MAXILLARY FIRST MOLAR BY DR. VANISHREE M

1. Permanent Maxillary First Molar
DR.VANISHREE.M
DEPARTMENT OF ORAL PATHOLOGY

2. Introduction
• 16 & 26 (FDI sytem)
• Assist mand molars in mastication and
comminution of food
• Three well developed roots, lingual longest
• It is not a succedaneous tooth
• Wider buccolingually
• 4 well developed cusps & cusp of carabelli

3. Objectives
• Clinical significance
• Chronology & Tooth Dimensions
• Labial aspect
• Lingual aspect
• Mesial aspect
• Distal aspect
• Occlusal aspect
• Endodontic Anatomy
• Variations & anomalies
• Summary

4. Clinical significance
• Basis for restorative and prosthodontic treatments in
particular and all phases of dentistry in general
• Knowledge of Pulpal anatomy helps to accomplish the
endodontic treatment.
• Help to understand the functional relation with
adjacent teeth and opposing teeth
• Periodontal instrumentation

5. Chronology of calcification & Eruption
• First evidence of calcification at birth
• Enamel completed 3-4 years
• Eruption 6 years
• Root completed 9 to 10 years

6. Tooth Dimensions
Cervico-
incisal
Length Of
Crown
Length Of
Root
Mesio-
distal
Diameter
Of Crown
Mesio-
distal
Diameter
Of Crown
At Cervix
Labio- Or
Bucco-
lingual
Diameter
Of Crown
Labio- Or
Bucco-
lingual
Diameter
At Cervix
Curvature
Of Cervical
Line-mesial
Curvature
Of Cervical
Line- Distal
Dimensio
ns
Suggeste
d [mm]
7.5
B L
12 13 10.0 8.0 11.0 10.0 1.0 1.0

7. Buccal Aspect
Outline form
• Crown is roughly trapezoidal
• Obtuse distobuccal line angle, distal
side seen
• Parts of four cusps seen

8. …Buccal Aspect
Outline form
• Mesiobuccal cusp broader than
distobuccal
• Mesiobuccal cusp slopes-meet at
obtuse angle
• Distobuccal cusp slopes-meet at 90o
angle

9. …Buccal Aspect
Outline form
• Buccal developmental groove is
equidistant between the mesiobuccal
and distobuccal line angles
• It terminates approx half the distance
from its origin occlusally to cervical line

10. …Buccal Aspect
Mesial outline
• Follows staight path downwards and
mesially curving occlusally as it reaches
crest
• Crest is approx 2/3 the distance between
the cervical line and tip of MB cusp
• Then continues downwards and distally and
becomes congruent with mesial slope of
mesiobuccal cusp

11. …Buccal Aspect
Distal outline
• Outline is convex, surface is spheroidal
• Crest of curvature-half the distance
from cervical line to tip of cusp
• Distal contact area-middle of middle
third

12. …Buccal Aspect
Cervical line
• Does not have much curvature but
generally convex with convexity
towards the roots

13. …Buccal Aspect
Roots
• All three roots may be seen
• The axes of roots inclined distally
• Mesiobuccal root curves distally starting at
the middle third (axis at right angles to
cervical line)
• Distal root staighter with long axis at acute
angle with the cervical line

14. …Buccal Aspect
…Roots
• Bifurcation of buccal roots-4 mm
above cervical line
• Deep developmental groove buccally
on the root trunk
• Roots are twice as long as the crown

15. Lingual Aspect
Outline form
• Gross outline is reverse of that from buccal
aspect
• Only lingual cusps seen (ML-longest cusp)
• Fifth cusp attached to ML surface of ML
cusp
• Cusp ridge of 5th cusp is 2mm cervical to
cusp ridge of ML cusp

16. …Lingual Aspect
..Outline form
• Variation between outline of mesial
and distal surfaces is apparent
• Lingual developmental groove is in
confluent with the outline of
distolingual cusp
• Lingual dev groove starts in centre of
lingual surface

17. …Lingual Aspect
Mesial outline
• Relatively straight line from cervical
line to contact point
• Angle between mesial outline and
mesial slope of mesiolingual cusp-
almost 90o
• Angle between mesial and distal
slopes of mesiolingual cusp= obtuse

18. …Lingual Aspect
Distal outline
• Distolingual cusp rounded
• Semicircular outline created by
distolingual cusp

19. …Lingual Aspect
Roots
• All three roots visible
• Lingual root makes up most of the
foreground
• Lingual root is conical, terminating in a
bluntly rounded apex

20. …Lingual Aspect
..Roots
• All of mesial outline of MB root may be
seen and part of apex
• Distal outline of DB root is seen above
its middle third including all of its
apical outline

21. Mesial Aspect
Outline form
• Mesiobuccal, mesiolingual and 5th
cusps seen
• Mesiobuccal root hides the
distobuccal root

22. …Mesial Aspect
Buccal outline
• Oultine of crown makes a short arc
starting at cervical line to crest
(cervical 3rd)
• Short arc followed by concavity and
then convexity as it progresses
towards cusp tip

23. …Mesial Aspect
Lingual outline
• curves outward and lingually to
same extent as on buccal side
• Crest of curvature is near the
middle third of the crown

