Enamel Formation Research Articles

Determination of mutation in the coding regions of FAM83H and ENAM genes in patients with imperfect enamel (Amelogenesis Imperfecta)

Introduction: Tooth enamel is a precious and highly mineralized tissue in the human body. Amelogenesis Imperfecta (AI) is a developmental, evolutionary and hereditary disease presents with the rare abnormal formation of enamel that affects the primary and secondary dentition. The molecular base of the incomplete quinizium together with clinical manifestation suggest that AI may result from mutations in the FAM83H and ENAM genes. In this study, we aimed to evalu- ate the association between Amelogenesis Imperfecta and mutations in the FAM83H and ENAM genes in 18 Iranian families with AI in dominant and non-syndromic form. Materials and Methods: 18 Iranian families with at least 1 patient with Amelogenesis Imperfecta were included in this case study and were examined for related specific manifestations and also, 10CC of blood was taken from each patient followed by PCR and genome sequence for genetic alterations in FAM83H and ENAM. Genome sequences were analyzed using CLC software and CLC Sequence Viewer was used to compare them with reference sequences in the RefSeq database at the NCBI later were discussed together with clinical manifestations for each patient. Results: All patients showed a mutation in the exon 5 of FAM83H gene in nucleotide rs56148058C/T which converted Serotonin to Aspartin. In two patients carried a mutation in the nucleotide rs546809055A/G that changed Leucine to Phenylalanine. None of patients showed sig- nificant alteration in the ENAM gene. Conclusion: This study indicates that FAM83H gene plays an import role in incidence of Amelogenesis Imperfecta in Iran.

Association of polymorphisms in genes involved in enamel formation, taste preference and immune response with early childhood caries in Saudi pre-school children.

Dental caries is primarily elicited by modifiable factors such as inadequate oral hygiene, poor dietary practices and deficient fluoride exposure. However, there is a growing body of evidence suggesting the profound influence of genetic factors in dental caries susceptibility. The present study aimed to evaluate the association between single nucleotide polymorphisms (SNPs) in ENAM (rs12640848), MMP20 (rs1784418), TAS2R38 (rs713598), and LTF (rs4547741) genes and early childhood caries (ECC) in Saudi preschool children. This case-control study enrolled 360 Saudi preschool children (262 with ECC and 98 caries-free). Data on environmental factors were collected through a questionnaire. However, caries experience and oral hygiene data were obtained during clinical examination. Buccal swab samples were collected for DNA extraction and SNPs were genotyped using PCR and DNA sequencing. Children with ECC were compared to caries free children (control), then they were categorized into two categories based on ECC severity as follows; non-severe ECC (NS-ECC), and severe-ECC (S-ECC). Association between the SNPs, ECC, NS-ECC, and S-ECC was reported as an odds ratio (OR) with a 95% confidence interval (CI). The majority of the children (72.8%) exhibited ECC (31.7% NS-ECC and 41.1% S-ECC) with mean dmft of 4.20 ± 4.05. Multivariate analyses of environmental factors showed that nocturnal feeding was a risk factor for ECC (P = 0.008). Poor oral hygiene was also a risk factor for both NS-ECC and S-ECC (ECC: P < 0.0001, NS-ECC: P = 0.032 and S-ECC: P < 0.0001). Univariate analysis showed that the AG genotype of rs1784418 of MMP20 gene was protective against ECC (OR = 0.532; 95% CI = 0.316–0.897, P = 0.018) and against NS-ECC (OR = 0.436; 95% CI = 0.238–0.798, P = 0.007). When environmental risk factors for ECC were included as covariates during multivariate analysis, AG variant in rs1784418 of MMP20 gene remained less frequent in NS-ECC cases compared to controls with borderline significance (OR = 0.542; 95% CI = 0.285–1.033, P = 0.063). Our findings concluded that MMP20 rs1784418 SNP might be associated with protection against ECC in Saudi preschool children.

