Maxillary 2nd Premolar

8/2/2019 Maxillary 2nd Premolar

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Maxillary 2nd premolar

Buccal aspect:-

Here we have 2 illustration :1) tooth (14) : maxillary 1st premolar

2) tooth (15) : maxillary 2nd premolar.Because we have 1st , 2nd , 3rd , premolar so we have type trait to distinguish between them .

in breadth & height .smallerpremolarnd1) 2

premolar.stprominent than 1lessocclusal (DO) angle are-occlusal (MO) , disto-2)mesioWhich has prominent MO , DO angle and they are over hanging in the out line of the root .

.seldom seenrethe buccal ridge & depression a3)

Lingual aspect :-

buccalysame lengthBuccal profile is seldom ( not easy to seen ) because this tooth has the& lingual y .


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Mesial aspect :-

to the lingual cusp.equal in height1)you see the the buccal cusp2) you cant see the:

_ mesial marginal groove_ concavity in the crown proportion of the mesial surface3) maxillary 2nd premolar has asingle root (90%) , but maxillary 1st premolar has 2

root (90%)

ot (10%) , and maxillarypremolar may has 2 rond: remember that maxillary 2NOTE1st premolar may has one root (10%) SO the root is not important to distinguishbetween these 2 tooth BUT it can help you when you has 90% sure about the typeof root .

Occlusal aspect :1)ovoid rather than hexagonal because the mesial & distal outline are parallelbecause thistooth is widebuccaly as lingual

2) lessconvergence of mesialy & distaly outline

3) we see the mesial & distal profile parallelbecause buccal cusp very nearly equal lingual inmesio-dista


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4) More rounded angles in the maxillary second premolar are rounded more than the maxillary

first one so the angles tend to be prominent in the maxillary first, and this is similar to the case

of maxillary incisors we said that the lateral incisor tends to have more rounded angles also

maxillary second premolar tends to have more rounded angles.

5) the apex of Lingual cusp is in the midline, but the tip of the lingual cusp in the maxillary first

premolar was slightly to the mesial.

6) it has a shorter occlusal groove, but in the maxillary first premolar this groove is longer that's

why the surface area of the occlusal surface in the maxillary second is less compared to thesurface area of the maxillary first premolar.

7) it has more numerous supplemental groove but we don't see these too many supplemental

grooves in the maxillary first, and finally no mesial marginal grooves crossing the mesial

marginal ridge.

-THE Pulp1) it is cigar shaped in a cross section at cervix "drawing B in the silde" and the pulp horns

are almost equal height, so the drawing "C" in the side below is wrong it should be like

the pic here -->

*Usually a single pulp canal , put a line under usually because sometimes we can see two

canals and sometimes we can see three canals but this is very rare, depending on the Dr's experience in his

fifth year in the dental school, this is a type trait.


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Mandibular 1st

premolar

-Buccal aspect

Long pointed buccal cusp in the buccal profile.

Mesial cusp ridge is shorter than distal one , so this is similar to the canines but not similar to themaxillary first premolar where the mesial cup ridge is longer than the distal cusp ridge, the Cusp tip

is a little mesial to the tooth midline.

HOCs are at the same level and located just occlusal to the halfway of the crown

Mesial & Distal outlines are markedly converging, as you see below the mesial and distal profiles

are sharply converging toward the cervix of the tooth, the Cervical Line is flat MesioDistally

compared to that of canine.

-Lingual aspect

notice how small the tooth is, buccally it was wide but lingualy its very very narrow, so this is the

premolar where the difference between the two cusps is very huge.

if this is an exam question : the discrepancy or difference in size between the two cusps of a premolartends to be greatest in.. ?? the answer is the mandibular first premolar where the difference in size betweenthe buccal and lingual cusp is the greatest; that's why the entire buccal profile and also the occlosal surface

can be seen from the lingual aspect, this is a type trait. the occlusal surface, buccal triangular ridge and marginal ridges all of them can be seen fromthe

lingual aspect because the crown is tilt lingually and cervically in relation to the long axis of the

tooth as we discussed in the premolar the crown is tend to be tilted lingualy so that's why the

occlosal surface is not exactly horizontal it is slightly inclined.

