dental anatomy lecture:4

8/6/2019 Dental anatomy Lecture:4

1/10

Dental AnatomyLecture 4


2/10

Last time we finished talking about max. permanent 1st

molar ,, bs 8bel ma nnt8el

lmwdoo3 jdeed , the anatomy of the max. 1st

is very important & in fact I put many

questionz in the final & practical examz about the details and anatomy of the

occlusal surface of this tooth . This tooth has a very complex occlusal surface so, we

need to understand the occlusal surface of this tooth very well . =)

Now ,, to understand the anatomy of this tooth let's discuss the occlusal surface of it

in detailz .

This tooth has 4 cusps ,, these cusps aren't in equal size .. thebiggest cusp is the ML

followed by the MB > DB > DL which z the smallest cusp .

^^ Remember that the DL cusp decrease in size as we go posteriorly so, the size of

the DL cusp is the maximum in the 1st

molar & the minimum in the 3rd

molar and

often this cusp is missing in the 3rd

molar ..

@@ blnesbell pix , refere to tha last page in the tfree'3 @@

Now ,, each cusp has 4 ridges .. let's take the MB cusp , this is cusp tip & we go

mesialy this z the mesial cusp ridge & this one the distal cusp ridge .. we have a same

B.cusp ridge not very prominent ..

We have also a triangular ridge .so, the MB as wee see (didn't hearwat the Dr said)

but instead the ML which z a huge cusp and we need to understand it careful , this is

the tip of the cusp, from the tip we goMesialy so it will be the MCR & here we don't

go distally for the DCR but we go OBLIQUELY ..

Y3ni this z the cusp tip, we don't have a CR going this way ,, y3ni this

Tooth doesn't have a distalcusp go distallyexactly .

The DCR of this tooth goes obliquely so, that's why the DCR is oneComponent or one mark of the oblique ridge .

This is the oblique ridge,, if u divide it into 2halfs :

*the first half of the OR is actually the DCR of the MLC.

Also the MLC has a triangular ridge, this ridge is continuous with the tip of the MBC

making continuous line . This is the transverse ridge ..

So :

Transverse ridge: is a ridge that goes from the tip of the MBC to the tip of the MLC

Oblique ridge: is the one that runs from the tip of the MLC to the tip of the DBC

* Between the TR & OR we have a fossa , this fossa called Central fossa ..

Now , let's take the DB cusp .. the DBC ,, it has a MR & DR.

The DR is continuous with the DMR & also it has a TR which is continuous with the

D.triangular cusp ridge of the MLC .now just D to the OR we have a depression , we

call it Distal fossa .

And also we have a distal triangular fossa : which is the fossa exactly near the DMR ..

So , we have D.fossa&D.triangular fossa .. andmesially we have M.triangular fossa .


3/10

Q: how many fassae I have in this tooth ?

A: 4 fossae ; 2 marginal fossae & 2 triangular fossae located just next to the marginal

ridges,, I have the central fossa & I have the distal fossa ..

Now, let's take the final cusp which is DL cusp. It has the DCR going to the DMR &

has a MCR & has a triangular ridge that ends in a groove .this ridge isn't continuous

with any ridges.

So, the 3 big cusps are called TRIGON ..and the Dl called TALON coz it is lonely ..

In addition , we have ( not heared) groove .. this is the cusp of CARABELLI

Now, we'll talk about the Max. permanent 2nd

molar ..

From the BUCCAL aspect : -

this tooth has the smaller crown size {the biggest crown is the crown of the Max. 1st

molar} ..

The DB cusp is less prominent & narrower MD than the DB cusp of the max. 1st

molar

** the roots are more distally inclined ,, as we go posteriorly the roots become more

distally inclined ..

From LINGUAL aspect :-

the DL cusp is smaller in width &hight

** the root is narrower MD & slightly distally inclined

- Low cusp of carabelli and I added a question mark here:

Last year we examined 3700 children in Jordan & we find the % of cusp of carabelli

of the 2ns molar is very low ..

From the MESIAL aspect :-

It has less numerous MRs (brdo mot heard)

We said last time the MR of the max. 1st

molar () BUT actually the MR of the 2nd

molar has less tubercles ; less # of tubercles ..

