Maxillary 1st Premolar Flashcards
List the functions of premolars
-mastication
-assisting molars in grinding and canines in tearing
-maintain vertical dimensions of the face
-support corners of mouth and cheeks
when do the mx 1st premolars calcify?
1.5 yrs
when do the mx 1st premolars erupt?
10-11yrs
when do the mx 1st premolars root complete?
12-13yrs.
The facial view outline shape is…
pentagonal
Compared to the canine, mx 1st premolars are…
-shorter
-narrower mesiodistally
-sharper mesial and distal marginal ridges
Facial view height of contour
cervical 3rd
Facial view mesial outline
-concave from the contact area to the cervical line
-prominent mesiocclusal angle
Facial view distal outline
similar to mesial but no concavity
mesial contact area
middle 3rd
distal contact area
middle 3rd (but more cervical than mesial)
crown surface
convex
Facial View: the cusp tip is offset to the…
distal
Mesial cusp ridge
longer and straighter
may have slight concavity
BEING LONGER IS UNIQUE TO MX 1st PM
Distal cusp ridge
shorter and more convex
Facial ridge
-extends from facial cusp to cervical line
-extremely well developed*
-result of middle facial lobe
-depressions on each side
The crown tapers towards the…
lingual
The lingual surface is…
smooth and convex
*NO lingual ridge
Which cusp is shorter, lingual or buccal?
lingual by 1-1.3mm
Lingual view: the cusp tip offsets to the…
mesial
Which slope is short, the mesial lingual or the mesial facial
mesial lingual is shorter
Lingual view height of contour
middle 3rd
Lingual view mesial cusp ridge
shorter than the distal, small portion of buccal cusp can be seen from lingual view
The proximal outline shape of the mx 1st premolar is…
trapezoidal
Proximal view: the cusp tips are _____ over the root
centered; within the confines of the root*
Proximal view: CEJ
cervical line less curved on distal compared to mesial
Mesial marginal ridge groove
crosses well developed MMR and continued onto to root
*not always present
*special considerations when scaling
Mesial developmental depression
on middle portion of cervical 3rd of crown, continues onto root across the CEJ, joining the developmental depression of the root
*usually quite prominent
Distal proximal view
-no grooves crossing the DMR
-no developmental depression
-more rounded and smooth
What is the occlusal outline shape of the mx 1st premolar
hexagonal
Occlusal view: the crown is wider on which surface, buccal or lingual
buccal
Occlusal view: the crown is wider…
buccolingually than mesiodistally
Occlusal view: distal proximal contact
facial to the mesial contact
Occlusal view: mesial proximal contact
lingual to the distal contact
Occlusal view: lingual vs facial cusp
lingual: more pointed
facial: larger wider and longer
Occlusal view: name the 4 cusp ridges
facial, lingual, distal, mesial
Occlusal view: triangular ridges
runs from cusp tip to central groove
*eventually join to form a transverse ridge
Occlusal table
area bounded by the perimeter of the ridges
Mesial marginal ridge
shorter than the DMR, located more occlusal than the DMR
has MM groove running through it
On the facial cusp, which cusp ridge is longer?
mesial facial is longer than distal facial
Name the developmental grooves of the mx 1st premolar
sharp deep and V shaped
-central
-mesial marginal
-mesiobuccal developmental
-distobuccal development
Name the 2 fossae
mesial triangular fossa
distal triangular fossa
Compared to the 2nd PM, there are _____ secondary/supplemental grooves
fewer
Name the developmental pits
mesial- intersection of MB, ML, MM, and central grooves
distal- intersection of DB, DL and central grooves
The lingual surface of the root is ______ than the buccal
narrower
mesial view of root
-deep depression
-mesial marginal groove continues with mesial depression
distal view of root
-convex or flat near cervical
-not as deep depression as on mesial
which type of root is more common, single or bifurcated?
bifurcated (1 buccal 1 lingual)
what is the root trunk?
the area between cervical line and point of furcation
number of pulp horns=
number of cusps
Type I root
-single root w/ deep mesial groove
-usually 2 root canals w/ 1 apical foramen
-2 pulp horns
Type II root
bifurcated- facial and lingual
-bifurcation apical to the 1/2
-facial roots longer and larger
-hardest to do root canal treatment
Type III root
laminated (fused) roots- buccal and lingual joined
Comparisons with anterior teeth
-greater faciolingual than mesiodistal
-mesial and distal contact areas broader and closer to same level on the tooth
-less mesial and distal curvature of cervical line
-shorter crowns
