Prevalence and predisponent factors of molar-incisor hypomineralization in primary dentition

Aim: To evaluate the prevalence and predisposing factors for hypomineralization of second molars in children in primary dentition. Methods: A questionnaire was applied to parents to analyze predisposing factors and to assist in the diagnosis of hypomineralization in children between 2 and 6 years old, followed by an intraoral examination based on indices of non-fluorotic enamel defects in the primary dentition, according to the "Modified Index DDE" to determine demarcated opacity and HSPM presence / severity index to assess hypomineralization. Children from public and private schools were dived into two groups: if they presented HSPM-Group 1 (G1) and if they did not have HSPM-Control group (CG). Results: The most frequent predisposing factors associated with the child were Illness in the first year of life (X2= 6.49; p=0.01) and antibiotic use in the first year of life (X2= 41.82; p= 0.01). The factors associated with the mother were hypertension (X2= 9.36; p=0.01), infections during pregnancy (X2=14.80; p=0.01) and alcohol consumption during pregnancy (X2=97.33; p=0.01). There was a prevalence of 3.9% of HSPM in 14 children, with statistical difference regarding gender (X2 = 4.57; p <0.05), with boys presenting a higher frequency. In G1 hypomineralization was of the type with demarcated opacity, with more prevalent characteristics the yellowish spot, with moderate post-eruptive fracture and acceptable atypical restorations. All lesions were located in the labial region with 1/3 of extension. Conclusion: The prevalence of HSPM in children between 2 and 6 years old was 3.9%, with a predominance in males, with tooth 65 being the most affected. There was an association between HSPM and infection in the first year of life, as well as the use of antibiotics and sensitivity in the teeth affected by the lesion. There was an association between HSPM and hypertension, infection and mothers' alcohol use during pregnancy

Clinical and Molecular Disorders Caused by COVID-19 During Pregnancy as a Potential Risk for Enamel Defects

ABSTRACT This paper discusses the potential risk that COVID-19 generates for the development of enamel defects. This hypothesis was built based on the etiopathogenesis of enamel defects and the relationship with the symptom's characteristic of COVID-19. Pregnancy is a critical period for the child's development; exposure to pathological agents can cause systemic imbalances and risks of adverse perinatal and prenatal outcomes. The main clinical symptoms of this disease and its association with that dental outcome were considered. Fever, breathing, cardiovascular disorders, and diarrhea were related as potential etiological factors of ameloblast metabolism imbalance, which can interfere qualitatively and quantitatively in the development, maturation and mineralization of the tooth enamel. Molecular disorders derived from COVID-19, as well as their clinical symptoms, can be considered potential risk factors for the development of enamel defects. Individuals with enamel defects experienced high stress levels during pregnancy or early childhood. The approach adopted may help build new research to ensure understanding of the etiology of the development of dental enamel defects and its relationship with COVID-19. However, longitudinal studies need to be conducted to confirm the association between COVID-19 and adverse events during pregnancy.

Oral manifestations of renal tubular acidosis associated with secondary rickets: case report / Manifestações bucais da acidose tubular renal associada ao raquitismo secundário: relato de caso

ABSTRACT This report describes the oral manifestations of renal tubular acidosis (RTA) associated with secondary rickets and discusses the biological plausibility of these findings. The characteristic electrolyte changes during RTA or genetic mutations that trigger RTA may be responsible for impaired amelogenesis, dental malocclusion, impacted teeth, and absent lamina dura. This report reinforces the possibility of an association between RTA and the oral manifestations described.

RESUMO Este relato de caso descreve as manifestações bucais da acidose tubular renal (ATR) associada ao raquitismo secundário e discute a plausibilidade biológica desses achados. As alterações eletrolíticas características da ATR ou as mutações genéticas que a desencadeiam podem ser responsáveis pela amelogênese imperfeita, maloclusão dentária, dentes impactados e ausência de lâmina dura. Este relato reforça a possibilidade de uma associação entre ATR e as manifestações bucais descritas.

Estudo morfológico do efeito do trauma mecânico sobre a amelogênese em incisivos de ratos / Morphological study of the effect of mechanical trauma on amelogenesis in rat incisors

Introdução: a amelogênese compreende a formação do esmalte por células especializadas denominadas ameloblastos. Os ameloblastos secretam proteínas da matriz e são responsáveis pela criação de um ambiente extracelular que favorece a mineralização do esmalte. Contudo, diversos fatores, como o trauma dentário, podem interferir na amelogênese, contribuindo para a formação de um esmalte defeituoso. O trauma dentário tem sido responsável por muitos casos de hipoplasia que podem fragilizar o dente, além de trazer desconforto estético. Objetivo: examinar as alterações morfológicas sobre o epitélio odontogênico e a matriz de esmalte de incisivos de ratos, produzidas por um trauma dentário. Metodologia: incisivos de ratos foram extruídos e depois reposicionados em seus alvéolos originais. Decorridos 3, 7, 10, 20, 30 e 60 dias do procedimento cirúrgico, os dentes foram fixados em uma solução de formaldeído e glutaraldeído, processados histologicamente e corados com azul de toluidina. Resultados: a análise morfológica revelou a formação de uma matriz de esmalte bastante heterogênea, com espessura irregular, particularmente na porção mais apical dos incisivos. Algumas matrizes de esmalte expostas mostravam pequenas lacunas de reabsorção, muitas vezes com deposição de um material cementoide. Conclusão: o presente estudo mostrou que o trauma foi suficiente para produzir alterações hipoplásicas e de hipomineralização importantes no esmalte que se relacionaram com a fase funcional dos ameloblastos na região afetada.

