Maxillary first premolar

1. Maxillary 1st Premolar

2. Maxillary premolars
2 in the right(#14|#15) and 2 in the left (#24|#25)
Premolars are so named because they are anterior to
the canines and molars
Assist the Canines and Molars in tearing and
chewing food
Have two cusps & sometimes one or two roots

3. Maxillary First Premolar
FUNCTION:
1. Assist in shearing and cutting
2. Support the corners of the mouth
• Has 2 cusps buccal and lingual
• Crown is angular shape
• Crown is shorter than canine
• Most have 2 roots and 2 canals

4. Chronology:
First evidence of calcification: 1 ½ - 1 ¾ year
Enamel completed 5-6 years
Eruption 10-11 years
Root completed 12-13 years

5. Measurement Table
Cervico-cocclusal
length of
the crown
Length of
root
Mesiodistal
diameter of
crown
Mesiodistal
diameter of
crown at
cervix
Labio- or
buccolingu
al diameter
of crown
Labio- or
buccolingu
al diamter
of crown at
cervix
Curvature
of cervical
line- Mesial
Curvature
of cervical
line- Distal
Dimensions* 8.5 14.0 7.0 5.0 9.0 83.0 1.0 0.0

6. Buccal Aspect
Crown: roughly
trapezoidal
Mesial outline: Slightly
concave
Distal Outline: nearly
straight
Mesial cusp slope is
nearly straight while the
distal cusp slope is
slightly convex
D M

7. Surface of the crown
Buccal surface: convex
Middle lobe : prominent
bucally forming the
BUCCAL RIDGE
Shallow depressions are
present mesial and distal
to the buccal ridge.

8. Contact areas: Mesial is at
middle third while Distal is at
occlusal third
Cervical line: convex root wise
Mesial & Distal Outline of the
Root: It tapers to a pointed
apex that is slightly curved
distally.
If two roots are present, the
lingual root is hidden behind
the buccal root as it’s shorter
and narrower than the buccal
root.
Surface of root: convex and
smooth

9. Lingual Root
Lingual cusp:
 Shorter by 1mm but
sharper than buccal cusp
 Smooth and spheroidal
from cervical portion near
the cusp tip
Mesial and Distal Outlines:
Convex
Cervical line: convex root
wise
Distal slope is longer than
Mesial slope
Lingual surface: convex at
middle ⅓
M D

10. Root
Mesial and Distal Outline
of the root taper to a
pointed apex that is
curved distally
Surface of root: convex
and smooth
Apex: more blunt than
the buccal root apex
If two roots are present,
the lingual root is shorter
and narrower than
buccal root

11. Mesial Aspect
Shape: Trapezoid
Smallest of the uneven
sides is occlusally
Buccal outline: convex with
maximum convexity at
cervical ⅓
Lingual Outline: evenly
convex
Cervical Line: regular in
outline
Curvature occlusally is less
1mm than cervical curvature
on mesial

12. Buccal cusp: Longer than
lingual cusp by 1mm
Buccal cusp tip: below
the center of Buccal root
Lingual cusp tip: One
line with lingual outline
of the lingual root

13. Contact area: at the
middle third & slightly
buccal to midline
Mesial Development
Groove: cross MMR &
location: lingual to the
contact area
Mesial Developmental
Depression: Crown and
continues with between
the roots (canine fossa)

14. Two roots (80%)
Root trunk: about half
the root length
Surface: smooth and
convex

15. One root
Buccal and Lingual
outlines: tapers to a
blunt apex on center of
the crown
Surface: smooth and
convex except for a
shallow depression in
center that is deeper
mesial than distal

16. Distal Aspect
Curvature of cervical
line: less than mesial
surface it is almost flat
Developmental Grooves:
less evident
Root trunk: flattened
with no outstanding
developmentalsigns

17. Occlusal Aspect
Shape: Hexagonal
2 equal buccal sides
(MB,DB)
Mesial side shorter than
distal side
Mesiolingual side shorter
than distolingual side
Crown is wider bucally
than lingually

18. Elevations:
 Buccal triangular ridge
 Lingual triangular ridge
 Mesial & Distal marginal
ridges
Depressions:
 Central developmental
groove
 Mesial and Distal
triangular fossae
 Mesial marginal
developmental groove

19. Pulp Cavity
MD Section BL section
Root canal
Lingual canal is larger and
more accessible
Pulp chamber
2 root canals
Narrow Wider

20. Buccolingual Section
2 well-developed roots that are not fully
separated or 1 broad root
2 root canals
Pulp horns:
 Usually extends further incisally under
the buccal cusp
 Maybe blunted
Pulp chamber floor:
 Located below the cervical level
Pulp chamber:
 Have at least root separation usually
shows the largest-incisal-apical
dimension
Shape of the pulp chamber: square or
root
Root canal:
 Appears to exit at tip of the root | slightly
to labial or lingual

21. Mesiodistal Section
Pulp horns:
 Blunted from the mesial/
distal aspect
Pulp cavity:
 Tapers slightly from
occlusal aspect to apical
foramen
Apical foramen:
 Appears to exit at tip of the
root

22. Cervical cross section
Shape: kidney
Pulp cavity:
Constriction adjacent to
developmental groove
Some roots demonstrate
2 separated root canals