Mineralization Of Dental Tissues Research Articles

The tooth: A marker of developmental abnormalities

Tooth formation results from specific epithelial-mesenchymal interactions, which summarize a number of developmental processes. Tooth anomalies may thus reflect subclinical diseases of the kidney, bone and more broadly of the mineral metabolism, skin or nervous system. Odontogenesis starts from the 3rd week of intrauterine life by the odontogenic orientation of epithelial cells by a first PITX2 signal. The second phase is the acquisition of the number, shape, and position of teeth. It depends on multiple transcription and growth factors (BMP, FGF, SHH, WNT). These ecto-mesenchymal interactions guide cell migration, proliferation, apoptosis and differentiation ending in the formation of the specific dental mineralized tissues. Thus, any alteration will have consequences on the tooth structure or shape. Resulting manifestations will have to be considered in the patient phenotype and the multidisciplinary care, but also may contribute to identify the altered genetic circuity.

Effects of photodynamic therapy on Streptococcus mutans and enamel remineralization of multifunctional TiO2-HAP composite nanomaterials

BackgroundAs photosensitizer and photocatalyst, titanium dioxide (TiO2) can produce a photodynamic reaction for antibacterial treatment. This study aims to explore a Titanium dioxide/nano-hydroxyapatite (TiO2-HAP) composite combined with the dental curing lamp (385–515 nm) in clinical which could inhibit the dental plaque biofilm formed by Streptococcus mutans (S. mutans) and promote the enamel surface remineralization simultaneously. MethodsX-ray Diffraction (XRD) and high resolution transmission electron microscope (HRTEM) were used to detect the characterization of TiO2-HAP composite nanomaterials. Photodynamic properties of TiO2-HAP were detected by Diffuse reflectance spectrum (DRS) and fluorescence spectroscopy. Bacterial growth was measured by reading the absorbance of bacterial cultures and confocal microscope was used to observe the biofilm removal ability of nanomaterials. The ability of TiO2-HAP to promote enamel remineralization was measured by Scanning electron microscope (SEM). ResultsThe OD 600 of S. mutans was 0.76 in the control group and 0.13 in group of TiO2-HAP with exposure to light-emitting diode (LED) (150 mW/cm2) for 5 min, suggesting its sustained antibacterial potency and inhibition of the metabolic activity of dental plaque microcosm biofilm. Also, the release of calcium and phosphorus ions in TiO2-HAP can promote enamel mineralization simultaneously. After 15 days of remineralization, the Ca/P ratio of demineralized enamel surface increased from 1.28 to 1.67, which was similar to that of normal enamel. ConclusionsThe TiO2-HAP exhibit a promising anti-bacterial activity and remineralization capacity which can prevent the occurrence of caries to the greatest extent and promote the biomimetic mineralization of dental tissues.

Insulin-like growth factor 1 promotes neural differentiation of human stem cells from the apical papilla

ObjectiveInsulin-like growth factor 1 (IGF1) is one of the vital factors in regenerative endodontics. Previous studies have focused on the role of IGF1 in the mineralization of dental tissues. However, the role of IGF1 in the neural differentiation of dental stem cells was little discussed. DesignIGF1 was overexpressed in human stem cells from the apical papilla (hSCAPs) by lentivirus and knocked down in hSCAPs by small interfering RNA. The neural differentiation level of hSCAPs was investigated histologically by HE staining and Nissl staining after neural induction for 3 days. The expression of proteins was examined by western blot and immunofluorescence. ResultsIGF1 promoted neural differentiation of hSCAPs, more cell processes and Nissl-positive body stained cells. IGF1 overexpression could both promote glial differentiation in hSCAPs, characterized by the increase of S100β and GFAP proteins, and neuronal differentiation, characterized by the increase of βIII-tubulin and functional GAD67/vGLUT1 proteins. Conversely, IGF1 knockdown suppressed both glial and neuronal differentiation. IGF1 activated AKT to regulate the early neural differentiation of hSCAPs. ConclusionsThe results indicate IGF1 could promote neural differentiation of hSCAPs by activating AKT signaling and provide a cue for the candidate of induced neural seeding cells in regenerative endodontics.

