Biocompatibility and Bioactivity of Calcium Silicate-based Dental Bioceramics

Abstract

Tricalcium silicate dental bioceramics are bioactive ceramics. They are used to repair and treat iatrogenic, and pathological communications between the oral environment and mesenchymal tissue through tooth structure, or as a retrograde root filling after root resection. They are placed in direct contact with mesenchymal tissues. Poor handling properties and high cost has led to the development of new formulations. These aim to improve on the original materials handling properties, and reduce material cost.

This in vitro study looked at the biocompatibility of Biodentine (a new tricalcium silicate formulation), comparing it to the original tricalcium silicate material ProRoot MTA. The study used gingival and periradicular fibroblast cell cultures, with both direct and indirect material exposure methods. Several cell culture techniques were used to determine biocompatibility and bioactivity of tricalcium silicate-based materials:

1)Visual observations of cell
2) Cell viability assays
3)Immunocytochemistry
4)Protein Biochemistry
5)mRNA expression analysis

Visual observations demonstrated differing changes in cellular morphology between our two main test materials and cell lines, with gingival fibroblasts demonstrating a more spindle like morphology, with reduced cytoplasmic volume when exposed to grey ProRoot MTA. Periradicular fibroblasts demonstrated a more stellate morphology when exposed to mineral precipitates of Biodentine.

Immunocytochemistry and protein biochemistry demonstrated differences in vimentin expression between cell lines. Increased vimentin expression of a gingival fibroblast cell line may indicate both an increased level of cellular stress and a reduced osteogenic potential. Reduced vimentin expression in periradicular fibroblasts may indicate the opposite, with better tolerance to tricalcium silicate materials and a greater osteogenic potential.

Cell viability assays (MTT assay) demonstrated differing toxicity profiles between Biodentine and ProRoot MTA, with Biodentine showing a marked initial toxicity, and ProRoot MTA showing an increased toxicity between 14-21 days at high eluate concentrations. Cell viability assay results also suggest that protective anti-apoptotic pathway is initiated. Vimentin upregulation may be involved in this protective mechanism. Although differences in cell morphology were seen between cell lines, similar cell viability assay (MTT assay) results between cell lines suggest that some changes in morphology are not due to toxicity.

Analysis of RNA collected after gingival fibroblasts were exposed to tricalcium silicate samples for 35 days shows continued bioactivity of tricalcium silicates. Although not directly involved in osteogenesis, gingival fibroblasts may stimulate osteogenesis via recruitment of progenitor cells via growth factors and release of bioactive peptides units produced by extracellular matrix degradation.

Date of Award	2016
Original language	English
Supervisor	William Saunders (Supervisor), Ian Ellis (Supervisor) & Sarah Jones (Supervisor)