Introduction: amelogenesis comprises of enamel formation by specialized cells called ameloblasts. Ameloblasts secrete matrix proteins and are responsible for the creation of an extracellular environment that favors the enamel mineralization. However, various factors, such as the dental trauma, can interfere with amelogenesis, contributing to the formation of a defective enamel. Dental trauma has been responsible for many cases of hypoplasia which can weaken the tooth, in addition to bringing aesthetic discomfort. Objective: examine the morphological changes on the odontogenic epithelium and the enamel matrix of rats incisors, produced by dental trauma. Methodology: rats incisors were extruded and then repositioned in their original alveoli. After 3, 7, 10, 20, 30 and 60 days of the surgical procedure, teeth were fixed in a solution of formaldehyde and glutaraldehyde, processed histologically and stained with toluidine blue. Results: the morphological analysis revealed the formation of enamel matrix extremely heterogeneous, with irregular thickness, particularly on the apical portion of the incisors. Some matrixes of exposed enamel showed small gaps of reabsorption, often with deposition of cementoid material. Conclusion: the present study showed that the trauma was enough to produce hypoplastic and hypomineralization changes important in the enamel that were related to the functional phase of the ameloblasts in the affected region

Expression and Localization of Keap1 During Amelogenesis in the Developing Molar Germ of Rats

The objective of this study was to examine the expression pattern of Kelch-like ECH-associated protein 1 (Keap1) in the maxillary 2(nd) molar germs of rats. We used the maxillary 2(nd) molar germs in rats' pup at postnatal day 3 (bell stage), 6 (crown formation stage) and 9 (root formation stage). The investigation on mRNA and protein levels were done using reverse transcription - polymerase chain reaction and western blot. Localization of Keap 1 in the maxillary 2(nd) molar germs were revealed through immunofluorescence staining. Keap1 from the maxillary 2nd molar germs were mostly manifested on postnatal day 3 and dramatically decreased on postnatal day 6 and 9 at mRNA and protein levels, while amelogenin and ameloblastin increased during the development of maxillary 2nd molar germs. During immunofluorescence analysis, the strong immunoreactivity against Keap1 was detected in the apical side of ameloblasts at the presecretory and secretory stages. However, Keap1 expression was hardly observed in the ameloblasts at the maturation stage. These results shows that Keap1 is strongly expressed in the presecretory and secretory ameloblasts of amelogenesis, and suggest that Keap1 may be a crucial molecule for the regulatory mechanisms tasked with the formation of enamel layer.

Effects of RhoA on the adherens junction of murine ameloblasts / 北京大学学报(医学版)

OBJECTIVE@#To investigate the regulation mechanism of RhoA signaling pathway during the enamel formation by using the EGFP-RhoADominant Negative (EGFP-RhoADN) transgenic mice model, from the aspect of adherens junctions, and to provide a theory basis for mechanism of enamel development defects.@*METHODS@#The enamel thickness of mandibular first molars of EGFP-RhoADN transgenic mice and wild type (WT) mice were observed by scanning electronic microscopy at 20 kV, and the enamel thickness of the distal face of the central cusp was measured at 10 locations via analysis by ImageJ (Rasband, 1997-2009). The enamel organs from mandibular first molars from postnatal-4-day (P4) EGFP-RhoADN mice and wild type mice were isolated, and the total RNA and protein were extracted from the epithelium of the enamel organs. The expression level of the adherens junctions components in ameloblasts layer of the postnatal-4-day EGFP-RhoADN transgenic mice and wild type mice mandibular first molars were detected by real-time PCR and Western blot assay.@*RESULTS@#The EGFP-RhoADN transgenic mice had decreased enamel thickness in their bilateral mandibular first molars versus those of control group (n=20), and enamel thickness was (84.60±0.20) μm vs. (106.24±0.24) μm, P<0.05. The protein expressions of E-cadherin, α-E-catenin and pan-cadherin in ameloblasts layer of postnatal-4-day EGFP-RhoADN transgenic mice molars were down-regulated, and the protein level of β-catenin in ameloblasts layer of P4 EGFP-RhoADN transgenic mice molars was up-regulated. The mRNA level of E-cadherin in ameloblasts layer of P4 EGFP-RhoADN transgenic mice molars was down-regulated versus that of WT mice, and the gene expression of E-cadherin was 0.93±0.01 vs. 1.00±0.02, P<0.05. The mRNA level of β-catenin in ameloblasts layer of P4 EGFP-RhoADN transgenic mice molars was up-regulated versus that of WT mice, and the gene expression of β-catenin was 1.23±0.03 vs. 1.00±0.05, P<0.05.@*CONCLUSION@#In the mandibular first molars of EGFP-RhoADN transgenic mice, the enamel formation was disrupted and the adherens junctions of EGFP-RhoADN transgenic mice ameloblasts were implicated during amelogenesis. RhoA signaling pathway may play a critical role in enamel development by altering the adherens junctions in ameloblasts.

Pathogenesis of dental fluorosis: biochemical and cellular mechanisms / Patogénesis de la fluorosis dental: mecanismos bioquímicos y celulares

Abstract. The mechanisms involved in the development of dental fluorosis are still unknown. The development of in vivo and in vitro models using biologically relevant concentrations of fluoride for the emergence of fluorosis has allowed suggesting hypotheses that contribute to the understanding of the mechanisms that produce this defect in enamel development, with high prevalence in Colombia. This topic review presents an update on the normal mechanisms of the formation of enamel and how they are affected by exposure to high concentrations of fluoride. This is a thorough review of the deleterious effects of fluoride on the cells and the extracellular matrix, especially during the maturation stage, resulting in a delay of the removal of the protein matrix of amelogenins, as well as the appearance of mottled enamel-a characteristic of dental fluorosis. Finally, it shows the perspectives of the study of this defect in enamel development from biochemistry and cellular and molecular biology.

