Mandibular First Premolar

Question 1

For mandibular first premolar, what is the expected age of eruption?

Answer 1

11-12 years

Question 2

For mandibular first premolar, is the occlusocervical crown dimension greater or less than the mesiodistal crown dimension of the buccal face?

Answer 2

The occlusocervical dimension is greater. Thus the occlusal surface of the mandibular 1st premolar is taller than it is wide.

Question 3

For mandibular first premolar, from the facial/lingual view, what is the outline form of the crown?

Answer 3

Trapezoidal (Occlusal surface being wider than the cervical end) OR pentagonal (mesial and distal cusp ridges form the pointed top of pentagon on the buccal side)

Question 4

For mandibular first premolar, which cusp ridge, mesial or distal, is longer? What features are commonly found on both cusp ridges?

Answer 4

The distal cusp ridge is longer. Both ridges commonly have occlusal notches (small concavities on the buccal cusp ridges)

Question 5

For mandibular first premolar, what are the mesial and distal outline shapes as seen from the facial/lingual view?

Answer 5

Mesial outline: Convex, not as pronounced as distal outline. Remember, mesial cusp ridge NOT as long as distal cusp ridge
Distal outline: Convex. Long distal cusp ridge.

Question 6

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

Answer 6

Mesial: Middle 1/3, just below the Occlusal-middle junction.
Distal: Middle 1/3, even with or just below the mesial contact point.

Question 7

For mandibular first premolar, how are the mesial-distal contact points centered buccolingually?

Answer 7

Mesial: Just on the buccal side of the buccal-lingual center line.
Distal: Either just buccal of the buccal-lingual center line or on the center line. Lingual to the mesial contact.

Question 8

For mandibular first premolar, how many roots are present? Shape? Root apex curvature?

Answer 8

1 mandibular 1st premolar root. Has a conical shape. The root apex often curves distally.

Question 9

For mandibular first premolar, how many pulpal canals are present? What is the pulp chamber shape in cross section?

Answer 9

1, oval shaped pulpal canal

Question 10

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

Answer 10

Diamond

Question 11

For mandibular first premolar, what are the facial and lingual outlines as seen from the occlusal view?

Answer 11

Facial outline is convex with a prominent middle lobe

Lingual outline is convex. There is a slight concavity on the mesial half = mesiolingual developmental groove.

Question 12

For mandibular first premolar, what is the small concavity found on the mesial side of the lingual cusp?

Answer 12

mesiolingual developmental groove.

Question 13

For mandibular first premolar, thick triangular rideges form the transverse ridge. Does the deep central groove cross the transverse ridge?

Answer 13

No.

Question 14

For mandibular first premolar, what shape is the occlusal table? What makes up the outline?

Answer 14

Triangle. The M & D cusp ridges make the base and the M & D make up the sides. The lingual cusp is the point opposite the base in the triangle.

Question 15

For mandibular first premolar, what is the crown shape from the proximal view?

Answer 15

Rhomboid because it slopes to the lingual.

Question 16

For mandibular first premolar, describe the buccal and lingual outlines as seen from the proximal view.

Answer 16

Facial outline: Convex, crown tilts lingually. Blunted cusp.

Lingual outline: Convex. Small lingual cusp. Less than half the height of the buccal cusp.

Question 17

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

Answer 17

Buccal: Cervical 1/3
Lingual: Middle 1/3 of the crown. Occlusal 1/3 of the lingual cusp.

Question 18

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

Answer 18

NO. The crown slopes lingually (rhomboidal shape) and the buccal cusp is over the root center. Crown is on lingual side.

Question 19

For mandibular first premolar, at what angle does the buccal triangular ridge slope?

Answer 19

45 degrees

Question 20

For mandibular first premolar, how many developmental lobes?

Answer 20

4.

Question 21

For mandibular first premolar, what is unique, among premolars, about the cervical-occlusal height relationship between the mesial and distal marginal ridges?

Answer 21

In the mandibular first premolar the distal marginal ridge is higher (more occlusal OR less cervical) than the mesial marginal ridge. In ALL other premolars the mesial marginal ridge is more occlusal than the distal marginal ridge.