Effect of dental follicles in minimally invasive open-eruption technique of labially impacted maxillary central incisors / 华西口腔医学杂志

OBJECTIVES@#To summarize the open-eruption technique of impacted anterior maxillary teeth, this study reports a technically improved operation on surgical exposure based on dental follicles and evaluates post-treatment periodontal health considering the effect of dental follicles.@*METHODS@#Patients who underwent open-eruption technique with unilateral labially impacted maxillary central incisors were selected. The impacted teeth were assigned to the experimental group, and the contralateral unimpacted maxillary central incisors were assigned to the control group. In the surgical exposure, the new technique makes use of dental follicles to manage the soft tissue, so as to preserve soft tissue for better aesthetic results and healthier periodontal tissue. Tooth length, root length, alveolar bone loss, and alveolar bone thickness were recorded after the therapy.@*RESULTS@#A total of 17 patients with unilateral maxillary central incisor impaction were successfully treated. The tooth length and root length of the two groups showed a statistically significant difference between the impacted and homonym teeth, with a shorter length in the impacted tooth (P<0.05). More labial alveolar bone loss was found in the experimental group compared with that in the control group (P<0.05). The outcomes of the cementoenamel junction width, pa- latal alveolar bone loss, and alveolar bone thickness did not indicate statistical significance between the experimental and control groups (P>0.05).@*CONCLUSIONS@#In the surgical exposure, the new technique uses dental follicles to manage the soft tissue and preserve it for better aesthetic results and healthier periodontal tissues.

Presencia de lesiones quísticas en sacos pericoronarios de terceros molares mandibulares / Presence of cystic lesions in pericoronary sacs of mandibular third molars

Introducción: a pesar de que un tercer molar no erupcionado repre- senta un riesgo de formación quística, la práctica clínica desestima el análisis histopatológico de los folículos de dichos molares. Objetivo: identificar la frecuencia de lesiones quísticas en los sacos pericoronarios de terceros molares mandibulares. Material y métodos: estudio des- criptivo, transversal, analítico y observacional, en donde se incluyeron sacos pericoronarios de terceros molares mandibulares para su análisis histopatológico, descripción de características clínico-radiográficas y su asociación con la presencia de cambios histológicos o lesiones quís- ticas. Resultados: se incluyeron 48 muestras de sacos pericoronarios, la histopatología de los sacos pericoronarios mostró que 83.3% tenían algún tipo de alteración: 13 quistes paradentales (27.1%), cuatro quistes dentígeros (8.3%), 12 folículos hiperplásicos (25.0%) y 11 folículos inflamados (22.9%). La presencia de lesiones quísticas en la población fue de 35.4%. Se detectó asociación estadísticamente significativa entre el sexo y la presencia de lesiones quísticas (p = 0.039) y entre el nivel de erupción y la presencia de cambios histológicos (p = 0.046). Con- clusiones: la frecuencia de lesiones quísticas o cambios histológicos en folículos de terceros molares mandibulares es alta, principalmente en molares parcialmente erupcionados o submucosos y sin importar la ausencia de sintomatología o alteraciones radiográficas (AU))

Introduction: although a non-erupted third molar represents a risk of cystic formation; clinical practice rejects the histopathological analysis of the follicles of said molars. Objective: identify the frequency of the histopathological changes in pericoronary sacs of mandibular third molars. Material and methods: descriptive cross- sectional, observational and analytic study, where pericoronary sacs of mandibular third molars were included for histopathological analysis, description of clinical-radiographic characteristics and their association with the presence of histological changes or cystic lesions. Results: 48 samples of pericoronary sacs were included, the histopathology of the pericoronary sacs showed 83.3% had some type of alteration: 13 paradental cysts (27.1%), four dentigerous cysts (8.3%), 12 hyperplastic follicles (25.0%) and 11 inflamed follicles (22.9%). The presence of cystic lesions in the population was 35.4%. A statistically significant association was detected between sex and the presence of cystic lesions (p = 0.039); and between the level of eruption and the presence of histological changes (p = 0.046). Conclusions: the frequency of cystic lesions or histological changes in mandibular third molar follicles is high, mainly in partially erupted or submucosal molars and regardless of the absence of symptoms or radiographic alterations (AU)

Terceiro molar superior impactado invertido: relato de caso / Invert impacted superior third molar: case report