Mineralization of dental tissues and caries lesions detailed with Raman microspectroscopic imaging.

Dental caries is the most common oral disease that causes demineralization of the enamel and later of the dentin. Depth-wise assessment of the demineralization process could be used to help in treatment planning. In this study, we aimed to provide baseline information for the development of a Raman probe by characterizing the mineral composition of the dental tissues from large composition maps (6 × 3 mm2 with 15 μm step size) using Raman microspectroscopy. Ten human wisdom teeth with different stages of dental caries lesions were examined. All of the teeth were cut in half at representative locations of the caries lesions and then imaged with a Raman imaging microscope. The pre-processed spectral maps were combined into a single data matrix, and the spectra of the enamel, dentin, and caries were identified by K-means cluster analysis. Our results showed that unsupervised identification of dental caries is possible with the K-means clustering. The compositional analysis revealed that the carious lesions are less mineralized than the healthy enamel, and when the lesions extend into the dentin, they are even less mineralized. Furthermore, there were more carbonate imperfections in the mineral crystal lattice of the caries tissues than in healthy tissues. Interestingly, we observed gradients in the sound enamel showing higher mineralization and greater mineral crystal perfection towards the tooth surface. To conclude, our results provide a baseline for the methodological development aimed at clinical diagnostics for the early detection of active caries lesions.

Dental defects in the primary dentition associated with hypophosphatasia from biallelic ALPL mutations.

ALPL encodes tissue-nonspecific alkaline phosphatase (TNAP), an enzyme expressed in bone, teeth, liver, and kidney. ALPL loss-of-function mutations cause hypophosphatasia (HPP), an inborn error-of-metabolism that produces skeletal and dental mineralization defects. Case reports describe widely varying dental phenotypes, making it unclear how HPP comparatively affects the three unique dental mineralized tissues: enamel, dentin, and cementum. We hypothesized that HPP affected all dental mineralized tissues and aimed to establish quantitative measurements of dental tissues in a subject with HPP. The female proband was diagnosed with HPP during childhood based on reduced alkaline phosphatase activity (ALP), mild rachitic skeletal effects, and premature primary tooth loss. The diagnosis was subsequently confirmed genetically by the presence of compound heterozygous ALPL mutations (exon 5: c.346G>A, p.A116T; exon 10: c.1077C>G, p.I359M). Dental defects in 8 prematurely exfoliated primary teeth were analyzed by high resolution micro-computed tomography (micro-CT) and histology. Similarities to the Alpl-/- mouse model of HPP were identified by additional analyses of murine dentoalveolar tissues. Primary teeth from the proband exhibited substantial remaining root structure compared to healthy control teeth. Enamel and dentin densities were not adversely affected in HPP vs. control teeth. However, analysis of discrete dentin regions revealed an approximate 10% reduction in the density of outer mantle dentin of HPP vs. control teeth. All 4 incisors and the molar lacked acellular cementum by micro-CT and histology, but surprisingly, 2 of 3 prematurely exfoliated canines exhibited apparently normal acellular cementum. Based on dentin findings in the proband's teeth, we examined dentoalveolar tissues in a mouse model of HPP, revealing that the delayed initiation of mineralization in the incisor mantle dentin was associated with a broader lack of circumpulpal dentin mineralization. This study describes a quantitative approach to measure effects of HPP on dental tissues. This approach has uncovered a previously unrecognized novel mantle dentin defect in HPP, as well as a surprising and variable cementum phenotype within the teeth from the same HPP subject.

Antibiotics Disturb Dentin Formation and Differentiation of Dental Pulp Stem Cells: The Role of Microbiota in Cellular Turnover of Mouse Incisor.

