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It is remarkable how teeth maintain their healthy condition under exceptionally high levels of mechanical loading. This suggests the presence of inherent mechanical adaptation mechanisms within their structure to counter constant stress. Dentin, situated between enamel and pulp, plays a crucial role in mechanically supporting tooth function. Its intermediate stiffness and viscoelastic properties, attributed to its mineralized, nanofibrous extracellular matrix, provide flexibility, strength, and rigidity, enabling it to withstand mechanical loading without fracturing. Moreover, dentin’s unique architectural features, such as odontoblast processes within dentinal tubules and spatial compartmentalization between odontoblasts in dentin and sensory neurons in pulp, contribute to a distinctive sensory perception of external stimuli while acting as a defensive barrier for the dentin-pulp complex. Since dentin’s architecture governs its functions in nociception and repair in response to mechanical stimuli, understanding dentin mechanobiology is crucial for developing treatments for pain management in dentin-associated diseases and dentin-pulp regeneration. This review discusses how dentin’s physical features regulate mechano-sensing, focusing on mechano-sensitive ion channels. Additionally, we explore advanced in vitro platforms that mimic dentin’s physical features, providing deeper insights into fundamental mechanobiological phenomena and laying the groundwork for effective mechano-therapeutic strategies for dentinal diseases.

BMP signaling plays an important role in dentin development. BMPs and antagonists regulate odontoblast differentiation and downstream gene expression via canonical Smad and non-canonical Smad signaling pathways. The interaction of BMPs with their receptors leads to the formation of complexes and the transduction of signals to the canonical Smad signaling pathway (for example, BMP ligands, receptors, and Smads) and the non-canonical Smad signaling pathway (for example, MAPKs, p38, Erk, JNK, and PI3K/Akt) to regulate dental mesenchymal stem cell/progenitor proliferation and differentiation during dentin development and homeostasis. Both the canonical Smad and non-canonical Smad signaling pathways converge at transcription factors, such as Dlx3, Osx, Runx2, and others, to promote the differentiation of dental pulp mesenchymal cells into odontoblasts and downregulated gene expressions, such as those of DSPP and DMP1. Dysregulated BMP signaling causes a number of tooth disorders in humans. Mutation or knockout of BMP signaling-associated genes in mice results in dentin defects which enable a better understanding of the BMP signaling networks underlying odontoblast differentiation and dentin formation. This review summarizes the recent advances in our understanding of BMP signaling in odontoblast differentiation and dentin formation. It includes discussion of the expression of BMPs, their receptors, and the implicated downstream genes during dentinogenesis. In addition, the structures of BMPs, BMP receptors, antagonists, and dysregulation of BMP signaling pathways associated with dentin defects are described.

Cell-based tissue engineering is a promising method for dentin-pulp complex (DPC) regeneration. The challenges associated with DPC regeneration include the generation of a suitable microenvironment that facilitates the complete odontogenic differentiation of dental pulp stem cells (DPSCs) and the rapid induction of angiogenesis. Thus, the survival and subsequent differentiation of DPSCs are limited. Extracellular matrix (ECM)-like biomimetic hydrogels composed of self-assembling peptides (SAPs) were developed to provide an appropriate microenvironment for DPSCs. For functional DPC regeneration, the most important considerations are to provide an environment that promotes the adequate attachment of DPSCs and rapid vascularization of the regenerating pulp. Morphogenic signals in the form of growth factors (GFs) have been incorporated into SAPs to promote productive DPSC behaviors. However, the use of GFs has several drawbacks. We envision using a scaffold with SAPs coupled with long-term factors to increase DPSC attachment and vascularization as a method to address this challenge. In this study, we developed synthetic material for an SAP-based scaffold with RGD- and vascular endothelial growth factor (VEGF)-mimetic peptide epitopes with the dual functions of dentin and pulp regeneration. DPSCs and human umbilical vein endothelial cells (HUVECs) were used to evaluate the biological effects of SAP-based scaffolds. Furthermore, the pulpotomized molar rat model was employed to test the reparative and regenerative effects of SAP-based scaffolds. This scaffold simultaneously presented RGD- and VEGF-mimetic peptide epitopes and provided a 3D microenvironment for DPSCs. DPSCs grown on this composite scaffold exhibited significantly improved survival and angiogenic and odontogenic differentiation in the multifunctionalized group in vitro. Histological and functional evaluations of a partially pulpotomized rat model revealed that the multifunctionalized scaffold was superior to other options with respect to stimulating pulp recovery and dentin regeneration in vivo. Based on our data obtained with the functionalized SAP scaffold, a 3D microenvironment that supports stem cell adhesion and angiogenesis was generated that has great potential for dental pulp tissue engineering and regeneration.

