Maxillary first premolar Flashcards
Posterior Teeth
Include:
1st and 2nd Pre-Molars, as well as the 1st, 2nd, and Third Molars
Characteristics of Posterior Teeth
- Greater relative faciolingual measurement compared with mesiodistal
- Broader contact areas- thick
- Contact areas are more nearly at the same level
- Less curvature of the cervical line and mesially and distally
- Shorter crown crevico-occlusally than that of anterior teeth- low to the floor
Pre Molars in General
4 in each arch, replace the deciduous molars (thus, no pre molars in primary dentition)
- Bicuspid= two cusps
Mandibular Pre Molar variation in cusps
can range from 1-3 cusps
Where are the cusps and roots located?
They’re placed buccal and lingually, roots are also placed buccal and lingually
Which cusp of a max and mand 1st premolar is long and sharp?
Buccal cusp of the max and mandibular is the longest and sharpest. Similar to how the neighboring canine has that one cusp that is apprehensive for prehensile/tearing tooth
How is the buccal cusp of the max and mand 2nd premolar?
It is less sharp and in articulation with the opposing teeth making them more efficient and grinding like molars
KEY NOTE: THE BUCCAL CUSP IS LIKE THE CUSP OF A CANINE
WHILE THE LINGUAL CUSP IS MORE LIKE THE SURFACE OF MOLARS
What type of plane do the marginal ridges exist in?
They exist in more of a horizontal plane!, as part of the occlusal surface, instead of part of the lingual surface like anterior teeth.
Facial Aspect
Mesial- Middle Third
Distal- Middle Third
Proximal Aspect
Buccal- Cervial Third
Lingual- Middle Third (note that because the lingual cusp is shorter)
Occlusal Aspect
Occlusal Aspect
Mesial- junction of the middle and buccal third
Distal- middle third
Occlusal Aspect
Buccal- Middle Third
Lingual- Middle Third
First calcification
1.5-1.75
enamel completion
5-6 years
eruption
10-11 years
root completion
12-13 years
Measurements
Mesial distal crown width is shorter than the facial lingual crown length.
Roots
Usually have two, with two pulp canals!
If one root is present there are usually still two canals!
How many lobes do the maxillary 1st premolar develop from?
Develop from the 4 lobes just like anterior teeth, main difference is a well-formed lingual cusp, from the lingual lobe.
Crowns are shorter than the canines
Is the mesial cusp ridge of the buccal cusp longer than the distal cusp ridge?
The mesial cusp ridge is longer than distal cusp ridge. OPPOSITE of maxillary canine and opposite of the maxillary second premolar
NOT as wide mesiodistally as maxillary canine
What is the crown shape of a maxillary 1st premolar?
The crown shape is a trapezoidal shape
How is the mesial outline on the buccal aspect?
The mesial outline is slightly concave near the CEJ to the mesial contact area, and the mesial contact area is a relatively broad curvature.
Mesial Contact Area
In the Middle Third, is a relatively broad curvature, the crest of which immediately occlusal to the halfway portion from the CEJ to the tip of buccal cusp.
Mesial Buccal Cusp Ridge
IS STRAIGHTER AND LONGER than distal.
Distal cusp ridge is more round and shorter.
Can the mesial slope of the buccal cusp sometimes be notched or have an appearance of a concave outline?
YES
You draw a bisecting line down, where does the tup of the buccal cusp relate to bisecting line on the buccal surface of the crown?
It is located distally!
Distal Outline on Buccal Aspect
Distal outline from CEJ to height of contour is straighter than mesial but also may be concave,
Focus more on the distal contact area is represented by a BROADER curvature!
Which lobe is more defined, gives a convex appearance?
Middle Buccal Lobe
Buccal Ridge
From the buccal cusp tip to the CEJ on the buccal surface of crown!
Are there developmental depressions on the mesial and distal surfaces of the buccal ridge?
YES- found in the occlusal thirds!
Roots longer or shorter than the maxillary canine?
SHORTER
Lingual Aspect
Crown tapers to the lingual because lingual cusp is narrower mesiodistally than the buccal cusp.
