120 Questions
What is the characteristic of the occlusal surface of the three-cusp version of the mandibular second premolar?
It is broader on the lingual aspect
What is the characteristic bulk of the three-cusp version of the mandibular second premolar?
Greater bulk buccolingually in the distal
What is the characteristic of the ML cusp compared to the DL cusp in the three-cusp version of the mandibular second premolar?
ML cusp is larger than the DL cusp
What is the characteristic of the ridges in the three-cusp version of the mandibular second premolar?
Three triangular ridges converging towards the central fossa
What is the characteristic of the central fossa in the three-cusp version of the mandibular second premolar?
It is shifted towards the distal
What is the characteristic of the lingual groove in the three-cusp version of the mandibular second premolar?
It separates the two lingual cusps
What is the unique characteristic of the Distal Marginal Ridge (DMR) of the Mandibular 1st Premolar?
It is more occlusal than the Mesial Marginal Ridge
What is the shape of the proximal aspects of the Mandibular 1st Premolar?
Mesial Rhomboid
What is the relative length of the Lingual cusp compared to the length of the crown?
It is shorter by 1/3 length of the crown
What is the orientation of the Mesial Marginal Ridge (MMR) of the Mandibular 1st Premolar?
It is inclined from B to L surface
What is the characteristic of the cervical line of the Mandibular 1st Premolar?
It curves occlusally and less curved distally
What can be observed in the occlusal aspect of a mandibular first premolar?
A shallow central groove extending from mesial to distal fossa
What is the characteristic of the Mesio-Lingual surface of the Mandibular 1st Premolar?
It has a developmental groove
What is characteristic of the lingual cusp in a mandibular second premolar?
It is smaller than the buccal cusp
What can be observed in the occlusal surface of a mandibular second premolar?
A square occlusal table with a round or oval-shaped crown
What is the shape of the fossae in a mandibular first premolar?
Circular or irregular
What is characteristic of the ridges in a mandibular second premolar?
More supplemental grooves than a mandibular first premolar
What can be observed in the mesial half of a mandibular second premolar?
More bulk than the distal half buccolingually
What is unique about the mesial marginal ridge of the mandibular 1st premolar?
It is more apical than the distal marginal ridge
What can be seen from the lingual aspect of the mandibular 1st premolar?
Most of the occlusal surface
How many lingual cusps does the mandibular 2nd premolar have?
Either 1 or 2
What is the relative size of the lingual cusp of the mandibular 2nd premolar with 1 lingual cusp compared to the lingual cusp of the mandibular 1st premolar?
Larger
In the mandibular 2nd premolar with 2 lingual cusps, which cusp is larger?
The ML cusp
What is the shape of the crown of the mandibular 1st premolar?
Tapered to the lingual
What is the distinctive feature of the mesial surface of the root of the 2nd premolar?
It is more convex
What is the characteristic of the proximal aspect of the 2nd premolar?
The buccal height of contour is at the junction of the cervical and middle 1/3
What is the shape of the crown of the mandibular first premolar?
Diamond shaped converging lingually
What is the characteristic of the cusp ridges of the mandibular first premolar?
They are nearly straight lines
What is the feature of the root of the mandibular 2nd premolar?
It has a distal root depression in the middle third
What is the characteristic of the occlusal aspect of the mandibular first premolar?
It appears as if the mesial side has been pushed inward
What is the distinguishing feature of the cervical line of the mandibular 1st premolar compared to the 2nd premolar?
It is more rounded mesiodistally
Which of the following is a characteristic of the crown shape of the mandibular 2nd premolar?
Roughly pentagonal
What is the location of the contact area of the mandibular 1st and 2nd premolars?
Near the junction of the occlusal and middle third
Which of the following is a characteristic of the buccal cusp of the mandibular 2nd premolar?
It is less pointed
Where are notches often seen on the cusp ridges of the mandibular 1st premolar?
