• Journal of the korean academy of Pediatric Dentistry
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• v.5 no.1
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• pp.7-11
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• 1978

Of 633 children, 334 in male and 299 in female, whose ages ranged from 3 to 13 years old, the amounts of development of teeth germ were observed according to ages with oblique lateral cephalogram to study the developing state of teeth germ of mandibular premolars. The results were as followings; 1. The time of actively develop:ng tooth germ was observed about 10 years old both in male and in female. 2. The increasing rate of development of tooth germ a year was higher in female than in male at mandibular 1st premolar and in male than in female at mandibular 2nd premolar. 3. Age of complete tooth germ development was earlier in female than in male at mandibular 1st and 2nd premolars.

• The korean journal of orthodontics
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• v.12 no.2
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• pp.95-108
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• 1982

The purpose of this study was to analyze the growth and development of tooth germ and dental arch related to the bone growth during the fetal period. From 70 maxillae and 61 mandibles of the fetus aged 5, 6, 7, 8, 9 and 10 months, X-ray films were taken and measured. The results were as follows; 1. There was remarkable bone growth in the anterior and posterior area of palatum osseum, that were the intetior portion of both deciduous canines anteriorly and the intero-posterior portion of both deciduous second molars posteriorly, where there was active bone growth and radiate formation of bony trabeculae was found. 2. The Growth of anterior tooth germ was greater than that of posterior tooth germ, so anterior tooth germs were crowded. Especially in maxilla, the tooth germs of deciduous lateral incisors were located inside of dental arch and the tooth germs of deciduous canines were located outside of dental arch. 3. Crowding amount increased with the fetal age because the growth of tooth germs was greater than that of jaw bone. 4. In the growth of upper dental arch, the increase of width was greater than that of length. 5. There was proportional relationship between the area of Palatal Trapezoid and the fetal age.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.1
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• pp.53-61
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• 2007

In case of missing tooth caused by dental caries or periodontal disease, it can be restored by various methods, and there has been much interest in implant and tooth transplantation. The success of tooth transplantation is going to be attained through the knowledge of growth, development and calcification of tooth. Tooth transplantation has been experimented in vivo and in vitro. Many animals such as rats, mice, cats and dogs are used for tooth transplantation experiment in vivo. In most experiments, tooth was transplanted into the extraoral site, but rare into the intraoral site In this study, to observe the capacity of formation and mineralization of tooth germ, first molar of a matured white rat was extracted and the cap stage tooth germ of a 13.5 Embryonic day embryo rat was transplanted into the extracted socket. The rats were killed 6 months later and the radiographical and histological results are as followings. 1. Tooth germ transplanted for 2 and 6 months are developing calcified tooth material such as dentin, cementum, pulp tissue, and epithelium around enamel space in the maxilla was seen. 2. The epithelium around enamel space was located beneath the oral epithelium and contained connective tissue and periodontal ligament. 3. Tooth formation was progressed as transplantation period but the size of newly formed tooth was small and the shape of tooth was incomplete.

• International Journal of Oral Biology
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• v.40 no.3
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• pp.151-159
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• 2015

Odontogenic cells express many genes spatiotemporally through complex and intricate processes during tooth formation. Therefore, investigating them during the tooth development has been an important subject for the better understanding of tooth morphogenesis. The present study was performed to identify the genetic profiles which are involved in the morphological changes during the different stages of rat tooth development using the Agilent Rat Oligonucleotide Microarrays. Morphologically, the maxillary 3rd molar germ at 10 days post-partum (dpp) was at the cap/bell stage. In contrast, the maxillary 2nd molar germ showed the root development stage. After microarray analysis, there were a considerable number of up- or down-regulated genes in the 3rd and the 2nd molar germ cells during tooth morphogenesis. Several differentially expressed genes for nerve supply were further studied. Among them, neuroligin 1 (Nlgn 1) was gradually downregulated during tooth development both at the transcription and the translation level. Also, Nlgn 1 was mostly localized in the dental sac, which is an important component yielding the nerve supply. This genetic profiling study proposed that many genes may be implicated in the biological processes for the dental hard tissue formation and, furthermore, may allow the identification of the key genes involved in the nerve supply to the dental sac.