Introdução: A impactação invertida dos dentes é raro, correspondendo a menos de 1% dos casos de terceiros molares impactados na maxila. O elemento dentário afetado pode permanecer por longos períodos sem apresentar sintomatologia, entretanto, podem provocar problemas dentários e desenvolvimento de patologias dos maxilares. O tratamento cirúrgico é proposto em casos em que o folículo dentário se apresentar patologicamente afetado, ou necessidade estética, funcional e/ou comportamental. Relato de caso: Paciente do sexo feminino, leucoderma, 35 anos, ASA I, procurou atendimento na Clínica Escola de Odontologia da Universidade Estadual da Paraíba, UEPB, Campus VIII em Araruna/ PB, queixando-se da presença de quadros de sintomatologia dolorosa na região direita da maxila. Por meio da avaliação clínico-radiográfica concluiu-se que a impactação invertida do elemento 18 era responsável por originar os episódios de dor. Devido a isto e com a finalidade de prevenir o desencadeamento de complicações futuras, optou-se, pela remoção cirúrgica do dente. Considerações finais: A exodontia de dentes invertidos - quando indicada - se configura como uma técnica cirúrgica eficiente. Assim, uma vez optada pela intervenção cirúrgica, o profissional deve realizar um planejamento minucioso da técnica operatória... (AU)

Introduction: Inverted impaction of teeth is rare, corresponding to less than 1% of cases of third molars impacted on the maxilla. The affected dental element can remain for long periods without presenting symptoms, however, they can cause dental problems and the development of pathologies of the jaws. Surgical treatment is proposed in cases where the dental follicle is pathologically affected, or has an aesthetic, functional and/or behavioral need. Case report: Female patient, leucoderma, 35 years old, ASA I, sought care at the Dental School Clinic of the State University of Paraíba, UEPB, Campus VIII in Araruna/PB, complaining of the presence of painful symptoms in the right region of the maxilla. Through clinical-radiographic evaluation, it was concluded that the inverted impaction of element 18 was responsible for causing episodes of pain. Because of this and in order to prevent the triggering of future complications, we opted for surgical removal of the tooth. Final considerations: The extraction of inverted teeth - when indicated - is an efficient surgical technique. Thus, once opted for surgical intervention, the professional must carry out a thorough planning of the operative technique... (AU)

Avaliação das alterações moleculares dos folículos dentários em relação à idade cronológica / Evaluation of molecular changes in dental follicles in relation to chronological age

O Folículo dental (FD) é um tecido de origem ectomesenquimal. Aproximadamente 57% dos adultos apresentam terceiro molar mandibular impactado, sendo esse elemento dentário com maior prevalência de impactação dental. Há maior incidência de alterações patológicas em indivíduos mais velhos em comparação com indivíduos mais jovens. Porém os mecanismos envolvidos na formação de cistos e tumores relacionados aos FDs não estão bem elucidados, e, por isso, alguns autores defendem a extração profilática dos terceiros molares inclusos. Durante o envelhecimento cronológico, padrões epigenéticos mudam, e um padrão de hipometilação global do DNA pode ser encontrado concomitantemente com hipermetilação de vários genes supressores tumorais. A metilação do DNA é um dos mecanismos que regula as vias de sinalização celular, como a da MAPK/ERK, que atuam no controle da proliferação e diferenciação. Alguns pesquisadores descobriram um aumento na atividade do ERK 1/2 durante o processo de envelhecimento, o que poderia contribuir para a ocorrência de doenças, e a sua desregulação está envolvida na indução e na progressão de doenças como câncer e doenças autoimunes. Portanto, o presente estudo teve por objetivo avaliar se os FDs de indivíduos jovens e indivíduos mais velhos apresentam diferença no perfil de metilação global do DNA, e avaliar o padrão de imunoexpressão da forma fosforilada ERK1/2 (pERK1/2) nos FDs. A metilação global do DNA (percentual de 5mC) e a hidroximetilação (5hmC) foram avaliadas por ELISA em 59 amostras. Testamos a correlação entre o conteúdo de 5mC e 5hmC e a correlação de cada um com a idade dos pacientes. Examinamos a imunorreatividade do pERK 1/2 para avaliar a ativação das vias MAPK/ERK em 46 amostras de FD. As amostras apresentaram variação entre 13 e 31 anos de idade. Os resultados mostraram uma relação inversamente proporcional entre o conteúdo de 5hmC e idade até os 19 anos, portanto o percentual de 5hmC nos FDs tende a diminuir linearmente com o envelhecimento. O estudo imuno-histoquímico mostrou um padrão variável de imunoexpressão de pERK1/2 com 46% (21/46) das amostras exibindo menos de 10% de células positivas, enquanto 24% (11/46) das amostrasapresentaram imunopositividade entre 10 e 50% e 30% (14/46) das amostras mais de 50% das células de FD. Não foi observado diferença nas idades entre esses grupos. Em conclusão, nossos resultados sugerem que a hidroximetilação global do DNA possui alteração no seu padrão durante o envelhecimento e que a via de sinalização celular MAPK/ERK está ativa nos FDs.