RESUMEN. Los mecanismos involucrados en el desarrollo de la fluorosis dental aún no se conocen a cabalidad. El desarrollo de modelos in vivo e in vitro que utilizan concentraciones de fluoruro biológicamente relevantes para la aparición de fluorosis ha permitido el planteamiento de hipótesis que aportan cada vez más al conocimiento de los mecanismos que generan este defecto del desarrollo del esmalte, de alta prevalencia en Colombia. Esta revisión presenta una actualización sobre los mecanismos normales de la formación del esmalte y cómo estos se ven afectados por la exposición a altas concentraciones de fluoruro. Se presenta una revisión en detalle de los efectos deletéreos del fluoruro sobre las células y sobre la matriz extracelular, especialmente durante la etapa de maduración, que tendrán como consecuencia el retraso de la remoción de la matriz proteica de amelogeninas y se traducirá en la apariencia de esmalte moteado, característica de la fluorosis dental. Por último, se muestran las perspectivas del estudio de este defecto del desarrollo del esmalte desde la bioquímica y la biología celular y molecular.

Expression of enamel proteins in rough endoplasmic reticulum and golgi complex in human dental germs / Expresión de proteínas del esmalte en retículo endoplásmico rugoso y complexo golgiensis en gérmenes dentales humanos

Tooth enamel is the hardest tissue in the body. The organic matrix configuration is provided by the main proteins amelogenin, ameloblastin and enamelysin (MMP20), an enzyme that helps to shape the matrix. The aim of this study was to determine by histochemistry the expression of amelogenin and enamelysin through the rough endoplasmic reticulum in the late stages of amelogenesis, and its expression in the Complexus golgiensis (Golgi complex / Golgi apparatus) in the early stages in human fetuses. In early stages a colocalization of both proteins inside the Golgi apparatus was found, being more evident the relationship between Golgi and amelogenin (99.92 %). In the late stage, a colocalization of both proteins and rugged endoplasmic reticulum was found. With enamelysin being more evident in relation with rough endoplasmic reticulum (99.95 %). Our findings demonstrated the presence of amelogenin and enamelysin in odontoblast and ameloblast. However, the presence of these two proteins in odontoblast remains unknown.

El esmalte dental es el tejido más duro del cuerpo. La configuración de la matriz orgánica es proporcionada por las proteínas principales amelogenina, ameloblastina y enamelisina (MMP20), una enzima que ayuda a dar forma a la matriz. El objetivo de este estudio fue determinar mediante histoquímica la expresión de amelogenina y enamelisina a través del retículo endoplasmático rugoso en las últimas etapas de la amelogénesis , y su expresión en el Complexo golgiensis en las primeras etapas de formación en fetos humanos. En las primeras etapas se observó colocalización de ambas proteínas en el interior del Complexo golgiensis, siendo más evidente la relación entre Golgi y amelogenina (99,92 %). En la última etapa, se identificó una colocalización de ambas proteínas y retículo endoplásmico rugoso. Resulto más evidente la enamelisina en relación con el retículo endoplasmático rugoso (99,95 %). Nuestros resultados demostraron la presencia de amelogenina y enamelisina en odontoblastos y ameloblastos, sin embargo se desconoce la presencia de estas dos proteínas en odontoblastos.

Expresión de tuftelina en gérmenes dentales humanos / Expression of tuftelin in human dental germs

La tuftelina es una proteína secretada en la matriz adamantina en desarrollo durante la formación del esmalte. Su función continúa sin esclarecerse, aunque se presume que juega un papel importante en la biomineralización de esmalte y dentina, así como en el desarrollo del órgano dental. Con el presente estudio se identificó su localización en las diferentes estructuras de gérmenes dentales de fetos humanos, conforme a los resultados se observó su expresión en el estadio pre-secretor observándose en el citoplasma de los ameloblastos, retículo estrellado, papila dental, así como en el estrato intermedio; en el secretor se identificó principalmente en la unión amelodentinaria, y en la superficie externa del esmalte, observando una marcada expresión de la proteína en la porción basal del proceso odontoblástico, pero no en la matriz extracelular de la dentina. De acuerdo a los resultados obtenidos se puede considerar que su expresión se presenta tanto en la amelogénesis, como en la odontogénesis en tejidos sin mineralizar.

The tuftelin is a secreted protein in the adamantine matrix in developing during the enamel formation. Its function continues unclarified, although it plays a role in the biomineralization of the dental organ. With the present studio the location was identified in the different structures of dental germs from human fetuses, according to the results it was observed the expression in the pre-secretor stage being observed in the cytoplasm of ameloblasts, stellate reticulum, dental papilla, also in the intermediate stratum; in the secretor it was mainly identified in the amelodentinal junction and in the outer surface of enamel, observing a marked expression of the protein in the basal portion of the odontoblastic process, but not in the extracellular matrix of the dentine. According to the results obtained it can be considered that its expression occurs in both amelogenesis and odontegenesis in unmineralized tissues.