MAP kinase phosphatase MKP-1 regulates p-ERK1/2 signaling pathway with fluoride treatment

Dental fluorosis is characterized by hypomineralization of tooth enamel caused by ingestion of excessive fluoride during enamel formation. Excess fluoride could have effects on the ERK signaling, which is essential for the ameloblasts differentiation and tooth development. MAP kinase phosphatase-1 (MKP-1) plays a critical role in regulating ERK related kinases. However, the role of MKP-1 in ameloblast and the mechanisms of MKP-1/ERK signaling in the pathogenesis of dental fluorosis are incompletely understood. Here, we adopted an in vitro fluorosis cell model using murine ameloblasts-like LS8 cells by employing sodium fluoride (NaF) as inducer. Using this system, we demonstrated that fluoride exposure led to an inhibition of p-MEK and p-ERK1/2 with a subsequent increase in MKP-1 expression in a dose-dependent manner. We further identified, under high dose fluoride, MKP-1 acted as a negative regulator of the fluoride-induced p-ERK1/2 signaling, leading to downregulation of CREB, c-myc, and Elk-1. Our results identify a novel MKP-1/ERK signaling mechanism that regulates dental fluorosis and provide a framework for studying the molecular mechanisms of intervention and fluorosis remodeling under normal and pathological conditions. MKP-1 inhibitors may prove to be a benefit therapeutic strategy for dental fluorosis treatment.

In the absence of a basal lamina, ameloblasts absorb enamel in a serumless and chemically defined organ culture system

ObjectivesTooth organ development was examined in a serumless, chemically defined organ culture system to determine whether morphological and functional development was identical to that in in vivo and serum-supplemented organ cultures. MethodsMouse mandibular first molar tooth organs at 16 days of gestation were cultured for up to 28 days in a Tronwell culture system using a serum-supplemented or serumless, chemically defined medium. After culture, specimens were processed for assessing tooth development using ultrastructural, immunohistochemical, and mRNA expression analyses. ResultsIn serum-supplemented conditions, inner enamel epithelial cells differentiated into secretory-stage ameloblasts, which formed enamel and reached the maturation stage after 14 and 21 days of culture, respectively. Ameloblasts deposited a basal lamina on immature enamel. Conversely, in serumless conditions, ameloblasts formed enamel on mineralized dentin after 21 days. Moreover, maturation-stage ameloblasts did not form basal lamina and directly absorbed mineralized enamel after 28 days of culture. RT-PCR analysis indicated that tooth organs, cultured in serumless conditions for 28 days, had significantly reduced expression levels of ODAM, amelotin, and laminin-322. ConclusionsThese results indicate that several differences were detected compared to the development in serum-supplemented conditions, such as delayed enamel and dentin formation and the failure of maturation-stage ameloblasts to form basal laminae. Therefore, our results suggest that some factors might be required for the steady formation of mineralized dentin, enamel, and a basal lamina. Additionally, our results indicate that a basal lamina is necessary for enamel maturation.

Diagnóstico y tratamiento integral en pacientes con Amelogénesis Imperfecta. Reporte de un caso

Objetivo: La Amelogénesis Imperfecta comprende un grupo heterogéneo de defectos del esmalte de origen genético, debidos a alteraciones en la formación del esmalte dentario, en calidad y/o cantidad. El diagnóstico se basa en la observación clínica, exámenes radiográficos, la historia familiar, el árbol genealógico y cuando es posible el diagnóstico genético. Se caracteriza por tener un amplio rango de presentaciones clínicas en ambas denticiones. Esta afección tiene un alto impacto en niños y adolescentes debido a que la carencia estética y la disfunción limitan su calidad de vida. La atención integral se convierte en un aspecto esencial y demanda una inteligente y necesaria interacción profesional, paciente y familia, la cual debe establecerse en forma temprana y de manera interdisciplinaria. Objetivo: Presentar un reporte de casocaso de un paciente de 11 años con Amelogénesis Imperfecta y diagnóstico clínico y radiográfico de tipo hipoplásico, apoyado en su historia familiar. El tratamiento integró varias etapas: uso de agentes remineralizantes a fin de restaurar los tejidos dentarios; ortodoncia para crear espacio para la erupción del canino retenido (13) y alineación de la arcada dentaria superior y rehabilitación dentaria con resinas compuestas y coronas metálicas fenestradas en oclusal. Conclusiones: El seguimiento por cinco años con una actitud muy positiva de la paciente hacia el mantenimiento de su salud, confirma que en el adolescente, una sonrisa saludable es importante en el desarrollo de la autoestima y las relaciones interpersonales.

