Particles released from implants following the mock implantoplasty procedure were collected, and microparticle size of particles produced from the grade 4 (G4) and grade 5 (G5) implants was 77.4 ± 9.1 μm (modal number 66.3 μm) and 48.4 ± 6.4 μm respectively (modal number 43.1 μm). DLS analysis showed nano-sized particles were also present: hydrodynamic diameters were 125.4 ± 10.9 nm (modal number 109.3 nm) and 57.74 ± 2.66 nm (modal number 52.1 nm) respectively. SEM images (Fig. 1) revealed that particles fragmented from both G4 and G5 implants as the result of implantoplasty were irregular in shape and varied significantly in sizes. The elemental composition of the particles was analysed using EDX (Fig. 2). The EDX spectra demonstrated distinctive differences between G4 and G5 particles. In addition to titanium (Ti), both aluminium (Al) and vanadium (V) were detected in G5 particles. Carbon (C) was detected in both samples. According to EDX analysis, the spherical objects amongst implant particles (indicated by arrows in Fig. 1) were titanium oxide.

Release of ions from the G4 and G5 particles was first investigated in SBF (Fig. 3). Upon immersion, the release of Ti was minimal from both G4 and G5 particles in SBF. Release of V from G5 particles was detected by ICP only after 10 days of immersion. There was no noticeable release of aluminium (Al) and iron (Fe) ions. The pH of SBF remained at 7.4 during the immersion period. Similar results were observed when the particles were immersed in DMEM (Fig. 4), with low release of Ti and no noticeable release of aluminium Al and Fe from both G4 and G5 particles. V, up to 0.116 ± 0.023 ppm, was only detected in medium containing G5 implant particles. Changing the concentration of the particles had little effect. As Al results were negligible, we assumed that no alloy particles passed through the 200-nm filters, but TiO₂ nanoparticles may have contributed to the Ti values (DLS measurement of blank media control returned value of 0).

The effect of G4 and G5 particles and their dissolution products on human gingival fibroblast viability in vitro was investigated using an MTT metabolic activity assay (Fig. 5). Administration of the dissolution products had no effect on cellular metabolic activity up to day seven, but there appeared to be a reduction in metabolic activity in cells exposed to G5 dissolution products by day 10, though it was not statistically significant. When the cells were exposed to G5 particles, metabolic activity significantly reduced as early as day 3. However, when cells were cultured with the G4 particles, there were no adverse effects. The significantly reduced metabolic activity as a result of exposure to G5 particles was observed at all-time points. Changing the concentration of the particles had little effect.