Surface bio-functionalization using plasma of argon could alter microbiological and topographic surface analysis of dental implants?

BACKGROUND

Plasma of argon was demonstrated to improve protein and cell adhesion on implant surface. On the other hand, increased surface energy and hydrophilicity could potentially amplify the risks of implant surface contamination during clinical phases, risks that have not yet been evaluated in Literature. The aim of the present in vitro study was to verify if Plasma treatment could alter the implant surface characteristics and its ability to remain sterile.

MATERIALS AND METHODS

Implants from 9 brands were collected (n=11). One implant for each company was used for SEM surface analysis. To perform the microbiological analysis, ten implants from each company were used and randomly split by allocation either in test or control group. To replicate the surgical work flow, both test and control samples were left 60s in clinical environment. Bacterial growth analysis was performed. Optical density at 600nm was measured as readout of bacterial growth and colony forming unit (CFU) after 24h was evaluated. Statistical analysis was performed by using the Wilcoxon Mann Whitney test. A p-value lower than 0.05 was considered significant.

RESULTS

SEM analysis revealed different categories of implant surface roughness. The optical density confirmed a readout of bacterial growth between 4 and 7 with no significant differences within groups. The number of CFU/ml for each measured sample (test and control) was lower than 102 and failed to present significant differences.

CONCLUSION

Surface activation using plasma of argon did not affect the degree of implant contamination, allowing to maintain a substantial sterility of the implant independently of its morphology. This may allow in the next future the use of bioactivation through plasma of argon to exploit the superhydrophilicity deriving from this biophysical process.

Effects of argon plasma treatment on the osteoconductivity of bone grafting materials

BACKGROUND

The osteoconductive properties of bone grafting materials represent one area of research for the management of bony defects found in the fields of periodontology and oral surgery. From a physico-chemical aspect, the wettability of the graft has been demonstrated to be one of the most important factors for new bone formation. It is also well-known that argon plasma treatment (PAT) and ultraviolet irradiation (UV) may increase the surface wettability and, consequently, improve the regenerative potential of the bone grafts. Therefore, the aim of the present in vitro study was to evaluate the effect of PAT and UV treatment on the osteoconductive potential of various bone grafts.

MATERIALS AND METHODS

The following four frequently used bone grafts were selected for this study: synthetic hydroxyapatite (Mg-HA), biphasic calcium phosphate (BCP), cancellous and cortical xenogenic bone matrices (CaBM, CoBM). Sixty-six serially numbered disks 10 mm in diameter were used for each graft material and randomly assigned to the following three groups: test 1 (PAT), test 2 (UV), and control (no treatment). Six samples underwent topographic analysis using SEM pre- and post-treatments to evaluate changes in surface topography/characteristics. Additionally, cell adhesion and cell proliferation were evaluated at 2 and 72 h respectively following incubation in a three-dimensional culture system utilizing a bioreactor. Furthermore, the effects of PAT and UV on immune cells were assessed by measuring the viability of human macrophages at 24 h.

RESULTS

The topographic analysis showed different initial morphologies of the commercial biomaterials (e.g., Mg-HA and BCP showed flat morphology; BM samples were extremely porous with high roughness). The surface analysis following experimental treatments did not demonstrate topographical difference when compared with controls. Investigation of cells demonstrated that PAT treatment significantly increased cell adhesion of all 4 evaluated bone substitutes, whereas UV failed to show any statistically significant differences. The viability test revealed no differences in terms of macrophage adhesion on any of the tested surfaces.

CONCLUSION

Within their limitations, the present results suggest that treatment of various bone grafting materials with PAT appears to enhance the osteoconductivity of bone substitutes in the early stage by improving osteoblast adhesion without concomitantly affecting macrophage viability.

CLINICAL RELEVANCE

Treatment of bone grafts with PAT appears to result in faster osseointegration of the bone grafting materials and may thus favorably influence bone regeneration.