Dentin Formation Research Articles

Experimental study of dexamethasone-loaded hollow hydroxyapatite microspheres applied to direct pulp capping of rat molars.

Dexamethasone (DEX) exerts anti-inflammatory and osteogenic effects. Hydroxyapatite is commonly used in bone repair due to its osteoconductivity, osseointegration, and osteogenesis induction. Hollow hydroxyapatite (HHAM) is often used as a drug carrier. This study aimed to investigate the histological responses of exposed dental pulp when dexamethasone-loaded nanohydroxyapatite microspheres (DHHAM) were used as a direct capping agent. Cavities were created in the left maxillary first molar of Wistar rats and filled with Dycal, HHAM, and DHHAM. No drug was administered to the control group. The rats were sacrificed at 1, 2, and 4 weeks after the procedure. The molars were extracted for fixation, demineralization, dehydration, embedding, and sectioning. H&E staining was performed to detect the formation of reparative dentin. H&E and CD45 immunohistochemical staining were performed to detect pulp inflammation. Immunohistochemical staining was performed to assess the expressions of dentin matrix protein 1 (DMP-1), interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-1β. The results of H&E and CD45 immunohistochemical staining showed that the degree of inflammation in the DHHAM group was less than that in the Control and HHAM groups at 1, 2, and 4 weeks after capping of the rat molar teeth (p<0.01). The H&E staining showed that the percentage of reparative dentin formed in the DHHAM group was higher than that in the Control, HHAM (p<0.001), and Dycal groups (p<0.01) at 1 and 2 weeks, and was significantly higher than that in the Control group (p<0.001) and the HHAM group (p<0.01) at 4 weeks. The immunohistochemical staining showed a lower range and intensity of expression of IL-1β, IL-6, and TNF-α and high expression levels of DMP-1 in the DHHAM group at 1, 2, and 4 weeks after pulp capping relative to the Control group. DHHAM significantly inhibited the progression of inflammation and promoted reparative dentin formation.

Development of a new universal adhesive containing CPNE7-derived peptide and its potential role in reducing postoperative sensitivity.

Post-operative sensitivity (POS) is the most common clinical dental complaint after tooth preparation and resin-based composite restoration. In our previous study, copine 7 (CPNE7) and CPNE7-derived peptide (CPNE7-DP) induced in vitro odontoblast differentiation and in vivo dentin formation. Here, we incorporated CPNE7-DP into All-Bond Universal (ABU) adhesive, developing ABU/CPNE7-DP. This study aimed to investigate the possibility of reducing POS using ABU/CPNE7-DP. We first determined the stability of CPNE7-DP under low pH. Furthermore, we evaluated its dentinal tubule penetration, in vitro odontogenic differentiation potential, in vivo tertiary dentin formation and its effects on bonding performance. CPNE7-DP was stable at pH 1.2, even lower than ABU's pH of 3.2. ABU/CPNE7-DP can penetrate dentinal tubules, stimulate odontoblast differentiation in vitro and generate tertiary dentin with tubular structure in vivo without interfering with bonding performance. Therefore, ABU/CPNE7-DP may serve as a novel bioactive adhesive for reducing POS.

Functional evaluation of mineral trioxide aggregate cement with choline dihydrogen phosphate.

To improve the cytocompatibility of mineral trioxide aggregate (MTA) cement and its ability for reparative dentin formation, the effect of adding choline dihydrogen phosphate (CDHP), which is reported to be biocompatible, to MTA cement was investigated. The L929 cell proliferation showed that the addition of CDHP improved cell viability. The addition of CDHP shortened the setting time of MTA cement, with a significant decrease in consistency above 0.4 g/mL. Diametral tensile strength of the set cement was improved by the addition of 0.4 g/mL CDHP. Solubility was judged to be within the range of clinical application. The spontaneous precipitation of low crystalline hydroxyapatite was examined by immersing the set cement in phosphate buffer saline, and it was found that the ability of the cement with 0.4 g/mL of CDHP was significantly improved compared with that of the cement without CDHP.