** MB & L roots are less divergent ; y3ni closer to each other ..

From the DISTAL aspect :-

The distal cusp is smaller than the distal cusp of the max. 1 st molar & a GREAT

portion of the occlusal aspect is visible ..

Q: if u look at the tooth from the distal aspect u can see part of the occlusalsurface

..why ??

A: bcoz we discuss the terms of the occlusion ; the MMR of this tooth is very HIGH

but the DMR is low ..

BUT the difference between the hight of the MR in the Max. 1st

molar is less ..of

course the the M is higher than the D but not too much , tha's why we don't see too


4/10

much of the occlusal surface of the max. 1st

molar when we look at it from the distal

aspect ..

From the OCCLUSAL aspect :-

MB & DL angles are more ACUTE so far we learnt that max. 1st

molar has 2 acute

angles & 2 obtuse angles ,, in acute angles tend to be more acute in max.2 nd molar &

the obtuse angles tend to be more obtuse {y3ni elzaweye el7adde btseer 7adde

aktrwlzaweyeelmonfrejebtseermonfrejeaktrlethalekeltoothbekoon t8reebn m3eeni

elshklelasquarishfl max. 1st molar } but tend to be very rhomboidal in the max.

2nd

molar ..

Talon: which is the area that called the DL cusp , is reduced in size,, more variable

pits & groove patterns .. the pit & groove pattern is very variable ; y3ni bshkl 3am as

we go posteriorly to the third molar the variable INCREASE ..

Lthalek mo3zm our teeth el 1st

molars byshbho b3d laken el 2nd

wl 3rd

molars bekoon

fi e5telaf kbeerbenhm ..

More supplementary grooves, crown is more constricted MD {y3ni el crown bkoon

dye2 MD} and the pulp is similar to that of the 1st

molar but if u want more details ,

actually it is there to find 2 canals in the MB root {in most of the cases the MB root

has 1 canal BUT as we said in the max. 1st molar there is a possibility that reaches up

to 60% to find 2 root canals in the MB root } ..

The max. 3rd

molar :

BUCCAL aspect :-

The crown is the smallest in all the dimensions , ,,, we said sth important which is : all

the mammals have the max. 1st

molar is the biggest in size but in

Champanzi&Gorellaz max. 3rd molar is the biggest .

** roots are much shorter & commonly fused and shows a pronounced distal

inclination ..

LINGUAL aspect : -

The DL cusp is usually missing so, DL we don't have a DL cusp ..

Let's see the this tooth , this is the max. 3rd

molar from an occlusalview ,, notice that

we have 2 buccal cusps ; MB & DB .. and only one cusp L ..

Q: where has the DL cusp gone ??

A: it is missing . (tb3nhyelmrra el 1000 ylli b3eda Dr. Ashraf =S)

MESIAL aspect :-

The crown profile is irregular & we see a fused root ..

DISTAL aspect :-

The DL aspect is absent & more of the occlusal surface is visible compared with the

1st

& 2nd

molars ..


5/10

In the 2nd

molar u see part of the occlusal surface when u look D but here in the 3rd

molar u see ALL the occlusal surface when u look D

This means that we have a big difference in the right of the MR ; the MMR is much

higher than the DMR

OCCLUSAL aspect :-

Actually it is a triangular or heart-shaped outline .. DB cusp is of minimal size became

the biggest cusp .

*Now , the ML followed by the MB > DB ..

NOTICE that bcoz the DL cusp is missing , the ML is huge ..

Q: how can I differentiate between the Right &Left ?

- Simply u have to identify that this is buccalbcoz we have 2 cusps ,, & this is the

lingual bcoz I have only 1 cusp ..

* the acute angle is the MB & the OBTUSE one is the DB ; that's why this is M & this I

D so that this is the max. Right 3rd

molar ..

* oblique ridge is barely visible bcoz one cusp is missing sometimes I can't see the

oblique ridge clearly but when the OR present it is connecting the L cusp with the DB

cusp ..