24. …Mesial Aspect
…Lingual outline
• If 5th cusp well developed lingual
outline dips inwards
• Mesiolingual cusp is on a line with
the lingual root

25. …Mesial Aspect
• Mesial marginal ridge is in confluent
with the MB and ML cusp ridges
• Marginal ridge is irregular curving
cervically

26. …Mesial Aspect
Cervical line
• Irregular curving occlusally with crest
of curvature above contact area

27. …Mesial Aspect
• Mesial contact area is apical to
marginal ridge
• At junction of middle and occlusal
thirds of the crown
• Concavity above the contact point
extending onto the root

28. …Mesial Aspect
Roots
• Mesiobuccal root is broad and flattened
• Buccal outline of root extends upward and
outward from the crown ending at blunt
apex
• Lingual outline is relatively straight with
blunt apex

29. …Mesial Aspect
…Roots
• Level of bifurcation is little closer to
cervical line than is found buccally
• Lingual root is longer than mesial but
is narrower (banana shaped)
• Lingual root-convex outline lingually
and concave outline buccally

30. Distal Aspect
• Gross outline similar to mesial aspect
• Most of the buccal surface is also
seen (because of tendency of crown
to taper distally)
• Distal marginal ridge dips sharply in
cervical direction

31. Distal Aspect
• Triangular ridges are visible
• Cervical line almost straight
• Distobuccal root is narrower at its
base than either of the others
• DB root-Graceful convex arc from
concavity to the rounded apex

32. Distal Aspect
• Lingual outline of the DB root from
the apex to bifurcation is slightly
concave
• Bifurcation is more apical than either
of the other two areas (5mm from
cervical line)

33. Occlusal Aspect
• Rhomboidal outline
• Measurement of the crown buccolingually
mesial to buccal and lingual grooves is greater
• Crown is wider mesially than distally and wider
lingually than buccally
• Four well developed cusp + small fifth cusp

34. …Occlusal Aspect
• ML cusp>MB cusp>DL cusp>DB cusp>5th cusp
• Acute angles- mesiobuccal and distolingual
• Obtuse angles- Mesiolingual and distobuccal
• Developmentally 3 major cusps
• Maxillary molar primary cusp triangle

35. …Occlusal Aspect
Cental fossa (triangular)
• Two major fossae
Distal fossa (linear)
Mesial triangular fossa
• Two minor fossae
Distal triangular fossa

36. …Occlusal Aspect
• Oblique ridge-crosses occlusal surface obliquely
• On level with marginal ridges
• Central fossa-concave area

37. …Occlusal Aspect
• Cental development pit
• Buccal development groove and central
development groove radiate from central pit
• Transverse groove of the oblique ridge

38. …Occlusal Aspect
• Distal oblique groove traverses the distal fossa
and it connects with lingual developmental
groove
• Fifth cusp groove-any part of dev groove that
outlines 5th cusp
• Distal oblique groove in most cases show
supplemental grooves

39. Endodontic Anatomy
Buccolingual Section (mesial view)
• Usually has 3 roots and 3 canals
• Shows pulp cavities of MB and Palatal
root
• Entire removal of pulp is impossible
because of complexities of root canal
system

40. …Endodontic Anatomy
…Buccolingual Section (mesial view)
• Palatal root canal has largest dimensions
• MB root wide buccolingually and possesses
accessory canal (MB2)
• Pulp horns are prominent
• Pulp chamber is rectangular

41. …Endodontic Anatomy
…Buccolingual Section (mesial view)
• Root canals of mesiobuccal roots are
widest at midroot level
• Palatal root canal and MB root canals
taper gently to the apical region
• Apical foramen appear to exit on the tip
of roots

42. …Endodontic Anatomy
Mesiodistal Section
• MB root has great tendency to possess
a more curved root and canal
• Pulp horns are very distinct
• Pulp chamber is somewhat square
• Canals taper slightly as they approach
the apical foramen

43. …Endodontic Anatomy
Cervical Cross Section
• Outline is rhomboidal in shape with
rounded corners
• Mesiobuccal angle-acute
• Distobuccal angle-obtuse
• If accessory MB2 canal present, it will
be located lingual to the MB canal

44. …Endodontic Anatomy
Midroot cross section
• Palatal and DB root canals are oval
to round
• MB canals are elongated, or round

45. Variations & Anomalies
• Cusp of carabelli sometimes absent
• Partial fusion of buccal roots, or of palatal
and distobuccal roots
• Partial division of palatal or mesiobuccal
root (very rare)

46. …Variations & Anomalies
• Occurrence of enamel pearls
• Extra small root on buccal side
• Concavity on palatal surface of palatal root
next to CEJ.

47. Summary
• Largest maxillary tooth
• Cusp of carabelli on mesiolingual cusp
• Three well developed roots
• Rhomboidal occlusal outline
• Four cusps, characteristic oblique ridge
• Buccal cusps more pointed than palatal cusps
• Crown wider buccolingually

48. Book References
• Dental Anatomy, Physiology and
Occlusion - Wheeler’s
• Dental Anatomy - it’s relevance to
dentistry - Woelfel & Scheid
• Dental Anatomy - S.I. Bhalajhi
• Dental Morphology: an illustrated guide-
Geoffrey C van Beek