Broken teeth are quite commonplace in animals.  In fact, they are so
widespread that researchers have been able to construct tooth fracture
frequency tables for many predators, including some species of mustelids.
Canine teeth are the most frequently broken, followed by premolars,
molars, and incisors.  For mammalian predators of all types, the chance
that they will damage, crack, or fracture one or more teeth during their
lifespan is about 25%.  However, the tooth fracture frequency is NOT
equal among carnivores.  For a long time, it was accepted that larger
predators had higher tooth fracture frequencies because they killed and
ate larger animals, with thicker, hardened bones.  This conclusion seemed
clear because tooth fracture frequencies were lowest in the smallest
predators and highest in the largest.  Also, it made intuitive sense:
heavy bones should damage teeth more often than light bones.  Recent
research, however, has disproved that idea, tying tooth fracture
frequencies to aging.  In mammals, larger predators tend to live longer
lives, so they have more time to damage teeth.  Because tooth damage is
accumulative, the longer you live, the more likely you are to hurt your
teeth.  Put simply, if a polecat lived as long as a lion, the tooth
fracture rates would probably be about the same, regardless of what the
other was eating.  This suggests older ferrets will have more tooth
damage than younger ones, regardless of diet (this is supported by
excellent data).
 
There are two basic types of dental damage studies -- those done by
scientists interested in veterinary applications, and those done by most
everyone else.  Many studies of dental damage in wild or feral animal
populations done for veterinary applications suggest dental injuries
are due to diet (bone eating), while those for most other applications
(zooarchaeology, paleontology, zoology) suggest dental damage is
multi-factorial.  The former studies are typified by data that quantifies
dental damage, but does little to investigate causation.  Suggestions
that diet (bone eating) is the causative agent for dental damage are
extremely simplistic (and shows an acute lack of scholarship).  Just
because a tooth is damaged in a bone-eating ferret, it doesn't mean
eating bone damaged the tooth; plenty of ferrets on a kibble diet have
damaged teeth.  Teeth could have just as easily been broken during
dominance fighting, in self-defense, while killing wildly struggling
prey, in a fall, while digging, from running into something, or during
some other type of accident.  In the case of pet ferrets, they regularly
break teeth trying to escape from cages, tugging objects, running into
things, or just falling from an owner's arms.  Teeth could break simply
because of aging; older teeth are more easily fractured as the blood and
nerve supply withdraws from the root and the space fills with dentine.
The danger increases if the root has died from injury or disease, or if
microfractures or cracks are present.  In other words, before you can say
a bone broke a tooth, you have to be able to prove it.  For example, in
an older veterinary paper, the dental lesions commonly found in sea otter
molars were explained by damage due to diet.  However, zooarchaeological
and zoological investigations showed the damage was not caused by diet,
but by the molar surfaces being scoured by sand, commonly suspended in
the water in surf zones.  Unfortunately, jumping to this type of
conclusion if far too common in dental damage studies performed for
veterinary applications.
 
There is a risk factor veterinary studies have never recognized: kibble
eating.  Normally, when a ferret chews a meat and bone diet, the
carnassials slice the food like a pair of poultry shears.  This produces
a wear facet on the contact surfaces of the cheek teeth, maintaining a
sharp edge that easily cuts through bone and tissue.  Kibble eating
ferrets have a different type of wear, from the crown down, which blunts
and flattens the carnassials.  This increases the surface area that comes
into contact with food, increasing the pressure on the tooth while
chewing.  I have seen SCORES of teeth from kibble-eating ferrets that
were cracked, broken, and worn down to the roots.  These teeth WILL
fracture, crack, and even split the crown (or what is left of the
crown).  If one of these ferrets chew a bone, it is probable the bone
will fracture the tooth and get the blame.  BUT, the damage was down
by kibble, a food highly defended by some veterinarians.
 
The point is, in ferret-sized carnivores there are numerous risk factors
that could cause tooth injury, eating bone is just one of many.  In terms
of pets ferrets, I know of NO instance where a ferret broke a tooth on a
bone, where it couldn't be shown the ferret had a history of biting or
pulling on cages, had taken a fall to a hard floor, or had other dental
problems.  I suspect nearly every instance where a tooth has been damaged
by biting into bone, the tooth had already been damaged, and if it didn't
break from impacting the bone, it would have eventually done so from
something else.  The real problem is a lifetime of minor dental damage
accumulating into a major dental fracture.  That doesn't mean a ferret
cannot break a tooth on a bone.  All I am suggesting is there are a lot
of unrecognized reasons ferrets break their teeth, bone being just one.
 
Bob C
[Posted in FML issue 4157]