Hydroxyapatite Whiskers Based Resin Composite versus Commercial Dental Composites: Mechanical and Biocompatibility Characterization

A systematic evaluation of mechanical and biocompatibility properties of different volume fractions of hydroxyapatite whiskers incomparison with three commercial dental composites filled with micro- and nanosilica particles was carried out. Six groups withdifferent hydroxyapatite whiskers mass fractions were taken into account in order to be compared with the performances of silicaparticles based composites group. Flexural properties were evaluated via a universal testing machine (2.5 kN Zwick Line) with a2 kN load-cell (sensitivity 0.001 N).The test was replicated 10 times for the seven experimental groups to better identify staticallythe significance of the mechanical performances data.MTT quantitative colorimetric assay was performed in order to evaluate the mitochondrial activity of living cells exposed to different resin composites. Data obtained show better interfacial interaction withfiller/matrix until 20 wt% of hydroxyapatite whiskers partially replaced silica particles filler. After this threshold, the mechanicalperformances decrease dramatically due to both the hydroxyapatite agglomerates formation and the low degree of resin conversion.In addition, biocompatibility test showed less cytotoxic effect with the addition of 20wt% of hydroxyapatite in comparison with higher rates.