Full-mouth rehabilitation in an amelogenesis imperfecta patient with anterior open bite using CAD/CAM system / 대한치과보철학회지

Amelogenesis imperfecta characterized as abnormally formed enamel is caused by a defect of unique group of genes. Patients affected by this disease might have difficulties in social and psychological aspects due to non-esthetic teeth as well as functional problems caused by enamel detachment and tooth wear from their early ages. Adult patients with amelogenesis imperfecta can be treated with full-mouth restorations, which make functional and esthetic rehabilitations of severely worn tooth. However, the anterior open bite and lack of occlusal clearance for posterior teeth restorations due to compensatory extrusion are the intervening factors in the prosthetic treatment. Therefore, the determination of anterior tooth lengths, vertical dimension, and anterior guidance should be set carefully. Recently, computer-aided design and computer-aided manufacturing (CAD/CAM) techniques help systematic approaches and enable dentists to reduce time-consuming procedures in the diagnosis and treatment of full-mouth rehabilitation. This case report demonstrates the successful full mouth rehabilitation using a CAD/CAM system in a young adult patient with amelogenesis imperfecta and anterior open bite.

Estudio de la microdureza de dientes permanentes con fluorosis incipiente, tratados con resina infiltrante / Micro-hardness of permanent teeth with incipient fluorosis treated with infiltrant resin / Estudo da microdureza de dentes permanentes com fluorose incipiente tratados com resina infiltrante

Objetivo: Evaluar la microdureza del esmalte afectado con fluorosis sometido a tratamiento con resina infiltrante, compa-rándolo con dientes sanos y dientes con fluorosis incipiente. Materiales y métodos: La muestra estuvo constituida por 15 dientes permanentes humanos recolectados del Banco de Dientes de la Facultad de Odontología de la Universidad Central del Ecuador. Para la selección de los dientes se tuvieron en consideración los criterios diagnósticos de fluorosis dental según Thylstrup y Ferjeskov (1978), teniendo 5 dientes con score 0 y 10 dientes con fluorosis incipiente (score 1-3). Todos los dientes considerados en el estudio no presentaron lesiones de caries, grietas ni fracturas. La muestra fue dividida en 3 grupos, G1: dientes sanos (control negativo), G2: dientes con fluorosis incipiente y G3: dientes con fluorosis incipiente tratado con resina infiltrante Icon®. A cada grupo (n=5) se le realizó una profilaxis y posteriormente al G3 se le aplicó la resina infiltrante. La microdureza knoop fue obtenida mediante tres indentaciones con microdurometro (Wilson Tukon Microhardness Tester). Los datos fueron analizados a través del método de Rho de Spearman con significancia de 5%. Resultados: La media de la microdureza knoop de los grupos y sus desviaciones estándar fueron de: G1=284,8 ± 56,2 G2=325,7 ± 95,1 G3=226,2 ± 67,4. no se encontraron diferencias estadísticamente significativas entre los grupos estudia-dos (p>0,05). Conclusión: La microdureza del esmalte afectado por fluorosis incipiente sometida a tratamiento con resina infiltrante, esmalte de dientes sanos y esmalte de dientes con fluorosis incipiente no mostró diferencia estadística.

Objective: To evaluate the microhardness of the enamel affected by fluorosis subjected to treatment with infiltrating resin, comparing it with sound teeth and teeth with incipient fluorosis. Materials and methods: The sample consisted of 15 permanent human teeth collected from the Teeth Bank of the Faculty of Odontology of the Central University of Ecuador. For the selection of the teeth, diagnostic criteria of dental fluorosis were considered according to Thylstrup and Ferjeskov (1978), having 5 teeth with score 0 and 10 teeth with incipient fluorosis (score 1-3). None of the teeth that were examined in the study had caries, cracks or fractures. The sample was divided into 3 groups. G1: sound teeth (negative control), G2: teeth with incipient fluorosis and G3: teeth with incipient fluorosis treated with Icon® infiltrating resin. To each group (n=5), dental prophylaxis was performed and afterwards to G3, infiltrating resin was applied. The Knoop micro-hard-ness was obtained through 3 indentations with microhardness tester (Wilson Tukon Microhardness Tester). The data were analyzed through the Spearman's Rho method with 5% significance. Results: The median of Knoop microhardness of the groups and their standard deviations were: G1=284.8 ± 56.2 G2=325.7 ± 95.1 G3=226.2 ± 67.4, no statistically significant differences were found between the examined groups (p>0.05). Conclusion: The microhardness of the enamel affected by incipient fluorosis subjected to treatment with infiltrating resin, enamel of sound teeth, and enamel of teeth with incipient fluorosis did not demonstrate statistical difference.

RESUMOObjetivo: Avaliar a microdureza do esmalte afetado com fluorose incipiente submetido ao tratamento com resina infiltrada, fazendo uma comparação com dentes higidos dentes com fluorose incipiente. Materiais e métodos: A amostra estava constituída por 15 dentes permanentes humanos coletados do Banco de Dientes de la Facultad de Odontología de la Uni-versidad Central del Ecuador (Banco de dentes da Faculdade de Odontologia da Universidade Central do Equador). Para a seleção dos dentes se considerou os critérios de diagnóstico de fluorose dental segundo Thylstrup y Ferjeskov (1978), tendo 5 dentes com pontuação de 0 e 10 dentes com fluorose incipiente (pontuação de 1 a 3). Todos os dentes considerados no estudo não apresentaram lesões de cárie, rachaduras nem fraturas. A amostragem foi dividida em 3 grupos: G1: dentes higidos (controle negativo); G2: dentes com fluorose incipiente e G3: dentes com fluorose incipiente tratados com resina infiltrante Icon®. Para cada grupo (n=5) uma profilaxia foi realizada, e posteriormente ao G3 se aplicou a resina infiltrante. A microdureza knoop foi obtida mediante três entalhes com microdurómetro (Wilson Tukon Microhardness Tester). Os dados foram analisados através do método de Rho de Spearman com um nivel de 5%. Resultados: A média da microdu-reza knoop dos grupos e seus desvios padrões foram de G1=284,8 ± 56,2; G2=325,7 ± 95,1; G3=226,2 ± 67,4, não foram estatisticamente encontradas diferenças significativas entre os grupos estudados (p>0,05). Conclusão: A microdureza do esmalte afetado com fluorose incipiente submetido ao tratamento com resina infiltrante, esmalte de dentes hígidos e de dentes com fluorose incipiente demostrou não ter diferença estatisticamente significativa.

