This document provides information about the permanent mandibular first premolar and differences between the mandibular first and second premolars. It discusses the general features of premolars, including their transitional location between canines and molars. For the mandibular first premolar, it describes the chronology, number of roots, crown and root outlines, contact areas, and surface anatomy from various aspects. It then compares the mandibular first and second premolars, noting differences in their geometric outlines, facial outlines and surface anatomy, lingual outlines, proximal outlines, occlusal aspects, and pulp cavities.

1. PERMANENT MANDIBULAR FIRST
PREMOLAR
AND
DIFFRENCES BETWEEN MANDIBULAR
FIRST AND SECOND PREMOLAR
Dr Monika Negi
MDS
Oral And Maxillofacial Pathology

2. PREMOLARS
There are four maxillary and four
mandibular premolars.
4&4 contact:
 3 & 3 mesially and
 5 & 5 distally
5 & 5 contact:
 4 & 4 mesially and
 6 & 6 distally.
Relations:

3. GENERAL FEATURES OF PREMOLARS
 They are transitional teeth
located between the
canine and molar teeth.
 By definition: Premolars
are permanent teeth distal
to the canines, and
successors to deciduous
molars.
 There are two premolars
per quadrant and are
identified as first and
second premolars.

4. GENERAL FEATURES OF PREMOLARS
 They have usually two
cusps(bicuspid) :
 One large buccal cusp,
 Smaller lingual cusp
 The lower second
premolar may-
sometimes- have two
lingual cusps.

5. MANDIBULAR FIRST PREMOLAR
Chronology:
•Enamel organ appearance: 7 miu.
•Beginning of calcification: 1 ¾ - 2y
•Crown completed: 5 – 6y
•Eruption: 10 – 12y
•Root completed: 12 – 13y

6. Mandibular First Premolar
Buccal Lingual Mesial
Occlusal
Distal
No. of roots
One root

7. Geometric Outline of the Crown
Facial and lingual aspects have
trapezoid out line.
The smallest of the
uneven sides

cervically.

8. Contact areas:
•Mesially and Distally: are nearly at
the same level, just occlusal to the
middle of the crown.
Cervical line:
•convex root wise.
M
Bucc. cusp
pointed and
long
Buccal Aspect Outlines:
•Mesial and distal outlines:
are nearly concave
•Mesial(shorter) and distal cusp
slopes: are also slightly concave
D

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

10. The surface of the root
is convex and smooth.
The M and D outline of the
root tapered to a pointed
apex that curved
distally(similar to canine
but slightly shorter).
Buccal Aspect
 Outline and Surface Anatomy
of the Root

11.  Outlines:
•M and D outlines are convex
Cervical line: is convex rootwise.
Elevations: The lingual surface is convex
with maximum convexity at middle 1/3
•The L cusp is short and small
reaching 2/3 of the length of the
Buccal cusp(has a pointed tip).
Deperssions: Mesio Lingual developmental groove separating
the Mesial Marginal ridge from the Mesial slope of the Lingual cusp.
Lingual AspectLingual convergence:
Lingual surface is narrower than buccal surface.
 Surface Anatomy :
MD

12. Lingual Aspect
MD
•Much of the occlusal and
proximal surfaces can be seen
from this aspect.
•The root is much narrower
than on the buccal surface. It
tapers from the cervix to a
pointed apex.

13. Proximal aspects have
rhomboid shape Mesial Distal
With narrow
occlusal table
Prominent lingual inclination
(much more than any other premolar)
Proximal Aspects

14. Lingual outline is less convex with maximum
convexity at the center of the crown length.
Cervical line is convex occlusally and less curved
distally
 Outlines of proximal aspects
Buccal outline is convex with maximum convexity at
the junction of middle and cervical 1/3 (cervical ridge).
Mesial
Aspect
Distal
Aspect

15. Occlusal margin:
The two cusps are not on the same level
The lingual cusp is shorter by 1/3 length of crown
The Buccal cusp tip centered over the root. This
is due to the prominent lingual inclination.
The L cusp tip in line with lingual border of the root.
Mesial
Aspect
Distal
Aspect

16. DMR is longer, straight
and at right angle to
the axis of the tooth.
(The only post. tooth in
which this is true).
MMR inclined sharply
from B to L surface parallel
to ridge of Buccal cusp
Mesial
Aspect
Distal
Aspect
DMR is occlusal than MMRMMR is cervical than DMR

17. M & D surfaces are smooth & convex except for
the ML groove.
Mesio-lingual
developmental grove
Passes over the MM
ridge(extension of M
groove on the occl. surf.
Contact areas:
 Proximal surface anatomy
nearly at same level
Contact area is broader,
more lingually situated
than the mesial one.
Mesial
Aspect
Distal
Aspect

18.  Outline of the Root
B & L outlines are nearly straight cervically then taper apically
to a pointed apex.
The surface is more convex with a
shallow dev. depres. centered on the
root
The surface is smooth & flat with a
deep dev. groove in the mid.& apical
1/3
Mesial
Aspect
Distal
Aspect
Occasionally the apical 1/3
may be divided into a B. & L.
roots by a deep dev. groove

19. It is diamond-shaped.
Lingual convergence is sharp.
Mesial outline is slightly curved.
Distal outline is more convex.
Occlusal Aspect
The B cusp is much larger than the L cusp.
M D

20.  Surface anatomy of occlusal aspect:
Elevations:
B triangular ridge(long).
L triangular ridge(short).
M & D marginal ridges(well
marked).
Transverse ridge (formed by
union of 2 triang. ridges).

