Dental Anatomy Introduction

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Dental anatomy has a very specific group of basic terms which are essential to its understanding
and communication. The objective of this tape is to define and illustrate some of these
basic terms. We will start by identifying the structures of an individual tooth. Then
we will briefly illustrate the surrounding or supporting tissues. We will identify the
adult teeth and the terms that relate them to the mouth and to each other. Then we will
combine some of these basic terms to more specifically describe the areas of these teeth.
If we look at a cross-section of a tooth we can start to identify some of the individual
structures. The most common one is the enamel which is the hardest substance in the human
body and covers the visible portion of the tooth. The dentin makes up the bulk of the
tooth, the second hardest tissue in the human body. It covers up the enamel all the way
throughout the tooth, it covers the largest portion or the largest area of the tooth.
Then we have the cementum which is a little bit softer but still a hard structure of the
tooth and this covers the root of the tooth from the crown all the way to the tip of the
root. This is the cementum of the tooth.
The fourth main structure of the tooth is the pulp which is composed of the blood vessels
as well as the nerves and lymphatics and the variety of primitive connective tissue and
this is housed in what we call the pulp cavity, a chamber with inside the tooth that is surrounded
completely by dentin. Actually the pulp can be divided down into two areas or our pulp
cavity can be divided into two areas. One is the pulp chamber which consists of that
area in the crown portion of the tooth. It's usually a little wider, a little broader and
the second area is our root canal which is generally a narrower canal which traverses
down the root of the tooth.
Actually we can divide our tooth into two basic areas. One is the crown of the tooth
which is that portion of the tooth which is covered with enamel.
And we can divide it into the root of the tooth which is that portion of the tooth which
is covered by the cementum.
When we come to the tip of the root we have a specific term which is our root apex, it's
like the apex of a triangle, it's the tip point of the root. Actually we also have another
term at the apical area of the tooth and this is the foramen or the hole in which our pulp
exits. This is called the apical foramen.
Where our hard structures join in the tooth we also have terms which combine the two hard
structures. In this area here we would have the cementoenamel junction sometimes abbreviated
as C-E-J, the cementoenamel junction.
Where our dentin and enamel join we have our dentinoenamel junction or frequently the D-E-J.
Then our third junction area is our cementodentinal junction, the area in which our cementum and
dentin join.
If we look at a cutaway section of some teeth, we can define the periodontium or the supporting
structures of the teeth have four basic parts that make up our periodontium. First is our
gingiva or the soft tissue which we usually see in the mouth.
Underlying our gingiva we have our alveolar bone which is the bone that makes up the socket
or the surrounding area of the tooth. Alveolar bone.
Then we have what we call a periodontal membrane it's a soft tissue or membrane a ligamentous
membrane which connects the tooth and the alveolar bone. Our periodontal membrane. There's
actually a fourth structure to our periodontium is a part of the tooth and that is our cementum.
The cementum connects the periodontal membrane to the hard structure on the tooth and then
the periodontium membrane is connected to the hard bone so the cementum is considered
part of the periodontium or the supporting apparatus of the tooth. If we were actually
to look to the crown, sometimes this crown portion is broken down into two areas. What
we call the anatomic crown is as we have described that portion of the tooth which is covered
by enamel. This is often broken down into another crown and that is the clinical crown.
The clinical crown is usually that portion of the tooth which is above the gingiva.
If we were to look to a mouth, we would find that normally and usually the clinical crown
does not go all the way down to the C-E-J or down to the cementum. The clinical crown
is about 90% of the enamel but doesn't go all the way down but again this may vary.
In other instances, such as in children, we may find that the clinical crown is only half
of the enamel.
Whereas in a case where we have had gingival surgery the clinical crown may be exactly
the same as the anatomic crown in fact, in this view, we can see a portion of the cementum
or part of the root here. So the clinical crown varies within the mouth.
