1. Cairo University
Faculty of Oral and Dental Medicine
Prof. Dr. Nahed A. Khalil
Head of Oral Biology Department
& Contributing Staff Members
Human Dentition

3. PREMOLARS
There are four maxillary and
four mandibular premolars:
Upper 1st premolar: upper 4
Lower 1stpremolar: Lower 4
Upper 2nd premolar: upper 5
Lower 2nd premolar: Lower 5

4. Maxillary first premolar
It has 5 surfaces:
Buccal
Lingual
Mesial
occlusal
Distal

5. Geometric outline of the crown
Buccal and lingual surfaces have trapezoid
outline .The smallest uneven side cervically.

6. Buccal Outlines
Mesial outline is nearly concave.
Distal outline is nearly straight.
Mesial cusp slope is nearly straight while the
distal cusp slope is slightly convex.
D
Contact areas:
Mesially is at the middle third while Distally it
is occlusally positioned which is an exception
from other permanent posterior teeth.
Cervical line: is convex root wise.
B cusp
pointed
and long
M

7. Outline and surface anatomy of the root
The M and D outline of the root tapers
to a pointed apex that is slightly curved
distally.
.
If it has two roots, the lingual root is
hidden behind the buccal root as it’s
shorter and narrower than the buccal
root.
The surface of the root is convex and
smooth

8. Surface anatomy of the crown
Elevations:
•The buccal surface is convex with the
maximum convexity at the cervical 1/3 .
•The middle lobe is prominent buccally
forming the BUCCAL ridge.
Depressions:
Shallow depressions are present
mesial and distal to the B ridge
(M&D developmental grooves)

9. Lingual outline and surface anatomy of the crown
M and D outlines are convex.
•The lingual cusp is shorter by 1 mm
but sharper than the buccal cusp
•The D slope of the lingual cusp is
longer than the M slope
Cervical line: is convex root wise.
The lingual surface is convex with the
maximum convexity at the middle 1/3
M
D

10. Outline and surface anatomy of the root
The M and D outlines of the root taper
to a pointed apex that is curved distally.
If two roots, the lingual root appears
shorter and narrower than the buccal
root.
The surface of the root is convex and
smooth

11. Geometric outline of the proximal aspect
Distal surface
Mesial surface
Trapezoid in
shape
Smallest of the uneven sides
is occlusaly

12. Outlines of proximal aspect
Distal surface
Mesial surface
Buccal outline is convex with the maximum convexity at the
cervical 1/3.
Lingual outline is convex with maximum convexity at
middle1/3.
Cervical line curves occlusally and decreased distally.

13. Distal aspect
Mesial aspect
Occlusal outline:
B cusp is longer than L cusp by 1mm.
Wide occlusal table.
B cusp tip is below the center of B root.
L cusp tip is in one line with the lingual outline of the L
root
MMRis present at the junction of O 1/3 and M 1/3, while

14. Proximal surface anatomy
Distal aspect
Mesial aspect
Contact area:
At the middle third (OC dimension) and
slightly buccal to the midline (BL
dimension)
Mesial developmental groove is
crossing MMR and located lingual to
the contact area.
Mesial Developmental depression in
the crown and continues with that
between the roots (canine fossa).
Occlusally positioned
and more buccally.
Smooth and convex
surface except for a
small flat area cervical
to contact area .

15. Mesial aspect
Distal aspect
In case of two roots (80%).
Root trunk is about half the
root length.
Surface is smooth and convex
except deep developmental
depression below bifurcation.
Root trunk is longer as the
bifurcation is near the
apical 1/3
Surface is smooth and
convex except shallow DD
on the root trunk

16. In case of one root.
The B and L outlines tapers to a blunt
apex on the center of the crown.
The surface is smooth and convex except
for a shallow depression in the center that
is deeper mesially than distally.

17. GEOMETRIC OUTLINE OF THE OCCLUSAL
ASPECT
It is hexagonal in shape
•2 equal buccal sides (MB, DB)
D
•M side shorter than D side.
•ML side shorter than DL side.
Thickness is greater than width
The crown is wider buccally than
lingually.
M

18. Surface anatomy of occlusal aspect:
Elevations:
B triangular ridge.
L triangular ridge.
M & D marginal ridges
Depressions:
Central developmental groove
M and D triangular fossae.
M marginal developmental
groove.

