The document discusses the morphological characteristics and chronology of the permanent mandibular second and third molars. It provides detailed descriptions and diagrams comparing the anatomical features of the first, second, and third molars, including their crowns, roots, and occlusal surfaces from the buccal, lingual, mesial, and distal aspects. The second molar is generally smaller and more symmetrical than the first molar. It has only four cusps compared to the first molar's five cusps. The third molar is the most variable and complex molar in terms of morphology. Diagrams illustrate and compare the key differences between each molar from different angles.

2. ‫ت‬َ ‫أتن‬َ ‫كأ‬َ ‫تن‬َّ‫إك‬ِ‫ن‬ ‫ن اأ‬َ ‫ت‬َ ‫م‬ْ‫نَت‬ ‫ل‬َّ‫ك‬‫ع‬َ ‫م اأ‬َ ‫الأ‬َّ‫ك‬ ‫إ‬ِ‫ن‬ ‫ن اأ‬َ ‫ل‬َ ‫مأ‬َ ‫ل‬ْ‫نَت‬‫ع‬ِ‫ن‬ ‫الأ‬َ ‫كأ‬َ ‫تن‬َ ‫ح ا‬َ ‫ب‬ْ‫نَت‬‫س‬ُ‫ب‬ ‫اأ‬ْ‫نَت‬‫او‬‫ل‬ُ‫ب‬‫ق ا‬َ ‫أ‬
‫م‬ُ‫ب‬‫كمي‬ِ‫ن‬ ‫ح‬َ ‫ل‬ْ‫نَت‬‫مأ ا‬ُ‫ب‬‫لمي‬ِ‫ن‬‫ع‬َ ‫ل‬ْ‫نَت‬‫ا‬
‫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
) ‫ساورةأ البقرةأ آيةأ‬32(
‫الرحمن‬ ‫ا‬ ‫بسم‬
‫الرحيم‬
‫صدق‬‫ا‬
‫العظيم‬

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
1st
. Molar 2nd
. Molar 3rd
. molar
Enamel
organ
appearance
1st
. Evidence
of
calcification
4 m.i.u
At birth
1 ‫أ‬year
2 ‫أ -أ ½أ‬3 ‫أ‬years
4 ‫أ‬year
8 ‫أ –أ‬10 ‫أ‬years
Enamel
completed
2 ‫أ -أ ½أ‬3 ‫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
1st
. Molar 2nd
. 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
1st
. Molar 2nd
. 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
1st
. Molar 2nd
. 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
1st
. Molar 2nd
. 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
1st
. Molar 2nd
. MolarThis 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
1st
. Molar 2nd
. 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
1st
. Molar 2nd
. 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
1st
. Molar 2nd
. Molar1. 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
1st
. Molar 2nd
. 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
1st
. Molar 2nd
. 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
1st
. Molar 2nd
. 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
1st
. Molar 2nd
. 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
1st
. Molar 2nd
. Molar 3rd
. Molar

22. Lingual aspect
1st
. Molar 2nd
. Molar 3rd
. Molar

23. Mesial aspect
1st
. Molar 2nd
. Molar 3rd
. Molar

24. Distal aspect
1st
. Molar 2nd
. Molar 3rd
. Molar

25. Occlusal aspect
1st
. Molar 2nd
. Molar 3rd
. Molar

27. Buccal aspect
1st
. Molar 2nd
. Molar 3rd
. Molar

28. Lingual aspect
1st
. Molar 2nd
. Molar 3rd
. Molar

29. 1st
. Molar 2nd
. Molar 3rd
. Molar
Mesial aspect

30. 1st
. Molar 2nd
. Molar 3rd
. Molar
Distal aspect

31. 1st
. Molar 2nd
. Molar 3rd
. Molar
Occlusal aspect

33. 1st
. Molar 2nd
. Molar 3rd
. 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?