When we look to a skull there are several more terms that we can illustrate and identify
here. Our upper jaw is referred to as a maxillary jaw and the teeth in here are maxillary teeth.
We will attempt to use this term rather than upper and lower teeth or upper and lower jaws.
Our upper jaw will be a maxillary jaw with maxillary teeth. Our lower jaw will be referred
to as our mandibular jaw, mandibular bone, mandibular teeth. We have eight individual
teeth we want to identify at this time. And we'll start right up with the central incisor.
This is the one most commonly seen in a person's smile and it's in the center. There's two
of them actually but we're going to consider the eight of them which are basically the
same here. So we have a central incisor and the one just lateral to it is also an incisor
and it's called a lateral incisor. These incisor teeth particularly the central grow more prominent
in our rodent animals, in our rats and beavers and what have you. But our teeth are all basically
the same in size.
Our third tooth here is a cuspid or canine tooth again this is the one that gets more
prominence in our cats and dogs and lions and tigers, our carnivorous animals. This
is characterized by having just one cusp, one sharp cusp on it and it's called our cuspid
tooth. We start going around the arch here. We come to what was called our first premolar
tooth or our first bicuspid tooth. We actually have two bicuspids and they are called first
and second so the first one would be considered our first premolar, the first bicuspid tooth
and this is characterized by having two cusps that’s where the term bicuspid comes from.
It's got two individual cusps on it, our first double cuspid tooth. We have a first premolar
or biscuspid and we have a second premolar or second bicuspid. Then our last three teeth,
posterior teeth are molars and these have multiple cusps on them and these are identified
in the order in which they are. We have a first molar,
and a second molar,
and we go back to a third molar. Now these eight basic teeth are duplicated
in other portions of the mouth. On the maxillary, on this side we have the same eight teeth.
Except on this side we would be calling them left, the left central incisor. In fact, we
can combine more terms to it. This would be a maxillary left central incisor and then
go right on back. On the mandibular teeth, we again have the same eight basic teeth but
we would be calling them mandibular central incisor, and more specific mandibular left
central incisor so we actually have four terms which are used to describe our teeth here
whether they are a right or a left whether they are maxillary or mandibular or whether
they are central or a lateral or an incisor and what have you so here we would have maxillary—or
mandibular left central incisor. These groups of teeth since they're duplicated
four times or divides our mouth in to what we call quadrants or quarters. We'll have
a maxillary right quadrant composed of our eight teeth in the maxillary right area. Maxillary
left quadrant which is a quarter of a section of these eight teeth here. And then the same
on the mandibular. Mandibular right quadrant and mandibular left quadrant. These are often
times used in referring to various procedures that we do within the mouth. Another general
area of breakdown that we have in these is what we call anterior and posterior teeth.
Our anterior teeth are generally our six front teeth or the six teeth that are most anterior
in the mouth. This composes are central incisor, our lateral incisor and our cuspid. These
are our anterior teeth. So we have maxillary anteriors which would be these six right here.
And we have our mandibular anteriors which are the six on the mandibular and the teeth
behind these are simply called posterior teeth. This is composed of our bicuspids, two bicuspids,
and our three molars. So we have our right maxillary posterior teeth. We have our right
mandibular posterior teeth. So we divide them in to anterior and posterior right in between
our cuspid and first premolar. Actually these teeth have numbers and when they are referred
to in our writings as far as our charting and our literature that we use to identify
these, they're commonly referred to by number. Instead of having to say maxillary right third
molar this particular tooth is known as tooth number one.
And then we will start to number around the arch until we come to 32 which is the total
number of the teeth so let's get the basic orientation of how these number. Our maxillary
right third molar is tooth number one and then we just start right down the line the
maxillary left, right,… Let's see, our maxillary right second molar would be number two. We
go right on down the line until we come to our maxillary right central incisor which
would be eight and we continue right around until we come over to our maxillary left third
molar which is number 16. So they're right in order right around 16 of them on the maxillary.
