Morphology of Molars Flashcards
Universal # of maxillary right perm. molars
1 2 3
Universal # of maxillary left perm. molars
14 15 16
Universal # of mandibular right perm. molars
30 31 32
Universal # of mandibular left perm. molars
17 18 19
Maxillary and mandibular molar widths make up 51% (mandibular) and 44% (maxillary) of the quadrant
___ (mandibular) and ___ (maxillary) of the quadrant
_____ are the only teeth with no tooth in proximal contact with the distal surface
Third molars
Functions of Molars
• Mastication (grinding)
• Maintenance of vertical dimension of face
• Maintenance of arch continuity for proper
alignment
• Support cheeks (esthetics)
Crown Size for All Molars
• Mesiodistal dimension is greater than occlusocervical (wider MD than tall OC)
• Have three to five cusps
• Larger crowns than other teeth but SHORTEST
occlusocervically
• Broader occlusal surfaces than other
teeth
Taper of molars
- Buccal to lingual ( occlusal view )
- Mesial to distal ( occlusal view )
- Mesial to distal ( buccal view )
Taper From Buccal to Lingual For All Molars
Crowns taper narrower from buccal to lingual
(EXCEPT maxillary first molar with large
distolingual cusp)
Taper to the Distal for All Molars
• From occlusal view, molar crowns taper narrower buccolingually from mesial to distal (are narrower buccolingually in distal third than in mesial third)
• All molar crowns taper from mesial to distal (distal cusps are shorter than mesial cusps) M -> D
______ molar is the only molar wider buccal to lingual
maxillary first molar (large DL cusp)
Facial height of
contour for molars is in ______
cervical third (as on all teeth)
Lingual height of
contour for molars is in _______
middle third (as on all posterior teeth)
Mesial contact for molars located
_________
near junction of middle/occlusal thirds
on all molars
Distal contact more
cervical near middle
third (on all molars)
more cervical; near middle
third (on all molars)
Crown Outline to Distinguish Maxillary From
Mandibular Molars:
Maxillary have occlusal ____ dimension greater: ____ shape
Mandibular have occlusal ___ dimension greater: ____ or ____ on firsts
Maxillary greater FL than MD
(wider faciolingually)
Maxillary: more square (rhomboid/parallelogram)
Mandibular greater MD than FL
Mandibular: Rectangular (pentagon on firsts)
Mandibular molars are likely to have #___ large cusps, often a fifth cusp on __1st or 2nd
4 large cusps, often 5th on mandibular 1st molars (distal - think 19/30)
Maxillary molars are likely to have _#___ large cusps, plus a smaller distolingual cusp, and possible fifth cusp called ______
3 large cusps
cusp of Carabelli
For maxillary and mandibular molars, each cusp is formed from how many lobes?
1 lobe (1:1)
Mandibular crowns tilt
______ relative to root
axis
lingually
T/F Maxillary crowns are more
centered over the root
with a lingual tilt
F
Maxillary crowns are more
centered over the root
with NO lingual tilt
T/F From buccal view, the
mandibular crowns tilt
slightly more mesially than
the maxillary
F From buccal view, the mandibular crowns tilt slightly more distally than the maxillary (think 19 & 30 we've been drilling on, APPRECIATE that distal tilt)
_____ have 3 roots
_____ have 2 roots
maxillary molars = 3 roots
mandibular molars = 2 roots
On maxillary molars, which root is the longest?
Which is shortest?
Is MB or DB root wider?
Maxillary
Lingual = longest
Distobuccal = shortest
Mesiobuccal = wider than DB
On mandibular molars, which root is longer? Which is wider?
Mandibular
Mesial = longer and wider
Distal = shorter and narrower
T/F Both mandibular molars are normally wider mesiodistally than occlusocervically (more so on firsts)
True
Which mandibular molar is larger?
Mandibular first larger than second (think 30 vs. 31, 30 has that extra distal cusp)
Mandibular firsts most often have five
cusps, __ buccal and ___ lingual
3 buccal: MB > DB > Distal
2 lingual: mesiolingual longer than distolingual
Mandibular first molar has __ buccal groove(s)
First has two buccal grooves (mesiobuccal, distobuccal)
Mandibular second molar has ____
cusps, __ buccal and ___ lingual, with __ buccal groove(s)
4 cusps: 2 buccal (MB-longer, DB) 2 lingual (ML-longer, DL)
1 buccal groove
T/F All mandibular molars have proximal contact areas located more occlusal on the mesial surface (at junction of _____) than on the distal (near _______)
mesial: jxn middle and occlusal thirds
distal: near middle third
T/F Cervical line/ CEJ of mandibular molars is close to straight mesiodistally (rarely may dip into root bifurcation)
True
Do mandibular first or second molars have more crown taper from the distal contact to the CEJ?
