00:00
cells, and neurofibers that carry
sensations away from the tooth. The tooth
is embedded in the alveolar bone in a
socket by the periodontal ligament.
00:07
Periodontal ligament, unlike many
ligaments, is very very cellular.
00:13
In fact, it's even vascular. It has got a
number of different functions. It's often
called a periodontal membrane. But the
name membrane or ligament doesn't
really give a credit for all the functions
that it does. It holds the tooth in
its socket. You can see Sharpey's fibres
that embed into the alveolar bone,
holding that tooth in its socket.
And that periodontal ligament plays a role
in the eruption of teeth. It plays a role
in remodeling the bone, the alveolar bone
when different stresses are put on the
tooth. Under certain dietary situations,
it can start to break down. So you might
get a wiggly tooth in its socket and
the tooth might even fall out. It majors
proprioception forces on the tooth. It has
got an enormous range of functions.
Therefore, it's not just a ligament or
a membrane, at least in name and
structure it is, but unlike other
ligaments and membranes, it has this enormous
other array of functions. On the right
hand side, you can see a section taken
through where the enamel and the gingiva
join together. The enamel space is labelled
there because, as I pointed out before,
the enamel is missing, because it's highly
mineralized and this is a decalcified
section. The enamel is now acellular. Those
ameloblasts that I spoke about
earlier laying down the enamel are lost
once the tooth erupts. So you can't
repair enamel if it's damaged. There
are no cells there to repair it.
02:08
And some bacteria can actually secrete
enzymes that can dissolve that very strong
calcified material and create a dental
caries. But have a look at the gingiva, on
the left-hand component or left-hand side
of that right-hand section, on the gingiva,
there is typical oral or masticatory mucosa.
The gingiva is at a very
small part of the oral cavity that lies
against the tooth. And then on the enamel
side, you've got the epithelial
attachment labelled. The epithelial
attachment refers to the basal lamina or
the basement membrane of the epithelial
membrane or the cellular epithelial
surface you see there on the
inner aspect of the gingiva sitting up
against where the enamel would be.
03:08
That epithelial attachment, as I say,
is the basement membrane of that epithelium.
03:15
And it's stuck to the enamel by very numerous
numbers of hemidesmosomes. And then
just above that
enamel or that epithelial attachment is
a little space called the gingival
sulcus that sometimes gets embedded with
food debris and can often cause a number
of problems. So let me just summarize the
sorts of structures we've looked at