Reparative Dentin Formation Following Dental Pulp Capping is Mediated by TNFR1 In Vivo

IntroductionTumor necrosis factor (TNF)-α is a pro-inflammatory cytokine that promotes biomineralization in vitro in dental pulp cells. However, the role of TNF-α-TNF receptor 1 (TNFR1) signaling in reparative dentin formation and related inflammatory pathways is not known. Therefore, the aim of this study was to evaluate the role of the TNF-α-TNFR1 axis in dental pulp repair following pulp capping in vivo. MethodsDental pulp repair response of genetically deficient TNF-α receptor-1 mice (TNFR1−/−; n = 20) was compared with that of C57Bl6 mice (wild type [WT]; n = 20). Pulp capping was performed with mineral trioxide aggregate on the mandibular first molars of mice. After 7 and 70 days, tissues were collected and stained with hematoxylin and eosin for histopathological and histometric evaluation, and assessed by the Brown and Brenn methods for histomicrobiological analysis and by immunohistochemistry to localize TNF-α, Runt-related transcription factor 2, Dentin Sialoprotein (DSP) and Osteopontin (OPN) expression. ResultsCompared with WT mice, TNFR1−/− mice showed significantly decreased reparative dentin formation with a lower mineralized tissue area (P < .0001). Unlike WT mice, TNFR1−/− mice also exhibited significant dental pulp necrosis, neutrophil recruitment, and apical periodontitis formation (P < .0001) without bacterial tissue invasion. TNFR1−/− animals further exhibited decreased TNF-α, DSP, and OPN expression (P < .0001), whereas Runt-related transcription factor 2 expression was unchanged (P > .05). ConclusionThe TNF-α-TNFR1 axis is involved in reparative dentin formation following dental pulp capping in vivo. Genetic ablation of TNFR1 modified the inflammatory process and inhibited the expression of the DSP and OPN mineralization proteins, which culminated in dental pulp necrosis and development of apical periodontitis.

Inflammatory Response and Odontogenic Differentiation of Inflamed Dental Pulp Treated with Different Pulp Capping Materials: An In Vivo Study.

Previous studies have evaluated the pulpal responses to calcium silicate cements (CSCs) on normal dental pulp, but investigations on the effects of CSCs on inflamed pulp are limited. This study aimed to test the inflammatory response and odontogenic differentiation of inflamed rat dental pulp after direct pulp capping with CSCs. Wistar rat molars pulps were exposed for 48 hours to induce inflammation and then capped with ProRoot MTA (Dentsply, Tulsa, OK, USA), Biodentine (Septodont, Saint-Maur-des-Fossés, France), RetroMTA (Bio MTA, Seoul, Korea) and Dycal (Dentsply Caulk, Milford, DE, USA). The degree of pulpal inflammation and hard tissue formation was evaluated by histological analysis. Immunofluorescence staining for interleukin (IL)-6, osteocalcin (OCN), and runt-related transcription factor 2 (RUNX2) was also performed. After 4 weeks, complete recovery from inflammation was evident in 22%, 37.5%, 10%, and none of the ProRoot MTA, Biodentine, RetroMTA and Dycal samples, respectively. Heavy hard tissue deposition as a continuous hard tissue bridge was observed in 77.8%, 75%, 70%, and 60% of the ProRoot MTA, Biodentine, RetroMTA, and Dycal samples, respectively. IL-6, OCN, and RUNX2 were detected in all materials, mainly adjacent to areas of inflammation and reparative dentine formation. At 1, 2, and 4 weeks, significant differences were not observed between the inflammation and hard tissue formation scores of the four material groups (P > .05). In this study, pulpal inflammation was still present in most specimens at 4 weeks after pulp capping and a significant number of samples showed incomplete and discontinuous dentine bridge formation. The results of this study suggest that initial inflammatory conditions of the pulp may risk the prognosis of teeth treated with CSCs.