The role of enamelysin (MMP-20) in tooth development: systematic review / El papel de la enamelisina (MMP-20) en el desarrollo dentario: revisión sistemática

ABSTRACT. Introduction: ameloblasts are cells responsible for the production and mineralization of the organic matrix of enamel through several stages: pre-secretory, secretory, transition, and maturation. The organic matrix components are produced in the secretory phase. In the maturation phase, the organic component is removed and the mineralization process starts. This process requires the involvement of matrix metalloproteinase 20 (MMP-20), also called enamelysin. Several studies have shown the presence of MMP-20 in tooth development and its relationship to alterations in enamel formation. The objective was: to classify the different studies and laboratory techniques used to demonstrate the involvement of enamelysin in tooth development and its relation to pathologies during enamel formation. Methods: a systematic review was conducted with the following bibliographic databases: PubMed, Science-Direct, Hinari, and SciELO, in order to classify the different studies related to the involvement of MMP-20 in tooth development and the methods to detect its expression, between the years of 2009 and 2014. Results and conclusions: 11 in vitro models show that MMP-20 has specific cleavage sites for enamel matrix proteins. This process is altered by chemical composition, ions, and the presence of hydroxyapatite. Enamel morphology is altered in the knockout models. In human studies, MMP-20 has been associated with increased susceptibility to dental caries, enamel thickness, and dental agenesis.

RESUMEN. Introducción: el ameloblasto es la célula encargada de la producción y mineralización de la matriz orgánica del esmalte. Atraviesa varias etapas: la fase pre-secretora, secretora, de transición y maduración. En la fase secretora se producen los componentes de la matriz orgánica. En la fase de maduración se elimina el componente orgánico y se inicia el proceso de mineralización. Este proceso requiere de la participación de la metaloproteinasa de matriz 20 (MMP-20) o también llamada enamelisina. Diversos estudios demuestran la presencia de MMP-20 en el desarrollo dentario y su relación con alteraciones en la formación del esmalte. El objeto fue clasificar los diferentes estudios y técnicas de laboratorio empleadas que demuestren la participación de enamelisina en el desarrollo dentario y su relación con patologías en la formación del esmalte. Métodos: se realizó una revisión sistemática de la literatura con las siguientes bases bibliográficas: PubMed, Science-Direct, Hinari y SciELO, con el fin de clasificar los diferentes estudios relacionados con la participación de MMP-20 en el desarrollo dental y los métodos utilizados para detectar su expresión, entre los años de 2009 a 2014. Resultados y conclusiones: los modelos in vitro evidencian que MMP-20 tiene sitios específicos de escisión para las proteínas de matriz de esmalte. Este proceso se ve alterado por la composición química, iones, y la presencia de hidroxiapatita. En los modelos knockout la morfología del esmalte está alterada. En los estudios en humanos, se ha relacionado la MMP-20 con una mayor susceptibilidad de caries dental, el grosor completo de esmalte y agenesias dentales.

Enamel renal syndrome with associated amelogenesis imperfecta, nephrolithiasis, and hypocitraturia: A case report

Numerous cases of enamel renal syndrome have been previously reported. Various terms, such as enamel renal syndrome, amelogenesis imperfecta and gingival fibromatosis syndrome, and enamel-renal-gingival syndrome, have been used for patients presenting with the dental phenotype characteristic of this condition, nephrocalcinosis or nephrolithiasis, and gingival findings. This report describes a case of amelogenesis imperfecta of the enamel agenesis variety with nephrolithiasis in a 21-year-old male patient who complained of small teeth. The imaging modalities employed were conventional radiography, cone-beam computed tomography, and renal sonography. Such cases are first encountered by dentists, as other organ or metabolic diseases are generally hidden. Hence, cases of amelogenesis imperfecta should be subjected to advanced diagnostic modalities, incorporating both dental and medical criteria, in order to facilitate comprehensive long-term management.

Enamel defects frequency in deciduous teeth

Developmental defects of the enamel are the result of alterations during amelogenesis due to hereditary, systemic or environmental factors. The present study was done to determine the frequency of developmental defects of enamel in primary teeth at Children Hospital PIMS, Islamabad from February 2011 to January 2012. The study was cross sectional and sample comprised of 300 children, which included 182 [60.7%] males and 118 [39.3%] females. The mean age of the studied population was 3.63 +/- 1.05 years. Enamel defects were present in 115 [38.3%] children. Out of 182 males 69 [37.9%] males and out of 118 females,46 [38.9%] females had enamel defect; thus frequency of enamel defect was not significantly different between the two genders [p=0.852]. The mean age of the children with enamel defect was 3.74 +/- 1.00 and mean age of children without enamel defect was 3.55 +/- 1.06 years respectively. This difference was not statistically significant [p=0.124]. Frequency of enamel defect was significantly higher among families with higher income categories [p=0.020].Out of 300 children, 185 [61.7%] had normal enamel, 5 [1%] had only demarcated opacity, 9 [3%] had only diffuse opacity, 80 [26.7%] had only hypoplasia, 3 [1%] had demarcatead diffuse opacity, 3 [1%] had demarcated opacity with hypoplasia, 13 [4.3%] had diffuse opacity with hypoplasia and 2 [0.7%] had all three defects. Present study concluded that more than one third of the children had developmental defects of enamel in primary teeth and most frequent lesion was enamel hypoplasia

