Mandibular first premolar Flashcards
First Calcification
1.75-2 years
Enamel complete
5-6 years
eruption
10-12 years
root completion
12-13 years
Measurements
Facial Lingual is wider than the Mesial Distal
Also, the root length is longer than crown length
2 cusps
How many lobes does it develop from?
4 lobes
Which cusp is more dominant, buccal or lingual?
Buccal
What is the most common pulp canal percentage?
1 canal/1 foramen 73.5%
Distal Curvature as well
How does the mandibular first pre molar resemble the canines?
-Buccal cusp is long and sharp!
The Buccolungual measurement is similar to that of the canine
-The occlusal surface slopes sharply lingual in the cervical direction
-Mesiobuccal cusp ridge is SHORTER than the distal buccal cusp ridge!
-The occlusal outline resembles the canine incisal outline
Resembles the 2nd pre-molar in that…
-Outline of crown and root from the buccal outline resembles that of the second premolar–except for the longer cusp!
- Mesial and distal contact areas are new the same level
- Curvature of the cervical in the mescal and distal are similar
-tooth has more than one cusp!
- Though generally shorter in length than the 2nd premolar, the root is closer in length than that of the 2nd pre molar
Buccal aspect
MESIAL CUSP RIDGE IS SHORTER Than the distal cusp ridge
Contact area: Broad and near the same levels mesial and distally
– Within the MIDDLE 3rds!!
What type of shape is the crown?
The crown is a trapezoidal shape, with the shorter of the two sides at the CEJ.
Cusp tip is pointed and slightly mesial to a center line
Buccal Surface - distal info
Distal outline above the CEJ to contact area is slightly concave, curvature of the contact area is broader than on mesial side.
Lingual Aspect
Crown tapes toward the lingual and a significant portion of the mesial and distal surfaces are visible from this aspect.
Lingual cusp tip is always small, little more than a cingulum.
Occlusal surface is sloped toward the lingual down to the lingual cusp.
Majority of occlusal surface is viewable.
MOST OF THE CROWN IS MADE UP OF THE MIDDLE BUCCAL LOBE giving it an appearance like a mandibular canine.
Are the mesial and distal concavities viewable above the CEJ up to contact areas?
Yes
Why are these mesial and distal contact areas more pronounced?
Due to the narrow cervical line
From the lingual aspect, what is a characteristic of the mandibular first pre molars?
The mesiolingual developmental groove- which lies between the mesiobuccal lobe and the lingual lobe and extends onto the occlusal surface.
Root
Significantly narrower on the lingual, forms a convex ridge from the CEJ to the cervix
Thus, mesial and distal surfaces are visible.
Root has an even taper from the cervix to a pointed apex
Mesial Aspect *
Corn is roughly rhomboidal from the mesial aspect, this is a characteristic of mandibular posterior teeth.
Where is the tip of the buccal cusp located in comparison with the root?
Nearly centered over the root
Where is the the tip of the lingual cusp located in comparison with the root?
Lingual cusp tip is IN LINE with the lingual border of the root, and the lingual outline of the crown is LINGUAL to the outline of the root- overhang
*Differs from all maxillary posterior teeth where the cusp tips are well within the confines of the root trunk!
From the mesial aspect, is the buccal outline curved from the cervical line to cusp tip?
YES
Where is the crest of curvature located on the Buccal?
IN THE CERVICAL THIRD or near the junction of the cervical and middle 3rd
This is a characteristic of all mandibular posterior teeth
Where is the crest of curvature located on the lingual?
IN THE MIDDLE THIRD
-Lingual aspect is less convex than the facial outline
-The distance from the cervix to the lingual cusp tip is 2/3 the distance from cervix to the buccal cusp tip.
How much of the occlusal surface is visible from the mesial aspect?
Only about 1/2 because of the mesial marginal ridge to the buccal triangular ridge is not as high!
How is the curvature of the CEJ on the mesial aspect?
Slight curvature towards the occlusal surface, may be straight across.
Root on the Mesial Surface
- Root outline tapers from the cervix to the apex IN LINE with the buccal cusp tip.
Lingual outline of the root may be straight and angular with the buccal curved.
Root on the Mesial Surface
- Root outline tapers from the cervix to the apex IN LINE with the buccal cusp tip.
Lingual outline of the root may be straight and angular with the buccal curved.
Is there a developmental groove on the mesial surface of the root?
YES
Distal Aspect
DISTAL MARGINAL RIDGE IS UP HIGHER ABOVE THE CERVIX THAN the mesial marginal ridge and does not have an extreme slope!
THE distal marginal ridge is confluent with the lingual cusp with no marginal developmental groove
Is the distal contact are broader than mesial?
YES
TRUE or FALSE: THE distal root surface exhibits less convexity than the mesial
Flase
Distal Root
Does contain a shallow developmental depression- but rarely contains a deep one.
From the occlusal aspect, what shape is the Mandibular 1st pre-molar?
Diamond- but lots of variation in shapes.
All mandibular 1st premolars have the following aspects:
Middle Buccal Lobe makes up the majority of the crown
Buccal Ridge is Prominent
Mesiobuccal and distobuccal ridges are prominent
All mandibular 1st premolars have the following aspects:
Curvatures representing the M&D contact areas are broad, but broader on distal
Crown converges sharply to lingual
Marginal ridges are prominent
Lingual cusp is small
Buccal triangular ride is dominant on occlusal view with the lingual triangular ridge small!
What surrounds the mesial and distal transverse ridges?
Mesial and Distal fossae
At the base these fossa, there appears to be a what?
A developmental groove and or pit
On the mesial fossa
mesial developmental groove
On the distal fossa
Distal developmental pit, may also have a distal developmental groove
Does the mandibular first premolar have a central groove?
NO- thus gives the appearance of “snake eyes” because of prominent mesial and distal fossae and associated pits
What is exiting the occlusal surface onto the mesial lingual part of the tooth?
a mesiolingual developmental groove- extending out of the mesiolingual fossa
What is the shape of the distal 1/2 of the occlusal?
semicircular
What surface of the crown is visible the most from the occlusal aspect?
The buccal surface because crown is tilted towards the lingual.