Then we drop directly below this to tooth number 17 which is our mandibular left third
molar. This is number 17. You've got to remember two teeth in the mouth for this numbering
system. One is your maxillary right third molar and the other is number 17 which is
your mandibular left third molar, number 17, and then we'll just number right around. For
a while it'll take a little time and you'll be counting on your fingers and toes and in
your mind and what have you to get these numbers down but the numbers of these teeth have to
become just as common as the letters in your name because you'll probably use them more
than you will writing your own name. When you get involved in dentistry these are written
many times every day. The numbers of these teeth. Number 32 then would be directly below
one and that is our maxillary right, pardon me, our mandibular right third molar would
be number 32 but the two key ones are just our number one and number 17 you want to remember
those and you could probably fit the rest of them in a pattern just by counting.
Let's take a look at the individual surfaces on these teeth. They each have names as well
as numbers. Our number one surface is our mesial surface. This is the surface closest
to the midline and in this instance the number one surface of our two maxillary central incisors
are contacting each other. It's the only surface in the mouth where we have this occurring.
The number one surface or mesial surface is defined as that surface which is closest to
the midline or as we go to the posterior it would be that surface closest to the anterior
or to the front of the mouth and the midline. It would the surface closest to the midline
here. Our number two surface is our distal surface and it's simply defined as that surface
which is away from the midline or towards the posterior of the mouth as we go towards
the posterior and it would be the surface opposite that of the mesial.
Our number three surface has three terms really. This is the surface which we see most commonly
and it’s the facial surface that surface which is on the face side of the teeth. This
is the same as the maxillary and mandibular all these are actually. So we call it facial
all the way from number one all the way around to number 32 the side, surface which is closest
to the face that's number three surface. This also can be broken down into two different
terms, the facial surface in the anterior six teeth is called the labial surface.
It's the number three surface again for record purposes.
And the facial surface in our posterior teeth is generally called the buccal surface. These
buccal and labial terms are probably more commonly used in the facial surface although
facial is perfectly acceptable and will be found in the literature too. It divides it
down into the posterior surfaces being called buccal here and the anterior six teeth being
called the labial. Our number four surface is our lingual surface and that's the term
in relation to the tongue surface. Most of these are in relation to the anatomical terms,
most of the anatomical terms of the tongue are called lingual and the surface next to
the tongue is a lingual surface. We might drop back a little bit when we're talking
about the number three surface, the labial surface, this is referring to lip that part
which is under the lip, 'labial' is again an anatomical term which refers to much of
our anatomy in the lip. 'Buccal' is a term which refers to cheek much of our anatomy
in the cheek is referred to buccal as far as our nerves and our arteries and our muscles
and a variety of other things are buccal so this is where the term for this comes. If
we go to our number five surface, we're talking about the biting surfaces on these teeth.
And in the posterior this is called an occlusal surface that's with our bicuspids and our
molars. Number five is the occlusal and in the anterior where we are involved more with
the cutting edge and the anterior six teeth we're talking about incisal surfaces. So again
we have two general terms that are referring to surface number five. Incisal surface in
the anterior and the occlusal surface in the posterior. Both of them referring to our biting
surfaces.
Section 13 in Kraus's textbook deals with alignment and articulation of these teeth.
This is something we ought to get a basic orientation to before we start studying individual
teeth because total alignment and articulation is important in relation to the individual
anatomy of these teeth. For instance, if you were to look to alignment of these teeth you'd
find that they don't sit one right atop of another like blocks. Like our anterior for
instance are at angles and our maxillary anterior teeth are coming forward considerably and
our mandibular anterior teeth are doing the same thing and these vary somewhat within
jaws.
We can look to another skull and see the variation of our maxillary anteriors that are at a very
strong angle that they come forward and out and this varies significantly the anatomy
of the teeth. This is one of the reasons that they're in this particular anatomical structure
and again the mandibular teeth are coming forward in a different area. You'll note these
teeth will occlude or to bite differently. Here we're… well we'll show it in this direction.
