1
Q
Mesiobuccal cusp
A
- The mesiobuccal
cusp has the greatest
mesiodistal dimension
66% of the time.
2
Q
Buccal developmental groove
A
- There is a single buccal
developmental groove
ending in the middle of
the buccal surface. - A pit may be present at
the end of the groove,
but the pit occurs less
frequently than it does
on the first molar, and
it’s less likely to be
carious.
3
Q
Mesial proximal contact
A
- The mesial proximal
contact has been
located at the junction
of the occlusal and
middle thirds (drawn
too far occlusally). - It has also been
noted that this
contact is positioned
further cervically than
the mesial contact of
the first molar (the
normal progression).
4
Q
Distal proximal contact
A
- The distal proximal
contact has been
described as centered
occlusocervically in
the middle third. - This is located cervical
to the mesial proximal
contact.
5
Q
Buccal cervical ridge
A
- The buccal cervical
ridge (buccogingival
ridge) is frequently
prominent on second
molars. - It is more prominent
mesially than distally.
6
Q
Root lengths
A
- The mesial root was
longer than the distal
root by an average of
0.9 mm when measured
on 296 teeth. - Virtually the same as
the first molar (mesial
root was 1 mm longer).
7
Q
Root parallelism
A
- The root axes are
nearly parallel.
8
Q
Root form
A
- The distal root has a
tendency to be more
nearly round (in cross
section). - The mesial root is more
oval or even kidney
bean-shaped (due to
the distal depression.
9
Q
Root trunk dimension
A
- The root trunk is
longer than the first
molar root trunk.
10
Q
Root trunk form
A
- There is a depression
on the root trunk from
the cervical line to the
furcation.
11
Q
Root separation
A
- The roots are not
widely separated.
12
Q
Root curvature
A
- Both root apices
frequently curve
toward the midline
of the tooth similar
to the handles of a
pair of pliers. - Alternately both roots
may curve distally.
13
Q
Proximal surface visibility
A
- Little if any of the
mesial and distal
surfaces are visible
from the lingual since
there is very little taper
of the crown towards
the lingual.
14
Q
Lingual cusp dimensions
A
- The lingual cusps are
taller than the buccal
cusps. - The mesiolingual cusp
is usually slightly wider
mesiodistally than the
distolingual cusp.
15
Q
Lingual cusp form
A
- Both lingual cusps
possess similar
sharpness.
16
Q
Lingual groove
A
- The lingual groove
may terminate on the
occlusal surface or
it may extend onto the
lingual surface in the
occlusal third (shown).
17
Q
Buccolingual crown width
A
- The greatest
buccolingual
width is found in
the mesial half at
the location of the
buccal cervical
ridge.
18
Q
Crown outline
A
- The outline has
been described
as rectangular
and also as
nearly forming
a parallelogram. - This one is
a rhombus.
19
Q
Mesiobuccal prominence
A
- There is a
prominent bulge
(buccal cervical
ridge) on the
mesiobuccal
aspect of the
crown.
20
Q
Distal outline
A
- The distal surface
is more convex
and rounded than
the mesial surface
which is nearly
straight buccolingually.
21
Q
Lingual crown convergence
A
- The crown
tapers lingually,
making the crown
slightly wider
mesiodistally on
the buccal aspect.
22
Q
Distal crown convergence
A
- The crown tapers
distally. - Neither taper is as
much as it was in
the first molar.
23
Q
Mesial proximal contact
A
- The buccolingual
position of the
mesial proximal
contact has been
located buccal to the
center of the crown,
near the junction of
the buccal and
middle thirds.
24
Q
Distal proximal contact
A
- The Tooth Atlas
says that the
buccolingual
position of the
distal proximal
contact is located
at the center of
the crown. - It is more often
slightly offset to
the buccal, which
is the traditional
location.
25
Cusp size
* The mesiobuccal
and mesiolingual
cusps are
generally a little
larger than the
distobuccal and
distolingual cusps.
* The mesiobuccal
cusp is normally
the largest cusp
and the distolingual
the smallest.
26
Cusp height
* The occlusal height
of the 4 cusps has
been listed in the
following order from
tallest to shortest:
1. Mesiolingual
2. Distolingual
3. Mesiobuccal
4. Distobuccal
27
Buccal cusp ridges
* The cusp ridges
of the distobuccal
cusp are located
buccal to the
cusp ridges of the
mesiobuccal cusp.
28
Fossae
* There are 3
fossae: mesial,
central, and distal.
29
"Transverse ridges"
* The Tooth Atlas says
that the triangular
ridges of the mesiobuccal
and mesiolingual
cusps and
also the distobuccal
and distolingual
cusps meet to form
transverse ridges.
* In the traditional
definition we are
using, these are
not true transverse
ridges due to the
presence of a strong
central groove.
30
Developmental grooves
* There are 3
developmental
grooves:
1. Central
2. Buccal
3. Lingual
* The buccal and
lingual grooves meet
the central groove in
such a manner that
a “+” (plus) sign is
formed, dividing
the crown into four
nearly equal parts.
* In Physical
Anthropology
and evolution
this is called a
“+ 4” pattern.
31
Crown outline (mesial view)
* The outline has
been described
as rhomboidal.
32
Buccal height of contour
* The buccal height
of contour has been
located in the cervical
third of the crown.
33
Lingual height of contour
* According to the Tooth
Atlas the lingual height
of contour is located in
the middle third, but
it’s sometimes located
more occlusally, at the
junction of the occlusal
and middle third.
* Along with the
mandibular first
molar, this is the
largest height of
contour measurement
of any tooth in the
mouth (1 mm).
34
Buccolingual root width
* The buccolingual
width of the mesial
root is greater than
the distal root, thereby
preventing the distal
root from being visible.
35
Root depressions
* Root depressions
are common on both
the mesial and distal
surfaces of the mesial
root, which gives this
tooth two mesial canals
approximately 98% of
the time (first molar
was 100% of the time).
36
Marginal ridge location
* Typically, the
distal marginal
ridge is located
farther cervically
than the mesial
marginal ridge.
37
Bucolingual root width
* The distal root is
narrower buccolingually
than the
mesial root.
38
Root depressions
* A depression on
the mesial surface
of the distal root (not
visible in this view)
may cause the distal
root to have two canals
approximately 8% of
the time (first molar
was 10% of the time).
