mTORC1 signaling pathway regulates tooth repair / 国际口腔科学杂志·英文版

Tooth germ injury can lead to abnormal tooth development and even tooth loss, affecting various aspects of the stomatognathic system including form, function, and appearance. However, the research about tooth germ injury model on cellular and molecule mechanism of tooth germ repair is still very limited. Therefore, it is of great importance for the prevention and treatment of tooth germ injury to study the important mechanism of tooth germ repair by a tooth germ injury model. Here, we constructed a Tg(dlx2b:Dendra2-NTR) transgenic line that labeled tooth germ specifically. Taking advantage of the NTR/Mtz system, the dlx2b+ tooth germ cells were depleted by Mtz effectively. The process of tooth germ repair was evaluated by antibody staining, in situ hybridization, EdU staining and alizarin red staining. The severely injured tooth germ was repaired in several days after Mtz treatment was stopped. In the early stage of tooth germ repair, the expression of phosphorylated 4E-BP1 was increased, indicating that mTORC1 is activated. Inhibition of mTORC1 signaling in vitro or knockdown of mTORC1 signaling in vivo could inhibit the repair of injured tooth germ. Normally, mouse incisors were repaired after damage, but inhibition/promotion of mTORC1 signaling inhibited/promoted this repair progress. Overall, we are the first to construct a stable and repeatable repair model of severe tooth germ injury, and our results reveal that mTORC1 signaling plays a crucial role during tooth germ repair, providing a potential target for clinical treatment of tooth germ injury.

Células madre en odontología: nuevas perspectivas / Stem cells in dentistry: new perspectives

En el campo de la odontología, prevalecen actualmente alternativas terapéuticas con una filosofía conservadora. Sin embargo, con el advenimiento de los tratamientos con células madre (CM), se amplían las posibilidades terapéuticas, que buscan la combinación y el equilibrio entre la intervención tradicional y las posibilidades de reposición de estructuras anatómicas dañadas, a través de la regeneración de tejidos utilizando células madre o sus derivados (AU)

In the dentistry field, therapeutic alternatives with a conservative philosophy currently prevail. However, with the advent of stem cell (SC) treatments, therapeutic possibilities are expanding, seeking a combination and balance between traditional intervention and the pos- sibility of replacing damaged anatomical structures through tissue regeneration, using stem cells or their derivatives (AU)

KLF6 facilitates differentiation of odontoblasts through modulating the expression of P21 in vitro / 国际口腔科学杂志·英文版

Multiple signaling pathways are involved in the regulation of cell proliferation and differentiation in odontogenesis and dental tissue renewal, but the details of these mechanisms remain unknown. Here, we investigated the expression patterns of a transcription factor, Krüppel-like factor 6 (KLF6), during the development of murine tooth germ and its function in odontoblastic differentiation. KLF6 was almost ubiquitously expressed in odontoblasts at various stages, and it was co-expressed with P21 (to varying degrees) in mouse dental germ. To determine the function of Klf6, overexpression and knockdown experiments were performed in a mouse dental papilla cell line (iMDP-3). Klf6 functioned as a promoter of odontoblastic differentiation and inhibited the proliferation and cell cycle progression of iMDP-3 through p21 upregulation. Dual-luciferase reporter assay and chromatin immunoprecipitation showed that Klf6 directly activates p21 transcription. Additionally, the in vivo study showed that KLF6 and P21 were also co-expressed in odontoblasts around the reparative dentin. In conclusion, Klf6 regulates the transcriptional activity of p21, thus promoting the cell proliferation to odontoblastic differentiation transition in vitro. This study provides a theoretical basis for odontoblast differentiation and the formation of reparative dentine regeneration.