Our maxillary teeth are forward of our mandibular teeth. Our mandibular teeth are biting up
on the lingual surface now of our maxillary teeth and even in our posterior area here
we have a lap of these teeth. They're not one on top of the other and the teeth are
biting in between each other.
If we were to look at a mandibular arch which is the whole arc of our mandibular teeth here
we'll see that it's an even semi-circle, but this is a very specific arc that's created
from these teeth and the teeth alter their anatomy to fit into this pattern and as we
study them we continually point to these various alternations that exist and even if we were
to look at the posterior teeth in here we'd find that they're not coming straight up.
They're coming at a rather sharp angle. One of the diagrams that are… illustrate this
quite nicely. As far as varying angulations of the teeth we have our anterior teeth shown
here to be angling, our maxillary anteriors rather significantly in a forward direction.
Our mandibulars, we can see our coming in a rather specific forward direction. It also
shows posterior teeth. These are also tipped and different teeth are tipped at different
angles. This is all designed for a rather complex functioning mechanism. If we were
to look at the maxillary teeth from the posterior as if we were sitting back on the tongue looking
out we would see that these maxillary teeth are angled rather significantly outward towards
the facial surface. They have very definite angles and this whole complex angulation goes
into the anatomy and hence forth into the function. Again we're sitting on the posterior
tongue looking forward on this mandible and we'll see that are mandibular teeth are at
a significant angle tapering in. This gives us rather good support in our mandibular bone
as far as the function and also meets and relates to our maxillary teeth rather significantly.
We have identified the surfaces of our teeth in the skull. Now let's look to a diagram
and see if we can identify them a little clearer here. We have superimposed a box over this
incisor to help us clarify these surfaces. We can start with our number one surface which
is our mesial surface and this is a whole area of the box that would be on the mesial
portion of the tooth here. Our number two surface would be our distal surface which
again would take of the area of the box in this area. Our number three surface is our
labial surface. Sometimes called a facial surface but I think more commonly in the anterior
here a labial surface. Our number four surface is our lingual surface covering the whole
lingual portion of the tooth. And our number five surface is our incisal surface which
is characteristic of our anterior portion of the mouth, our anterior teeth, the surface
is called incisal.
Now one of the advantages of our box is that it helps us to identify the junctions of these
surfaces. And where these surfaces join we have an angle. This is called a line angle.
A line angle is an angle formed at the junction of two surfaces and this is given a specific
name according to the surfaces that make up this angle and in this instance we have a
mesio – we note that I said 'o' you drop the 'al' on the term 'mesial' when you say
'mesio' – and then the next surface which is the labial line angle. Then mesiolabial
is one word. So we have a mesiolabial line angle. Actually this could be called a labiomesial
line angle but custom usually identifies the mesial surface first and our workbook has
a little description as to how these are more commonly or frequently referred to. It's not
wrong to say it, by saying a labiomesial but it's more customary to say the mesiolabial.
On the distal we have the same basic thing. We have the distolabial line angle and the
same on the two lingual line angles. They'd be named according to the two surfaces that
adjoin them. This also gives us a line angle on our incisal and in this area here we would
have our labioincisal line angle. This angle here would be identified by the
mesioincisal line angle and the same on our on our lingual and distal angles.
Now where three of these surfaces meet, we have a point angle and the point angle again
is named where the three surfaces make it up. And again this would be basically one
word. We would have a mesial, labial, incisal point angle and again we change the mesial
to 'o' on both the mesial and labial and use the 'al' on the incisal. So we got a mesiolabioincisal
point angle right here and the same exists for our other point angles. This one would
be our mesiolinguoincisal point angle. So this gives us an identification of our surfaces,
our line angles, and our point angles. Let's look to a posterior tooth here.
