Oh Really

P. gingivalis needs iron to survive.   Apparently it can dissolve stainless steel.   It increases growth in the presence of stainless steel.   Like dental appliances.  Braces.   Implant screws.   

Not to mention: Most pathogenic bacteria scavenge iron.      

In vitro corrosion studies of stainless-steel dental substrates during Porphyromonas gingivalis biofilm growth in artificial saliva solutions: providing insights into the role of resident oral bacterium

(insert roll-eyes and curse words here.)