Efeito da amoxicilina e do fluoreto no desenvolvimento do esmalte dentário de ratos / Effect of amoxicillin and fluoride on enamel development in rat teeth

O uso da amoxicilina durante a primeira infância tem sido relacionado ao desenvolvimento de defeitos de esmalte denominados Hipomineralização Molar-Incisivo (HMI). Ademais, há relatos de possível potencialização dos efeitos do fluoreto no esmalte pela amoxicilina. Objetivo: A proposta do presente estudo foi avaliar o efeito da amoxicilina, e da associação amoxicilina com fluoreto no desenvolvimento do esmalte dentário de ratos. Metodologia: O experimento foi dividido em três capítulos. Capítulo 1 - Quinze ratas prenhas (Rattus norvegicus, albinus, Holtzman) foram aleatoriamente distribuídas em três grupos que receberam, a cada 24 h, dose intragástrica de amoxicilina 100 mg/kg/dia (grupo GA100), amoxicilina 500 mg/kg/dia (grupo GA500) ou soro fisiológico (grupo GS), a partir do 130 dia de prenhez. Após o nascimento, doze filhotes de cada grupo receberam o mesmo tratamento das respectivas mães durante os períodos de 7 dias (n=6) e 12 dias (n=6) de vida. Após a eutanásia, as cabeças dos ratos foram removidas, fixadas e processadas para inclusão em parafina. Os cortes frontais da cabeça exibindo os primeiros molares superiores foram em parte corados com H&E e em parte submetidos à reação imuno-histoquímica para detecção de amelogenina e metaloproteinases da matriz-20 (MMP-20). Os cortes corados com H&E foram utilizados para análise morfológica e mensuração da espessura da camada de esmalte. A imunoexpressão para amelogenina e MMP-20 foram avaliados por análise semiquantitativa (H-score). Os dados foram analisados estatisticamente pelo teste Tukey com nível de significância de 5%. Capítulo 2 - Quinze ratas prenhas (Rattus norvegicus, albinus, Holtzman) foram aleatoriamente distribuídas em três grupos, que receberam, amoxicilina 100 mg/kg/dia (grupo GA100), amoxicilina 500 mg/kg/dia (grupo GA500) ou soro fisiológico (grupo GS), conforme descrito no capítulo 1. Após o nascimento, dez filhotes por grupo receberam o mesmo tratamento do 10 ao 400 dia de vida. Aos 40 dias, os animais sofreram eutanásia, os incisivos e molares foram extraídos, e submetidos às análise do conteúdo de cálcio, pelo método de titulação com EDTA, de fósforo por método colorimétrico usando espectrofotômetro. E a densidade eletrônica do esmalte nos primeiros molares foi analisada pela tomografia micro-computadorizada (XRM). Capítulo 3 - Quarenta ratos foram distribuídos, aleatoriamente, em quatro grupos, expostos ao fluoreto na água (100 ppm (mg F/L) ou à administração intragástrica de amoxicilina (500 mg/Kg peso), segundo as combinações: grupo controle (GS); grupo amoxicilina (GA), grupo fluoreto (GF) e grupo amoxicilina com fluoreto (GA+F). Após 60 dias, amostras de plasma e uma tíbia foram coletados e analisados quanto a concentração de fluoreto por meio de eletrodo de íon seletivo. Os incisivos foram submetidos à quantificação do grau de fluorose (por um software de análise de imagens, Dental fluorosis by Image Analysis ­ DFIA), a análise de conteúdo de cálcio, pelo método de titulação com EDTA, de fósforo por método colorimétrico usando espectrofotômetro, e determinações da espessura do esmalte e de sua microdureza. Resultados: Capítulo 1 - Aos 7 dias, diversas estruturas vacuolares foram observadas na porção citoplasmática distal dos ameloblastos dos ratos dos grupos GA100 e GA500; além disso, a espessura do esmalte foi significantemente menor nos grupos GA100 e GA500 quando comparado ao GS (p<0,001). Em contraposição, diferenças estatisticamente significantes não foram observadas entre os grupos no período de 12 dias (p=0,111). Diferenças entre os grupos também não foram observadas na intensidade de imunomarcação exibida pelos ameloblastos à anti-amelogenina (p=0,818) e à anti-MMP-20 (p=0,855). Capítulo 2 - Não foram observadas diferenças estatisticamente significante no conteúdo de cálcio (p=0,180), fósforo (p=0,054) e densidade eletrônica (p=0,150) entre os grupos. Capítulo 3 - Observou-se que a espessura do esmalte (p=0,228) e a concentração de cálcio (p=0,592) e fósforo (p=0,409) nos incisivos não diferiram estatisticamente entre os grupos. No entanto, a concentração de fluoreto nos tecidos dentário, ósseo e plasma foi maior nos grupos expostos em GF e GA+F (p<0.001). A análise fotográfica pelo índice DFIA e a microdureza mostraram diferenças significativas entre os grupos (p<0.001), sendo que GF apresentou maior severidade de hipomineralização do esmalte, seguido por GA+F e GA. Houve um aumento linear na dureza do esmalte quando nas profundidades de 10 µm a 30 µm, sendo esse aumento entre 4 a 5 KHN por µm de profundidade nos GA+F e GF, e entre a 7 a 8 KHN por µm nos grupos GA e GS. Os achados desse estudo mostraram que os animais expostos cronicamente ao fluoreto desenvolveram hipomineralização de esmalte, e a associação da amoxicilina não potencializou a severidade da hipomineralização. Conclusão: Capítulo 1 - Conclui-se que a amoxicilina pode provocar alterações durante a amelogênese, as alterações foram observadas no estágio secretor da matriz do esmalte, sugerindo atraso na aposição de matriz do esmalte. Capítulo 2 - Conclui-se que a amoxicilina não influenciou o conteúdo mineral dos incisivos e molares de ratos. Capítulo 3 - Concluímos que a amoxicilina não influenciou o desenvolvimento do esmalte, bem como não potencializou o efeito do fluoreto

