• 대한소아치과학회지
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• 제5권1호
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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.

• 대한치과교정학회지
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• 제12권2호
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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.

• 대한소아치과학회지
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• 제34권1호
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• pp.53-61
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• 2007

치아우식증이나 치주질환으로 치아를 상실한 경우 여러 가지 방법으로 수복 치료할 수 있으나 그 중에서 임플란트와 치아 이식에 대한 관심이 높아지고 있다. 최근에는 치아 이식에 대한 성공률을 높이기 위해서 치아를 형성시키고 발육시키는 과정에 관한 많은 연구가 이루어지고 있다. 치아싹 이식은 생체 내와 생체 외에서 연구되고 있고, 생체 내 이식은 쥐와 생쥐, 고양이, 개 등 여러 동물에서 시행되고 있다. 이러한 생체 내 이식은 대부분 구강 외에서 시행되고 있으며 구강 내 이식에 대한 연구는 드물다. 본 연구는 악골 내에 이식한 치아싹이 발육되고 석회화되는지 관찰하기 위하여 성숙한 흰쥐의 상악 제 1 구치를 발치하고 그 발치와에 임신 13.5일 된 태아쥐에서 모상기의 하악 제 1 구치의 치아싹을 이식하고 2, 6 개월 후 희생하여 방사선학적 그리고 조직학적으로 관찰하여 다음과 같은 결과를 얻었다. 12 개월과 6개월 동안 악골 내에 이식한 치아싹은 석회화된 치아 조직이 형성 되었고 치아 조직에서 상아질과 백악질, 치수 조직이 관찰되었으며 법랑질 공간 주변은 상피로 둘러싸여 있었다. 2. 6개월 동안 구강 상피 하방에 위치한 치아 조직은 상피로 둘러싸여 있었고 주위에 치주인대 및 결합조직이 관찰되었다. 3. 이식한 시간이 경과함에 따라 치아 형성이 진전되었으나 치아 조직은 크기가 작았고 형태학적으로 완전하지 못하였다.

• International Journal of Oral Biology
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• 제40권3호
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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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• 제52권3호
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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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• 제25권4호
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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.

• International Journal of Oral Biology
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• 제49권2호
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• pp.48-52
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• 2024

This study explores the histological features and Bmp4 expression patterns in the replaced tooth germ of Xenopus laevis. Tooth germ formation starts from the dental placode through epithelial-mesenchymal interactions, involving various signaling pathways such as Fgf, Shh, Bmp, and Wnt. In mice, Bmp4 expression in the dental placode inhibits Pax9 expression in the dental mesenchyme. Although absent in the presumptive dental lamina of birds and toothless mammals, Bmp4 remains conserved in reptiles and fish owing to gene duplication. However, its expression in amphibian tooth germs is poorly understood. Three-month-old X. laevis were employed in this study. Initially, samples underwent paraffin embedding and were sectioned into 5 or 12 ㎛ ribbons for H&E staining and in situ hybridization, respectively. Results revealed teeth appearing in two maxillary rows: the labial side, with prefunctional and functional teeth, and the lingual side, with replaced tooth germs behind functional teeth. Enameloid was observed between the inner dental epithelium and dental mesenchyme at the cap or early bell stages, whereas enamel and dentin formed during the late bell or mineralization stages from the replaced tooth germ. Bmp4 expression was evident in the inner dental epithelium (ameloblasts), dental papilla (odontoblasts), stellate reticulum, and Hertwig's epithelial root sheath. Overall, these findings highlight the conservation of Bmp4 expression in X. laevis tooth development.

• 대한치과의사협회지
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• 제42권2호통권417호
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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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• 제49권4호
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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.

• 대한소아치과학회지
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• 제33권4호
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• pp.722-727
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• 2006

치아가 정상적으로 맹출해야 하는 시기를 지나서도 골조직 내에서 맹출하지 않을 수 있으며, 이러한 치아를 매복치라 한다. 유치의 매복은 드물게 나타나며, 더구나 과거의 문헌 고찰에 의하면 현재까지 보고된 계승 영구치 하방에 매복된 유치는 극히 드물다. 대부분의 경우 매복된 유치는 제 2 유구치이다. 유치의 매복에 대한 병인은 유치 치배의 비정상적인 발달로 인해 조기에 유착이 일어나는 것으로 추측되어지고 있으나, 아직까지 정확하게 밝혀진 바는 없다. 전위는 동일한 사분악 내의 인접한 두 개 치아의 위치가 서로 바뀐 것을 말하며, 영구 상악 견치와 제 1소구치 사이에 가장 많이 발생한다. 그 빈도는 1% 내외로 낮으며, 특히 유치열의 전위는 거의 발표된 바가 없다. 본 증례는 양악 양측 제 2유구치의 매복을 주소로 본과에 의뢰된 환자의 구강 및 방사선 검사 결과 매복된 제 2유구치와 후속 제 2소구치 사이의 수직 전위가 관찰되었기에 보고하는 바이다.