The dental follicle (DF) is a tissue of ectomesenquimal origin. Approximately 57 % of young adults have impacted third molars, which is the most prevalent impacted tooth. The incidence of pathological changes is greater among older individuals than younger individuals. However, the mechanisms behind the formation of cysts and tumors related to DFs have not been fully clarified and, therefore, some researchers defend the prophylactic extraction of third molars. During chronological aging, epigenetic patterns change and a global DNA hypomethylation pattern can be found concomitantly with hypermethylation of several tumor suppressor genes. DNA methylation is one of the regulators of cell signaling pathways, such as the MAPK/ERK pathway. Some researchers have found an increase in ERK1/2 activity during the aging process, which may contribute to the occurrence of disease, and its dysregulation is involved in the induction and progression of diseases such as cancer and autoimmune diseases. Thus, the aim of the present study was to evaluate whether DFs in young and older individuals differ in terms of global methylation and hydroxymethylation and to evaluate the immunoexpression pattern of phosphorylated ERK1/2. Global DNA methylation (5mC content) and hydroxymethylation (5hmC) were evaluated by ELISA in 59 DF samples We tested the correlation between 5mC and 5hmC content, and the correlation of each with patients' age. We examined ERK1/2 immunoreactivity for the evaluation of the activation of the MAPK pathways in 46 DF samples. Age of patients of the 59 samples of DFs raged from 13 to 31 years. An inversely proportional relation was found between the 5hmC content and age up to 19 years, therefore, the percentage of 5hmC in the DFs tends linearly decrease with aging. The immunohistochemical study showed a variable pattern of immunoexpression of pERK 1/2 with 46% (21/46) of the samples showing less than 10% of positive cells, while 24% (11/46) of the samples showed immunopositivity between 10 and 50% and 30% (14/46) of the samples greater than 50% of the DF cells. There was no difference in age among these groups. In conclusion, our results suggest that the global hydroxymethylation of DNA changes in its pattern during aging and that the MAPK/ERK cell signaling pathway is active in DFs.

AFF4 regulates osteogenic differentiation of human dental follicle cells / 国际口腔科学杂志·英文版

As a member of the AFF (AF4/FMR2) family, AFF4 is a transcription elongation factor that is a component of the super elongation complex. AFF4 serves as a scaffolding protein that connects transcription factors and promotes gene transcription through elongation and chromatin remodelling. Here, we investigated the effect of AFF4 on human dental follicle cells (DFCs) in osteogenic differentiation. In this study, we found that small interfering RNA-mediated depletion of AFF4 resulted in decreased alkaline phosphatase (ALP) activity and impaired mineralization. In addition, the expression of osteogenic-related genes (DLX5, SP7, RUNX2 and BGLAP) was significantly downregulated. In contrast, lentivirus-mediated overexpression of AFF4 significantly enhanced the osteogenic potential of human DFCs. Mechanistically, we found that both the mRNA and protein levels of ALKBH1, a critical regulator of epigenetics, changed in accordance with AFF4 expression levels. Overexpression of ALKBH1 in AFF4-depleted DFCs partially rescued the impairment of osteogenic differentiation. Our data indicated that AFF4 promoted the osteogenic differentiation of DFCs by upregulating the transcription of ALKBH1.

