The document details the anatomical characteristics and distinguishing traits of mandibular premolars, focusing on both the first and second premolars' morphology. It describes variations in crown shape, cusp size, contact areas, and occlusal features, highlighting differences between the two types (two-cusp and three-cusp). Key aspects addressed include the shapes, dimensions, and grooving patterns of the occlusal surfaces, as well as root characteristics.

1. Anatomy of Mandibular premolars

2. Type traits of mandibular premolars
• 1. 2- cusp type with 1 lingual cusp
• 2. 3-cusp type with 2 lingual cusps

3. Distinguishing characteristicsof mandibular premolars
• Generally
– The mandibular 1st premolar has a longer crown and a
shorter root than the 2nd premolars.
– The mandibular 1st premolar is longer overall than 2nd

4. Buccalaspect of mandibular premolars
• 1. Crown shape: (roughly pentagonal)
1st premolar: nearly symmetrical except for a shorter
mesial cusp ridge and a distal bulge of the crown

5. Buccal aspect of mandibular premolars
• 1. Crown shape: (roughly pentagonal)
– 2nd premolar: buccal cusp is less pointed and cusp
slopes are less steep than on the mandibular premolar

6. Buccal aspect
• 2. Notches on the cusp ridges:
– Notches often seen on –
mesiobuccal cusp ridge in
mandibular 1st premolars
– Notches often seen on
distobuccal cusp ridge in
mandibular 2nd premolars

7. Buccal aspect
• 3. Cervical lines:
• The cervical line of the
mandibular 1st premolar is
more rounded mesiodistally,
while that of the 2nd premolar
is more flat

8. Buccal aspect
• 4. Contact areas – Mesial:
– 1st and 2nd premolars –
near junction of occlusal
and middle third

9. Buccal aspect
• 5. Contact area – Distal
– 1st premolar distal contact
area is more occlusal than
the mesial contact area

10. Buccal aspect
• 6. Contact area – Distal
– 2nd premolar has a distal
contact located more cervical
than the mesial contact area,
as is usually the case with
posterior teeth

11. Lingual aspect of mandibular premolars
• 1. Crown shape:
– Mandibular first premolar
crown tapers (converges) to the
lingual (narrower on lingual
side that buccal)

12. Lingual aspect of mandibular premolars
• 1. Crown Shape:
– Mandibular 2nd premolar with 1
lingual cusp, crown tapers to
lingual
– Mandibular 2nd premolar with 2
lingual cusps, crown is as wide or
wider mesiodistally than the
buccal

13. Lingual aspect
• 2. Cusp Size and Shape:
– Mandibular 1st premolar
lingual cusp is small and
pointed
– Most of the occlusal surface
can be seen from this aspect

14. Lingual aspect
• 2. Cusp Size and Shape:
– Mandibular 2nd premolar with 1
lingual cusp:
– Lingual cusp is smaller than
buccal cusp, but larger than
lingual cusp of 1st premolar

15. Lingual aspect
• 2. Cusp Size and Shape:
– Mandibular 2nd premolar with
2 lingual cusps:
– Ml cusp is larger than the DL
cusp, with the L groove
between them and onto the
lingual crown surface

16. Lingual aspect
• 3. Marginal Ridges:
– Mandibular 1st premolar:
– Only tooth in the mouth where
the mesial marginal ridge is
more apical than the distal
marginal ridge

17. Lingual aspect
• 3. Marginal Ridges:
– Mandibular 2nd premolar:
– Mesial marginal ridge is more
occlusal than the distal marginal
ridge (as found in all other teeth)

18. Lingual aspect
• 4. Mesiolingual groove:
– Frequently seen on
mandibular 1st premolar only

19. Proximal aspect of mandibular premolars
• 1. Crown Shape – Rhomboid:
– The crowns of both premolars tilt
lingually, but the mandibular 1st
premolar tilts more lingually than
the mandibular 2nd premolar

20. Proximal aspect of mandibular premolars
• 1. Crown Shape – Rhomboid:
– In both premolars, the
lingual cusps are shorter
than the buccal cusps

21. Proximal aspect
• 2. Mesiolingual groove:
– Often present on mandibular
first premolar between the mesial
marginal ridge and the mesial
slope of the lingual cusp
– Not present in mandibular
second premolar