Early loss of primary molar and permanent tooth germ caused by the use of devitalizer during primary molar root canal therapy: Two cases report / 北京大学学报(医学版)

Devitalization has been widely used in the root canal therapy of primary and permanent teeth in China more than ten years ago. With the development of local anesthetic drugs and injection technologies, this treatment method with high potential risks has been gradually abandoned. However, a questionnaire survey targeted all the participants at the 2018 China Pediatric Dentistry Conference showed that the devitalizer utilization proportion was still as high as 38.1% (383/1 005), even though the ratio was much lower than 75.5% (105/139) in 2003. These doctors had pay more attention to tissue burn caused by devitalizer marginal leakage or direct leakage, and know how to identify and handle with devitalizer burn. Devitalizers were usually made of arsenic trioxide, metal arsenic or paraformaldehyde, which have cytotoxicity, allergenicity, mutagenicity, carcinogenicity, and teratogenic effects on animals. Marginal leakage of devitalizers have high risks of causing soft and hard tissue necrosis. Most of the dentists have an understanding of the potential damages of arsenic containing devitalizers, so they will choose parafor maldehyde with relatively less toxicity. Paraformaldehyde has a certain self limitation, and there are few cases reported, so some dentists lack of vigilance. Paraformaldehyde can also causes tissue necrosis if leakage happens, and the treatment methods are similar to that of arsenic containing devitalizers. When handling with devitalizers burn, the necrosed soft and hard tissue, for example gingiva, alveolar bone or teeth that cannot keep, must be completely removed until fresh blood appears, then rinse with large amount of saline and seal with iodoform gauze. This paper described two cases of devitalizer burn during the root canal treatment of primary molars, both of the doctors failed to identify the devitalizer burn symptoms in the early stage, thus didn't do proper treatments immediately after burning. Resulting in the necrosis of large area of gingiva and alveolar bone, loss of primary molars and permanent tooth germs 1-2 months after devitalizer burn. This paper reported these two cases in detail in order to warn dentists the high risks of using any kind of devitalizers, help them learn how to identify and treat devitalizer burn, and remind them to stop using devitalizers as soon as possible.

Odontoma e retenção dentária: relato de caso / Odontoma and dental retention: case report

Este relato de caso teve como objetivo descrever a realização de um procedimento cirúrgico de remoção de um odontoma composto em um paciente pediátrico, e a partir disto elucidar a importância do diagnóstico precoce, assim como o seu tratamento. Um paciente do sexo masculino de 8 anos com ausência de erupção dos germes dentários 21 e 22 e retenção prolongada dos dentes 61 e 62. Foi realizado o planejamento cirúrgico de remoção do tumor e dos elementos dentários não esfoliados. Durante o acompanhamento de 6 meses do paciente houve a erupção do dente 22 e o 21 permaneceu retido, o qual se encontra em acompanhamento ortodôntico para manutenção do espaço e possível tracionamento orto-cirúrgico. Portanto, o diagnóstico e investigação de situações clínicas e radiográficas sugestivas de odontomas são imprescindíveis para evitar danos futuros a dentição permanente... (AU)

This case report aimed to describe the performance of a surgical procedure of removal of a compound odontoma in a pediatric patient, and from this to elucidate the importance of early diagnosis and treat ment. A male patient 8 years old without no eruption of tooth germs 21 and 22 and prolonged retention of teeth 61 and 62. Surgical planning was carried out to remove the tumor and the unexfoliated teeth. During the 6-month follow-up of the patient, the eruption of tooth 22 and 21 remained retained, which is under orthodontic follow-up to space maintenance and possible ortho-surgical traction. Therefore, the diagnosis and investigation of clinical and radiographic situations suggestive of odontomas are essential for prevent future damage to permanent teeth.removal of a compound odontoma in a pediatric patient, and from this to elucidate the importance of early diagnosis and treatment. A male patient 8 years old without no eruption of tooth germs 21 and 22 and prolonged retention of teeth 61 and 62. Surgical planning was carried out to remove the tumor and the unexfoliated teeth. During the 6-month follow-up of the patient, the eruption of tooth 22 and 21 remained retained, which is under orthodon tic follow-up to space maintenance and possible ortho-surgical traction. Therefore, the diagnosis and investigation of clinical and radiographic situations suggestive of odontomas are essential for prevent future damage to permanent teeth... (AU)

Immunohistochemical localization of vascular factors in tooth germ of amphibian (Cynops pyrrhogaster) / Localización inmunohistoquímica de factores vasculares en germen dentario de anfibios (Cynops pyrrhogaster)

