Descriptive anatomy of Maxillary permanent premolars

Question 1

How many maxillary premolars does the adult have?

Answer 1

4; 2 in right maxilla and 2 in left maxilla

Question 2

How many lobes do the maxillary permanent premolars develop from?

Answer 2

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.

Question 3

How is the development different between maxillary permanent premolars and the rest of the anterior maxillary teeth?

Answer 3

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.

Question 4

What is the function of the maxillary first premolar?

Answer 4

The buccal cusp of the maxillary first premolar is long and sharp and functions to assist the canine as a tearing tooth.

Question 5

What is the function of the mandibular first premolar?

Answer 5

Assists the mandibular canine in tearing food

Question 6

What is the function of the second premolars?

Answer 6

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.

Question 7

How are the cusps arranged in maxillary permanent premolars?

Answer 7

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.

Question 8

When do the maxillar permanent premolars first calcify?

Answer 8

Initial calcification is at 18 - 21 months

Question 9

When is the crown completed in the maxillary permanent premolars?

Answer 9

at 5 - 6 years

Question 10

When do the maxillary permanent premolars erupt into occlusion?

Answer 10

at 10 - 11 years

Question 11

When is the root completed in the maxillary permanent premolars?

Answer 11

at 12 - 13 years

Question 12

What are the primary functions of premolars?

Answer 12

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.

Question 13

How many roots do maxillary first premolars have?

Answer 13

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

Question 14

How are roots arranged in maxillary first premolars with 2 roots?

Answer 14

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.

Question 15

What are the main characteristics of the maxillary first premolars?

Answer 15

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

Question 16

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?

Answer 16

The maxillary first premolar

Question 17

What is unique about the mesial side of maxillary first premolar?

Answer 17

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

Question 18

Why is the maxillary first premolar shaped the way it is?

Answer 18

To accomodate the distal morphology of the crown and root form of the canine

Question 19

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?

Answer 19

The distance from the buccal crest to the mesial crest is slightly longer than the distance from the buccal crest to the distal crest

Question 20

What are the dimensions of the maxillary first premolar?

Answer 20

1. 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).
2. The distance from the mesial crest to the lingual crest is much shorter than the distance from the distal crest to the Palatal crest.
3. The crown is wider on the buccal than on the lingual.
4. The buccolingual dimension of the crown is
   much greater than the mesiodistal dimension.

Question 21

How wide is the occlusal table of the maxillary first premolar?

Answer 21

The buccolingual width of the occlusal table is about 1/2 that of the total buccolingual width of the tooth crown.

Question 22

Describe the occlusal aspect of the maxillary first premolar?

Answer 22

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.

Question 23

Where is the well-defined central developmental groove located on the maxillary first premolar?

Answer 23

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.

Question 24

What developmental grooves join the central developmental groove on the maxillary first premolar?

Answer 24

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.

Question 25

Where is the triangular fossa located on the maxillary first premolar and what is it related to?

Answer 25

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.

Question 26

What are the principle identifying features of the maxillary first premolars?

Answer 26

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

Question 27

How is the maxillary second premolar different to the first premolar?

Answer 27

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.

Question 28

How many roots and root canals does the maxillary second premolar have?

Answer 28

This tooth typically has 1 root with 2 pulp canals.

Question 29

Which cuspal ridges are longer in the maxillary second molar?

Answer 29

Distal cuspal ridges of both cusps are longer than the mesial cuspal ridges.

Question 30

How are the cusps of maxillary second premolars different to those of the first premolars?

Answer 30

Maxillary second premolar has 2 cusps (buccal and lingual) that are of nearly equal size and height.

Question 31

What are the principle identifying features of maxillary second premolars?

Answer 31

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.

Question 32

What traits can be used to distinguish maxillary first and second premolars from each other?

Answer 32

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