dental anatomy , max. first molar

1. Maxillary 1st Molar

2. By Ahmed Reath Jelewi
‫رياض‬ ‫احمد‬‫جليوي‬

4. 1. It is the sixth tooth from the median line.
2. It is the largest tooth in the maxillary arch.
12
3
4
5
6

5. 3. It has large crown with four well-formed cusps
(more pronounced than those on the
opposing lower molar).
The two buccal cusps are more pointed
than the two palatal cusps.

6. 4. A unique feature of the tooth is the presence of
an elevation called tubercle of Carabelli (fifth
cusp) .

8. 5. A unique feature of the tooth is the presence of
an elevation called oblique ridge crossing the
occlusal surface obliquely.
L
B
M D

9. Buccal Aspect
The geometric outline of the crown
is trapezoidal with the short of the
uneven sides cervically.

10.  Distal outline:
 Is nearly straight from the cervical line to
the mesial contact area
 then curves distally to be continuous with
the mesial slope of the mesiobuccal cusp.
 Mesial outline:
 Is convex from the cervical line to the
tip of the distobuccal cusp.
 The crest of curvature is at the middle of
the middle third .
 The distal side of the crown can be seen
from the buccal aspect due to the
obtuse distobuccal line angle.
MD

11.  MESIAL
At the junction of the occlusal and middle third.
 DISTAL
At the center of the middle third.

12.  Two buccal cusps, mesiobuccal and
dislobuccal cusps.
 Each cusp has a tip, a mesial cusp
slope and distal cusp slope.
 The mesiobuccal cusp is broader
than the distobuccal cusp.
M.B.CD.B.C

13.  The mesial and distal slopes of the
mesiobuccal cusp meet at an obtuse
angle
 While the slopes of the distobuccal
cusp meet at right angle
 So the distobuccal cusp is sharper
and at least as long or often longer
than the mesiobuccal cusp.
 Parts of the two lingual cusps can be
seen from the buccal aspect.
M.B.CD.B.C

14.  The cervical line is generally irregular and
slightly convex toward the root.

15.  A buccal developmental groove
separates the two buccal cusps
extending to the middle third.
 The groove fades out cervically,
ending by a transverse dip in
enamel mesially and distally.
Sometimes the buccal groove ends
by a pit.

16.  The roots originate as a
common undivided part on
the base of the crown, this
single common root base is
called root trunk.
 The root trunk of this tooth
divides into three roots; two
buccal and one palatal. The
axes of the roots are inclined
distally.
 The length of root trunk is
about 4 millimeters.
The RootsThe Roots
Left
Right

17.  The mesiobuccal root is slightly longer than
the distobuccal one.
The Roots

18.  The mesiodistal diameter of the lingual surface
is nearly equal to that of the buccal surface.
Lingual AspectLingual Aspect

19.  The Mesial Outline:
◦ is almost straight and forms a right
angle with the mesial slope of the
mesiolingual cusp.
 The Distal Outline:
◦ is smoothly convex and becomes
continuous with the distal slope of the
distolingual cusp (i.e. semicircular)
M.L.C
M.L.C
D.L.C
D.L.C

20.  The two lingual cusps are the only one to be
seen from this aspect (beside the cusp or
tubercle of Carabelli when exist).

21.  The Mesiolingual Cusp:
◦ is the largest and longest cusp of this
tooth.
◦ Its mesiodistal width is about three
fifth of the mesiodistal crown diameter.
 The Distolingual Cusp:
◦ is spheroidal and smooth.
◦ It makes up the remaining two fifth of
the crown diameter.

22.  The fifth cusp or tubercle of
Carabelli is a small elevation,
commonly found in about 60 per
cent of cases on the lingual
surface of the mesiolingual cusp.
 It is outlined occlusally by an
irregular developmental groove.
 If it is well developed, its cusp
ridge is nearly 1.5 mm cervical to
the cusp ridge of the mesiolingual
cusp.

23.  Cervical line is irregular.

24.  A lingual developmental groove divides
unequally the two lingual cusps.
 It ends nearly at the center of the
lingual surface.
 From the end of the lingual groove a
shallow depression extends to the
center of the lingual surface of the
lingual root crossing the cervical line
and fades out at the middle third of the
root.

25. The three roots are seen lingually.
The large palataone l root is conical,
ending in a bluntly rounded apex.
This apex is on a line with the lingual
groove.
Parts of the buccal roots are seen
from this aspect behind the lingual

26.  The geometric outline is roughly
trapezoidal with the uneven short
side occlusally.
 From this aspect the great
buccolingual dimension of this tooth
is evident as in all upper molars.

