Search Results (45)

Objective: This study aimed to assess, through a systematic review, the potential link between bisphenol A (BPA) exposure and molar incisor hypomineralization (MIH). Methods: A systematic review was performed according to the PRISMA grid. All international studies—in vitro, in vivo, or clinical—evaluating the relationships between bisphenol A and MIH were included. An iterative search of eligible publications was conducted on May 26, 2025, using three different databases: PubMed, Science Direct, and Google Scholar. Results: Eleven studies were included in the review, ten of which were experimental studies. They were published between 2013 and 2024. Among the selected articles, a rat model was used in eight studies and seven established a link between MIH and BPA (63.64% of the articles). In the included studies, the incisors of rats treated with BPA presented asymmetrical white spots at the enamel level, with a phenotype similar to human MIH. The authors highlight the hypothesis of the implication of steroid receptors expressed by ameloblasts, in particular at the stage of maturation, thus impacting enamel quality. Conclusions: The results presented in this review highlight a trend in the interaction of bisphenol A with steroid receptors, thus affecting enamel quality. However, these associations are weak, and future studies should investigate cofactors modulating BPA’s role in the development of MIH. Full article

The junctional epithelium, which lines the inner gingival surface, seals the gingival sulcus to block the infiltration of food debris and pathogens. The junctional epithelium is derived from the reduced enamel epithelium, consisting of late developmental stage ameloblasts and accessory cells. No prior studies have investigated whether defective ameloblast differentiation or enamel matrix formation affects junctional epithelium anatomy or function. Here, we examined the junctional epithelium in mice exhibiting amelogenesis imperfecta due to loss-of-function mutations in the major enamel matrix protein amelogenin (Amelx^−/−) or the critical enamel matrix protease KLK4 (Klk4^−/−). Histological analyses demonstrated altered morphology and cell layer thickness of the junctional epithelium in Amelx^−/− and Klk4^−/− mice as compared to wt. Immunohistochemistry revealed reduced ODAM, laminin 5, and integrin α6, all of which are critical for the adhesion of the junctional epithelium to the enamel in Amelx^−/− and Klk4^−/− mice. Furthermore, we observed altered cell–cell adhesion and increased permeability of Dextran-GFP through the mutants’ junctional epithelium, indicating defective barrier function. Reduced β-catenin and Ki67 at the base of the junctional epithelium in mutants suggest impaired mitotic activity and reduced capacity to replenish continuously desquamated epithelium. These findings highlight the essential role of normal amelogenesis in maintaining junctional epithelium homeostasis. Full article

The sodium–citrate cotransporter (NaCT) plays a crucial role in citrate transport during amelogenesis. Mutations in the SLC13A5 gene, which encodes the NaCT, cause early infantile epileptic encephalopathy 25 and amelogenesis imperfecta. We analyzed developing pig molars and determined that the citrate concentrations in secretory- and maturation-stage enamel are both 5.3 µmol/g, with about 95% of the citrate being bound to mineral. To better understand how citrate might enter developing enamel, we developed Slc13a5^Flag reporter mice that express NaCT with a C-terminal Flag-tag (DYKDDDDK) that can be specifically and accurately recognized by commercially available anti-Flag antibodies. The 24-base Flag coding sequence was located immediately upstream of the natural translation termination codon (TAG) and was validated by Sanger sequencing. The general development, physical activities, and reproductive outcomes of this mouse strain were comparable to those of the C57BL/6 mice. No differences were detected between the Slc13a5^Flag and wild-type mice. Tooth development was extensively characterized using dissection microscopy, bSEM, light microscopy, in situ hybridization, and immunohistochemistry. Tooth formation was not altered in any detectable way by the introduction of the Flag. The Slc13a5^Flag citrate transporter was observed on all outer membranes of secretory ameloblasts (distal, lateral, and proximal), with the strongest signal on the Tomes process, and was detectable in all but the distal membrane of maturation-stage ameloblasts. The papillary layer also showed positive immunostaining for Flag. The outer membrane of odontoblasts stained stronger than ameloblasts, except for the odontoblastic processes, which did not immunostain. As NaCT is thought to only facilitate citrate entry into the cell, we performed in situ hybridization that showed Ank is not expressed by secretory- or maturation-stage ameloblasts, ruling out that ANK can transport citrate into enamel. In conclusion, we developed Slc13a5^Flag reporter mice that provide specific and sensitive localization of a fully functional NaCT-Flag protein. The localization of the Slc13a5^Flag citrate transporter throughout the ameloblast membrane suggests that either citrate enters enamel by a paracellular route or NaCT can transport citrate bidirectionally (into or out of ameloblasts) depending upon local conditions. Full article

