The untreated infected root canal is an environment
that provides micro-organisms with nutritional
diversity in a shifting pattern over time. The available nutrients
are mainly peptides and amino acids, which
favour anaerobic proteolytic species.
Whilst the microbial flora in an untreated infected
root canal may experience feast, in the well-filled root
canal there is predominantly famine. Most or all of the
original necrotic pulp will have been eliminated leaving
dry, barren conditions for surviving microbial cells.
These microbes endure a static environment and
starvation, but with some luck may encounter a serum-like fluid
transudate from the periapical tissue. The
species that persist are those that either have survived
the antimicrobial treatment, or have entered during
treatment and found it possible to establish where
others cannot do so. Where the coronal seal is defective
or missing, there is the possibility for new infection of
the root canal space.