VPS4B mutation impairs the osteogenic differentiation of dental follicle cells derived from a patient with dentin dysplasia type I / 国际口腔科学杂志·英文版

A splicing mutation in VPS4B can cause dentin dysplasia type I (DD-I), a hereditary autosomal-dominant disorder characterized by rootless teeth, the etiology of which is genetically heterogeneous. In our study, dental follicle cells (DFCs) were isolated and cultured from a patient with DD-I and compared with those from an age-matched, healthy control. In a previous study, this DD-I patient was confirmed to have a loss-of-function splicing mutation in VPS4B (IVS7 + 46C > G). The results from this study showed that the isolated DFCs were vimentin-positive and CK14-negative, indicating that the isolated cells were derived from the mesenchyme. DFCs harboring the VPS4B mutation had a significantly higher proliferation rate from day 3 to day 8 than control DFCs, indicating that VPS4B is involved in cell proliferation. The cells were then replenished with osteogenic medium to investigate how the VPS4B mutation affected osteogenic differentiation. Induction of osteogenesis, detected by alizarin red and alkaline phosphatase staining in vitro, was decreased in the DFCs from the DD-I patient compared to the control DFCs. Furthermore, we also found that the VPS4B mutation in the DD-I patient downregulated the expression of osteoblast-related genes, such as ALP, BSP, OCN, RUNX2, and their encoded proteins. These outcomes confirmed that the DD-I-associated VPS4B mutation could decrease the capacity of DFCs to differentiate during the mineralization process and may also impair physiological root formation and bone remodeling. This might provide valuable insights and implications for exploring the pathological mechanisms underlying DD-I root development.

Why canines induce resorption of neighboring roots? An imaging correlation

ABSTRACT Despite the explanations about the mechanisms and reasons why dental follicles of unerupted maxillary canines do not cause root resorption in neighboring teeth, questions remain about the time expected for this event and the lack of protocols for preventive clinical management, which may serve as insights for further studies. Here, these mechanisms are correlated with imaging findings of CT scans and 3D reconstructions of a typical clinical case.

RESUMO Apesar das explicações dos mecanismos e dos porquês os folículos pericoronários dos caninos superiores não irrompidos podem reabsorver as raízes dos dentes vizinhos, questiona-se a inexistência de previsibilidade do tempo em que isso ocorre e a ausência de protocolos de condutas clínicas preventivas, como insights para novas pesquisas. Correlaciona-se, também, esses mecanismos com os aspectos imaginológicos de cortes tomográficos e reconstruções 3D de um caso clínico característico.

Three-Dimensional Spheroid Formation of Cryopreserved Human Dental Follicle-Derived Stem Cells Enhances Pluripotency and Osteogenic Induction Properties

BACKGROUND: Enhancement and maintenance of the stemness of mesenchymal stem cells (MSCs) is one of the most important factors contributing to the successful in vivo therapeutic application of these cells. In this regard, three-dimensional (3D) spheroid formation has been developed as reliable method for increasing the pluripotency of MSCs. Moreover, using a new protocol, we have previously shown that dental tissues of extracted wisdom teeth can be effectively cryopreserved for subsequent use as a source of autologous stem cells. The main purpose of this study is to analyze the stemness and in vitro osteogenic differentiation potential of 3D spheroid dental MSCs compared with conventional monolayer cultured MSCs. METHODS: In this study, MSC-characterized stem cells were isolated and cultured from long-term cryopreserved dental follicles (hDFSCs), and then 2D hDFSCs were cultured under 3D spheroid-forming conditions using a newly designed microchip dish. The spheroids (3D hDFSCs) thus produced were investigated and characterized with respect to stemness, MSC marker expression, apoptosis, cell cycle analysis, extracellular matrix (ECM) production, and osteogenic and adipogenic differentiation properties. RESULTS: In terms of MSC and senescence markers, spheroid cells showed no difference when compared with 2D hDFSCs; however, 3D hDFSCs were observed to have a higher proportion of cell cycle arrest and a larger number of apoptotic cells. Moreover, spheroids showed substantially increased levels of pluripotency marker (early transcription factors) and ECM protein expression. Compared with 2D hDFSCs, there was also a notable enhancement in the osteogenic induction potential of spheroids, although no differences were observed with respect to in vitro adipogenesis. CONCLUSION: To the best of our knowledge, this is the first study to demonstrate the application of a spheroid culture system for dental follicle-derived stem cells using a microchip dish. Although further studies are needed, including in vivo transplantation, the results obtained in this study indicate that spheroid hDFSCs derived from cryopreserved dental follicle tissues could be used as a valuable source of autologous stem cells for bone tissue regeneration.

