A biomechanical evaluation of CNT-grown bone

The combined use of carbon nanotubes with synthetic ceramics enhances posterolateral fusion: an experimental study in a rat spinal fusion model

PURPOSE

The aim of the present study was to evaluate the effectiveness of carbon nanotubes (CNTs)/ HA-tricalcium phosphate (TCP) composite in a posterolateral spinal fusion model.

METHODS

At first, CNTs and CNTs/HA-TCP composites were prepared. Twenty adult male Sprague Dawley rats were randomized into four groups with five rats in each group. Decortication was carried out in standard manner in all animals. Group 1 (only decortication), group 2 (CNTs), group 3 (HA-TCP) and group 4 (CNTs/HA-TCP) were formed. Eight weeks later, all animals were killed and obtained fusion segments were evaluated by manual palpation, histomorphometry and micro-computed tomography (mCT).

RESULTS

In all evaluations, highest fusion values were obtained in Group 4. In mCT investigations, bone volume/ tissue volume (BV/TV) ratio was found to be significantly higher in composite group (group 4) only compared to ceramic group (group 3) (p < 0.001). Although in Group 2, in which only CNTs were used, the ratio was found to be statistically significantly higher than group 1(p < 0.001), the difference was not considered as significant in terms of fusion and in addition in group 2, CNTs were completely surrounded by fibrous tissue, i.e., no bone formation was observed.

CONCLUSIONS

The CNTs/HA-TCP composite is a promising synthetic bone graft substitute for spinal fusion. Although CNTs are inadequate in producing spinal fusion when they are used alone, due to their high biocompatibility due to their high biocompatibility, and multiple effect on bone regeneration, they seem to increase fusion rates significantly when they are used in combination with ceramic-based synthetic grafts.

Young’s Modulus and Vickers Hardness of the Hydroxyapatite Bioceramics with a Small Amount of the Multi-Walled Carbon Nanotubes

The Vickers hardness and Young’s modulus of the hydroxyapatite (HA) bioceramics with a small amount of the multi-walled carbon nanotubes (MWCNTs) were studied by using ultramicrotester Shimadzu for dynamic tests DUH-211. Small concentrations of MWCNTs were from 0.05 to 0.5 wt.%. The argon inert atmosphere and vacuum condition were taken for the prevention of the MWCNTs oxidation. The Brunauer–Emmett–Teller (BET) surface area S_BET of the HA-MWCNTs composites was determined by thermal adsorption-desorption of nitrogen. It was found that for HA-MWCNTs sintered in the Ar atmosphere, an increase in the concentration of nanotubes up to 0.5 wt.% leads to a decrease in porosity near 3 times in comparison to HA without MWCNTs additives. The small amount of additives of multi-walled carbon nanotubes leads to an increase in hardness of 1.3 times and compression strength of composite and compression strength of composite that is comparable in absolute values with the literature data of enamel hardness (3–5 GPa) and compression strength (95–370 MPa). The absolute values increase close to linearly with the increase of nanotube concentrations. The Young’s modulus of sintered composite slightly changes with the variation of concentrations of nanotubes and close to the enamel (75–100 GPa). The ratio of plastic work to total work and the ratio of elastic (reversible) work to the total work of deformation of composite HA/MWCNTs are practically constant at a studied range of MWCNTs concentration. The additives of the multi-walled carbon nanotubes lead to both an increase in the elasticity index of ~1.5 times and an increase in the resistance to plastic deformation of ~3 times, which improved the tribological performance of the surface. Plastic and elastic (reversible) work slightly changed.

Dental Applications of Carbon Nanotubes

Glass ionomer cements and resin-based composites are promising materials in restorative dentistry. However, their limited mechanical properties and the risk of bulk/marginal fracture compromise their lifespan. Intensive research has been conducted to understand and develop new materials that can mimic the functional behavior of the oral cavity. Nanotechnological approaches have emerged to treat oral infections and become a part of scaffolds for tissue regeneration. Carbon nanotubes are promising materials to create multifunctional platforms for dental applications. This review provides a comprehensive survey of and information on the status of this state-of-the-art technology and describes the development of glass ionomers reinforced with carbon nanotubes possessing improved mechanical properties. The applications of carbon nanotubes in drug delivery and tissue engineering for healing infections and lesions of the oral cavity are also described. The review concludes with a summary of the current status and presents a vision of future applications of carbon nanotubes in the practice of dentistry.

Degradation Behavior In Vitro of Carbon Nanotubes (CNTs)/Poly(lactic acid) (PLA) Composite Suture

Poly(lactic acid) (PLA) suture can be absorbed by the human body, and so have wide applications in modern surgery operations. The degradation period of PLA suture is expected to meet with the healing time of different types of wounds. In order to control the degradation period of the PLA suture, the carbon nanotubes (CNTs) were composited with PLA suture, and the degradation experiment in vitro was performed on sutures. The structure and properties of sutures during degradation, such as surface morphology, breaking strength, elongation, mass and chemical structure, were tracked and analyzed. The results indicated that the degradation brought about surface defects and resulted in 13.5 weeks for the strength valid time of the original PLA suture. By contrast, the strength valid time of the CNTs/PLA suture was increased to 26.6 weeks. Whilst the toughness of both the pure PLA and CNTs/PLA sutures decreased rapidly and almost disappeared after 3 to 4 weeks of degradation. The mass loss demonstrated that the time required for complete degradation of the two sutures was obviously different, the pure PLA suture 49 weeks, while CNTs/PLA sutures 63 to 73 weeks. The research proved that CNTs delayed PLA degradation and prolonged its strength valid time in degradation.