19. Pulp cavity.
MD section
BL section
Root canals:
2 root canals (B&L)
L canal is larger &more
accessible
Narrow
Pulp chamber:
Wider

20. Maxillary second premolar
It has 5 surfaces:
Buccal
Lingual
Mesial
occlusal
Distal

21. Geometric outline of the crown
• Buccal and lingual surfaces have
trapezoid outline.
The smallest of the
uneven sides is cervically.

22. Facial Outlines and surface anatomy of the crown
4
D
M
B cusp is long and pointed
5
D
M
B cusp is short and less pointed
M slope is longer than D
Mesial contact A is in the M1/3
while distally more occlusal.
M slope is shorter than D
Mesial contact A is in O1/3 while
distally more cervically.
Cervical line curved root wise.
Cervical line less curved.

23. 4
D
M
Prominent B ridge
Narrow cervical portion.
Short root.
5
D
M
Less prominent B ridge
Wider cervical portion.
Longer root.

24. Lingual outline and surface anatomy of the crown
4
The L cusp is shorter by
1 mm than the B cusp.
80% has 2 roots with L
root is shorter than B
root and its apex is
pointed.
5
The L and B cusps are
nearly of same height.
Rare to has 2 roots
In case of two roots the L root
is shorter and its apex is
more blunt.

25. Mesial aspect
4
5
B cusp is longer than L
cusp by 1mm
The cusps are nearly at the
same level.
The occlusal table is
wide.
The occlusal table is narrow.
The crown surface is smooth
Mesial DG and canine
and convex while the root has
fossa.
shallow developmental
depression.

26. 4
5
MMR at the junction of M1/3
&O1/3
MMR positioned more
occlusal.
Contact area:
At the middle third (OC
dimension) and slightly
buccal to the midline (BL
dimension)
At the occlusal third (OC
dimension) and slightly
buccal to the midline (BL
dimension)

27. Distal aspect
4
5
DMR more occlusal than MMR
DMR more cervical than MMR
CA occlusally positioned and
more buccally than MCA.
CA cervically positioned and
more buccally than MCA.
Smooth and convex surface
except for a small flat area
cervical to contact area.
Smooth and convex
surface.

28. 4
Root trunk is long as
the bifurcation is near
apical 1/3
Surface is smooth and
convex except shallower
DD on the root trunk than
mesially.
5
One root and if 2 the
bifurcation will be
more apically.
Surface is smooth and
convex except deeper
DD in the middle of the
root than mesially.

29. Occlusal aspect
5
D
M
D
M
It’s oval
It’s
hexagonal
B & L triangular ridges.
B & L triangular ridges.
M & D marginal ridges
Thicker M & D MRs

30. 4
5
Long Central DG
M developmental groove
Shorter Central DG.
Not present.
M and D triangular fossae. M and D triangular fossae.

32. Mandibular first premolar
It has 5 surfaces:
Buccal
Lingual
Mesial
occlusal
Distal

33. Geometric outline of the crown
• Buccal and lingual surfaces have
trapezoid outline.
The smallest uneven side is
cervically.

34. Buccal Outlines
Mesial and distal outlines are nearly concave
Mesial and distal cusp slopes are also
slightly concave
D
Contact areas:
Mesially at the junction of O and M
thirds while Distally it’s cervically
positioned.
Cervical line: is convex root wise.
B cusp
pointed
and long
M

35. Outline and surface anatomy of the root
The M and D outline of the root tapers to a
pointed apex that is curved distally.
The surface of the root is convex and
smooth

36. Surface anatomy of the crown
Elevations:
•The buccal surface is convex with the maximum
convexity is at C 1/3 representing cervical ridge.
•The middle lobe is prominent
buccally forming BUCCAL ridge.
Depressions:
Shallow depressions are present
mesial and distal to the B ridge

37. Lingual outline and surface anatomy of the crown
M and D outlines are convex with
marked lingual convergence .
The L cusp is short and small reaching 2/3 the crown
length and has a pointed tip.
Cervical line: is convex root wise.
Elevations: The lingual surface is convex
with the maximum convixty at M 1/3
Depessions: ML developmental groove at
the ML line angle.
M
D

38. Geometric outline of the proximal surfaces
Distal surface
Mesial surface
Rhomboid in shape
With narrow occlusal
table
Lingual inclination is well prominent

39. Outlines of proximal surfaces
Distal surface
Mesial surface
Buccal outline is convex with the maximum convexity at
C 1/3 representing …….
Lingual outline is convex with maximum convexity at
M1/3
Cervical line curves occlusally and decreased distally

40. Outlines of proximal surfaces.
Distal surface
Mesial surface
Occlusal outline: the two cusps are not in the
same level
The B cusp is centered above the root. This is due
to the presence of lingual inclination.
The L cusp tip is in line with the lingual border of the
root.