Dentin formation was dependent on osteo-/odontogenic differentiation of dental pulp stem cells (DPSCs). It was observed in previous studies that antibiotic treatment in a clinical and animal model resulted in impaired mineralization of dental tissues. We previously reported that microbiota maintained the function of bone marrow mesenchymal stem cells, while whether microbiota dysbiosis caused by antibiotic treatment contributed to DPSCs dysfunction and impaired dentin formation is still not known. In this study, we aimed to clarify the role of microbiota or its metabolic products on dental mineralization and the function of DPSCs. Mice were treated with antibiotics to disrupt microbiota; then, the growth rate and histological characteristics of incisors as well as the biological characteristics of DPSCs in vitro were compared with specific pathogen-free (SPF) mice. In antibiotic-treated mice (AbT), we found a diminished quantity of microbiota and reduced growth rate of mechanical injured incisor, as well as decreased colony-forming rate and impaired ability of osteo-/odontogenic differentiation of DPSCs, in comparison to SPF mice. Colonization of AbT mice with SPF mice replanted the microbiota by cohousing (conventionalized (ConvD)) and normalized the growth rate of injured incisors and colony-forming and osteo-/odontogenic differentiation ability of DPSCs. Giving short-chain fatty acids (SCFAs) by oral gavage after antibiotic treatment also rescued the growth rate of incisors and the differentiation ability of DPSCs and enhanced proliferation ability of DPSCs. Collectively, gut microbiota could make contribution to maintain continuous growth of injured rodent incisor and differentiation capacity of DPSCs; SCFAs might play a crucial role in this process.

Scanning electron microscopy approach to observe bacterial adhesion to dental surfaces

AIMTo describe the in vitro bacterial adhesion protocol of Streptococcus mutans and Lactobacillus casei on dental surfaces for a qualitative approach by Scanning Electron Microscopy (SEM) observations. A control and Amelogenesis Imperfecta (AI) affected teeth were used to validate the protocol. METHOD DETAILSEight teeth were collected and fixed in 10% formalin during 10 days. Crowns were fragmented into 4 parts and kept in the freshly prepared artificial saliva. For the preparation of bacterial suspensions, bacterial strains (S. mutans and L. casei) were incubated in a freshly prepared culture medium. After two successive cultures at 37 °C and 3 rinces, bacterial suspensions were prepared in artificial saliva and adjusted to correspond to 108 CFU ml−1. Bacterial adhesion was carried out by sedimentation. Dental fragments were immersed in bacterial suspensions and rinsed with PBS to remove non adherent bacteria. Adherent bacteria were fixed with glutaraldehyde. Finally, teeth samples were dehydrated, coated, dried and observed using high-resolution SEM (JEOL, JSM-5400). RESULTSSEM observations showed adherence of spheric stuctures, identified as S. mutans and bacilic structures identified as L. casei. CONCLUSIONAdhesion of bacteria could be observed by SEM and depends on the quality of dental mineralized tissues.

Trps1 transcription factor regulates mineralization of dental tissues and proliferation of tooth organ cells

Mutations of the TRPS1 gene cause trichorhinophalangeal syndrome (TRPS), a skeletal dysplasia with dental abnormalities. TRPS dental phenotypes suggest that TRPS1 regulates multiple aspects of odontogenesis, including the tooth number and size. Previous studies delineating Trps1 expression throughout embryonic tooth development in mice detected strong Trps1 expression in dental mesenchyme, preodontoblasts, and dental follicles, suggesting that TRPS dental phenotypes result from abnormalities in early developmental processes. In this study, Trps1+/− and Trps1−/− mice were analyzed to determine consequences of Trps1 deficiency on odontogenesis. We focused on the aspects of tooth formation that are disturbed in TRPS and on potential molecular abnormalities underlying TRPS dental phenotypes. Microcomputed tomography analyses of molars were used to determine tooth size, crown shape, and mineralization of dental tissues. These analyses uncovered that disruption of one Trps1 allele is sufficient to impair mineralization of dentin in both male and female mice. Enamel mineral density was decreased only in males, while mineralization of the root dental tissues was decreased only in females. In addition, significantly smaller teeth were detected in Trps1+/− females. Histomorphometric analyses of tooth organs showed reduced anterior-posterior diameter in Trps1−/− mice. BrdU-incorporation assay detected reduced proliferation of mesenchymal and epithelial cells in Trps1−/− tooth organs. Immunohistochemistry for Runx2 and Osx osteogenic transcription factors revealed changes in their spatial distribution in Trps1−/− tooth organs and uncovered cell-type specific requirements of Trps1 for Osx expression. In conclusion, this study has demonstrated that Trps1 is a positive regulator of cell proliferation in both dental mesenchyme and epithelium, suggesting that the microdontia in TRPS is likely due to decreased cell proliferation in developing tooth organs. Furthermore, the reduced mineralization observed in Trps1+/− mice may provide some explanation for the extensive dental caries reported in TRPS patients.