Re-understanding the role of enamel matrix proteins in periodontal regeneration

Enamel matrix proteins (EMP) are deposited on the surface of developing roots before dentin formation and may play a role in osteogenesis. Amelogenins (Am) are the main and active component in EMPs. Studies had showed great clinical values of EMPs in periodontal regenerative treatment and other fields. By affecting the expression of growth factors and inflammatory factors, EMPs could act on various periodontal regeneration-related cells to promote angiogenesis, anti-inflammation, bacteriostasis and tissue healing, achieving the clinical effect of periodontal tissue regeneration (newly generated cements and alveolar bones as well as functionally penetrated periodontal ligament). EMPs alone or combined with bone graft material and barrier can be used for regenerative surgical treatment in intrabony defects and degree Ⅱ furcation-involved at maxillary buccal or mandibular teeth. EMPs can also be adjunctively used to treat recession type 1 or 2 gingival recessions, forming periodontal regeneration on the exposed root surface. Through a comprehensive understanding of the principle and current clinical application of EMPs on periodontal regeneration, we can look forward to their future development. The development of recombinant human amelogenin to replace animal-derived EMPs through bioengineering technologies, the study of the clinical application of EMPs combined with other collagen biomaterials, and the specific application of EMPs in severe soft and hard periodontal tissue defects and peri-implant lesions are all important development directions of future EMPs-related researches.

The potency of propolis extract as anti-inflammatory agent for stimulation of reparative dentin formation

Background: As an effort to treat a deep caries lesion with a diagnosis of reversible pulpitis, one of the treatment options is pulp capping. For decades, calcium hydroxide has been considered the most acceptable pulp capping material and has been routinely used in dental practice, but it also has some weakness. To overcome that, alternative materials are needed that can provide a better effect. Recently, a lot of research has been done using natural ingredients, including Propolis. Propolis has been known to have strong antimicrobial and anti inflammatory properties. Therefore, it is necessary to conduct a deeper study regarding the potency of propolis extract as an anti inflammatory agent for the stimulation of reparative dentin formation so that it can be considered to be used as a pulp capping material. Objective: The aim of this literature review is to highlight the potency of propolis extract as anti inflammatory agent in the natural stimulation of reparative dentin formation. Methods: The search strategy consist of an electronic research using databases such as PubMed, Google Scholar, Science Direct, dan Springer Link for studies published from 2003 to 2021 regarding the potency of propolis extract as anti inflammatory agent for stimulation of reparative dentin formation, including review articles and research articles. Results: Propolis and its constituents have been proven to be used as a potent natural anti inflammatory, it also considered to have the ability to promote reparative dentin formation. However, there are some literatures stated that reparative dentin does not form with the application of propolis, and the causes may vary. Conclusion: Propolis extract has a potency as an anti inflammatory agent in dental pulp inflammation by inhibiting TNFα expression, and increasing TGF-β1 expression, as well as its potency in stimulating the formation of reparative dentin. Based on this review, further studies are needed.

GATA4 inhibits odontoblastic differentiation of dental pulp stem cells through targeting IGFBP3

ObjectiveThe odontogenic differentiation of human dental pulp stem cells (HDPSCs) is associated with reparative dentinogenesis. Transcription factor GATA binding protein 4 (GATA4) is proved to be essential for osteoblast differentiation and bone remodeling. This study clarified the function of GATA4 in HDPSCs odontoblast differentiation. MethodsThe change in GATA4 expression during reparative dentin formation was detected by immunohistochemistry staining. The expression of GATA4 during HDPSCs odontoblastic differentiation was detected by western blot and quantitative polymerase chain reaction. The effect of GATA4 on odontoblast differentiation was investigated following overexpression lentivirus transfection. RNA sequencing, dual luciferase assay and chromatin immunoprecipitation (CHIP) were conducted to verify downstream targets of GATA4. GATA4 overexpression lentivirus and small interference RNA targeting IGFBP3 were co-transfected to investigate the regulatory mechanism of GATA4. ResultsUpregulated GATA4 was observed during reparative dentin formation in vivo and the odontoblastic differentiation of HDPSCs in vitro. GATA4 overexpression suppressed the odontoblastic potential of HDPSCs, demonstrated by decreased alkaline phosphatase activity (p < 0.0001), mineralized nodules formation (p < 0.01), and odonto/osteogenic differentiation markers levels (p < 0.05). RNA sequencing revealed IGFBP3 was a potential target of GATA4. CHIP and dual luciferase assays identified GATA4 could activate IGFBP3 transcription. Additionally, IGFBP3 knockdown recovered the odontoblastic differentiation defect caused by GATA4 overexpression (p < 0.05). ConclusionsGATA4 inhibited odontoblastic differentiation of HDPSCs via activating the transcriptional activity of IGFBP3, identifying its promising role in regulating HDPSCs odontoblast differentiation and reparative dentinogenesis.