SUMMARY: Vascular endothelial growth factor (VEGF) and its receptor, VEGFR-2, are known to regulate blood vessel endothelium growth. They play important role in human and rodents teeth development. In newt jaws, there are sequential developmental teeth germs following behind the mature teeth. We examined the immunohistochemical localization of VEGF and its receptor and showed the specific expression pattern of VEGF and VEGF receptor in Cynops pyrrhogaster sequential tooth development. The intensity of immunoreactivity for VEGF in the inner enamel epithelium was weaker than that in the outer enamel epithelium in the dentine matrix formation and mineralization stages. Finally, at the enameloid maturation and enamel-like matrix formation stage, immunoreactivity for VEGF in inner enamel epithelium was stronger than in the outer enamel epithelium. The intensity of immunoreactivity for VEGFR-2 was positive for the outer enamel epithelium throughout tooth development. The crown sides of the odontoblasts were stained especially strongly for VEGF and VEGFR-2 during the dentine matrix formation and mineralization stage of the enameloid maturation and enamel- like matrix formation stage. We postulate that the expression of VEGF in the inner enamel epithelium and odontoblast widely effects tooth development in newts, as well as in human and rodents.

RESUMEN: Se sabe que el factor de crecimiento endotelial vascular (VEGF) y su receptor, VEGFR-2, regulan el crecimiento del endotelio de los vasos sanguíneos. Desempeñan un papel importante en el desarrollo de los dientes humanos y de los roedores. En las mandíbulas de tritón, hay gérmenes dentales de desarrollo secuenciales que siguen a los dientes maduros. Examinamos la localización inmunohistoquímica de VEGF y su receptor y mostramos el patrón de expresión específico de VEGF y receptor de VEGF en el desarrollo secuencial de dientes de Cynops pyrrhogaster. La intensidad de la inmunorreactividad para VEGF en el epitelio interno del esmalte era más débil que en el epitelio externo del esmalte en las etapas de formación y mineralización de la matriz de dentina. Finalmente, en la etapa de maduración del esmalte y de formación de la matriz similar al esmalte, la inmunorreactividad para VEGF en el epitelio interno del esmalte fue más fuerte que en el epitelio externo del esmalte. La intensidad de la inmunorreactividad para VEGFR- 2 fue positiva para el epitelio externo del esmalte durante el desarrollo del diente. Los márgenes de la corona de los odontoblastos se tiñeron especialmente para VEGF y VEGFR-2 durante la etapa de formación de la matriz de dentina y mineralización de la etapa de maduración del esmalte y la etapa de formación de la matriz similar al esmalte. Postulamos que la expresión de VEGF en el epitelio interno del esmalte y odontoblastos afecta ampliamente el desarrollo de los dientes en tritones, así como en humanos y roedores.

Supernumerary teeth in patients with cleft lip and palate: the tooth germs do not separate

ABSTRACT Introduction: Supernumerary teeth in cases of cleft lip and palate do not result from the division of normal germs before the formation of hard tissue. Deciduous and permanent teeth odontogenesis begins after the face has formed, either with or without the cleft. Discussion: The most acceptable hypothesis to enable understanding of the presence of supernumerary teeth on one or both sides of the cleft palate is hyperactivity of the dental lamina in its walls. This hyperactivity, with the formation of more tooth germs, must be attributed to mediators and genes related to tooth formation, under strong influence of local epigenetic factors, whose developmental environment was affected by the presence of the cleft. Conclusion: The current concepts of embryology no longer support the fusion of embryonic processes for the formation of the face, but rather the leveling of the grooves between them. All human teeth have a dual embryonic origin, as they are composed of ectoderm and mesenchyme/ectomesenchyme, but this does not make it easy for them to be duplicated to form supernumerary teeth.