Research on how a stratified oral epithelium gained the capability to create the hardest hydroxyapatite-based mineralized tissue produced biologically to protect the surfaces of teeth has been ongoing for at least 175 years. Many advances have been made in unraveling some of the key factors that allowed the innermost undifferentiated epithelial cells sitting on a skin-type basement membrane to transform into highly polarized cells capable of forming and controlling the mineralization of the extracellular organic matrix that becomes enamel. Genetic manipulation of mice has proven to be a useful approach for studying specific events in the amelogenesis developmental sequence but there have been pitfalls in interpreting loss of function data caused in part by conflicting literature, technical problems in tissue preservation, and the total amount of time spent on tooth development between different species that have led to equivocal conclusions. This critical review attempts to discuss some of these issues and highlight the challenges of characterizing amelogenesis in gene-targeted mouse models. Full article

The human laminin family is composed of five α, four β, and three γ chains. Laminins are heterotrimers of α, β, and γ chains. Laminins play critical roles during organogenesis, mostly as basement membrane components. The expression of all and the localization of most laminin chains were characterized in mouse developing teeth. Primary laminin isoforms in basement membranes along the inner enamel epithelium before the secretory stage and outside of the outer enamel epithelium were laminins 111 (α1β1γ1) and 511. The mouse laminin α3 chain has two variants, α3A and α3B. Although a basement membrane structure is absent, laminin 3A32 was localized along the secretory surface of the secretory stage ameloblast Tomes’ processes. Laminin 3A32 was localized along the atypical basement membrane of maturation stage ameloblasts and the specialized basement membrane of junctional epithelium facing the enamel surface. The endothelial basement membrane in the dental papilla and outside of the enamel organ contained laminins 411 and 511. Laminin 332 was detected in the extracellular matrix but not the basement membrane of the apical loop. Laminin 111 was localized in the extracellular matrix of the apical dental papilla without forming a visible basement membrane. These findings suggest the multifaceted functions of laminins in tooth development and set the foundation for functional investigations. Full article

Background: Ameloblastic carcinoma (AC) is a rare malignant odontogenic tumor with limited knowledge surrounding its pathogenesis, molecular pathways, clinical behavior, treatment, and prognosis. This 40-year literature scoping review aims to enhance the comprehension of this complex condition, looking closely at how AC works at molecular and pathophysiological levels and what causes it to develop. Methods: The PUBMED, Medline, Scopus, and Cochrane central databases were searched, including articles from 1984 to date. Articles reporting epidemiological, clinical, instrumental, and histopathological data were included. Results: Out of the 375 articles examined, 52 met the inclusion criteria, yielding a total of 80 cases of AC. All cases before 1984 were excluded from the analysis, as were all that did not provide information on patient survival. Several molecular mechanisms associated with its development and progression were identified; these help in early diagnosis. Moreover, AC can spread locally, making a radical surgical approach necessary. There is still no agreement on how to manage neck dissection. Surgical removal followed by monitoring is an important part of managing AC. Conclusions: Advancements in biological and molecular insights have the potential to facilitate earlier diagnosis and treatment. These could lead to improvements in patients’ quality of life and long-term survival. Full article

