Mandibular Second premolar Flashcards
First Calcification
2.25-2.5 years
Enamel Completion
6-7 years
eruption
11-12 years
root completion
13-14 years
Measurements
The Facial Lingual width is greater than the Mesial Distal Width
Root Length
Longer than the crown
How many cusps are present?
2 or 3!
Is the mandibular 2nd premolar larger than the first?
YES
Is the mandibular 2nd premolar larger than the first?
YES
Cusps
2 *buccal and lingual
3 *buccal, mesiolingual, and distolingual
Typically the more common form is 3 cusps!
Buccal Aspect
Buccal cusp is shorter than the first mandibular pre molar, buccal contact areas appear higher than the 1st because of the short cusp, but remain in the MIDDLE 3rd.
Is the root broader mesiodistally than the 1st?
YES and ends in apex that is more blunt
Buccal Cusp Ridge
More common in occlusal third of the first, less common than maxillary premolars
Buccal Cusp Ridge comparison of 1st and 2nd premolars
1st is deeper on the mesial of buccal surface, while the 2nd is deeper on the buccal surface
Root Comparison
Root tapers gradually and may either bend to mesial or distal, but the 2nd is more blunt, thicker, and longer
What shape is the facial aspect?
Pentagon
Notches on the cusp ridges
Most common on Mesial Cusp Ridge of the 1st and Distal Cusp Ridge of the Second
How is the cervical line on the second?
It is more flat!
Proximal heights of contour
All at the junction of the occlusal and middle thirds!
1st Premolar vs 2nd Premolar Cusp tip
1st premolar have a more pointed cusp tip with longer cusp ridges
2nd has more flat cusp ridges than first
Lingual Aspect
Remember- may vary with either one lingual cusp or two!
Are the lingual cusp(s) longer than the first?
YES
3 cusp variety
Mesiolingual and Distolingual Cusps, Mesiolingual Cusp is large and longer.
A small lingual groove is what separates the two cusps in the lingual aspect
2 cusp variety
Single lingual cusp- equal in height of the 3 cusp variety.
No lingual groove but has a developmental depression distolongually
On the 2 cusp variety, where is the lingual cusp tip located in regards to a bisecting line?
Mesial to or On
Lingual Surface
Smooth of booth varieties and spheroid.
Has a bulbous form thinning towards the cervix.
Root is wide lingually but narrower than on buccal
Lingual Taper
1st and 2nd cusp, 2nd tapers lingually
3 cusps 2nd will be as wide or wider on lingual
Lingual Cusp Size and Shape
1st Premolar
-transition from anterior to posterior- from cingulum to cusp!
-may have no lingual cusp or up to 4 cusplets
-most of the occlusal surface is viewable
Lingual Cusp Size and Shape
2nd Premolar
-2 cusp: 2nd cusp is mesial to or on a bisecting line
3 cusp: 2nd lingual groove passes through the mesiolingual and distolingual cusps
3 Cusp: 2nd mesiolingual cusp is larger and longer than the distolingual cusp!
Marginal Ridges *
1st: Only adult tooth with the Mesial Marginal Ridge is more cervically located than distomarginal ridge
2nd: Distal Marginal Ridge is more cervically located!
Mesial Aspect
Crown and Root wider than the 1st!
Mesial Aspect
Crown and Root wider than the 1st!
Is the buccal cusp centered over the root?
Not nearly as centered as compared to the first and it is shorter than the first.
Is the lingual lobe development greater than 1st?
YES
Is the lingual lobe development greater than 1st?
Right angle
Why is the occlusal view not as visible on the 2nd from the mesial aspect?
Because the MMR is up higher towards occlusal, DMR is up higher towards the cervical
Is there a mesiolingual developmental groove?
No
Is the root longer than the 1st
Yes but more blunt
Distal Aspect
- Note that more of the occlusal surface is visible because DMR is more cervical
The crowns of all posterior teeth are tipped distally on the long axis of the tooth!
Where do all the mandibular posterior teeth tilt?
Towards the lingual
What shape is the proximal aspect?
Rhomboid Shape
Which tilts more lingually, the man 1st pre molar or man 2nd pre molar?
Mandibular 1st PreMolar
In the 3 cusp variety, how many cusps do you see from the mesial?
You see two cusps, but from the distal you see 3!
Why?
-Cause Mesiolingual cusp is larger and longer- so from mesial aspect you’ll see the buccal cusp and the mesiolingual cusp
Buccal
1st is in the cervical third
2nd is at the junction of the middle and cervical third
Lingual
Both are middle 1/3
cervical lines
1st Premolar- cervical line on mesial surface is regular, the crest of curvature is centered buccolingually, and the line maybe straight across buccoingually.
2nd premolar- similar to 1st but less curvature
Root
1st is usually straight on the buccal and lingual sides, until mid root it tapers to a blunt end
1st may be bifurcated!
Occlusal Surface of Both Varieties of Cusps on the Man 2nd premolar
Both have similar buccal portions outside of occlusal table,
2nd cusp variety is a round occlusal table
while the 3rd cusp variety is a more square!
Does each cusp have a triangular ridge?
yes
What separates the triangular ridges from each other?
Separated by developmental grooves that converge to form a central pit- Y Shape
Contains:
Mesial developmental groove, mesial triangular fossa, distal developmental groove (shorter than mesial), Distal triangular fossa, Lingual Developemental groove
Occlusal View 2 cusp variety
Outline of the crown is rounded lingual to the buccal cusp ridges
Some lingual convergence of the mesial and distal side occurs
Mesiolingual and Distolingual line angles rarer rounded
One well developed lingual cusp is directly across from the buccal cusp
2 Cusp Variety- Occlusal View
A central groove travels mesiodistally and can vary in a U shape to and H shape!
-Terminates in the mesial and distal fossa
Occlusal View of Man 2nd Premolars
3 Cusps- Y shape developmental groove orientation
2 Cusps- May have a U shape or H shape orientation
Determining Sides (2 Cusps)
-Tapers lingually and from mesial to distal
- Mesial cusp ridge is shorter than the distal cusp ridge
- Distal Marginal ridge is more cervical
-Distal fossa is often large and deeper
- Deeper depression on distal root surface
-Mesial Curvature of CEJ is greater
-Root Tip more often bends distally.
Determining Sides (3 Cusp)
-Mesial Cusp Ridge is shorter than the distal cusp ridge
-DMR is more cervical
-Distal fossa is larger and deeper
-Root tip bends more distally
-More often tapers from distal to mesial
-Distolingual cusp is smaller than mesiolingual
-DMR is shorter, concave and cervically located
-Distal Fossa is distal to the center of the occlusal surface