On the mesiobuccal cusp ridge
What is the relative length of the crown and root of the mandibular 1st premolar compared to the 2nd premolar?
The crown is longer and the root is shorter
Which of the following is a characteristic of the overall length of the mandibular 1st premolar compared to the 2nd premolar?
It is longer
Where is the distal contact area of the mandibular 2nd premolar located?
More cervical than the mesial contact area
What is the characteristic of the cusp ridges of the mandibular 2nd premolar compared to the 1st premolar?
They are less steep
Which of the following is a characteristic of the crown shape of the mandibular 1st premolar?
Nearly symmetrical except for a shorter mesial cusp ridge and a distal bulge of the crown
What is the characteristic of the buccal triangular ridge in the mandibular first premolar?
It is longer than the lingual triangular ridge
What is the characteristic of the fossae in the occlusal aspect of the mandibular first premolar?
They are irregular or circular in shape
What is the characteristic of the transverse ridge in the occlusal aspect of the mandibular first premolar?
It is always smooth and uninterrupted
What is the characteristic of the crown shape of the mandibular second premolar?
It is round in shape
What is the characteristic of the marginal ridges in the mandibular first premolar?
They converge lingually
What is the characteristic of the central groove in the occlusal aspect of the mandibular second premolar?
It is curved
In the three-cusp version of the mandibular second premolar, which of the following is true about the bulk?
It is greater buccolingually in the distal
What is unique about the central fossa in the three-cusp version of the mandibular second premolar?
It is shifted towards the distal
What is characteristic of the ridges in the three-cusp version of the mandibular second premolar?
They converge towards the central fossa
What is the relationship between the ML cusp and the DL cusp in the three-cusp version of the mandibular second premolar?
The ML cusp is larger than the DL cusp
What is the characteristic of the lingual groove in the three-cusp version of the mandibular second premolar?
It separates the two lingual cusps
What is the characteristic of the occlusal surface of the three-cusp version of the mandibular second premolar?
It is broader on the lingual
What is the characteristic of the buccal cusp in relation to the root of the mandibular 1st premolar?
It is centered over the root.
What is the characteristic of the buccal cusp tip from an occlusal view of the mandibular first premolar?
Near the center
What can be observed in the occlusal morphology of the mandibular first premolar?
A diamond-shaped crown
What is the shape of the proximal aspects of the mandibular 1st premolar?
Rhomboid
What is the orientation of the mesial marginal ridge of the mandibular 1st premolar?
Parallel to the buccal cusp ridge
What is the characteristic of the convergency of the crown shape of the mandibular first premolar?
It converges lingually
What is the characteristic of the marginal ridges of the mandibular first premolar?
The mesial marginal ridge is more prominent
What is unique about the distal marginal ridge of the mandibular 1st premolar?
It is more occlusal than the mesial marginal ridge
What is the characteristic of the ridges in the mandibular second premolar?
They are nearly straight lines
What is the characteristic of the occlusal margin of the mandibular 1st premolar?
The lingual cusp is shorter than the buccal cusp
What is the characteristic of the developmental groove on the root of the mandibular premolar?
It is deep and narrow
What is the location of the mesiolingual developmental groove of the mandibular 1st premolar?
At the junction of the lingual and mesial surfaces
What is the characteristic of the lingual cusp of the mandibular 1st premolar?
Small and pointed
What is the relative size of the mesial marginal ridge compared to the distal marginal ridge in the mandibular 1st premolar?
Mesial is more apical
What is the characteristic of the crown shape of the mandibular 2nd premolar with 2 lingual cusps?
Wide or wider mesiodistally than the buccal
What is the characteristic of the mesial marginal ridge compared to the distal marginal ridge in the mandibular 2nd premolar?
Mesial is more occlusal
What is the relationship between the ML cusp and the DL cusp in the mandibular 2nd premolar with 2 lingual cusps?