Fam20C overexpression in odontoblasts regulates dentin formation and odontoblast differentiation.

FAM20C phosphorylates secretory proteins at S-x-E/pS motifs, and previous studies of Fam20C-dificient mice revealed that FAM20C played essential roles in bone and tooth formation. Inactivation of FAM20C in mice led to hypophosphatemia that masks direct effect of FAM20C in these tissues, and consequently the direct role of FAM20C remains unknown. Our previous study reported that osteoblast/odontoblast-specific Fam20C transgenic (Fam20C-Tg) mice had normal serum phosphate levels and that osteoblastic FAM20C-mediated phosphorylation regulated bone formation and resorption. Here, we investigated the direct role of FAM20C in dentin using Fam20C-Tg mice. The tooth of Fam20C-Tg mice contained numerous highly phosphorylated proteins, including SIBLINGs, compared to that of wild-type mice. In Fam20C-Tg mice, coronal dentin volume decreased and mineral density unchanged at early age, while the volume unchanged and the mineral density elevated at maturity. In these mice, radicular dentin volume and mineral density decreased at all ages, and histologically, the radicular dentin had wider predentin and abnormal apical-side dentin with embedded cells and argyrophilic canaliculi. Immunohistochemical analyses revealed that abnormal apical-side dentin had bone and dentin matrix properties accompanied with osteoblast-lineage cells. Further, in Fam20C-Tg mice, DSPP content which is important for dentin formation, was reduced in dentin, especially radicular dentin, which might lead to defects mainly in radicular dentin. Renal subcapsular transplantations of tooth germ revealed that newly formed radicular dentin replicated apical abnormal dentin of Fam20C-Tg mice, corroborating that FAM20C overexpression indeed caused the abnormal dentin. Our findings indicate that odontoblastic FAM20C-mediated phosphorylation in the tooth regulates dentin formation and odontoblast differentiation.

Reparative dentin formation as a possible factor influencing the penetrability of dentin in human teeth with apical periodontitis: an ex vivo study

BackgroundThere is still a lack of knowledge regarding the permeability and configuration of infected root dentin. The aim of this ex vivo study was to compare the dentin penetrability of healthy teeth and necrotic teeth with apical periodontitis by evaluating the penetration of sodium hypochlorite (NaOCl) and to analyze the histopathological features of root dentin.MethodsForty-eight molars were collected and divided into two groups. The clinical diagnosis for one group was pulp necrosis with apical periodontitis and the pulp and periapex were normal in the other group. Forty-eight straight roots were divided into two groups: infected and healthy. First, all root canals were stained with 2% methylene blue to visualize penetration after standard root canal instrumentation and irrigation. Transverse sections were obtained, and the dye penetration parameters were measured. The cross sections were processed to 20–30 μm and stained with hematoxylin and eosin for observation of the histopathological changes in the root dentin.ResultsThe maximum penetration depth, median penetration depth and penetration percentage of NaOCl solutions, in infected root canals were significantly lower than those in healthy root canals. The histopathological analysis showed that the frequency of reparative dentin formation in infected root canals was significantly greater than that in healthy root canals.ConclusionsThe dentin penetrability of teeth with necrotic teeth and apical periodontitis was more superficial during root canal irrigation than that of healthy teeth. The histopathological changes in infected radicular dentin, namely the formation of reparative dentin, might be associated with the lower permeability of dentin tubules in human teeth with apical periodontitis.

