DENTAL ENAMEL FORMATION AND IMPLICATIONS FOR ORAL HEALTH AND DISEASE

Engineering quantum carbon dots unveiling quantum wave entanglement wave function on enamel substrate: A relativistic in-vitro study

OBJECTIVES

As artificial atoms, quantum dots are widely used in quantum information research since their individual energy levels may be precisely controlled using gate voltages. The purpose of the study was to modify carbon quantum dots (CQDs) and evaluate its effects on the structure, crystal orientation and mechanical properties of the enamel substrate along with antibacterial properties of CQDs.

MATERIALS AND METHODS

Enamel specimens of 4 mm × 4 mm × 3 mm were cut and CQD solution was dialyzed in deionized water mixed with urea solution and placed in microwave system (800 W) to obtain *CQD0.1 %-, **CQD0.2 %-, ***CQD0.3 %-, and *****CQD0.5 % for enamel blocks to be immersed for 2 weeks. X-ray diffraction analysis and density-functional theory (DFT) calculations were performed to determine degree of phase purity. Transmission electron microscopy (TEM) was used for imaging of CQDs and treated enamel, with zeta potential measured with Zetasizer. Raman spectra was acquired with spectral range of 400-2000 cm-1. Atomic force microscopy was performed with a peak force set at 200 nN. Lactobacillus biofilm was prepared on treated enamel substrates and analysed using confocal, scanning electron microscopy and TEM.

RESULTS

DFT calculations summarised improved lattice parameters of HAp***CQD0.3 %- and HAp***CQD0.5 %-. Zeta potential is least for salineS and is maximum for *****CQD0.5 %- distributed system. The salineS, and *CQD0.1 %- groups had comparable v₁PO₄³⁻ value, indicating consistent phosphate intensities. TEM successfully verified carbon dots as spherical. Enamel crystals aligned their c-axis perpendicular to the electron beam within 1° with CQDs treated specimens exhibiting misoriented-crystals. *****CQD0.5 %- group had highest elastic modulus and nano hardness with maximum shear stress. Calculated bond length and angles using XRD show higher measures (p < 0.05) in all CQD groups. *****CQD0.5 %- exhibited a fibre texture pattern with an orientational distribution resembling an angle distortion. Most bacteria in the biofilms fluoresced red in CQD groups with no colony chain formations observed with *****CQD0.5 %- group. CQDs assemblies were observed to cause explosive lysis through loss of cell integrity.

CONCLUSION

*****CQD0.5 %- modified enamel substrate displayed significant crystallite changes providing a novel option for fabrication of diverse functional CQDs aimed at modification of enamel tissue while possessing optimum antimicrobial properties.

A comprehensive review of recent advancements in microbial-induced mineralization: biosynthesis and mechanism, with potential implementation in various environmental, engineering, and medical sectors

Biomineralization has garnered profuse attention in multidisciplinary fields. Using this strategy, living things, including eukaryotes or prokaryotes, mediate the uptake of ions from the surrounding environment, followed by assembling and depositing them as greatly configured structures inside the organic matrix. The generated biominerals, including nanomaterials, possess outstanding hierarchical structures that exceed their chemically synthesized counterparts. Despite the significant progress achieved in microbial-mediated mineralization, several key knowledge gaps remain, including mechanisms controlling biomineralization pathways and the impact of environmental factors on mineral morphology, crystallinity, and stability. This review provides a comprehensive description of this biomineralization, which can be categorized into controlled, influenced, and induced biomineralization. Interestingly, we highlighted biologically-induced mineralization approaches, such as photosynthesis, methane oxidation, and nitrogen-based metabolic pathways, and identified various chemical interactions during mineral production following analytical chemistry. This review also extensively delineates updates on application of biominerals across all fields, commencing with the remediation of deleterious pollutants and biominerals exploited in industrial sectors, moving on to using them to reinforce soil, generate biocement for construction, and delving into their utilization in pharmaceutical applications to deliver drugs, repair teeth and bones, and combat cancer and pathogenic microorganisms. Moreover, the review outlines the drawbacks and adequate solutions for biomineralization, particularly CaCO₃-mediated processes, such as the generation of ammonium and nitrate during the CaCO₃ precipitation process and the relatively slow rate of microbial-mediated mineralization. Biomineralization inspired the fabrication of smart biomaterials, which combine biological advantages. Overall, this comprehensive review discusses updated research and highlights potential approaches to future studies.

Antimicrobial, remineralization, and infiltration: advanced strategies for interrupting dental caries

Dental caries, driven by plaque biofilm, poses a major oral health challenge due to imbalance in mineralization and demineralization. The primary objective in caries management is to maintain biofilm homeostasis while facilitating the repair and regeneration of dental hard tissues, thus restoring both structural integrity and functionality of affected teeth. Though antimicrobial and remineralization approaches haven shown promise, their standalone utilization without concurrent bacterial control or rebalancing lacks an integrated strategy to effectively arrest caries progression. Furthermore, according to the principles of minimally invasive dentistry, treatment materials should exhibit high permeability to ensure optimal sealing of demineralized tooth surfaces. The concept of interrupting dental caries (IDC) has emerged as a holistic approach, drawing upon extensive research encompassing three pivotal techniques: antibacterial strategies, remineralization therapies, and infiltration mechanisms, all of which are indispensable components in combating the progression of dental caries. In this review, we provide a comprehensive overview of the mechanisms and applications of antibacterial, remineralization, and infiltration technologies within the context of caries management. Additionally, we summarize advanced materials that align with the IDC concept, aiming to offer valuable insights for designing next-generation materials adept at preventing or halting caries progression efficiently.

Prenatal exposure to per-and polyfluoroalkyl substances and its association with Developmental Defects of Enamel (DDE) and dental caries in 4 years old children: Findings from Shanghai birth cohort

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants with potential health risks. While the association between PFAS and dental health is under-researched, this study aims to address this gap by investigating prenatal PFAS exposure in relation to Developmental Defects of Enamel (DDE) and dental caries in children.

METHODS

This study included 1,136 children from the Shanghai Birth Cohort, with maternal blood samples collected during early pregnancy to measure concentrations of 10 PFAS compounds. Oral health outcomes, assessed when the children were 4 years old, included the prevalence of DDE and dental caries, as well as DDE tooth count and the decayed, missing, and filled teeth (dmft) index. Logistic regression and zero-inflated negative binomial regression were used to examine associations between individual PFAS compounds and oral health outcomes. Restricted Cubic Splines (RCS) were used to explore potential nonlinear associations. Additionally, Bayesian Kernel Machine Regression (BKMR), Weighted Quantile Sum (WQS), and Quantile G-Computation (QGC) were employed to assess the joint effects of PFAS mixtures on the outcomes.

RESULTS

Individual PFAS compounds, particularly perfluorobutane sulfonate (PFBS) and perfluoroheptanoic acid (PFHpA), exhibited heterogeneous associations with DDE prevalence. PFBS was linked to an increased risk of DDE (OR: 1.37; 95%CI: 1.05, 1.80), while PFHpA showed a protective effect (OR: 0.72; 95%CI: 0.54, 0.97). No significant associations were observed between individual PFAS compounds and dental caries outcomes. Additionally, the study found a lack of significant associations between PFAS mixtures and the prevalence of DDE or dental caries, as well as the absence of any marked effects on DDE tooth count or dmft.

CONCLUSION

Although no overall association was observed between PFAS mixtures and oral health outcomes, certain short-chain PFAS compounds, such as PFBS and PFHpA, demonstrated distinct effects on enamel defects. Further research is warranted to clarify the biological mechanisms underlying these associations and to examine the role of PFAS exposure in other populations.

Dendritic polyglutamic acid-chelerythrine nanocomplex for the reversal of bacterial tooth decay

Caries begin with an imbalance between demineralization and remineralization due to the continuous acid production by cariogenic bacteria. However, the development of dental materials that could prevent and treat caries via a simple and efficient mechanism has always been a challenge. To address this issue, therapeutic nanoparticles composed of a dendritic polyglutamic acid (DPGlu) and chelerythrine (CHE) complex (DPGlu@CHE) were developed via hydrophobic interactions and hydrogen bonds. DPGlu@CHE could be adsorbed onto the tooth surface, releasing CHE rapidly under acidic conditions to remove cariogenic bacteria, subsequently inducing tooth surface remineralization in situ. Our results demonstrated that more than 99% of Streptococcus mutans on the tooth surface were killed, and 84% of the mechanical properties of tooth were restored within 2 weeks. Thus, DPGlu@CHE was proven to be a safe and effective enamel restoration material in vitro, and its safety was verified in vivo, making it a promising mouthwash ingredient to maintain dental health.