Low-intensity pulsed ultrasound promotes tissue regeneration in rat dental follicle cells in a porous ceramic scaffold

Abstract The aim of this study was to investigate the effects of low-intensity pulsed ultrasound (LIPUS) on the osteogenic differentiation of dental follicle cells (DFCs) in vitro and on the regenerative effects of DFC-OsteoBoneTM complexes in vivo. DFCs were isolated and characterized. In the in vitro study, DFCs were cultured in an osteogenic medium in the presence or absence of LIPUS. The expression levels of ALP, Runx2, OSX, and COL-I mRNA were analyzed using real-time polymerase chain reaction (RT-PCR) on day 7. Alizarin red staining was performed on day 21. The state of the growth of the DFCs that were seeded on the scaffold at 3, 5, 7, and 9 days was detected by using a scanning electron microscope. In our in vivo study, 9 healthy nude mice randomly underwent subcutaneous transplantation surgery in one of three groups: group A, empty scaffold; group B, DFCs + scaffold; and group C, DFCs + scaffold + LIPUS. After 8 weeks of implantation, a histological analysis was performed by HE and Mason staining. Our results indicate that LIPUS promotes the osteogenic differentiation of DFCs by increasing the expression of the ALP, Runx2, OSX, and COL-I genes and the formation of mineralized nodules. The cells can adhere and grow on the scaffolds and grow best at 9 days. The HE and Mason staining results showed that more cells, fibrous tissue and blood vessels could be observed in the DFCs + scaffold + LIPUS group than in the other groups. LIPUS could promote the osteogenic differentiation of DFCs in vitro and promote tissue regeneration in a DFCs-scaffold complex in vivo. Further studies should be conducted to explore the underlying mechanisms of LIPUS.

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.

TGF-β2 downregulates osteogenesis under inflammatory conditions in dental follicle stem cells / 国际口腔科学杂志·英文版

Bone formation is important for the reconstruction of bone-related structures in areas that have been damaged by inflammation. Inflammatory conditions such as those that occur in patients with rheumatoid arthritis, cystic fibrosis, and periodontitis have been shown to inhibit osteoblastic differentiation. This study focussed on dental follicle stem cells (DFSCs), which are found in developing tooth germ and participate in the reconstruction of alveolar bone and periodontal tissue in periodontal disease. After bacterial infection of inflamed dental tissue, the destruction of bone was observed. Currently, little is known about the relationship between the inflammatory environment and bone formation. Osteogenic differentiation of inflamed DFSCs resulted in decreased alkaline phosphatase (ALP) activity and alizarin red S staining compared to normal DFSCs. Additionally, in vivo transplantation of inflamed and normal DFSCs demonstrated severe impairment of osteogenesis by inflamed DFSCs. Protein profile analysis via liquid chromatography coupled with tandem mass spectrometry was performed to analyse the differences in protein expression in inflamed and normal tissue. Comparison of inflamed and normal DFSCs showed significant changes in the level of expression of transforming growth factor (TGF)-β2. Porphyromonas gingivalis (P.g.)-derived lipopolysaccharide (LPS) was used to create in vitro inflammatory conditions similar to periodontitis. The osteogenic differentiation of LPS-treated DFSCs was suppressed, and the cells displayed low levels of TGF-β1 and high levels of TGF-β2. DFSCs treated with TGF-β2 inhibitors showed significant increases in alizarin red S staining and ALP activity. TGF-β1 expression was also increased after inhibition of TGF-β2. By examining inflamed DFSCs and LPS-triggered DFSCs, these studies showed both clinically and experimentally that the increase in TGF-β2 levels that occurs under inflammatory conditions inhibits bone formation.

