Microhardness and Fracture Resistance of Radicular Dentin Treated with Different Concentrations of Calcium Hydroxide in Endodontic Regeneration Procedures

Purpose: to reveal the effect of different concentrations of prepared calcium hydroxide pastes (70%, 50%, and 30%) used in regenerative endodontic on microhardness and fracture resistance of radicular dentin. Material and methods: Different concentrations of calcium hydroxide (Ca(OH)2) were prepared with measured pH, then forty eight single rooted teeth were prepared and randomized into three groups according to Ca(OH)2 paste concentrations (12 samples each) and 12 samples were availed as control group. Group I: root canal contained 30% Ca(OH)2 paste. Group II: root canal contained 50% Ca(OH)2 paste. Group III: root canal contained 70% Ca(OH)2 paste. Samples were stored at 37 0C with 100% humidity for four weeks for subsequent microhardness and fracture resistance tests. Results: There was a statistically significant reduction of microhardness and fracture resistance between test groups and control group (P≤ 0.05), group III showed a significant reduction in both microhardness and fracture resistance compared to group I. However, there was no significant difference in pH between different concentration of Ca(OH)2. Conclusion: Increasing concentration of Ca(OH)2 paste can negatively affect microhardness and fracture resistance of radicular dentin in revascularization procedure.

In Situ Oxygen Generation Enhances the SCAP Survival in Hydrogel Constructs

Prolonged and severe hypoxia is the main cause of death of transplanted cells prior to the establishment of functional circulation. In situ generation of oxygen by oxygen-producing scaffolds—a unique solution that could produce and deliver oxygen to the adjacent cells independently of blood perfusion—has attracted considerable attention to enhance the survivability of the transplanted cells. However, the application of oxygen-generating scaffolds for facilitating cell survival in pulp-like tissue regeneration is yet to be explored. In this study, gelatin methacryloyl (GelMA)—a biocompatible scaffolding material that closely mimics the native extracellular matrix and is conducive to cell proliferation and differentiation—was used to fabricate oxygen-generating scaffolds by loading various concentrations of CaO2. The CaO2 distribution, topography, swelling, and pore size of CaO2-GelMA hydrogels were characterized in detail. The release of O2 by the scaffold and the viability, spreading, and proliferation of stem cells from apical papilla (SCAPs) encapsulated in the GelMA hydrogels with various concentrations of CaO2 under hypoxia were evaluated. In addition, cellular constructs were engineered into root canals, and cell viability within the apical, middle, and coronal portions was assessed. Our findings showed that 0.5% CaO2-GelMA was sufficient to supply in situ oxygen for maintaining the embedded SCAP viability for 1 wk. Furthermore, the 0.5% CaO2-GelMA hydrogels improved the survivability of SCAPs within the coronal portion of the engineered cellular constructs within the root canals. This work demonstrated that 0.5% CaO2-GelMA hydrogels offer a potential promising scaffold that enhances survival of the embedded SCAPs in endodontic regeneration.

Nanomaterials for Endodontic Regeneration

Irreversible pulp inflammation is so painful that the clinical treatment is the removal of the entire pulp tissue. The current irreversibility of this inflammation is due to the lack of suitable biomaterials able to control it and to orchestrate pulp regeneration. Vitality of the tooth is so important for its functional life that adequate regenerative biomaterials must be developed. Whatever the degree of tooth maturity and its pathology, pulp and surrounding tissues constitute a treasure of dental stem cells. Advances of regenerative nanomedicine provide innovative strategies to use these strongly regenerative stem cells for endodontic regeneration. These cells can support endodontic regeneration by cell homing or by being seeded in biomaterials. Whatever the regenerative strategy, nanotechnologies optimise the attraction, colonisation, proliferation and differentiation of dental stem cells. The nano-reservoirs of active biomolecules orchestrate and enhance their cellular functions. The nanofibers constitute biomimetic scaffolds which promote their pulp connective tissue regeneration. Nanostructured composite scaffolds functionalized by controlled drug delivery systems of several active biomolecules would be the future nanobiomaterials for meeting the challenge of the complex endodontic regeneration.