My "aging ferrets" post brought in a slew of questions regarding teeth, so
I am dumping my normal format to answer them quickly.
 
Regarding missing incisor teeth (the tiny front teeth): Not a problem.
These teeth have little function--mostly holding or gripping--which
translates as functionless in a pet.  I would worry more about what the
missing teeth are saying about the condition of the mouth.  Is there an
infection you don't know about?  Did the teeth break off, like in cage
chewing, or did they pull out or fall out, like what happens when the
ferret has a jaw infection?  If the mouth is healthy, the loss of the
incisors in inconsequental.
 
Regarding missing canines (the vampire-like fangs): Not a problem as long
as the ferret is a house pet and lives with neutered ferrets.  These teeth
are designed to kill prey and for personal defence; both not really
necessary in a home-maintained animal.  Often, one or more of the canines
are broken off, usually from falling to a hard floor, or as a result of
biting parts of a hard metal cage.  Normally, only the tip of the tooth is
broken off, but on occasion, the entire tooth may break at the root.  In
those instances where the pulp cavity is exposed, there is a danger of
infection, but in most cases, the tooth will fill the root canal with
dentine on its own, and while not actually repairing the tooth, will at
least prevent future infections.  A broken tooth needs to be watched
carefully for signs of infection, and at the first sign (nasty breath, gum
swelling or discoloration, bumps under the gum, pus or other drainage,
etc), get to a vet as soon as possible.  What you don't want is a long-term
bone infection, which may never be cleared up or cause the death of your
ferret.  If no symptoms, it is probably ok to wait for your next scheduled
vet visit, such as for shots, and then point out the broken tooth.  A
particularly bad tooth might have to be cut off or pulled.  It is usually
unnecessary to polish or smooth the tooth.
 
Most rescued ferrets missing their canines had them cut or pulled by a
previous owner.  I do *NOT* advocate pulling or cutting these teeth, which
is unnecessary in a pet; even bad nasty biters can be conditioned to stop
biting if placed with loving owners.  This condition usually is found in
animals rescued from a non-pet industry breeder, or occasionally one used
as a laboratory animal.  While the temptation to harshly judge the pulling
or cutting of canines in a lab or breeding environment is great, I usually
don't do so because it is sometimes the only way to quickly and safely
handle large numbers of poorly socialized animals (I don't like it; I just
understand why).  It is also quite commonly found in non-domesticated
exotic animals that use their teeth to prove their points (which I also
understand having been biten once by a playful river otter and getting 22
stitches on my bodacious butt).  Basically, while the loss of canines is a
drastic and oft-misused approach, I would support it's use in those
occasional instances where physical trauma or brain damage prevents any
other technique from training a ferret not to bite.  I have been badly
chewed on numerous occasions by ferrets (and mink, as the hole in my ear
demonstrates), and I would think that as an extreme last resort, having a
vet medically and painlessly remove the canines would be acceptable on a
case-by-case basis.  Losing a few teeth is much better than losing a head,
if you get what I mean.  Sometimes you do what you have to do.
 
Regarding tooth cleaning.  I don't do it, I don't need to do it, and I have
never had it done.  I am the wrong person to ask because I believe
prevention is better than curing, so I give my ferrets a natural tooth
brush before it becomes a problem.  My natural tooth brush is, of course,
bone, and to a lesser degree, intact body carcasses (mostly mice, which I
buy frozen from a herp dealer).  Chewing fur, skin and bone naturally
cleans the teeth of carnivores, leaves their mouth in a "neutral" state
which prevents the formation of dental plaque, and satisfies their
psychological need for chewing.  If you don't like it, don't do it.  I do
it and it works well.
 
Regarding broken molars.  Ok, these are a problem.  The only way your
ferret can eat food is by cutting it with the cheek teeth into small enough
fragments that can be swallowed whole.  They don't chew food to a paste,
like we do, or cough it up to rechew like cows.  They simply scissor cut it
to small chunks and swallow.  Damage to these cutting teeth will impair
your ferret's ability to eat.  Look at these teeth every couple of weeks,
and if you see cracks, cavities, excessive wear, or fractures, see a vet
for their opinion.  A ferret missing these cutting teeth is doomed to a
soft diet, so don't wait or get used to making my chicken gravy.
 
Regarding a broken jaw.  Some vets pin these immediately regardless of the
type or extent of fracture.  Others allow the jaw to knit on it's own, and
help the process by putting the ferret on a soft diet.  Most decide which
is necessary on a case-by-case basis.  Most fractures in ferrets are *NOT*
stabilized (casted or pinned) and the ferret heals naturally in a month or
so.  Jaw bones, if not crushed, tend to "splint" themselves, and the ferret
eats on the side of the mouth that isn't sore.  In 2 weeks, the jaw is
softly knitted together, and in 4 to 8 weeks, the jaw (or most bones) has
healed.  Sometimes a tooth will be lost where the jaw was broken and not a
lot can be done about it.  If you suspect your ferret's jaw is broken (or
any other bone), see a vet immediately; you need an X-ray!
 
Finally, the health of the mouth is of extreme importance.  Don't hesitate
to see a vet if you suspect a problem.  Rotten or sour breath, strange
swellings, pus or other drainage, swollen faces, jaws that don't close and
other obvious signs of damage require expert medical care and soon.
Hesitation could mean a serious bone infection, damage to facial nerves,
loss of teeth, or even septic shock and death.  Besides, a ferret uses it's
mouth to manipulate the environment, to feed, to play and to communicate
emotional states, so allowing a potientually painful or disabling problem
to go on unchecked is cruel and unethical.  Don't wait; see a vet.
 
Bob C and 19 MO' Officers of Omnidirectional and Omnificent Oopsies
[Posted in FML issue 2636]