ODAM promotes junctional epithelium‐related gene expression via activation of WNT1 signaling pathway in an ameloblast‐like cell line ALC

In this study, we investigated the potential and mechanism of odontogenic ameloblast-associated protein (ODAM) in the promoting junctional epithelium-related gene expression in an ameloblast-like cell line ALC. ODAM is expressed in ameloblasts and JE and acts as a component of the inner basal lamina (IBL) and intercellular matrix of JE. ODAM KO mice showed destruction of the integrity of the JE, which detaches from teeth. ODAM was confirmed to regulate the cytoskeleton through the ODAM-ARHGEF5-RhoA signaling pathway of the JE. Whether ODAM contributes to the regulation of ameloblast differentiation in JE remains unclear. After the formation of enamel, the ameloblast undergoes a series of morphological changes. Whether ODAM will affect the biological behavior of ameloblasts making them have the characteristics of JE is unclear. A murine ameloblast-like cell line, ALC, was used to investigate the effects of ODAM on the JE-like changes of ALC cells in an epithelium-induced environment by generating ODAM overexpression and ODAM knockdown cells through a lentivirus transduction approach. The biomarkers of junctional epithelium CK19, SLPI, and ODAM and the potential regulatory gene WNT1 were investigated by real-time PCR, western blot, immunocytochemistry, immunostaining, luciferase reporter, and rescue assays. ODAM, CK19, and SLPI were significantly upregulated after epithelial induction. Overexpression of ODAM in ALC cells markedly increased CK19 and SLPI expression, while knockdown of ODAM in ALC cells clearly decreased CK19 and SLPI expression. A reporter luciferase assay showed that ODAM activated the WNT signaling pathway, especially through WNT1. Exogenous overexpression of ODAM upregulated WNT1 expression, while knockdown of ODAM reversed this effect. The WNT1 inhibition assay further confirmed the above results and showed that the WNT1 pathway was positively correlated with biomarkers of junctional epithelium CK19 and SLPI expression. Rescue studies showed that knocking down WNT1 in the ODAM-overexpressing ALC cells decreased the expression of CK19 and SLPI. Immunocytochemistry showed that ODAM colocalized with CK19, SLPI, and WNT1 in the cells. In conclusion, the research work showed that ODAM promotes junctional epithelium-related gene expression in ALC via the ODAM-WNT1 axis, which may provide new insight into the function of ODAM and JE formation.

Analysis of Protein Immunoexpression and Its Interrelationship in the Pathogenesis of Odontomas and Ameloblastic Fibro-Odontomas: A Systematic Review.

Odontomas and ameloblastic fibro-odontomas (AFOs) are the result of a developmental anomaly of odontogenic tissues. A literature review of proteins immunoexpressed in odontomas and AFOs was conducted in order to determine which proteins are involved in the pathogenesis of these lesions. AFO was changed to early odontoma in the 2017 WHO classification and will also be discussed in this article. A literature search was performed in the following electronic databases: PubMed/MEDLINE, Web of Science, Scopus, EMBASE, Lilacs, Cochrane Collaboration Library, and Science Direct. The research question was developed according to the population, intervention, comparison, and outcome (PICO) framework: Which proteins are related to the differentiation of odontomas and what is their interrelationship with AFOs? Thirty articles met all inclusion criteria and were selected for this systematic review, totaling 355 cases of odontomas and 43 cases of AFO. Similar immunoexpression was observed in odontomas and AFOs. Immunoexpression of proteins involved in cell differentiation was higher in compound odontomas than in complex odontomas. Proteins involved in histodifferentiation and enamel formation were more frequent in odontomas. The immunoexpression of enamel matrix proteins differs between odontomas and tooth germs, with their persistence being related to the development of odontomas. Compound odontomas exhibit the highest immunoexpression of proteins involved in cellular histodifferentiation and the Wnt/beta-catenin pathway is involved in tumor formation.

Ameloblasts in Health and Disease

Abstract Ameloblasts are highly sensitive enamel-forming cells. They are derived from ectoderm and undergo a series of transformative changes in their life cycle. The functional efficiency of ameloblasts depends on various factors such as intracellular and extracellular environment, epithelial–mesenchymal interactions, and genetic control. Enamel formation is a well-organized event in the life cycle of ameloblasts. Normal enamel formation is the sign of healthy ameloblasts. The well-being of ameloblasts would be under threat in multiple situations. Internal regulatory mechanisms that are influenced by genetic mutations will lead to abnormal behavior of the cell. Environmental factors such as trauma, infection, exposure to chemicals, nutritional deficiencies, and hormonal dysregulation would affect the cell's normal behavior, which leads to abnormal enamel production. In this article, factors affecting the health of ameloblasts are described briefly.