RESUMO Introdução: Os dentes extranumerários nas fissuras labiopalatinas não são resultado da divisão dos germes normais antes da formação do tecido duro. A odontogênese dos decíduos e permanentes inicia-se depois de formada a face, com ou sem fissuras. Discussão: A hipótese mais plausível para compreender a presença dos dentes extranumerários em um ou nos dois lados da fissura labiopalatina é a hiperatividade da lâmina dentária em suas paredes. Essa hiperatividade, com formação de mais germes dentários, deve ser atribuída aos mediadores e genes relacionados à formação dos dentes, sob forte influência de fatores epigenéticos locais, cujo ambiente de desenvolvimento foi afetado pela presença da fissura. Conclusão: Os conceitos atuais da embriologia não fundamentam mais a fusão de processos embrionários para a formação da face, e sim o nivelamento dos sulcos entre eles. Todos os dentes humanos têm uma dupla origem embrionária, pois se compõem de ectoderma e mesênquima/ectomesênquima, mas isso não facilita sua duplicação para formar dentes extranumerários.

Effect of a novel bioceramic root canal sealer on the angiogenesis-enhancing potential of assorted human odontogenic stem cells compared with principal tricalcium silicate-based cements

Abstract Objective: This study evaluated the angiogenesis-enhancing potential of a tricalcium silicate-based mineral trioxide aggregate (ProRoot MTA), Biodentine, and a novel bioceramic root canal sealer (Well-Root ST) in human dental pulp stem cells (hDPSCs), human periodontal ligament stem cells (hPLSCs), and human tooth germ stem cells (hTGSCs). Methodology: Dulbecco's modified Eagle's medium was conditioned for 24 h by exposure to ProRoot MTA, Biodentine, or Well-Root ST specimens (prepared according to the manufacturers' instructions). The cells were cultured in these conditioned media and their viability was assessed with 3-(4,5-dimethyl-thiazol-2-yl)-5-(3-carboxy-methoxy-phenyl)-2-(4-sulfo-phenyl)-2H tetrazolium (MTS) on days 1, 3, 7, 10, and 14. Angiogenic growth factors [platelet-derived growth factor (PDGF), basic fibroblast growth factor (FGF-2), and vascular endothelial growth factor (VEGF)] were assayed by sandwich enzyme-linked immunosorbent assay (ELISA) on days 1, 7, and 14. Human umbilical vein endothelial cell (HUVEC) migration assays were used to evaluate the vascular effects of the tested materials at 6-8 h. Statistical analyses included Kruskal-Wallis, Mann-Whitney U, and Friedman and Wilcoxon signed rank tests. Results: None of tricalcium silicate-based materials were cytotoxic and all induced a similar release of angiogenic growth factors (PDGF, FGF-2, and VEGF) (p>0.05). The best cell viability was observed for hDPSCs (p<0.05) with all tricalcium silicate-based materials at day 14. Tube formation by HUVECs showed a significant increase with all tested materials (p<0.05). Conclusion: The tricalcium silicate-based materials showed potential for angiogenic stimulation of all stem cell types and significantly enhanced tube formation by HUVECs.

Structural characteristics of the deciduous teeth of Tibetan miniature pigs / 南方医科大学学报

OBJECTIVE@#To explore the histological structure of the deciduous teeth and the tooth germs of Tibetan miniature pigs for studies of dental tissue diseases and tooth regeneration.@*METHODS@#The structure of the deciduous teeth of Tibetan miniature pigs was observed by X-ray. The ultrastructure of the enamel and dentin of deciduous teeth was characterized by scanning electron microscopy. The jaws and teeth were three-dimensionally reconstructed using Mimics software based on Micro-CT scanning of the deciduous teeth. Image J software was used to calculate the gray value and the mineralization density of the deciduous teeth. Hisotological structure of the tooth germ and the pulp tissue of Tibetan miniature pigs was observed using HE staining.@*RESULTS@#The deciduous teeth of Tibetan miniature pigs were composed of enamel, dentin and medullary pulp tissue. The permanent tooth germ were formed during the deciduous dentition. The enamel and dentin ultrastructure of deciduous teeth were consistent with that of human deciduous teeth. The enamel and dentin mineralization densities were 2.47±0.09 g/cm and 1.72±0.07 g/cm, respectively. The pathological structures of tooth germ and pulp tissue were similar to those of human teeth, and the pulp tissue of the deciduous teeth was in an undifferentiated state.@*CONCLUSIONS@#The deciduous teeth of Tibetan miniature pig have similar anatomy, ultrastructure and histopathological structure to human teeth and can serve as a good animal model for studying human dental tissue diseases and the mechanisms of tooth regeneration.