Background: Amoxicillin use in early childhood has been associated with molarincisor hypomineralization. Moreover, it has been supposed an association between amoxicillin and fluoride on enamel defects. Aim. This study aimed to evaluate in vivo the effect of amoxicillin and amoxicillin associated with fluoride on the enamel development of rat tooth. Materials and Methods: The research was divided into three studies. Chapter 1 ­ Fifteen pregnant Holtzman rats (Rattus norvegicus albinus) were divided randomly into three groups to receive saline (SG), 100 mg/kg/day amoxicillin (A100G), or 500 mg/kg/day amoxicillin (A500G), intragastrically, from days 13 to 22 of pregnancy. Twelve offsprings per group got the same dose until day 12. After 7 and 12 days, the specimens were fixed and embedded in paraffin. In the HEstained sections, the thickness of enamel matrix of upper molar germs was evaluated. Moreover, detection of amelogenin on day 7 and matrix metalloproteinase 20 (MMP -20) on day 12 by immunohistochemistry were carried out. Chapter 2 - Fifteen rats (Rattus norvegicus, Albinus,Holtzman) were randomly divided into three groups to receive saline (SG), 100 mg/kg/day amoxicillin (A100G), or 500 mg/kg/day amoxicillin (A500G), as described in Chapter 1. Ten offspring per group received the same dose until day 40. The animals were euthanized on day 40. A total of 60 upper incisors and 60 upper first molars from 30 animals were dissected. Calcium (Ca) determination was performed by the compleximetric titration method and phosphorus (Pi) determination by colorimetric analysis using a spectrophotometer at 680 nm. A total of 30 lower first molars from 15 animals were analyzed under X-ray microtomography (XMT). Chapter 3 - Forty rats were, randomly, divided into four groups exposed to fluoride in water (100 ppm (mg F/L) or intragastric administration of amoxicillin (500 mg /kg body weight), according to the combinations: control group (SG); amoxicillin group (AG), fluoride group (FG) and amoxicillin with fluoride group (A+FG.) After 60 days, the animals were euthanized. The concentrations of fluoride in the plasma, tibia and incisors of the rats were determined. The incisors were also analysed by the fluorosis severity (by software image analysis, Dental fluorosis by Image analysis - DFIA), calcium content by compleximetric titration method and phosphorus content by colorimetric method, enamel thickness, and its hardness. Results: Chapter 1 - A100G and A500G groups showed lower thickness of the enamel matrix than GS (p<0.001) on day 7, but not on day 12 (p=0.111). On day 7, the treated groups showed morphological changes in ameloblasts, represented by vacuoles. The amelogenin (p=0.818) and MMP20 (p=0.855) immunostaining intensity did not differ among groups. Chapter 2 - There were no statistically significant differences in Ca content (p=0.180), Pi content (p=0.054), or XMT electron density (p=0.150) among the groups. Chapter 3 - The thickness of the enamel (p=0.228), Ca content (p= 0.592) and Pi content (p=0.409) were not statistically different among the groups. However, the concentration of fluoride in the tooth, bone, and plasma was higher in the FG and A+FG (p< 0.001) than AG and SG. The DFIA index and microhardness showed significant differences among groups (p<0.001), and FG presented greater severity hypomineralization enamel than SG, followed by A+FG and AG. The hardness increased linearly in the 10 µm a 30 µm depths, being from 4 to 5 KHN per mm in depth in the AG and A+FG, and from 7 to 8 KHN mm in depth in the AG and SG. The findings of this study showed that animals chronically exposed to fluoride developed enamel hypomineralization, and the association of amoxicillin had no role in the hypomineralization severity. Conclusion: Chapter 1 - Amoxicillin can cause changes only during secretory stage, suggesting a delay in ameloblasts differentiation. Chapter 2 ­ Amoxicillin did not affect the mineral content and electron density of rat teeth. Chapter 3 ­ Amoxicillin did not influence the development of the enamel, and did not potentiate the effect of fluoride

Avaliação genética da hipomineralização molar-incisivoAutor / Genetic evaluation of the molar-incisor hypomineralization

