Lower Second & Third Molar

Ist Dental Students - Morphology

2. تَ نتأَ أكَ نتَّكإِن أا نَ تَ مْتَنلَّكعَ أا مَ ألاَّكإِن أا نَ لَ أمَ لْتَنعِن ألاَ أكَ نتَ ا حَ بْتَنسُب أاْتَنوالُبا قَ أ
مُبيمكِنحَ لْتَنا أمُبيملِنعَ لْتَنا 
أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ أ
) أةيآ أةرقبلا أةرواس32(

نمحرلاامسب
ميحرلا
قدص ا
ميظعلا

3. Permanent Mandibular
Second & Third Molars
By:
Assistant professor of Oral Biology
Faculty of Dentistry
Mansoura University

4. General characters of the Permanent
Mandibular second Molar:
1.Arch position:

5. General characters of the Permanent
Mandibular second Molar:
2. General form and function:
The second molar resembles the first
molar in many respects, although it is more
symmetrical, and smaller in all dimensions.
It has the least complicated occlusal design
of any molar. Normally only four cusps are
present, and thus there is no distobuccal
groove, and no distal cusp. In mastication, it
functions with the other molars in grinding.

6. Chronology
1
st
. Molar2
nd
. Molar3
rd
. molar
Enamel
organ
appearance
1
st
. Evidence
of
calcification
4 m.i.u
At birth
1 أyear
2 أ½ أ- أ3 أyears
4 أyear
8 أ– أ10 أyears
Enamel
completed
2 أ½ أ- أ3 أyears أ 7 أ– أ8 أyears 12 أ– أ16 أyears
Eruption 6 أ– أ7 أyears 11 أ– أ13 أyears 17 أ- أ21 أyears
Root
completed
9 أ– أ10 أyears 14 أ– أ15 أyears 18 أ– أ25 أyears

7. Describe in details the
morphological differences between
mandibular permanent first and
second molars, mentioning their
chronology and illustrating your
answers with diagrams

8. Buccal aspect
1
st
. Molar 2
nd
. MolarCrown:
1.The crown is somewhat
shorter cervico-occlusally.
2.The crown is narrower
mesiodistally.
3.There are only two buccal
cusps, which are about equal
in their mesiodistal
measurements but
mesiobuccal cusp is wider.
4.There is only one buccal
developmental groove act as a
line of demarcation between
the mesiobuccal and
distobuccal cusps and it may
end in a pit on the middle of
the buccal surface.
½
½
⅓
⅓
⅓

9. Buccal aspect
1
st
. Molar 2
nd
. Molar
Crown:
5- More cervically lacated
contact areas..
6- Cervical line is nearly
straight. It may point
sharply toward the root
bifurcation
7- crown more symmetrical
from all aspects.

10. Buccal aspect
1
st
. Molar 2
nd
. MolarRoot
1.The root is shorter than those
of the first molar.
2.The roots are usually straighter
and closer together and their axes
are nearly parallel.
3.The roots are inclined distally
in relation to the occlusal plane
than is found on the first molar.
4.The roots taper apically and
more pointed than of the first
molar.
5.Both roots are flattened MD
and M root is slightly longer than
D root.
6.Longer root trunk.

11. Lingual aspect
1
st
. Molar 2
nd
. Molar
1- Only lingual cusps
are visible and more
pointed than buccal
cusps.
2- The main difference
is that the lingual
convergence of the
tooth as a whole, crown
& root, is less than
what could be found in
the first molar.

12. Lingual aspect
1
st
. Molar 2
nd
. Molar
This relation resulted in:
1. Mesiodistal calibration at the
cervix lingually is always
greater than that of the
mandibular permanent first
molar.
2.Little of the mesial and distal
surfaces may therefore be seen
from this aspect.
3.The curvature mesially and
distally on the crown that
representing the contact areas
are more noticeable from the
lingual aspect.
4.The contact areas are found to
be at slightly lower level,
especially in the distal contact
area, than those of 1st. molar

13. Mesial aspect
1
st
. Molar 2
nd
. MolarCrown
1. The cervical ridge buccally
is in most cases less
pronounced.
2. The mesial contact area is
larger in size.
3. The occlusal surface may
be more constricted
buccolingually.
4. Cervical line shows less
curvature, being straight and
regular in outline
buccolingually.
BB
L