Spatio-temporal expression of dentin sialophosphoprotein and collagen Ⅰ during molar tooth germ development in vps4b knockout mouse / 华西口腔医学杂志

OBJECTIVE@#To verify the effect of the mutant gene vps4b on the expression of tooth development-related proteins, dentin sialophosphoprotein (DSPP) and collagenⅠ (COL-Ⅰ).@*METHODS@#Paraffin tissue sections of the first molar tooth germ were obtained from the heads of fetal mice at the embryonic stages of 13.5, 14.5, and 16.5 days and from the mandibles of larvae aged 2.5 and 7 days after birth. The immunohistochemical method was used to detect the expression and location of DSPP and COL-Ⅰ in wild-type mouse and vps4b knockout mouse.@*RESULTS@#DSPP and COL-Ⅰ were not found in the bud and cap stages of wild-type mouse molar germ. In the bell stage, DSPP was positively expressed in the inner enamel epithelium and dental papilla, whereas COL-Ⅰ was strongly expressed in the dental papilla and dental follicle. During the secretory and mineralized periods, DSPP and COL-Ⅰ were intensely observed in ameloblasts, odontoblasts, and dental follicles, but COL-Ⅰ was also expressed in the dental papilla. After vps4b gene knockout, DSPP was not expressed in the dental papilla of the bell stage and in the dental papilla and dental follicle of the secretory phase. The expression position of COL-Ⅰ in the bell and mineralization phase was consistent with that in the wild-type mice. Moreover, the expression of COL-Ⅰ in the dental papilla changed in the secretory stage.@*CONCLUSIONS@#Gene vps4b plays a significant role in the development of tooth germ. The expression of DSPP and COL-Ⅰ may be controlled by gene vps4b and regulates the development of tooth dentin and cementum together with vps4b.

Estudio de la proliferación celular en gérmenes dentarios humanos / Cell proliferation study in human tooth germs

El objetivo de este estudio fue conocer la expresión de MCM4-5-6 en gérmenes dentarios humanos en estado de campana. Materiales y Métodos Se obtuvieron preparados histológicos de 4 maxilares fetales incluidos en parafina en el archivo de bloques de la cátedra de Histología de la Facultad de Odontología, UdelaR. Se procedió al corte de los mismos en secciones para técnica de rutina (HE) y de IHQ para MCM 4, 5 y 6. Resultados: Las diferentes regiones del órgano del esmalte mostraron 100 % de positividad en el estrato intermedio, una variación de 100 % a 0 % en el epitelio interno del órgano del esmalte, desde el sector cervical al sector incisal del mismo, y0% tanto en el retículo estrellado como en el epitelio externo del órgano del esmalte. Conclusiones: Los resultados obtenidos permitieron evidenciar y confirmar la acción proliferativa de las diferentes zonas del órgano del esmalte.

The aim of this study was to determine the expression of MCM4-5-6 in human tooth germs in the bell stage. Materials and methods: Histological samples were collected from four fetal maxillae placed in paraffin at the block archive of the Histology Department of the School of Dentistry, UdelaR. Sections were made for HE routine technique and for immunohistochemistry technique for MCM4-5-6. Results: Different regions of the enamel organ showed 100% positivity in the intermediate layer, a variation from 100% to 0% in the inner epithelium from the cervical loop to the incisal area, and 0% in the stellar reticulum as well as the outer epithelium. Conclusions: The results show and confirm the proliferative action of the different areas of the enamel organ.

Predicción del tercer molar e indicaciones de germenectomía: reporte de un caso / Prediction of the third molar and indications of germectomy: report of a case

Los factores ambientales y evolutivos, los cambios en los hábitos dietéticos, entre otros, pueden desencadenar un papel etiológico en la aparición de anomalías dentales llevando a la especie humana a una disminución en la función masticatoria que trae como consecuencia una reducción en el tamaño de los maxilares originando la falta de espacio para la correcta posición de los dientes en el arco dental, lo que provoca un aumento en la incidencia de casos de segundos y terceros molares retenidos con su consecuente patología multisintomática ocasionando de esta manera un problema de salud pública. Diversos autores han utilizado las imágenes radiográficas para realizar análisis específicamente del tercer molar, basándose en una proyección lateral y panorámica para, mediante marcas y referencias, establecer un diagnóstico y determinar el riesgo y la necesidad de su extracción. La imagenología presenta una nueva herramienta que es la tomografía Cone Beam que nos permite adaptar los conocimientos clásicos del análisis del tercer molar a una imagen en tres dimensiones, aportando el factor profundidad (AU)