Buccal triangular ridge crosses midportion of the occlusal surface,see because the crown is tilted

lingually this makes the buccal cusp occupied more than 80% of the crown and less than 20% for

the lingual cusp." the Lingual cusp is a minor elevation in height & pointed cone in shape, It may be

centric in the center or eccentric in relation with buccal cusp there is no a rule for this"


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the mesial aspect:1) the occlusal plane still lingually and cervicaly .2) the transverse ridge can be seen which is composed of the triangular ridge of the buccal cusp

and the triangular ridge of the lingual cusp .*Notice that: if you make the long axis of the root it tend to pass not in the middle of the occlusalsurface , it tend to pass at the tip of the buccal cusp. Thats why when you do a filling on this tooth ,

you need to remember this feature because we cant start dri lling the tooth vertically.what happen ifwe continue drilling ?you will make a tooth fracture to the lingual cusp.So, because of that when you drill this tooth you have to drill along the axis of the crown, not alongthe axis of the root . this is very important.We can see a groove at the end of the mesial marginal ridge , and also at the end of the mesial ridgeof the lingual cusp we have a groove called the mesiolingual groove .So the mesial marginal ridge with the mesiolingual groove of the lingual cusp, they meet in a groove

.this is a type trait ,because this feature is not found in the mandibular second premolar.3) The buccal profile shows highly lingual inclination .

Lingual profile is straight ,then it is convex up to the cusp of the tooth .(4

5) The tip of the lingual cusp is inclined with the long axis of the root .so this is the only tooth that theextension of the long axis of the root passes with the tip of the buccal cusp.In pre molar if you remember : take the long axis of the root , it passes between the two cusps .

The root(6The root is broad buccolingually and narrow mesiodistaly .The mesial contact area is inclined with the apex of the buccal cusp . so this is the contact area

which is located just below the tip of the buccal cusp.From the distal aspect : the distal marginal ridge is more prominent ( tends to be more horizontal andhigher that the mesial marginal ridge).

This is the only tooth among all teeth where the distal marginal ridge is higher than the

mesial marginal ridge . in all other teeth the mesial marginal ridge is higher than the distal

marginal ridge .

This is a good question .


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Exam Question!Which tooth has it's Mesialmarginal ridge tends to belower than the Distal marginalridge?

-Its the Mandibular 1stpremolar.

Distal marginal ridgetends to be morehorizontal than theMesial marginalridge and also it'shigher!( it's the only toothwith this Property )

In premolar -if you remember- , the long axis of the root passes between the two cusps. In fact theroot is broad bucco-lingually and tends to be slightly narrower mesio-distally, while the mesial contactarea is in-lined with the apex of buccal cusps, so again the contact area is located just below thebuccal cusps.

P.S

The Mesial contact area is located just below the buccal cusps!

- Distal Aspect- In Distal Aspect, the distal marginal ridge is more prominent, which means the Distal marginal ridge

tends to be more horizontal than the Mesial marginal ridge and also it's higher. The premolar is theonly tooth where we can find that the Distal marginal ridge tends to be" Higher" than the Mesialmarginal ridge . In distal aspect we dont see any disto-lingual groove but we can clearly see mesio-lingual groove. For Contact area it's more extensive distally than mesialy.


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-Occlusal aspect

Talking about Occlusal aspect whichis Diamond in shape, also it'sInverted V shaped Buccal profile,furthermore Mesial & Distal profilesconverge lingually and the Distal

profile is more convex than theMesial profile. We also notice thatLingual profile is (half) Mesio-distallength of Buccal profile, and thatsbecause the Buccal cusp is muchbigger than the lingual cusp. One moreproperty is that 2/3 of buccal surfacewith ridge & depressions are visiblebecause the crown is toward lingually when we look at the tooth from above we cansee part of the Occlusal surface about the

occlusal table it's triangular in shape. While it was not triangular in theMaxillary 1st and 2nd premolar .Some information about Mesial & Distal fossa, each contains1- A pit2-A groove extending Bucco-Lingually parallel to MR3-Mesial contains Mesio-Lingual groove running in aMesio-Lingual direction from Mesial pit.Mesio-Lingual section of Mandibular Premolar is similar to that of the Canine, and for the Bucco-lingual section we can see two horns but the the Buccal horn is much higher than lingual horn. Sodoing a "Root Canal Treatment" for that tooth then you have to make access to the root canal then

you have to drill obliquely because when you go vertically then you will not be able to reach thepulp and you will fracture off the lingual part. So remember to go oblique with the long axis of thecrown.

P.SMesio-Lingual section of Mandibular Premolar is similar to that of the Canine !

Occlusal table: is the Areabetween the ridges of thecusps and the marginalridges. Its marks theocclusal surface of the

tooth.