Evaluation of the effects of prenatal exposure to pregabalin and postnatal analysis of dental and mandibular bone tissue development in rat offspring

Pregabalin is a gabapentinoid indicated for the treatment of peripheral neuropathic pain, fibromyalgia, and as an adjuvant therapy for epilepsy. The aim of this study was to evaluate the effects of pregabalin on postnatal development, odontogenesis, and mandibular trabecular tissue using computed microtomography. Pregnant rats (N = 24) were divided into two groups: control group/placebo (C), and treated group (PGB). The PGB group received 200 mg/kg of pregabalin via gavage during the embryonic period and the C group received distilled water under the same design. On the 21st day of pregnancy, delivery occurred naturally. On the first postnatal day, the litters were reduced to four pups (2 males and 2 females) and followed up for 30 days. On postnatal day 30, eight animals from each group were randomly selected for analysis of the lower right first molar and adjacent trabecular bone. In the maternal parameters, the data revealed a significant decrease in body weight gain in addition to a smaller number of live pups. In the postnatal analysis, the exposed pups showed a significant decrease in weight and length and a delay in the eruption of the incisor teeth. Microtomography analysis revealed a significant reduction in enamel volume, a lower volume and percentage of open pores, lower total porosity, and a higher percentage of bone volume. The findings of this study showed that pregabalin altered the eruption chronology of the incisors, decreased enamel volume, affected the microarchitecture of mandibular trabecular bone, and impaired postnatal development. CONCEA-CEUA-UEL n. 11,174.2018.36, State University of Londrina, (UEL), Londrina, Paraná, Brazil; retrospectively registered on August 21, 2018.

KMT2D Regulates Tooth Enamel Development

Amelogenesis, the process of enamel formation, is tightly regulated and essential for producing the tooth enamel that protects teeth from decay and wear. Disruptions in amelogenesis can result in amelogenesis imperfecta, a group of genetic conditions characterized by defective enamel, including enamel hypoplasia, marked by thin or underdeveloped enamel. Mutations in the KMT2D (MLL4) gene, which encodes histone H3 lysine 4 methyltransferase, are associated with Kabuki syndrome, a developmental disorder that can involve dental anomalies such as enamel hypoplasia. However, the specific role of KMT2D in amelogenesis remains poorly understood. To address this gap, we generated a conditional knockout (cKO) mouse model with ectoderm-specific deletion of Kmt2d (Krt14-Cre;Kmt2dfl/fl, or Kmt2d-cKO) and characterized the resulting enamel defects using gross, radiographic, histologic, cellular, and molecular analyses. Micro-computed tomography and scanning electron microscopy revealed that adult Kmt2d-cKO mice exhibited 100% penetrant amelogenesis imperfecta, characterized by hypoplastic and hypomineralized enamel, partially phenocopying human Kabuki syndrome. Additionally, Kmt2d-cKO neonates developed molar tooth germs with subtle cusp shape alterations and mild delays in ameloblast differentiation at birth. RNA sequencing analysis of the first molar tooth germ at birth revealed that 33.7% of known amelogenesis-related genes were significantly downregulated in the Kmt2d-cKO teeth. Integration with KMT2D CUT&RUN sequencing results identified 8 overlapping genes directly targeted by KMT2D. Reanalysis of a single-cell RNA sequencing data set in the developing mouse incisors revealed distinct roles for these genes in KMT2D-regulated differentiation across various cell subtypes within the dental epithelium. Among these genes, Satb1 and Sp6 are likely direct targets involved in the differentiation of preameloblasts into ameloblasts. Taken together, we propose that KMT2D plays a crucial role in amelogenesis by directly activating key genes involved in ameloblast differentiation, offering insights into the molecular basis of enamel development and related dental pathologies.

Novel Roles of Nestin in Postnatal Root Formation

Background/Objectives: Nestin is an intermediate filament protein and a marker of odontoblasts, but its function in tooth and bone formation is largely unknown. This study aimed to determine whether Nestin plays a role in postnatal tooth formation. Methods: 4-week-old Nestin knockout (KO) mice were analyzed with a range of techniques, including X-ray imaging, uCT, backscattered and acid-etched casted SEM, FITC-confocal microscopy, H&E and TRAP staining, and immunohistochemistry. Results: The KO mice had no apparent difference in crown formation compared to age-matched wild-type (WT) but showed delayed molar eruption with reduced TRAP+ osteoclasts. More importantly, KO mice developed expanded predentin and shorter, thinner roots with irregular and shortened dentin tubules. Additionally, the Nestin KO mice exhibited a reduced cellular cementum mass with sharp reductions in DMP1, OPN, and BSP. Conclusions: These findings suggest that Nestin plays a critical role in the postnatal development of root dentin and cellular cementum.

Genetic polymorphisms associated with developmental defects of enamel: A systematic review

BACKGROUND

Polymorphisms in genes related to enamel formation and mineralization may increase the risk of developmental defects of enamel (DDE).

AIM

To evaluate the existing literature on genetic polymorphisms associated with DDE.

DESIGN

This systematic review was registered in the PROSPERO (CRD42018115270). The literature search was performed in PubMed, Scopus, Web of Science, LILACS, BBO, Cochrane Library, and in the gray literature. Observational studies assessing the association between DDE and genetic polymorphism were included. The Newcastle-Ottawa Scale was used to assess the risk of bias.

RESULTS

One thousand one hundred and forty-six articles were identified, and 28 met the inclusion criteria. Five studies presented a low risk of bias. Ninety-two genes related to enamel development, craniofacial patterning morphogenesis, immune response, and hormone transcription/reception were included. Molar-incisor hypomineralization (MIH) and/or hypomineralization of primary second molars (HPSM) were associated with 80 polymorphisms of genes responsible for enamel development, immune response, morphogenesis, and xenobiotic detoxication. A significant association was found between the different clinical manifestations of dental fluorosis (DF) with nine polymorphisms of genes responsible for enamel development, craniofacial development, hormonal transcription/reception, and oxidative stress. Hypoplasia was associated with polymorphisms located in intronic regions.

CONCLUSION

MIH, HPSM, DF, and hypoplasia reported as having a complex etiology are significantly associated with genetic polymorphisms of several genes.

The crucial role of centrioles in tooth growth and development

BACKGROUND

Tooth development hinged on reciprocal interactions between enamel and dentin, shaping tooth structures. Centrioles influenced cellular direction, critical for stem cell differentiation. Aberrant centrioles contributed to conditions like Huntington's disease and cancers. Centriole-related gene mutations, like Pericentrin and Centrosomal P4.1-associated protein (CPAP), led to tooth abnormalities, microcephaly. Our study explored the role of centrioles in ameloblasts during molar growth, shedding light on tooth development mechanisms.

METHODS

Tissue sections underwent immunofluorescence and hematoxylin and eosin staining to observe centriole changes in C57BL/6 mouse molars (1,3,5,7, and 9 days). Emphasis was placed on comparing centrioles in enamel and ameloblasts between Nestin-Cremediated Cpap conditional knockout in p53-deficient mice (Cpap(-/-) mice) and normal mice on the ninth day.

RESULTS

In mouse molar tissue, ameloblasts and enamel underwent notable changes during the 1-9 days after birth. Centrioles in ameloblasts exhibited dynamic temporal localization, migrating away from cell nuclei towards enamel generation. Correlation between enamel thickness and centriole quantity suggested a relationship. Comparative analysis of normal and Cpap (-/-) mice on the ninth day revealed differences in enamel thickness, ameloblast elongation, and centriole distribution, highlighting the impact of CPAP deficiency on tooth development.

CONCLUSION

This study affirmed the positive contribution of ciliated centrioles in ameloblasts to enamel growth during the secretory phase. Increased centrioles correlated with enhanced enamel formation. Conversely, CPAP loss disrupted centriole organization, impacting ameloblast morphology and functionality, resembling enamel hypoplasia observed in microcephaly patients. Further research is essential to unravel molecular mechanisms and potential interactions with odontoblast centrioles.

The Evolutionary Young Actin Nucleator Cobl Is Important for Proper Amelogenesis

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.

Effect of prenatal alcohol consumption on dental enamel formation in offspring-An animal study protocol

BACKGROUND

The etiology of developmental defects of enamel (DDE) remains incompletely understood. Prenatal alcohol exposure has been proposed as a potential risk factor for DDE. Animal studies suggest that in utero ethanol exposure can disrupt ameloblast function, leading to enamel abnormalities. This study aims to: (1) Assess the impact of prenatal alcohol consumption on the clinical and structural properties of dental enamel in offspring; and (2) Investigate the underlying mechanisms of these alterations through histological and molecular analyses. Pregnant Wistar rats will be assigned to two groups: one exposed to ethanol and a control group with no alcohol exposure. Ethanol exposure will follow a binge drinking model, with rats receiving 3 g/kg of ethanol (30% w/v) for 3 consecutive days, followed by 4 days of rest each week. This regimen will begin one week prior to conception and continue throughout pregnancy. The incisors and molars of offspring will be evaluated on the 10th (n = 22 per group) and 28th (n = 22 per group) days of life. Visible enamel changes will be documented through photographs. Enamel volume, thickness, and density will be assessed using micro-CT imaging. Mechanical properties will be evaluated using the Knoop microhardness test, while chemical composition will be analyzed through Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX) and Raman spectroscopy, respectively. The area of the organic enamel matrix will be quantified in histological sections. Genes Amelx, Enam, Ambn, Mmp2, Mmp9, Mmp20, Klk4, Cldn3, Cldn16, and Cldn19 will be evaluated in ameloblasts using real-time RT-PCR and protein synthesis will be confirmed by immunohistochemistry. Gelatinolytic activity in the ameloblast layer will be assessed by in situ zymography.