Neurotrophin 3 promotes osteogenic differentiation of human dental follicle cells / 华西口腔医学杂志

OBJECTIVE@#This study aims to investigate the effect of neurotrophin 3 (NT-3) on the osteogenic differentiation of human dental follicle cells (hDFCs).@*METHODS@#hDFCs were isolated and cultured in vitro. Immunocytochemical staining was used to identify the origin of hDFCs. The effects of different NT-3 concentrations on hDFCs proliferation were detected by using CCK-8 assay. The alkaline phosphatase (ALP) activities and mRNA expression levels of bone morphogenetic protein-2 (BMP-2) and osteocalcin (OCN) were determined to investigate the effects of NT-3 on hDFCs osteogenesis. The difference in the number of mineralized nodules was detected using alizarin red staining.@*RESULTS@#Vimentin and cytokeratin staining results showed that hDFCs originated from the mesenchymal cells. NT-3 exerted no evident effect on hDFCs proliferation. The ALP activity and the BMP-2 and OCN mRNA expression levels of hDFCs were significantly improved under treatment with different NT-3 concentrations (25, 50, and 100 ng·mL ⁻¹) compared with those in the control group. BMP-2 and OCN mRNA relative expression levels of hDFCs reached the highest when the NT-3 concentration was 100 ng·mL ⁻¹. The number of mineralized nodules reached the maximum when the hDFCs were treated with 50 and 100 ng·mL ⁻¹ NT-3.@*CONCLUSIONS@#Appropriate mass concentration of NT-3 can promote the osteogenic differentiation of hDFCs.

Retrospective Analysis of Incisor Root Resorption Associated with Impacted Maxillary Canines / 대한소아치과학회지

Root resorption of the permanent maxillary incisors can occur due to ectopic eruption of the permanent canines. Severe root resorption threatens the long-term survival of the affected incisors. The aim of the present study was to identify risk factors for root resorption of the maxillary incisors associated with impacted maxillary canines. In the present study, we retrospectively analyzed the Cone-Beam Computed Tomography (CBCT) scans of 65 children and adolescents with ectopically erupting maxillary canines (total of 88 impacted canines). Root resorption of central incisors was significantly associated with the mesiodistal position and root development of the adjacent canine. Root resorption of lateral incisors was significantly associated with sex, age, and the buccolingual and vertical position of the adjacent canine. However, enlargement of the dental follicle was not significantly associated with root resorption of adjacent incisors. Although incisor resorption is difficult to diagnose and predict, our findings suggest that changes in the dental follicles of the erupting maxillary canines do not cause resorption of the adjacent permanent incisors. CBCT should be utilized to ensure early diagnosis of impacted canines and precise evaluation of incisor root resorption.

Histopathological evaluation of dental follicles associated with impacted third molars

Aim: To histologically evaluate dental follicles of impacted third molars with no radiographic evidence of pathology. Methods: We carried out both a quantitative and qualitative analysis of pericoronal follicles removed from impacted third molars and investigated the association with clinical data. The sample included 36 extracted dental follicles of impacted third molars, obtained from 28 patients, which presented with no radiographic evidence of pathologies. Results: None of the follicles analyzed showed any pathological entity. The epithelial lining was observed in 61.1% of samples, being identified as reduced enamel epithelium. We found a significant relation between the the presence of inflammatory infiltrate and the group aged over 21 years (64.3%; p<0.05). Conclusions: Considering the absence of pathological lesions, we suggest that impacted third molars should only be extracted in young-aged individuals due to specific pathologies or indications

Effect of hypoxia on the biological characteristics of human dental follicle cells / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This study aimed to investigate the effects of hypoxia on the characteristics of human dental follicle cells (hDFCs).</p><p><b>METHODS</b>The tissue explant collagenase method was used to isolate hDFCs from young permanent teeth. The immunofluorescence technique was used to detect cell surface markers, and the multi-differentiation potential was detected by multilineage differentiation induction assay. Then, the hypoxic microenvironment was physically mimicked, and the cells were divided into the normoxia group (20%O₂) and the hypoxia group (2%O₂). The effects of hypoxia on cell migration and proliferation were examined by Transwell chamber test and CCK-8 assay, respectively. The gene and protein expression levels of stemness-related markers at both oxygen concentrations were measured by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot, respectively. After osteogenic induction of both groups, qRT-PCR was performed to evaluate the osteogenesis-related gene, and alizarin red staining was used to assess the formation of mineralized nodules.</p><p><b>RESULTS</b>With the multi-differentiation capacity of osteogenic cells, adipogenic cells, and nerves, hDFCs demonstrate strong stem cell characteristics and possess the criteria of mesenchymal stem cells, which can meet the requirements of seed cells in dental tissue engineering. Hypoxia was conducive to the maintenance of hDFC stemness. Hypoxia promoted the migration and proliferation of hDFCs. The hDFCs were induced to osteogenic differentiation under hypoxic conditions, thereby enhancing osteogenesis.</p><p><b>CONCLUSIONS</b>Hypoxic microenvironment plays an important role in maintaining the stemness and promoting the proliferation, migration, and differentiation of hDFCs. Thus, this microenvironment could also serve several important functions in future clinical applications.</p>

