor, 7 year 5 month on canine, 8 year 1 month on the first premolar, 8 year 6 month on the second premolar 5 years 6 month on the first molar and 10 year 3 month on the second molar. Calcification timing of female in the maxilla was 6 year 2 month on central incisor, 6 year 7 month on lateral incisor, 6 year 11 month on canine, 8 year 1 month on the first premolar, 8 year 5 month on the second premolar, 5 years 10 month on the first molar and 9 year 10 month on the second molar, calcification timing of male in the mandible was 5 year 6 month on central incisor, 5 year 9 month on lateral incisor, 6 year 8 month on canine, 7 year 6 month on the first premolar, 8 year 4 month on the second premolar, 5 years 3 month on the first molar and 9 year 7 month on the second molar. 2. The sequence of calcification at Nolla stage 7 was in consequence to the first molar, central incisor, lateral incisor, canine, the first premolar, the second premolar and second molar. 3. While the sequence of root completion of maxilla was in consequence to the first molar, central incisor, lateral incisor, that of mandible was in order of central incisor, first molar and lateral incisor. 4 the calcification timing of permanent teeth was earlier in female than in male (p<0.05). According to above data, the result of this study is applicable for diagnosis and routine clinical practice for children.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.4
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• pp.373-384
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• 2023

This study aims to confirm the average chronologic age according to the developmental stages of the mandibular canine (L3), first and second premolars (L4, L5), and second and third molars (L7, L8) in children and adolescents, and to confirm the developmental stage of L3, L4, L5, and L7, which can estimate the development of L8. A total of 1,956 digital panoramic radiographs of healthy individuals aged between 6 and 15 years who visited Seoul National University Dental Hospital from January 2019 to December 2020 were selected. The developmental stages of L3, L4, L5, L7, and L8 on both sides were evaluated using the dental maturity scoring system proposed by Demirjian and Goldstein. The average age at which the follicle of L8 was first observed was around 9.34 ± 1.35 years and varied from 6 to 12 years. The possibility of agenesis of L8 was high when no traces of L8 were observed after the following stages: L3, L4, and L5 at the developmental stage F and L7 at the developmental stage E; the age was about 10 years. In estimating the development of L8, when only one tooth was considered, estimation accuracy with L5 was the highest, and there was no significant difference when all four teeth were included. This study showed the age distribution according to the developmental stages of L3, L4, L5, L7, and L8 in children and adolescents and confirmed the developmental stages of L3, L4, L5, and L7, which can be used to estimate the development of L8.

• The Journal of the Korean dental association
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• v.26 no.10 s.233
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• pp.898-902
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• 1988

완전히 발육된 하악 제3대구치가 매복되어 있거나 또는 부분적으로 맹출된 상태일때는 임상증상을 일으키기 전에 발치하는 것이 치관주위염이나 이로 인한 합병증 및 치주질환 등을 예방할 수 있느느 가장 좋은 방법이며 이미 임상 증상을 유발한 매복 하악 제 3대구치는 대부분 재발방지를 위하여 발거하게 된다. 성공적인 발치의 기준을 1) 치아의 완전한 발치 2) 인접조직에 대한 최소한의 외과적 손상 3) 술후 합병증의 극소화 4) 가능한한 시술 시간의 단축 등이라 할때 매복 하악제 3대구치의 성공적인 발거를 위하여는 발치의 기본 원칙을 숙지하여야 함은 물론이며 더욱 면밀한 술전 평가와 외과적 발치술 시 필요한 기구의 완비 등이 필수적이라 할 것이다.

• Journal of dental hygiene science
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• v.7 no.4
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• pp.207-211
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• 2007

Many studies reported that the presence of cervical enamel projection (CEP) in cemento-enamel junction(CEJ) is greatly related to periodontal disease. The aim of this study was to investigate the prevalence of enamel projections in buccal, mesial, distal and lingual(palatal) surface of maxillary and mandibular first and second molars on extracted teeth. Among 660 teeth extracted due to the periodontal disease and dental caries in Seoul National University Dental Hospital was examined, 530 teeth which has distinct CEJ were examined with 8 times x electronic magnifier by one examiner. The prevalence of CEP for maxillary teeth (45.49%) was higher than that of mandible (39.62%). The first molar (45.22%) had more CEP than second (39.89%). Furthermore, buccal surface had highest incidence of CEP than other surfaces. The results of this study imply that the clinicians should take good care of the prevalence of CEP when scaling or root planning, plaque control instruction and periodontal surgery.