Max First Molar.ppt

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 calcificationat 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 90
o
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 5
th
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 90
o
•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 5
th
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 3
rd
)
•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 5
th
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 mesialaspect
•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>5
th
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 5
th
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