Dentes: ( = teeth, dentition, upper and lower dental arches or arcades,
complete dental arcade)
 
Teeth are tools, weapons, sensory organs, and a means for nutritional
competence.  They are objects of beauty, long utilized for jewelry and to
enhance human appearance.  They have been carved into beautiful objects
of art, made into sporting equipment, and turned into delicate tools.
Humans have desired mammalian teeth throughout their evolution; wherever
human archaeological sites are found, so are the remains of tools and
jewelry made from the teeth of animals.  Ferrets, or rather their polecat
progenitors, use their dentition to explore their environment, defend
themselves against predation, warn away interlopers, perform sexual rituals
as a prelude to reproduction, play with siblings, carry and care for young,
excavate burrows, manipulate, move or carry objects, groom themselves, and,
yes, to kill prey and consume them.  Because of the obvious importance of
the teeth in nutrition and behavior, it is fitting the ferret's dentition
be discussed in detail.
 
Deciduous and Permanent Dentitions:
 
Ferrets, like humans and most mammals, have two sets of teeth during their
lifespan -- those being the deciduous and permanent dentitions.  While both
sets have incisors, canines and premolars, molars are only found in the
permanent arcades.  The deciduous dentition is designed to get the ferret
through early growth, when the skull and jaws are rapidly changing shape
and size.  Because the skull is small and still developing when the
dentition erupts, adult teeth would be too large to fit within the dental
arcades.  This problem is exacerbated by the need to wean the kit as soon
as possible; kits have almost explosive growth curves, which require a
tremendous amount of food to fuel.  Jills can provide only so much milk,
and as the kits grow, something more substantial is needed.  One solution
is for the jill to provide portable, condensed packages of nutrition to
the growing kits; otherwise known as prey carcasses.  This means teeth
are needed prior to cessation of skull growth.  These problems are met by
using a "throw-away" set of teeth; not as large, as hard, nor as durable
as the permanent dentition, which makes them cheaper from a nutritional
standpoint, but nonetheless capable of standing up to short-term use.
These "throw-away" teeth are the deciduous dentition, and they will be
discarded as soon as the skull is large enough to house the permanent
dental arcades.  (Synonyms deciduous dentition = baby teeth, deciduous
arches or arcades, deciduous dental arches or arcades, deciduous teeth,
dentes decidui, milk teeth, primary dentition, temporary teeth.  Synonyms
permanent dentition = accessional teeth, adult teeth, dentes permanentes,
permanent arches or arcades, permanent dental arches or arcades, permanent
teeth, secondary dentition).
 
The deciduous dentition needs to be in position within the first month of
the ferret's life, prior to when the jill begins to wean the kit.  Tooth
formation and growth (= odontogenesis) takes time, so the ferret is born
with some of the teeth already in place (= natal teeth).  Others have
crowns already formed so they can erupt within the first month of life (=
neonatal teeth).  In ferrets, the deciduous dentition mimics the permanent
teeth in that they have a similar appearance and function.  Most of the
ferret's deciduous teeth emerge at about 20 days, which is near the time
the jill first starts to supplement the diet with hard foods.  These
erupted teeth are mostly in place about a week later, and by day 40, while
the jill may still allow the kits to suckle; they are more or less able to
survive exclusively on solid foods.  Just after this time, the permanent
teeth begin to erupt, replacing the soft, temporary teeth with a rugged
dentition designed to last them the rest of their lives.
 
 
Basic Tooth Anatomy:
 
Each tooth is grown from an individual bud (= tooth germ) inside the
maxilla and mandible within blood-rich chambers that eventually fill
with bone to form the dental alveolus (= tooth socket). They grow from
the occlusal surface (= contact surface, biting surface) downwards,
forming the enameled crown first. When the crown is more or less
complete, the roots begin to form, and the tooth ultimately erupts
through the gums (= gingival emergence). Inside the tooth is the pulp
chamber, which contains the nerve and blood vessels that nourish the
dental tissues. These nerves and vessels extend through the root canal
to the apex (= root tip), and exit the tooth to attach to sources within
the mandible and maxilla (some teeth have more than one root, thus more
than one apices). The tooth is secured to the dental alveolus by the
periodontal ligament. This connective tissue is wrapped around the root,
connecting the cement-covered dentine to the alveolar bone and forming a
strong -- yet flexible -- joint. The periodontal ligament allows subtle
movement of the tooth during chewing and biting, which is perfect for
holding the teeth in position, but helping to shield them from severe
biomechanical stresses that could cause fractures under heavy load.
 
Teeth can be divided into two basic parts; the crown and the root.  The
crown (= corona) is the erupted portion of the tooth and is swathed in
enamel (the hardest substance in the body -- it will produce sparks when
struck by steel).  The root (= radix) is covered with a hard, bone-like
substance called cement (= cementum), and is attached to the crown at the
neck (= cervical region, dental cervix).  Under the thin layer of enamel
and cementum is the dentine (= ivory), which is the substance that makes
up most of the tooth.  Dentine is very hard and for centuries was the
material of choice for objects demanding durability, such as piano keys
or billiard balls (elephant tusks are dentine; the small enamel crown
present at eruption wears away rapidly with heavy use).
 