Environmental factors, evolutionary changes in dietary habits, among others can trigger an etiological role in the appearance of dental anomalies. Taking the human species to a decrease in masticatory function resulting in a reduction in the size of the jaws, resulting in a lack of space for the correct position of the teeth in the dental arch. Causing an increase in the incidence of second and third molars retained. Its eruption restriction consequent multisymptomatic pathology causing a public health problem in this way. Several authors have used the radiographic images to perform analyzes of the third molar. Based on a lateral and a panoramic radiographic projection, to establish a diagnosis and determine the risk and the need to extract it. Imaging diagnostic presents a new tool that is Cone Beam tomography that allows us to adapt the classical knowledge of the third molar analysis to an image in three dimensions, providing the depth factor (AU)

Aspectos radiográficos de imágenes periapicales asociadas a incisivos primarios traumatizados / Aspectos radiográficos de imagens periapicais associadas a incisivos decíduos traumatizados / Radiographic aspects of periapical images associated with traumatized primary incisors

Las imágenes radiolúcidas periapicales que involucran dientes primarios traumatizados se pueden confundir entre sí y dar lugar a diagnósticos erróneos y tratamiento. Por lo tanto, es importante identi-ficar las características radiográficas de las imágenes radiolúcidas periapicales en los incisivos prima-rios traumatizados, principalmente debido al hecho de que la superposición de imágenes se produce en esta región. Además, es frecuente observar la expansión del folículo haciendo que el diagnóstico radiográfico sea aún más difícil. El objetivo de este estudio fue describir, a través de una revisión de la literatura, las características radiográficas de las imágenes periapicales asociadas con los incisivos primarios traumatizados.

Periapical radiolucencies involving traumatized primary teeth can be confused with each other and lead to misdiagnosis and treatment. Therefore, it is important to identify radiographic characteristics of periapical radiolucent images in traumatized primary incisors, mainly due to the fact that overla-pping of images occurs in this region. Besides, it is frequent to observe follicle expansion making the radiographic diagnosis even more difficult. The objective of this study was to describe, through a literature review, the radiographic characteristics of periapical images associated with traumatized primary incisors.

As radioluscências periapicais envolvendo dentes decíduos traumatizados podem ser confundidas entre si e levar a um erro de diagnóstico e tratamento. Por isso, é importante identificar características radiográficas de imagens radiolúcidas periapicais em incisivos decíduos traumatizados, principalmente pelo fato que nesta região ocorre sobreposição de imagens e, é frequente observar expansão do folículo, dificultando ainda mais o diagnóstico radiográfico. O objetivo deste trabalho foi descrever através de uma revisão de literatura as características radiográficas de imagens periapicais associadas a incisivos decíduos traumatizados.

Remoção de terceiro molar superior deslocado para o espaço bucal / Removal of upper third molar displaced to the buccal space

Os autores descrevem um caso clínico de deslocamento de germe dentário de terceiro molar superior esquerdo para o espaço bucal em um paciente de 13 anos de idade. A localização do dente em posição profunda com envolvimento do corpo adiposo do bucinador dificultou a sua localização, ainda não descrita, nas condições em questão, na literatura. Com a Tomografia Computadorizada de Feixe Cônico (TCFC), foi possível localizar o dente deslocado e planejar a sua remoção. Os riscos e benefícios das extrações de germes de terceiros molares precisam ser avaliados devido ao grande risco de deslocamentos... (AU)

The authors describe a case of displacement of left upper third molar tooth germ to the buccal space in a patient 13 years old. The deep position of the tooth with involvement of the fat body of the buccinator made it difficult its location, still not described, under the concerned conditions, in the literature. With the cone beam computed tomography (CBCT), it was possible determine the location of the tooth and plan his removal. The risks and benefits of third molar tooth germ extraction should be evaluated because there is a greater chance of displacement... (AU)