Both cusps are visible from this view!
CEJ has a greater curvature towards apex than on the buccal aspect.
Mesial Aspect Shape
Trapezoidal in shape- the horizontal line across the cervix is longer than a horizontal line drawn at the cusp tips.
Curvature of the CEJ
Still greater on the mesial, but not as defined as compared to anterior teeth.
Buccal outline from the mesial aspect
Curves outward from the CEJ to the height of contour, and then extends to cusp tip with less convexity.
Height of Contour on the Buccal Surface
At the junction between the middle and gingival/cervical third, or within the gingival third!
Is the buccal cusp tip inline with the middle of the buccal root?
YES
Lingual Outline on Mesial Aspect
smooth curved line starting on the CEJ and ending on the lingual cusp tip.
Crest of Curvature of lingual
Is at the MIDDLE 3rd!
Where does the mesial marginal ridge sit?
On the junction of the middle and incisal third!
Mesial marginal developmental groove
Extends across the mesial marginal ridge onto the mesial proximal surface directly lingual to the mesial contact area
Mesial developmental depression
Sits cervical to the mesial contact area, centered on the mesial proximal surface and bordered bucally and lingually by mesiobucacal and mesiolingual angles.
Even with one rooted 1st premolar the root depression is VRY NOTICEABLE for most of root length!
Buccal Outline from the Mesial aspect
Relatively straight compared to a lingual inclination
Once the root bifurcates, the root may have a buccal curve in which the buccal outline is straight from CEJ to apex or buccal curve in the middle third root.
Lingual root is relatively straight but may curve towards the buccal or lingual
Mesial Aspect: What makes up about 1/2 the root length in the bifurcated root?
Root Trunk
What is the mesial marginal ridge rule on max 1st and 2nd premolars?
Mesial marginal ridges are more occlusal than the distal marginal ridge
Distal Aspect
-Crown surface is convex at all points except for a small, flattened arc cervical to the contact area and buccal to the center of distal surface.
CEJ has less curvature
Is there a distal marginal developmental groove?
NO
Is the root trunk flat without a development depression on the distal side?
YES
What is the shape of the crown on the occlusal aspect?
Irregular Hexagonal Shape
- Wider on the Buccal than the Lingual
The crest of the buccal ridge in comparison to the crest of the lingual ridge?
DISTAL to
The crest of the buccal ridge in comparison to the crest of the lingual ridge?
DISTAL to
Mesial Contact area is _______ to the distal contact area
Lingual
Buccal cusp tip
Distal on a bisecting line
Mesiobuccal cusp ridge longer or shorter than distobuccal ridge?
Longer
TRUE OR FALSE: ALL other premolars have a buccal cusp slightly MESIAL to a bisecting line
TRUE- in this case- the max 1st pre molar has buccal cusp tip to the Distal
Where is the lingual cusp tip located in regards to a bisecting line?
MESIAL for both maxillary premolars
What is circumscribed by the cusp ridges and marginal ridges?
the occlusal surface– aka the occlusal table
Occlusal Table
Buccal cusp tip
Mesiobuccal cusp ridge
Mesiomarginal ridge
Mesiolingual cusp ridge
Lingual cusp tip
Distolingual cusp ridge
Distal marginal ridge
distobuccal cusp ridge
buccal cusp tip`
What is more visible from the occlusal view- buccal surface or lingual surface?
Buccal Surface
Are there any supplemental grooves visible?
NO- relatively smooth occlusal surface then
What divides the surface evenly buccolingually?
Central Developmental Groove
What is near the distal marginal ridge?
The distobuccal developmental groove that joins the central groove
What comes off the central groove that extends towards the mesial aspect of the buccal surface?
mesiobuccal developmental groove
True or False: The mesial side of the central groove joins the mesial marginal developmental groove, which crosses the mesial marginal ridge and ends on the mesial surface?
True
What happens at the junction of these grooves?
They are deep and referred to as the mesial and distal developmental pits
What surrounds these pits?
Two depressions on the occlusal surface around these pits are called the mesial and distal triangular fossa.