14. Mesial aspect
1
st
. Molar 2
nd
. Molar
Root
1-The M root is less broad
and is somewhat pointed
apically, permitting part of
the distal root to be in sight
buccally, while in first
molar it appeared lingually.
2- The M root has
longitudinal depression on
its M surface as 1st. molar
B
L

15. Distal aspect
1
st
. Molar 2
nd
. Molar
1.Absence of distal cusp.
2.DB cusp is the shortest of the
four cusps.
3.Absence of distobuccal groove.
4.Contact area is larger and is
centered on the distal surface
buccolingually and is placed
equidistant from cervical line
and marginal ridge.
5.The D marginal ridge is
concave but less angular than
M one and less frequently
crossed by a marginal groove
B
L

16. Occlusal Aspect of
Mandibular first Molar :
1. Geometric outline:
2. Dimensions.
3. Surface outlines:
- Buccal outline.
- Lingual outline.
- Mesial outline.
- Distal outline
4. Surface describtion:
- Cusps.
- Ridges.
- Grooves.
- Fossae.
- Pits.
1
2 2
3
4

17. Occlusal aspect
1
st
. Molar 2
nd
. Molar
•Geometric outline:

The occlusal aspect geometric
outline found to be
rectangular in shape.
•Dimensions.
1.The crown is larger MD
than BL.
2.The D side is narrower
than the M side and the L
side is narrower than B
side.
•Surface outlines:
1.Prominent cervical bulge
can be seen.
2.The D shorter side is more
convex (semicircular )than
M side which is nearly
straight.

18. Occlusal aspect
1
st
. Molar 2
nd
. Molar
• Surface describtion:
- Cusps.
1. Absence of the distal cusp.
2.The four cusps are nearly
equal. The two M cusps are
larger than D cusps (MD and
BL).
- Ridges.
1.Four Δ ridges of four cusps
making transverse ridge
between MB and ML cusps
and DB and DL cusps.
2.2 marginal ridges M and D.
- Fossae.
1.Large central fossa.
2.Small M Δ fossa.
3.Minute D Δ fossa.
- Pits.
1.May be present in any of the
fossae.

19. Occlusal aspect
1
st
. Molar 2
nd
. Molar
-Grooves.
Developmental grooves.
1- Cross – shaped groove
(cruciform fissure), dividing
the occlusal portion of the
crown into four parts that are
nearly equal.
2- Absence of the distobuccal
developmental groove.
3- The central groove extends from
the central fossa to both M
and D Δ fossae. Its course is
straighter than lower 6.
4- B groove separates the two B
cusps. L groove separates the
two L cusps.
5- The buccal and lingual
developmental groove meet
the central developmental
groove at right angles at the
central pit on the occlusal
surface.

20. Occlusal aspect
1
st
. Molar 2
nd
. Molar
- Supplemental grooves.
1.Many supplemental
grooves found to be radiating
from the developmental
grooves.
2. The cusp slopes on occlusal
surface are roughened by
these grooves.
3. The marginal ridge grooves
may be seen and are more
in M than D.

21. Buccal aspect
1
st
. Molar2
nd
. Molar3
rd
. Molar

22. Lingual aspect
1
st
. Molar2
nd
. Molar3
rd
. Molar

23. Mesial aspect
1
st
. Molar2
nd
. Molar3
rd
. Molar

24. Distal aspect
1
st
. Molar2
nd
. Molar3
rd
. Molar

25. Occlusal aspect
1
st
. Molar2
nd
. Molar3
rd
. Molar

27. Buccal aspect
1
st
. Molar2
nd
. Molar3
rd
. Molar

28. Lingual aspect
1
st
. Molar2
nd
. Molar3
rd
. Molar

29. 1
st
. Molar2
nd
. Molar3
rd
. Molar
Mesial aspect

30. 1
st
. Molar2
nd
. Molar3
rd
. Molar
Distal aspect

31. 1
st
. Molar2
nd
. Molar3
rd
. Molar
Occlusal aspect

33. 1
st
. Molar2
nd
. Molar3
rd
. Molar

34. Lower 6 &7
Buccal
aspect
Occlusal aspect
34

35. Lower 6&7
Buccal
aspect
Occlusal aspect
35

36. Lower 8
Buccal
aspect
Lingual aspect
36

37. Lower 8
Occlusal
aspect
37

39. A QESTION?