A prevalent Krt8-to-Krt5 cellular state transition in skin is co-opted by p63 for enamel organ development

Tooth enamel, the hardest tissue in vertebrates, is crucial for mastication and dental protection. Its formation depends on the enamel organ (EO), a specialized epithelial structure derived from oral epithelium. A fundamental question persists: how does uniform oral epithelium differentiate into diverse EO cell types? While p63, a master regulator of ectodermal development, coordinates multiple signaling pathways essential for dental placode formation, its specific roles in EO development remain unclear due to the early developmental arrest in p63 knockout mice. Using single-cell RNA sequencing data from mouse incisors, we demonstrate that p63 is expressed across all EO cell types, serving both shared and distinct functions. Through trajectory reconstruction, we identify the role of p63 in regulating both amelogenic (AmG) and non-AmG lineage commitment during EO development. Our comparative transcriptome analyses reveal that p63 regulates the Krt8-to-Krt5 transition during AmG cell differentiation, paralleling its function in skin development. This parallel is reinforced by comparative motif discovery, revealing shared transcription factor usage, particularly p63 and AP-2 family members, in both AmG and skin epidermal cells during this transition. Chromatin accessibility analysis further illustrate that p63 mediates this transition through chromatin landscape remodeling. Together, these findings demonstrate that p63 co-opts the Krt8-to-Krt5 transition mechanism from skin development for EO development, providing novel insights into the molecular mechanisms underlying EO development and potential therapeutic targets for enamel disorders.

Evaluation of Silica and Bioglass Nanomaterials in Pulp-like Living Materials

Although silicon is a widespread constituent in dental materials, its possible influence on the formation and repair of teeth remains largely unexplored. Here, we studied the effect of two silicic acid-releasing nanomaterials, silica and bioglass, on a living model of pulp consisting of dental pulp stem cells seeded in dense type I collagen hydrogels. Silica nanoparticles and released silicic acid had little effect on cell viability and mineralization efficiency but impacted metabolic activity, delayed matrix remodeling, and led to heterogeneous cell distribution. Bioglass improved cell metabolic activity and led to a homogeneous dispersion of cells and mineral deposits within the hydrogel. These results suggest that the presence of calcium ions in bioglass is not only favorable to cell proliferation but can also counterbalance the negative effects of silicon. Both chemical and biological processes should therefore be considered when investigating the effects of silicon-containing materials on dental tissues.

Clinical and Technological Evaluation of the Remineralising Effect of Biomimetic Hydroxyapatite in a Population Aged 6 to 18 Years: A Randomized Clinical Trial

The aim of this randomized clinical trial was to evaluate the efficacy of two different remineralising toothpastes in preventing dental caries and promoting oral health. Patients aged 6-18 years old with healthy and fully erupted first permanent molars (C1 and C2 DIAGNOdent scores) were enrolled and randomized into two groups according to the home-hydroxyapatite-based remineralising treatment used: the Trial group used zinc carbonate hydroxyapatite-based treatment (Biorepair Total Protective Repair), while the Control group used magnesium strontium carbonate hydroxyapatite conjugated with chitosan toothpaste (Curasept Biosmalto Caries Abrasion & Erosion). Dental and periodontal parameters were measured over a six-month period, including the DIAGNOdent Pen Index (primary outcome), BEWE Index, Plaque Index, Bleeding Score, Schiff Air Index, and ICDAS assessed with DIAGNOcam. A total of 40 patients were equally allocated in the two groups and finally analyzed. A significant reduction in the DIAGNOdent Pen score was reported in the Trial group after 1 month of treatment, while in the Control group, no significant change was found. The Trial group also showed a significant reduction in plaque levels after 3 months of treatment, while in the Control group, it occurred after 1 month. However, the Bleeding Score and Schiff Air Index showed no significant differences between the groups, suggesting that additional measures may be required to address gingival inflammation and hypersensitivity. The ICDAS index also showed no statistically significant changes, due to the limited duration of this study. Overall, zinc-hydroxyapatite-based toothpaste was more effective than magnesium strontium carbonate hydroxyapatite toothpaste in enhancing enamel remineralisation in the short-term period. The assigned treatments did not result in significant improvements in the oral indexes assessed in this study.

Roles of calcium in ameloblasts during tooth development: A scoping review

Objectives

Calcium ions (Ca2+) play crucial role in tooth development, particularly in maintaining enamel density during amelogenesis. Ameloblasts require specific proteins such as amelogenin, ameloblastin, enamelin, kallikrein, and collagen for enamel growth. Recent research has highlighted the importance of calcium and fluoride ions, as well as the TRPM7, STIM, and SOCE pathways, in regulating various stages of enamel formation. This review synthesizes current knowledge, focusing on preclinical data elucidating the molecular mechanisms of calcium transport in ameloblasts, during normal tooth development and in response to external stimuli.

Methods

This scoping review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The literature search, conducted in December 2023, spanned multiple databases including PubMed (8.363 records), Google Scholar (5.630 records), and Science Direct (21.810 records). The primary aim was to examine the influence of calcium ion regulation on ameloblast development, with a focus on preclinical studies.

Results

After an initial screening of 396 titles and abstracts, 11 full-text articles (four in vitro studies and seven animal studies) met the inclusion and exclusion criteria. The studies, assessed for quality using the CAMRADES tool, ranged from low to moderate. Calcium deficiency, nutritional supplements, fluoride exposure, TRPM7, STIM proteins, and the SOCE pathway were found to influence amelogenesis.

Conclusion

Calcium transport mechanisms play a critical role in enamel formation, with factors such as TRPM7, Kir 4.2, CRAC channels, and the SOCE pathway supporting enamel mineralization, while disruptions like hypoxia, fluoride exposure, and circadian imbalances negatively impact amelogenesis. Understanding the interplay between calcium, environmental, and nutritional factors provides valuable insights into ameloblast function and offers potential avenues for improving enamel quality and addressing defects.

Promising potential effects of resveratrol on oral and dental health maintenance: a comprehensive review

Resveratrol (RV-3, 5, 4'-trihydroxystilbene) is a natural compound found in plants like red grapes, berries, and peanuts, with promising effects on dental health. It helps strengthen tooth enamel by promoting remineralization, making the teeth more resistant to decay caused by acid-producing bacteria. RV also shields dentin, a vulnerable layer beneath the enamel, from erosion and sensitivity. Its anti-inflammatory properties can reduce inflammation associated with dental conditions such as pulpitis and endodontic diseases. Moreover, RV's antimicrobial activity inhibits the growth of bacteria involved in dental plaque and biofilm formation, preventing their accumulation on the tooth surface. This contributes to a healthier oral environment and prolongs the lifespan of dental restorative materials. However, the research on RV's impact on dental health is in its early stages, and further studies are needed to confirm potential benefits. Important factors such as determining the optimal dosage, understanding its bioavailability, and assessing potential side effects require further investigation. This review focuses on the important role of RV in promoting dental health. It delves into various aspects, including its impact on root health, maintenance of the dental pulp, care for tooth enamel, effectiveness of dental restorative materials, and health of dentin.

Evaluation of Broccoli Extract for Enhancing Primary Tooth Enamel Microhardness: An In Vitro Study

Background and Aims

Dental caries remains highly prevalent among children. This study aimed to evaluate the efficacy of aqueous broccoli extract in enhancing the microhardness of demineralized primary tooth enamel compared to a standard fluoride treatment.

Methods

An in vitro study was conducted using 30 extracted primary second molars, which were sectioned and polished. Baseline enamel microhardness was assessed using a Vickers hardness tester. Demineralization was induced using a cola drink (pH 4.5) for 8 min. The broccoli extract was prepared by air-drying fresh florets, stems, and leaves at room temperature, followed by aqueous extraction with distilled water and filtration. The samples were randomly assigned to receive a 10-min treatment with either aqueous broccoli extract (Group B) or 1.23% acidulated phosphate fluoride (APF) gel (Group F). Microhardness was measured posttreatment, and percentage changes between time points were compared using statistical analysis.

Results

After demineralization, broccoli extract, and fluoride gel significantly improved enamel microhardness. The broccoli extract group exhibited a greater recovery in microhardness (+44.95% vs. +20.78%, p = 0.008) compared to the fluoride gel group. However, the overall reduction in microhardness from baseline to final measurement showed no statistically significant difference between the two groups (p = 0.077).

Conclusion

Aqueous broccoli extract demonstrated comparable overall efficacy to fluoride gel in enhancing demineralized primary tooth enamel microhardness despite showing different patterns of demineralization and recovery. These findings suggest that broccoli extract may be a natural and effective alternative for enhancing enamel remineralization in pediatric caries prevention, warranting further clinical investigation.

Dentists' Knowledge, Attitudes, and Practices Regarding Molar Incisor Hypomineralization (MIH): A French Survey

INTRODUCTION

With an estimated 878 million cases worldwide in 2015, molar incisor hypomineralization (MIH) is a growing issue. Early detection and management require knowledge and application of good clinical practices. The aim of the study was to evaluate the knowledge, attitudes, and practices of French dentists regarding MIH.

METHOD

A self-administered questionnaire was distributed to different groups of practitioners between 30 January and 27 March 2023, including members of the French dental practice-based research network, members of the social network "French pediatric dentists," and members of the professional social network LinkedIn (LinkedIn, Sunnyvale, California, United States). The data from 311 questionnaires were analyzed.

