Bill,  I have come across the phenomena of dead teeth before, and
discussed this with the late Bob Minney on many occasion while we have
been discussing comb tuning.

What you can find when tuning teeth is, you can get them just where
you consider them crack on, only to have one killed off by another
tooth further up the scale (or lower down) when you tune those.  There
must be a scientific reason why a certain frequency of oscillation in
one tooth can cancel out that of another close by, but it does happen
and we have found this common when tuning Polyphon combs; if it doesn't
stop the tooth dead it usually slows the resonation to just a few
awkward beats.

My advice to you would be to take the comb off and identify the dead
tooth and mark the underside with a felt marker, at which point take
some automotive masking tape, and run a strip along all the teeth tips
except for the one presumed dead.

Unless there is some carbon flaw in the steel (unlikely) there's a good
chance the tooth is gonna resonate.  If it does then might I suggest
a process of elimination until you find the culprit tooth that's
suppressing it, then ever so carefully scrape the lead resonator with
a craft knife, and remove only a fine scraping, the dead tooth should
start to come to.  Alternatively, if the dead tooth has a larger
resonator, this one can be trimmed ever so slightly instead, but I'd go
with the culprit tooth.

It's quite amazing what results can be achieved in this fashion.
I guess I'm leaving myself wide open to uber criticism here, but I have
had excellent results with this method -- a lacklustre plink-plonk flat
Polyphon can be tweaked in this fashion until it rings out like the
best of them.

If the tooth is indeed dead and sounds like a wooden leg when it's
plucked, then the only answer is a little remedial surgery.  Personally
I would be surprised if Regina let a box out of the factory that was
anything less than acceptable, as there is generally a much higher
frequency of uniformity of tonal sound quality than you could possibly
hope for from Polyphon.

Mark Singleton
Lancashire, UK