ML cusp is larger than the DL cusp
What is the characteristic of the lingual cusp of the mandibular 2nd premolar with 1 lingual cusp compared to the lingual cusp of the mandibular 1st premolar?
Larger than the lingual cusp of the 1st premolar
What is the primary distinguishing characteristic of the buccal cusp of the mandibular 2nd premolar?
Less pointed than the 1st premolar
What is the characteristic shape of the crown of the mandibular 1st premolar?
Roughly trapezoidal
Where are notches often seen on the cusp ridges of the mandibular 2nd premolar?
Distal cusp ridge
What is the characteristic feature of the cervical line of the mandibular 1st premolar?
More rounded mesiodistally
What is the relative length of the mandibular 1st premolar compared to the 2nd premolar?
Longer crown and shorter root
What is the characteristic feature of the contact areas of the mandibular 1st and 2nd premolars?
Mesial contact area is more cervical
What is the characteristic shape of the crown of the mandibular 2nd premolar?
Roughly pentagonal
Where is the distal contact area located on the mandibular 2nd premolar?
More cervical than the mesial contact area
What is the characteristic feature of the marginal ridges of the mandibular 1st premolar?
More rounded mesiodistally
What is the primary distinction in the occlusal morphology of the mandibular 1st and 2nd premolars?
Shape of the crown
What is the characteristic of the transverse ridge in the occlusal aspect of the mandibular first premolar?
It may be crossed by a shallow central groove extending from mesial to distal fossa.
What is the characteristic of the buccal cusp of the mandibular second premolar?
It is larger than the lingual cusp.
What is the characteristic of the crown shape of the mandibular first premolar?
It is round or oval shaped with a square occlusal table.
What is the characteristic of the marginal ridges of the mandibular first premolar?
They converge lingually and form a uninterrupted transverse ridge.
What is the characteristic of the fossae in the occlusal aspect of the mandibular first premolar?
They are irregular or circular in shape and have pits.
What is the characteristic of the ridges in the mandibular second premolar?
They are more prominent and have more supplemental grooves.
What is the characteristic of the occlusal surface of the three-cusp version of the mandibular second premolar?
Broader in the lingual aspect
What is the characteristic of the lingual groove in the three-cusp version of the mandibular second premolar?
Completes the Y-shaped occlusal groove pattern
What is the characteristic of the marginal ridges of the three-cusp version of the mandibular second premolar?
Convergent in the mesial and distal aspects
What is the characteristic of the central fossa in the three-cusp version of the mandibular second premolar?
Shifted towards the distal aspect
What is the characteristic of the ridges in the three-cusp version of the mandibular second premolar?
Triangular in shape and converging towards the central fossa
What is the characteristic of the crown shape of the mandibular second premolar?
Asymmetrical in the buccal and lingual aspects
On the occlusal surface of the mandibular first premolar, what is the characteristic feature of the buccal cusp?
It lacks a prominent buccal ridge
What is the characteristic shape of the crown of the mandibular first premolar?
Asymmetrical and diamond-shaped
On the occlusal surface of the mandibular first premolar, what is the characteristic feature of the cusp ridges?
They are nearly straight lines
What is the characteristic of the marginal ridges of the mandibular first premolar?
They converge lingually
What is the characteristic of the occlusal margin of the mandibular 1st premolar?
The lingual cusp is shorter by 1/3 length of the crown
On the proximal aspect of the mandibular second premolar, where is the height of contour located?
At the junction of the cervical and middle 1/3 on the buccal side
What is the orientation of the buccal triangular ridge in relation to the root of the mandibular 1st premolar?
Centered over the root
What is the characteristic feature of the root of the mandibular second premolar?
It is smooth and flat with a deep developmental groove
What is the shape of the crown of the mandibular 1st premolar in the mesial view?
Rhomboid
What is the characteristic of the marginal ridges of the mandibular 1st premolar?