Multimodal Imaging of Dental Pulp Healing Patterns Following Tooth Autotransplantation and Regenerative Endodontic Treatment

IntroductionUnderstanding the healing process of dental pulp after tooth autotransplantation (TAT) and regenerative endodontic treatment (RET) of immature teeth is important both clinically and scientifically. This study aimed to characterize the pattern of dental pulp healing in human teeth that underwent TAT and RET using state-of-the-art imaging techniques. Materials and MethodsThis study examined 4 human teeth, 2 premolars that underwent TAT, and 2 central incisors that received RET. The premolars were extracted after 1 year (case 1) and 2 years (case 2) due to ankylosis, while the central incisors were extracted after 3 years (cases 3 and 4) for orthodontic reasons. Nanofocus x-ray computed tomography was used to image the samples before being processed for histological and immunohistochemical analysis. Laser scanning confocal second harmonic generation imaging (SHG) was used to examine the patterns of collagen deposition. A maturity-matched premolar was included as a negative control for the histological and SHG analysis. ResultsAnalysis of the 4 cases revealed different patterns of dental pulp healing. Similarities were observed in the progressive obliteration of the root canal space. However, a striking loss of typical pulpal architecture was observed in the TAT cases, while a pulp-like tissue was observed in one of the RET cases. Odontoblast-like cells were observed in cases 1 and 3. ConclusionsThis study provided insights into the patterns of dental pulp healing after TAT and RET. The SHG imaging sheds light on the patterns of collagen deposition during reparative dentin formation.

Dentoalveolar Alterations in an Adenine-Induced Chronic Kidney Disease Mouse Model.

Chronic kidney disease (CKD) is characterized by kidney damage and loss of renal function. CKD mineral and bone disorder (CKD-MBD) describes the dysregulation of mineral homeostasis, including hyperphosphatemia and elevated parathyroid hormone (PTH) secretion, skeletal abnormalities, and vascular calcification. CKD-MBD impacts the oral cavity, with effects including salivary gland dysfunction, enamel hypoplasia and damage, increased dentin formation, decreased pulp volume, pulp calcifications, and altered jaw bones, contributing to clinical manifestations of periodontal disease and tooth loss. Underlying mechanisms are not fully understood, and CKD mouse models commonly require invasive procedures with high rates of infection and mortality. We aimed to characterize the dentoalveolar effects of an adenine diet (AD)-induced CKD (AD-CKD) mouse model. Eight-week-old C57BL/6J mice were provided either a normal phosphorus diet control (CTR) or adenine and high-phosphorus diet CKD to induce kidney failure. Mice were euthanized at 15 weeks old, and mandibles were collected for micro-computed tomography and histology. CKD mice exhibited kidney failure, hyperphosphatemia, and hyperparathyroidism in association with porous cortical bone in femurs. CKD mice showed a 30% decrease in molar enamel volume compared to CTR mice. Enamel wear was associated with reduced ductal components, ectopic calcifications, and altered osteopontin (OPN) deposition in submandibular salivary glands of CKD mice. Molar cusps in CKD mice were flattened, exposing dentin. Molar dentin/cementum volume increased 7% in CKD mice and pulp volume decreased. Histology revealed excessive reactionary dentin and altered pulp-dentin extracellular matrix proteins, including increased OPN. Mandibular bone volume fraction decreased 12% and bone mineral density decreased 9% in CKD versus CTR mice. Alveolar bone in CKD mice exhibited increased tissue-nonspecific alkaline phosphatase localization, OPN deposition, and greater osteoclast numbers. AD-CKD recapitulated key aspects reported in CKD patients and revealed new insights into CKD-associated oral defects. This model has potential for studying mechanisms of dentoalveolar defects or therapeutic interventions. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

The Combined Effects of Hydraulic Calcium Silicate Cement and Enamel Matrix Derivative Regarding Osteogenic and Dentinogenic Differentiation on Human Dental Pulp Stem Cells.