RESULTS

Around 277 (89%) practitioners were familiar with MIH, 180 (58%) were perfectly aware of the clinical features of MIH, and 193 (62%) reported being able to clinically identify MIH. Nearly 100% (310) of dentists cited "environmental pollutants" as the most frequent etiological factor. Glass ionomer is the most used restorative material.

CONCLUSION

Education regarding MIH must be improved among dentists to correctly detect, treat, or refer patients. It would seem useful to carry out an MIH prevalence study in France.

Endocytosis mediated by megalin and cubilin is involved in enamel development

BACKGROUND

Endocytosis of enamel matrix proteins (EMPs) by ameloblasts is a key process in the mineralization of enamel during the maturation stage of amelogenesis. However, the relevant receptor mediating endocytosis of EMPs is still unclear. The aim of this study was to explore potential endocytic receptors involved in this process.

RESULTS

Two endocytic receptors, megalin, and cubilin, were found to be distributed in ameloblasts of mouse incisors and molars during the secretory and maturation stages. Megalin was located at the distal end of ameloblasts during the maturation stage when proteolysis and recycling were the most active. Megalin and cubilin were also expressed in an ameloblast-lineage cell (ALC) line. The immunoelectron microscopy results showed that megalin was positively labeled on the vesicle structures of ALC, where endocytosis happened. Immunofluorescence showed that megalin and cubilin were colocalized with amelogenin, and the absorption of amelogenin was significantly reduced when megalin and cubilin were inhibited by their inhibitor, receptor-associated protein (RAP). Knockdown of megalin and cubilin with siRNA also reduced the ability of ALC to absorb amelogenin.

CONCLUSIONS

The results of this study suggest that megalin and cubilin are involved in the absorption process of ameloblasts during amelogenesis.

Clinically oriented automatic three-dimensional enamel segmentation via deep learning

BACKGROUND

Establishing accurate, reliable, and convenient methods for enamel segmentation and analysis is crucial for effectively planning endodontic, orthodontic, and restorative treatments, as well as exploring the evolutionary patterns of mammals. However, no mature, non-destructive method currently exists in clinical dentistry to quickly, accurately, and comprehensively assess the integrity and thickness of enamel chair-side. This study aims to develop a deep learning work, 2.5D Attention U-Net, trained on small sample datasets, for the automatical, efficient, and accurate segmentation of enamel across all teeth in clinical settings.

METHODS

We propose a fully automated computer-aided enamel segmentation model based on an instance segmentation network, 2.5D Attention U-Net. After data annotation and augmentation, the model is trained using manually annotated segmented enamel data, and its performance is evaluated using the Dice similarity coefficient metrics. A satisfactory image segmentation model is applied to generate a 3D enamel model for each tooth and to calculate the thickness value of individual enclosed 3D enamel meshes using a normal ray-tracing directional method.

RESULTS

The model achieves the Dice score on the enamel segmentation task of 96.6%. This study provides an intuitive visualization of irregular enamel morphology and a quantitative analysis of three-dimensional enamel thickness variations. The results indicate that enamel is thickest at the incisal edges of anterior teeth and the cusps of posterior teeth, thinning towards the roots. For posterior teeth, the enamel is thinnest at the central fossae area, with mandibular molars having thicker enamel in the central fossae compared to maxillary molars. The average enamel thickness of maxillary incisors, canines, and premolars is greater than that of mandibular incisors, while the opposite is true for molars. Although there are individual variations in enamel thickness, the average enamel thickness graduallly increases from the incisors to the molars among all teeth within the same quadrant.

CONCLUSIONS

This study introduces an automatic, efficient, and accurate 2.5D Attention U-Net system to enhance precise and efficient chair-side diagnosis and treatment of enamel-related diseases in clinical settings, marking a significant advancement in automated diagnostics for enamel-related conditions.

Comparative Analysis of Whitening Outcomes of Over-the-Counter Toothpastes: An In Vitro Study

Background/Objectives: Whiter teeth are widely accepted as the most beautiful. With the growing demand for whiter teeth, several manufacturers have launched different brands of whitening toothpaste claiming to be effective in removing tooth stains and whitening teeth. The objective of this in vitro study was to evaluate and compare the whitening effect of eight over-the-counter available toothpastes by measuring the changes in color using a digital colorimeter in a simulated staining-brushing cycle model. Methods: A total of 32 extracted bovine enamel were polished with 1000-2000 grit SIC paper and immersed in a tea staining solution for 30 min at 37 °C to create extrinsic staining. The specimens were randomly divided into eight groups (n = 4) and subjected to a staining-brushing cycle for 2 weeks. During this period, the specimens were stained for 5 min twice, brushed for 2 min twice per day, and immersed in artificial saliva for the remaining time. The colors of the enamel surfaces L*, a*, and b* were recorded, and the color difference (ΔE) was measured before the treatment and after 1 and 2 weeks of the staining-brushing cycle. Results: The repeated measures showed a significant reduction of (ΔE) after 1 week of the staining-brushing cycle in all eight experimental groups (p < 0.05). The (ΔE) was significantly reduced after the second week of the staining-brushing cycle in groups 1, 3, and 5 (p < 0.05). However, it was insignificant in groups 2, 6, 7, and 8 (p > 0.05). Among the tested materials, group 1 showed the highest and group 8 showed the lowest teeth-whitening effects. Conclusions: The over-the-counter toothpaste used in this study showed effective teeth-whitening. Charcoal-based toothpaste showed the highest efficiency in teeth whitening.

Antithrombotic and anticariogenic activity of peptide fractions from cowpea (Vigna unguiculata) protein hydrolysates

BACKGROUND

Protein-derived peptide fractions can play a key role in the physiological and metabolic regulation and modulation of the body, which suggests that they could be used as functional ingredients to improve health and to reduce the risk of disease. This work aimed to evaluate the in vitro antithrombotic and anticariogenic bioactivity of hydrolysates and protein fractions obtained from cowpea (Vigna unguiculata) by biocatalysis.

RESULTS

Cowpea protein concentrate was hydrolyzed by sequential action with two enzyme systems, Pepsin-Pancreatin or Alcalase-Flavourzyme. There was extensive enzymatic hydrolysis, with degrees of hydrolysis of 34.94% and 81.43% for Pepsin-Pancreatin and Alcalase-Flavourzyme, respectively. The degree of hydrolysis for the control treatments, without the addition of the enzymes Pepsin-Pancreatin and Alcalase-Flavourzyme was 1.1% and 1.2%, respectively. The hydrolysates were subjected to fractionation by ultrafiltration, with five cut-off points according to molecular weight (<1, 1-3, 3-5, 5-10 and >10 kDa). The Alcalase-Flavourzyme hydrolysate led to 100% inhibition of platelet aggregation, while the Pepsin-Pancreatin hydrolysate showed 77.41% inhibition, but this was approximately 100% in the ultrafiltered fractions. The highest anticariogenic activity was obtained with the Pepsin-Pancreatin system, with 61.55% and 56.07% for calcium and phosphorus demineralization, respectively.

CONCLUSION

Hydrolysates and their peptide fractions from Vigna unguiculata exhibited inhibition of platelet aggregation and protection of tooth enamel and have the potential for use in the development of functional products with beneficial health effects. © 2024 Society of Chemical Industry.

Unlocking Osseointegration: Surface Engineering Strategies for Enhanced Dental Implant Integration

Tooth loss is a prevalent problem faced by individuals of all ages across the globe. Various biomaterials, such as metals, bioceramics, polymers, composites of ceramics and polymers, etc., have been used for the manufacturing of dental implants. The success of a dental implant primarily depends on its osseointegration rate. The current surface modification techniques fail to imbibe the basics of tooth development, which can impart better mineralization and osseointegration. This can be improved by developing an understanding of the developmental pathways of dental tissue. Stimulating the correct signaling pathways through inductive material systems can bring about a paradigm shift in dental implant materials. The current review focuses on the developmental pathway and mineralization process that happen during tooth formation and how surface modifications can help in biomimetic mineralization, thereby enhancing osseointegration. We further describe the effect of dental implant surface modifications on mineralization, osteoinduction, and osseointegration; both in vitro and in vivo. The review will help us to understand the natural process of teeth development and mineralization and how the surface properties of dental implants can be further improved to mimic teeth development, in turn increasing osseointegration.

Age estimation using the ratio of dental pulp to tooth volume by CT scan in dogs

IMPORTANCE

Accurate age estimations in dogs are essential for various veterinary and clinical applications. Traditional methods based on dental appearance are error-prone because of external influences, necessitating the development of more precise methodologies.

OBJECTIVE

This study examined the association between chronological age and pulp to tooth (P/T) volume ratio in dogs using computed tomography (CT) of the right maxillary canine and right maxillary fourth premolar (PM4) teeth.

METHODS

Ninety-five canine skulls, aged five to 216 months, were examined using a two-slice CT scan machine. Volumetric analyses of the right maxillary canine and PM4 were performed. Statistical analysis, including Spearman's correlation and regression analysis, was conducted to assess the relationship between age and the P/T volume ratio.