• Imaging Science in Dentistry
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• v.52 no.3
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• pp.275-281
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• 2022

Purpose: The aim of this study was to assess the performance of a deep learning system for permanent tooth germ detection on pediatric panoramic radiographs. Materials and Methods: In total, 4518 anonymized panoramic radiographs of children between 5 and 13 years of age were collected. YOLOv4, a convolutional neural network (CNN)-based object detection model, was used to automatically detect permanent tooth germs. Panoramic images of children processed in LabelImg were trained and tested in the YOLOv4 algorithm. True-positive, false-positive, and false-negative rates were calculated. A confusion matrix was used to evaluate the performance of the model. Results: The YOLOv4 model, which detected permanent tooth germs on pediatric panoramic radiographs, provided an average precision value of 94.16% and an F1 value of 0.90, indicating a high level of significance. The average YOLOv4 inference time was 90 ms. Conclusion: The detection of permanent tooth germs on pediatric panoramic X-rays using a deep learning-based approach may facilitate the early diagnosis of tooth deficiency or supernumerary teeth and help dental practitioners find more accurate treatment options while saving time and effort

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.25 no.4
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• pp.311-323
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• 1999

The osteonectin is a sort of glycoprotein which is secreted in human tissues. The osteonectin is generally detected in number of normal or neoplastic human tissues in vivo, but hasn't been studied the role of osteonectin in developing human teeth and odontogenic tumors. We evaluated degree of the expression of osteonectin immunohistochemically in 20 cases of developing tooth germ which growth from fetus 5 to 38 weeks, and total 51 odontogenic tumors whitch has taken from routine biopsy, such as 10 ameloblastomas, 5 cases of adenomatoid odontogenic tumors and odontomas and odontogenic fibromas, 4 cases of cementomas and calcifying epithelial odontogenic cyst and odontogenic keratocyst and dentigerous cysts and periapical cysts, and 3 cases of ameloblastic fibromas and myxomas. The results were as follows: 1. The osteonectin on the bud stage of tooth germ was strongly expressed in the epithelial dental lamina and in the outer dental epithelium on the early bell stage, and also strongly expressed in the inner dental epithelium on the late bell stage of tooth germs. 2. In ameloblastoma, the osteonectin was strongly expressed in the epithelial tumor component and especially in the acanthomatous types. 3. In both of calcifying epithelial odontogenic tumor and adenomatoid odontogenic tumors, the osteonectin was moderately expressed on the duct like spindle cells and epithelial tumor cells around calcification areas. 4. In odontogenic tumors originated from epithelial-mesenchymal tissues, the osteonectin was moderately expressed on the epithelial tumor components and in odontogenic cysts, it was expressed in ghost cells and calcification areas only. These were summaried the osteonectin may be strongly related to the developing tooth germ and odontogenic tumors and could be regulated hard tissue of human tooth in morphogenesis and involved with calcification mechanism in development odontogenic tumors.

• The Journal of the Korean dental association
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• v.42 no.2 s.417
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• pp.150-157
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• 2004

Inverted maxillary incisor is that maxillary incisor rotates counterclockwise direction. The cause of this 'Inverted incisor' is the injury of the deciduous predecessor transmitted to the developing permanent tooth germ or displacement of permanent tooth crown portion from unknown origin. Dilaceration, defined as a distorted root from, may result from mechanical injury during eruption period or ectopic development of tooth germ. This article presents a case of an inverted and dilacerated maxillary right central incisor. Through orthodontic traction, the dilacerated and inverted incisor was successfully moved into the proper position.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.49 no.4
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• pp.184-191
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• 2023

Germectomy is a surgical method most typically performed in young adults. The indications for treatment are controversial. The purpose of this review was to determine the correct indications for germectomy and to discuss the advantages and disadvantages of the procedure. We reviewed the surgical techniques (anesthetic methods, patient preparation, and flap designs) and complications. Germectomy for orthodontic purposes is a common indication for surgical removal of tooth germ among young patients. Several studies have supported removal at an earlier age to produce fewer surgical complications. Several surgical techniques have been described in the literature.

• 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.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.30 no.5
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• pp.438-443
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• 2004

Objectives : The proper development of the facial structures relies upon a sequence of tightly regulated signaling interactions between the ectoderm and mesoderm involving the participation of several families of signaling molecules. Among these, bone morphogenetic proteins (BMPs) have been suggested to be a key signal that regulates the development of the mandible and the initiation and morphogenesis of the teeth. The aim of this study was to examine the artificial development of the mandibular structures and to examine the role of BMPs on tooth morphogenesis and differentiation using an organ culture system. Materials and Methods : The tooth germs from Ed 11.5, 13.5 mice were dissected, and transplanted into the diastema of the mandible primordia. The mandibles containing the transplanted tooth germs were cultured in vitro. During this period, beads soaked with BMP4 were implanted around the transplanted tooth germs. In addition, a diastema block containing the transplanted tooth germ was dissected, then transferred to an adult mouse kidney. After the organ culture, the developing mandibular explant was removed from the kidney and prepared for the tissue specimens. Odontogeneis of the transplanted tooth germs was examined after Hematoxylin-eosin, Masson-trichrome staining. Results : Proliferation and differentiation of the tooth germs cultured in the diastema was observed. In the BMP4-treated tooth germs, the formation of the first and second molars was noted. The crown of the developing tooth showed the formation of a mature cusp with the deposition of enamel and dentin matrix. In conclusion, it was confirmed that BMP4 is involved in the formation of a dental crown and the differentiation of ameloblasts and odontoblasts of the molar tooth during the development of the transplanted tooth germs.