The ideal treatment option for immature necrotic permanent teeth is regeneration of the pulp-dentin complex. Mineral trioxide aggregate (MTA), the conventional cement used for regenerative endodontic procedures, induces hard tissue repair. Various hydraulic calcium silicate cements (HCSCs) and enamel matrix derivative (EMD) also promote osteoblast proliferation. The purpose of the present study was to determine the osteogenic and dentinogenic potential of commercially distributed MTA and HCSCs when applied in combination with Emdogain gel on human dental pulp stem cells (hDPSCs). The presence of Emdogain resulted in greater cell viability, and higher alkaline phosphatase activity was detected in the Emdogain-supplemented groups in the early days of cell culture. On qRT-PCR, the groups treated, respectively, with Biodentine and Endocem MTA Premixed in the presence of Emdogain showed an increased expression of the dentin formation marker DSPP, and the group treated with Endocem MTA Premixed in the presence of Emdogain showed an upregulated expression of the bone formation markers OSX and RUNX2. In an Alizarin Red-S staining assay, all of the experimental groups exhibited a greater formation of calcium nodules when treated in combination with Emdogain. Overall, the cytotoxicity and osteogenic/odontogenic potential of HCSCs were similar to that of ProRoot MTA. The addition of the EMD increased the osteogenic and dentinogenic differentiation markers.

Localization of senescent cells under cavity preparations in rats and restoration of reparative dentin formation by senolytics.

Reparative dentin formed by dental cavity preparation (DCP) is frequently used in clinical operations and plays a pivotal role in pulp protection. Recent reports have shown that senescent cells induced by various stressors aggravate many diseases. They can be treated using senolytics, which are drugs that selectively eliminate senescent cells. However, the association between DCP, senescent cells, and senolytics remains unclear. In this study, we established a rat model of DCP and analyzed the spatiotemporal localization of senescent cells in the pulp. The results showed that p21- and p16-positive senescent cells appeared mostly around the pulp horn (PH) under DCP. Furthermore, administration of senolytics (dasatinib and quercetin) successfully eliminated these senescent cells, thereby restoring the volume of reparative dentin formation. These data indicate that senescent cells induced by DCP may hamper the formation of reparative dentin. Senescent cells may be targets for the development of new restorative dentistry therapies.

Functional Expression of IP, 5-HT4, D1, A2A, and VIP Receptors in Human Odontoblast Cell Line.

Odontoblasts are involved in sensory generation as sensory receptor cells and in dentin formation. We previously reported that an increase in intracellular cAMP levels by cannabinoid 1 receptor activation induces Ca2+ influx via transient receptor potential vanilloid subfamily member 1 channels in odontoblasts, indicating that intracellular cAMP/Ca2+ signal coupling is involved in dentinal pain generation and reactionary dentin formation. Here, intracellular cAMP dynamics in cultured human odontoblasts were investigated to understand the detailed expression patterns of the intracellular cAMP signaling pathway activated by the Gs protein-coupled receptor and to clarify its role in cellular functions. The presence of plasma membrane Gαs as well as prostaglandin I2 (IP), 5-hydroxytryptamine 5-HT4 (5-HT4), dopamine D1 (D1), adenosine A2A (A2A), and vasoactive intestinal polypeptide (VIP) receptor immunoreactivity was observed in human odontoblasts. In the presence of extracellular Ca2+, the application of agonists for the IP (beraprost), 5-HT4 (BIMU8), D1 (SKF83959), A2A (PSB0777), and VIP (VIP) receptors increased intracellular cAMP levels. This increase in cAMP levels was inhibited by the application of the adenylyl cyclase (AC) inhibitor SQ22536 and each receptor antagonist, dose-dependently. These results suggested that odontoblasts express Gs protein-coupled IP, 5-HT4, D1, A2A, and VIP receptors. In addition, activation of these receptors increased intracellular cAMP levels by activating AC in odontoblasts.

Axin2-CreERT2 mediated knockout of bone morphogenetic protein receptor type 1A caused abnormal secondary dentine and altered cell fate of Axin2-expressing odontogenic cells.