22. Proximal aspect
• 3. Height of Contour:
– Mandibuar 1st premolar
• Buccal- cervical 1/3
• Lingual – middle 1/3

23. Proximal aspect
• 3. Height of Contour:
– Mandibular 2nd premolar
• Buccal- junction of cervical
and middle 1/3
• Lingual – middle 1/3

24. Proximal aspect
• 4. Cervical Lines:
– Both premolars have greater
curve on the mesial than the
diastal

25. Proximal aspect
• 5. Root (proximal):
– Both premolars generally
consists of one root
– The mandibular 1st premolar
occasionally will have a
furcated root

26. Proximal aspect
• 6. Root Depressions:
– Mandibular 1st premolar – have a
shallow root depression in the apical
and middle third of both mesial and
distal root surface.

27. Proximal aspect
• 6. Root Depressions:
– Mandibular 2nd Premolar – have
a distal root depression in the
middle third of the root, but no
mesial depression

28. Occlusal aspect of mandibular first premolars
• 1. Outline:
– Have much variation in
occlusal morphology
– Outline is not symmetrical
(more bulky on the distal)

29. Occlusal aspect of mandibular first premolars
• 1. Outline:
– Often appears as if the mesial
side has been pushed inward
(mesiolingual corner)

30. Occlusal aspect of mandibular first premolars
• 1. Outline:
– Tip of the buccal cusp is near
the center from occlusal view
– Lacks a prominent buccal
ridge
– Cusp ridges are nearly
straight lines

31. Occlusal aspect of mandibular first premolars
• 1. Outline:
– Crown is somewat diamond
shaped converging lingually
– Shape of the crown is
asymmetrical

32. Occlusal aspect of mandibular first premolars
• 1. Outline:
– Mesial and distal marginal
ridges may converge lingually

33. Occlusal aspect of mandibular first premolars
• 2. Ridges, Fossae, Grooves:
– Due to size of cusp, the buccal
triangular ridge is long
– Join the shorter lingual
triangular ridge
– Often may meet smoothly and
form a uninterrupted
transverse ridge

34. Occlusal aspect of mandibular first premolars
• 2. Ridges, Fossae, Grooves:
– The transverse ridge may be
crossed by a shallow central
groove extending from mesial
to distal fossa
– This is rare

35. Occlusal aspect of mandibular first premolars
• 2. Ridges, Fossae, Grooves:
– The grooves of the first premolar are fewer in number,
but may be deeper than those of the second premolar
(just like the maxillary)

36. Occlusal aspect of mandibular first premolar
• 2. Ridges, Fossae, Grooves:
– Possess a mesial and distal fossa
– Both are circular, not triangular
– Distal fossa is usually larger and deeper.

37. Occlusal aspect of mandibular secdond premolar
• 1. Outline – Two cusp version:
– Crown is round or oval shaped with a square occlusal
table

38. Occlusal aspect of mandibular secdond premolar
• 1. Outline – Two cusp version:
– Ther is slightly more bulk in the mesial half
buccolingually than in the distal half

39. Occlusal aspect of mandibular secdond premolar
• 2. Ridges, Fossae, Grooves – two cusp version:
– Lingual cusp smaller than buccal cusp
– Possess more supplemental grooves

40. Occlusal aspect of mandibular secdond premolar
• 2. Ridges, Fossae, Grooves – two cusp version:
– Possess a curved central groove with no lingual groove
– This groove can be fairly straight

41. Occlusal aspect of mandibular secdond premolar
• 1. Outline – Three cusp version:
– When lingual cusps are large, the occlusal surface is
broader on thwe lingual

42. Occlusal aspect of mandibular secdond premolar
• 1. Outline – Three cusp version:
– Often have greater bulk buccolingually in the distal not
the mesial
– The ML cusp is usually larger than the dl cusp

43. Occlusal aspect of mandibular secdond premolar
• 2. Ridges, Fossae, Grooves – three cusp version:
– Possess three triangular ridges converging towards the
central fossa
– There is no transverse ridge

44. Occlusal aspect of mandibular secdond premolar
• 2. Ridges, Fossae, Grooves – three cusp version:
– Has a central fossa (unique) shifted towards the distal
– Lacks a central groove
– Mesial groove present

45. Occlusal aspect of mandibular secdond premolar
• 2. Ridges, Fossae, Grooves – three cusp version:
– Possess a lingual groove that separates the two lingual
cusps
– This groove completes the Y shaped occlusal groove
pattern