Permanent Maxillary 1st premolar

1. By
Dr. Abhishek Solanki

2. INTRODUCTION
 Premolars are so named because they are
placed between the anterior teeth and the molars
(pre = before)
 Premolars assist canines & molars in tearing and
chewing food
 Have two cusps (bicuspid) & two roots (buccal &
lingual)
 Eruption : at 10-11 years

3. TOOTH NUMBERING
 Universal : #5 , #12
 Z-P : 4 4
 FDI : 14, 24

4. CHRONOLOGY
 First evidence of calcification :1.5 – 1.75 yrs
 Enamel Completion : 5-6 yrs
 Eruption : 10-11 yrs
 Root completion : 12-13 yrs

5. DIMENSIONS (in mm)
Cervico-occlusal Length of Crown 8.5
Length of Root 14
Mesiodistal Diameter of Crown 7
Mesiodistal Diameter of Crown at Cervix 5
Labio- or Bucco-lingual Diameter of Crown 9
Labio- or Bucco-lingual Diameter of Crown at Cervix 8
Curvature of Cervical Line—Mesial 1
Curvature of Cervical Line—Distal 0

6. Buccal Aspect
 Crown : Pentagonal shaped
 Crown closely resembles to maxillary
canine and second premolar
 Mesial margin joins the mesio-occlusal
slope to create an obtuse mesio-occlusal
angle

7.  Contour of the mesial outline is concave
from the contact area to the cervical line
 The mesial slope of the buccal cusp is
longer than distal slope, which is the
opposite of canine
 Disto-occlusal angle is a little less
prominent and the cervical concavity is not
as deep

8.  Occlusal margin of this tooth is, similar to
the incisal margin of the maxillary canine
 Buccal ridge
 Mesio-buccal & distobuccal developmental
depressions on each side of buccal ridge

9. Lingual Aspect
• The crown tapers towards the lingual aspect
• The lingual cusp is shorter than the buccal
cusp
• The lingual cusp is smooth from the cervical
portion to the area near the cusp tip

10. • The cusp tip is pointed with mesial and
distal slope meeting at an angle of about
90 degrees
• Small portion of the buccal cusp can be
seen from this aspect
 Smoothly convex in all directions
 There is no clearly defined lingual ridge

11.  Mesial and distal outlines are normally
somewhat convex & shorter than the same
outlines of the buccal surface
 Lingual cusp tip is not as sharply pointed as
the buccal cusp tip
 The mesio-occlusal slope is shorter than the
disto-occlusal slope

12. Mesial Aspect
• From the mesial and distal aspect both the
buccal and lingual cusps are visible
• A well developed mesial marginal ridge
and a mesial marginal developmental
groove is present
• In the middle of the mesial surface is the
mesial developmental depression which
continues beyond the cervical line

13.  Mesial concavity
 Shape of the mesial surface is trapezoidal
 Buccal outline is generally convex, with
the height of contour in the cervical third
 Lingually the outline takes the form of
an even arc, with the height of contour
in the middle third

14.  Occlusal margin is irregularly concave
and the majority of it is made up of the
mesial marginal ridge.
 A prominent mesial marginal groove is
usually present indenting the occlusal
margin almost two-thirds of the way
from the buccal to the lingual outline.

15. Distal Aspect
 There is no developmental depression or
groove on this aspect, instead it is convex
at almost all points
 The curvature of the cervical is less on this
aspect
 The contact area is near the junction of
occlusal and middle third
 distal is remarkably similar to the mesial
surface, although it is slightly shorter
occluso-cervically.

16.  Lingual margin is almost symmetrical & is
quite convex, especially in middle third,
where height of contour is located
 Occlusally, distal is similar to mesial aspect,
except that marginal ridge is located at a
more cervical level
 There is normally no marginal groove

17. Occlusal Aspect
• Within cusp ridges and marginal
ridges the following are present
TBC & TLC : Tip of Buccal & Lingual
cusp
BTR & LTR : Buccal & Lingual
Triangular ridge
DBDG: disto-buccal developmental
groove
DTF & MTF : Mesial & Distal
triangular fossa
CG : Central groove

18.  outline of crown can be described as
hexagonal or six-sided and it is wider
buccolingually than mesiodistally
 prominent buccal ridge is primary
contributor to generally convex buccal
outline
 lingual margin is evenly convex, almost
in a semicircle
 Proximal margins are relatively straight
& they converge toward lingual

19. Root
• Most Maxillary first premolars have 2 roots,
but one and three roots can also be seen
• Two roots : buccal and lingual
• Buccal portion of the root resembles canine

20. • The root when viewed from the proximal side shows a big
trunk and bifurcation area from where the buccal and
lingual root separate
• A developmental depression is seen on the mesial aspect
of the trunk
TRUNK

21. REFERENCES
 CONCISE DENTAL ANATOMY & MORPHOLOGY :
JAMES L FULLER
 DENTAL ANATOMY, PHYSIOLOGY & OCCLUSION:
WHEELER’S
 TEXTBOOK OF DENTAL ANATOMY, PHYSIOLOGY &
OCCLUSION: RASHMI GS (PHULARI)
 INTERNET