• Imaging Science in Dentistry
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• 제51권3호
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• pp.323-328
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• 2021

Tooth extraction after head and neck radiotherapy exposes patients to an increased risk for osteoradionecrosis of the jaw. This study reports the results of a radiographic analysis of bone neoformation after tooth extraction in a case series of patients who underwent radiation therapy. No patients developed osteoradionecrosis within a follow-up of 1 year. Complete mucosal repair was observed 30 days after surgery, while no sign of bone formation was observed 2 months after the dental extractions. Pixel intensity and fractal dimension image analyses only showed significant bone formation 12 months after the tooth extractions. These surgical procedures must follow a strict protocol that includes antibiotic prophylaxis and therapy and complete wound closure, since bone formation at the alveolar socket occurs at a slower pace in patients who have undergone head and neck radiotherapy.

• Imaging Science in Dentistry
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• 제53권4호
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• pp.303-312
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• 2023

Purpose: This study investigated the prevalence of developmental and acquired pathologic conditions associated with impacted third molars (3Ms) in a Southern Brazilian population and evaluated whether demographic and tooth characteristics were correlated with the presence of bone or tooth lesions. Materials and Methods: Panoramic radiographs were assessed for developmental (bone-related) or acquired (tooth-related) pathoses associated with impacted upper or lower 3Ms. Data on tooth positioning, tooth development, and patient demographics were collected. A trained, calibrated postgraduate student evaluated all images. Binary and multivariate logistic regression models were used to assess associations between outcomes and the demographic and radiographic variables. The threshold for statistical significance was set at 5% (P<0.05). Results: The sample comprised panoramic radiographs from 2054 patients, predominantly female (59.2%), with a mean age of 27.2±11.5 years. Overall, 4066 impacted 3Ms were evaluated, revealing 471 (11.6%) developmental and 710 (17.5%) acquired pathoses. Among the developmental pathoses, 460 (95.2%) were indicative of dentigerous cysts. Male sex, lower 3M location, vertical or distoangular positioning, and incomplete root formation were associated with an elevated likelihood of developmental pathology. Lower tooth position, complete root formation, and partial eruption were linked to an increased probability of an acquired pathology in the third or second molar. Conclusion: The prevalence of pathologic conditions associated with impacted 3Ms was low. Male sex, lower 3M placement, horizontal or distoangular positioning, and incomplete root formation were associated with developmental pathoses, while lower tooth position, complete root formation, and partial eruption were related to acquired pathoses.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제30권5호
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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.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제35권2호
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• pp.73-81
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• 2013

Purpose: Smad4 is a central mediator for transforming growth factor-${\beta}$/bone morphogenetic protein ($TGF-{\beta}/BMP$) signals, which are involved in regulating cranial neural crest cell formation, migration, proliferation, and fate determination. Accumulated evidences indicate that $TGF-{\beta}/BMP$ signaling plays key roles in the early tooth morphogenesis. However, their roles in the late tooth formation, such as cellular differentiation and matrix formation are not clearly understood. The objective of this study is to understand the roles of Smad4 in vivo during enamel and dentin formation through tissue-specific inactivation of Smad4. Methods: We generated and analyzed mice with dental epithelium-specific inactivation of the Smad4 gene (K14-Cre:$Smad4^{fl/fl}$) and dental mesenchyme-specific inactivation of Smad4 gene (Osr2Ires-Cre:$Smad4^{fl/fl}$). Results: In the tooth germs of K14-Cre:$Smad4^{fl/fl}$, ameloblast differentiation was not detectable in inner enamel epithelial cells, however, dentin-like structure was formed in dental mesenchymal cells. In the tooth germs of Osr2Ires-Cre:$Smad4^{fl/fl}$ mice, ameloblasts were normally differentiated from inner enamel epithelial cells. Interestingly, we found that bone-like structures, with cellular inclusion, were formed in the dentin region of Osr2Ires-Cre:$Smad4^{fl/fl}$ mice. Conclusion: Taken together, our study demonstrates that Smad4 plays a crucial role in regulating ameloblast and odontoblast differentiation, as well as in regulating epithelial-mesenchymal interactions during tooth development.

• Journal of Korean Dental Science
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• 제16권2호
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• pp.182-191
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• 2023

Purpose: This study investigated the orthodontic tooth movement after weekly parathyroid hormone (PTH) injection in mongrel dogs and analyzes bone formation activity on the tension and pressure sides of the tooth movement in mongrel dogs. Materials and Methods: Three mongrel dogs were used in this study. The first premolar was extracted and orthodontic force using 150 g of closed coil springs between the canine and second premolar was applied. The low-dose PTH group (PTH_1) and high-dose PTH group (PTH_2) received weekly injections of 1.61 ㎍/kg and 3.23 ㎍/kg of PTH, respectively. The control group received weekly injections of 1 ml of saline. Clinical, histomorphometric analysis were carried out. Result: The orthodontic tooth movement was greatest in the PTH_2 group and the lowest in the control group. Fluorescence staining images showed higher bone remodeling on the tension side of the tooth movement in the PTH_1 and PTH_2 groups. PTH_2 group showed a thicker labeling band than the PTH_1 group. PTH_2 group showed the highest mineral apposition rate and bone formation rate, followed by the PTH_1 group and the control group. Conclusion: Weekly intermittent PTH injection, especially in the short-term and at higher doses with orthodontic force, successfully increased orthodontic tooth movement and bone remodeling in mongrel dogs.

