Enamel Development Research Articles

Functional Role of Inorganic Trace Elements on Enamel and Dentin Formation: A Review.

Calcium and phosphate are the major components of hydroxyapatite crystals that form the inorganic portion of the teeth. Apart from these, certain elements are present in little amounts in enamel and dentin of the human teeth. Although they are required in minute quantities, their absence may alter healthy development of enamel and dentin and may result in developmental tooth defects as well as dental caries. Furthermore, excessive intake of some trace elements may inversely affect tooth development and health. The exact of effects that trace elements have on teeth and oral health is still an unexplored territory. The present paper reviews the presence of trace elements in teeth and their role in tooth health and development.

Expression and localization of amelotin, laminin γ2 and odontogenesis-associated phosphoprotein (ODAPH) on the basal lamina and junctional epithelium.

At maturation stage of enamel development, a specialized basal lamina (sBL) was built between ameloblasts and enamel. After the teeth eruption, the ameloblasts transform into the inner cell layer of junctional epithelium. The inner cell layer forms the internal basal lamina of junctional epithelium. However, the composition of the sBL and internal basal lamina was not clarified. The objective of our study was to make a description of the localization of amelotin (AMTN), laminin γ2 (LAMC2) and Odontogenesis-associated phosphoprotein (ODAPH) on the sBL and internal basal lamina. In immunohistochemical study, AMTN, LAMC2 and ODAPH were detected on the sBL at maturation stage. AMTN was also detected in ameloblasts at maturation stage. The expression of AMTN decreased from early-to-late maturation stage. In contrast, the expression of LAMC2 and ODAPH was stable. Immunofluorescence double-staining showed the localization of AMTN was close to enamel surface. However, the localization of ODAPH was close to ameloblasts. LAMC2 and ODAPH were observed on internal basal lamina of junctional epithelium. In contrast, no expression of AMTN was detected on internal basal lamina of junctional epithelium. Our results suggested that ODAPH might participate in enamel maturation and periodontal health, which might provide a better understanding of enamel defects and periodontal disease in clinic.

A Brief History of the Discovery of Amelogenin Nanoribbons In Vitro and In Vivo

Without evidence for an organic framework, biological and biochemical processes observed during amelogenesis provided limited information on how extracellular matrix proteins control the development of the complex fibrous architecture of human enamel. Over a decade ago, amelogenin nanoribbons were first observed from recombinant proteins during in vitro mineralization experiments in our laboratory. In enamel from mice lacking the enzyme kallikrein 4 (KLK4), we later uncovered ribbon-like protein structures that matched the morphology, width, and thickness of the nanoribbons assembled by recombinant proteins. Interestingly, similar structures had already been described since the 1960s, when enamel sections from various mammals were demineralized and stained for transmission electron microscopy analysis. However, at that time, researchers were not aware of the ability of amelogenin to form nanoribbons and instead associated the filamentous nanostructures with possible imprints of mineral ribbons in the gel-like matrix of developing enamel. Further evidence for the significance of amelogenin nanoribbons for enamel development was stipulated when recent mineralization experiments succeeded in templating and orienting the growth of apatite ribbons along the protein nanoribbon framework. This article provides a brief historical review of the discovery of amelogenin nanoribbons in our laboratory in the context of reports by others on similar structures in the developing enamel matrix.

The effect of Chronic Administration of Ampicillin/Sulbactum on rat Developing Enamel

Objective: This study aimed to evaluate the effect of chronic administration of Ampicillin/Sulbactum on enamel development of Albino rats’ mandibular first molar. Materials & Methods: Eight pregnant female Albino rats were equally divided into two groups: control and treated group. The treated group received intraperitoneal injection of 200 mg/kg BW of Ampicillin/Sulbactum once daily for nine days till delivery. This was followed by injection of the offspring for additional 11 days. Treated offsprings (n=7) were sacrificed at 12 day of birth and H&E stained sections of the mandibular first molar tooth germ were examined. The other half of the treated pups was sacrificed at 28 days of birth, their mandibular first molars were examined by quantitative computerized tomography (QCT), scanning electron microscope (SEM) & ground section then statistical analysis was performed for enamel measurements of H&E, ground sections and QCT Results: Examination of H&E stained sections of the Ampicillin/Sulbactam treated subgroup at 12 days revealed an apparent reduction in enamel matrix thickness which was statistically insignificant compared with control subgroup. QCT showed a significant decrease in enamel density of the treated subgroup compared with untreated subgroup at 28 days. SEM observation showed enamel surface irregularities, pores and fissures. An insignificant reduction in enamel thickness was revealed by statistical analysis of the ground sections under light microscope. Conculsion: Within the limitations of this study, chronic administration of Ampicillin/Sulbactam adversely affected the development of enamel in rat’s offspring.