Inducing odontogenic differentiation and tubular dentine formation is extremely important in dentine repair and tooth regeneration. Bone morphogenic proteins (BMPs) signalling plays a critical role in dentine development and tertiary dentine formation, whilst how BMPR1A-mediated signalling affects odontoblastic differentiation of Axin2-expressing (Axin2+ ) odontogenic cells and tubular dentine formation remains largely unknown. This study aims to reveal the cellular and molecular mechanisms involved in the formation of secondary dentine. Axin2lacZ/+ mice harvested at post-natal 21 (P21) were used to map Axin2+ mesenchymal cells. Axin2CreERT2/+ ; R26RtdTomato/+ mice and Axin2CreERT2/+ ; R26RDTA/+ ; R26RtdTomato/+ mice were generated to observe the tempo-spatial distribution pattern of Axin2-lineage cells and the effect of ablation of Axin2+ cells on dentinogenesis, respectively. A loss-of-function model was established with Axin2CreERT2/+ ; Bmpr1afl/fl ; R26RtdTomato/+ (cKO) mice to study the role of BMP signalling in regulating Axin2+ cells. Micro-computed tomography, histologic and immunostainings, and other approaches were used to examine biological functions, including dentine formation, mineralization and cell differentiation in cKO mice. The results showed rich expression of Axin2 in odontoblasts at P21. Lineage tracing assay confirmed the wide distribution of Axin2 lineage cells in odontoblast layer and dental pulp during secondary dentine formation (P23 to P56), suggesting that Axin2+ cells are important cell source of primary odontoblasts. Ablation of Axin2+ cells (DTA mice) significantly impaired secondary dentine formation characterized with notably reduced dentine thickness (Mean of control: 54.11 μm, Mean of DTA: 27.79 μm, p = .0101). Furthermore, malformed osteo-dentine replaced the tubular secondary dentine in the absence of Bmpr1a with irregular cell morphology, abnormal cellular process formation and lack of cell-cell tight conjunction. Remarkably increased expression of osteogenic markers like Runx2 and DMP1 was detected, whilst DSP expression was observed in a dispersed manner, indicating an impaired odontogenic cell fate and failure in producing tubular dentine in cKO mice. Axin2+ cells are a critical population of primary odontoblasts which contribute to tubular secondary dentine formation, and BMP signalling pathway plays a vital role in maintaining the odontogenic fate of Axin2+ cells.

AAV6-Mediated Gene Therapy Prevents Developmental Dentin Defects in a Dentinogenesis Imperfecta Type Ⅲ Mouse Model.

Dentin is a major type of hard tissue of teeth and plays essential roles for normal tooth function. Odontoblasts are responsible for dentin formation. Mutations or deficiency in various genes affect the differentiation of odontoblasts, leading to irreversible dentin developmental defects in animals and humans. Whether such dentin defects can be reversed by gene therapy for odontoblasts remains unknown. In this study, we compare the infection efficiencies of six commonly used adeno-associated virus (AAV) serotypes (AAV1, AAV5, AAV6, AAV8, AAV9, and AAVDJ) in cultured mouse odontoblast-like cells (OLCs). We show that AAV6 serotype infects OLCs with the highest efficiency among the six AAVs. Two cellular receptors, which are able to recognize AAV6, AAV receptor (AAVR), and epidermal growth factor receptor (EGFR), are strongly expressed in the odontoblast layer of mouse teeth. After local administration to mouse molars, AAV6 infects the odontoblast layer with high efficiency. Furthermore, AAV6-Mdm2 was successfully delivered to teeth and prevents the defects in odontoblast differentiation and dentin formation in Mdm2 conditional knockout mice (a mouse model of dentinogenesis imperfecta type Ⅲ). These results suggest that AAV6 can serve as a reliable and efficient vehicle for gene delivery to odontoblasts through local injection. In addition, human OLCs were also successfully infected by AAV6 with high efficiency, and both AAVR and EGFR are strongly expressed in the odontoblast layer of extracted human developing teeth. These findings suggest that AAV6-mediated gene therapy through local injection may be a promising treatment approach for hereditary dentin disorders in humans.

