1. Mandibular Molars
Howard Chi, D.M.D.

2. Learning Objective
• Anatomy of the mandibular molars

3. Buccal Aspect Of
Mandibular Molars
• Crown Shape
– The crowns of
mandibular molars are wider mesiodistally than
high cervico-occlusally (greatest extent on first
molars)

4. Buccal Aspect Of
Mandibular Molars
• First Molar Cusps
– The mesiolingual cusp is the highest and widest
– The first molar has the largest mesiodistal dimension
of any tooth
– First molars usually possess three buccal cusps
123

5. Buccal Aspect Of
Mandibular Molars
• First Molar Cusps
– The mesiobuccal is the largest, widest, and highest
cusp on the buccal side
– The distobuccal cusp is slightly smaller, shorter, and
may be sharper than the mesiobuccal
– Distal cusp is on the DB line angle and is the
smallest of the five cusps
LMS
DB Line angle

6. Buccal Aspect Of
Mandibular Molars
• First Molar Cusps
– The distolingual cusp is the second highest cusp when
the tooth is oriented vertically
– Even though the lingual cusps are higher than the
buccal cusps, clinically the lingual cusp tips are at a
lower level than the buccal due to the lingual tilt of the
tooth
2nd highest

7. Buccal Aspect Of
Mandibular Molars
• Grooves Of The First Molars
– The mesiobuccal groove separates the mesiobuccal
and distobuccal cusp
– There may be a deep pit at the cervical end of this
groove
– This pit can be a site of caries
MB groove
Buccal
Pit

8. Buccal Aspect Of
Mandibular Molars
• Grooves Of The First Molar
– The distobuccal groove separates the distobuccal
cusp from the distal cusp
– It is shorter than the MB groove and not frequently
pitted
DB groove

9. Buccal Aspect Of
Mandibular Molars
• Second Molar Cusps
– Four cusps are present on lower second molars
– MB cusp is usually wider mesiodistally than the DB
cusp
– The lingual cusp tips are usually visible from the
buccal aspect
D M

10. Buccal Aspect Of
Mandibular Molars
• Grooves Of The Second Molar
– The buccal groove separates the MB cusps from the
DB cusp
– May end in the middle of the buccal surface in a pit
D M
Buccal groove

11. Buccal Aspect Of
Mandibular Molars
• Proximal Contacts
– Same as all molars
– Mesial: Junction of the occlusal and middle thirds
– Distal: Middle third of crown

12. Buccal Aspect Of
Mandibular Molars
• Cervical Line
– CEJ is nearly straight across the buccal surface on lower
first and second molars
– Occasionally a point of enamel will dip down nearly into
the root bifurcation
– Can also have this type of projection on the lingual, this
could lead to periodontal problems
Enamel projection

13. Buccal Aspect Of
Mandibular Molars
• Taper To The Cervical And The Distal
– There is proportionally more tapering of the crown
from contact areas to the cervical line on first
molars than second molars because of the bulge of
the distal cusp
#31 #30

14. Buccal Aspect Of
Mandibular Molars
• Variations In Mandibular Molar Crowns
– The distal cusp is absent one fifth of the time
– A four-cusp molar may not always be a
second molar - rely on tooth position to aid in
determination
Absent 1/5 of
the time

15. Roots Of
Mandibular Molars
• Both mandibular first and second molars
have two roots (one mesial and one distal)
• Both roots are nearly twice as long as the crown

16. Roots Of
Mandibular Molars
• The root bifurcation of a mandibular first
molar is near the cervical line
• A depression exists between the cervical line
and bifurcation
• The root trunk relatively short (shorter than
lower second molars)
Root depression
Short
root
trunk

17. Roots Of
Mandibular Molars
• Roots of first molars are widely separated
• Second molars have more parallel roots
• Roots may possess a distal curve in the
apical portion
Note distal bend in root

18. Roots Of
Mandibular Molars
• From the buccal aspect can
see the distal surface of the mesial root because
it is twisted on the trunk
• The distal root is straighter than the mesial
root and may possess a pointed apex
• The apex of the mesial root may be in line with
the mesiobuccal groove

19. Lingual Aspect Of
Mandibular Molars
• Crown Shape From The Lingual
– Mandibular first and second molar crowns taper to
the lingual
– This lingual taper is more evident in first molars
– The lingual cusps are longer and more pointed than
the buccal cusps
#30

20. Lingual Aspect Of
Mandibular Molars
• Crown Shape From The Lingual
– The mesiolingual cusp is usually longer and
wider (slightly) than the distolingual cusp
#30
ML DL

21. Lingual Aspect Of
Mandibular Molars
• Grooves
– The lingual groove separates the mesiolingual cusp
from the distolingual cusp
– Terminates in the occlusal third with no pit

