Maxillary Molars Comparison

Question 1

Mesiodistal Crown Width

Answer 1

First molar crowns are wider mesiodistally than second molars and second molars are wider than third molars

Question 2

Occlusocervical Crown height

Answer 2

The occlusocervical crown height of first molars is greater than second molars and second molars are greater than third molars

Question 3

Third molar form variation

Answer 3

• Third molars are less well-developed than the other maxillary molars
• Third molars vary from their “normal” form more often than other teeth
• The maxillary third molars frequently exhibits an extra small crown size (microdontia).

Question 4

Crown-root orientation

Answer 4

• On second molars, the disital aspect is shorter than the mesial when viewed from the buccal
• This creates a distal tipping on the root trunk with the occlusal surface slanting cervically from mesial to distal
• The distal tipping of posterior teeth is probably most apparent on maxillary second molars when viewed from the buccal.

Question 5

Cusp sizes

Answer 5

• The two buccal cusps are closer in size on first molars than second molars since the distobuccal cusp is much smaller relative to the mesiobuccal cusp on second molars
• When comparing cusp heights, it has also been stated that the buccal cusps are of equal height on first molars, the distobuccal cusp is slightly shorter than the mesiobuccal cusp on second molars, and on third molars the distobuccal cusp is much shorter than the mesiobuccal cusp.

Question 6

Buccal developmental grooves

Answer 6

• The buccal developmental groove is located farther distally on the crown surface of second molars than first molars, producing a relatively larger mesiobuccal cusp on second molars.
• The buccal groove is shorter on second molars than on first moars.
• According to the Tooth Atlas, there is NO pit at the termination of the buccal groove on second molars wherease first molars may have a pit.

Question 7

Root length

Answer 7

• The roots of first and second molars are about the same length, whereas the third molar is the shortest of the three

Question 8

Root form

Answer 8

• From a buccal view, the roots of maxillary first molars resemble the handles of a pair of pliers but this form is NOT present on second molars

Question 9

Root separation

Answer 9

• The roots have their greatest mesiodistal separation on first molars, less on second molars, and have the least separation (even fusion) on third molars.
• Partial or total fusion is common on second molars as well

Question 10

Root Alignment

Answer 10

• The mesial and distal roots are more parallel to each other on second molars than first molars.

Question 11

Root Inclination

Answer 11

• The distal inclination of the roots is greatest on third molars, less on second molars, and the least inclination occurs on first molars

Question 12

Root trunk

Answer 12

• The buccal furcation is located farther apically on the second molar than on the first molar.
• The cervico-apical dimension (height) of the root trunk is greatest on third molars, less on second molars, shortest on first molars.

Question 13

Cusps of Carabelli

Answer 13

• The Cusp of Carabelli is fairly common on first molars but somewhat rare on second molars; “Less common” would be better description.

Question 14

Distolingual cusp

Answer 14

• The distolingual cusp of the second molar is much shorter than the mesiolingual cusp

Question 15

Distolingual groove

Answer 15

• The distolingual developmental groove does NOT extend as far mesially or as far cervically on the lingual surface of second molars as it does on first molars

Question 16

Palatal (Lingual) Root width

Answer 16

• From a lingual view, the palatal root of first molars is wide mesiodistally; it is narrower on second molars, narrowest on third molars.
• The apex of the palatal root is aligned with the distolingual cusp tip on second molars whereas it is aligned with the lingual groove on first molars.

Question 17

Buccolingual crown width

Answer 17

• From an occlusal view, maxillary molar crowns are about the same width buccolingually, with first molars being slightly wider than seconds and third molars being narrower.

Question 18

Crown Outline

Answer 18

• The occlusal outline of first molars is square to rhomboidal. The Rhomboidal outline is more accentuated on second molars.
• The predominant occlusal outline form of third molars is “heart-shaped”.

Question 19

Third molar crown form

Answer 19

• Third molar crowns are more rounded and bulbous than first and second molars.

Question 20

Lingual crown convergence

Answer 20

• Second molars are narrower mesiodistally in the lingual half of the crown than first molars, producing a lingual crown taper
• There is even greater lingual convergence in third molar crowns
• First molars frequently have reverse taper (or reverse convergence) being wider on the lingual than on the buccal

Question 21

Distal crown convergence of second molars

Answer 21

• There is more distal crown taper on second molars than first molars.

Question 22

Distolingual cusp size

Answer 22

• The distolingual cusp is smaller on second molars than on first molars
• The distolingual cusp is usually very small or missing on third molars
• About three-quarters of the third molars have 3 cusps, although we see odd variations from one cusp (looking like a tiny canine) to as many as eight cusps
• When the third molar has 4 cusps the distolingual cusp could be very small or it could be normal-size and look like a smaller version of the second molar

Question 23

Mesiobuccal Angle

Answer 23

• When viewing second molars occlusally, the angle between the buccal and mesial surfaces (mesiobuccal angle) is more acute than it is on first molars.

Question 24

Mesiolingual and Distobuccal angles

Answer 24

• From an occlusal view, the obtuse angles found in the outline of the crown (distobuccal and mesiolingual) are more obtuse on second molars than on first molars

Question 25

Marginal Ridge Tubercles

Answer 25

* There are fewer marginal ridge tubercles on the mesial marginal ridge of second molars than first molars; tubercles are absent from third molars.

Question 26

Third molar occlusal surface area

Answer 26

* Third molars have the *smallest* occlusal surface area (smallest occlusal table)

Question 27

Cusp sizes

Answer 27

* On second molars, the two mesial cusps are about the same size as the mesial cusps on the first molars but the distal cusps are smaller and not as well-developed

Question 28

Oblique Ridge

Answer 28

* The oblique ridge is smaller on second molars than first molars * The oblique ridge is rarely crossed by a groove in the first molar but is frequently crossed by a groove in the second molar * The oblique ridge is barely visible or absent on third molars

Question 29

Pit-groove pattern/number

Answer 29

* The pit and groove pattern on the occlusal surface is more variable and there are more supplemental grooves on the occlusal surface of second molars than first molars. * The pit and groove pattern on third molars frequently creates a wrinkled occlusal surface similar to the maxillary 2nd premoar.