Methods: Nano-HA powder was produced from the sol-gel. A novel covalently bonded PU-nano-apatite composite material was chemically prepared by utilising solvent polymerisation. Chemical, thermal, and mechanical properties of the resulting composites were investigated. The resultant composite material was electrospun to form fibre mats. The bio-adhesion with dentine were analysed in distilled water and artificial saliva. Bioactive behaviour was determined in simulate body fluid (SBF). The composites were hydrolytically degraded in distilled water and phosphate buffer saline (PBS) and were analysed. Cell growth and proliferation was measured by MTS assay.
Results: Spectral analyses showed the grafted isocyanate and ether peaks on HA indicating that urethane linkage was established. The thermal and mechanical properties were enhanced by nano-HA (p=0.05). The SEM images of electro-spun nano-fibres revealed no loose HA particles. Bio-adhesion and bioactivity analysis showed the composite adhered firmly on the tooth surface (enamel/dentine or both). Higher nano-HA content composite showed thicker layer of adhesion. These composites had high resistance toward hydrolysis and little degradation and a significant difference was observed (p<0.05). Biocompatibility test of the composite showed that the cells were growing although at a lower rate of growth compared to PU.
Conclusion: Covalent bond between HA and polymer were found in this novel composite with no silane agent. Bio-adhesion was found between this composite and tooth structure. Hence, it has the potential to be a desirable restorative material.