Descriptive anatomy of Maxillary permanent premolars Flashcards
How many maxillary premolars does the adult have?
4; 2 in right maxilla and 2 in left maxilla
How many lobes do the maxillary permanent premolars develop from?
Same as anterior teeth - 4
The primary difference in development is the well-formed Palatal cusp,
developed from the lingual lobe, which is represented by the cingulum development on incisors and canines.
How is the development different between maxillary permanent premolars and the rest of the anterior maxillary teeth?
The primary difference in development is the well formed palatal cusp developed from the lingual lobe which is represented by the cingulum development on the incisors and the canines.
What is the function of the maxillary first premolar?
The buccal cusp of the maxillary first premolar is long and sharp and functions to assist the canine as a tearing tooth.
What is the function of the mandibular first premolar?
Assists the mandibular canine in tearing food
What is the function of the second premolars?
Both maxillary and mandibular second premolars have cusps less sharp than the first premolars and articulate with opposing teeth like grinding teeth making them more functional like molars.
This is to a lesser degree due to their reduced surface area.
How are the cusps arranged in maxillary permanent premolars?
Because of the cusp development buccally and palatally the marginal ridges are in a more horizontal plane and are considered part of the occlusal surface of the crown rather than part of the lingual surface as is the case of incisors and canines.
When do the maxillar permanent premolars first calcify?
Initial calcification is at 18 - 21 months
When is the crown completed in the maxillary permanent premolars?
at 5 - 6 years
When do the maxillary permanent premolars erupt into occlusion?
at 10 - 11 years
When is the root completed in the maxillary permanent premolars?
at 12 - 13 years
What are the primary functions of premolars?
Mastication.
Assist in maintaining vertical dimension of the face.
The first premolars assist the canines in shearing, tearing, or cutting food morsels.
Premolars support the corners of the mouth and cheeks and contribute in the prevention of facial sagging.
Contributes in determining the arch shape of the individual patient. Arch shape can be categorized as square, tapering, or ovoid.
How many roots do maxillary first premolars have?
Variations range from one to three roots
Approximately 70 - 80% of maxillary premolars have 2 roots and 2 root canals
20 - 30% have a single root
Occasionally there are three rooted premolars. These are very hard to treat as it can have a complex canal system
How are roots arranged in maxillary first premolars with 2 roots?
1 is placed buccally and and 1 is placed palatally
The buccal cusp is usually larger and longer than the palatal cusp
The crown is shorter than that of the canine by 1.5 to 2mm on average.
What are the main characteristics of the maxillary first premolars?
Greater relative faciopalatal measurement compared with the mesiodistal measurement
Broader contact areas
Contact areas are at a similar level or height
Less curvature of the cervical line mesially and distally
Shorter crown, cervico-occlusally than that of anterior teeth
Which premolar has a mesial cusp ridge that is longer than the distal cusp ridge and the buccal cusp located slightly distal to the mid-root axis?
The maxillary first premolar
What is unique about the mesial side of maxillary first premolar?
The mesial marginal ridge is crossed by a substantial groove. This does not occur at the distal marginal ridge.
Mesial crown surface has a relatively deep developmental depression
Mesial development root depression is deeper than the distal root depression
Why is the maxillary first premolar shaped the way it is?
To accomodate the distal morphology of the crown and root form of the canine
Which is longer on the maxillary first premolar; the distance from the mesial crest to the buccal crest or the distance from the buccal crest to the distal crest?
The distance from the buccal crest to the mesial crest is slightly longer than the distance from the buccal crest to the distal crest
What are the dimensions of the maxillary first premolar?
- The distance from the buccal crest (A) to the mesial crest (C) is slightly longer than the distance from the buccal crest to the distal crest (D).
- The distance from the mesial crest to the lingual crest is much shorter than the distance from the distal crest to the Palatal crest.
- The crown is wider on the buccal than on the lingual.
- The buccolingual dimension of the crown is
much greater than the mesiodistal dimension.
How wide is the occlusal table of the maxillary first premolar?
The buccolingual width of the occlusal table is about 1/2 that of the total buccolingual width of the tooth crown.
Describe the occlusal aspect of the maxillary first premolar?
Occlusal surface of the tooth has no supplemental grooves in most cases making the surface relatively smooth
Well-defined central developmental groove divides the surface evenly buccopalatally. This is located at the bottom of the central sulcus of the occlusal surface.
Where is the well-defined central developmental groove located on the maxillary first premolar?
It is located at the bottom of the central sulcus of the occlusal surface, extending from a point just mesial to the distal marginal ridge to the mesial marginal ridge, where it joins the mesial marginal developmental groove. This latter groove crosses the mesial marginal ridge and ends on the mesial surface of the crown.
What developmental grooves join the central developmental groove on the maxillary first premolar?
These grooves are called the mesiobuccal developmental groove and the distobuccal developmental groove. The junctions of these grooves are deeply pointed and are named the mesial and distal developmental pits.
Where is the triangular fossa located on the maxillary first premolar and what is it related to?
Just distal to the mesial marginal ridge, the triangular depression that harbours the mesiobuccal developmental groove is called the mesial
triangular fossa. The depression in the occlusal surface, just mesial to the
distal marginal ridge, is called the distal triangular fossa.
What are the principle identifying features of the maxillary first premolars?
2 roots, buccal and lingual and tend to curve distally.
2 sharply-defined cusps: Buccal larger than palatal
Concave canine fossa on mesial surface of crown extending to pronounced longitudinal groove on mesial surface of root.
Central developmental groove interrupts mesial marginal ridge
Mesial slope of buccal cusp longer than distal
Palatal cusp mesially placed in relation to buccal cusp
Occlusal outline more angular than the upper second premolar
How is the maxillary second premolar different to the first premolar?
Maxillary second premolar supplements 1st premolar in function. Both resemble each other significantly.
The second premolar is smaller than the first premolar.
Root is as long or occasionally even longer than the 1st maxillary premolar.
Buccal ridge is not as prominent as that of the maxillary first premolar.
This tooth will usually present with more supplemental occlusal anatomy.
How many roots and root canals does the maxillary second premolar have?
This tooth typically has 1 root with 2 pulp canals.
Which cuspal ridges are longer in the maxillary second molar?
Distal cuspal ridges of both cusps are longer than the mesial cuspal ridges.
How are the cusps of maxillary second premolars different to those of the first premolars?
Maxillary second premolar has 2 cusps (buccal and lingual) that are of nearly equal size and height.
What are the principle identifying features of maxillary second premolars?
2 cusps: 1 palatal, 1 buccal: Shallower and more equal in size than upper first premolar.
No canine fossa - mesial surface is convex
Oval occlusal outline
Single root flattened mesiodistally - longer than roots of upper first premolar
Mesial slope of buccal cusp shorter than distal slope. This is the opposite of upper first premolar but similar to upper canine.
Occlusal mesiodistal fissure does not interrupt mesial marginal ridge.
What traits can be used to distinguish maxillary first and second premolars from each other?
Maxillary 1st:
Mesial buccal ridge
depression 50 - 55%
Sharper Buccal cusp angle
Bulging shoulders and angular outline
Tapers more from the contacts cervically
Mesial cusp arm longest
Prominent buccal ridge.
Maxillary 2nd:
Distal buccal depression 20 - 25%
More blunt buccal cusp angle
Narrow, more rounded shoulders
Less taper from contacts cervically
Distal cusp arm longest
Less prominent bulge