Molar incisor hypomineralization (MIH) is a dental condition that affects the enamel of permanent molars and/or incisors, often leading to tooth decay. Although several etiological hypotheses have come forward, including prenatal medical problems and postnatal illness, the pathogenesis of MIH is yet unclear. Aimed at exploring the epigenomic landscape of this dental condition, we collected dental tissue from a MIH-affected child and an age-matched control patient and investigated their DNA methylation status through an in-depth analysis of nanopore long-read sequencing data. We identified 780,141 CpGs with significantly different methylation levels between the samples; intriguingly, the density of these dinucleotides was higher in the regions containing genes involved in dental morphogenesis and inflammatory processes leading to periodontitis. Further examination of 54 genes associated with MIH or hypomineralized second primary molar disorders revealed very distinct methylation of intragenic transposable elements (SINEs, LINEs, and LTRs), while functional profiling analysis of 571 differentially methylated regions genome-wide uncovered significant enrichment processes including ameloblasts differentiation and calcium ion binding, as well as SP1 and other zinc finger transcription factors. Taken together, our findings suggest that DNA methylation could play a role in the pathogenesis of MIH and represent a stepping stone towards a comprehensive understanding of this multifactorial disorder. Full article

The actin cytoskeleton plays an important role in morphological changes of ameloblasts during the formation of enamel, which is indispensable for teeth to withstand wear, fracture and caries progression. This study reveals that the actin nucleator Cobl is expressed in ameloblasts of mandibular molars during amelogenesis. Cobl expression was particularly pronounced during the secretory phase of the enamel-forming cells. Cobl colocalized with actin filaments at the cell cortex. Importantly, our analyses show an influence of Cobl on both ameloblast morphology and cytoskeletal organization as well as on enamel composition. At P0, Cobl knock-out causes an increased height of ameloblasts and an increased F-actin content at the apical membrane. During the maturation phase, the F-actin density at the apical membrane was instead significantly reduced when compared to WT mice. At the same time, Cobl-deficient mice showed an increased carbon content of the enamel and an increased enamel surface of mandibular molars. These findings demonstrate a decisive influence of the actin nucleator Cobl on the actin cytoskeleton and the morphology of ameloblasts during amelogenesis. Our work thus expands the understanding of the regulation of the actin cytoskeleton during amelogenesis and helps to further elucidate the complex processes of enamel formation during tooth development. Full article

Background/Objectives: Odontogenic tumors in pediatric patients are uncommon; among all, the intraosseous occurrence of odontogenic myxoma is very rare, accounting for almost 8.5–11.6% of all odontogenic tumors in children. The radiological appearance is highly variable and is often responsible for the diagnostic delay and treatment. Methods: We report a case of odontogenic myxoma occurring in the posterior mandible of a 12-year-old female, found on a panoramic radiograph performed for the delayed eruption of the second inferior molar, treated by conservative surgery. A comprehensive analysis of the literature was also carried out. Results: The radiological features of the presented case were unique, as the lesion was encompassed within the uncompleted (developing) dental crown still unerupted, as confirmed by the macroscopic appearance. Then, the differential diagnosis included odontogenic fibroma, immature dental pulp or follicle from a developing tooth, and ameloblastic fibrodontoma. The histological examination led to the final diagnosis of odontogenic myxoma. As for the literature analysis, after a PRISMA-based selection of the papers, a total of 23 articles (case reports and case series on odontogenic myxomas in pediatric patients, a total of 33 cases) were finally selected and studied; all the pertinent data are widely discussed within the paper. Conclusions: The current case highlights the importance of the radiological investigation in pediatric patients when a delayed eruption lasts for several months, leading to an early diagnosis necessary to avoid more aggressive surgical therapies and possible recurrence; data from the literature about site of occurrence, sex, age, kind of surgical procedure, and recurrence rate are discussed too. Full article

Patients with diabetes mellitus (DM) have an increased risk of tooth decay caused by alterations in their tooth development and their oral environment, as well as a tendency to present with pulp infection due to compromised immune response. The present study analyzed the characteristic alterations in tooth development under DM conditions using incisors from db/db type 2 diabetic mouse model (T2DM mice). In micro-CT analyses, T2DM mice showed delayed dentin and enamel formation. Through transcriptomic analyses, pre-ameloblast- and pre-odontoblast-specific genes were found to be significantly decreased in the incisors of T2DM mice, whereas major ameloblast- and mature odontoblast-specific genes were not changed. Stem cell markers were decreased in T2DM mice compared to those from the control mice, suggesting that the stemness of dental pulp cells (DPCs) is attenuated in T2DM mice. In vitro analyses demonstrated that DPCs from T2DM mice have lower colony-forming units (CFU), slower propagation, and diminished differentiation characteristics compared to the control. These data suggest that T2DM conditions could impair the differentiation property of multiple progenitor/stem cells in the tooth, resulting in delayed tooth development in T2DM mice. Full article