Which contour is straighter? M or D
More crown taper from distal contact to CEJ on FIRSTS than seconds
Mesial contour is more straight than distal
T/F Mandibular first and second molars have two roots: mesial (wider and shorter) and distal
M wider and longer > D
Root trunk shorter on mandibular first
or second?
First has shorter root trunk
On mandibular firsts, the roots are more ___ toward the apex
Divergent - mandibular first
convergent - mandibular second
Crowns taper narrower from buccal to
lingual (more so on firsts) so proximal
surfaces are somewhat visible from the _______
lingual
Mesiolingual and distolingual cusps are
_____ than buccal cusp (mandibular molars)
Mesiolingual and distolingual cusps are longer than buccal cusp
T/F Mesiolingual cusp is wider than distolingual cusp (mandibular molars)
True
T/F On mandibular molars, lingual groove, if onto lingual surface, is likely
to be carious
F
UNLIKELY
T/F Roots narrower on buccal side than lingual side for mandibular molars
F
Roots narrower on lingual side than buccal
Mandibular molars:
Buccal height of contour is in the
____ third
Lingual height of contour is in ____ third
Buccal: cervical third
Lingual: middle third (as on all molars)
T/F Buccal cervical ridge running mesiodistally and more prominent in mesial half (seen occlusally) of mandibular second molar
True
On mandibular molars, are lingual or buccal cusps more pointed and longer (handheld)
lingual cusps are longer and more pointed than buccal
With mandibular molars, you cannot see the occlusal from the mesial view, but from the distal view, you can see more of occlusal surface. This is due to:
taper shorter toward distal
-distal tilt of mandibular molars
CEJ of mandibular molars when comparing proximal views
CEJ slopes occlusally from buccal to lingual (buccal more cervical, lingual more occlusal)
Very slightly curved
Distal marginal ridge is more ___ than
mesial marginal ridge (similar to proximal contacts)
distal more cervical than mesial
Mesial root is broader faciolingually
and longer than distal root, so cannot
see distal root from __ view
mesial view: can’t see distal, M is wider FL
Mesial root of mandibular molar has ___ surface depression, but ___ is deeper.
Smaller distal root has mesial surface
depression but distal surface is _____
mesial, distal is deeper
distal is variable
If mandibular molar is viewed along root axis, more ____ surface is visible than
_____ due to lingual tipping of
the crown relative to the root
facial > lingual
Outline Shape and Taper of Mandibular Second Molars (occlusal)
Mandibular second molar is RECTANGULAR
(MD > BL)
• Tapers narrower from mesial to distal and from buccal to lingual
• Buccal cervical ridge prominent on mesial
Outline Shape and Taper of Mandibular First
Molars (occlusal)
Mandibular first is more prominent in middle of buccal (over distobuccal cusp) and very small distal cusp, making outline more
PENTAGON shaped
• Tapers narrower from
buccal to lingual
• Distal third narrower buccolingually than mesial third
___ triangular ridges form two transverse
ridges on mandibular molars
four
MB + ML = mesial transverse ridge
DB + DL = distal transverse ridge
*Distal cusp triangular ridge is separate
First and second mandibular molars have ____ fossae
3 fossae
– Central (largest)
– Mesial triangular
– Distal triangular (very small)
Mandibular second molar groove pattern is _______, where ___ and ____ grooves join and cross the central groove
Which groove is caries prone?
Mandibular second molar groove pattern is
“+” shaped where BUCCAL and LINGUAL grooves join and cross the central groove
• Buccal groove with buccal pit is caries
prone
Mandibular first molar groove pattern is _______, where ___ and ____ grooves join and cross the central groove
Which groove separates distobuccal and distal cusps?
More “zig-zag” central groove from mesial to
distal fossa
MESIOBUCCAL and LINGUAL grooves join central groove near central fossa
Distobuccal groove
T/F Mesial and distal contact areas normally slightly buccal to the central groove on mandibular molars, so lingual embrasure greater than buccal embrasure
True
Which term refers to possible extra lingual cusp on mandibular molars?