Methods for In Situ Protein Visualization in Dental Mineralized Tissues.

Immunohistochemistry (IHC) is a technique based on the specificity of antibody-antigen principle used commonly to detect antigens in tissue sections. The immune labeling can be performed in paraffin sections, cryostat sections, and ultrathin sections and can be observed in light confocal and transmission electron microscopy. However, the use of immunohistochemical techniques for the study of mineralized tissues has been a challenge for decades (Berdal et al., Arch Oral Biol 36:715-725, 1991; Nanci et al., Eur J Histochem 52:201-214, 2008). Specific procedures are necessary when compared with soft tissue immunohistochemistry. This chapter describes methods for IHC on Tissue-Tek O.C.T. compound and paraffin-embedded sections to detect antigens in the dental mineralized tissues.

Protocols for Studying Formation and Mineralization of Dental Tissues In Vivo: Extraction Protocol for Isolating Dentin Matrix Proteins from Developing Teeth.

The organic material in developing dentin is 90% type I collagen and 10% non-collagenous proteins. The key to understanding dentin biomineralization is to study how these proteins collectively precipitate and organize hydroxyapatite crystals. The first step in characterizing the proteins within a mineralizing matrix is to efficiently extract and isolate the essential molecular participants and elucidate their structural and biochemical properties. In this study, we expanded previous approaches to develop an improved strategy for the extraction of extracellular matrix proteins from the dentin of developing teeth. Proteins in dentin powder were sequentially extracted in the order Tris-guanidine buffer, HCl-formic acid solution, acetic acid-NaCl solution, Tris-NaCl buffer, and a second Tris-guanidine buffer. Individual fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), by gelatin or casein zymography, and by Western blot analysis using dentin sialoprotein (DSP)- or dentin glycoprotein (DGP)-specific antibodies. This approach was used to purify assorted porcine dentin non-collagenous proteins.

Evolution of dental tissue mineralization: an analysis of the jawed vertebrate SPARC and SPARC-L families

BackgroundThe molecular bases explaining the diversity of dental tissue mineralization across gnathostomes are still poorly understood. Odontodes, such as teeth and body denticles, are serial structures that develop through deployment of a gene regulatory network shared between all gnathostomes. Dentin, the inner odontode mineralized tissue, is produced by odontoblasts and appears well-conserved through evolution. In contrast, the odontode hypermineralized external layer (enamel or enameloid) produced by ameloblasts of epithelial origin, shows extensive structural variations. As EMP (Enamel Matrix Protein) genes are as yet only found in osteichthyans where they play a major role in the mineralization of teeth and others skeletal organs, our understanding of the molecular mechanisms leading to the mineralized odontode matrices in chondrichthyans remains virtually unknown.ResultsWe undertook a phylogenetic analysis of the SPARC/SPARC-L gene family, from which the EMPs are supposed to have arisen, and examined the expression patterns of its members and of major fibrillar collagens in the spotted catshark Scyliorhinus canicula, the thornback ray Raja clavata, and the clawed frog Xenopus tropicalis. Our phylogenetic analyses reveal that the single chondrichthyan SPARC-L gene is co-orthologous to the osteichthyan SPARC-L1 and SPARC-L2 paralogues. In all three species, odontoblasts co-express SPARC and collagens. In contrast, ameloblasts do not strongly express collagen genes but exhibit strikingly similar SPARC-L and EMP expression patterns at their maturation stage, in the examined chondrichthyan and osteichthyan species, respectively.ConclusionsA well-conserved odontoblastic collagen/SPARC module across gnathostomes further confirms dentin homology. Members of the SPARC-L clade evolved faster than their SPARC paralogues, both in terms of protein sequence and gene duplication. We uncover an osteichthyan-specific duplication that produced SPARC-L1 (subsequently lost in pipidae frogs) and SPARC-L2 (independently lost in teleosts and tetrapods).Our results suggest the ameloblastic expression of the single chondrichthyan SPARC-L gene at the maturation stage reflects the ancestral gnathostome situation, and provide new evidence in favor of the homology of enamel and enameloids in all gnathostomes.