• 치과방사선
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• 제3권1호
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• pp.7-18
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• 1973

The authors have taken the x-ray films of carpal bone and orthopantomographs in Korean children to research the degree of ossification of carpal bone, that of calcification of tooth in jaw bone, the eruption rate of tooth, and the completion rate of apical foramen, and have compared the bone age and tooth age. We have gained a series of intersting conclusions to dare to report. 1. The ossification of carpal bone and the growth of tooth had processed proportionally to each other. 2. Both the bone age and tooth age were earlier in the female than in the male. 3. The completion of tooth crown formation and that of tooth root formation had processed proportionally to each other, and the general tendency of process was the earliest in the mandibular first molar and the latest in the second molar. 4. The eruption of tooth was the earliest in the mandibular first molar. The other teeth had erupted in the following orders: the central incisor, the lateral incisor, the first premolar, the second premolar, the canine and the second molar.

• International Journal of Oral Biology
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• 제46권2호
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• pp.67-73
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• 2021

This study summarizes the recent cutting-edge approaches for dentin regeneration that still do not offer adequate solutions. Tertiary dentin is formed when odontoblasts are directly affected by various stimuli. Recent preclinical studies have reported that stimulation of the Wnt/β-catenin signaling pathway could facilitate the formation of reparative dentin and thereby aid in the structural and functional development of the tertiary dentin. A range of signaling pathways, including the Wnt/β-catenin pathway, is activated when dental tissues are damaged and the pulp is exposed. The application of small molecules for dentin regeneration has been suggested as a drug repositioning approach. This study reviews the role of Wnt signaling in tooth formation, particularly dentin formation and dentin regeneration. In addition, the application of the drug repositioning strategy to facilitate the development of new drugs for dentin regeneration has been discussed in this study.

• 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.

• 대한치과교정학회지
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• 제34권1호
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• pp.71-81
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• 2004

치아의 맹출 과정과 치간이개로 유도된 치아 및 치조골의 흡수 과정에서 치주인대 세포와 치주인대 단백질의 기능을 알아보기 위하여, 발육 중인 흰쥐를 치근 형성 전, 치근 형성 시작과 치근 형성 및 맹출 시기로 구분하여 조직 표본을 제작하고, 또한 성 장 중인 흰쥐를 2주간 치간 이개시켜 조직표본을 제작하였다. 치주인대 섬유모세포에서 특이적으로 발현되며 치주인대의 분화와 성숙에 관여하는 PDLs22단백질과 치아와 치조골의 파괴와 흡수를 조절하는 것으로 알려진 RANKL과 OPG의 발현을 면역 조직화학적으로 연구하였다. PDLs22 단백질은 치근 형성이 시작되면서부터 치낭세포와 골모세포에서 발현되어, 치아가 맹출하는 과정에서도 그 발현이 계속 유지되었으나, 치간이개에 의하여 치주인대가 개조되는 부위에서는 발현이 감소하였다. RANKL은 치근형성 과정에서는 미약한 발현을 나타내었으나, 치아가 맹출하면서 발현이 증대되었으며, 치간이개에 의한 치근과 치조골 흡수과정에서는 치주인대세포, 골모세포, 치수세포 및 파치세포에서 발현이 증대되었다. OPG는 치근이 형성되는 시기에는 강한 발현을 보였으나, 치아가 맹출하면서 발현이 현저히 감소하였고, 치아와 치조골의 흡수가 진행됨에 따라서 발현이 다소 감소하였다.

• 대한소아치과학회지
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• 제33권1호
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• pp.35-42
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• 2006

정상적인 치열의 형성 및 치아의 생성과정을 분석하고 실제로 임상에 적용하기 위해 치아의 발생과정을 연구하는 것은 매우 중요하다. 본 연구는 이식된 태아 치아싹의 석회화가 가능하고 정상적인 구조로 발육할 수 있는지 밝히기 위해, 그리고 악골 자체가 새로운 이식 공여부로 사용가능한지 알기 위해 흰쥐의 발치와에 치아싹을 이식하여 치아의 형성을 살펴보고자 하였다. 이를 위하여 성숙한 흰쥐의 상악 제 1구치를 발거한 발치와에 13.5일된 태아쥐의 치아싹을 이식한 후 4, 8주 후에 희생하여 조직학적 및 방사선학적으로 관찰하여 다음과 같은 결과를 얻었다. 1. 이식된 치아싹에서 상아질과 백악질, 치수, 치주인대의 소견을 갖는 석회화된 조직이 형성되었다. 2. 형성된 경조직 및 연조직은 정상적인 치아형성과정에 비해 발육이 늦었으며 유착 및 골양상아질(osteodentin)과 같은 비정상적 조직이 관찰되었다. 3. 석회화된 조직은 8주내에 악궁으로 맹출하는 소견이 관찰되지 않았다.