Comparative in vitro evaluation of human dental pulp and follicle stem cell commitment

Objective: Pulp and periodontal tissues are well-known sources of mesenchymal stem cells [MSCs] that provide a promising place in tissue engineering and regenerative medicine. The molecular mechanisms underlying commitment and differentiation of dental stem cells that originate from different dental tissues are not fully understood. In this study, we have compared the expression levels of pluripotency factors along with immunological and developmentally-related markers in the culture of human dental pulp stem cells [hDPSCs], human dental follicle stem cells [hDFSCs], and human embryonic stem cells [hESCs]

Materials and Methods: In this experimental study, isolated human dental stem cells were investigated using quantitative polymerase chain reaction [qPCR], immunostaining, and fluorescence-activated cell sorting [FACS]. Additionally, we conducted gene ontology [GO] analysis of differentially expressed genes and compared them between dental stem cells and pluripotent stem cells

Results: The results demonstrated that pluripotency [OCT4 and SOX2] and immunological [IL-6 and TLR4] factors had higher expressions in hDFSCs, with the exception of the JAGGED-1/NOTCH1 ratio, c-MYC and NESTIN which expressed more in hDPSCs. Immunostaining of OCT4, SOX2 and c-MYC showed cytoplasmic and nucleus localization in both groups at similar passages. GO analysis showed that the majority of hDFSCs and hDPSCs populations were in the synthesis [S] and mitosis [M] phases of the cell cycle, respectively

Conclusion: This study showed different status of heterogeneous hDPSCs and hDFSCs in terms of stemness, differentiation fate, and cell cycle phases. Therefore, the different behaviors of dental stem cells should be considered based on clinical treatment variations

Research progress on the cellular and molecular mechanisms of tooth eruption / 华西口腔医学杂志

Tooth eruption is a series of complicated physiological processes occurring once the crown is formed completely, as well as when the tooth moves toward the occasion plane. As such, the tooth moves through the alveolar bone and the oral mucosa until it finally reaches its functional position. Most studies indicate that the process of tooth eruption involves the alveolar bone, dental follicles, osteoclasts, osteoblasts, and multiple cytokines. Dental follicles regulate both resorption and formation of the alveolar bone, which is required for tooth eruption. Furthermore, root formation with periodontal ligament facilitates continuous tooth eruption. However, the exact mechanism underlying tooth eruption remains unclear. Hence, this review describes the recent research progress on the cellular and molecular mechanisms of tooth eruption.

Expression and significance of wingless-type MMTV integration site family, member 5A/receptor tyrosine kinase-like orphan receptor 2 in the rat dental follicle / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To observe the expression of wingless-type MMTV integration site family, member 5A (Wnt5A)/receptor tyrosine kinase-like orphan receptor 2 (Ror2) signal in the dental follicle cells during the normal eruption of the teeth as well as to explore the relationship between the expression of dental follicle cells and the formation of mature osteoclasts and eruption of the teeth.</p><p><b>METHODS</b>The mandibulars of 1-13 d old SD rats were separated to observe the growth and develop-ment of the teeth and alveolar bone through hematoxylin-eosin(HE) staining. Ror2 and Wnt5A expressions in rat dental follicle were also observed through immunohistochemistry. Dental follicle cells from the lower first intact molar germs of 5-6-day old SD rats were separated and cultured.</p><p><b>RESULTS</b>On the second day after birth, the dental follicle began to differentiate into periodontal tissues, but no obvious changes were observed in the alveolar bone one to three days after birth. On the fourth day, the number of osteoclasts increased significantly. The results of immunohistochemistry showed that Wnt5A was not significantly expressed in rat dental follicle tissues before the fourth day, but positive expression was expressed in the next day and continued to express to thirteenth days. Ror2 was expressed in the rat dental follicle at postnatal days 1-3, but weak expression was found in days 4-13.</p><p><b>CONCLUSIONS</b>Wnt5A and Ror2 expressions in the process of tooth eruption have specific time distributions, suggesting that these expressions may participate in the regulation of the eruption of the teeth.</p>