Amelotin-Mediated Crystals Assembly in Liquid-Phase and on Tooth Surface

Objectives: To study the role of amelotin in enamel formation, purified recombinant human amelotin was used in a study of amelotin self assembly and its role in new HAP crstal structure formation in a laboratory setting. Methods: The full-length human amelotin gene was cloned from developing tooth buds and recombinant amelotin was expressed and purified. Morphological changes during amelotin self-assembly and the role of amelotin in promoting new minieralization structure is studied using Transmission electronic microscopy and Scanning electron microscopy. Results: The measured molecular weight of expressed human amelotin was 28 kDa that matches the predicted values. Amelotin self-assembles to form nano-spheres 10 - 30 nm in size. The amelotin self-assembly process further produces higher 3-D structure in the forms of chain-like fabric arranged in parallel and perpendicular direction. The neonatal pearl crystals were arranged side by side to form a string of small rods and small parallel rods extend from the demineralized glaze on the surface of teeth that were pre-treated with amelotin.

Clinical Observation of the Effect of Erbium-Doped Yttrium Aluminium Garnet Laser on the Treatment of Pit and Fissure in Children

To apply erbium-doped yttrium aluminium garnet laser to the closure of young permanent teeth and pits, compare the total retention rate of sealants, and discuss whether erbium-doped yttrium aluminium garnet laser is suitable for clinical treatment in children. Sixty children with 6-9 y old and bilateral mandibular first molars with complicated sulcus were randomly divided into two groups: A and B. The self-half control method was used: group A children’s control side test teeth application of corundum The enamel was performed by enamel, acid etching, coating pit and fissure sealant, erbium-doped yttrium aluminium garnet laser enameloplasty was applied to the contralateral test teeth and pit and fissure sealant was applied; group B children’s control side test teeth were treated with group A. The contralateral test teeth were treated with erbium-doped yttrium aluminium garnet laser enameloplasty, acid etching, and coating pit and fissure sealant. The children were scored for treatment after surgery, and regular follow-up was performed to observe the retention of the sealant. 63.3 % of the children tested were willing to take the initiative to choose laser treatment. At the 3rd and 6th mo of follow-up, there was no significant difference in the total retention rate of the two groups of sealants (p>0.05); at the 12th and 18th mos of followup, the total retention rate of the sealant materials: laser+etchant group>traditional bur. The difference between the needle group and the laser group was statistically significant (p<0.05). Laser is a more acceptable treatment for children. Erbium-doped yttrium aluminium garnet laser is used in the formation of permanent enamel. It needs to be combined with acid etchant to enhance the retention of the sealant.

An inconstant biorhythm: The changing pace of Retzius periodicity in human permanent teeth

Human tooth enamel retains evidence of growth in the form of Retzius lines. The number of daily growth increments between the regularly occurring lines defines their repeat interval, or periodicity. Retzius periodicity is often incorporated into enamel formation times, age-at-death reconstructions, or used to provide a basis from which to explore an underlying biorhythm. Biological anthropologists typically assume that RP remains constant within an individual and does not vary along the tooth-row. Here, we test that assumption. RP was calculated from n = 223 thin sections of human permanent teeth from individuals of British and southern African origin. Forty individuals provided multiple teeth (n = 102 teeth) and a further 121 individuals each provided a single tooth. We report first evidence that RP of permanent teeth does not always remain constant within an individual. Of those individuals that provided multiple teeth, 42% (n = 17/40) demonstrated a decrease in RP along the tooth row, with most shifting by two or more days (n = 11). Across the entire sample, mean RP of anterior teeth was significantly higher than molars. Mean premolar RP tended to be intermediate between anterior teeth and molars. Our data do not support the assumption that RP invariably remains constant within the permanent teeth of an individual. Transferring RP from molars to incisors within an individual can result in a miscalculation of formation time and age-at-death by up to 1 year. Implications for biological anthropologists and the source of the underlying long period biorhythm are discussed.

Co-Immunoprecipitation Reveals Interactions Between Amelogenin and Ameloblastin via Their Self-Assembly Domains.

