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UBC Theses and Dissertations

Synthesis and characterization of calcium phosphate silicate bio-cements Zhou, Shuxin


Calcium phosphate silicate cement (CPSC) describes a family of materials in which the powder component is composed of the mixture of hydraulic calcium silicates and calcium phosphates. CPSC was developed and characterized in this work with the broad goal to address, and possibly overcome, the disadvantages of calcium silicate and calcium phosphate cements used in medical and dental fields. The main objective of this work was to synthesize and characterize CPSC, focusing particularly on the hydration process of CPSC. The cements consisting of various amounts of triclacium silicate (C₃S) and calcium phosphate monobasic (CPM), were synthesized by the sol-gel process, followed by heat treatment at 1550ºC and planetary ball-milling. It has been determined that after mixing with water, C₃S hydrates to calcium silicate hydrates (C-S-H) and calcium hydroxide (CH); within 10 min CPM reacts with CH to form dicalcium phosphate dihydrate (DCPD), which further reacts with CH and precipitates hydroxyapatite (HAP). It is proposed that the phosphate ions incorporate into C-S-H to form another type of hydrates C-S-P-H. The morphology of the hydrates depends on the process of hydration and the composition of CPSC. At the early stages of hydration, the hydration products form “almond-shaped” particles that serve as a nucleation site for the hydrates. The hydrates take tubular shape and form bundles clustered along the radial direction of the tubes. CPM influences the hydration kinetics of C₃S by increasing the duration of the hydration acceleration period rather than increasing the hydration rate, especially for the higher content of CPM in CPSC. CPM also increases the porosity of CPSC and reduces the content of CH, thought to be the “weak link” in the set CPSC. As a compromise between the two effects, the optimal content of CPM appears to exist at about 10 wt% of CPM in CPSC. After immersion in simulated body fluid, HAP forms on the surface of CPSC indicating that CPSC is bioactive in vitro. Cytotoxicity assay and cell adhesion assay against human gingival fibroblast indicated that the biocompatibility of CPSC is significantly enhanced.

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