Reparative tertiary dentinogenesis requires the recruitment and odontogenic differentiation of dental pulp stem cells (DPSCs). Extracellular vesicles (EVs) as bioactive molecules have gained attention in regenerative medicine for their ability to mediate tissue repair through intercellular communication, influencing cell recruitment, proliferation, and differentiation. This study aimed to evaluate the effects of EVs on DPSC homing and odontogenic differentiation for dentin regeneration. DPSC-derived EVs were cultured in either growth (EV-G) or odontogenic differentiation (EV-O) conditions and isolated using a modified precipitation method. EVs were characterized by nanoparticle tracking analysis, scanning electron microscopy, antibody array, and cellular uptake assay. Treatment with 5 × 108 EVs/mL significantly enhanced DPSC chemotaxis and proliferation compared with a no-treatment control and a lower dosage of EV (5 × 107 EVs/mL). Gene expression and biochemical analyses revealed that EV-O up-regulated odontogenic markers including collagen type 1A1 (COL1A1), runt-related transcription factor 2 (RUNX2), and alkaline phosphatase (ALP). EV-O enhanced dentin regeneration by approximately 55% over vehicle controls in a rabbit partial dentinotomy/pulpotomy model. We identified key microRNAs (miR-21-5p, miR-221-3p, and miR-708-3p) in EV-O involved in cell homing and odontogenesis. In conclusion, our EV-based cell homing and odontogenic differentiation strategy has significant therapeutic potential for dentin regeneration.

Dentin‐pulp complex regeneration is a promising alternative treatment for the irreversible pulpitis caused by tooth trauma or dental caries. This process mainly relies on the recruitment of endogenous or the transplanted dental pulp stem cells (DPSCs) to guide dentin‐pulp tissue formation. Platelet‐derived growth factor (PDGF), a well‐known potent mitogenic, angiogenic, and chemoattractive agent, has been widely used in tissue regeneration. However, the mechanisms underlying the therapeutic effects of PDGF on dentin‐pulp complex regeneration are still unclear. In this study, we tested the effect of PDGF‐BB on dentin‐pulp tissue regeneration by establishing PDGF‐BB gene‐modified human dental pulp stem cells (hDPSCs) using a lentivirus. Our results showed that PDGF‐BB can significantly enhance hDPSC proliferation and odontoblastic differentiation. Furthermore, PDGF‐BB and vascular endothelial growth factor (VEGF) secreted by hDPSCs enhanced angiogenesis. The chemoattractive effect of PDGF‐BB on hDPSCs was also confirmed using a Transwell chemotactic migration model. We further determined that PDGF‐BB facilitates hDPSCs migration via the activation of the phosphatidylinositol 3 kinase (PI3K)/Akt signaling pathway. In vivo, CM‐DiI‐labeled hDPSCs were injected subcutaneously into mice, and our results showed that more labeled cells were recruited to the sites implanted with calcium phosphate cement scaffolds containing PDGF‐BB gene‐modified hDPSCs. Finally, the tissue‐engineered complexes were implanted subcutaneously in mice for 12 weeks, the Lenti‐PDGF group generated more dentin‐like mineralized tissue which showed positive staining for the DSPP protein, similar to tooth dentin tissue, and was surrounded by highly vascularized dental pulp‐like connective tissue. Taken together, our data demonstrated that the PDGF‐BB possesses a powerful function in prompting stem cell‐based dentin‐pulp tissue regeneration. Stem Cells Translational Medicine 2017;6:2126–2134 Platelet‐derived growth factor‐BB through enhancing human dental pulp stem cells (hDPSC) proliferation, odontogenic differentiation, angiogenesis, and also facilitating stem cell homing to promote hDPSC‐mediated dentin‐pulp complex regeneration.

