Flexural Properties of Glass Fibre Reinforced Composite with Partially Biodegradable Polymer Matrix

Marju Väkiparta1 and Pekka K. Vallittu2

1University of Turku, Institute of Dentistry, Department of Prosthetic Dentistry and Biomaterials Science and Turku Biomaterials Centre, Itäinen Pitkäkatu 4 B, FIN-20520 Turku, Finland

2University of Turku, Institute of Dentistry, Department of Prosthetic Dentistry and Biomaterials Science, Lemminkäisenkatu 2, Turku, Finland

Introduction

Composites are becoming more commonly used in dental and medical applications to replace the metal and polymer materials.Flexural properties of the composites for bone substitute applications should mimic flexural properties of the bone to avoid the stress shield in the interface of the bone and composite implant. Recently have been found that using biodegradable poly(4-L-hydroxy-L-proline) (PA) as a coating of the fibres in fibre-reinforced composite (FRC), canal formation between the fibres and matrix is possible in simulated body fluid allowing the hydroxyapatite ingrowth to the composite [[1]] and thus making bone ingrowth possible. However, that canal formation may decrease the mechanical properties of FRC.

The aim of the study was to determine the flexural strength and modulus of elasticity of partially biodegradable matrix containing FRC after water immersion.

Materials and methods

Investigated test groups in this study were Bis-GMA/TEGDMA (BN), Bis-GMA/TEGDMA with E-glass fibres (BEN) and Bis-GMA/TEGDMA with E-glass fibres coated with PA (BESN). The specimens were polymerized with light ( = 480 nm). Specimens were stored in water for one week at +37 C and dehydrated at least for 3 days at +40 C.

The 3-point bending tests were used to measure the flexural strength and Young’s modulus of the specimens. The quantity of fibres was also determined.

Results and Discussion

Minor increase was found in flexural strength of FRC after water immersion compared to not-immersed in groups BT and BTE (108 vs. 81 MPa and 838 vs. 805 MPa, respectively). Residual monomers and other small molecules can act as plasticizers and during water immersion they leach out from the composite, thus making composite stiffer. Flexural strength and Young’s modulus of the BTES decreased (from 888 to 634 MPa and from 27 to 23 GPa, respectively) because of the dissolution of PA forming open canals between fibres and matrix weakening mechanical properties of FRC. However, the strength and modulus of FRC are level, which are demands for implant for load bearing bone applications.

Quantity of glass fibres was 0 wt % for BT, 59.6 wt% for BTE and 52.6 wt% for BTES.

Conclusions

It can be concluded that coating of glass fibres with biodegradable PA combined with Bis-GMA–TEGDMA monomers resulted in lower flexural strength and modulus than without coating however preserving enough mechanical properties for load-bearing bone substitute applications. However, further in vitro studies are needed to show the behavior of partially biodegradable FRC in environment simulating the conditions of the body.

Keywords: fibre-reinforced composite; biodegradable; mechanical properties

References:

[[1]] M. Väkiparta et al., J Mater Sci: Mater Med16, 873 (2005).