RESULTS

This study included 60 male and 35 female dogs, with no significant age difference between genders (p = 0.655). A strong negative correlation was observed between age and the P/T volume ratio for the right maxillary canine (r = 0.88, p < 0.001) and PM4 (r = 0.77, p < 0.001) teeth. Logarithmic regression models provided a better fit for age prediction (R² = 0.78 for the right maxillary canine, R² = 0.67 for PM4) compared to linear models.

CONCLUSIONS AND RELEVANCE

CT-based volumetric analysis of the P/T ratio in the right maxillary canine and PM4 teeth offers a precise, non-invasive method for estimating the age of dogs. This technique can improve the accuracy of age estimations, particularly in forensic and clinical settings, providing valuable insights for veterinarians and researchers.

IP3 receptor depletion in a spontaneous canine model of Charcot-Marie-Tooth disease 1J with amelogenesis imperfecta

Inositol 1,4,5-trisphosphate receptors (IP3R) mediate Ca2+ release from intracellular stores, contributing to complex regulation of numerous physiological responses. The involvement of the three IP3R genes (ITPR1, ITPR2 and ITPR3) in inherited human diseases has started to shed light on the essential roles of each receptor in different human tissues and cell types. Variants in the ITPR3 gene, which encodes IP3R3, have recently been found to cause demyelinating sensorimotor Charcot-Marie-Tooth neuropathy type 1J (CMT1J). In addition to peripheral neuropathy, immunodeficiency and tooth abnormalities are occasionally present. Here, we report the identification of a homozygous nonsense variant in the ITPR3 gene in Lancashire Heeler dogs, presenting with a severe developmental enamel defect and reduced nerve conduction velocity. We studied the primary skin fibroblasts of the affected dogs and observed that the nonsense variant in ITPR3 led to a complete absence of full-length IP3R3 protein. Unexpectedly, the protein levels of IP3R1 and IP3R2 were also markedly decreased, suggesting co-regulation. Functional Ca2+ measurements revealed reduced IP3R-mediated Ca2+ flux upon stimulation of G-protein-coupled-receptors in the affected dog fibroblasts. These findings highlight the first spontaneous mammalian phenotype caused by a nonsense variant in ITPR3, leading to the loss of IP3R3. The human and canine IP3R3 proteins are highly similar, and our study suggests that the tissue involvement resulting from the receptor's dysfunction is also conserved. In summary, IP3R3 is critical for enamel formation and peripheral nerve maintenance.

Comprehensive characterization of tobacco-induced changes in enamel surface topography

Introduction

Enamel translucency, essential for the aesthetic appeal of teeth, is primarily determined by its thickness, quality, and refractive index. Several factors, including age, genetics, diet, oral hygiene practices, fluoride exposure, and acidic challenges, can influence enamel translucency. Tobacco use, in particular, leads to significant alterations in enamel appearance by penetrating its micropores, causing yellowing and browning. Prolonged exposure to tobacco results in demineralization, increasing enamel porosity and reducing its translucency. Over time, this exposure leads to permanent discoloration and structural degradation, rendering teeth dull and opaque. To assess these changes, various methods such as visual examinations, digital photography, spectrophotometry, stylus profilometry, and atomic force microscopy (AFM) are utilized.

Materials and methods

This study analyzed human enamel samples, including one unstained sample (Grade 0) and three tobacco-stained samples (Grades 1-3) according to Modified Lobene Stain Index (MLSI), to investigate the impact of tobacco exposure on enamel structure. The samples were thoroughly cleaned and dried to ensure accurate results. High-resolution AFM imaging was employed to assess surface roughness, porosity, and microstructural changes induced by tobacco staining. A stylus profilometer was used to trace the surface topography, providing detailed measurements of surface irregularities. Additionally, a spectrophotometer was utilized to evaluate the optical properties of the enamel, focusing on changes in translucency and light absorption due to tobacco exposure.

Results

AFM analysis revealed a clear progression of enamel surface roughness from Grade 0 to Grade 3. The Sa and Sq values increased significantly with the severity of tobacco staining, indicating greater surface degradation. The stylus profilometer data corroborated these findings, with rising Ra values as the degree of staining intensified, highlighting the topographical alterations caused by tobacco exposure. Spectrophotometric analysis further demonstrated a decrease in enamel reflectance and an increase in light absorption from mild to severe staining, underscoring the detrimental optical effects of tobacco on enamel.

Conclusion

The combined use of AFM, stylus profilometry, and spectrophotometry provided a comprehensive assessment of the impact of tobacco staining on enamel translucency and surface roughness. The findings show that as staining severity increases, enamel translucency diminishes, and surface roughness worsens. These alterations not only affect the aesthetic appearance of teeth but also have potential implications for enamel functionality and long-term oral health.

A Chemically Defined Culture for Tooth Reconstitution

It is known for decades that dental epithelium and mesenchyme can reconstitute and regenerate a functional tooth. However, the mechanism of tooth reconstitution remains largely unknown due to the lack of an efficient in vitro model. Here, a chemically defined culture system is established that supports tooth reconstitution, further development with normal anatomy, and prompt response to chemical interference in key developmental signaling pathways, termed as toothoids. By using such a system, it is discovered that, during reconstitution, instead of resetting the developmental clock, dental cells reorganized and restarted from the respective developmental stage where they are originally isolated. Moreover, co-stimulation of Activin A and Hedgehog/Smoothened agonist (SAG) sustained the initial induction of tooth fate from the first branchial arch, which would be otherwise quickly lost in culture. Furthermore, activation of Bone Morphogenetic Protein (BMP) signaling triggered efficient enamel formation in the late-stage toothoids, without affecting the normal development of ameloblasts. Together, these data highlight the toothoid culture as a powerful tool to dissect the molecular mechanisms of tooth reconstitution and regeneration.

KMT2D regulates tooth enamel development

Amelogenesis, the process of enamel formation, is tightly regulated and essential for producing the tooth enamel that protects teeth from decay and wear. Disruptions in amelogenesis can result in amelogenesis imperfecta, a group of genetic conditions characterized by defective enamel, including enamel hypoplasia, marked by thin or underdeveloped enamel. Mutations in the KMT2D (MLL4) gene, which encodes a histone H3-lysine 4-methyltransferase, are associated with Kabuki syndrome, a developmental disorder that can involve dental anomalies such as enamel hypoplasia. However, the specific role of KMT2D in amelogenesis remains poorly understood. To address this gap, we generated a conditional knockout mouse model with ectoderm-specific deletion of Kmt2d (Krt14-Cre;Kmt2d fl/fl , or Kmt2d-cKO) and characterized the resulting enamel defects using gross, radiographic, histological, cellular, and molecular analyses. Micro-computed tomography and scanning electron microscopy revealed that adult Kmt2d-cKO mice exhibited 100% penetrant amelogenesis imperfecta, characterized by hypoplastic and hypomineralized enamel, partially phenocopying human Kabuki syndrome. Additionally, Kmt2d-cKO neonates developed molar tooth germs with subtle cusp shape alterations and mild delays in ameloblast differentiation at birth. RNA-seq analysis of the first molar tooth germ at birth revealed that 33.7% of known amelogenesis-related genes were significantly downregulated in the Kmt2d-cKO teeth. Integration with KMT2D CUT&RUN-seq results identified 8 overlapping genes directly targeted by KMT2D. Re-analysis of a single-cell RNA-seq dataset in the developing mouse incisors revealed distinct roles for these genes in KMT2D-regulated differentiation across various cell subtypes within the dental epithelium. Among these genes, Satb1 and Sp6 are likely direct targets involved in the differentiation of pre-ameloblasts into ameloblasts. Taken together, we propose that KMT2D plays a crucial role in amelogenesis by directly activating key genes involved in ameloblast differentiation, offering insights into the molecular basis of enamel development and related dental pathologies.

Study protocol on the impact of postnatal maternal separation stress on dental enamel formation in a murine experimental model

Dental development is a complex process influenced by genetic and environmental factors. Dental enamel, primarily composed of hydroxyapatite, is formed through complex cellular and biochemical mechanisms. Although this is a stable process, genetic, nutritional, and environmental factores can lead to developmental defects such as hypomineralization and hypoplasia. Molar incisor hypomineralization is a type of hypomineralization that represents a public health challenge. Its etiology is not yet fully understood, but factors such as hypoxia, medication exposure, adverse events in early childhood, and genetic influences are considered. This study protocol aims to investigate whether postnatal adverse events can impact amelogenesis, exploring the role of stress in the etiology of dental enamel defects. Specific objectives include evaluating enamel structure and mechanical properties by comparing the offspring of rats exposed to postnatal maternal separation with control animals (non-exposed). Additionally, we will evaluate weight, length, survival assessment, and developmental milestones between the groups. Macrophotographic analysis, microtomography, microhardness testing, and electron microscopy will enable a detailed assessment of enamel morphology and its mechanical properties. Histological and molecular analyses-such as immunohistochemistry, indirect immunofluorescence, and in situ zymography-will be performed to evaluate possible changes in proteins and enzymes that are essential for proper enamel biomineralization.