Enamel Defects Associated With Dentin Sialophosphoprotein Mutation in Mice.

Dentin sialophosphoprotein (DSPP) is an extracellular matrix protein that is highly expressed in odontoblasts, but only transiently expressed in presecretory ameloblasts during tooth development. We previously generated a knockin mouse model expressing a mouse equivalent (DSPP, p.P19L) of human mutant DSPP (p.P17L; referred to as “DsppP19L/+”), and reported that DsppP19L/+ and DsppP19L/P19L mice manifested a dentin phenotype resembling human dentinogenesis imperfecta (DGI). In this study, we analyzed pathogenic effects of mutant P19L-DSPP on enamel development in DsppP19L/+ and DsppP19L/P19L mice. Micro-Computed Tomography (μCT) analyses of 7-week-old mouse mandibular incisors showed that DsppP19L/P19L mice had significantly decreased enamel volume and/or enamel density at different stages of amelogenesis examined. Acid-etched scanning electron microscopy (SEM) analyses of mouse incisors demonstrated that, at the mid-late maturation stage of amelogenesis, the enamel of wild-type mice already had apparent decussating pattern of enamel rods, whereas only minute particulates were found in DsppP19L/+ mice, and no discernible structures in DsppP19L/P19L mouse enamel. However, by the time that incisor enamel was about to erupt into oral cavity, distinct decussating enamel rods were evident in DsppP19L/+ mice, but only poorly-defined enamel rods were revealed in DsppP19L/P19L mice. Moreover, μCT analyses of the mandibular first molars showed that DsppP19L/+ and DsppP19L/P19L mice had a significant reduction in enamel volume and enamel density at the ages of 2, 3, and 24weeks after birth. Backscattered and acid-etched SEM analyses revealed that while 3-week-old DsppP19L/+ mice had similar pattern of enamel rods in the mandibular first molars as age-matched wild-type mice, no distinct enamel rods were observed in DsppP19L/P19L mice. Yet neither DsppP19L/+ nor DsppP19L/P19L mice showed well-defined enamel rods in the mandibular first molars by the age of 24weeks, as judged by backscattered and acid-etched SEM. In situ hybridization showed that DSPP mRNA level was markedly reduced in the presecretory ameloblasts, but immunohistochemistry revealed that DSP/DSPP immunostaining signals were much stronger within the presecretory ameloblasts in Dspp mutant mice than in wild-type mice. These results suggest that mutant P19L-DSPP protein caused developmental enamel defects in mice, which may be associated with intracellular retention of mutant DSPP in the presecretory ameloblasts.

A histological investigation of dental crown characters used in mosasaur phylogenetic analyses

Mosasaur researchers have used varieties of tooth crown ornamentation as diagnostic and phylogenetic characters for decades. Such tooth crown features include facets, flutes, striations, serrated carinae, and coarse anastomosing texture. This study investigates the relative contribution of dentine and enamel to the development of these dental characters and assesses possible homologies between these structures. Histological analysis of isolated mosasaur teeth revealed that flutes and facets develop initially from the dentine, and the external enamel morphology we observe macroscopically mirrors the shape the underlying dentine. Striations combine underlying contributions from the dentine with additional and irregular enamel deposition that results strictly from amelogenesis. In both serrated carinae and anastomosing texture the border between the dentine and the enamel is smooth, and these external ornamentations form through variations in enamel development. Based on these observations, we infer that flutes and facets are part of a morphological spectrum and should not be treated as separate phylogenetic characters. Conversely, striations develop differently than flutes and facets, and should therefore be treated as a distinct character. We recommend referring to the “serrations” on mosasaur carinae as crenulations to differentiate these enamel-only structures from true denticles possessing a dentine core. Anastomosing texture can also coincide with significant apical thickening, both of which could be adaptations for processing hard-shelled prey. Care must be taken when using tooth crown features as diagnostic or phylogenetic characters because seemingly different morphologies can have similar developmental origins, and tooth morphology can be more closely tied to diet than to common ancestry.