Macromolecular assembly of extracellular enamel matrix proteins (EMPs) is intimately associated with the nucleation, growth, and maturation of highly organized hydroxyapatite crystals giving rise to healthy dental enamel. Although the colocalization of two of the most abundant EMPs amelogenin (Amel) and ameloblastin (Ambn) in molar enamel has been established, the evidence toward their interaction is scarce. We used co-immunoprecipitation (co-IP) to show evidence of direct molecular interactions between recombinant and native Amel and Ambn. Ambn fragments containing Y/F-x-x-Y/L/F-x-Y/F self-assembly motif were isolated from the co-IP column and characterized by mass spectroscopy. We used recombinant Ambn (rAmbn) mutants with deletion of exons 5 and 6 as well as Ambn derived synthetic peptides to demonstrate that Ambn binds to Amel via its previously identified Y/F-x-x-Y/L/F-x-Y/F self-assembly motif at the N-terminus of its exon 5 encoded region. Using an N-terminal specific anti-Ambn antibody, we showed that Ambn N-terminal fragments colocalized with Amel from secretory to maturation stages of enamel formation in a single section of developing mouse incisor, and closely followed mineral patterns in enamel rod interrod architecture. We conclude that Ambn self-assembly motif is involved in its interaction with Amel in solution and that colocalization between the two proteins persists from secretory to maturation stages of amelogenesis. Our in vitro and in situ data support the notion that Amel and Ambn may form heteromolecular assemblies that may perform important physiological roles during enamel formation.

The forgotten contribution of J. E. Purkyně to dentistry

Objectives: the name of Jan Evangelista Purkyně (Purkinje in German), born in Bohemia in 1787 and died in Prague in 1869, is mainly associated with discoveries in histology and specialist fields of Medicine like embriology, histological techniques, ophthalmology, cardiology and neurophysiology. This short article presents a brief account of his life, commemorates his achievements in biology and medicine but also in in the politics and literature of his Country (he was elected to the Diet of Bohemia but also he composed poems and important translations from German, French and Italian languages into Czech) and examines in depth his contribution to Dentistry. Materials and Methods: Purkyně’s major contributions to Dentistry, which focused on embryology and dental histology, endodontics and periodontology, are traced to two dissertations in Latin which were discussed by his pupils (Meyer Fraenkel and Isaac Raschkow), at Breslau University in 1835: we present a brief summary of each, with the major innovative findings highlighted. Results: the two dissertations contain remarkable, though often overlooked, contributions to Dentistry. Among these we can indicate the individuation of: the dental cement (substantia ostoidea), the acquired dental pellicle, the nature of optical illusion of Hunter-Schreger lines, the “enamel pulp” from which the enamel would evolve, the sub-odontoblastic nervous plexus which is the cause of tooth sensitivity, the predentine, the organic nature of the process of enamel formation, the dentine and enamel formation in opposing directions, the presence of alveolus membrane (id est: the periodontium). Conclusions: after reviewing the main innovations these two dissertations made to Dentistry, Purkyně’s personal share in both is very clear. Both the two his pupils acknowledged their debt to Purkyně and also famous contemporary Purkinje scientists such as Alexander Nasmyth, Sir Richard Owen, Sir James Paget had no doubt he is had generated the ideas expressed in the two little treatises.

Characterization of AMBN I and II Isoforms and Study of Their Ca2+-Binding Properties.

Ameloblastin (Ambn) as an intrinsically disordered protein (IDP) stands for an important role in the formation of enamel—the hardest biomineralized tissue commonly formed in vertebrates. The human ameloblastin (AMBN) is expressed in two isoforms: full-length isoform I (AMBN ISO I) and isoform II (AMBN ISO II), which is about 15 amino acid residues shorter than AMBN ISO I. The significant feature of AMBN—its oligomerization ability—is enabled due to a specific sequence encoded by exon 5 present at the N-terminal part in both known isoforms. In this study, we characterized AMBN ISO I and AMBN ISO II by biochemical and biophysical methods to determine their common features and differences. We confirmed that both AMBN ISO I and AMBN ISO II form oligomers in in vitro conditions. Due to an important role of AMBN in biomineralization, we further addressed the calcium (Ca2+)-binding properties of AMBN ISO I and ISO II. The binding properties of AMBN to Ca2+ may explain the role of AMBN in biomineralization and more generally in Ca2+ homeostasis processes.

