Experimental study of the Ti-implant surfaces structured by the ytterbium-doped pulsed fiber laser

Relevance. Currently, there are several basic techniques for the dental implant surface structuring. Laser treatment is an extremely promising technique for the surface structuring. This technology allows creating regular implant surface without using chemicals and in just one technological step. The purpose was to present study aimed to compare and evaluate in vivo the stability and osseointegration of dental implants with 2 different surfaces structured by ytterbium-doped pulsed fiber laser operating at 1064 nm.Materials and methods. 60 dental implants were placed in the study. 2 types of dental implant surfaces, namely holes and parallel grooves, were created by the ytterbium laser operating at 1064 nm. A polished dental implant (without laser surface structuring) was also included in the experiment for comparison. The study was carried out on 15 laboratory animals (male rabbits, weight 3.5-4 kg). The implants were placed in the tibia. 4 implants with different surface types but of the same diameter and length were placed in each rabbit.Results. Laboratory animals were sacrificed 1.5 and 3 months after the surgery. The stability of the implants was assessed by RFA (Resonance Frequency Analysis), based on the registration of resonance electromagnetic oscillations of the implant and the surrounding bone when they are exposed to the electromagnetic field (Osstell ISQ). Also, nondecalcified bone blocks were histologically examined using a confocal laser scanning microscope (Carl Zeiss LSM 780) and histomorphometry was performed (BIC-index: Bone-to-implant contact). Bone blocks were prepared according to a special technique: they were soaked and embedded into the plastic and synthetic resin. The obtained blocks were cut into sections, 40-50 µm thick, and stained with toluidine blue.Conclusion. Laser surface structuring of the dental titanium implants is a promising technique. 59 in 60 (98.3%) implants were osseointegrated, there were no signs of inflammation in the bone tissue. The present results allow further studying of dental implants with various surface designs, structured by ytterbium laser.

Real-space observation of surface structuring induced by ultra-fast-laser illumination far below the melting threshold

Intense short laser pulses are an intriguing tool for tailoring surface properties via ultra-fast melting of the surface layer of an irradiated target. Despite extensive studies on the interaction of femto-second laser interaction with matter, the initial steps of the morphological changes are not yet fully understood. Here, we reveal that substantial surface structure changes occur at energy densities far below the melting threshold. By using low-temperature scanning tunneling microscopy we resolve atomic-scale changes, i.e. the creation of nanosized adatom and vacancy clusters. The two cluster types have distinct non-linear fluence-dependencies. A theoretical analysis reveals their creation and motion to be non-thermal in nature. The formation of these atomistic changes, individually resolved here for the first time, recast our understanding of how surfaces respond to low-intensity ultra-short laser illumination. A visualization and control of the initial morphological changes upon laser illumination are not only of fundamental interest, but pave the way for the designing material properties through surface structuring.

Unique and universal dew-repellency of nanocones

Surface structuring provides a broad range of water-repellent materials known for their ability to reflect millimetre-sized raindrops. Dispelling water at the considerably reduced scale of fog or dew, however, constitutes a significant challenge, owing to the comparable size of droplets and structures. Nonetheless, a surface comprising nanocones was recently reported to exhibit strong anti-fogging behaviour, unlike pillars of the same size. To elucidate the origin of these differences, we systematically compare families of nanotexture that transition from pillars to sharp cones. Through environmental electron microscopy and modelling, we show that microdroplets condensing on sharp cones adopt a highly non-adhesive state, even at radii as low as 1.5 µm, contrasting with the behaviour on pillars where pinning results in impedance of droplet ejection. We establish the antifogging abilities to be universal over the range of our cone geometries, which speaks to the unique character of the nanocone geometry to repel dew. Truncated cones are finally shown to provide both pinning and a high degree of hydrophobicity, opposing characteristics that lead to a different, yet efficient, mechanism of dew ejection that relies on multiple coalescences.

Surface Structuring by Laser Remelting (WaveShape): Microstructuring of Ti6Al4V for a Small Laser Beam Diameter and High Scan Speeds

The appearance of a surface is a crucial characteristic of a part or component. Laser-based micromachining gets increasingly important in generating tailored surface topographies. A novel structuring technique for surface engineering is surface structuring by laser remelting (WaveShape), in which surface features are created without material loss. In this study, we investigated the evolution of surface topographies on Ti6Al4V for a laser beam diameter of 50 m and scan speeds larger than 100 mm/s. Surface features with aspect ratios (ratio of height to width) of almost 1:1 were achieved using the WaveShape process. Furthermore, wavelengths smaller than 500 m could be effectively structured using scan speeds of up to 500 mm/s. The experimental results showed further that the efficiency of the WaveShape process in terms of achieved structure height per unit time significantly increases for high scan speeds.