Had many emails on how to interpret some of the sections from our “fracture case” on TDO. I forget I’ve been looking at biofilms for almost 15 years so fail to remember how confusing they can be…..I’ll publish a series that may help. In most cases, biofilms look different from planktonic organisms. Biofilms enmesh themselves in EPS—which looks like melted wax or molasses…you can’t detect anything that looks cellular at all. Many times the biofilm itself is mistaken for the smear layer—it is so amorphous-looking. In the SEMs, they appear to be constructed “in layers”—layer over layer. In the SEM alone, it frequently is not possible to tell whether you are observing a biofilm or dentin because of the nature of the EPS.