Effects of idiopathic hypoparathyroidism on tooth eruption of rats

Objective: To explore the effects of reduced parathyroid function in early growth and development on tooth eruption and enamel development by establishing an animal model of idiopathic hypoparathyroidism (IHP) and to explore the mechanism of IHP affecting tooth eruption with a view to provide experimental basis for early diagnosis and clinical treatment of IHP. Methods: Forty-eight SD rats at postnatal day 7 were randomly and equally divided into sham operation group and IHP group. The bilateral parathyroidectomy (PTX) was performed by using carbon nanoparticles technique to establish an IHP rat model, while no parathyroids were removed in the sham operation group using the same technique. Serum was extracted after surgery, serum calcium, serum phosphorus, and serum parathyroid hormone (PTH) concentrations were detected in order to verify the success of the modeling. At postnatal day 14, day 25 and day 38 (P14, P25 and P38) the rats were sacrificed to collect the mandible samples (six from each group) and to analyze the volume of enamel, the height of the tooth eruption and the bone microarchitecture parameters of the root-oriented alveolar bone of mandibular third molar quantitatively by micro-CT scanning. Histological sections were prepared. The distribution and expression levels of osteoblast differentiation markers runt-related transcription factor 2 (RUNX2) and osterix (OSX) in the alveolar bone around the third molar were detected by immunohistochemical staining and the osteoclast activity was detected by tartrate-resistant acid phosphatase (TRAP) staining. After each of the third molars was isolated, the microhardness of the enamel was measure by using a microhardness tester and the enamel microstructure was photographed by using scanning electron microscope. Primary dental follicle stem cells were isolated from other six mandibulars from each group at P14 and cultured in vitro. The cell proliferation activity was tested by cell colony forming units detection. After induction of dental follicle stem cells into osteogenic differentiation, the degree of mineralization was detected by using alkaline phosphatase staining and alizarin red staining. The mRNA of mandibular tissues and dental follicle cells were extracted, the expression of genes related to osteoblasts and osteoclast differentiations and parathyroid hormone receptor 1 (PTH1R) were detected by real-time quantitative PCR. Results: Bilateral parathyroidectomy was successfully performed on rats with the help of carbon nanoparticles under stereomicroscope. After surgery, the serum calcium concentration reduced, the serum phosphorus concentration increased and the serum PTH concentration distinctly reduced (P<0.01). The volume of enamel [(4.58±0.24) mm3] and the microhardness [(167.76±21.86) MPa] in IHP group were significantly lower than that in sham operation group [(5.22±0.46) mm3, P<0.05; (223.92±10.94) MPa, P<0.01, respectively]. The eruption height of the mandibular third molar in the IHP group was respectively lower than that in the sham operation group (P<0.05). The bone volume over total volume and trabecular number of the root-oriented alveolar bone of the mandibular third molars in the IHP group were respectively lower than that in sham operation group (P<0.05). The expression levels of RUNX2 and OSX proteins in the root-oriented alveolar bone of the mandibular third molars in the IHP group respectively reduced, compared to that in sham operation group (P<0.05). Furthermore, the number of osteoclasts (3.86±1.07) in crown-oriented alveolar bone in the IHP group was respectively lower than that in sham operation group (6.43±1.27) (P<0.01). The proliferative activity of dental follicle stem cells in the IHP group respectively decreased (P<0.01). After the induction of osteogenic differentiation, the mineralization ability of dental follicle stem cells in the IHP group was weakened. In the mandibular tissues of IHP group, the expression levels of osteogenesis related genes such as RUNX2 and OSX and the the expression of PTH1R significantly reduced (P<0.05). The receptor activator of nuclear factor-κB ligand/osteoprotegerin (RANKL/OPG) ratio reduced significantly (P<0.01) compared to those of sham operation group. Also in the dental follicle cells of IHP group, the expression levels of osteogenesis related genes such as RUNX2 and OSX, the RANKL/OPG ratio and the expression of PTH1R significantly decreased simultaneously compared to that in sham operation group (P<0.01). Conclusions: Under the condition of idiopathic hypoparathyroidism, the weakening of PTH/PTH1R signaling may reduce the proliferative activity of dental follicle stem cells, inhibit their regulation for osteoblast and osteoclast differentiations and functions, thereby interfere the bone remodeling of alveolar bone around the tooth germ during tooth eruption, which eventually leads to delayed tooth eruption.