Assessment of Change in Enamel Color and Surface Hardness Following the Use of ICON Resin Infiltration and Remineralizing Agent: An In Vitro Study

This study aimed to evaluate the change in enamel color and surface micro-hardness following the use of resin-infiltration concept material (ICON) and casein phosphopeptide-amorphous calcium fluoride phosphate (CPP-ACFP) remineralizing agent. Fifty-four extracted human third molars were collected and randomly divided into three groups: group A: control with no surface treatment; group B: treated using ICON; and group C: treated using CPP-ACFP. The change in color and micro-hardness of the enamel surface were measured using spectrophotometer and Vickers hardness number, respectively. The measurements were taken at three timelines; baseline (BL), after demineralization (DM), and after surface treatment (TX). The three groups showed no significant differences in enamel color change after demineralization (p < 0.05). However, after surface treatment in relation to the baseline, groups B and C had a significant increase in color change compared to the control group (p < 0.05), and group B showed a statistically significant increase in enamel color changes compared to group C. Additionally, all groups exhibited a significant reduction in enamel micro-hardness after demineralization in comparison to their baseline (p < 0.05). Group C showed a significant increase in micro-hardness after surface treatment compared to groups A and B (p < 0.05), while group B showed a significant decrease in enamel micro-hardness compared to groups A and C (p < 0.05). These findings suggest that teeth treated with CPP-amorphous calcium fluoride phosphate (CPP-ACFP) show a significant improvement in enamel surface color after demineralization compared to the teeth treated with resin infiltration (ICON) and the non-treated teeth. Additionally, enamel surfaces treated with CPP-ACFP show significant enamel hardness regaining, while resin infiltration (ICON) compromises enamel surface hardness.

The intricacies of tooth enamel: Embryonic origin, development and human genetics

Tooth enamel is a fascinating tissue with exceptional biomechanical properties that allow it to last for a lifetime. In this mini review, we discuss the unique embryonic origin of this highly mineralized tissue, the complex differentiation process that leads to its "construction" (amelogenesis), and the various genetic conditions that lead to impaired enamel development in humans (amelogenesis imperfecta). Tremendous progress was made in the last 30 years in understanding the molecular and cellular mechanism that leads to normal and pathologic enamel development. However, several aspects of amelogenesis remain to be elucidated and the function of many genes associated with amelogenesis imperfecta still needs to be decoded.

SAXS of murine amelogenin identifies a persistent dimeric species from pH 5.0 to 8.0

Amelogenin is an intrinsically disordered protein essential to tooth enamel formation in mammals. Using advanced small angle X-ray scattering (SAXS) capabilities at synchrotrons and computational models, we revisited measuring the quaternary structure of murine amelogenin as a function of pH and phosphorylation at serine-16. The SAXS data shows that at the pH extremes, amelogenin exists as an extended monomer at pH 3.0 (Rg = 38.4 Å) and nanospheres at pH 8.0 (Rg = 84.0 Å), consistent with multiple previous observations. At pH 5.0 and above there was no evidence for a significant population of monomeric species. Instead, at pH 5.0, ∼80 % of the population is a heterogenous dimeric species that increases to ∼100 % at pH 5.5. The dimer population was observed at all pH > 5 conditions in dynamic equilibrium with a species in the pentamer range at pH < 6.5 and nanospheres at pH 8.0. At pH 8.0, ∼40 % of the amelogenin remained in the dimeric state. In general, serine-16 phosphorylation of amelogenin appears to modestly stabilize the population of the dimeric species.

Deletion within ameloblastin multitargeting domain reduces its interaction with artificial cell membrane

In human, mutations in the gene encoding the enamel matrix protein ameloblastin (Ambn) have been identified in cases of amelogenesis imperfecta. In mouse models, perturbations in the Ambn gene have caused loss of enamel and dramatic disruptions in enamel-making ameloblast cell function. Critical roles for Ambn in ameloblast cell signaling and polarization as well as adhesion to the nascent enamel matrix have been supported. Recently, we have identified a multitargeting domain (MTD) in Ambn that interacts with cell membrane, with the majority enamel matrix protein amelogenin, and with itself. This domain includes an amphipathic helix (AH) motif that directly interacts with cell membrane. In this study, we analyzed the sequence of the MTD for evolutionary conservation and found high conservation among mammals within the MTD and particularly within the AH motif. We computationally predicted that the AH motif lost its hydrophobic moment upon deleting hydrophobic but not hydrophilic residues from the motif. Furthermore, we rationally designed peptides that encompassed the Ambn MTD and contained deletions of largely hydrophobic or hydrophilic stretches of residues. To assess their AH-forming and membrane-binding abilities, we combined those peptides with synthetic phospholipid membrane vesicles and performed circular dichroism, membrane leakage, and vesicle clearance measurements. Circular dichroism showed retention of α-helix formation in all peptides except the one with the largest deletion of eleven amino acids including seven that were hydrophobic. This same peptide variant failed to cause leakage or clearance of synthetic membranes, while smaller deletions yielded intermediate membrane interaction as measured by leakage and clearance assays. Our data revealed that deletion of key hydrophobic residues from the AH leads to the most dramatic loss of Ambn-membrane interaction. Pinpointing roles of residues within the MTD has important implications for the multifunctionality of Ambn.

KDF1 promotes ameloblast differentiation by inhibiting the IKK/IκB/NF-κB axis

Enamel protects teeth from external irritation and its formation involves sequential differentiation of ameloblasts, a dental epithelial cell. Keratinocyte differentiation factor 1 (KDF1) is important in the development of epithelial tissues and organs. However, the specific role of KDF1 in enamel formation and corresponding regulatory mechanisms are unclear. This study demonstrated that KDF1 was persistently expressed in all stages of ameloblast differentiation, through RNAscope in situ hybridization. KDF1 expression in the mouse ameloblast cell line LS8 was demonstrated via immunofluorescence assay. KDF1 was knocked out in LS8 cells using the CRISPR/Cas-9 system or overexpressed in LS8 cells through lentiviral infection. In vitro ameloblast differentiation induction, quantitative reverse transcription PCR, western blot analysis, and alkaline phosphatase (ALP) assay indicated that knockout or overexpression of KDF1 in LS8 cells decreased or increased the mRNA and protein levels of several key amelogenesis markers, as well as ALP activity. Furthermore, liquid chromatography-mass spectrometry and co-immunoprecipitation analyses revealed that KDF1 can interact with the IKK complex, thereby inhibiting the NF-κB pathway. Suppressing NF-κB activity partially recovered the decreased ameloblast differentiation in LS8 cells induced by KDF1-knockout. This study demonstrated that KDF1 can promote ameloblast differentiation of LS8 cells by inhibiting the IKK/IκB/NF-κB axis, and is a potential target for functional enamel regeneration.

Remineralising enamel caries with a novel peptide: An in vitro study

OBJECTIVE

To evaluate the antibacterial and remineralising effects of GAPI peptide on artificial enamel caries.

METHODS

Human enamel blocks were exposed to Streptococcus mutans biofilm to create artificial carious lesions. The blocks were randomly assigned to either the GAPI treatment group or the deionised water control group, treated twice daily for 21 days. The viability, growth kinetics, and morphology of S. mutans biofilms were assessed using confocal laser scanning microscopy (CLSM), colony-forming unit (CFU) counting, and scanning electron microscopy (SEM). Lesion depth, mineral loss, calcium-to-phosphorus ratio, Knoop hardness, enamel surface morphology, and crystal characteristics of enamel lesions were determined using micro-computed tomography (Micro-CT), SEM-energy dispersive spectroscopy (EDS), a microhardness tester, SEM, and X-ray diffraction (XRD).

RESULTS

CLSM showed that the dead-to-live ratio of S. mutans was 0.8 ± 0.1 in the GAPI group and 0.4 ± 0.1 in the control group (p < 0.001). The Log CFUs were 6.9 ± 0.7 in the GAPI group and 8.1 ± 0.5 in the control group (p = 0.002). SEM revealed confluent growth of S. mutans in the control group but not in the GAPI group, which also exhibited cell damage. Micro-CT showed that the lesion depth (µm) was 142 ± 11 in the GAPI group and 178 ± 20 in the control group (p < 0.001), with mineral loss (gcm⁻³) of 1.1 ± 0.1 and 1.5 ± 0.1, respectively (p < 0.001). SEM-EDS indicated that the calcium-to-phosphorus ratio was 1.71 ± 0.02 in the GAPI group and 1.67 ± 0.03 in the control group (p = 0.006). Additionally, Knoop hardness was 302 ± 22 in the GAPI group and 242 ± 17 in the control group (p < 0.001). SEM revealed an orderly pattern of enamel rods in the GAPI group, and XRD showed better crystallisation of hydroxyapatite in the GAPI group compared to the control group.

CONCLUSION

GAPI exhibits antibacterial and remineralising properties against artificial enamel caries.

CLINICAL SIGNIFICANCE

If the anti-caries properties of GAPI are confirmed in clinical studies, it could be used for caries prevention.

Evaluation of the Effectiveness of Different Types of Professional Tooth Whitening: A Systematic Review

BACKGROUND/OBJECTIVES

Tooth whitening is a cosmetic dental treatment that improves the color of natural teeth, making them whiter and brighter; this review aimed to evaluate the greater effectiveness of in-office, at-home, and combined bleaching with hydrogen or carbamide peroxide, also in relation to possible relapses and side effects (tooth sensitivity).

METHODS

A literature search has been carried out through electronic databases, PubMed/MEDLINE, and Cochrane Library, focused on the use of the effectiveness of in-office, at-home, and combined dental bleaching. This review has been registered on PROSPERO (ID613248).

