MAXILLARY MOLARS.pdf about the occlusal aspect of molar

Learning about molar

2. •There are 12 permanentmolars
•First, second and third on each side, both on the upper and lowerarch
•Under universal numbering system they are
1,2,3,14,15,16,17,18,19,30,31,32
•They are the largestand strongestteeth in the arch

3. Maxillarymolarsassistthemandibularmolarsinperformingthe
majorportionoftheworkinthemastication.
Maxillarymolarshavelargecrownswithfourwell-formedcusps
Theyhave3roots,2buccaland1lingual
Thelingualrootislargest
Normallocation–atthecenterofthefullydevelopedadultjaw
anteroposteriorlyasaconsequenceofthesignificanceoftheir
positionsandcircumstancessurroundingtheirerruption–mayalso
beconsideredasCORNERSTONESofthedentalarches

4. •Frequently, one or more of the third molars are congenitallymissing
•This occurs in nearly 20% of thepopulation
•The combined mesiodistalwidth of the three mandibularmolars on one
side make up 51% of the mesiodistaldimension of their quadrant
•The maxillary molars constitute 44% of their quadrants mesiodistal
dimension

5. •Play a major role in the mastication of food (chewing andgrinding)
•Loss of first molar can result in loss of more than 80mm of chewing
surface
•Important in maintaining vertical dimension of theface
•Maintaining continuity withindental arches, thus keeping other teeth in
alignment
•Function in estheticsby keeping the cheeks full and keeping chin
proper distance from thenose

6. First evidence of calcification : at birth
Crown completion : 3-4 years
Erruption: 6-7 years
Root completion : 9-10 years

7. The crown is roughly trapezoidal, and the cervical
line shows little convexity, which is directed
towards theroot.
The mesialoutline -straightcurving occlusallyas it
reaches the contact area which is at the junction of
the occlusaland middlethirds.
The distal outline -convex, distal surface-speroidal
the crest of curvature is at thecentre of the middle
third
MBDB
L/P
M
D

8. The mesiobuccalcusp is broader than the distobuccal
cusp, and its mesialand distal slopes meet at an obtuse
angle, while the mesialand distal slopes of the
distobuccalcusp meet at sharper rightangle.
Distobuccalcusp is therefore sharper.
We may see the lingualcusps.
The buccaldevelopmental groove divides the 2 buccal
cusps in equal distance and it terminatesapically.
The 3 roots are visible and inclined distally.
The lingual root is the longest, and the mesiobuccal
and distobuccalroots are equal in length.
MBDB

9. Buccaldevelopmental groove(BDG) slants occlusoapicallyin a line of
direction parallel to long axis of distobuccalroot.
Terminates –at point half the distancefrom its origin occlusallyto
cervical line.
Lateral to buccaldevelopmental groove (BDG) terminus –dip in the
enamel is seen iedevelopmental in character and extends for some
distance mesially& distally
Groove –not deep, it becomes shallow towards its termination,
gradually fading out.
Pit is sometimes present at the end ofthe groove that can be the site of
caries
BDG

10. MB, DB, andPalatal
roots
Roots are nearlytwice
as long as thecrown
Relative length:
Palatal>MB>DB
Roots converge into a broad cervical
rootbase called the RootTrunk
Furcationusually located at the
junction of the cervical and middle
thirds of theroots
DB
MB
P
Point of bifurcation of
two buccalroots-4mm
above the cervical line

11. •TheMBandDBrootsoftencurvedistally
•TheapicalthirdoftheMBrootmaycurvedistallyenoughto
putitsapexdistaltothebuccalgroove

12. Only lingual cusps can beseen.
The mesiolingualcusp is the largest cusp, and accounts to 3/5 of the
mesiodistalcrown diameter, the distolingualcusp accounts to2/5.
The angle formed by mesialoutline of the crown and the mesialslope of
ML cusp –90 degree
DL cusp -spheroidaland smooth
Due to the prominent DL cusp, crown may be as wide or wider on the
lingual for the first molar
The lingual developmental groove starts approx. inthe centerof lingual
surface mesiodistally, and curves sharply distally, then continues on the
occlusalsurface.
DL
Lingual
root

13. The fifth cusp attached to the mesiolingualsurface of the
mesiolingualcusp.
The fifth cusp (cusp of Carabelli)is 1.5 mm cervical to the
mesioling. cusp tip.
An irregular dev. groove separates the cusp from the
mesiolingualcusp.
If the fifth cusp is well developed, cusp angle will be sharper
and less obtuse than that of the mesiolingualcusp
There are 3 roots visible, the lingual root makes most of the
aspect.
Cusp of Carabelli