ENAMEL PREPARATION AND TECHNOLOGY OF ART PRODUCTION

The purpose of the study is to highlight the process of preparation and disclosure of the technology of making works of art in the technique of hot enamel, as the basis of enamel art. The process of development of artistic enamel in Ukraine in the first quarter of the XXI century was supplemented by technological innovations. On the basis of the experimental approach, the artists developed the latest technologies, which became the basis of new directions of artistic and plastic expression – easel, monumental and plastic forms, artistic relief enamel. Systematic and complex approaches, chemical-physical and technical-technological methods were used to reveal the purpose of the research. The application of technical and technological method of enamel art research allows to reveal the attributive properties of the work, to assess the quality of its performance, to supplement the results of art analysis by revealing the essence of hot enamel technique and its impact on the author's style. The scientific novelty of the obtained results lies in the formulation and development of a topical topic, which in the scientific dimension has received insufficient coverage. The combination of technological methods and academic art research methods creates a synergy of understanding the significance of enamel art. The study of the application of enamel technologies contributes to the disclosure of the process of development of enamel art. The technology of making a work of art in the technique of artistic hot enamel is a complex labor-intensive process that requires not only the creative inspiration of the artist, but also the knowledge, skills and competencies associated with the technology of making the work. Enameling technology is divided into four stages: preparation of the work under the enamel, application of enamel, firing of enamel and processing of the work. Technical conditions affect the possibility of realization of the figurative and stylistic idea of the author. The results of understanding the essence of the process of technology and methods of enamel works can serve as an important component of the study of modern problems of art history and the development of enamel art. Key words: enamel art, technique, technology, hot enamel, cold enamel, artistic enamel.

Sequelae of congenital oropharyngeal teratoma in the oral cavity of the child

Congenital oropharyngeal teratoma is a rare tumor subtype with cells from the three germ layers, majorly being benign. Whereas teratoma develops early in intrauterine life, thus affecting the growth and development of adjacent structures, the purpose of this case report is to present the sequelae of this tumor in a child's oral cavity. Female child, 2 years and 3 months old referred by the otorhinolaryngologist for dental evaluation. The mother´s main complaint was the the child could not close her mouth. According to the child's medical record, at 34th week of gestation, during the routine ultrasound examination, the presence of the anechoic tumor mass was observed without Doppler signal, presenting a 3.2cm x 2.4cm diameter outside through the oral cavity. At 17 and 32 days of life, respectively, the excision of the largest and residual tumor located on the floor of the mouth was performed. Upon anatomopathological examination, the tumor with was classified as a mature teratoma. In the intraoral examination, a deep and atresia palate incomplete cleft palate, bone growth in the region of the posterior alveolar ridge of the maxilla, and in the posterior region of the mandible on the left side, "V" shaped mandible and microglossia, crowding were observed dental agenesis of the lower lateral incisors, absence of caries lesions, gingivitis and enamel development defects. The child will remain under the regular dental pediatric follow-up. Several sequelae were observed in the child's oral cavity and the need for multi-professional follow-up after excision of congenital oropharyngeal teratoma.

The absence of muscle segment homeobox 2 leads to the pyroptosis of ameloblasts by inducing squamous epithelial hyperplasia in the enamel organ.

