• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.3
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• pp.382-388
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• 2002

In the present study, crown diameters and their sexual differences in deciduous teeth were investigated in children of Chon-ju city, Korea. Plaster casts of the deciduous dentitions obtained from 50 boys and 50 girls were examined. Mesiodistal and buccolingual crown diameters were measured using a digital caliper(0.01mm) according to the definitions of Seipel and Moorees et al. These measurements were performed three times, and intra-observer measurement errors were calculated by the single determination method. The crown index, module and area were calculated in order to provide a comparison of crown proportions. The results obtained were summarized as follows; 1. The mean values of intra-observer measurement errors were 0.255mm and are unlikely to have influenced the statistical analysis. 2. The mean values of mesiodistal and buccolingual crown diameters examined were larger in boys than girls. 3. The mean coefficient of variation was 5.6 in the deciduous dentition. There were a trend for the primary second molar to be the least variable in size of all teeth both in boys and girls. 4. Fluctuating asymmetry is the difference between left and right antimeres in individuals. Primary second molars were less asymmetrical than primary first molars in both dimensions. 5. In maxillary teeth, Crown index is larger in boys than in girls. In contrast, in mandibular teeth, except primary canine, it is larger in girls than in boys. Crown module is larger in boys than in girls and increased progressively from primary first incisor to primary second molar. Crown area is consistently larger in boys than in girls. The minimum crown area is mandibular primary incisor and maximum crown area is maxillary primary second molar.

• 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.37 no.1
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• pp.130-135
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• 2010

Ectopic eruption is caused by an abnormal direction of eruptive path, most common in maxillary first molar, mandibular lateral incisor, and maxillary canine, and sometimes mandibular first molar. Ectopic eruption of first molar leads to abnormal root resorption of second deciduous molar, which, if left untreated, could cause premature loss of second deciduous molar; mesial tilting and rotation of first permanent molar; lack of space for eruption of second premolar; and occlusal problems. Therefore early treatment is advised when diagnosed as ectopic eruption. Treatment of ectopic eruption in the first permanent molar involves providing proper guidance for the direction of eruption using interproximal wedging and distal tipping methods while preserving second deciduous molar. This case report shows satisfactory results of the ectopic eruption of mandibular first molars in young patients who were treated with Humphrey appliance and Halterman appliance.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.446-452
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• 1999

Ectopic eruption of the first permanent molar means the first permanent molar assumes an atypical path of eruption resulting in premature atypical resorption of the second primary molar. If the reversible eruption does not occur, early loss of the second primary molars results in space loss, mesial tipping of the first permanent molar, impaction of the second premolar, buccal segment crowding and overeruption of opposing tooth. The main objectives of treatment are (1) to prevent loss of the second deciduous molars so it can continue to serve as a space maintainer and (2) to regain lost arch length, allowing the second premolar to erupt into normal position. The optimal treatment approach depends on a number of factors including the clinical eruption status of /6/, the change in position of /6/, the amount of enamel ledge of /E/ entrapping /6/, the mobility of /E/, and the presence of pain or infection. Unilateral appliance to correct the mesial angulation of ectopic permanent first molars, as in the majority of the appliance designs, would produce a resultant force that would further enhance the space loss. A bilateral support similar to the holding arch design is recommended to maximize the anchorage. These case reports present the successful result of preserving space for the second premolar in treatment of ectopic eruption of the first permanent molar using Halterman appliance with bilateral anchorage on patients visiting department of pediatric dentistry in Samsung Medical Center.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.1
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• pp.98-102
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• 2000

Ectopic eruption is out of a normal position by local eruption disturbance in the developing permanent molar. The prevalence of ectopic eruption is reported to be the between 2 and 6%, most often associated maxillary first permanent molar whereas, the occurrence for the mandibular is quite rare. The etiologic factors of ectopic eruption are inadequate arch length, lack of growth in the posterior region of the jaw, mesially inclined eruption path of first permanent molars, abnormally large first permanent molars, hereditary factor and a stainless steel crown which has been improperly restored. Ectopic eruption can be treated by the use of brass wire, separating elastics, distal disking and Humphrey appliance and the use of removable appliance and cervical traction headgear after extraction of the second primary molar. This case was that lower right first permanent molar was mesially tilted state by locking on the stainless steel crown of a lower right second primary molar. The stainless steel crown was removed and Humphrey appliance was set. Like this case, ectopic eruption could be happened by the stainless steel crown which improperly restored. In restoration of the stainless steel crown, selection of proper size, trimming and contouring are very important.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.3
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• pp.495-501
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• 2003

Impaction is defined as the cessation of the eruption of the tooth caused by a clinically or radiographically detectable physical barrier in the eruption path or by the ectopic position of tooth germ. Besides the third molars and the maxillary canines, the most common impacted tooth is the second premolar. The overall frequency of premolar impaction has been reported to be 0.5%. In some cases, orthodontic traction and surgical repositioning may be indicated. When impacted second premolar is involved with prolonged retained second primary molar, extraction of primary molar and space maintenance lead to eruption of second premolar. In these cases, all patients visited to department of pediatric dentistry of Kyungpook National University Hospital for the chief complaint of unerupted second premolar. Extraction of prolonged retained second primary molar and space management are tried for spontaneous eruption of impacted second premolar tooth. The results were as follows: 1. When impacted second premolar is involved with prolonged retained second primary molar, minimal treatment via elimination of primary molar leads to successful results. 2. Proper space management and periodic radiographic examination are required before eruption of second premolar. 3. Sufficient time must be allowed for confirm of tooth movement before orthodontic traction or surgical repositioning. 4. The result is more successful in incomplete root development.

• 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.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.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.3
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• pp.352-358
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• 2021

Molar-incisor malformation (MIM) is characterized by malformation in the root with a normal crown. While MIM mostly occurs in the permanent first molar, it has also been reported in the maxillary central incisor and the primary second molar (PSM), but anatomical analysis of the primary teeth with MIM has not been studied to date. In this case report, a patient with MIM was reported, and an extracted PSM with MIM was analyzed with micro computed tomography (CT). A cervical constriction morphology of the cementoenamel junction (CEJ) can be observed in extracted PSM. In micro CT analysis, characteristics such a mineralized plate (cervical mineralized diaphragm) in the CEJ area, complex root canal morphologies, a calcified mass inside the pulp chamber, and constricted pulp chamber of crown portion were observed.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.4
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• pp.722-727
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• 2006

Most of impacted teeth reported are permanent teeth. Impaction of primary tooth caused by primary failure of eruption is rare and the most of impacted primary tooth are second primary molars. The etiology of a primary molar impaction would appear to be a physical barrier, early ankylosis of the tooth, abnormal development of the primary molar germ or malposition of the successor bud. Transposition has been described as an interchange in the position of two teeth within the same quadrant of the dental arch. It is most commonly seen with canine and lateral incisor teeth, but is rarely associated with the primary dentition. The two cases show the transposition of impacted primary molar and the tooth germ of second premolar in their clinical and radiographic examinations. In case 1, lower second primary molar was deeply impacted inferiorly to the tooth germ suspected to be a second premolar. In case 2, impacted all second primary molars were positioned inferiorly to the tooth germs suspected to be the successors. We extracted all second primary molars under general anesthesia and the extracted tooth germs appeared to be second premolars.