I have to take your word on the risk of lingual nerve damage in the
case of an extraction.
    I must confess curiosity as to what your role in this scenario is.
Your language suggests medical training; however I personally doubt a
dentist would consider "eugenol management".
    Whether the risk of extraction is undertaken depends upon the perceived
risk.  You imply the third molar is at least partially impacted, but
this is not clear.  Furthermore, I cannot assume that root canal is
"overkill" if extraction is not feasible.  Of course the root canal may
well not be feasible either; however the consequences of untreated
abscess in this area are not insignificant.
    BTW, if there is exudate from the pulp chamber there is abscess; if the
pulp is vital in this case it will not long remain so.
    If root canal and restoration is not possible I see no option other
than extraction.  The neglect of this situation during the period when
simpler treatment would have been possible seems to me to preclude
successful treatment otherwise, and have put the patient in a position
where a certain amount of risk is unavoidable.

Steve

Due to proximity of adjacent tooth, third lower molar caries resulted
in a communicating lesion for many years, but no pain, with occasional
taste of exudate. 3 months ago 4mm piece broke off exposing interior of
tooth. With risk of lingual nerve damage on exicision in an adult, the
preference is to keep the tooth, but closing the cavity completely is
prob. neither possible (due to proximity to gingival surface and access
difficulty from adjacent molar ) - or advisable due to likelihood of
pressure bildup.
What are your preferred solutions ?

1) Exicse (declined, prefer current management with cotton filling
placed w. explorer)

2) Rootcanal (declined, overkill for a third molar, would also leave
the side open)

3) Eugenol management ?

4) Management with new compound less irritating to oral mucosa than
eugenol ?

5) Placing filling after placing a wire in split section so that a
canal can allow continued exudate flow?

Thank you for your insight. The pulp is definitively vital, cooling
pain disappears at once, there is
only light tapping pain. One would think there is a low abscess risk as
long as there is an opening..