Muscle segment homeobox 2 (MSX2) has been confirmed to be involved in the regulation of early tooth development. However, the role of MSX2 has not been fully elucidated in enamel development. To research the functions of MSX2 in enamel formation, we used a Msx2 −/− (KO) mouse model with no full Msx2 gene. In the present study, the dental appearance and enamel microstructure were detected by scanning electron microscopy and micro‐computed tomography. The results showed that the absence of Msx2 resulted in enamel defects, leading to severe tooth wear in KO mice. To further investigate the mechanism behind the phenotype, we performed detailed histological analyses of the enamel organ in KO mice. We discovered that ameloblasts without Msx2 could secrete a small amount of enamel matrix protein in the early stage. However, the enamel epithelium occurred squamous epithelial hyperplasia and partial keratinization in the enamel organ during subsequent developmental stages. Ameloblasts depolarized and underwent pyroptosis. Overall, during the development of enamel, MSX2 affects the formation of enamel by regulating the function of epithelial cells in the enamel organ.

Lif Deficiency Leads to Iron Transportation Dysfunction in Ameloblasts

Leukemia inhibitory factor (LIF), a member of the interleukin 6 family of cytokines, is involved in skeletal metabolism, blastocyst implantation, and stem cell pluripotency maintenance. However, the role of LIF in tooth development needs to be elucidated. The aim of the present study was to investigate the effect of Lif deficiency on tooth development and to elucidate the functions of Lif during tooth development and the underlying mechanisms. First, it was found that the incisors of Lif-knockout mice had a much whiter color than those of wild-type mice. Although there were no structural abnormalities or defective mineralization according to scanning electronic microscopy and computed tomography analysis, 3-dimensional images showed that the length of incisors was shorter in Lif−/− mice. Microhardness and acid resistance assays showed that the hardness and acid resistance of the enamel surface of Lif−/− mice were decreased compared to those of wild-type mice. In Lif−/− mice, whose general iron status was comparable to that of the control mice, the iron content of the incisors was significantly reduced, as confirmed by energy-dispersive X-ray spectroscopy (EDS) and Prussian blue staining. Histological staining showed that the cell length of maturation-stage ameloblasts was shorter in Lif−/− mice. Likewise, decreased expression of Tfrc and Slc40a1, both of which are crucial proteins for iron transportation, was observed in Lif−/− mice and Lif-knockdown ameloblast lineage cell lines, according to quantitative reverse transcription polymerase chain reaction, immunohistochemistry, and Western blot. Moreover, the upregulation of Tfrc and Slc40a1 induced by Lif stimulation was blocked by Stattic, a signal transducer and activator of transcription 3 (Stat3) signaling inhibitor. These results suggest that Lif deficiency inhibits iron transportation in the maturation-stage ameloblasts, and Lif modulates expression of Tfrc and Slc40a1 through the Stat3 signaling pathway during enamel development.

MMP20-generated amelogenin cleavage products prevent formation of fan-shaped enamel malformations

Dental enamel forms extracellularly as thin ribbons of amorphous calcium phosphate (ACP) that initiate on dentin mineral in close proximity to the ameloblast distal membrane. Secreted proteins are critical for this process. Enam−/− and Ambn−/− mice fail to form enamel. We characterize enamel ribbon formation in wild-type (WT), Amelx−/− and Mmp20−/− mouse mandibular incisors using focused ion beam scanning electron microscopy (FIB-SEM) in inverted backscatter mode. In Amelx−/− mice, initial enamel mineral ribbons extending from dentin are similar in form to those of WT mice. As early enamel development progresses, the Amelx−/− mineral ribbons develop multiple branches, resembling the staves of a Japanese fan. These striking fan-shaped structures cease growing after attaining ~ 20 µm of enamel thickness (WT is ~ 120 µm). The initial enamel mineral ribbons in Mmp20−/− mice, like those of the Amelx−/− and WT, extend from the dentin surface to the ameloblast membrane, but appear to be fewer in number and coated on their sides with organic material. Remarkably, Mmp20−/− mineral ribbons also form fan-like structures that extend to ~ 20 µm from the dentin surface. However, these fans are subsequently capped with a hard, disorganized outer mineral layer. Amelogenin cleavage products are the only matrix components absent in both Amelx−/− and Mmp20−/− mice. We conclude that MMP20 and amelogenin are not critical for enamel mineral ribbon initiation, orientation, or initial shape. The pathological fan-like plates in these mice may form from the lack of amelogenin cleavage products, which appear necessary to form ordered hydroxyapatite.