The distal marginal ridge is more occlusal than the mesial marginal ridge
What is the location of the mesiolingual developmental groove of the mandibular 1st premolar?
At the junction of the lingual and mesial surfaces
What is the characteristic of the proximal surface anatomy of the mandibular 1st premolar?
M & D surfaces are convex and smooth except for a concave area cervical to the contact area
What is the characteristic of the lingual aspect of the mandibular 2nd premolar with 2 lingual cusps?
The ML cusp is larger than the DL cusp
What is the characteristic of the crown shape of the mandibular 1st premolar?
It tapers to the lingual side
What is the characteristic of the marginal ridges of the mandibular 2nd premolar?
The mesial marginal ridge is more occlusal than the distal marginal ridge
What is the characteristic of the occlusal surface of the mandibular 1st premolar?
Most of the occlusal surface can be seen from the lingual aspect
What is the characteristic of the cusp size and shape of the mandibular 1st premolar?
The lingual cusp is small and pointed
What is the characteristic of the convergence of the mandibular 1st premolar?
The crown converges to the lingual side
What is the characteristic shape of the cervical line of the mandibular 2nd premolar?
More flat
On which cusp ridge are notches often seen in the mandibular 2nd premolar?
Distobuccal cusp ridge
What is the characteristic feature of the crown shape of the mandibular 1st premolar?
Trapizoidal
Where is the contact area located on the mandibular 2nd premolar?
More cervical than the mesial contact area
What is the characteristic of the buccal cusp of the mandibular 2nd premolar compared to the 1st premolar?
It is less pointed
What is the characteristic of the marginal ridges of the mandibular 1st premolar?
They are more rounded
What is the characteristic of the occlusal morphology of the mandibular 1st and 2nd premolars?
Both premolars have a different morphology
What is the characteristic of the fossae in the occlusal aspect of the mandibular 1st premolar?
They are more shallow
What is the characteristic of the ridges in the mandibular 2nd premolar?
They are more sloping
What is the characteristic of the convergency of the crown shape of the mandibular 1st premolar?
It is more convergent
Study Notes
Mandibular Premolars: Key Features and Characteristics
Crown Shape
- Mandibular 1st premolar: Crown tapers (converges) to the lingual (narrower on lingual side than buccal)
- Mandibular 2nd premolar:
- With 1 lingual cusp: Crown tapers to lingual
- With 2 lingual cusps: Crown is as wide or wider mesiodistally than the buccal
Cusp Size and Shape
- Mandibular 1st premolar:
- Lingual cusp is small and pointed
- Most of the occlusal surface can be seen from this aspect
- Mandibular 2nd premolar:
- With 1 lingual cusp: Lingual cusp is smaller than buccal cusp, but larger than lingual cusp of 1st premolar
- With 2 lingual cusps:
- ML cusp is larger than the DL cusp
- Lingual groove between ML and DL cusps, and onto the lingual crown surface
Marginal Ridges
- Mandibular 1st premolar:
- Mesial marginal ridge (MMR) is more apical than the distal marginal ridge
- Only tooth in the mouth where the mesial marginal ridge is more apical than the distal marginal ridge
- Mandibular 2nd premolar:
- Mesial marginal ridge (MMR) is more occlusal than the distal marginal ridge (as found in all other teeth)
Occlusal Aspect
- Mandibular 1st premolar:
- Outline: Mesial and distal marginal ridges may converge lingually
- Ridges, Fossae, Grooves:
- Due to size of cusp, the buccal triangular ridge is long
- Joins the shorter lingual triangular ridge
- Often may meet smoothly and form a uninterrupted transverse ridge
- Fossae:
- Possess a mesial and distal fossa
- Both are irregular or circular, not triangular
- Both possess pits
- Distal fossa is usually larger and/or deeper
2nd Premolar Variations
- Two-cusp version:
- Crown is round or oval shaped with a square occlusal table