14. •Onfirstmolarsthepalatalrootisthethirdlongestofany
maxillarytooth(aftercanineandsecondpremolar)
•Tapersapicallytoabluntorroundedapex
•Thereisusuallyadepressiononthelingualaspectofthe
palatalroot

15. The buccaloutline has a crest of curvature within the cervical third,
then it continues with a convex outline until the tip of thecusp.
The lingual outline has a crest of curvature within the middle third,
and it shows a convex pattern until it reaches cusp of Carabelli
which shows anotherconvexity.
The mesialmarginal ridge, confluent with the MB &ML cusp ridges
is irregular & is located at a level 1/5 of the height of crown from
the tip of thecusps.
The cervical line curves occlusallyabout1mm.
If 5
th
cusp –well developed, lingual outline dips inward to reveal it
ML cusp-is on a line with the long axis of lingual root.
MB
ML
B
L/P

16. The intercuspaldistance of the 2 mesial cusps is a little
more than half the buccolingualdimension of the
crown. (Mesial cusp dist> ½ BL)
Mesialcontactarea-apicaltomarginalridge,approx.
JunctionofMIDDLE&OCCLUSALthird
Themesialcontactareaisbuccaltothebuccolingual
centerofthecrown.
The lingual and the mesiobuccalrootsare seen
MB root -widerbuccolingually.

17. Level of bifurcation –little closer to the cervical line than is
found between the roots buccally.
Lingual/palatal root-longer than the mesialroot but looks
narrower from this aspect
Lingual /Palatal root –banana shaped. Convex outline-
lingual, Concavity-buccal.
Roots-apex is roundened, palatal root appears more pointed
toward the end than MB root.
P
MB
MB
ML

18. The general outline is similar to that of the mesialaspect,
but the buccolingualmeasurement is more mesiallythan
distally due to the tilt of the buccalside of thecrown.
Thedistalmarginalridgeislocatedmorecervicallyso
thatwecanseepartoftheocclusalsurface.
Thecervicalline’scurvatureiszero.
Allthe3rootsarevisible.
Thedistobuccalrootisthesmallestone.
P
DB
DL DB

19. Crown -centeredoverroots
The occlusal outline is rhomboidal, with the mesial and
lingual measurements being greater than distal and buccal
measurements
Four well developed cusps, mesiolingual(the largest), then
mesiobuccal, then distolingual, then distobuccal, then fifth
(Carabelli’s)cusp.
ML cusp: Largest and longest; connects to DB cusp by the
ObliqueRidge ML>MB>DB>DL
DB MB
MLDL

20. Developmentally-3 cusps can be considered as PRIMARY, ML & 2
Bcusps
DL Cusp is common to all the maxillary molars
Any other additional one –5
th
cusp –SECONDARY
DL cusp –progressively smaller from first molar to third molar, often
disappearing as a major cusp.
TRIANGULAR arrangement of cusps is reflected in root trunk when
the tooth is sectioned
Thus triangular arrangement of molar cusp ----MAXILLARY MOLAR
PRIMARY CUSP TRIANGLE

21. Themesiobuccal,anddistolinguallineanglesare
acute
Mesiolingual,anddistobuccallineanglesare
obtuse
Thereisanobliqueridgemadefromtheunionofthe
∆ridgeofthedistobuccalcuspandthedistalridge
ofthemesiolingualcusp.
Itcrossestheocclussalsurfaceobliquely.

22. There are 4 fossae
Majorfossae
(i)Central fossais roughly triangular in shape,mesialto oblique
ridge.
(ii)Distal fossais linear, distal to obliqueridge.
Minorfossae
(i)Mesial∆ fossa. It is distal to mesialmarginalridge.
(ii)Distal ∆ fossa. It is mesialto distal marginalridge.

23. There are 6 developmental grooves
1. Central developmental groove-From central pit to mesial ∆
fossa.
2. Buccal developmental groove-From central pit buccally
between the mesiobuccaland distobuccalcusps.
3. Distal oblique groove -From distal ∆ fossa going obliquely.

24. 4. Lingual developmental groove-joins distal oblique
groove, goes between mesiolingualand distolingual
cusps and travels cervically.
5. Transverse groove of the oblique ridge -It crosses the
obliqueridge.
6. Fifth cusp groove-Between the fifth cusp and the
mesiolingualcusp.

26. There are 3pits
1. Central pit is located in the deepest part of the central fossa. It is
a result of the junction of central and buccaldevelopmental
grooves.
2. Mesialpit is located in the deepest part of themesial∆fossa.
3. Distal pit is located in the deepest part of the distal ∆ fossa.

