Properties of Hydraulic Calcium Silicate-Based Cement for Vital Pulp Therapy

Abstract

The introduction of hydraulic calcium silicate-based cements (HCSCs) caused a paradigm shift in endodontics. Contemporary trends of managing deep caries and exposed pulp turned shifted to a minimally invasive and biologically based approach. The application of HCSCs in vital pulp therapy (VPT) is beneficial due to their hydraulic nature, requiring water to set and reach optimal properties. Additionally, the calcium hydroxide formed as a by-product of the setting reaction attributes to the bioactivity and antimicrobial properties. Recently, several modified HCSCs have been introduced to enhance the beneficial effect. These modifications include substituting cementitious phase, alternative vehicles or incorporating various additives, namely calcium chloride, calcium fluoride, silicon dioxide or resin component. This project investigated modified HCSC and glass-ionomer cement used for VPT and whether different modifications affect their setting reactions and properties. The investigated commercial materials were either established: Fuji IX GP ®, MTA Angelus™ and Biodentine™, or newly released: Bio-C Pulpo and EndoSequence® BC liner™. The materials’ hydration characteristics and microstructure were investigated with scanning electron microscopy coupled with dispersive energy spectroscopy and X-ray diffraction (XRD) analysis. Setting time, radiopacity, microhardness, and compressive strength were determined. In addition, materials’ solubility were monitored over time, and leachates were evaluated for pH change and calcium ions release by inductive coupled plasma - optical emission spectroscopy (ICP-OES). Interaction with simulated body fluid (HBSS), as well as treated and untreated caries-affected dentine, were investigated. Remineralisation potential was assessed by dentinal mechanical recovery and minerals content analysis (calcium/phosphorus ratio). Finally, antimicrobial efficacy was evaluated in planktonic and biofilm forms. Bio-C Pulpo had a typical Portland cement-based microstructure but no calcium hydroxide formation as a by-product. The addition of silicon dioxide enhanced the material strength, which decreased over time, and calcium chloride decreased the setting time and enhanced the chemical profile in comparison to MTA. The inclusion of calcium fluoride enhanced reactivity and promoted remineralisation only at the adjacent dentine while presenting a wide interface. EDTA enhanced the adaptation of all included HCSCs. Bio-C Pulpo possessed a comparable antimicrobial and antibiofilm activity to MTA and Bodentine while decreasing over time. BC liner presented a glass phase interspersed into the polymeric matrix, with inadequate polymerisation after 20 sec of curing. The incorporation of hybrid resin increased the material strength significantly. A minor amount of calcium was identified in the material composition, and a negligible amount of calcium was released that aided a neutral pH over time despite the presence of polyacrylic acid. The addition of sodium fluoride was ascertained by XRD and deposited on the surface after ageing. It presented a satisfactory adaptation to dentine. Overall, material modifications altered setting reactions and enhanced the desired properties.

Date of Award	1 Aug 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Alison Qualtrough (Supervisor), Nick Silikas (Supervisor) & Joanne Cunliffe (Supervisor)