• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.1
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• pp.167-174
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• 2008

Mandibular first molar and primary molars usually have two roots, on the mesial and distal sides. Occasionally, these molars have an extra root located in the distolingual aspect. Prevalence of the 3-rooted first permanent molar shows ethnic variation, ranging from about 3% in Caucasian to about 20% in Mongoloid group, which includes Chinese, Japanese, Eskimo, American and Canadian Indians. The frequency of the mandibular molar with three roots decreases in the order of the first permanent molar, the second primary molar, and the first primary molar. If the mandibular first or second primary molar has an additional distolingual root, the adjacent molars, including the first permanent molar, posterior to it also may have it. Coronal morphologic change can occur in the mandibular first primary molars with three roots: the crown had more triangular-shape compared to the one with two roots, possibly affected by the presence of additional distolingual root. Clinically, exact diagnosis and treatment should be taken with those teeth for pulp canal treatment, extraction, and SS Cr.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.2
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• pp.159-167
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• 2010

The purpose of this study was to identify patterns of caries in the dentition of preschool children using cluster analysis and multidimensional scaling. 815 preschool children aged 36-71 months old were examined for caries experience. The first four clusters in the cluster analysis were (1) molars, (2) upper incisors, (3) lower 1st molars, and (4) upper 1st molars in teeth, (1) occlusal surfaces of lower molars and upper 2nd molars, (2) mesial surfaces of upper central incisors, (3) occlusal surfaces of lower 1st molars, and (4) separation between occlusal surfaces of upper and lower 2nd molars in tooth surfaces, and (1) proximal surfaces of upper anterior teeth, (2) occlusal surfaces of lower molars, (3) buccolingual surfaces of upper anterior teeth and (4) buccolingual, proximal, and occlusal surfaces of upper molars and buccolingual and proximal surfaces of lower molars in tooth surfaces groups. In the multidimensional scaling analysis, teeth could be divided into lower 1st molars, upper 1st molars, upper central incisors, upper lateral incisors, lower 2nd molars, upper 2nd molars, and the rest(canines, lower incisors), tooth surfaces could be divided into occlusal surfaces of lower molars, mesial surfaces of upper central incisors, occlusal surfaces of upper molars, and the rest, and tooth surface groups could be divided into proximal surfaces of upper anterior teeth, buccolingual surfaces of upper anteiror teeth, occlusal surfaces of lower molars, and the rest in the order of the distance from others. In the cluster analysis and the multidimensional scaling analysis, caries patterns were different according to the age.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.1
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• pp.27-35
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• 2007

Stainless steel crowns are invaluable restorative material for the treatment of badly broken down primary teeth in pediatric dentistry. But it is difficult to fit margin because selection of size is not easy and they are not adjusted for Korean children. The purpose of this study was to examine and analyze the marginal adaptation of stainless steel crown of posterior primary tooth. Marginal surface was taken by Fine Pix S602 digital camera and measurements of crown were recorded at 20 points that were randomly selected for marginal gap evaluation by Kappa image base program. 1. Mean marginal gap were large upper 2nd primary molar, lower 1st primary molar, lower 2nd primary molar, upper 1st primary molar in order(p<0.05). 2. Mean marginal surface dimension ratio was more than 20% irrespective of tooth. 3. Largest amount of marginal gap was shown at mesial surface in upper 1st, 2nd primary molar and distolingual surface in lower 1st primary molar, buccal surface in lower 2nd primary molar.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.1
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• pp.25-35
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• 2020

The purpose of this study is to evaluate the morphological characteristics of the roots and roots canals of primary molar teeth using Cone-Beam Computed Tomography (CBCT). A total of 68 CBCT images of children aged 4 - 5 years was used for this study. A total of 160 molar teeth were analyzed. Various parameters such as the number of roots and canals, length of root and root canal, and the angulation and shape of the roots were analyzed. All maxillary primary molars had 3 roots. The presence of 2 root canals in 1 root was only observed in the mesiobuccal root of maxillary primary second molars. Most mandibular primary molars had 2 roots, and most mesial roots had 2 root canals. Concerning the length of the roots, the palatal root of the maxillary primary molar was found to be longest whereas the distobuccal root was shortest. In mandibular primary molars, the mesial root was longer than the distal root. In maxillary primary molars, the palatal root had the greatest angulation whereas the distal root has the greatest in mandibular molars. The root and root canals of maxillary primary molars were more curved in shape whereas mandibular primary molars were straight.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.2
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• pp.335-340
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• 2007

Primary teeth and the permanent successor must be understood as interdependent units, where each one of them interacts with and depends upon the other. The spread of pulpal inflammation in primary teeth to the periradicular tissues can lead to early eruption, enamel hypoplasia or hypocalcification, developmental arrest of permanent successor. Also the periapical inflammation cause permanent tooth displacement in various direction. We describe here two clinical cases of displaced permanent successor caused by periapical lesion of mandibular primary molar in children.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.2
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• pp.219-227
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• 2020

Tooth eruption involves a complex developmental process of tooth migration from the dental follicular origin to the final occlusion position in the oral cavity via the alveolar process. Disturbance of tooth eruption can occur at any point in a series of eruption stages; however, horizontal impaction of the mandibular first molar and primary retention of the primary mandibular second molar are rarely observed simultaneously. This study describes the treatment for two cases of horizontally impacted first molar with primary retention of primary molar. The primary retention of the primary mandibular second molar was extracted, and orthodontic traction was applied to the horizontally impacted primary mandibular first molar. Subsequently, displacement of the premolar tooth bud was improved and space regaining for eruption was achieved, guiding to normal eruption of the first molar.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.3
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• pp.362-371
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• 2004