* pits & groove pattern is very variable & we hav e too many supplementary grooves

This is the pulp ^^^ I don't want u to remember the the pulp system of the 3rd

molar

bcoz normally we don't do canal treatment in the max. 3rd

molar bcoz this tooths'

position is very posterior in the mouth & normally it's buccaly inclined so, it is very

difficult to accept this tooth to doing canal treatment ^^^

So, at the caries the only treatment of this tooth end up with EXTRACTION ..( slide 26 for urself reading ;) )

Q: can we use OcclusalR to distinguish between the right from left ?

A: yea ,the OR go from the ML corner to the DB ..

Now , the 3rd

molar .. we said the most prominent pattern to have 3 cusps but

sometimes at least 20 ppl at this theater may have 4 cusps in the 3rdM , in this case

the DL cusp is not missing it is present but it is very small in size ,,, but this is actually

is not very common , the most common pattern is to find 3 cusps ,, in very very

small percentage of ppl we may findonly 2 cusps in the 3rd molar . and in some of us

3rd molars can be missing , not all of us have 3 rd molars ..(These are the type traits of the MAX. 3

rdmolars)

MANDIBULAR MOLARS

Regarding mandibular molars upper &lwer molars show progressive reduction

posteriorly ; this means as we go from the 1st

to the 3rd

molars the tooth decrease

in size "this is in humans" _ .


6/10

** the permanent 2nd

molars are the first teeth to appear in the permanent

dentition & they came up ( =() in the age of 6 yearsz ..

(ARCH TRAITS):

Q: If got a molar ,, how can u tell this is maxillary molar or mandibular molar in less

than 1 minute ??

1- Simply in the lower molars we have 2 roots ,,,,, in the max. we have 3 roots.^^ When we have 2 roots in the lower molars we have 1 mesial & 1 distal root .

2- Also, the 4 cusps are of EQUAL size , not like the Max. & sometimes we have afifth cusp like the Mand. 1 st molar but this actually in lesser size..

3- Crowns are broader MD the BL ..Look at this tooth here,, this is the max. molar BL wider than MD & the op posite is

true in MAND. MOLARS ..

*** the widest tooth MD is the mand. 1st

molar .

The 2 L cusps are of equal size but in the max. molar the 2 L cusps are not equal size

MB & DB cusps are of equal size and they are not of equal size in the max. molars ,

that's why it's very easy to tell upper from lower molars and also, I'll have sth that I

discovered about how to tell now , look at the molar if u see the root exactly

under the MR MAND. Molar

If u see the root exactly under the cusp MAX.molar

Hl2, max. molars have 3 roots ..

- the MB root is exactly under the MB cusp

- the DB root is exactly under the DB cusp

- the L root is exactly under the ML cusp

But in mand.Molar , w e have M & D root so, that's why the M root is exactly under

the MMR& the D root is exactly under the DMR ..

These are the (arch traits) that distinguish between the upper & lower molars

Let's begin now with the Mand. 1st

molar:

BUCCAL aspect:-

It is the widest tooth MD.. MB, DB, D cusps can be seen from the buccal view.

This tooth has 5 cusps; 3 B & 2 L so that's why we have MB,DB,D cusps B &

L we have ML &DL ..

** MB (the widest)> DB>D ..

MB & DB cusp are ofequal height, D cusp is very small CONICAL located in the DB

corner of the tooth bcoz we have 3 cusps ..we have 2 grooves:

* the first groove: is the groove the that separate the MB from the DBcusps & it is

called MB developmental groove

* the second groove: DB groove ..

So, we have MB & DB grooves .


7/10

So, if I give u in the exam the following question ..

Q: the following tooth is the tooth that has 2 grooves buccaly..wat z it ?

A: the only group of teeth where u see 2 grooves B are the Mand. Molars.

Now, from the BUCCAL aspect:-

The M profile in the cervical 1/3 is straight& sometimes concave BUT the occlusal

2/3 areconvex.

The D profile is entirely convex ..the M & D profiles are convergent cervically

The size of the tooth are not parallel that's why the tooth is narrower from the

cervical than the occlusal.

- The cervical line is similar to that of the upper 1st

molar nearly straight line.