Epithelial loss of mitochondrial oxidative phosphorylation leads to disturbed enamel and impaired dentin matrix formation in postnatal developed mouse incisor

The formation of dentin and enamel matrix depends on reciprocal interactions between epithelial-mesenchymal cells. To assess the role of mitochondrial function in amelogenesis and dentinogenesis, we studied postnatal incisor development in K320E-TwinkleEpi mice. In these mice, a loss of mitochondrial DNA (mtDNA), followed by a severe defect in the oxidative phosphorylation system is induced specifically in Keratin 14 (K14+) expressing epithelial cells. Histochemical staining showed severe reduction of cytochrome c oxidase activity only in K14+ epithelial cells. In mutant incisors, H&E staining showed severe defects in the ameloblasts, in the epithelial cells of the stratum intermedium and the papillary cell layer, but also a disturbed odontoblast layer. The lack of amelogenin in the enamel matrix of K320E-TwinkleEpi mice indicated that defective ameloblasts are not able to form extracellular enamel matrix proteins. In comparison to control incisors, von Kossa staining showed enamel biomineralization defects and dentin matrix impairment. In mutant incisor, TUNEL staining and ultrastructural analyses revealed differentiation defects, while in hair follicle cells apoptosis is prevalent. We concluded that mitochondrial oxidative phosphorylation in epithelial cells of the developed incisor is required for Ca2+ homeostasis to regulate the formation of enamel matrix and induce the differentiation of ectomesenchymal cells into odontoblasts.

Molar crown formation times of fossil orangutan molars from Guangxi, China.

We aimed to investigate molar enamel development in fossil orangutans from Guangxi and shed light on the evolution of Asian great apes. We collected 32 fossil orangutan molars, most of which were from Guangxi apothecaries and the Guangxi Daxin Heidong cave, and prepared histological sections of each molar. We then characterized aspects of dental development, including long period line periodicity, number of Retzius lines and lateral enamel formation time, cuspal enamel thickness, and enamel formation time. The long period line periodicity in fossil orangutans ranged from 9 to 10 days (mean, 9.09 days). The molar lateral enamel formation time ranged from 1.48 to 3.17 years (540-1,152 days). Cuspal enamel thickness in fossil orangutan molars ranged from 949 to 2,535 μm, and cuspal enamel formation time ranged from 0.64 to 1.87 years. Molar enamel formation time of fossil orangutans ranged from 2.47 to 4.67 years. Long-period line periodicity of fossil orangutans from Guangxi was within the variation range of extant orangutans, and the average long period line periodicity (9.09 days) of fossil orangutans from Guangxi in this study was lower than the values for extant orangutans (9.5 days) and fossil orangutans (10.9 days) from Sumatra and Vietnam. Orangutan enamel thickness may have gradually decreased from the Middle Pleistocene to Holocene. Crown formation time of fossil orangutans was slightly longer than that of extant orangutans, and the M1 emergence age of fossil orangutans from Guangxi was about 4-6 years. These findings might indicate the regional difference or evolutionary changes in orangutans since Pleistocene. Dental development of the Guangxi fossil orangutans were more similar to that of Asian Miocene apes, suggesting the closer evolutionary relationship of orangutans to Miocene Asian fossil apes.

New insight into dental epithelial stem cells: Identification, regulation, and function in tooth homeostasis and repair.

Tooth enamel, a highly mineralized tissue covering the outermost area of teeth, is always damaged by dental caries or trauma. Tooth enamel rarely repairs or renews itself, due to the loss of ameloblasts and dental epithelial stem cells (DESCs) once the tooth erupts. Unlike human teeth, mouse incisors grow continuously due to the presence of DESCs that generate enamel-producing ameloblasts and other supporting dental epithelial lineages. The ready accessibility of mouse DESCs and wide availability of related transgenic mouse lines make mouse incisors an excellent model to examine the identity and heterogeneity of dental epithelial stem/progenitor cells; explore the regulatory mechanisms underlying enamel formation; and help answer the open question regarding the therapeutic development of enamel engineering. In the present review, we update the current understanding about the identification of DESCs in mouse incisors and summarize the regulatory mechanisms of enamel formation driven by DESCs. The roles of DESCs during homeostasis and repair are also discussed, which should improve our knowledge regarding enamel tissue engineering.

Caries experience among children born after a complicated pregnancy.