We have the same thing basically on the posterior teeth except we've got two different named
surfaces. We've got our buccal surface and the surface number five here now is our occlusal
surface and again where these surfaces join we would have our line angles but they would
be named according to the surface. So this line angle here would be our buccal occlusal
line angle and the same with the line angles around the rest of the posterior teeth. We
would have our mesial occlusal line angle and then we can go our point angles again
and again this is identified by our three surfaces. Here we would have our bucco –
that would be an 'o' now – our buccomesioocclusal point angle and the same would exist for basically
all the rest of our point angles in the posterior teeth. These are more frequently referred
to, these point angles in the posterior teeth because posterior teeth, uh, are more square
or rectangular and these angles are sharper and much more frequently we refer to our point
angles in our posterior teeth.
Another way we can help describe these teeth is by dividing them into thirds which is a
fairly common way of describing portions of our teeth. If we look to a labial surface
of an incisor here, we can divide it into thirds again according to the general areas
in which we're, surfaces in which we're talking here. So we've got an incisal third, we've
got a middle third, and we've got what's called a cervical third. Now this term 'cervical'
refers to the general area of the teeth around the cementoenamel junction. And actually the
cementoenamel junction which we had described before is often referred to in three ways.
One is by the cementoenamel junction, the other is by the abbreviation C-E-J and the
third which is very common, is called a cervical line so the cementoenamel junction has another
term which is called cervical line which generally describes the area of the C-E-J and so we've
got the term 'cervical' referring to this area of the teeth. We have here a cervical
third of the crown, we've got a cervical third of the root, a middle third of the root, and
an apical third to the root. These terms help us give us handles in case we want to describe
certain things that may happen to the teeth. We may have a fracture which may be a horizontal
fracture and it could be through the middle third of the tooth or the incisal third. It
helps us to identify them. If on removing the tooth we were to break the root, we possibly
could break it in the apical third. And we refer to these portions of the teeth generally
by the thirds. While I've got this diagram also I might combine a couple other terms.
When we're talking about fractures, we could have a vertical fracture in the tooth which
would allow us to combine some terms here and this would be called a vertical fracture
in which we have a fracture in the incisal cervical direction. Sometimes it would be
called a incisal cervical fracture. If we had a fracture in this direction, we may call
it a mesial distal fracture. Sometimes in measuring these teeth we'll measure the distance
from the incisal to the cervical. This will be our incisal cervical distance and we have
the same thing on the mesial distal. We've got measurements that measure our mesial distal
distance. So these surfaces can be combined in many ways to aid us in describing these
teeth.
Let's look at the labial view and divide our tooth into thirds in a different direction
here. We've got a third here which would be a mesial third of the crown, a middle third
to the crown, and a distal third to the crown. We may have a fracture which involves the
mesial third of the crown and we may have some caries or something that is in the mesial
third so again these are just descriptive handles that we can use in describing these
portions of the teeth. Let's look to a mesial view. We can also divide it down here. We
have a labial third, a middle third and a lingual third to our crown and actually the
roots are basically the same thirds. These are basically by the surfaces that are involved.
If we look to our posterior teeth we find that they're divided in basically the same
thirds except we have a little different terminology on a couples surfaces so we'll use those surfaces
in dividing them into thirds. The first one is our occlusal third, our… instead of having
an incisal as we have in the anterior and the posterior, we're talking about our occlusal
surface so we have an occlusal third, a middle third, a cervical third of our crown, a cervical
third of our root, and then the middle third again which we probably best identify as middle
third of our root, and then an apical third. If we were to look to the buccal surface and
divide these teeth from mesial to distal into thirds then we would have a mesial third,
we would have a middle third again, and we would have a distal third. If we look to the
mesial surface of our posterior tooth, we'll find that we have a buccal third, the surface
being the buccal surface, we've got a buccal third to our crown, a middle third, as well
as our lingual third. We hope that these illustrations and definitions have given you a better grasp
of some of our basic dental terminology. These terms are essential to the communication of
dental anatomy and important before we start studying the individual teeth.
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