The buccal surface: we see buccal prominent cervical ridge. This is similar to the

buccal ridge of the incisors & canine bcoz this presence the maximum height of

countourbuccaly at the junction between cervical 1/3 & the middle 1/3.

MB groove ends halfway, DB groove extends most of the B surface length.

** always MB groove is shorter than the DB groove.

** The roots:

We see 2 roots from the buccal view; the M & the D roots ..they are widely

separated (type trait) bcoz in the Mand. 2nd

the roots are closely to each other &

more D.inclined .

We have a common trunk & then after thiscommon trunk the root is divided. Notice

that the divide location happens at the junction between cervical 1/3 & middle 1/3.

The APICAl half of the M root is D.inclined ,, that's why we have in a curvature here

(& this is clinically important)

LINGUAL aspect:-

U see ML & DL cusps ..these are ofequal size ,, but notice that these are higher &

more conical than the B cusps ..

* So, the 2 L cusps are higher than the 2 B cusps .

L groove is between the 2 lingual cusps, notice that we have one groove L .. BUT we

have 2 grooves B..

Narrower MD than B profile the crown is narrower MD than when we look for the

crown from the B side..

M & D profile:Generally convex EXCEPT in the C1/3 btkoon straight or concave ,, but it tend to be

convergent cervically .. y3ni wide Occlusaly but narrow Cervically

The L surface is very convex both in horizontal & vertical plane.

(always L aspect bekoon w k2nno jzo2 mnkorah); entirely convex esp. at the Occlusal

1/3 ,, but the Cervical 1/3 is flat or concave .


8/10

** The roots seen from the L aspect we can see some vertical shallow depression on

the midline of the root trunk, proximal surface of roots are visible..

MESIAL aspect :-

The ML cusp is slightly higher than MB cusp ..always L cusp is higher than the B cusp

*B3ks eluppermolars*; in upper molars the opposite is true .. enno el B cusp is

higher than the L cusp.. (this point is very important w lazem t7fzooha mnee7 ;))

MMR is higher than the DMR & also has MMRgroove which similar to the Max.

1st

PREmolar but this groove is smaller

From the B cervical ridge , B outline curves sharply L (Arch trait)..

From the B cervical ridge we go too much L ,, but in the L inclination of the B profile

L profile is entirely convex, the L HOC is between the middle 1/3 &Occlusal 1/3

B HOC is very close to the Cervical line ..

M surface is flat or concave in the C 1/3 & convex in the Occlusal 2/3 ..

Here we see 1 root from the M view bcoz the M root is wider than the D one & that's

why we can't see the distal root M ..so, u can see the broad root which is the M root

that is very broad BL (and this is a Type trait) .

** This root is tend to be narrower in the 2nd& 3rd molars.

The apex is blunt & we can see proximal root concavity..

DISTAL aspect:-

U can see the 3 cusps ..notice that the DMR is lower than the mesial one & that's

why u can see part of the occlusal surface when u look from the D view & u can seeall the cusps .. u can see the DL , DB , & the D cusp ..

D cusp is L to the DB cusp (the DB cusp is more prominence from the D cusp)..

The DMR is shorter than the MMR & has a DMgroove ,, half of the B surface is visible

.. why ??

A: bcoz the line angle between the B & D surface is obtuse ..

* C line is straight & narrower BL than the M surface..

* always D surface is narrower BL than the M surface ..

** And finally the ROOTS:

Here we can see part of the M root ..why ???

A: bcoz the D is narrower from the M root ..

Also, we have a shallow groove ..


9/10

We will continue next time enshallah ..w hl2 el kl ytl3 wr8a w 8lam w yktebesmo

3leeha l7tta n3ml quiz =P

Obliqe Rtriangular R MR DR Cusp tiptransverseR

DR

MBcusp

carabelli

ML cusp R

DL cusp

THE END .

Forgive us if there is any mistake .. we did our best w sarlna 3 dayzmonaymeen w la 3m

n3ml shiella had el tfree'3 , so enshallahykoon mnee7 =)

Done by:

* Samar Al-Omari&

* Tuqa Al-Zoubi


10/10

dental anatomy lecture:4

Documents