Orthodontic movement in deciduous teeth

Deciduous teeth exfoliate as a result of apoptosis induced by cementoblasts, a process that reveals the mineralized portion of the root while attracting clasts. Root resorption in deciduous teeth is slow due to lack of mediators necessary to speed it up; however, it accelerates and spreads in one single direction whenever a permanent tooth pericoronal follicle, rich in epithelial growth factor (EGF), or other bone resorption mediators come near. The latter are responsible for bone resorption during eruption, and deciduous teeth root resorption and exfoliation. Should deciduous teeth be subjected to orthodontic movement or anchorage, mediators local levels will increase. Thus, one should be fully aware that root resorption in deciduous teeth will speed up and exfoliation will early occur. Treatment planning involving deciduous teeth orthodontic movement and/or anchorage should consider: Are clinical benefits relevant enough as to be worth the risk of undergoing early inconvenient root resorption?.

O dente decíduo é esfoliado graças à apoptose em seus cementoblastos, que desnuda a parte mineralizada da raiz e atrai os clastos. A rizólise é lenta, pois faltam mediadores em quantidade para acelerar o processo, mas ela se acelera e unidireciona quando se aproxima um folículo pericoronário de dente permanente rico em EGF e outros mediadores da reabsorção óssea - os responsáveis pelas reabsorções óssea na erupção e dentária decídua na rizólise e esfoliação. Se houver movimentação ortodôntica ou ancoragem em dentes decíduos, aumenta-se, também, o nível local desses mesmos mediadores, devendo-se estar bem consciente de que haverá uma aceleração da rizólise e, em decorrência, uma antecipação de sua esfoliação. No planejamento de casos em que dentes decíduos estejam envolvidos na movimentação ortodôntica e/ou ancoragem, deve-se ponderar: o benefício clínico para o paciente será relevante, a ponto de valer o risco de uma rizólise abreviada e inconveniente?.

Incidência de anormalidades histológicas em tecido correspondente ao espaço pericoronário de terceiros molares inclusos e semi-inclusos / Incidence of the soft tissue changes around unerupted or impacted third molars

Introdução: O Folículo Pericoronário envolve a coroa do germe dental durante seu desenvolvimento. Quando o dente permanece incluso, alterações do folículo podem originar doenças, como cistos e tumores odontogênicos. Objetivo: Analisar as alterações histológicas no tecido mole circundante a terceiros molares inclusos e semi-inclusos, independentemente de alterações patológicas aparentes em suas radiografias correspondentes, além de relacionar o diagnóstico histológico com o diagnóstico radiográfico dos casos. Material e Método: A partir de terceiros molares extraídos de 26 pacientes, foram analisados espécimes histológicos de folículos pericoronários por dois examinadores calibrados. O diagnóstico histopatológico obtido foi relacionado ao radiográfico, sendo este realizado por meio de radiografias periapicais e, quando necessário, complementado por radiografias panorâmicas. Resultado: Dos 37 folículos pericoronários avaliados, 30% mostraram alterações histológicas compatíveis com cistos dentígeros; 51% eram folículos normais, e 19% continham apenas fragmentos de mucosa. Radiograficamente, 100% dos casos demonstraram características de folículos sem alterações. Conclusão: Esses dados exemplificam que anormalidades podem estar presentes nos tecidos pericoronários sem que haja evidências clínicas e radiográficas. O exame histopatológico provê um diagnóstico mais preciso e deve ser considerado para a construção do diagnóstico definitivo. .

Introduction: Dental follicles remain adjacent to the crown of an unerupted or impacted tooth. Changes in dental follicles can occur and form a solitary cyst around the crown of the tooth, deemed dentigerous cysts. Objective: The aim of this study was to determine the incidence of soft tissue changes around unerupted or impacted third molars. Material and Method: Pericoronal tissue of patients who were referred to our clinic for removal of third molars for a variety of reasons was examined histopathologically. Follicular spaces were measured from periapical and panoramic radiographs by each author independently. Result: Of the 37 specimens submitted for histopathologic examination, 19 normal follicular tissues (51%), 11 arrangements typical of a cyst (30%) and 7 normal tissues of oral mucous (11%) were found. Conclusion: Cystic changes may be encountered in the histopathologic examination of radiographically normal unerupted or impacted third molar follicles. .