Background The aim of this study was to evaluate the effect of different endodontic access cavity designs on biomechanical properties of endodontically treated maxillary premolars under various static loads by finite element analysis method. Methods Based on cone beam computed tomography data of maxillary first premolar, the models of endodontically treated teeth with traditional access cavity (TEC-I), traditional access cavity with Class-II mesio-occlusal cavity design (TEC-II), conventional access cavity (CEC), ninja access cavity (NEC), caries-driven access cavity (Cd-EC), buccal access cavity (BEC) and bucco-occlusal access cavity (BOEC). Three different static loads which were single-point vertical load (Static I), multi-point vertical load (Static II) and multi-point oblique load (Static III) were applied. The stress distribution and maximum Von Misses stress values were recorded. Results For the enamel surface, the stress concentration was seen around the central fossa in Static I, on the marginal edge and palatal tubercle in Static II, and on the palatal cusp tip in Static III loads. For the dentin surface, the stress concentration was observed on pericervical area and buccal root surface in Static I, on all around the root surface in Static II, and on buccal and palatal root surfaces and furcation area in Static III loads. While the minimum stress distribution was detected in control group, followed by NEC and CEC designs, the maximum stress distribution was generally monitored in Cd-EC and TEC-II cavity designs. Conclusion The increased tissue loss in maxillary premolars due to endodontic access cavity preparation meant the higher stress distribution on the tooth surface.

This study investigated the interplay between Hippo-YAP and β-catenin signaling in regulating odontogenic differentiation of human dental pulp stem cells (DPSCs) and explored its potential implications for dentin-pulp regeneration. Using lentivirus-mediated YAP overexpression/silencing, β-catenin siRNA knockdown, and pharmacological Wnt inhibition (via WIF-1), we assessed DPSC proliferation, migration, mineralization, and molecular markers (via qRT-PCR, immunofluorescence). In vivo validation employed subcutaneous transplantation of DPSC-seeded scaffolds in immunocompromised mice. YAP activation enhanced DPSC proliferation (1.44-fold), migration (1.39-fold), invasion (1.54-fold), and differentiation, as evidenced by elevated ALP activity (1.46-fold) and mineralization (1.36-fold). We observed transcriptional upregulation of odontogenic markers (RUNX2, DSPP, DMP1, OCN, ALP) and Wnt pathway components (β-catenin, Cyclin D1, c-Myc). Immunofluorescence revealed coordinated YAP and β-catenin expression patterns during differentiation. β-catenin silencing or Wnt inhibition abolished YAP-mediated functional enhancements and simultaneously suppressed YAP expression, partially confirming bidirectional regulation. In vivo, YAP-overexpressing DPSCs exhibited 1.27- to 1.62-fold induction of dentin-specific markers and β-catenin, whereas YAP silencing impaired these markers expression. Our findings demonstrate that coordinated YAP and β-catenin signaling drives DPSC odontogenesis, with potential implications for dentin regeneration. Although reciprocal regulation is evident, direct molecular interactions require further validation.

The goal of this study was to establish mini-swine as a large animal model for stem cell-based pulp regeneration studies. Swine dental pulp stem cells (sDPSCs) were isolated from mini-swine and characterized in vitro . For in vivo studies, we first employed both ectopic and semi-orthotopic study models using severe combined immunodeficiency mice. One is hydroxyapatite-tricalcium phosphate (HA/TCP) model for pulp-dentin complex formation, and the other is tooth fragment model for complete pulp regeneration with new dentin depositing along the canal walls. We found that sDPSCs are similar to their human counterparts exhibiting mesenchymal stem cell characteristics with ability to form colony forming unit-fibroblastic and odontogenic differentiation potential. sDPSCs formed pulp-dentin complex in the HA/TCP model and showed pulp regeneration capacity in the tooth fragment model. We then tested orthotopic pulp regeneration on mini-swine including the use of multi-rooted teeth. Using autologous sDPSCs carried by hydrogel and transplanted into the mini-swine root canal space, we observed regeneration of vascularized pulp-like tissue with a layer of newly deposited dentin-like (rD) tissue or osteodentin along the canal walls. In some cases, dentin bridge-like structure was observed. Immunohistochemical analysis detected the expression of nestin, dentin sialophosphoprotein, dentin matrix protein 1, and bone sialoprotein in odontoblast-like cells lining against the produced rD. We also tested the use of allogeneic sDPSCs for the same procedures. Similar findings were observed in allogeneic transplantation. This study is the first to show an establishment of mini-swine as a suitable large animal model utilizing multi-rooted teeth for further cell-based pulp regeneration studies.

