Message Number: YG6174 | New FHL Archives Search
From: RRC
Date: 2001-08-07 09:33:00 UTC
Subject: Bob C: Ferret Dentition, part 1

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