Dentine-pulp tissue engineering in miniature swine teeth by set calcium silicate containing bioactive molecules

Tomographic evaluation of direct pulp capping using a novel injectable treated dentin matrix hydrogel: a 2-year randomized controlled clinical trial

OBJECTIVES

To assess clinically and radiographically the success of pulp capping procedure done in traumatically exposed permanent posterior teeth using a novel injectable treated dentin matrix hydrogel (TDMH), Biodentine, and MTA and to evaluate the formed dentin bridge under the capping materials using CBCT imaging.

MATERIALS AND METHODS

45 patients subjected to accidental traumatic pulp exposures by undergraduate dental students are allocated for this study. For each patient, a pulp capping procedure was done. TDMH was formed of TDM powder and sodium alginate to be injected and then hardened in the defect area. Patients were assigned to 3 groups: TDMH, Biodentine, and MTA, respectively, and returned to the clinic after 3, 6, 12, 18, and 24 months for clinical and radiographic examinations. Tomographic data, including thickness and density of formed dentin bridges, were evaluated at the end of the study period compared to the base line. Pulp sensitivity was evaluated throughout the study period using thermal testing and electric pulp tester.

RESULTS

During the follow-up period, all patients were asymptomatic with no clinical signs and symptoms and revealed no radiographic signs of pathosis. However, tomographic evaluation showed the tested materials to have different levels of impact on formed dentin bridges with TDMH group resulted in significantly superior dentin bridges of a higher radiodensity and thickness than Biodentine and MTA.

CONCLUSIONS

TDMH has a greater potential to induce dentin bridge formation than Biodentine and MTA under standardized conditions. Additionally, CBCT imaging was confirmed as a non-invasive and inclusive approach to evaluate the formed dentin bridges after pulp capping procedure.

CLINICAL RELEVANCE

Direct pulp capping can be done successfully with this novel injectable pulp capping material in future clinical applications.

TRIAL REGISTRATION

PACTR201901866476410.

Current evidence of tissue engineering for dentine regeneration in animal models: a systematic review

Aim: The aim of this study is to verify the type of scaffold effect on tissue engineering for dentine regeneration in animal models. Materials & methods: Strategic searches were conducted through MEDLINE/PubMed, Web of Science and Scopus databases. The studies were included with the following eligibility criteria: studies evaluating dentine regeneration, and being an in vivo study. Results: From 1392 identified potentially relevant studies, 15 fulfilled the eligibility criteria. All studies described characteristics of neoformed dentine, being that the most reported reparative dentine formation. Most of included studies presented moderate risk of bias. Conclusion: Up to date scientific evidence shows a positive trend to dentine regeneration when considering tissue engineering in animal models, regardless the type of scaffolds used.

Characterization of Odontoblast-like Cell Phenotype and Reparative Dentin Formation In Vivo: A Comprehensive Literature Review

INTRODUCTION

The primary aim was to explore the criteria used in characterization of reparative cells and mineralized matrices formed after treatment of pulp exposures, and the sequence of relative events. The secondary aim was to evaluate whether the reparative events depend on the experimental model species, age, and therapeutic intervention.

METHODS

A literature search of databases using different combinations of the key words was undertaken. Data analysis was based only on studies having histological or histochemical assessment of the pulp tissue responses. The search yielded 86 studies, 47 capping material-based and 39 bioactive application-based experiments, which provided data on morphological or functional characterization of the mineralized matrices and the associated cells.

RESULTS

In 64% of capping material-based and 72% of bioactive application-based experiments, a 2-zone mineralized matrix formation (atubular followed by tubular) was detected, whereas characterization of odontoblastic differentiation is provided in only 25.5% and 46.1% of the studies, respectively. In 93.3% of the studies showing odontoblast-like cells, differentiated cells were in association with tubular mineralized matrix formation. Analyses further showed that cell- and matrix-related outcomes do not depend on experimental model species, age, and therapeutic intervention.

CONCLUSIONS

The evidence of the reviewed scientific literature is that dental pulp cells secrete a dentin-like matrix of tubular morphology in relation to primitive forms of atubular or osteotypic mineralized matrix. Furthermore, data analysis showed that dental pulp cells express in vivo the odontoblastic phenotype, and secrete matrix in a predentin-like pattern, regardless of the model species, age, and therapeutic intervention used.