ADAM10 is a multi-functional proteinase that can cleave approximately 100 different substrates. Previously, it was demonstrated that ADAM10 is expressed by ameloblasts, which are required for enamel formation. The goal of this study was to determine if ADAM10 is necessary for enamel development. Deletion of Adam10 in mice is embryonically lethal and deletion of Adam10 from epithelia is perinatally lethal. We therefore deleted Adam10 from ameloblasts. Ameloblast-specific expression of the Tg(Amelx-iCre)872pap construct was confirmed. These mice were crossed with Adam10 floxed mice to generate Amelx-iCre; Adam10^fl/fl mice (Adam10 cKO). The Adam10 cKO mice had discolored teeth with softer than normal enamel. Notably, the Adam10 cKO enamel density and volume were significantly reduced in both incisors and molars. Moreover, the incisor enamel rod pattern became progressively more disorganized, moving from the DEJ to the outer enamel surface, and this disorganized rod structure created gaps and S-shaped rods. ADAM10 cleaves proteins essential for cell signaling and for enamel formation such as RELT and COL17A1. ADAM10 also cleaves cell-cell contacts such as E- and N-cadherins that may support ameloblast movement necessary for normal rod patterns. This study shows, for the first time, that ADAM10 expressed by ameloblasts is essential for proper enamel formation. Full article

Excessive fluoride ingestion during tooth development can cause dental fluorosis. Previously, we reported that fluoride activates histone acetyltransferase (HAT) to acetylate p53, promoting fluoride toxicity in mouse ameloblast-like LS8 cells. However, the roles of HAT and histone acetylation status in fluoride-mediated gene expression remain unidentified. Here, we demonstrate that fluoride-mediated histone modification causes gene expression alterations in LS8 cells. LS8 cells were treated with or without fluoride followed by ChIP-Seq analysis of H3K27ac. Genes were identified by differential H3K27ac peaks within ±1 kb from transcription start sites. The levels of mRNA of identified genes were assessed using rea-time PCR (qPCR). Fluoride increased H3K27ac peaks associated with Bax, p21, and Mdm2 genes and upregulated their mRNA levels. Fluoride decreased H3K27ac peaks and p53, Bad, and Bcl2 had suppressed transcription. HAT inhibitors (Anacardic acid or MG149) suppressed fluoride-induced mRNA of p21 and Mdm2, while fluoride and the histone deacetylase (HDAC) inhibitor sodium butyrate increased Bad and Bcl2 expression above that of fluoride treatment alone. To our knowledge, this is the first study that demonstrates epigenetic regulation via fluoride treatment via H3 acetylation. Further investigation is required to elucidate epigenetic mechanisms of fluoride toxicity in enamel development. Full article

Putatively, tooth agenesis was attributed to the initiation failure of tooth germs, though little is known about the histological and molecular alterations. To address if constitutively active FGF signaling is associated with tooth agenesis, we activated Fgf8 in dental mesenchyme with Osr-cre knock-in allele in mice (Osr2-cre^KI; Rosa26R-Fgf8) and found incisor agenesis and molar microdontia. The cell survival assay showed tremendous apoptosis in both the Osr2-cre^KI; Rosa26R-Fgf8 incisor epithelium and mesenchyme, which initiated incisor regression from cap stage. In situ hybridization displayed vanished Shh transcription, and immunostaining exhibited reduced Runx2 expression and enlarged mesenchymal Lef1 domain in Osr2-cre^KI; Rosa26R-Fgf8 incisors, both of which were suggested to enhance apoptosis. In contrast, Osr2-cre^KI; Rosa26R-Fgf8 molar germs displayed mildly suppressed Shh transcription, and the increased expression of Ectodin, Runx2 and Lef1. Although mildly smaller than WT controls prenatally, the Osr2-cre^KI; Rosa26R-Fgf8 molar germs produced a miniature tooth with impaired mineralization after a 6-week sub-renal culture. Intriguingly, the implanted Osr2-cre^KI; Rosa26R-Fgf8 molar germs exhibited delayed odontoblast differentiation and accelerated ameloblast maturation. Collectively, the ectopically activated Fgf8 in dental mesenchyme caused incisor agenesis by triggering incisor regression and postnatal molar microdontia. Our findings reported tooth agenesis resulting from the regression from the early bell stage and implicated a correlation between tooth agenesis and microdontia. Full article