Hypophosphatasia: oral cavity and dental disorders

Dental anomalies exist in every subtype of hypophosphatasia (HPP), from the most severe to the most moderate, called odontohypophosphatasia. The forms are defined by the age at onset of the initial symptoms. These anomalies affect all dental mineralized tissues from enamel, dentin and cementum to alveolar bone in a gradient proportional to the severity of the disease. Early loss of the deciduous teeth, before 3 years of age, and then possibly of the permanent teeth, is due to an abnormality of the cementum, the tissue attaching the teeth to alveolar bone, and is the most frequent abnormality. Tooth loss is a very important diagnostic sign and needs to be recognized. Patients with HPP need specialized oral and dental care in coordination with the reference and expert centers. The oral and dental signs and their treatment remain poorly known. The recording of the abnormalities and their treatment in a registry is indispensable in order to enhance patient management and oral and dental health.

Distribution of Cathepsin K in Late Stage of Tooth Germ Development and Its Function in Degrading Enamel Matrix Proteins in Mouse.

Cathepsin K (CTSK) is a member of cysteine proteinase family, and is predominantly expressed in osteoclastsfor degradationof bone matrix proteins. Given the similarity in physical properties of bone and dental mineralized tissues, including enamel, dentin and cementum, CTSK is likely to take part in mineralization process during odontogenesis. On the other hand, patients with pycnodysostosis caused by mutations of the CTSK gene displayedmultipledental abnormalities, such as hypoplasia of the enamel, obliterated pulp chambers, hypercementosis and periodontal disease. Thereforeitis necessary to study the metabolic role of CTSK in tooth matrix proteins. In this study, BALB/c mice at embryonic day 18 (E18), post-natal day 1 (P1), P5, P10 and P20 were used (5 mice at each time point)for systematic analyses of CTSK expression in the late stage of tooth germ development. We found that CTSK was abundantly expressed in the ameloblasts during secretory and maturation stages (P5 and P10) by immunohistochemistry stainings.During dentinogenesis, the staining was also intense in the mineralization stage (P5 and P10),but not detectable in the early stage of dentin formation (P1) and after tooth eruption (P20).Furthermore, through zymography and digestion test in vitro, CTSK was proved to be capable of hydrolyzing Emdogain and also cleaving Amelogenininto multiple products. Our resultsshed lights on revealing new functions of CTSK and pathogenesis of pycnodysostosis in oral tissues.

Endogenous Enzymes in Root Caries.

Similar to coronal caries, root caries results from a disequilibrium of the de-remineralization balance in favor of the demineralization process. It mainly involves a bacterial shift in favor of an increase in the proportion of acidogenic and aciduric bacteria. This process permanently damages the dental mineralized tissues, namely the dental cementum and dentin. In addition to the demineralization and exposure of the dentin or the cementum organic matrix, acid production by cariogenic bacteria induces the activation of endogenous (host-derived) enzymes within the dentin and saliva. These enzymes include matrix metalloproteinases and cathepsins. Once activated, these potent proteolytic enzymes collectively have the capacity to degrade all the components of the exposed organic dentin and cementum matrices. In this chapter, the description of the healthy cement and dentin organic matrices and their endogenous proteases will be followed by the role of these proteases in the root caries process.

A Critical Role of TRPM7 As an Ion Channel Protein in Mediating the Mineralization of the Craniofacial Hard Tissues