Bone, enamel, cement and dentine are all variants of the same biomaterial,
calcium hydroxyapatite, Ca10(PO4)6(OH)2.  These substances are composed
of a protein framework (= matrix) filled with ultra-fine crystals of the
inorganic salt.  The difference between them is in how the crystals are
formed and interconnected (including the matrix and the amount of water
molecules).  Tooth enamel, although nearly chemically identical to bone,
is far harder (which makes it far more durable).  However, hardness exacts
a price in brittleness.  While enamel is hard, it will easily fracture
under sudden impact, such as when a ferret falls and the tip of their
tooth strikes a concrete floor.  In these circumstances, enamel (or any
crystalline hydroxyapatite material, including bone) acts like a ceramic,
and fractures with the same patterns seen in broken glass.  In ferret
canines, this usually means the tip will fragment, and a partial U-shaped
flake of material will pop off the surface of the tooth (usually in the
front or just to one side; the size and position depending on impact force
and angle).  The tip actually shatters, and the flake is a portion of a
larger cone; imagine a long, thin slice out of the side of a funnel.
Ferrets also break off the tips of their canines by pulling at cage
doors, or in play, but the fracture patterns are usually different.  This
specialized tooth fracture mimics the sudden force applied when a B-B hits
glass, and is usually diagnostic of a fall (shattered tip, cone-shaped
flake).
 
The bumps, points and ridges on the top of the crowns are called cusps
(cones, tubercula dentis, tubercles).  The cusps on specific teeth are
diagnostic of species; that is, you can identify a mammal from the cusp
pattern alone, a trick discovered by Cuvier more than 150 years ago.  Thus,
while a root fragment has little or no zooarchaeological value, a crown is
quite valuable.  They can be traced to specific animals, yielding clues to
past ecology, hunting patterns, and environmental conditions, among others.
The cusps are modeled in dentine and covered with a thick layer of enamel,
creating a very hard projection on the tooth.  This allows the ferret the
ability to slice through tough connective and muscle tissue, and crush
bones to get to the valuable and nutritious marrow.  In the ferret, most
of the cusps are heavily modified into cutting blades, and are unsuitable
for food grinding.  Like cats, ferrets do not masticate their food; rather,
they cut it into chunks that can be wolfed down rapidly.
 
On the top of the jaw, along the line of tooth sockets, is the alveolar
ridge (= alveolar margin, alveolar process).  Covering this bone is the
gingivia (= gums, oral gingivia, oral epithelium), which is filled with
tiny blood vessels just under the surface.  These vessels feed the rapidly
growing epithelium (= outer skin) covering the gingivia, which explains why
gums look pink.  The gingivia has to grow briskly to replace skin cells
mechanically lost during predation and food consumption, to rapidly repair
injuries, such as biting the tongue or ripping the inside of the cheek, and
to help fight infections.  This exceptionally vascular region will bleed
from every tiny nick and scrape, which is often the cause of unnecessary
apprehension for new ferret owners -- it takes very little blood to impart
the appearance of serious injury.  Bleeding is normally self-limiting and
of little consequence, and benefits the ferret by washing pathogens from
the wound.  Serious cuts, or those which cause substantial or prolonged
bleeding, should treated by a veterinarian as soon as possible.  Whitish,
yellowish, bluish or grayish gums are good indications that the ferret is
ill, and should be evaluated by a veterinarian.  Large bumps along the gums
or on the roof of the mouth may be caused by infections or abscesses, or
could be a sign of an oral tumor, and should be treated by a veterinarian.
 
The health of the gingivia is necessary for the health of the underlying
bone.  The gingivia covers the alveolar ridge holding the teeth, and forms
a tiny pocket around the base of the tooth, called the gingival sulcus.
In a healthy mouth, the gingival sulcus is held close to the tooth enamel
by the gingival cuff, but with inflamed or infected mouths, the sulcus is
reddened and swollen.  This opens the gingival sulcus, creating a "pocket"
that can fill with bacteria and debris, exacerbating the original problem.
In short-term cases, such as when a piece of food scratches the ferret's
gums or the gum is injured during play, the inflammation is usually
self-limiting.  Most gingivitis is a result of injury or local
inflammation, and is self-limited, yet common.  Indeed, some odontogists
claim every mouth has gingivitis to one degree or another, which flares
and resolves with little notice.  In other words, at any one time you can
find some degree of gingivitis within a ferret's mouth, making them litle
different than any other mammal.  However unpleasant, in long-term cases
of gingivitis, the real danger is that periodontitis can set in.
 
Bob C
 
[Moderator's note: Part 2 of this article has already been received and
will appear in a future FML.  If you must have it NOW, please e-mail me
at the ferret-request address and I'll send you a copy.  (It's shorter
than this part.)  BIG]
[Posted in FML issue 3504]