MAXILLARY FIRST PREMOLAR
Dr. Saleem Shaikh
INTRODUCTION
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Posterior teeth
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Present anterior to molars hence named a premolars
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Also known as bicuspids but some may have 3 cusps
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The maxillary premolars develop from 4 lobes, the middle lobe as well as the
lingual lobe is well developed
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The lingual lobe develops to form the lingual cusp and hence no cingulum is
seen.
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The marginal ridges are horizontal and are part of the occlusal surface and
not the lingual surface.
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The crown of the premolars is shorter than that of the canine
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Maxillary first premolar usually has two roots.
BUCCAL ASPECT
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The crown is roughly trapezoidal and
resembles a canine.
The mesial outline is slightly concave from
the cervical line to the mesial contact area.
Mesial contact area is in the middle third
The mesial slope of the buccal cusp is
longer and straight than the distal slope.
The cusp tip is slightly distal to the line
bisecting the buccal surface.
The distal contact area is slightly broader
than the mesial contact area and is in the
middle third
The distal outline below the contact area is
straight.
Buccal ridge is seen.
LINGUAL ASPECT
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The lingual outline is reverse than that of the buccal
cusp
The crown tapers towards the lingual surface hence
the lingual cusp is smaller than the buccal cusp.
Parts of the buccal cusp is also seen
The lingual cusp is smooth and spheroidical from the
cervical line to the cusp tip.
The cusp tip forms an angle of 90 degrees
A well developed lingual ridge is present
The lingual root is also smaller and part of the buccal
root can also be seen.
The lingual cusp is around 1-2 smaller than the
buccal cusp
MESIAL ASPECT
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The outline is roughly trapezoidal, the longest of
uneven sides is towards the cervical portion
The tips of the cusps are always within the
confines of the root trunk.
Most of the maxillary first premolars have a
buccal and a lingual root.
The buccal outline of the crown is convex and
the crest of curvature lies within the cervical
third
From the crest of curvature the outline slopes
towards the cusptip which lies below the center
of the buccal root.
The lingual outline is more convex, the crest of
curvature is in the middle third. The lingual tip
on line with lingual outline of root.
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A distinguishing feature seen on the mesial aspect
is the presence of a depression known as “mesial
developmental depression” which is present
immediately below the mesial contact area and may
continue onto the root.
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The first premolar also has a well defined
developmental groove seen on the mesial marginal
ridge – mesial marginal developmental groove.
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The root trunk is long and bifurcation of the root is
seen in the apical or middle thirds.
DISTAL ASPECT
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Looks similar to the mesial aspect but does
not have the developmental depression or
groove.
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The distal surface is more flattened than the
mesial surface.
OCCLUSAL ASPECT
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The occlusal aspect resembles a six sided
hexagonal structure.
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The buccal sides are equal, the mesial side is
shorter than the distal side and the
mesiolingual side is shorter than the
distolingual side.
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The occlusal surface is circumscribed by the
cusp ridges and the marginal ridges. Both
buccal and lingual cusp can be seen
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A well defined central groove divides the
surface buccolingually
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The central groove extends over the mesial
marginal ridge to form the mesial marginal
developmental groove.
Two grooves join the central groove inside the
mesial and distal marginal ridges –
mesiobuccal and distobuccal developmental
grooves.
At the junction of the grooves are the mesial
and distal developmental pits.
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Two fossas are seen known as the mesial and
distal triangular fossa
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Buccal and lingual triangular ridge can be
seen, buccal ridge is more prominent than the
lingual ridge.
Maxillary
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nd
2
premolar
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Buccal Aspect: The Buccal cusp appears to be
slightly shorter and less pointed than the 1st
premolar.
The mesial cusp ridge is shorter than the distal
cusp ridge (opposite in 1st premolar).
The buccal ridge is not very prominent
15
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Lingual Aspect: the lingual cusp is longer than in
first premolar hence less of the occlusal surface
is visible.
Maxillary
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nd
2
premolar
Mesial aspect: the buccal and lingual
cusps of the second premolar are almost
equal in height.
No developmental depression or groove
is seen on the 2nd premolar
Distal Aspect: root depression on the
distal aspect is greater than on the
mesial surface.
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15
14
14
Maxillary 2nd premolar
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Occlusal aspect:
The crown outline is more rounded and oval rather
than hexagonal.
The central developmental groove is shorter and
irregular. Multiple supplemental grooves are seen
radiating from the central groove.
This gives the occlusal surface of the 2nd premolar a
wrinkled appearance.
Pulp: the 2nd premolar usually has a single pulp canal
whereas the 1st premolar almost always has 2 pulp
canals