Magnesium ion (Mg2+) is the fourth most common cation in the human body, and has a crucial role in many physiological functions. Mg2+ homeostasis is an important contributor to bone development, however, its roles in the development of dental mineralized tissues have not yet been well known. We identified that transient receptor potential cation channel, subfamily M, member 7 (TRPM7), was significantly upregulated in the mature ameloblasts as compared to other ameloblasts through our whole transcript microarray analyses of the ameloblasts. TRPM7, an ion channel for divalent metal cations with an intrinsic serine/threonine protein kinase activity, has been characterized as a key regulator of whole body Mg2+ homeostasis. Semi-quantitative PCR and immunostaining for TRMP7 confirmed its upregulation during the maturation stage of enamel formation, at which ameloblasts direct rapid mineralization of the enamel matrix. The significantly hypomineralized craniofacial structures, including incisors, molars, and cranial bones were demonstrated by microCT analysis, von Kossa and trichrome staining in Trpm7Δkinase∕+ mice. A previously generated heterozygous mouse model with the deletion of the TRPM7 kinase domain. Interestingly, the skeletal phenotype of Trpm7Δkinase∕+ mice resembled those found in the tissue-nonspecific alkaline phosphatase (Alpl) KO mice, thus we further examined whether ALPL protein content and alkaline phosphatase (ALPase) activity in ameloblasts, odontoblasts and osteoblasts were affected in those mice. While ALPL protein in Trpm7Δkinase∕+ mice remained at the similar level as that in wt mice, ALPase activities in the Trpm7Δkinase∕+ mice were almost nonexistent. Supplemented magnesium successfully rescued the activities of ALPase in ameloblasts, odontoblasts and osteoblasts of Trpm7Δkinase∕+ mice. These results suggested that TRPM7 is essential for mineralization of enamel as well as dentin and bone by providing sufficient Mg2+ for the ALPL activity, underlining the key importance of ALPL for biomineralization.

FAM20C Plays an Essential Role in the Formation of Murine Teeth

FAM20C is highly expressed in bone and tooth. Previously, we showed that Fam20C conditional knock-out (KO) mice manifest hypophosphatemic rickets, which highlights the crucial roles of this molecule in promoting bone formation and mediating phosphate homeostasis. In this study, we characterized the dentin, enamel, and cementum of Sox2-Cre-mediated Fam20C KO mice. The KO mice exhibited small malformed teeth, severe enamel defects, very thin dentin, less cementum than normal, and overall hypomineralization in the dental mineralized tissues. In situ hybridization and immunohistochemistry analyses revealed remarkable down-regulation of dentin matrix protein 1 (DMP1) and dentin sialophosphoprotein in odontoblasts, along with a sharply reduced expression of ameloblastin and amelotin in ameloblasts. Collectively, these data indicate that FAM20C is essential to the differentiation and mineralization of dental tissues through the regulation of molecules critical to the differentiation of tooth-formative cells.

Effect of Wnt6 on Human Dental Papilla Cells In Vitro

Introduction The Wnt signaling pathway plays an important role in tissue development by acting on proliferation, differentiation, and cell fate decisions. Because the role of Wnt6 in tooth development was still unknown, the purpose of this study was to investigate the role of Wnt6 in tooth morphogenesis and dental tissue mineralization by elucidating its effect on human dental papilla cells (hDPCs) in vitro. Methods Human dental papilla cells were enzymatically separated from tooth germs. Recombinant adenovirus encoding full-length Wnt6 cDNA was constructed to overexpress Wnt6, and the biologic effects of Wnt6 on hDPCs were investigated. Wnt6-transduced changes in hDPC proliferation were examined by means of a 5-bromodeoxyuridine (BrdU) incorporation assay and cell cycle analysis. Wnt6-transduced changes in hDPC differentiation were investigated by evaluating alkaline phosphatase (ALPase) activity, by a mineralization assay, and analysis of mineralization-related gene expression including ALP, type I collagen (Col I), osteonectin (ON), osteopontin (OPN), bone sialoprotein (BSP), and dentin matrix protein-1 (DMP-1). Results Wnt6 overexpression had no significant effect on the proliferation of hDPCs by BrdU incorporation assay and flow cytometric analysis. Wnt6 enhanced differentiation of hDPCs into functional odontoblast-like cells with up-regulated activity of ALPase and the expression of mineralization-related genes such as ALP, Col I, ON, OPN, BSP, and DMP-1. Wnt6 overexpression also promoted the mineralization of hDPCs. Conclusions Our findings verified that Wnt6 plays an important role in tooth development by promoting hDPC differentiation, without significant effects on hDPC proliferation.

