Elkateb, Walid M; (2024) Bioactive Brushite Cements for Regenerative Endodontics with added Hydroxyapatite Nanoparticles and Antibacterial ɛ-Polylysine. Doctoral thesis (Ph.D), UCL (University College London).

Text Thesis-WalidElkateb-electronic copy-SN17000178 (1).pdf - Submitted Version Access restricted to UCL open access staff until 1 March 2025. Download (13MB)

Abstract

Vital pulp therapy and Revascularization are two endodontic techniques that rely on the regenerative capacity of dental pulp stem cells. An Ideal material for these techniques should be antibacterial, encourage cell proliferation and ion release for remineralisation. Other requirements include suitable handling, setting and mechanical properties. Unfortunately, current commercial materials, fall short of some of these requirements. Calcium phosphates have inherent biocompatibility, bio-interactivity and bioactivity. Nevertheless, their application in Endodontics have not been fully explored. Aim is to develop and optimise a brushite forming calcium phosphate cement for utilisation in Vital pulp therapy and Revascularisation. This will be done by addition of Hydroxyapatite (HA) nanoparticles in the presence of ɛ polylysine (PLS) as an antibacterial agent and comparing it to Mineral Trioxide Aggregate (MTA), Biodentine and Dycal. Methods: 18 brushite cement formulations were developed by optimizing citric acid concentration, incorporating hydroxyapatite (HA), and varying antibacterial ε-polylysine (PLS) concentrations. The setting kinetics, mechanical properties, mass changes, and apatite precipitation were examined and compared. The best performing formulations were then assessed against commercial materials, (including MTA, Biodentine, and Dycal). Setting and dissolution kinetics were determined using FTIR and gravimetrically. Flexural strength after setting for 24 hours and upon immersion in deionised water and DMEM for up to 8 weeks was determined. To test biocompatibility, cellular cytotoxicity and adherence of hDPSCs on disc surfaces were assessed with SEM and live/dead (L/D) stain. Expression of odontoblastic differentiation markers and ability of cells to form calcific deposits were done using immunofluorescence and Alizarin red staining respectively. Finally, the fracture resistance of teeth after in-vitro simulated revascularization technique obturated with cervical plugs made from the best optimised experimental formulation and commercial alternatives (MTA and Biodentine) was tested. Results& Conclusion: The influence of the added components on the cement formulation's performance revealed, that increasing citric acid content allows for better control over setting kinetics and working time. While HA addition reduces mass loss, enhances mechanical properties, and speeds up apatite precipitation. However, PLS, while potentially offering antibacterial benefits, contributed to increased mass loss and decrease in flexural strength. Experimental formulations with highest HA content exhibited comparable or superior properties in terms of working time, setting time, solubility, and apatite formation when compared to commercial cements. They also showed cytocompatibility and potential for promoting differentiation and calcification. And finally, also showed an enhanced fracture resistance to revascularized teeth comparable to the commercial alternatives.

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