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Development and characterisation of dental composites containing anisotropic fluorapatite bundles and rods

Lookup NU author(s): Dr Matthew GermanORCiD



This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


Objectives To develop dental composites incorporating fluorapatite (FA) crystals as a secondary filler and to characterise degree of conversion, key mechanical properties and fluoride release. Methods FA rod-like crystals and bundles were hydrothermally synthesised and characterised by Scanning Electron Microscopy/ Energy Dispersive X-ray Spectroscopy (SEM/EDS), X-ray Diffraction (XRD) and 19 F MAS-NMR. Composites were formulated containing BisGMA/TEGDMA/BisEMA and barium- aluminium- silicate glass (0FA). FA crystals were incorporated at 10 (10FA), 20 (20FA), 30 (30FA) and 40 wt% (40FA) maintaining a filler content of 80 wt% (63-67 vol%). Degree of conversion (DC), flexural strength (FS), flexural modulus (FM), fracture toughness (K1C), Vickers hardness (HV) and 2-body wear were measured. Fluoride release was measured in neutral and acidic buffers. Results XRD and 19 F MAS-NMR confirmed that only FA was formed, whilst SEM revealed the presence of single rods and bundles of nano-rods. DC ranged between 56-60% (>0.05). FA composites showed lower FM and lower FS ( p <0.05), but comparable wear resistance and HV ( p >0.05) to 0FA. 30FA and 40FA showed similar K1C to 0FA ( p >0.05), with SEM showing evidence of toughening mechanisms, whereas 10FA and 20FA showed lower K 1C ( p <0.05). FA containing composites released fluoride that was proportional to the amount of FA incorporated (p <0.05) but only under acidic conditions. Significance The addition of FA to the experimental composites reduced strength and stiffness but not the DC, hardness or wear rate. 30FA and 40FA had a higher K 1C compared to other FA groups. Fluoride release occurred under an accelerated acidic regime, suggesting potential as a bioactive ‘smart’ composite.

Publication metadata

Author(s): Altaie A, Bubb N, Franklin P, German MJ, Marie A, Wood DJ

Publication type: Article

Publication status: Published

Journal: Dental Materials

Year: 2020

Volume: 36

Issue: 8

Pages: 1071-1085

Print publication date: 01/08/2020

Online publication date: 05/06/2020

Acceptance date: 05/05/2020

Date deposited: 19/05/2020

ISSN (print): 0109-5641

Publisher: Elsevier


DOI: 10.1016/


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