Permanent Premolars/Bicuspids Flashcards
Are premolars always referred to as bicuspids?
No, the mandibular 2nd premolars can sometimes have 3 cusps
How many lobes form the premolars?
Most form from 4 lobes (3 buccal and 1 lingual) and have 2 cusps, except for the mandibular 2nd premolar which sometimes forms from 5 lobes (3 buccal, 2 lingual) and will have 3 cusps
Are premolars wider M/D or B/L?
Buccal/Lingual
Describe the buccal ridge of the maxillary premolars
Runs vertically down the midline w/ developmental depressions on either side
Describe the marginal ridges of the maxillary premolars
On the occlusal surface
Create a boundary that separates the occlusal surface from the peripheral surfaces (MMR, DMR)
Where are the triangular ridges of the maxillary premolars?
Occlusal surface of the cusps, runs buccal to lingual (BTR, LTR)
Describe the central groove of the maxillary 1st premolar
Spans mesial pit to distal pit
What forms the triangular fossa?
Area where the mesial/distal pits meet the triangular grooves and the M/D and B/L grooves
On which tooth do we see the marginal groove?
Only on the maxillary 1st premolar only.
Acts as a spillway
What are the triangular grooves and what do they form?
MBG/MLG and DBG/DLG
Terminate at and form the triangular fossa
Where are developmental grooves usually found?
Usually found on the occlusal surface of the maxillary 2nd premolars
Give surface a wrinkled appearance
Where is the height of contour on the mesial/distal aspects of the max 1st premolars?
Occlusal 1/3
Where is the height of contour on the buccal aspect of the max 1st premolar?
Cervical 1/3
Where is the height of contour on the lingual aspect of the max 1st premolars?
Middle 1/3
What is the function of the 1st premolars?
Tearing, supplements the function of the canines
Which tooth does the maxillary 1st premolar resemble?
Canine buccal aspect but is 1.5-2mm shorter
Root is also shorter
How curved is the CEJ of the maxillary 1st premolars?
Not as curved M/D as the canines
Which ridge on the maxillary 1st premolars is longer, the DBCR or the MBCR?
DBCR
Describe the mesial marginal groove of the maxillary 1st premolar
Extends from the occlusal table to the mesial surface and is very prominent
Describe the root depression on the max 1st premolar
Very prominent on the M/D
Where does the bifurcation occur on the root of the max 1st premolar?
Apical 1/3, buccal root is usually longer
How many roots do max 1st premolars have?
Usually 2. May have 1 but still 2 pulp canals. Can also be trifurcated w/ 3 pulp canals
2 buccal, 1 palatal
What is the function of the 2nd premolars?
Grinding. Supplementing the function of the molars
What is the size and shape of the maxillary 2nd premolars? Height difference between the cusps?
Slightly smaller than the 1st premolars and more rounded
Cusps are almost equal in height
Do the max 2nd premolars have a MMG?
No
What is the shape/contour of the buccal cusp ridge on the max 2nd premolars?
More curved
Do the max 2nd premolars have a central groove?
Sometimes. It will be shorter or not there at all with just a pit w/ supplemental grooves on the occlusal surface
How many roots do the max 2nd premolars have?
Usually a single root w/ one pulp canal but will occasionally have 2 pulp canals and may bifurcate
Of the two maxillary premolars, which has the longer root?
2nd, has a mesial root depression
What is the height of contour on the mesial/distal aspects of the mandibular 1st premolars?
Middle 1/3
What is the height of contour on the buccal aspect of the mand 1st premolars?
Between the cervical and middle 1/3’s
What is the height of contour on the lingual aspect of the mand 1st premolars?
Middle 1/3, near cusp tip
What is the difference in the cusp tips between the max/mand 1st premolars?
Cusps are more blunt on the mandibular
Describe the CEJ on the mand 1st premolars
Fairly straight w/ a slight curve toward the occlusal
Describe the crown form of the mand 1st premolar
Cusp tip sits over the root and occlused with the max fossa
What can you see from the lingual aspect of the mand 1st premolars?
Lingual cusp is in line with the BTR forming a True Transverse Ridge
MLG is visible and prominent
What is the shape of the occlusal table on the mand 1st premolar?
Triangular
Describe the mesial triangular fossa (MTF) on the mand 1st premolars
Smaller w/ a pit that the MLG courses from
Describe the distal triangular fossa (DTF)
Larger w/ a pit
Describe the roots of the mand 1st premolar
May have a mesial root depression
One root with one pulp canal- may have 1 root with 2 pulp canals and may also bifurcate
Describe the shape of the mandibular 2nd premolars
Shaped more like a molar w/ well developed lingual cusps
Describe the buccal aspect of the mand 2nd premolars
Smoother, usually with no developmental depressions and lass prominent BCR
Describe the occlusal shape on the mand 2nd premolars
Round or squared and very symmetrical
What are the two cusp types of mand 2nd premolars?
3 cusp type
2 cusp type
How many lobes form the 3 cusp type mand 2nd premolars?
5 lobes- 3 buccal (1 cusp), 2 lingual (2 cusps)
Mesiolingual cusp is larger than the distal lingual cusp
Lingual groove is only present on the 3 cusp type
How many lobes form the 2 cusp type mand 2nd premolars?
4 lobes- 3 buccal, 1 lingual
What are the 3 variations of occlusal patters in mand 2nd premolars?
U, H and Y
How many cusps/fossa on the U-shaped and H-shaped occlusal patterns?
2 cusps
3 fossa
How many cusps/fossa in the Y-shaped occlusal pattern of the mand 2nd premolars?
3 cusps
3 fossa
Describe the root of the mand 2nd premolars
Single root with 1 or 2 pulp canals
Larger and longer than the mand 1st premolar
May bifurcate with a deep developmental groove on the mesial