RESULTS

30 articles have been included. Most of the studies did not find any more effective treatment than the proposed treatments; all types of bleaching have been shown to be effective in changing color; in the studies that have compared in-office and at-home bleaching, there was a lower recurrence of treatment with the use of the at-home trays with carbamide peroxide gel. There were no clear positions regarding tooth sensitivity, which would appear to be higher in professional in-office and combined dental bleaching.

CONCLUSIONS

Bleaching is an effective treatment for the change of color of the tooth regardless of the type used (concentrations, type of gel, and duration of sessions), although, at home, it would seem to be more effective over time. It is, however, a clinical feature that may give a risk of tooth sensitivity after treatment.

Nanoscale Study on Noninvasive Prevention of Dental Erosion of Enamel by Silver Diamine Fluoride

Here, we aimed to demonstrate the efficacy of silver diamine fluoride (SDF) in halting dental erosion caused by dietary selection and offer a potential explanation for the underlying mechanism. We investigated the surface chemical and mechanical characteristics of human tooth enamel when exposed to Coca-Cola from 10 s to 1 h, with and without the topical treatment of SDF. We analyzed the mechanical properties by measuring the enamel surface roughness and elastic modulus using atomic force microscopy and the surface chemical composition through x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses, with scanning electron microscopy as a supplementary characterization method. After 1 h of immersion in Coca-Cola, the roughness changed from 83 to 287 nm for enamel without SDF treatment and 64 to 70 nm for enamel with SDF treatment. Under the same conditions, the elastic modulus changed from 125 GPa to 13 GPa for enamel without SDF treatment and 215 GPa to 205 GPa for enamel with SDF treatment. Topical coating of SDF onto enamel formed a passivation layer composed of fluorapatite and created added fluorine flux in the system, which protected the teeth from demineralization under Coca-Cola etching, as shown by morphology and chemical composition analysis as well as roughness and modulus characterization. Applying SDF to enamel minimizes changes in chemical compositions and surface roughness while improving enamel elastic modulus.

The sensory nerve regulates stem cell homeostasis through Wnt5a signaling

Increasing evidence indicates that nerves play a significant role in regulating stem cell homeostasis and developmental processes. To explore the impact of nerves on epithelial stem cell homeostasis during tooth development, the regulation of sensory nerves on stem cell homeostasis was investigated using a rat model of incisor development. Impaired mineralization, decreased enamel thickness, and fractured enamel rods of the incisor were observed after denervation. qPCR and histological staining revealed that the expression of enamel-related factors ameloblastin (AMBN), kallikrein-4, amelogenin (Amelx), collagen type XVII (col17a), and enamelin were decreased in the incisor enamel of rats with sensory nerve injure. The decreased expression of Wnt5a in ameloblasts was coupled with the downregulation of calcium ion-related calmodulin kinase II. These results implicate that the sensory nerves are essential in stem cell homeostasis for enamel mineralization and development.

Bioactive Self-Polymerizing Resin with Surface Pre-Reacted Glass Ionomer Fillers for Suppressed Enamel Demineralization

The treatment of damaged enamel surfaces involves modification of the enamel surface with artificial materials or the development of a pseudo-enamel, with research focusing on bioactive and biomimetic materials. In this study, a bioactive auto-polymerizing resin (APR) was developed by adding surface-pre-reacted glass ionomer (S-PRG) fillers of different quantities to APR. Its bioactive effects were evaluated via pH neutralization, ion release, and inhibition of enamel demineralization studies. The pH and fluoride ion release were measured using ion-specific electrodes, revealing that the APR disk with the S-PRG filler immediately neutralized the lactic acid solution (pH 4.0) through ion release. Inductively coupled plasma atomic emission spectrometry revealed that the Sr ion release peaked on the first day, with the other ions following the order F > B > Si > Al > Na, exhibiting a weekly decrease in the same order. Scanning electron microscopy was used to examine the enamel block morphology of the disks after 7 d of incubation, revealing enamel demineralization in disks without the S-PRG filler, whereas no demineralization occurred in disks with the S-PRG filler. APR containing the S-PRG filler demonstrated acid buffering suppressed enamel demineralization and bioactive properties.

3D X-ray microscope acts as an accurate and effective equipment of pathological diagnosis in craniofacial imaging

Craniofacial structure and dental hard tissue used to be researched on by traditional imaging tools such as light microscope, electron microscope and micro-CT. Due to the limitations of imaging principle, resolution and 3D rendering reconstruction technique, traditional imaging tools are constrained for presenting fine structure and precise measurements. Here a brand-new imaging equipment-3D X-ray microscope is introduced to realize a more efficient scanning by demonstrating the comparison of the craniofacial structures and dental hard tissue of diabetes and normal DBA mouse. To explore a higher resolution, more efficient imaging measurement and 3D reconstruction method on craniofacial structure and dental hard tissue. The study included 12 DBA mice which were divided into two groups (control group and diabetes group). The heads were separated and scanned by 3D X-ray microscope, after which regions of interest were selected, followed by measurement and 3D reconstruction based on microscope attached software Dragonfly pro©. Hemi-mandibles were collected for enamel mineral density assessment supported by QRM-MicroCT-HA phantom. Data was submitted to paired t-tests at a 95% confidence level. The automatic assessed enamel thickness of diabetes mice decreased on average, whereas the rest of manual measurements and automatic assessed density showed no statistical difference. We constructed HA phantom assisted enamel density procedure in Dragonfly software. Craniofacial structure and dental hard tissue were well-presented both in 2D slide and 3D reconstruction viewport by 3D X-ray microscope which can be routinely used as craniofacial structure and dental hard tissue imaging tool.

Prevalence of hypomineralized second primary molars and association with socioeconomic characteristics and dental caries in a Brazilian population of preschoolers: a cross-sectional study

OBJECTIVE

To analyze the prevalence of hypomineralized second primary molar (HSPM) and its association with socioeconomic characteristics and dental caries in a Brazilian population of preschoolers.

MATERIAL AND METHODS

603 preschoolers, enrolled in public preschools in Itajaí (state of Santa Catarina, Brazil), took part in the study. To assess the participants' socio-economic characteristics, an original questionnaire was formulated and sent to the children's parents. The clinical evaluation was carried out by a calibrated examiner using the deft/DMFT index for dental caries and Ghanim et al. (Ghanim et al., Eur Arch Paediatr Dent, 2015) criteria for HSPM. The data were analyzed through Poisson regression, using STATA statistical software, and the association analyses were presented by prevalence ratios (PR).

RESULTS

The prevalence of at least one HSPM-affected second molar was 24.5%. The prevalence of HSPM was associated to the city's geographical regions of the Educational hubs (p < 0.001). A significant association was found between dental caries and HSPM (p = 0.003; PR: 1.31; 95% CI 1.09-1.56). Children with HSPM were 31% more likely to experience dental caries than children without HSPM. Geographical regions of educational hubs were also significantly associated with HSPM (p < 0.001). None of the socioeconomic characteristics was associated with HSPM (p > 0.05).

CONCLUSION

HSPM is a common developmental defect of enamel in children in our study. The HSPM distribution was associated with the city's geographic regions. Children with HSPM are more likely to experience dental caries. Socioeconomic characteristics were not associated with HSPM.

Tissue engineering approaches for dental pulp regeneration: The development of novel bioactive materials using pharmacological epigenetic inhibitors

The drive for minimally invasive endodontic treatment strategies has shifted focus from technically complex and destructive root canal treatments towards more conservative vital pulp treatment. However, novel approaches to maintaining dental pulp vitality after disease or trauma will require the development of innovative, biologically-driven regenerative medicine strategies. For example, cell-homing and cell-based therapies have recently been developed in vitro and trialled in preclinical models to study dental pulp regeneration. These approaches utilise natural and synthetic scaffolds that can deliver a range of bioactive pharmacological epigenetic modulators (HDACis, DNMTis, and ncRNAs), which are cost-effective and easily applied to stimulate pulp tissue regrowth. Unfortunately, many biological factors hinder the clinical development of regenerative therapies, including a lack of blood supply and poor infection control in the necrotic root canal system. Additional challenges include a need for clinically relevant models and manufacturing challenges such as scalability, cost concerns, and regulatory issues. This review will describe the current state of bioactive-biomaterial/scaffold-based engineering strategies to stimulate dentine-pulp regeneration, explicitly focusing on epigenetic modulators and therapeutic pharmacological inhibition. It will highlight the components of dental pulp regenerative approaches, describe their current limitations, and offer suggestions for the effective translation of novel epigenetic-laden bioactive materials for innovative therapeutics.

Biological action of bleaching agents on tooth structure: A review

The use of bleaching agents to remove stains is one of the main dental procedures to improve the aesthetics of teeth. This review presents the main agents used for tooth whitening, existing clinical protocols, and the structural changes that may occur through their use. The main bleaching agents consist of hydrogen peroxide and carbamide peroxide, which are used in bleaching techniques for vital teeth. These techniques can be performed in the office by a professional or by the individual in a home en-vironment under professional guidance. Bleaching agents come in a variety of concentrations and there are over-the-counter products available on the market with lower concentrations of hydrogen peroxide. Due to the chemical characteristics of the agents, changes in the organic and inorganic content of the tooth structure can be observed. These changes are related to morphological changes characterized by in-creased permeability and surface roughness, such changes compromise the mechanical resistance of the tooth. Furthermore, bleaching agents can promote molecular changes after reaching the dental pulp, resulting in oxidative stress of pulp cells and the release of pro-inflammatory mediators. Despite the bleaching effectiveness, tooth sensitivity is considered the main side effect of use. Therefore, among the heterogeneity of protocols, those that used the bleaching agent for a prolonged time and in lower con-centrations presented more harmful effects on the tooth structure.