It is essential to have adequate knowledge of the timing of root resorption of deciduous teeth for diagnosis and treatment planning in pediatric and orthodontic dentistry. Dental development is also influenced by hereditary characteristics, environmental factors, race, sex, endocrine reaction, nutrition, socioeconomic condition and secular factor. The aims of the present study were to determine the mean age of root resorption of deciduous teeth in contemporary Korean children and to compare the mean age of root resorption time of deciduous teeth between early 1990s and early 2000s. The study population was made up of Korean children attending the pediatric dentistry ward of Kyungpook National University Hospital. One thousand thirty seven children's panoramic radiograph (girls: 528 persons, boys: 509 persons) in $1990{\sim}1992$ and one thousand sixty five children's panoramic radiograph (girls: 394 persons, boys: 671 persons) in $2001{\sim}2003$ were examined. This study utilized a cross-sectional design. Due to the problems of imaging in the maxillary region and the mandibular incisor region, the mandibular deciduous canine, the mandibular deciduous first molar and the mandibular deciduous second molar were chosen for examination. The results were as follows. 1. There is a tendency for the teeth to resort earlier in the early 2000s group than the in early 1990s group. At the Res c stage, the difference of the mean age was 0.4 years. 2. At the Res c stage, the order of difference of the mean age from smaller to larger for the girls was the mandibular deciduous canine, the mandibular first deciduous molar, and the mandibular second deciduous molar. On the other hand, for the boys, the order was the mandibular second deciduous molar, the mandibular first deciduous molar, and the mandibular deciduous canine. The difference was larger with aging in girls and smaller with aging in boys. 3. There is a tendency for the teeth to resort earlier in girls in both the early 1990s group and the early 2000s group. The difference of the mean age between girls and boys was 0.3 year. 4. The commencement of root resorption of the mandibular deciduous canine was slower than that of the mandibular first deciduous molar. However, the completion of root resorption of the mandibular deciduous canine is faster than that of the mandibular first deciduous molar. The total elapsed time of root resorption from commencement to completion was shortest in the mandibular deciduous canine. 5. For each of the teeth in the early 1990s and the early 2000s groups, the speed of root resorption was in the later stage faster than in the earlier stage. In order to know about the exact timing of root resorption of deciduous teeth, periodic and longitudinal studies preferably covering the entire period of growth, is required.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.1
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• pp.89-100
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• 2005

The purpose of this study was to analyze the morphometrics of primary second molar and permanent first molar. Samples were consisted of normal occlusion in the primary dentition(50 males and 50 females) and permanent dentition(43 males and 43 females). Their upper and lower plaster casts were used and their measuring points were decided, through 3-dimensional laser scanning(3D Scanner, DS4060, LDI, U.S.A.), fitting standard horizontal plane were made for measuring the intercuspal distance, volume of intercuspal area and section curve. The results were as follows; 1. Average distance from the fit plane to the cusp tips of mandibular primary second molar was smaller than any other tooth. (0.05-0.09 mm in male and 0.04-0.09 mm in female). 2. Intercuspal distances of mandibular primary second molar and permanent first molar were larger in male than in female. Especially, there was statistical significance in primary second molar(p<0.05). 3. Intercuspal distance between distobuccal and distolingual cusp was larger in maxillary primary second molar, except cross intercuspal distances. And distances between distal and distolingual cusp, in mandibular primary second molar, between mesiolingual and mesiobuccal cusp, in maxillary first molar, and between distolingual and mesiolingual cusp, in mandibular first molar were larger than any other intercuspal distance. 4. Volume of intercuspal area of primary second molar and permanent first molar was larger in mandible than in maxilla and that of permanent first molar was 1.40-1.75 times of primary second molar (p<0.05). Also it was larger in male than in female, but there was no statistical significance. 5. In most cases, section curves were wider and deeper in permanent dentition than in primary dentition. Except cross intercuspal distances, in maxilla, section curve between mesiobuccal and mesiolingual cusp was the deepest in both dentition. In mandible, section curve between distobuccal and distal cusp was the deepest in permanent dentition and between distolingual and distal cusp was the deepest in primary dentition.

• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.3
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• pp.340-347
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• 2022

Distal displacement of the tooth germ of the mandibular second premolar (MnP2) leads to its impaction and obturation of the eruption path of the mandibular first molar delaying its eruption. The present case report describes the treatment of 2 cases of eruption guidance for distally displaced developing MnP2 that caused delayed eruption of the mandibular first molar. Intentional extraction of primary predecessor results in the mesial shift of the displaced MnP2. However, unfavorable distal ectopic eruption of the mandibular first premolar after the premature loss of primary second molar has been previously reported. Hemisection and sequential extraction of the mandibular primary second molar were performed to mesially shift the distally displaced MnP2, while preventing unfavorable distal ectopic eruption of the mandibular first premolar.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.1
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• pp.87-92
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• 2020

Adenomatoid odontogenic tumor (AOT) is a rare benign odontogenic jaw lesion. It usually occurs in the anterior maxilla and is mostly related to impacted canines in teenagers. A 3-year-old girl was referred from a local dental clinic due to delayed eruption of the right primary mandibular 2nd molar. There was no history of pain or swelling. Radiography revealed a large radiolucency lesion with radiopacities around the unerupted right primary mandibular 2nd molar. Surgical enucleation with extraction of the right primary mandibular 2nd molar and surgical biopsy were performed. Based on the clinical and radiological findings, this lesion was defined as an ameloblastic fibro-odontoma which often develops in the mandible of adolescents. However, this lesion was diagnosed as AOT from the results of the histological examination. This report aimed to present a rare case of AOT in the posterior mandibular area in a very young patient.