Which term refers to extra cusp on distal marginal ridge of first molar?
tuberculum intermedium
tuberculum sextum
List the following in order from tallest to shortest cusp height/length for mandibular molars:
A. mesiobuccal B. distal C. mesiolingual D. distobuccal E. distolingual
Tallest
- C, E mesiolingual =distolingual (ML slightly taller)
- A mesiobuccal
- D distobuccal
- B distal
Shortest
List the following in order from largest to smallest cusp size/bulk for mandibular molars:
A. mesiobuccal B. distal C. mesiolingual D. distobuccal E. distolingual
Largest
- C mesiolingual
- A mesiobuccal
- E distolingual
- D distobuccal
- B distal
Smallest
T/F For maxillary molars, both cusp length and size can be ordered largest to smallest as:
- Mesiolingual (largest, tallest)
- Mesiobuccal
- Distobuccal
- Distolingual (smallest, shortest)
True
T/F Maxillary first molar is largest maxillary tooth
True
Which maxillary molar is wider mesiodistally?
Maxillary first wider MD
Maxillary molars have __ buccal cusps and ___ lingual cusps
Two buccal cusps:
-mesiobuccal (wider and longer) and
distobuccal
Two lingual cusps:
-mesiolingual (longest of the two) and
distolingual (shortest, can not be seen from buccal view)
On maxillary molars, _____ separates the mesiobuccal and distobuccal cusps, ____ caries prone
buccal groove
is not caries prone
Maxillary molars all have mesial contact at _________ and distal contact _________
mesial: junction of occlusal and middle thirds
distal: near middle third, more cervical
From buccal view, maxillary molar has 3 roots with ____ as the longest, showing behind & between the mesiobuccal and distobuccal roots. ____ is longer and wider than ____, with ____ as the shortest
lingual = longest mesiobuccal = longer and wider than distobuccal
db=shortest
The root trunk of which maxillary molar is shorter?
first maxillary trunk shorter than second maxillary root trunk
Maxillary first have roots more (divergent/convergent), maxillary second have roots more (divergent/convergent)
first: roots more divergent
second: roots more convergent
When viewed from the lingual, little or no proximal surface shows on maxillary first molar due to ____ lingual surface, ____ distolingual cusp. More proximal shows on second with _____ distolingual
cusp.
wider lingual surface
larger distolingual cusp
smaller or missing distolingual cusp = more proximal showing on second
_____ molar has largest and longest mesiolingual cusp (often with cusp of Carabelli or groove 70%) and somewhat smaller distolingual cusp
maxillary first molar has largest and longest ML cusp
Second molar also has longest and largest
_______ cusp compared to much smaller (or missing) ______ cusp
mesiolingual
distolingual
T/F On maxillary molars, lingual grooves and pits are not caries prone
FALSE
on maxillary molars, lingual grooves and pits are prone to caries
Longest lingual root often has ______ on lingual surface (on first molar)
longitudinal depression
Are the distobuccal and mesiobuccal roots closer together on the maxillary first or maxillary second molars?
maxillary second molars
T/F The faciolingual dimension of maxillary molars is greater than the occlusocervical dimension
True FL > OC
T/F From the mesial view, only 3 cusps (but not Carabelli) are visible since distal cusps are shorter on maxillary molars.
FALSE
only 2 cusps (AND cusp of Carabelli) are visible since distal cusps are shorter
From the distal view, you can visibly see ____ cusps on maxillary molars because mesial cusps are ____ than distal
from distal: 4 cusps visible
mesial cusps are LONGER than distal cusps
For maxillary molars, the buccal height of
contour is in the cervical third (like all teeth), and the lingual height of contour is in the middle third (like all posterior teeth), or even ______ if big cusp of
Carabelli
more occlusal if big cusp of Carabelli
From distal view, some of facial and lingual surfaces of maxillary molars may be visible due to crown tapering narrower toward ____
distal
Mesial marginal ridge is ______ than
distal, so more occlusal surface is visible from distal view
mesial marginal ridge MORE OCCLUSAL than distal
Tubercles and marginal ridge grooves are more common on ______ and on ___ marginal ridges than ____
more common on FIRST than second
more common on MESIAL ridges than distal
Which root is known as the banana root?