Ex ( Mesial and Distalridges and also Distal andMesial marginal ridges andcontinue that with lingualcusp ,all together , is theocclusal table )


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The pulp:

The mesiolingual section is similar to that of canine, in the buccolingual section we see two horns ,

but notice that the buccal horn is much bigger than the lingual horn.

CONCENTRATE HERE:

The buccal horn is bigger than the lingual horn.

PLEASE REMEMBER:

When we want to do root canal treatment for that tooth you have to make axis to the root you have to

drill OBLIQUELY.

Many students in the fifth year when they do root canal treatment they go vertically, and if you go

vertically you will not reach the pulp and you will fracture of the lingual cusp.

REMEMBER:

You have to go with the long axis of the crown (obliquely) , not with the long axis of the root.

-in cross section:the root is OVOID.

Pulp

ML section Similar to that of canine

BL section

A large B horn &

a small L horn

X section

Ovoid

Mandibular 1st premolar

-Buccal aspect:

From the buccal aspect it is very similar to the mandibular first premolar ,from the lingual aspect it is

different , why ?

Because the mesiodistal diameter of that tooth is equal the mesiodistal diameter buccaly ,so this

tooth the buccal diameter equal the lingual diameter , but the mandibular first premolar have ahuge

buccaly diameter and very small lingual diameter.

Also the occlusal surface cant be seen, why?

Because the lingual cusp are high.


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Here the lingual cusp is very low occlusal plane is perpendicular to long axis.

See here the occlusal plane is not perpendicular to the long axis of the root.

But here the occlusal is perpendicular o the long axis.

Thats why if you want to do root canal treatment to the mandibualr second premolar you can go

vertical you will reach the pulp.

CONCENTRATE HERE

You cant go vertically in the first mandibualr premolar.

We see commonly cusps on that tooth but this is in 60% of the cases .when you go home look in the

mirror , if you find two cusps lingual on the mandibualr second premolar this means you are among

the 60-70% pof people ,but if you find one cusp you are among 30-40% of people. And as aresult we

cant call it bicuspid we call it premolar ,because bicuspes means two cusps and this tooth has three

cusps.

One student may rise his hand and ask :some molars have three cusps ,how can I distinguish

between them?

Answer: you must count the number of cusps buccaly ,if there is one buccal cusp Then it is a

premolar , if there is two cusps there is a molar.

So this the way to distinguish between three cusped molar and premolar.

The two lingual cusps they are not for equal size ,the mesial tends to be bigger than the distal

CONCENTRATE HERE:

The two lingual cusps they are not for equal size ,the mesial tends to be bigger than the distal.

Which means mesiolingual cusp bigger than distolingual cusp.

So two third of the mesiodistal distance is given for the lingual cusp and one third for the lingual cusp.

We see a lingual groove between these two cusps.


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.

Buccal aspect Similar to Mandibular 1stpremolar

Lingual aspect MD diameter = that from B aspect (type

trait)

Occlusal surface cannot be seen (type

trait) Occlusal plane is perpendicular to tooth

axis

2 lingual cusps (most commonly) ML major, 2/3 MD diameter, same height

as B

DL minor

Lingual groove

Mandibular 2nd premolar 45

44

44

45

Mesial aspect--The triangular ridges of the buccal and mesio-lingual cusp are visible as you see here in themandibular right second premolar.

-Cusps do not form a continuous crest.

* if you remember when we discussed all the three premolars we said we have a continuous

transverse ridge between the tip of the buccal cusp until the tip of the lingual cusp but here

because we have two cusps lingually we do not see a continuous crest (transverse ridge).

**The posterior tooth that does not have transverse ridge is?

Mandibular second premolar.

Distal aspect:-lingual cusps are seen.

Mesial aspect

Triangular ridges of B & ML

cusps dont form a

continuous crest

Distal aspect

Both lingual cusps are seen

Mandibular 2nd premolar 45

44

44

45


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Occlusal aspect

This is the tooth from the occlusal surface , notice that the mesial and distal

profiles are parallel and the looks like square in shape ,so this is the only premolar

which is square in shape.

-more than half of the buccal surface can be seen

because the crown is slightly inclined lingually.

-the buccal ridge is less prominent than the mandibular

.a type traitfirst premolar and this is

-mesial and distal marginal ridges are equal in length.

-the groove looks like the letter "Y" in shapemeet at the central pit.1-M separates B & ML triangular ridges runs obliquely.2-L separates lingual cusps.3-D separates B & DL triangular ridges.