Stem Cell Regulatory Gene Expression in Human Adult Dental Pulp and Periodontal Ligament Cells Undergoing Odontogenic/Osteogenic Differentiation

IntroductionDuring development and regeneration, odontogenesis and osteogenesis are initiated by a cascade of signals driven by several master regulatory genes. MethodsIn this study, we investigated the differential expression of 84 stem cell–related genes in dental pulp cells (DPCs) and periodontal ligament cells (PDLCs) undergoing odontogenic/osteogenic differentiation. ResultsOur results showed that, although there was considerable overlap, certain genes had more differential expression in PDLCs than in DPCs. CCND2, DLL1, and MME were the major upregulated genes in both PDLCs and DPCs, whereas KRT15 was the only gene significantly downregulated in PDLCs and DPCs in both odontogenic and osteogenic differentiation. Interestingly, a large number of regulatory genes in odontogenic and osteogenic differentiation interact or crosstalk via Notch, Wnt, transforming growth factor β (TGF-β)/bone morphogenic protein (BMP), and cadherin signaling pathways, such as the regulation of APC, DLL1, CCND2, BMP2, and CDH1. Using a rat dental pulp and periodontal defect model, the expression and distribution of both BMP2 and CDH1 have been verified for their spatial localization in dental pulp and periodontal tissue regeneration. ConclusionsThis study has generated an overview of stem cell–related gene expression in DPCs and PDLCs during odontogenic/osteogenic differentiation and revealed that these genes may interact through the Notch, Wnt, TGF-β/BMP, and cadherin signaling pathways to play a crucial role in determining the fate of dental derived cell and dental tissue regeneration. These findings provided a new insight into the molecular mechanisms of the dental tissue mineralization and regeneration.

Dentonin, a MEPE Fragment, Initiates Pulp-healing Response to Injury

Phosphorylated extracellular matrix proteins, including matrix extracellular phosphoprotein (MEPE), are involved in the formation and mineralization of dental tissues. In this study, we evaluated the potential of Dentonin, a synthetic peptide derived from MEPE, to promote the formation of reparative dentin. Agarose beads, either soaked with Dentonin or unloaded, were implanted into the pulps of rat molars, and examined 8, 15, and 30 days after treatment. At day 8, Dentonin promoted the proliferation of pulp cells, as visualized by PCNA-labeling. RP59-positive osteoblast progenitors were located around the Dentonin-soaked beads. PCNA- and RP59-labeling were decreased at day 15, while osteopontin, weakly labeled at day 8, was increased at 15 days, but dentin sialoprotein was undetectable at any time. At 8 days, precocious reparative dentin formation occurred in pulps containing Dentonin-soaked beads, with formation slowing after 15 days. These results suggest that Dentonin affects primarily the initial cascade of events leading to pulp healing.

In vitro study of the effects of copper ion on osteoclastic resorption in various dental mineralized tissues

To investigate the effects of copper ion on osteoclastic resorption in various dental mineralized tissues. Osteoclasts were separated from long-limb bones of neonatal rabbits, and cultured with de-activated human tooth slices and glass slices. The cells in the experiment group were treated with (1 x 10(-14))-1 x (10(-4)) mol/L copper + 10% (volume fraction) fetal calf serum (FCS) + alpha-MEM, while the cells in control group cells were grown in 10% FCS + alpha-MEM. Osteoclasts on glass slices were stained by TRAP staining. The absorption pits on tooth slices were observed by inverted phase contrast microscope. The resorbing activity was evaluated with the concentration of calcium in the supernatant liquid of osteoclasts. The ratio between the concentration of calcium in the experiment group and control group was termed as the resorption index. The isolated cells were multinuclear and TRAP positive in cytoplasma. Osteoclasts resorbed teeth slices first on the cementum and dentin. Compared with those on bone slices, the lacunae on the dental slices numbered less, with smaller volume and shallower in depth. Microscopy showed that the number and area of absorption pits formed on treated tissues were less than those on control tissues. The content of calcium in the supernatant liquid decreased in the concentrations of 1 x 10(-14) mol/L - 1 x 10(-4) mol/L copper, especially in the group of 1 x 10(-10) mol/L copper at 3rd day (P < 0.05) and 1 x 10(-4) mol/L, 1 x 10(-10) - 1 x 10(-12) mol/L copper at 7th day (P < 0.05). Their resorption index was lower than one. Extracellular copper ion can inhibit osteoclastic resorption on dental slices.