22. Lingual Aspect Of
Mandibular Molars
• Cervical Line
– The CEJ is relatively flat mesiodistally
– Can dip cervically between the roots over the
bifurcation (similar to buccal)
– A depression can be seen between the cervical line
and the bifurcation

23. Roots Of
Mandibular Molars
From The Lingual
– On first molars, root trunk appears longer on the
lingual than the buccal
– This is due to the fact that the cervical line is more
occlusal on the lingual surface

24. Roots Of
Mandibular Molars
From The Lingual
• The roots are narrower on the lingual aspect
than the buccal
• Can often see the mesial aspect of the mesial
root due to the twisting on the trunk
• Can see the distal side of the distal root
because of taper to the lingual
Mesial

25. Proximal Aspect
Of Mandibular Molars
• Crown Shape From The Proximal
– Appear relatively short occlusocervically compared
to faciolingual dimension
– The crowns are tilted lingually on the root base
– The buccal outline is convex in the cervical third

26. Proximal Aspect
Of Mandibular Molars
• Crest Of Curvature
– The height of contour on the buccal surface is
within the cervical third
– On molars this buccal bulge is called the buccal
cervical ridge
– It is more prominent on second molar than first
molars
#30

27. Proximal Aspect
Of Mandibular Molars
• Cusp Height
– The lingual cusps are more conical and pointed
than the buccal
– They are the largest of the four to five cusps
#30

28. Proximal Aspect
Of Mandibular
Molars
• Distal Tilt
– Due to the distal tilt of the crown and the sloping of
the occlusal surface, most of the occlusal surface and
all cusps can be seen from the distal
#30 Distal #31 Distal

29. Proximal Aspect
Of Mandibular
Molars
• Taper To The Distal
– On both first and second molars the crown is more narrow
on the distal than the mesial
– Can see some of the buccal and lingual surface from the
distal due to this taper
#30 Distal #31 Distal

30. Proximal Aspect
Of Mandibular
Molars
• Cervical Line
– The mesial CEJ of both first and second molars slopes
occlusally from buccal to lingual
– The distal cervical line is nearly straight

31. Proximal Aspect
Of Mandibular
Molars
• Marginal Ridges
– The mesial marginal ridge is concave buccolingually
– Usually longer on first molars than second and
V-shaped on the second

32. Occlusal Aspect Of Mandibular Molars
• Lingual Inclination
– Due to lingual inclination a considerable portion of
the buccal aspect can be seen from this view
– The molars are wider mesiodistally than
faciolingually

33. Occlusal Aspect Of Mandibular Molars
• Shape: Rectangular Or Pentagon
– The second molar is roughly rectangular
– The first molar with the distal cusp is more like a
pentagon
– The two mesial cusps are larger than the two distal
cusps
D M M D

34. Occlusal Aspect Of Mandibular Molars
• Taper To The Distal And Lingual
– The crown is narrower buccolingually on the distal
than the mesial
– The crown is narrower mesiodistally on the lingual
than the facial
D M M D

35. Occlusal Aspect Of Mandibular Molars
• Taper To The Distal And Lingual
– The widest portion of the crown of a second molar
buccolingually is opposite the mesial cusps
– The widest portion of the crown of a first molar
buccolingually is opposite the distobuccal cusp
D M M D

36. Occlusal Aspect Of Mandibular Molars
• Ridges
– On both first and second molars the MB and
ML cusp’s triangular ridges
form a transverse ridge
– The same is true for the DB
and DL cusps
– Since lingual cusps are taller, they possess
longer triangular ridges than the buccal

37. Occlusal Aspect
Of Mandibular
Molars
• Fossae
– Mandibular molars possess three fossae, a large
central fossa, a smaller mesial, and the smallest
distal fossa
– Each or all may possess a pit

38. Occlusal Aspect
Of Mandibular
Molars
• Grooves: First Molar
– The central groove is more zigzag or crooked in its
mesiodistal course
– There are two buccal grooves instead of one found
on lower second molars
MB Groove
DB Groove

39. Occlusal Aspect
Of Mandibular
Molars
• Grooves: Second Molar
– Groove is simpler than first and resembles a cross
– Central groove is straighter than that of the first
molar
– Buccal and lingual grooves are usually continuous

40. Mandibular
Third Molars
• Shape And Relative Size
– Shortest of mandibular teeth
– Crown may resemble a first or second molar
– Generally have bulbous crowns
#32 Buccal
#32 Distal

41. Mandibular
Third Molars
• Distal Tip
– The crown tips distally and the distal half of the
crown is noticeably shorter

42. Mandibular
Third Molars
• Cusp Size
– Lingual cusps are the longest and largest, with ML
being biggest
• Grooves
– Irregular groove pattern with multiple
supplemental grooves

43. Mandibular
Third Molars
• Roots
– The two roots tend to be short and are often fused
– If the roots are separate the root trunk will be long
– Can possess one or more extra roots
#32 Lingual #32 Mesial