Lingual root of maxillary molars (esp. 1st)
T/F Only two roots visible from mesial (since
distobuccal is shorter and narrower than
mesiobuccal)
True
T/F Less spread of first molar roots compared to second
False, less spread on second
_____ root has mesial and distal root depression; the _____ root is less likely to have depressions
MB root = mesial and distal depressions
DB root less likely to have depressions
T/F First and second maxillary molars have buccolingual less than mesiodistal dimension
False, first and second maxillary molars are wider BL than MD
Maxillary first molars often have a buccal half narrower mesiodistally than lingual half due to large ______
large distolingual cusp
______ molars are rhomboid or almost square in occlusal outline, with sharp MB and DL angles and other angles more rounded
Maxillary first molars
In ______, there is great variety. Because the distolingual cusp is often quite small, lingual half is narrower mesiodistally than buccal half. Distolingual cusp may be missing, making this molar a tricuspid.
maxillary second molars
Do maxillary first or second molars have a more twisted rhomboid outline due to the prominent mesiobuccal cervical ridge?
Maxillary second molarsz
Maxillary first molar has ___ cusps plus often Carabelli cusp (or depression) on _____ cusp
four
mesiolingual = carabelli or depression
Maxillary second molar has ___
larger cusps, which form the ______, and one smaller or absent
(distolingual)
3 larger cusps MB DB ML (mesiobuccal, distobuccal, and mesiolingual) = Primary Cusp Triangle
Name the 2 distinct components of maxillary molars
Trigon
Talon
Well-developed in 1st molar & undergoes
reduction in size in 2nd & 3rd molars
Bears MB, ML & DB cusps (Tricuspate or
Primary cusp triangle)
Trigon
Bears DL cusp & D MR Located DL to the
Tricuspate
Talon
Cusp of Carabelli Present on __ of Maxillary First Molars; Varies Greatly in Size
70%
RARELY: carabelli found on second maxillary molars
If 4 cusp type maxillary molar, what ridges exist?
Transverse ridge: from mesiolingual to
mesiobuccal cusp
Oblique ridge: from mesiolingual to distobuccal cusp
If maxillary molar has four cusps, it has ___ fossae
4 cusps = 4 fossae
- Central (largest)
- Distal oblique (second largest, cigar shaped)
- Mesial triangular
- Distal triangular (minute)
If three-cusp type maxillary molar: only
three fossae: ____, _____, and ______
mesial, central, and distal
Grooves on Maxillary Molars (Four-cusp Type)
- Central groove: from mesial to central fossa
- Buccal groove: from central fossa
- Distal oblique groove: from distal fossa
- Lingual groove: continues from distal oblique (caries prone)
- Transverse groove of oblique ridge (if present)
Grooves on Maxillary Molars (Three-cusp Type)
If three cusped (heart shaped occlusal outline), grooves are:
– Buccal
– Central
(No distal oblique groove,
no lingual groove, and
no transverse groove of
oblique ridge)
Mesial and distal contacts for maxillary molars are located ____ to buccolingual
center, with _____ more buccal, EXCEPT on the maxillary first molar where the ___ is centrally located
buccal to buccolingual center
mesial more buccal than distal
distal on 1st centrally located
Match the following occlusal outlines to their molar:
- Rhomboid/square
- Pentagon
- Heart
- Rectangle
A. Mandibular first B. Mandibular second C. Maxillary first D. Maxillary second E. Maxillary second, 3 cusp type
- Rhomboid/square = C or D (max 1st or second)
- Pentagon = A (mand first)
- Heart = E (max second 3 cusp; also max third)
- Rectangle = B (mand second)
All Third Molars Traits (diff from 1st and 2nd molars)
- often smaller (crowns and roots) than first or second molars
- maxillary third molars are ONLY maxillary teeth to occlude with only one tooth (recall: mandibular central incisor as well)
- more bulbous, smaller occlusal table
- more wrinkled (accessory grooves/fissures)
- morphology may resemble first, second, or heart shape
- roots OFTEN FUSED, long trunk
- roots thin, pointed; if bent, distally
Size varies greatly but usually ___ molars are the shortest of permanent teeth (short crowns and short roots)
third molars
greatest variance of shape as well
Because third molars are often so distal in location and may not fully erupt, they may be covered with a tissue flap called _____;
trauma and infection of this tissue may cause ______
operculum
trauma/infection can cause pericoronitis
