Mandibular Premolars Flashcards
Which premolars show lingual convergence and which show divergence?
1st premolar and the 2-cusp 2nd show divergence while the 3-cusp 2nd show convergence.
What is the rule of 4?
At 7 months of age the first teeth erupt, at 11 months - 4 teeth present. Then 4 teeth present every 4 months. All 20 teeth are typically present by 24-36 months.
Describe the root from the lingual view of the 1st mandibular premolar.
Root is more narrow on the lingual. Mesial and Distal developmental depressions are visible.
Describe the 1st mandibular premolars’ cusp tips from the proximal view.
Facial cusp tip is centered over root. Lingual cusp tip is in line with lingual root outline.
Which premolars are always bigger than the other?
2nd premolars
Describe the differences in the cusp tips of the 2nd premolar.
Mesiolingual cusp tip is about 1.5 mm shorter than facial cusp. Distolingual cusp tip is about 2.0 mm shorter than facial cusp. Mesiolingual cusp is wider than distolingual cusp.
Describe the mesiolingual groove of 1st mandibular premolar.
Mesiolingual groove extends from the mesial fossa of the occlusal surface onto the mesiolingual surface of the crown
Describe the 1st mandibular premolar from the buccal view.
Relatively symmetrical bilaterally, pointed cusp, mesial cusp ridge shorter than distal, slight vertical depressions, and a ridge extending from the cervical third to the cups tip is call the buccal ridge
Describe the 1st mandibular premolar from the lingual view.
Occlusal table slants cervically, lingual cusp is similar to a cingulum because so small, and the Lingual cusp has a pointed and centered tip and is much shorter than the facial cusp.
How does the 2nd premolar compare to the 1st from the buccal view?
Shorter Buccal Cusp. Cusp ridges show less angulation. Mesial cusp ridge is shorter than distal cusp ridge. Distal cusp notch more common.
Describe the 1st mandibular premolars’ central groove and fossa.
Central groove is lingually positioned, due to the long triangular ridge of the buccal cusp. Comma shaped distal fossa.
Describe the 1st mandibular premolars’ height of contours from proximal view.
Facial height of contour is in cervical 1/3. Lingual height of contour is in middle 1/3
Describe the 1st mandibular premolars’ marginal ridges.
Mesial Marginal Ridge is at 45 degrees. Distal Marginal Ridge is nearly horizontal and is more coronally positioned.
Describe the 1st mandibular premolar from the occlusal view.
Diamond shaped occlusal outline. Triangular shaped occlusal table. Long facial triangular ridge. Short lingual triangular ridge. Triangular ridges form transverse ridge which separates M and D pits.
Compare the premolars from the lingual view.
Two lingual cusps (3 total cusps which developed from 5 lobes) or 1 lingual cusp (2 total cusps which developed from 4 lobes) may be present. 3-cusp variety has a lingual groove between the 2 lingual cusps.
