dental anatomy 6

8/7/2019 Dental Anatomy 6

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Lecture 6Part 1

The incisal and middle 1/3s and the distal height of contour is in the

middle of the crown .

1. The mesial cusp ridge here is high and adjacent with cusp tip .

2. The distal cusp ridge is lower than the mesial cusp ridge ; always

remember ,similarly to the maxillary canine ,the mesial cusp ridge

is shorter than the distal cusp ridge; this feature is important in

telling the surfaces of the tooth ,when you draw any canine from

the labial aspect ,when you see a cusp sloping ridge shorter than

the other ,then the short sloping ridge is the mesial part and the

longer one is the distal part . This is simply how we can tell the

side of the tooth, which is similar to

the approach that we follow ismaxillary canine.

3. The incisal outline is 1/4 to 1/5 IC

height, the part present in the cusp

tip is around 1/4 -1/5 the crown

height .

4. The mesial outline is straight while

distal is convex ,both converge

slightly toward the cervix.(as we go

down in the root the tooth should be

converged ,it's not straight )

So incisors and canines are wider incisally than cervically . So the two

,distal and mesial, outlines they converge cervically . The mesial height

of contour is just below MI angle ; the Distal height of contour is

between incisal & middle thirds. Mesial height of contour is lower than

the distal height of contour, generally its between the incisal third and

middle third of this tooth.

5. This tooth also is similar to incisor and maxillary canine, it'sformed by the fusion of 3 separate lobes.

y the middle lobe represents the tip of the cusp and

y mesial lobe

y and distal lobe



6. Root is conic

¡

and it's blunted ;Mesial inclination from cervix to

apex ,as we go from cervix to apex we find some mesial inclination

; the crown appears tilted distally in relation to the root long axis

;if you draw a line throught the root is looks a bit inclinated, not

straight .

This t ooth, mand i bu ¢ ar cani n £ ,has the l ongest crown of

all teeth; it measur es around 11mm from the t op of the

root t o the cerv ical li ne..Max ill ary cani ne is also l ong but

still shor ter than mand i bul ar .

The cusp ti p is less poi nted than max ill ary cani ne.

From th¤

lingual asp¤ ¥

t :

1¦ The tooth has two marginal ridges ,mesial and distal ,and has two

fosse,mesiolingual and distolingual ;this means that we have aridge that separated the two fosse ,this ridge is the LINGUAL

RIDGE.

2§ These two fosse are shallower than the maxillary

fosse which are deeper. This is something general,

if you remember we said that fosse in maxillary

teeth are deeper than fosse in mandibular teeth,

even in incisors the lingual fossa is deeper in

maxillary incisor than mandibular ones.

3§ Pits or grooves are rare .

4 § Root narrower lingually than labially ,from the lingual side we can see the sides of the tooth,

because the root is slightly narrower lingually from labial ,it

means a cross section of the root will not be

symmetrical ,the labial part will be thicker than the

lingual in this cross section.

5 § Distinct longitudinal depressions on the root,

clearly evident in the picture. These extend down

to reach the cervical line or the proximal surfaces.

Sometimes we might have a CENT

RAL CANAL in the root,and probability of having a central canal in the root is

also 30% similar to the probability of find it in a maxillary

canine. That's why any dentist working on a root canal treatment, he

/she has to remember that there is a possibility in 30% of the population

to have a two canals.



Fro ̈

the mesial aspect :

1. Cusp tip with long axis of the tooth, if we draw a line dissecting

the root in the middle this line passes through the tip of the cusp.

Remember this feature is not the same in maxillary canine ,if you

remember we said : the maxillary canine if we draw a line dissecting the

root ,this line will be lingual to the tip of the cusp (or the tip of the cusp

will be labially to that line );but in mandibular canine this line pass in the

tip of the cusp and some text books say that this line pass lingual to the

cusp(completely opposite) ,but in most of cases the tip of the cusp is

exactly in line with the labiolingual dissecting line.2. The height of contours labially and lingually are almost at same

level located ,near the cervix.

3. The root is very broad labiolingually, wider than mesiodistally;

that's why if we make a cross section through the root it will not

be circular, it will be prolonged, it has the labiolingual diameter

longer than the mesiodistal diameter.

From the distal side: is similar to mesial .

From the incisal side :

1. The mesial and distal halves are more nearly symmetrical , this

means that the distal and mesial parts are almost equal ;

This is not similar to maxillary canine,you remember we said that the

mesial portion is thicker labiolingually than distal ,and the mesial

portion is shorter mesiodistally than the distal portion ;in other words

tooth halves are not identical ,they are more identical in mandibular

canine.

2. Less bulky appearance of the incisal edge ,

This means the incisal part of the tooth is almost thin, but in maxillarycanine the incisal part is thick.

3. Vertical lobe grooves are less marked

If you remember we said that we have labial grooves on maxillary

canines formed by the fusion of two lobes ,so that's why we have on the

maxillary canine LABIAL GROOVE and at the side of this labial groove



we have two depressions ,these depressions are shallower in mandibular

canine,more evident.

Pulp is similar to maxillary canine.:

y Double convex lens shape

y Very narrow MD

y But wide labiolingually

This is a cross section of root canal .it is elongated and in case of having

two canals you will see two separates canals.

Fr om slide 10-13 sho © t he arch t r aits o

canines... T his is a summary o

© hat © e've talked about it's very impor tant, r ead it and kno © it.

Canine r elationship:

In the last lecture we talked about the incisal relationship ,we said we

have Class I , class II and class III. And we discussed what we mean by

overjet and overbite.

We'll talk about the three classes of

canine relationship: class I ,class II

and class III .

** Remember something: the

maxillary incisors are wider than

mandibular, for this reason you

should imagine than mandibular

teeth all come under maxillary ,

Look at the picture : we have maxillary incisor, wide ; and the

mandibular incisor, more narrower ,you can notice there's a space

between the two teeth while occluding .Because of that in any

apposition of any teeth ,the mandibular will be more mesial than the



same tooth in the maxilla ,thus forming a space; for example if you take

the mandibular first premolar ,this should be more mesial than maxillary

first premolar ,why?because we have diff erence in the incisals ,because

the incisal in the upper jaw are wider than in the lower jaw ,so all the

posterior teeth will be nearer to the middline than maxilla.

Because of this we have class I ,class II

and class III .

1 in class I relationship :

notice that the mandibular canine is

located between the maxillary canine and

lateral incisor ;

i n other word s : the set of the max ill ary

cani ne is l ocated bet ween the mand i bul ar

cani ne and the mand i bul ar f i r st pr emol ar .

2 now ,if the tip on

mandibular canine is

located more anterior to

this position ,it's class II .

3 If it's located more

posterior to this position

,it's class III .

See here ,for example, the tip of the

maxillary canine should be exactly

between the mandibular canine and

first premolar ,but because it's

located more anterior to the original

position ,we call it CLASS II.

If it was located more posterior ,like

in the third picture, you can see the

tip of the canine is located posterior

,so it's CLASS III.So simply ,we actually can give the canine relationship based on the

location of the canine tip in relation to the mandibular teeth.

Done by : Sara Ibd i wi

Maxillary canine

Mandibular Canine

dental anatomy 6

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