Background This study evaluated the antibacterial efficiency and ability of propolis to promote regeneration of immature permanent non-vital dogs’ teeth. Methods Ninety six immature permanent premolars teeth in 6 mongrel dogs were divided randomly into: experimental teeth ( N  = 72) and control teeth ( N  = 24). Periapical pathosis was induced in all experimental and positive control teeth. Experimental teeth were classified according to the used intra-canal medication into: group I ( N  = 36), propolis paste was used and group II (N = 36), triple antibiotic paste (TAP) was used. Bacteriologic samplings were collected before and after exposure to intra-canal medicaments. After the disinfection period (3 weeks), revascularization was induced in all experimental teeth. Each group was subdivided according to the root canal orifice plug into: subgroup A ( N  = 18), propolis paste was used and subgroup B (N = 18), mineral trioxide aggregates (MTA) was used. Each subgroup was further subdivided according to the evaluation period into 3 subdivisions (6 teeth each): subdivision 1; after 2 weeks, subdivision 2; after one month and subdivision 3; after 2 months. Positive control group had 12 teeth with induced untreated periapical pathosis. Negative control group had 12 untouched sound teeth. All teeth were evaluated with radiography and histology. The bacteriologic and radiographic data were analyzed using repeated measures ANOVA and post-hoc Tukey tests. The histologic data were analyzed using Kruskal-Wallis test, Mann-Whitney U test with Bonferroni’s adjustment and Chi-square test. The significance level was set at P  ≤ .05. Results There was no significant difference in the antibacterial effectiveness between TAP and propolis groups ( P  > .05). In all subdivisions, there was no significant difference between the experimental groups in terms of increase in root length and dentin thickness, decrease in apical closure, new hard tissue formation, vital tissue formation inside the pulp canal and apical closure scores ( P  > .05). Conclusion Propolis can be comparable with TAP as a disinfection treatment option in regenerative endodontic. As a root canal orifice plug after revascularization of necrotic immature permanent teeth in dogs, propolis induces a progressive increase in root length and dentin thickness and a decrease in apical diameter similar to those of MTA.

MicroRNA (miR)-200c enhances osteogenesis, modulates inflammation, and participates in dentin development. This study was to investigate the beneficial potential of miR-200c in vital pulp therapy (VPT) by mitigating pulpitis and promoting dentin regeneration. We explored the miR-200c variations in inflamed pulp tissues from patients with symptomatic irreversible pulpitis and primary human dental pulp-derived cells (DPCs) challenged with P.g. lipopolysaccharide (Pg-LPS). We further assessed the functions of overexpression of miR-200c on odontogenic differentiation, pulpal inflammation, and dentin regeneration in vitro and in vivo. Our findings revealed a noteworthy downregulation of miR-200c expression in inflamed pulp tissues and primary human DPCs. Through the overexpression of miR-200c via transfecting plasmid DNA (pDNA), we observed a substantial downregulation of proinflammatory cytokines interleukin (IL)-6 and IL-8 in human DPCs. Furthermore, this overexpression significantly enhanced the transcript and protein levels of odontogenic differentiation markers, including Runt-related transcription factor (Runx)2, osteocalcin (OCN), dentin matrix protein (DMP)1, and dentin sialophosphoprotein (DSPP). In a rat model of pulpitis induced by Pg-LPS, we demonstrated notable benefits by local application of pDNA encoding miR-200c delivered by CaCO3-based nanoparticles to reduce pulpal inflammation and promote dentin formation. These results underscore the significant impact of locally applied miR-200c in modulating pulpal inflammation and facilitating dentin repair, showcasing its ability to improve VPT outcomes.