Tratamiento de marsupialización de un quiste odontogénico inflamatorio en un niño de 5 años con preservación de los gérmenes dentarios permanentes / Marsupialization of a inflammatory dentigerous cyst in a 5-year-old child with preservation of the permanent tooth germs

El quiste radicular ha sido catalogado como un quiste inflamatorio, como resultado de una necrosis pulpar por un proceso de caries, con una reacción inflamatoria periapical. Avanza lentamente y en los primeros estadios puede ser asintomático. Debido a esto pueden tener grandes dimensiones.A continuación, presentamos una situación de un quiste radicular inflamatorio en relación con el segundo molar temporario inferior en un paciente de 5 años de edad. La ortopantomografía muestra una gran radiolucidez unilocular con un borde bien definido en la región periapical del segundo molar temporario inferior que se extiende desde la raíz hasta el primer molar temporario con desplazamientode los gérmenes de los premolares permanentes hacia la basal mandibular del sector derecho.

Differential Expression of Amelogenin, Enamelin and Ameloblastin in Rat Tooth Germ Development

Tooth development shows dynamic morphological changes from the stages of cap to hard tissue formation and is strictly regulated during development. In the present study, we compared expression and localization of 3 major enamel matrix proteins in rats: amelogenin, enamel and ameloblastin. DD-PCR and RT-PCR revealed differential expression of the major proteins from the cap stage to root stage. Immunofluorescence staining results indicated that amelogenin was not detected in either inner enamel epithelium or reduced enamel epithelium, but highly immunoreactive in preameloblasts and ameloblasts; in addition, it was sporadically expressed in preodontoblasts abutting preameloblasts. Ameloblastin expression was also observed in not only differentiated ameloblasts but also osteoblasts. Immunoreactivity to ameloblastin in ameloblasts was strong in Tomes' processes. Enamelin was exclusively localized along the entire newly formed and maturing enamel. Enamelin was largely localized in near Tomes' processes and enamel rods in maturing enamel. Alendronate treatment resulted in down-regulation of amelogenin and ameloblastin at both transcription and translation levels; whereas, enamelin expression was unchanged in response to the treatment. These results suggested that amelogenin, ameloblastin and enamelin might be implicated in cell differentiation, adhesion of ameloblasts to enamel and enamel crystallization during enamel matrix formation, respectively.

Analisis inmunohistoquimico de CK14 y CK19 en germen dentario y ameloblastoma / Immunohistochemical analysis of ck14 and ck19 in tooth germs and ameloblastoma

La odontogénesis es el proceso de formación de los órganos dentarios, en el cual se expresan diversas moléculas, dentro de las cuales encontramos las citoqueratinas 14 y 19 (CK14, CK19). Una vez concluido el proceso de formación del diente quedan restos del epitelio odontogénico, el cual se ha sugerido se encuentra implicado en el desarrollo del ameloblastoma, uno de los tumores odontogénicos más frecuentes. Se ha sugerido que las CK14 y CK19 tienen utilidad como marcadores de diferenciación ameloblástica, y podrían tener implicación dentro del comportamiento tumoral de los ameloblastomas. El objetivo del presente estudio fue describir los patrones de expresión inmunohistoquímica de estas dos citoqueratinas en gérmenes dentarios y ameloblastomas. Materiales y métodos. Se incluyeron 6 ameloblastomas sólidos multiquísticos y 5 gérmenes dentarios a los cuales se les realizó técnica de inmunohistoquímica para CK14 y CK19. Resultados. Este estudio permitió visualizar la inmunoexpresión de CK14 y CK19 en el epitelio y la negatividad en el ectomesénquima, tanto en los gérmenes dentarios como en ameloblastomas. También permitió concluir que CK19 puede ser considerada como un eficiente marcador de diferenciación ameloblástica, mientras que CK14 es gradualmente remplazada por CK19 en el epitelio interno del órgano del esmalte, evidenciándose marcada inmunoexpresión de esta última en ameloblastos secretores...