Unraveling Nanomaterials in Biomimetic Mineralization of Dental Hard Tissue: Focusing on Advantages, Mechanisms, and Prospects

The demineralization of dental hard tissue imposes considerable health and economic burdens worldwide, but an optimal method that can repair both the chemical composition and complex structures has not been developed. The continuous development of nanotechnology has created new opportunities for the regeneration and repair of dental hard tissue. Increasingly studies have reported that nanomaterials (NMs) can induce and regulate the biomimetic mineralization of dental hard tissue, but few studies have examined how they are involved in the different stages, let alone the relevant mechanisms of action. Besides their nanoscale dimensions and excellent designability, NMs play a corresponding role in the function of the raw materials for mineralization, mineralized microenvironment, mineralization guidance, and the function of mineralized products. This review comprehensively summarizes the advantages of NMs and examines the specific mineralization mechanisms. Design strategies to promote regeneration and repair are summarized according to the application purpose of NMs in the oral cavity, and limitations and development directions in dental hard tissue remineralization are proposed. This review can provide a theoretical basis to understand the interaction between NMs and the remineralization of dental hard tissue, thereby optimizing design strategy, rational development, and clinical application of NMs in the field of remineralization.

The circadian clock in enamel development

Circadian rhythms are self-sustaining oscillations within biological systems that play key roles in a diverse multitude of physiological processes. The circadian clock mechanisms in brain and peripheral tissues can oscillate independently or be synchronized/disrupted by external stimuli. Dental enamel is a type of mineralized tissue that forms the exterior surface of the tooth crown. Incremental Retzius lines are readily observable microstructures of mature tooth enamel that indicate the regulation of amelogenesis by circadian rhythms. Teeth enamel is formed by enamel-forming cells known as ameloblasts, which are regulated and orchestrated by the circadian clock during amelogenesis. This review will first examine the key roles of the circadian clock in regulating ameloblasts and amelogenesis. Several physiological processes are involved, including gene expression, cell morphology, metabolic changes, matrix deposition, ion transportation, and mineralization. Next, the potential detrimental effects of circadian rhythm disruption on enamel formation are discussed. Circadian rhythm disruption can directly lead to Enamel Hypoplasia, which might also be a potential causative mechanism of amelogenesis imperfecta. Finally, future research trajectory in this field is extrapolated. It is hoped that this review will inspire more intensive research efforts and provide relevant cues in formulating novel therapeutic strategies for preventing tooth enamel developmental abnormalities.

Expression patterns of keratin family members during tooth development and the role of keratin 17 in cytodifferentiation of stratum intermedium and stellate reticulum

Keratins are typical intermediate filament proteins of the epithelium that exhibit highly specific expression patterns related to the epithelial type and stage of cellular differentiation. They are important for cytoplasmic stability and epithelial integrity and are involved in various intracellular signaling pathways. Several keratins are associated with enamel formation. However, information on their expression patterns during tooth development remains lacking. In this study, we analyzed the spatiotemporal expression of keratin family members during tooth development using single-cell RNA-sequencing (scRNA-seq) and microarray analysis. scRNA-seq datasets from postnatal Day 1 mouse molars revealed that several keratins are highly expressed in the dental epithelium, indicating the involvement of keratin family members in cellular functions. Among various keratins, keratin 5 (Krt5), keratin 14 (Krt14), and keratin 17 (Krt17) are highly expressed in the tooth germ; KRT17 is specifically expressed in the stratum intermedium (SI) and stellate reticulum (SR). Depletion of Krt17 did not affect cell proliferation in the dental epithelial cell line SF2 but suppressed their differentiation ability. These results suggest that Krt17 is essential for SI cell differentiation. Furthermore, scRNA-seq results indicated that Krt5, Krt14, and Krt17 exhibited distinct expression patterns in ameloblast, SI, and SR cells. Our findings contribute to the elucidation of novel mechanisms underlying tooth development.

Cdc42 deletion yielded enamel defects by disrupting mitochondria and producing reactive oxygen species in dental epithelium

Developmental defects of enamel are common due to genetic and environmental factors before and after birth. Cdc42, a Rho family small GTPase, regulates prenatal tooth development in mice. However, its role in postnatal tooth development, especially enamel formation, remains elusive. Here, we investigated Cdc42 functions in mouse enamel development and tooth repair after birth. Cdc42 showed highly dynamic temporospatial patterns in the developing incisors, with robust expression in ameloblast and odontoblast layers. Strikingly, epithelium-specific Cdc42 deletion resulted in enamel defects in incisors. Ameloblast differentiation was inhibited, and hypomineralization of enamel was observed upon epithelial Cdc42 deletion. Proteomic analysis showed that abnormal mitochondrial components, phosphotransferase activity, and ion channel regulator activity occurred in the Cdc42 mutant dental epithelium. Reactive oxygen species accumulation was detected in the mutant mice, suggesting that abnormal oxidative stress occurred after Cdc42 depletion. Moreover, Cdc42 mutant mice showed delayed tooth repair and generated less calcified enamel. Mitochondrial dysfunction and abnormal oxygen consumption were evidenced by reduced Apool and Timm8a1 expression, increased Atp5j2 levels, and reactive oxygen species overproduction in the mutant repair epithelium. Epithelium-specific Cdc42 deletion attenuated ERK1/2 signaling in the labial cervical loop. Aberrant Sox2 expression in the mutant labial cervical loop after clipping might lead to delayed tooth repair. These findings suggested that mitochondrial dysfunction, up-regulated oxidative stress, and abnormal ion channel activity may be among multiple factors responsible for the observed enamel defects in Cdc42 mutant incisors. Overall, Cdc42 exerts multidimensional and pivotal roles in enamel development and is particularly required for ameloblast differentiation and enamel matrix formation.

Fluctuating asymmetry in third molar agenesis as an aid to estimate socioeconomic status

Traditionally, dental identification techniques are used to establish identity or assist in reconstructing an individual's biological profile. However, other aspects of identity, namely socioeconomic status (SES), can be estimated through teeth. This work aims to evaluate the influence of SES on third molar agenesis in a Portuguese population. X-rays from 448 subjects (223 belonging to a high and 225 to a low socioeconomic status) were assessed and demographic data (age, sex) and dental history were registered. Frequencies and associations between the variables were analyzed using the chi-square test. For each group, differences between third molar agenesis were studied using the Wilcoxon test. The significance level was 5%. X-rays displaying at least one agenesis were more common in females (in both SES groups). Differences between socioeconomic status were found in female subjects' upper right and lower left third molars, with a higher frequency of agenesis in the lower SES group. Agenesis of lower third molars displayed fluctuant asymmetry in both groups, whereas agenesis of upper third molars was also present in the lower SES group. These results suggest that socioeconomic status can affect third molar agenesis prevalence, and fluctuant asymmetry seems more prevalent in the lower SES, as it affects all third molars.

Roles of the histone methyltransferase SET domain bifurcated 1 in epithelial cells during tooth development

OBJECTIVE

This study aimed to reveal the effects of SET domain bifurcated 1 (SETDB1) on epithelial cells during tooth development.

DESIGN

We generated conditional knockout mice (Setdb1fl/fl,Keratin14-Cre+ mice), in which Setdb1 was deleted only in epithelial cells. At embryonic day 14.5 (E14.5), immunofluorescence staining was performed to confirm the absence of SETDB1 within the epithelium of tooth embryos from Setdb1fl/fl,Keratin14-Cre+ mice. Mouse embryos were harvested after reaching embryonic day 13.5 (E13.5), and sections were prepared for histological analysis. To observe tooth morphology in detail, electron microscopy and micro-CT analysis were performed at postnatal months 1 (P1M) and 6 (P6M). Tooth embryos were harvested from postnatal day 7 (P7) mice, and the epithelial components of the tooth embryos were isolated and examined using quantitative RT-PCR for the expression of genes involved in tooth development.

RESULTS

Setdb1fl/fl,Keratin14-Cre+ mice exhibited enamel hypoplasia, brittle and fragile dentition, and significant abrasion. Coronal sections displayed abnormal ameloblast development, including immature polarization, and a thin enamel layer that detached from the dentinoenamel junction at P7. Electron microscopic analysis revealed characteristic findings such as an uneven surface and the absence of an enamel prism. The expression of Msx2, Amelogenin (Amelx), Ameloblastin (Ambn), and Enamelin (Enam) was significantly downregulated in the epithelial components of tooth germs in Setdb1fl/fl,Keratin14-Cre+ mice.

CONCLUSIONS

These results indicate that SETDB1 in epithelial cells is important for tooth development and clarify the relationship between the epigenetic regulation of SETDB1 and amelogenesis imperfecta for the first time.