28. Maxillary second molar supplements the first molar in function
Roots -as long as maxillary first molar (less divergent, and may be joined
together)
Both distal cusps are less developed. (Distobuccal cusp is not as large or
as well developed, Distolingualcusp is smaller)
No 5
th
cusp is evident
DB
DP

29. •The crown is smaller in overall dimensionsthan themaxillary first
molar.
•Crown-maxillary second molar is 0.5mm shorter cervico-occlusallythan
that of first molar.
•Buccolinguallyis about the same.

30. •ProximalContacts
Same as for allmolars:
–Mesial:Junction of occlusal and middlethirds
–Distal: Middlethird
–The crown appears totilt distally at thecervix
–This, coupled with a short distobuccalcusp makes the crown appear
shorter on the distal than themesial
DM

31. •The crown is shortercervico-occlusallyand narrower
mesiodistally.
•The distobuccal cusp issmaller, part of DMR and some part of the
distal surface isseen.
•Buccalroots are about same length.
•Roots are nearly parallel & inclined distally. End of the DB root is
slightly distal to the distal extremity of the crown
•Tip of MB root-line with buccalgroove of the crown instead of tip
of MB cusp, as was found on the first molar
MBDB
D M

32. PALATALASPECT
•Thedistolingualcusp-smaller.
•Partofthedistobuccalcuspisseendistaltothe
distolingualcusp.
•Noevidenceofpresenceofthefifthcusp.
•Apexofthelingualrootisinlinewiththedistolingual
cusptipinsteadofthelingualgroove
DM
ML DL
DB

33. Mesial aspect
•Buccolingualdimension –same as first molar, but the
crown length is less.
•The divergence of the roots is less than that of the
max. firstmolar.
•Roots-do not spread as far BL ( within the confines
of BL outline)
MB
ML
BL

34. Distalaspect
•Because the distobuccal cusp is smaller than the
mesiobuccal cusp more ofthe mesiobuccal cusp isseen
from this angle.
•Apex of lingual root-in line with distolingualcusp
DBDL
BL

35. 1Rhomboidal shape of occlusal aspect is more visible (acute
angles are less and obtuse angles are more).
2Buccolingualdiameteristhesameasfirstmolar,but
mesiodistaldiameteris1mmless.
3Thedistalcuspsaresmallerandlessdeveloped.
4Nofifthcusp.
5Itisnotuncommontofindmoresupplementarygrooves,
accidentalgroovesandpitsthanmaxillary1
st
molar
OcclusalAspect

36. 2
3 4
•Generally there are fourcusps
•First molar possess a fifth cusp 70% of the
time
•Second molar may be missing the DLcusp
•The oblique ridge connects
the DB cusp with the ML
cusp
•It is present in second molars,
butsmaller than the oblique
ridge of firstmolars
Three-CuspMolars
•The distal fossaeand both the distal oblique
and lingual grooves areabsent
1 2
3
4
5
1

37. Maxillary first molar Maxillary second molar
Buccalroot spread out behind lingual rootBuccalroot less spread out
Some rootflare behind crown Less root flare
Lingual cuspsnearly the same width Distolingualis narrower than mesiolingual,
absent
Cusp of carabellipresent on ML cusp Cusp of carabelliabsent
Crown often wideron lingual half Crown –narrower on lingual half
Crown -larger Crown-smaller
More prominent obliqueridge Smaller oblique ridge
prominent mesiobuccalcervical ridge Lessprominent mesiobuccalcervical ridge

38. Supplements-second molar in function
Roots and crown shorter than first or second molar
Crown often possess more supplemental grooves
DL cusp-very small & poorly developed
Triangular occlusaloutline.

39. Roots are shorter, convergent, often fused, and
usually are 3 innumbers.
smallest maxillarymolar.
The mesiolingualcusp is the largest.
MD

40. CI and MD –shorter than second molar
Roots -usually fused, functioning as one large
root
Fused root end in a taper at the apex
Roots -slant to the distal

41. One large lingual cusp is seen
No lingual groove is evident

42. Taper to the fused roots and a bifurcation ,
usually in the region of the apical third
Root portion is considerably shorter in relation
to the crown length
Both the crown & roots –poorly developed,
with irregular outlines

43. Most of the buccalsurface of the crown is in view
More of the occlusalsurface may be seen than can be
seen on 2
nd
molar
measurement from CL to MR is short

44. Heart shaped outline
Lingual cusp –large and well developed
Little or no DL cusp is evident –semicircular
shape from one contact area to other
3 cusps-2 buccal, 1 lingual
Supplemental grooves

45. It may have manyvariations occlusally:
a)Heart shape type with three cusps.
b)Rhomboidal shape type with four cusps
-Strong oblique ridge, central fossa, distal fossa& lingual developmental
groove-as seen on second molar
c) Crown –converges more lingually
d) One cusp type (pegshaped).
e) Congenitallymissing.