LASIMP - Research project

The LASIMP project explored the relevance for dental implantology of surface topographies produced by femtosecond laser on a titanium alloy, by controlling several parameters (wavelength, polarization, power, etc.). This study revealed the impact of both nanoscale and microscale dimensions on bacterial colonization and gingival tissue adhesion, thanks to the development of specific evaluation methods.
Topographical parameters correlated with the adhesion of two bacterial strains (P. gingivalis and S. mutans), responsible for peri-implant infections, were identified, thus determining key parameters to consider during laser texturing.
Texturations exhibiting a dual functional nature were validated through an in vitro study under pro-infectious conditions, aiming for optimal clinical application. This notably involves promoting a tight junction between the implant and the gingiva, as well as an implant surface that limits bacterial colonization.

 

To assess the biological performance of texturing produced by femtosecond laser, topochips containing a multitude of different nanostructures were manufactured by the Hubert Curien laboratory and Manutech-USD. Several laser sources (1030nm, 515nm and 257nm) and several laser parameters (beam power, fluence, number of pulses, polarization) were tested. The nanostructures obtained were characterized by Scanning Electron Microscopy (SEM). 

Streptococcus mutans, a bacterium involved in peri-implantitis, was seeded on the topochips and labeled with calcein to evaluate the properties of each texturing. This preliminary screening showed that, in accordance with the literature, the correlation between pattern periodicity and bacteria size, is directly linked to bacterial ability to adhere on titanium surfaces (Figure 2). Bacteria and topographies interactions are also observed by SEM, confirming that when pattern periodicity is inferior to bacteria size, contact surfaces between titanium and bacteria are reduced, and so is the bacterial adhesion (Figure 3).
To assess short-term cell adhesion, fluorescence microscopy was used to analyze the formation and localization of focal contacts on different areas. At 48 hours, human mesenchymal stem cells (hMSCs) have formed larger focal contacts on polished surfaces compared to textured surfaces (Figure 4). However, in the longer term (28 days of culture), scratch tests on cell layer, developed by the LTDS, have shown that the adhesion of the cell layer is better on the areas textured with the femtosecond laser (Figure 5). These adhesion tests were developed on hMSCs, and similar tests are now carried out on gingival fibroblasts. Since one of the major problems of peri-implantitis is the lack of adhesion of the gingival tissues to the implant, which leads to bacterial infiltration, an improved fibroblasts adhesion will be a key to increase implant lifetime.