Distúrbios genéticos durante o desenvolvimento dentário influenciam na variação do número e formada dentição. Este é o primeiro estudo a avaliar se a variação genética nos genes da formação do esmalte dentário está associada com a Hipomineralização Molar-Incisivo (HMI), levando também em consideração, a experiência de cárie. Amostras de DNA de 71 casos (com HMI) e 89 controles (não afetados) de Araraquara/SP (Brasil) foram analisadas. Onze marcadores em cinco genes [ameloblastina (AMBN), amelogenina (AMELX), enamelina (ENAM), tuftelina (TUFT1), e proteína 11 interagindo com tuftelina (TFIP11)] foram genotipados pelo método TaqMan. O teste Qui-quadrado foi utilizado para comparar as frequências alélicas e genotípicas entre os grupos caso e controle. A experiência de cárie no grupo HMI também foi avaliada para a associação com a variação genética nos genes da formação do esmalte. Os marcadores rs3796704 (ENAM), rs4694075 (AMBN); rs5997096/rs134136 (TFIP11), foram associados com a HMI (p<0.05). Associações dos marcadores rs5997096/rs134136(TFIP11), rs12640848/rs3796704 (ENAM) e rs17878486 (AMELX) (p<0.05) com a cárie dentária foram observadas. O presente estudo sugere possibilidade de associação entre o esmalte hipomineralizado e variação genética nos genes da formação do esmalte dentário

Genetic disturbances during dental development influence variation of number and shape of the dentition. This is the first study that tested if genetic variation in enamel formation genes is associated with molar-incisor hypomineralization (MIH), also taking into consideration caries experience. DNA samples from 71 cases with MIH and 89 unaffected controls from Araraquara/SP (Brazil) were studied. Eleven markers in five genes [ameloblastin (AMBN), amelogenin (AMELX), enamelin (ENAM), tuftelin (TUFT1), and tuftelin-interacting protein 11 (TFIP11)] were genotyped by the TaqMan method. Chi-square was used to compare allele and genotype frequencies between cases with MIH and controls. Distinct caries experience within the MIH group was also tested for association with genetic variation in enamel formation genes. The markers, rs3796704 (ENAM), rs4694075 (AMBN); rs5997096/rs134136 (TFIP11), were associated with MIH (p<0.05). Associations between rs5997096/rs134136 (TFIP11), rs12640848/rs3796704 (ENAM) e rs17878486 (AMELX) (p<0.05) markers could be seen with caries. This study suggests a possible association between hypomineralized enamel and genetic variation in the genes of the enamel formation

The similarity between human embryonic stem cell-derived epithelial cells and ameloblast-lineage cells / 国际口腔科学杂志·英文版

This study aimed to compare epithelial cells derived from human embryonic stem cells (hESCs) to human ameloblast-lineage cells (ALCs), as a way to determine their potential use as a cell source for ameloblast regeneration. Induced by various concentrations of bone morphogenetic protein 4 (BMP4), retinoic acid (RA) and lithium chloride (LiCl) for 7 days, hESCs adopted cobble-stone epithelial phenotype (hESC-derived epithelial cells (ES-ECs)) and expressed cytokeratin 14. Compared with ALCs and oral epithelial cells (OE), ES-ECs expressed amelogenesis-associated genes similar to ALCs. ES-ECs were compared with human fetal skin epithelium, human fetal oral buccal mucosal epithelial cells and human ALCs for their expression pattern of cytokeratins as well. ALCs had relatively high expression levels of cytokeratin 76, which was also found to be upregulated in ES-ECs. Based on the present study, with the similarity of gene expression with ALCs, ES-ECs are a promising potential cell source for regeneration, which are not available in erupted human teeth for regeneration of enamel.

Bone morphogenetic protein-2 gene controls tooth root development in coordination with formation of the periodontium / 国际口腔科学杂志·英文版

Formation of the periodontium begins following onset of tooth-root formation in a coordinated manner after birth. Dental follicle progenitor cells are thought to form the cementum, alveolar bone and Sharpey's fibers of the periodontal ligament (PDL). However, little is known about the regulatory morphogens that control differentiation and function of these progenitor cells, as well as the progenitor cells involved in crown and root formation. We investigated the role of bone morphogenetic protein-2 (Bmp2) in these processes by the conditional removal of the Bmp2 gene using the Sp7-Cre-EGFP mouse model. Sp7-Cre-EGFP first becomes active at E18 in the first molar, with robust Cre activity at postnatal day 0 (P0), followed by Cre activity in the second molar, which occurs after P0. There is robust Cre activity in the periodontium and third molars by 2 weeks of age. When the Bmp2 gene is removed from Sp7(+) (Osterix(+)) cells, major defects are noted in root, cellular cementum and periodontium formation. First, there are major cell autonomous defects in root-odontoblast terminal differentiation. Second, there are major alterations in formation of the PDLs and cellular cementum, correlated with decreased nuclear factor IC (Nfic), periostin and α-SMA(+) cells. Third, there is a failure to produce vascular endothelial growth factor A (VEGF-A) in the periodontium and the pulp leading to decreased formation of the microvascular and associated candidate stem cells in the Bmp2-cKO(Sp7-Cre-EGFP). Fourth, ameloblast function and enamel formation are indirectly altered in the Bmp2-cKO(Sp7-Cre-EGFP). These data demonstrate that the Bmp2 gene has complex roles in postnatal tooth development and periodontium formation.

A post-classical theory of enamel biomineralization… and why we need one / 国际口腔科学杂志·英文版

Enamel crystals are unique in shape, orientation and organization. They are hundreds of thousands times longer than they are wide, run parallel to each other, are oriented with respect to the ameloblast membrane at the mineralization front and are organized into rod or interrod enamel. The classical theory of amelogenesis postulates that extracellular matrix proteins shape crystallites by specifically inhibiting ion deposition on the crystal sides, orient them by binding multiple crystallites and establish higher levels of crystal organization. Elements of the classical theory are supported in principle by in vitro studies; however, the classical theory does not explain how enamel forms in vivo. In this review, we describe how amelogenesis is highly integrated with ameloblast cell activities and how the shape, orientation and organization of enamel mineral ribbons are established by a mineralization front apparatus along the secretory surface of the ameloblast cell membrane.