21. Depressions:
Central dev. groove crossing
the transv. ridge.
M(oval) and D(circular)
fossae.
Mesio-lingual develop. groove – extension of M
groove on the occ. surface.
Each fossa has a dev. pit
(called snake eyes)
M D
..

22. PULP CAVITY
Buccal p. horn: more
pronounced than the
lingual.
Cross sec. at the cervix:
rounded or oval
BLMD
Usually have a single RC
Resemble that of
The lower canine

23. MANDIBULAR
FIRST PREMOLAR

24. THE 2 TYPES DIFFER MAINLY FROM
THE OCCLUSAL ASPECT. THE
OUTLINES AND GENERAL
APPEARANCE FROM ALL OTHER
ASPECTS ARE SIMILAR.

25. Geometric outline of the crown
Facial and lingual aspects have
trapezoid shape
But wider
cervically
than 4.
Comparison Between
Mandibular First and Second Premolars

26. Facial Outlines and surface anatomy
Crown is smaller & B
cusp is longer &
pointed
Prominent B ridge Less prominent B ridge
Crown is larger & B cusp
is shorter and less pointed
Root: Shorter, narrower with
pointed apex
Root: longer, broader,
with blunt apex
Mandibular First Premolar Mandibular Second Premolar

27. Lingual outline and surface anatomy
The lingual surface is convex with
maximum convexity in middle 1/3(center of
crown)
The L cusp is short and small reaching 2/3
the crown length and has a pointed tip.
ML developmental groove at the ML
line angle.
Two cusp type
L cusp is shorter and smaller than
B cusp but larger than of 4
The surface is convex with
maximum convexity in Occ.1/3.
No MLDG
Mandibular First Premolar Mandibular Second Premolar
Ling. s. not so
narrow as in 1st
premolar
MD D M

28. Three cusp type:
ML cusp is longer and larger than DL
cusp. They both shorter than B
cusp and less pointed.
DM
The surface convex with
maximum convexity at occ.1/3.
The L developmental groove
between the 2 ling. cusps
No ling. convergency.

29. Proximal outlines
Rhomboid in shape with
narrow occlusal table.
Prominent lingual
inclination
Rhomboid in shape with
narrow occlusal table.
Lingual inclination
less prominent
Mandibular First Premolar Mandibular Second Premolar
The crown is wider BLThe crown is narrower BL

30. Maximum convexity at Middle 1/3 Maximum convexity at Occlusal 1/3
B cusp tip on line buccal to the
root axis.
The mesial and distal marginal ridges
are straight
L cusp is shorter and smaller than B cusp
but larger than that of 4
The B cusp centered over the root.
The L cusp is short and small reaching
2/3 the crown length
The mesial MR is oblique while distally
is straight
Mandibular First Premolar Mandibular Second Premolar
The root is
wider BL

31. Three Cusp
Type of
Mandibular
Second
Premolar
ML cusp is shorter than the B cusp
& longer and larger than DL cusp.
DL cusp is shorter and smaller than ML
cusp. Both are seen from this aspect.
Both lingual cusps are shorter than the buccal cusp
and less pointed
Mesial
Aspect
Distal
Aspect
Develop.
depression
Cerv. line: slightly curved. Cerv. line: nearly straight.

32. Occlusal Aspect
Two cusp type
Diamond-shaped.
Lingual convergence
is sharp.
The outline is round
Slight lingual convergence
Three cusp type
The outline
is square
Mandibular First Premolar Mandibular Second Premolar
U- shaped H - shaped
M D
The 3 cusps are
well developed
M D

33. Surface Anatomy of Occlusal Aspect:
Elevations:
B & L triang. ridges
form a transv. ridge.
M & D marginal ridges
Lower 5
Two cusp type
Lower 4

34. Depressions:
Shallow central devel. groove
M(oval) and D(round) fossae.
Mesiolingual devel. gr.
Central devel. groove extending
MD across the occ. surface, over
the transv. ridge.
M and D fossae: Circular.
The D fossa is larger than
the M one
Lower 5
Two cusp type
Lower 4
. .
M D
M D

35. Elevations & Depressions
Each cusp has triang. ridge
that converge toward a
central fossa, which has
cent. pit.
M & D marginal ridges are well marked.
No central devel. gr. or transv. ridge
Three cusp typeLower 5
Three devel. gr.(M,D, & L) radiate
from the cent. Pit : Y-shaped.
The D triang. fossa is smaller than the M one.
M D

36. MANDIBULAR
SECOND PREMOLAR
3 cusp type
2 cusp type

37. PULP CAVITY
MD BL
Cross sec. at the cerv. line
round or oval