41. Outlines of proximal surfaces
Distal surface
DMR in 4 is straight
and at right angle to
the axis of the tooth.
Mesial surface
MMR is inclined from
B to L surface to B
cusp ridge.
DMR is occlusal than MMR (unique characteristic of this
tooth).

42. Proximal surface anatomy
Distal surface
Mesial surface
M & D surfaces are smooth and convex except area
cervical to contact area it’s concave.
nearly at the same level
Contact area
it’s broader, cervically
and lingually
positioned.
ML developmental groove
is present at the junction
of L and M surfaces.

43. Outline and surface anatomy of the root
Distal surface
Mesial surface
B & L outlines are nearly straight and parallel
cervically then taper apically to a blunt apex
The surface is more
convex
The surface is smooth
and flat with deep
developmental groove

44. GEOMETRIC OUTLINE OF THE OCCLUSAL
ASPECT
It’s diamond-shaped.
D
Lingual convergence is sharp.
Mesial outline is slightly curved.
Distal outline is more convex.
M

45. Surface anatomy of occlusal aspect:
Elevations:
B triangular ridge.
L triangular
ridge.
M & D marginal ridges
Transverse ridge

46. Depressions:
Central developmental groove
M and D triangular fossae.
Mesiolingual developmental groove

47. Mandibular second premolar
It has 5 surfaces:
Buccal
Lingual
Mesial
occlusal
Distal

48. Geometric outline of the crown
• Buccal and lingual surfaces have trapezoid
shape with the shortest uneven side cervically.

49. Buccal outlines and surface anatomy
4
5
B cusp
B cusp
pointed and long
short and less pointed
Well developed B ridge
Not well developed B
ridge
Blunt apex
Pointed apex

50. Lingual outline and surface anatomy
4
5
Two cusp type
The L cusp is short and small
reaching 2/3 the crown length
and has a pointed tip.
L cusp is shorter and
smaller than B cusp but
larger than of 4
The lingual surface is convex
with maximum convixty at M 1/3
The surface is convex
with maximum convixty
at O 1/3.
No MLDG
ML developmental groove at
the ML line angle.

51. Three cusp type:
5
ML cusp is longer and larger than
DL cusp.However, both of them are
shorter than the B cusp and the ML
cusp is less pointed.
The surface is convex with the
maximum convixty at O 1/3.
M
The Lingual developmental groove is
between the 2 lingual cusps
D

52. Proximal outlines
4
5
Rhomboid in shape with
Rhomboid in shape with
narrow occlusal table.
narrow occlusal table.
Lingual inclination well prominentLingual inclination less prominent

53. 5
4
Maximum convexity at M1/3
The L cusp is short and small
reaching 2/3 the crown
length
Maximum convexity at O1/3
L cusp is shorter and
smaller than B cusp but
larger than of 4
The B cusp centered over the B cusp tip on line with junction
root.
of B & M 1/3 of the root.
The mesial MR is oplique
while distally is straight
The mesial and distal
marginal ridges are straight

54. Mesial surface
Distal surface
Three cusp type:
ML cusp is longer and
larger than DL cusp.
DL cusp is shorter and
smaller than ML cusp.
Both lingual cusps are shorter than the buccal cusp
and the ML cusp is less pointed.
Surface anatomy is simillar to that of 4

55. Geometric outline of the occlusal surface
4
5
It is diamondshaped.
It has two cusps.
Lingual convergence is sharp.
Two cusp type:
The outline is oval
Slight lingual convergence
Three
cusp
type:The
outline is
square
no lingual
convergenc

56. Surface anatomy of occlusal aspect:
4
5
Elevations:
Buccal triangular ridge.
Lingual triangular ridge.
Transverse ridge
M & D marginal ridges

57. 4
5
Depressions:
Central developmental groove
M and D triangular fossae.
Mesiolingual developmental
groove
Central developmental
groove
H or U shapped.
M and D triangular fossae.

58. Lower 5 (Three cusp type):
Elevations:
Buccal triangular ridge.
Lingual triangular ridges (ML
&DL).
M & D marginal
ridges
Depressions:
Central developmental groove Y
shape D triangular
M and
fossae with M and D pits
.