Defining the Role of MEMO1 in Craniodental Mineralization

Defects in the mineralization of craniofacial tissues are an underlying pathology in a variety of human congenital disorders. Our understanding of these developmental processes is confounded by the complex intertwinement of different tissue types (e.g. ectoderm, neural crest and mesoderm) and mineralization methods (e.g. endochondral and intramembranous ossification). Understanding the unique cellular and molecular mechanisms driving the development and mineralization of craniodental tissues (e.g. bone and teeth) is critical to explain, prevent, and treat associated genetic disorders. Our lab has identified the protein Mediator of Cell Motility 1 (MEMO1)—initially found to associate with breast cancer metastasis—is critical for bone and enamel mineralization. However, MEMO1’s biological and molecular function in these processes is unknown.We are using in vivo mouse-based and in vitro cell culture-based models to address this knowledge gap. With our in vivo models, we have utilized immunofluorescence, scanning electron microscopy, µCT, single cell RNA-sequencing, and basic histological examination to define the craniodental defects upon loss of Memo1 in the ectoderm or oral epithelium. With our in vitro models, we have utilized an oral epithelial cell line, along with CRISPR/Cas9 genome editing, Western Blot analysis, bulk RNA-sequencing and immunofluorescence to gain insight into the cellular and molecular function of MEMO1 within oral epithelial cells. Analyses of the in vivo Memo1 ectoderm or oral epithelial mutants, relative to controls, identifies an important role for MEMO1 in enamel development. Conditional mutants display chalky enamel associated with a significant decrease in enamel density (p-value < 0.03). Compromised enamel in conditional mutants is further supported by alterations in gene and protein expression within ameloblasts and may include defects in the cytoskeleton. Supporting this observation, our oral epithelial in vitro Memo1 loss-of-function model displays changes in cytoskeletal dynamics, including increased cellular contractility.These findings provide novel insight into how MEMO1 contributes to mineralization, potentially deploying its breast cancer metastatic function (i.e., cytoskeletal regulation), within a novel biological setting—amelogenesis. The oral epithelial specific role of MEMO1 expands our understanding of craniodental mineralization and MEMO1’s molecular control of these processes. Furthermore, this provides novel insight into genetic diseases of mineralization, including those impacting the craniodental complex. Additional investigation into our Memo1 loss-of-function models will progress both the specific and general knowledge of tissue mineralization—providing novel opportunities to exploit this protein, or its interacting partners, in a clinical or therapeutic setting.

Effect of amoxicillin on the enamel mineralization of SD rats

Objective: To determine whether amoxicillin had an effect on the enamel mineralization of SD rats. Methods: Eighteen SD rats were randomly divided into three groups. The rats in the control group were given distilled water. The rats in two experimental groups were administered 50 or 100 mg/kg amoxicillin by intragastric administration from day 3 to day 17 after birth. The general condition, the structure of liver and kidney, the enamel surface changes of mandibular first molars and incisors were observed. The changes of Ca/P ratio on enamel surface were analyzed by X-ray energy dispersive spectrometer (EDS). The surface morphology after phosphoric acid treatment was examined by scanning electron microscopy (SEM). Histological changes in the ameloblasts of mandibular incisors were analyzed by hematoxylin and eosin (HE) staining. Results: Compared with the control group, the general conditions as well as liver and kidney structures of SD rats in 50 and 100 mg amoxicillin groups had no significant differences. There was no obvious chalky changes on the first mandibular molars of SD rats in each group. All the incisors in 50 and 100 mg groups showed different degrees of chalkiness in the labial incisal 1/3 enamel. X-ray EDS analysis showed that the Ca/P ratios of occlusal and incisal 1/3 enamel in 50 and 100 mg groups (occlusal 1/3 of mandibular first molars: 1.51±0.03 and 1.52±0.02, incisal 1/3 of mandibular incisors: 1.46±0.01 and 1.43±0.01) was significantly lower than that in the control group (occlusal 1/3 of mandibular first molars: 1.67±0.41, incisal1/3 of mandibular incisors: 1.73±0.07) (P<0.05). However, there was no significant differences in the cervical 1/3 Ca/P ratio of mandibular first molars and incisors among the three groups (mandibular first molars: 1.56±0.04 for control group, 1.59±0.05 for 50 mg group and 1.57±0.04 for 100 mg group; incisors: 1.52±0.02 for control group, 1.47±0.01 for 50 mg group and 1.51±0.03 for 100 mg group) (P>0.05). SEM observation showed that the enamel rods of the first molars and incisors in the 50 and 100 mg group varied in size and arranged disorderly. The spaces between the enamel rods were larger than that in the control group and some areas even appeared large pits. HE staining showed that the gaps between ameloblasts in 50 and 100 mg groups were significantly wider than that in the control group. Conclusions: Intake of amoxicillin during the period of enamel development of SD rats might affect enamel mineralization.