Introduction. Odontogenesis is the process by which teeth form, and where different molecules are expressed, among them some cytokeratins (CK) like CK14 and CK19. Remnants of odontogenic epithelium may persist once the development process is complete, which has been suggested to be involved in the development of ameloblastoma, one of the most common benign odontogenic tumours. It has been suggested that CK14 and CK19 are useful markers of ameloblast differentiation and that they could have implications for tumour behaviour. The aim of this study is to describe the patterns of immunohistochemical expression of these cytokeratins in tooth germs and ameloblastomas. Materials and methods. We worked with 6 solid multicystic ameloblastomas and 5 tooth germs. The immunohistochemistry technique was used to visualise CK14 and CK19. Results. We detected CK14 and CK19 immunoexpression in the epithelium and no expression in the ectomesenchyme in both tooth germs and ameloblastomas. It was concluded that CK19 can be considered an efficient marker of ameloblast differentiation, whereas CK14 is gradually replaced by CK19 in the inner epithelium of the enamel organ, showing strong immunoexpression in secretory ameloblasts...

The effects of polymeric zinc propylen-bis-dithiocarbamate (Propineb) on tooth development in rats / Efectos del propileno-bis-ditiocarbamato de zinc polimérico (Propineb) sobre el desarrollo de los dientes en ratas

Dithiocarbamate propinebs are organometal fungicides that are widely used for the control of diseases in plants. In this study, pregnant female rats received 400 ppm propineb concentrations in 5 ml distilled water for 16 days of gestation, and then infant rats were obtained by cesarean section. In the histological analysis on the frontal sections, the use of propineb was found effective on odontoblast cell hyperplasia, cell infiltration in the dental papilla, and degeneration in the mesenchymal cells of the outer enamel. The expression of MMP-2 (Matrix Metalloproteinase-2) and VEGF (Endothelial cell growth factor) in the connective tissue was evaluated by immunohistochemistry. The drinking water given to the mothers in propineb tooth bud, enamel and dentin, resulted in morphological changes suggestive of a delay in formation, which cross the placental barrier and possibly affect the tooth development.

Los ditiocarbamatos (Propineb) son fungicidas organometálicos que son ampliamente utilizados para el control de enfermedades en las plantas. En este estudio, ratas hembras preñadas recibieron concentraciones de 4000 ppm de propineb en 5 ml de agua destilada durante 16 días de su gestación. Luego, las crías de las ratas fueron obtenidas mediante cesárea para su estudio estudio histológico. En el análisis histológico de las secciones frontales, el uso de propineb fue positivo para la hiperplasia de las células odontoblástica, infiltración de células en la papila dental, y la degeneración en las células mesenquimales del epitelio externo del esmalte. La expresión de MMP-2 (metaloproteinasa de la matriz 2) y VEGF (factor de crecimiento de células endoteliales) en el tejido conectivo se evaluó por inmunohistoquímica. El agua potable con propineb dada a las madres actuó sobre el brote dentario, esmalte y dentina; se tradujo en cambios morfológicos indicativos de un retraso en la formación. Por tanto, el propineb atraviesa la barrera placentaria y posiblemente afecten el desarrollo de los dientes.

Osteocalcin Expression and Mineralization in Developing Tooth of Xenopus laevis

Osteocalcin (OC) is the most abundant noncollagenous protein of extracellular matrix in the bone. In an OC deficient mouse, bone formation rates are increased in cancellous and cortical bones. OC is known as a negative regulator of mineral apposition. OC is also expressed in the tooth of the rat, bovine, and human. However, little is known about OC during tooth development in Xenopus. The purpose of this study is to compare the expression of OC with mineralization in the developing tooth of Xenopus, by using von Kossa staining and in situ hybridization. At stage 56, the developmental stage of tooth germ corresponds to the cap stage, and an acellular zone was apparent between the dental papilla and the enamel organ. From stage 57, calcium deposition was revealed by von Kossa staining prior to OC expression, and the differentiated odontoblasts forming predentin were located at adjoining predentin. At stage 58, OC transcripts were detected in the differentiated odontoblasts. At stage 66, OC mRNA was expressed in the odontoblasts, which was aligned in a single layer at the periphery of the pulp. These findings suggest that OC may play a role in mineralization and odontogenesis of tooth development in Xenopus.