-M & D triangular fossae. each contains:

1- A pit

2- MB & DB grooves

-mesio-lingual cusp is bigger than the disto-lingual cusp.

.

Occlusal view

Grooves (Y-shape meet at thecentral pit)

M separates B & ML triangular ridges

runs obliquely

L separates lingual cusps

D separates B & DL triangular ridges

M & D triangular fossae

each contains

A pit

MB & DB grooves

Mandibular 2nd premolar

Occlusal aspect

Square profile (type trait)

M & L profiles are parallel

> B surface is visible

B ridge is less prominent than

that of mandibular 1stpremolar

(type trait)

M & D MRs are equal in length


disto-

lingual

cusp

mesio-

lingual

cusp

Central

pit

ML

D


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Pulp :-

-the pulp is not similar to that in mandibular first premolar .

-we have three horns for each cusp but the highest horn is the horn for the buccal cusp followed by themesio-lingual horn followed by the disto-lingual horn

Root :-

The root of this tooth is exactly conical which is similar to the root of the maxillary central incisor and because

of that sometimes we can do trans- implantation.

*What does trans- implantation mean ?

We can take this tooth out without it's socket and put it in the maxillary central incisor' socket ,the two roots

will be identical.

*What is the percentage of having two root canals in mandibular premolars ?

30%

*What is the percentage of having one root canal in mandibular premolars ?

70%

*What is the percentage of having two root canals in maxillary first premolars ?

90%

*What is the percentage of having two root canals in maxillary second premolars ?

Nearly 10%

Pulp BL section

Pulp chamber is

wider

Pulp horns are of

equal height

Xsection



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TOP POINTS:-1-chartaristics of mandibular second premolar:

Occlusal

aspect

Distal

aspect

Mesial

aspect

Lingual

aspect

Buccal

aspect

-Grooves (Y-shape meet at thecentral pit.

-M & D triangularfossae

-each contains:

*pit.

*MB & DB grooves.

-Both lingualcusps are seen.

-Triangularridges of B &ML.

-cusps dontform a

continuous

crest.

-MDdiameter =

that from B

aspect.

-Occlusalsurface

cannot be

seen.

-2 lingualcusps

-lingualgroove.

-buccal pro-file+occlusal

Surface-visible.

-Buccaltriangular ridge

crosses

midportion of

the occlusal

surface.

-Lingual cusp is a

minor elevation

in height+pointed cone.

-Root isnarrower from

lingual aspect

2-buccal aspect

*crown bilaterally symmetrical.

3-lingual aspect

*none of buccal profile visible.

*buccal and lingual cusps are almost equal in height.

4-mesial aspect

*no transverse ridge.

*Mesial marginal ridge is horizontal .

5-occlusal aspect

*squre*buccal and lingual cusps are nearly equal in size.

*main grooves from "Y".

*central pit.


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Questions :-

1- The posterior tooth that does not have transverse ridge is?

A)mandibular first premolar.

B)maxillary second premolar.

C)mandibular second premolar.

D)mandibular second molar.

2-the difference between the two cusps tends to be greatest in mandibular first premolar:

A)true

B)false

3-the grooves in the picture is for :

A)mandibular second molar

B)maxillary second premolar

C)maxillary second molar

D)mandibular second premolar

4) All of the following sentences are correct about mandibular second premolar EXCEPT:A)main grooves shape "Y" pattern with central pit

B)cusps form a continuous crest .

C)both lingual cusps are seen from the distal aspect.

D)M&D marginal ridges are equal in length.

5)All of the following sentences are false about mandibular premolars EXCEPT:

A)mandibular second premolar has no central pit while the first one has.

B)in first premolar,the lingual cusp much higher then buccal.

C)the occlusal table is triangular in outline in second premolar.

D) M&D marginal ridges are equal in length in second premolar.

6)The occlusal surface in the picture is for:

A)mandibular first molar

B)maxillary second premolar

C)mandibular first premolar

D)mandibular second premolar

7- the percentage of having two root canals in mandibular premolars is 10%:

A)true

B)false


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Answers-

DONE BYDental anatomy Group

Ahmed AL-Shammary

Heba Ramadneh Hadeel sumrien

Asma Almawas Hiba Jarah

A9eel Gwanmeh Rawda NajarRussia Elshboul Eman Idkaidek

Eman Nazzal Abeer Dirawi

Noha Mohamad Sundous Abuzaid

Gaydaa Kanan Baarah SalamatSalam Bataenih

" "

"

"

C1

A2

D3

B4

D5

C6

B7

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Maxillary 2nd Premolar