JNK Signaling Pathway Mediates Fluoride-Induced Upregulation of CK1α during Enamel Formation

Fluorosis is a defect in the enamel mineral content caused by excessive fluoride intake during amelogenesis; the interaction of various factors in the development and progression of fluorosis has not been defined. Casein kinase 1α (CK1α) is constitutively active in cells and is involved in diverse cellular processes; however, its expression in fluorosis has not been measured. This study aimed to investigate the effects of fluoride on CK1α expression and to assess the regulation of molecular signaling involving fluoride and CK1α during enamel development. Kunming mice were randomly divided into the control and F groups with induced clinical features of fluorosis. The F group mice, including mothers and newborns, were treated with 50 ppm fluoridated water. Immunohistochemical staining of the sections of the embryonic mandible regions was performed at the bell stage. Protein expression and signaling pathways in a mouse-derived ameloblast-like cell line (LS8) exposed to fluoride or a Jun N-terminal kinase (JNK) inhibitor were compared to those in control cells without exposure. CK1α and proteins of the JNK signaling pathways were assayed by quantitative real-time PCR and Western blotting. Mice of the F group developed dental fluorosis. Scanning electron microscopy showed a significant reduction in the degree of mineralization in the F group mice, which manifested as thin, loosely arranged, and disorganized enamel rods. Additional analysis revealed that the expression of CK1α in the F group was significantly elevated compared with that in the control group; LS8 cells responded to fluoride by upregulation of CK1α expression through the JNK pathway. Our findings identified the potential effects of CK1α on fluorosis using a mouse model and revealed that a high fluoride level increases the expression of CK1α and that JNK can be a key regulatory factor in CK1α expression.

Exploring Eating Challenges and Food Selectivity for Latinx Children with and without Autism Spectrum Disorder Using Qualitative Visual Methodology: Implications for Oral Health.

Diet and food choices significantly impact teeth, including enamel quality and development of dental caries. However, studies focusing on diet and its relation to oral care in Latinx children with and without Autism Spectrum Disorders (ASD) have been minimally addressed in research. This qualitative study used an inclusive visual methodology to explore what Latinx caregivers learned about their child’s diet preferences and food routines in relation to their oral health. As a secondary aim, the study sought to explore whether notable differences in diet emerged between Latinx children with and without ASD. Participants were 32 Latinx caregivers from 18 families with children with and without Autism (n = 8 with a typically developing child and n = 10 with a child with ASD) who completed a food journal activity and photo elicitation interview. Interviews were thematically coded for themes pertaining to parents’ perceptions of their child’s diet and oral health. Findings of this study indicate that the process of taking photos helped Latinx caregivers to better situate the barriers and behaviors influencing everyday food routines in their children within the context of relating to their overall oral health. Via their active participation in the research process, parents were empowered to note strategies they could employ that would directly impact their child’s oral health outcomes, such as reducing juice intake and monitoring sugar consumption. Therefore, visual research methodologies are an important strategy for researchers to consider in order to empower participants to be part of the research process and part of the outcomes, and to offer better understanding of the lived experience of populations underrepresented in the literature, such as Latinx children with and without ASD and their families.

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

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.

In vivo effect of fluoride combined with amoxicillin on enamel development in rats.

