Adherent endotoxin on dental implant surfaces: a reappraisal

Abstract

Abstract Osteoimmunology, i.e. the cross-talk between cells from the immuno and skeletal systems, suggests a role of pro-inflammatory cytokines in the stimulation of osteoclasts activity. Endotoxin or bacterial challenges to inflammatory cells are directly relevant to dental implants pathologies involving bone resorption, such as osteointegration failure and periimplantitis. While the endotoxin amount on implant devices is regulated by standards, it is not known whether commercially available dental implants elicit different levels of adherent-endotoxin stimulated cytokines. The objective of this work is to develop a model system and to evaluate endotoxin-induced expression of pro-inflammatory cytokines genes relevant to osteoclasts activation on commercially available dental implants. Murine J774-A1 macrophages were cultured on Ti disks with different level of Lipopolysaccharide (LPS) contamination, to define the time-course of the inflammatory response to endotoxin, as evaluated by RT-PCR analysis. The developed protocol was then used to measure adherent endotoxin on commercially available dental implants, packaged, sterile, that is in the "as-implanted" condition. Results show that tested dental implants induce variable expression of endotoxin-stimulated genes, sometime over the level expected to promote bone resorption in vivo. Results are not affected by the specific surface treatment, rather they likely reflect cares in cleaning and packaging protocols. In conclusion, expression of genes that enhance osteoclasts activity through endotoxins stimulation of inflammatory cells is widely different on commercially available dental implants. A reappraisal of the clinical impact of adherent endotoxins on dental (and bone) implant devices is required on the light of increasing knowledge on crosstalk between cells from the immuno and skeletal systems.