Development of a mouse model for pulp-dentin complex regeneration research: a preliminary study

Objectives

To achieve pulp-dentin complex regeneration with tissue engineering, treatment efficacies and safeties should be evaluated using in vivo orthotopic transplantation in a sufficient number of animals. Mice have been a species of choice in which to study stem cell biology in mammals. However, most pulp-dentin complex regeneration studies have used large animals because the mouse tooth is too small. The purpose of this study was to demonstrate the utility of the mouse tooth as a transplantation model for pulp-dentin complex regeneration research.

Materials and Methods

Experiments were performed using 7-week-old male Institute of Cancer Research (ICR) mice; a total of 35 mice had their pulp exposed, and 5 mice each were sacrificed at 1, 2, 4, 7, 9, 12 and 14 days after pulp exposure. After decalcification in 5% ethylenediaminetetraacetic acid, the samples were embedded and cut with a microtome and then stained with hematoxylin and eosin. Slides were observed under a high-magnification light microscope.

Results

Until 1 week postoperatively, the tissue below the pulp chamber orifice appeared normal. The remaining coronal portion of the pulp tissue was inflammatory and necrotic. After 1 week postoperatively, inflammation and necrosis were apparent in the root canals inferior to the orifices. The specimens obtained after experimental day 14 showed necrosis of all tissue in the root canals.

Conclusions

This study could provide opportunities for researchers performing in vivo orthotopic transplantation experiments with mice.

Phase pure, high hardness, biocompatible calcium silicates with excellent anti-bacterial and biofilm inhibition efficacies for endodontic and orthopaedic applications

Here we report for the very first time the synthesis of 100% phase pure calcium silicate nanoparticles (CSNPs) of the α-wollastonite phase without using any surfactant or peptizer at the lowest ever reported calcination temperature of 850 °C. Further, the phase purity is confirmed by quantitative phase analysis. The nano-network like microstructure of the CSNPs is characterized by FTIR, Raman, XRD, FESEM, TEM, TGA, DSC etc. techniques to derive the structure property correlations. The performance efficacies of the CSNPs against gram-positive e.g., S. pyogenes and S. aureus (NCIM2127) and gram-negative e.g., E. coli (NCIM2065) bacterial strains are studied. The biocompatibility of the CSNPs is established by using the conventional mouse embryonic osteoblast cell line (MC3T3). In addition, the biofilm inhibition efficacies of two varieties of CSNPs e.g., CSNPs(W) and CSNPs(WC) are investigated. Further, the interconnection between ROS e.g., superoxide (O₂^.-) and hydroxyl radical (^.OH) generation capabilities of CSNPs and their biofilm inhibition efficacies is clearly established for the very first time. Finally, the mechanical responses of the CSNPs at the microstructural length scale are investigated by nanoindentation. The results confirm that the α-wollastonite phases present in CSNPs(W) and CSNPs(WC) possess extraordinarily high nanohardness and Young's moduli values. Therefore, these materials are well suited for orthopaedic and endodontic applications.

A Miniature Swine Model for Stem Cell-Based De Novo Regeneration of Dental Pulp and Dentin-Like Tissue

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.

Regulation of Reactionary Dentine Formation

During the treatment of dental caries that has not penetrated the tooth pulp, maintenance of as much unaffected dentine as possible is a major goal during the physical removal of decayed mineral. Damage to dentine leads to release of fossilized factors (transforming growth factor-β [TGF-β] and bone morphogenic protein [BMP]) in the dentine that are believed to stimulate odontoblasts to secrete new "tertiary" dentine (reactionary dentine). This is formed on the pulpal surface of existing dentine and rethickens the dentine. We have previously shown that activation of Wnt/β-catenin signaling is pivotal for tooth repair in exposed pulp injury, and the pathway can be activated by small-molecule GSK-3 antagonists, resulting in enhanced reparative dentine formation. Here, we use a nonexposed pulp injury model to investigate the mechanisms of reactionary dentine formation in vivo, using small molecules to modulate the Wnt/β-catenin, TGF-β, and BMP pathways. We found that a local increase of Wnt activation at the injury site enhances reactionary dentine secretion. In addition, inhibition of TGF-β, BMP, or Wnt pathways does not impede reactionary dentine formation, although inhibition of TGF-β and/or BMP signaling does result in more disorganized, nontubular reactionary dentine. This suggests that Wnt/β-catenin signaling plays no major role in the formation of reactionary dentine, but in common with reparative dentine formation, exogenous elevation of Wnt/β-catenin signaling can enhance tertiary dentine formation. Release of latent TGF-β or BMPs from dentine is not required for the deposition of mineral to form reactionary dentine but does play a role in its organization.