Mandibular Second Premolar

Question 1

For the mandibular second premolar, what is the expected age at eruption?

Answer 1

11-12 years

Question 2

For the mandibular second premolar, what are the tooth numbers in the universal numbering system?

Answer 2

20 & 29

Question 3

For the mandibular second premolar, what is the crown shape as seen from the facial or lingual view?

Answer 3

Trapezoid (M-D length longer at occlusal 1/3 than cervical 1/3) or pentagon (reflects the central facial cusp and M,D ridges).

Question 4

For the mandibular second premolar, is the O-C crown dimension longer or shorter than the M-D crown dimension?

Answer 4

Longer. The facial surface is taller than it is wide in the M-D direction.

Question 5

For the mandibular second premolar, describe the mesial and distal outlines as seen from the facial and lingual views.

Answer 5

Mesial outline: convex. The mesial cusp ridge is shorter than distal cusp ridge. Notches are often seen in mesial cusp ridge.
Distal outline: Convex. Distal cusp ridge longer. Notches common.

Question 6

For the mandibular second premolar, what are the heights of contour (occlusogingival contact points) of the mesial and distal faces?

Answer 6

Mesial: Middle 1/3 just below occlusal-middle junction
Distal: Middle 1/3; cervical to mesial height of contour.

Question 7

For the mandibular second premolar, how many developmental lobes are there? How many cusps are present on the occlusal surface?

Answer 7

Usually 5! Sometimes four. First time we have seen this. Usually 3 cusps (if 5 developmental lobes)

Question 8

For the mandibular second premolar, if, as usual, the occlusal surface has 3 cusps, which has a wider M-D dimension, the lingual or buccal ridge of tooth?

Answer 8

The lingual if 3 cusp. Buccal if two cusps.

Question 9

For the mandibular second premolar, are the mesial and distal marginal ridges parallel?

Answer 9

Yes.

Question 10

For the mandibular second premolar, what is the crown shape as seen from the occlusal view?

Answer 10

Depends on # of cusps:
3 cusps=square
2 cusps=round or oval (same as max 2nd premolar)

Question 11

For the mandibular second premolar, describe the facial and lingual outlines as seen from the occlusal view.

Answer 11

Facial outline: Convex; prominent middle lobe

Lingual outline: mostly convex; more square shaped than buccal side in 3 cusp tooth.

Question 12

For the mandibular second premolar, is there a transverse ridge present on the occlusal surface?

Answer 12

NOT when the tooth has 3 cusps. Three triangular ridges don’t meet to form a transverse ridge.

Question 13

For the mandibular second premolar, when 3 cusps are present how many fossa are present? what are they called? Which is largest?

Answer 13

3. The Mesial, distal, and central fossa. Central fossa is largest.

Question 14

For the mandibular second premolar, what are the buccolingual contact locations?

Answer 14

Mesial: Buccal to B-L center
Distal: Just slightly buccal to B-L center or at B-L center. Distal buccolingual contact location is more lingual than the mesial contact location.

Question 15

For the mandibular second premolar, of the two lingual cusps, which is larger?

Answer 15

The mesial cusp is larger and extends higher occlusally.

Question 16

For the mandibular second premolar, what groove separates the two lingual cusps?

Answer 16

The lingual groove

Question 17

For the mandibular second premolar, what are the names of the 3 developmental grooves present on the 3 cusp occlusal surface? Which way do they travel?

Answer 17

Mesial developmental groove travels MB from central fossa
Distal developmental groove travels DB from the central fossa
Lingual developmental groove travels in a lingual direction from the central fossa.

Question 18

For the mandibular second premolar, what is the developmental groove on the two cusp occlusal surface?

Answer 18

Central developmental groove. Connects the mesial and distal fossa crossing the transverse ridge to get there.

Question 19

For the mandibular second premolar, what is the crown shape as seen from the mesial view?

Answer 19

Rhomboidal.

Question 20

For the mandibular second premolar, is the occlusal table centered over the root trunk?

Answer 20

NO due to its lingual tilt leading to it’s classification as a rhombus.

Question 21

For the mandibular second premolar, how do the O-C crown dimensions and the B-L crown dimensions compare?

Answer 21

They are almost the same with the O-C being just slightly longer. Shorter and wider crown than mandibular 1st premolar.

Question 22

For the mandibular second premolar, describe the facial and lingual outlines as seen from the mesial view.

Answer 22

Facial outline: Convex; height of contour in cervical 1/3. Slants to the lingual. Blunted cusp.
Lingual outline: Convex; height of contour in middle 1/3 of crown and occlusal 1/3 of crown. Lingual cusp is shorter than buccal cusp but larger than lingual cusp on man 1st premolar.

Question 23

For the mandibular second premolar, what are the heights of contour for the buccal and lingual surfaces as seen from the proximal view?

Answer 23

Buccal: Cervical 1/3
Lingual: Middle 1/3 of crown; occlusal 1/3 of lingual cusp.

Question 24

For the mandibular second premolar, number of roots? Shape? Dilaceration?

Answer 24

1 conical shaped mandibular secondary premolar root that dilacerates to the distal

Question 25

For the mandibular second premolar, number of pulpal canals? shape in cross section of pulpal chamber?

Answer 25

1, oval