ObjectivesBehavioural and lifestyle factors, as oral hygiene and diet, are well‐established risk factors in the pathogenesis of dental caries, though displaying large differences in susceptibility across individuals. Since enamel formation already starts in utero, pregnancy course and outcome may eventually play a role in enamel strength and caries susceptibility. Therefore, we studied the association between history of pregnancy complications and the caries experience in their six‐year‐old children. The pregnancy complications included small for gestational age (SGA), spontaneous preterm birth (sPTB), gestational hypertension (GH), pre‐eclampsia (PE), individually, and a combination of those, designated as placental syndrome.MethodsThis study was embedded in Generation R, a prospective longitudinal Dutch multiethnic pregnancy cohort study. Information about pregnancy complications was obtained from questionnaires completed by midwives and obstetricians with cross‐validation in medical records. These included SGA, sPTB, GH and PE. Caries experience was assessed with the decayed, missing and filled teeth (dmft) index at a mean age of six years. The association between dental caries experience and a history of pregnancy complications was studied by using hurdle negative binomial (HNB) models.ResultsWe were able to assess the dmft index in 5323 six‐year‐old children (mean age 6.2 years, SD 0.5). We did not find an association between the different pregnancy complications and dental caries experience in childhood, whether for SGA, sPTB, GH, PE, or for the combined outcome placental syndrome (HNB estimates: OR 1.02, 95%CI 0.87 ‐ 1.19; RR 0.90, 95%CI 0.78 ‐ 1.04). Further adjustment of the models with different confounders did not alter the outcome.ConclusionsAlthough it is expected that prenatal stress can be a risk factor for caries development later in life, our findings do not support this hypothesis. Therefore, we believe disparities in caries experience between children are probably not explained by early life events during a critical intrauterine period of development.

“ NEW SYNDROME ASSOCIATING GINGIVAL FIBROMATOSIS AND DENTAL ABNORMALITIES – A CASE REPORT”

Gingival Fibromatosis is the overgrowth of the gingiva characterized by an expansion and accumulation of the connective tissue with the rarely presence of an increased number of cells. It is hereditary or is induced as a side effect of systemic drugs. As an inherited disorder, Gingival Fibromatosis may be part of a genetic syndrome or it may be isolated, in which case it is referred to as hereditary gingival fibromatosis. Some of the cases of Hereditary Gingival Fibromatosis associated with dental abnormalities like Amelogenesis Imperfecta. It is a general term for a number of conditions that affect enamel formation and/or calcification. The purpose of this article is to report manifesting syndrome characterized by Gingival Fibromatosis associated with dental abnormalities, including generalized thin hypoplastic Amelogenesis Imperfecta, intrapulpal calcifications, delay of tooth eruption, pericoronal radiolucencies in unerupted teeth, dental agenesis and root dilacerations.

G protein–coupled receptor Gpr115 (Adgrf4) is required for enamel mineralization mediated by ameloblasts

Dental enamel, the hardest tissue in the human body, is derived from dental epithelial cell ameloblast-secreted enamel matrices. Enamel mineralization occurs in a strictly synchronized manner along with ameloblast maturation in association with ion transport and pH balance, and any disruption of these processes results in enamel hypomineralization. G protein-coupled receptors (GPCRs) function as transducers of external signals by activating associated G proteins and regulate cellular physiology. Tissue-specific GPCRs play important roles in organ development, although their activities in tooth development remain poorly understood. The present results show that the adhesion GPCR Gpr115 (Adgrf4) is highly and preferentially expressed in mature ameloblasts and plays a crucial role during enamel mineralization. To investigate the in vivo function of Gpr115, knockout (Gpr115-KO) mice were created and found to develop hypomineralized enamel, with a larger acidic area because of the dysregulation of ion composition. Transcriptomic analysis also revealed that deletion of Gpr115 disrupted pH homeostasis and ion transport processes in enamel formation. In addition, in vitro analyses using the dental epithelial cell line cervical loop-derived dental epithelial (CLDE) cell demonstrated that Gpr115 is indispensable for the expression of carbonic anhydrase 6 (Car6), which has a critical role in enamel mineralization. Furthermore, an acidic condition induced Car6 expression under the regulation of Gpr115 in CLDE cells. Thus, we concluded that Gpr115 plays an important role in enamel mineralization via regulation of Car6 expression in ameloblasts. The present findings indicate a novel function of Gpr115 in ectodermal organ development and clarify the molecular mechanism of enamel formation.