Potential Combination of Acemannan Sponge and Calcium Phosphate Cement-Calcium Sulfate Hemihydrate (CPC-CSH) as Direct Pulp Capping Alternative Materials for Reparative Dentin Formation

Abstract Background Health problem that affects hard tissues of the teeth is dental caries, which is experienced by around 2.3 billion people in the world, with prevalence in Indonesia reaching 88.8. Direct pulp capping (DPC) is a vital pulp therapy used to maintain pulp vitality. Calcium hydroxide (Ca(OH)2) is the gold standard pulp capping material, but has poor adhesion to dentin and mechanical properties, bacterial infiltration, formation of tunnel defects in the pulp resorption, and dentin bridge. Therefore, it is necessary to develop alternative therapy, namely, a combination of acemannan sponge and calcium phosphate cement (CPC)-calcium sulfate hemihydrate (CSH) for reparative dentin formation. Purpose This article describes the potential combination of acemannan sponge and CPC-CSH as DPC alternative materials for reparative dentin formation. Reviews Acemannan extracted from aloe vera exhibits anti-inflammatory, antimicrobial, and cytocompatibility properties. As DPC material, acemannan induces pulp proliferation and differentiation to osteoblast-like, growth factor synthesis, and promotes reparative dentin formation. However, acemannan sponge is radiolucent, allowing misinterpretation between pulp and acemannan sponge. CPC can be combined with CSH to shorten the setting time. CPC-CSH is radiopaque, has good compressive strength, and biocompatibility. CPC-CSH is a calcium-based material with neutral pH that can induce the dentin bridge formation. CPC-CSH showed good bioactivity because it induces the formation of apatite which plays a significant part in dentin and pulp regeneration. Conclusion The combination of acemannan sponge and CPC-CSH has the potential as DPC alternative materials for reparative dentin formation.

Cold lasers for photobiomodulation in pulpotomy of primary molars: A short review

Photobiomodulation with diode lasers of 660 and 810 - 980 nm is used for the proliferation of fibroblasts and to enhance the healing of oral lesions or surgical wounds. It has the potential to stimulate the formation of reparative dentin and preserve pulp vitality. Photobiomodulation uses low-level laser therapy (LLLT) which works on the principle of supplying direct bio-stimulative light energy to the cells. Based on these characteristics, numerous studies are conducted on photobiomodulation with a diode laser for pulpotomy in primary molars. This review article aims to provide data to clinicians regarding varying parameters used for photobiomodulation in pulpotomy and their clinical outcomes in primary molars.

CHIP inhibits odontoblast differentiation through promoting DLX3 polyubiquitylation and degradation.

Dentin is the major hard tissue of teeth formed by differentiated odontoblasts. How odontoblast differentiation is regulated remains enigmatic. Here, we report that the E3 ubiquitin ligase CHIP is highly expressed in undifferentiated dental mesenchymal cells and downregulated after differentiation of odontoblasts. Ectopic expression of CHIP inhibits odontoblastic differentiation of mouse dental papilla cells, whereas knockdown of endogenous CHIP has opposite effects. Chip (Stub1) knockout mice display increased formation of dentin and enhanced expression of odontoblast differentiation markers. Mechanistically, CHIP interacts with and induces K63 polyubiquitylation of the transcription factor DLX3, leading to its proteasomal degradation. Knockdown of DLX3 reverses the enhanced odontoblastic differentiation caused by knockdown of CHIP. These results suggest that CHIP inhibits odontoblast differentiation by targeting its tooth-specific substrate DLX3. Furthermore, our results indicate that CHIP competes with another E3 ubiquitin ligase, MDM2, that promotes odontoblast differentiation by monoubiquitylating DLX3. Our findings suggest that the two E3 ubiquitin ligases CHIP and MDM2 reciprocally regulate DLX3 activity by catalyzing distinct types of ubiquitylation, and reveal an important mechanism by which differentiation of odontoblasts is delicately regulated by divergent post-translational modifications.