Modified Dental Composites for Bone Repair

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URL: https://discovery.ucl.ac.uk/id/eprint/10138536

Abstract

The aim of this project was to develop modified dental composites for bone repair with additional remineralising monocalcium phosphate monohydrate (MCPM) and antibacterial polylysine (PLS).

Bone composites were prepared with the powder to monomer weight ratio of 3:1. The monomer phase consisted of dimethacrylate monomers with chemical curing initiator and activator. Powder phase consisted of glass filler, PLS as antibacterial agent and MCPM as the mineralising agent. The level of remineralising agent and PLS were varied amongst formulations. Commercial polymethylmethacrylate (PMMA) (SimplexTM P) and bone composite (Cortoss®) were used for comparison. Degree of monomer conversion (DC) was assessed using fourier transform infrared spectroscopy (FTIR) (n=3). Biaxial flexural strength (BFS), tested by means of ball on ring technique, was used to compare the mechanical properties of each formulation (n=6). Surface apatite forming ability was carried out using scanning electron microscopy (SEM). Toxicity of monomers were assessed with sheep mesenchymal stem cells (MSCs) and MG63 cells using an Alamar Blue assay. Chick Embryo Chorioallantoic Membrane (CAM) assay was carried out to assess angiogenesis and development of a chick embryo upon contact with the experimental bone composite.

Optimised initiator (benzoyl peroxide (BP)) and activator (N-(2-hydroxy-3-((2- methyl-1-oxo-2-propenyl)oxy)propyl)-N- tolyl glycine (NTGGMA)) levels enabled working times comparable to commercial cement, and advantageously higher conversion and lower heat generation. Increasing PLS resulted in decreased strength and cell activity. Conversely higher MCPM had lesser detrimental effect on these properties and increased surface mineral precipitation both in-vitro and in-ovo. CAM assay showed, the set discs were generally not toxic (particularly those with high MCPM). Over time the CAM also showed strong adherence for the experimental bone composite discs but not the commercial PMMA.

The experimental bone composites show promising potential, since it encouraged apatite precipitation, which is known to promote bone bonding and did not show toxicity to the developing chicks embryos.

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