Some evidence in vitro suggested that amoxicillin and fluoride could disturb the enamel mineralization. Objective: To assess the effect of amoxicillin and of the combination of amoxicillin and fluoride on enamel mineralization in rats. Methodology: In total, 40 rats were randomly assigned to four groups: control group (CG); amoxicillin group (AG - amoxicillin (500 mg/kg/day), fluoride group (FG - fluoridated water (100 ppm -221 mg F/L), and amoxicillin + fluoride group (AFG). After 60 days, the samples were collected from plasma and tibiae and analyzed for fluoride (F) concentration. The incisors were also collected to determine the severity of fluorosis using the Dental Fluorosis by Image Analysis (DFIA) software, concentration of F, measurements of enamel thickness, and hardness. The data were analyzed by ANOVA, Tukey’s post-hoc test, or Games-Howell post-hoc test (α=0.05). Results: Enamel thickness of the incisors did not differ statistically among the groups (p=0.228). Groups exposed to fluoride (AFG and FG) have higher F concentrations in plasma, bone and teeth than those not exposed to fluoride (CG and AG). The groups showed a similar behavior in the DFIA and hardness test, with the FG and AFG groups showing more severe fluorosis defects and significant lower hardness when compared with the AG and CG groups, with no difference from each other. Conclusion: The rats exposed to fluoride or fluoride + amoxicillin developed dental fluorosis, while exposure to amoxicillin alone did not lead to enamel defects.

СИСТЕМА ЛАКОКРАСОЧНОГО ПОКРЫТИЯ НА ОСНОВЕ ПОЛИУРЕТАНОВОЙ ЭМАЛИ ХОЛОДНОЙ СУШКИ ДЛЯ ЗАЩИТЫ НОСОВЫХ ОБТЕКАТЕЛЕЙ САМОЛЕТОВ

Recently in the aviation industry there has been an increasing demand for the development of functional paints and varnishes, in particular, for the production of coatings intended to protect aviation equipment from abrasion and erosion damaged. Coatings of this type are especially relevant for polymer products. This work is devoted to the development of a new polyurethane enamel for the protection of antenna radomes. The comparative data of fluoroplastic, polyurethane imported enamel, enamels based on chlorosulfonated polyethylene and fluorinated rubber, intended for protection of abrasive damage.

The Dual Effects of Reactive Oxygen Species on the Mandibular Alveolar Bone Formation in SOD1 Knockout Mice: Promotion or Inhibition.

The status of reactive oxygen species (ROS) correlates closely with the normal development of the oral and maxillofacial tissues. Oxidative stress caused by ROS accumulation not only affects the development of enamel and dentin but also causes pathological changes in periodontal tissues (periodontal ligament and alveolar bone) that surround the root of the tooth. Although previous studies have shown that ROS accumulation plays a pathologic role in some oral and maxillofacial tissues, the effects of ROS on alveolar bone development remain unclear. In this study, we focused on mandibular alveolar bone development of mice deficient in superoxide dismutase1 (SOD1). Analyses were performed using microcomputerized tomography (micro-CT), TRAP staining, immunohistochemical (IHC) staining, and enzyme-linked immunosorbent assay (ELISA). We found for the first time that slightly higher ROS in mandibular alveolar bone of SOD1(-/-) mice at early ages (2-4 months) caused a distinct enlargement in bone size and increased bone volume fraction (BV/TV), trabecular thickness (Tb.Th), and expression of alkaline phosphatase (ALP), Runt-related transcription factor 2 (Runx2), and osteopontin (OPN). With ROS accumulation to oxidative stress level, increased trabecular bone separation (Tb.Sp) and decreased expression of ALP, Runx2, and OPN were found in SOD1(-/-) mice at 6 months. Additionally, dosing with N-acetylcysteine (NAC) effectively mitigated bone loss and normalized expression of ALP, Runx2, and OPN. These results indicate that redox imbalance caused by SOD1 deficiency has dual effects (promotion or inhibition) on mandibular alveolar bone development, which is closely related to the concentration of ROS and the stage of growth. We present a valuable model here for investigating the effects of ROS on mandibular alveolar bone formation and highlight important roles of ROS in regulating tissue development and pathological states, illustrating the complexity of the redox signal.