Epigenetic modulation, including histone modification, alters gene expression and controls cell fate. Histone deacetylases (HDACs) are identified as important regulators of dental pulp cell (DPC) mineralisation processes. Currently, there is a paucity of information regarding the nature of histone modification and HDAC expression in the dentine–pulp complex during dentinogenesis. The aim of this study was to investigate post-translational histone modulation and HDAC expression during DPC mineralisation and the expression of Class I/II HDACs during tooth development and in adult teeth. HDAC expression (isoforms −1 to −6) was analysed in mineralising primary rat DPCs using qRT-PCR and Western blot with mass spectrometry being used to analyse post-translational histone modifications. Maxillary molar teeth from postnatal and adult rats were analysed using immunohistochemical (IHC) staining for HDACs (1–6). HDAC-1, -2, and -4 protein expression increased until days 7 and 11, but decreased at days 14 and 21, while other HDAC expression increased continuously for 21 days. The Class II mineralisation-associated HDAC-4 was strongly expressed in postnatal sample odontoblasts and DPCs, but weakly in adult teeth, while other Class II HDACs (-5, -6) were relatively strongly expressed in postnatal DPCs and adult odontoblasts. Among Class I HDACs, HDAC-1 showed high expression in postnatal teeth, notably in ameloblasts and odontoblasts. HDAC-2 and -3 had extremely low expression in the rat dentine–pulp complex. Significant increases in acetylation were noted during DPC mineralisation processes, while trimethylation H3K9 and H3K27 marks decreased, and the HDAC-inhibitor suberoylanilide hydroxamic acid (SAHA) enhanced H3K27me3. These results highlight a dynamic alteration in histone acetylation during mineralisation and indicate the relevance of Class II HDAC expression in tooth development and regenerative processes. Full article

AMELX mutations cause X-linked amelogenesis imperfecta (AI), known as AI types IE, IIB, and IIC in Witkop’s classification, characterized by hypoplastic (reduced thickness) and/or hypomaturation (reduced hardness) enamel defects. In this study, we conducted whole exome analyses to unravel the disease-causing mutations for six AI families. Splicing assays, immunoblotting, and quantitative RT-PCR were conducted to investigate the molecular and cellular effects of the mutations. Four AMELX pathogenic variants (NM_182680.1:c.2T>C; c.29T>C; c.77del; c.145-1G>A) and a whole gene deletion (NG_012494.2:g.307534_403773del) were identified. The affected individuals exhibited enamel malformations, ranging from thin, poorly mineralized enamel with a “snow-capped” appearance to severe hypoplastic defects with minimal enamel. The c.145-1G>A mutation caused a -1 frameshift (NP_001133.1:p.Val35Cysfs*5). Overexpression of c.2T>C and c.29T>C AMELX demonstrated that mutant amelogenin proteins failed to be secreted, causing elevated endoplasmic reticulum stress and potential cell apoptosis. This study reveals a genotype–phenotype relationship for AMELX-associated AI: While amorphic mutations, including large deletions and 5′ truncations, of AMELX cause hypoplastic-hypomaturation enamel with snow-capped teeth (AI types IIB and IIC) due to a complete loss of gene function, neomorphic variants, including signal peptide defects and 3′ truncations, lead to severe hypoplastic/aplastic enamel (AI type IE) probably caused by “toxic” cellular effects of the mutant proteins. Full article