27.  The crest of curvature is
located at the cervical
third representing the
maximum convexity of
the cervical ridge .
Right
Left
M.B.C
M.B.C

28. The crest curvature is
at the middle third of
the crown.
Left
Right
M.L.C
M.L.C

29.  The mesiobuccal cusp is on a line with the long
axis of the mesiobuccal root.
RightLeft
M.B.CM.B.C

30.  The cervical line is irregular and slightly convex
occlusally.
Left

31.  The mesial contact area is just below
the marginal ridge, nearly at the
junction of the occlusal and middle
thirds of the crown and somewhat
buccal to the center of the crown. Left
Right

32. The Root Trunk
is a little shorter mesially than buccally
(about 3 mm) with a smooth depression
at the bifurcation extending occlusally
and lingually.
The Mesiobuccal Root
is broad and flattened on its mesial
surface.

33.  The Palatal Root
◦ is longer and narrower than the
mesiobuccal root.
◦ The palatal root is the most divergent root
in order to follow the bone around the
maxillary sinus.
◦ It is banana-shaped, extending lingually.
 The Distobuccal Root can not be seen
from this aspect.
◦ It is hidden behind the mesiobuccal one.

34. It is similar to the mesial aspect with
certain variations.
The crown tends to converge distally,
due to the slant of the buccal side.
So, the buccolingual measurement of
the crown distally is smaller than that
mesially, thus part of the buccal surface
can be seen distally.

35.  Is almost straight.
 Occasionally it may curve apically.

36.  The root trunk shows the largest
length distally reaching 5 mm or
more.
 The distobuccal root is narrower
than the other two roots.
DM

37. The geometric outline of the
crown occlusally is somewhat
rhomboidal with acute
mesiobuccal and distolingual
angles and obtuse
mesiolingual and distobuccal
angles.
L
B
M D

38.  The buccolingual measurement of the crown mesially is
greater than distally.
 The mesiodistal measurement lingually is greater than
buccally.
Thus,
 The crown is wider mesially than distally and wider
lingually than buccally .
L
B
M D

39.  The maxillary first molar has four well
developed cusps named according to
their location.
 A small fifth cusp or tubercle of
Carabelli appearing on the lingual
surface of the mesiolingual cusp near
the mesiolingual line angle.
 This tubercle may be ill defined or
absent.

40.  The mesiolingual cusp is the largest followed in
decreasing order of size by the mesiobuccal,
distolingual and distobuccal cusp .
 The fifth cusp (tubercle), if present, is the smallest.
M.L
M.B D.B
D.L

41.  Each of the four cusps has a definite triangular
ridge.
 Union of the triangular ridges of the
mesiolingual and the distobuccal cusps forms
an oblique ridge crossing the occlusal surface
obliquely (characteristic of maxillary molars).

42.  The mesial and distal marginal ridges are
continuous with the adjacent cusp ridges.

43. There are two types :
A - Major fossae:
1- The central fossa
2- The distal fossa
B - Minor fossae:
1- The mesial
triangular fossa
2-The distal triangular fossa

44.  It is near the center of the
occlusal surface, and mesial to
the oblique ridge
 The central fossa contains in its
depth a central developmental
pit.
 It is bounded by the oblique
ridge and the distal and mesial
slopes of the mesiobuccal and
distobuccal cusps respectively.

45.  The distal fossa is roughly elongated and
distal to the oblique ridge.

46.  The small mesial and the minute distal triangular
fossae are immediately distal and mesial to the
mesial and distal marginal ridges respectively .

47. Starting from the central pit of the central fossa
the following grooves radiate:
Starting from the central pit of the central fossa
the following grooves radiate:
The buccal developmental groove extends from
the central pit buccally and continues between the
buccal cusps onto the buccal surface of the crown as
the buccal groove.

48.  The central groove extends mesially from the
central pit to terminate at the apex of the
mesial triangular fossa.

49.  a short developmental groove
radiates from the central pit and
runs transversely and distally
across the oblique ridge to the
distal fossa joining the central
and distal fossae.
 This groove is called the
transverse groove, of the oblique
ridge.

50.  It is irregular developmental groove traverses the
distal fossa from the distal triangular fossa
lingually between the lingual cusps and continues
onto the lingual surface as the 5- lingual
groove.

51.  6- the fifth cusp groove (or tubercle) is distinct,
this groove separates the tubercle from the
mesiolingual cusp and joins the lingual groove.