- There is slightly more bulk in the mesial half buccolingually than in the distal half
- Ridges, Fossae, Grooves:
- Lingual cusp smaller than buccal cusp
- Possess more supplemental grooves than first premolars
- Also has a smaller triangular ridge
- Groove:
- Possess a curved central groove with no lingual groove
- This groove can be fairly straight
- Three-cusp version:
- When lingual cusps are large, the occlusal surface is broader on the lingual
- Often have greater bulk buccolingually in the distal not the mesial
- Ridges, Fossae, Grooves:
- Possess three triangular ridges converging toward the central fossa
- There is no transverse ridge
- Central fossa (unique) shifted towards the distal
- Lacks a central groove
- Mesial groove present
- Lingual groove:
- Separates the two lingual cusps
- Completes the Y-shaped occlusal groove pattern
Proximal Aspect
- Mandibular 1st premolar:
- Mesial View:
- Proximal aspects have Mesial Rhomboid shape
- With narrow occlusal table and prominent lingual inclination
- Distal Aspect:
- Outlines of proximal aspects
- Buccal outline is convex with maximum convexity at C 1/3 representing cervical ridge
- Lingual outline is convex with maximum convexity at middle 1/3
- Cervical line curves occlusally and less curved distally
- Occlusal margin:
- The two cusps are not on the same level
- The lingual cusp is shorter by 1/3 length of crown
- The buccal cusp is centered over the root
- This is due to the prominent lingual inclination
- The lingual cusp tip is in line with lingual border of the root
- Mesial Marginal Ridge (MMR) and Distal Marginal Ridge (DMR):
- Inclined from B to L surface, parallel to B cusp ridge
- Straight and at right angle to the axis of the tooth
- DMR is more occlusal than MMR (unique characteristic of this tooth)
- Proximal surface anatomy:
- M & D surfaces are smooth and convex, except for a concave area cervical to contact area
- Mesio Lingual developmental groove present at the junction of Lingual and Mesial surfaces
- Mesial View:
Root Depressions
- Mandibular 2nd premolar:
- Have a distal root depression in the middle third of the root
- NO mesial depression
Distinguishing Characteristics
-
Generally speaking:
- The mandibular 1st premolar has a longer crown and a shorter root than the 2nd premolar
- The mandibular 1st premolar is longer overall than the 2nd### Mandibular 2nd Premolar
-
Root has a distal depression in the middle third, but no mesial depression
-
Mesial surface of root is more convex
-
Root surface is smooth and flat with a deep developmental groove
-
Proximal aspect: height of contour is at the junction of the cervical and middle 1/3 on the buccal side and middle 1/3 on the lingual side
-
Distolingual cusp is smaller, so more of the occlusal surface is seen from the distal aspect
Mandibular 1st Premolar
- Occlusal aspect: outline is not symmetrical, more bulky on the distal side
- Mesiolingual corner appears as if it has been pushed inward
- Tip of the buccal cusp is near the center from the occlusal view
- Lacks a prominent buccal ridge
- Cusp ridges are nearly straight lines
- Crown is somewhat diamond-shaped, converging lingually
- Shape of the crown is asymmetrical
- Mesiolingual groove is frequently seen only on the mandibular 1st premolar
- Crown tilts more lingually than the mandibular 2nd premolar
Proximal Aspect of Mandibular Premolars
- Crown shape is rhomboid
- Crowns of both premolars tilt lingually
- Proximal aspects have a mesial rhomboid shape with a narrow occlusal table and prominent lingual inclination
- Distal aspect outlines: mesial and distal aspects have different outlines
- Mesial aspect: buccal outline is convex with maximum convexity at the cervical 1/3
- Lingual outline is convex with maximum convexity at the middle 1/3
- Cervical line curves occlusally and less curved distally
Mesial and Distal Aspects
- Occlusal margin: two cusps are not on the same level, lingual cusp is shorter by 1/3 length of the crown
- Buccal cusp is centered over the root due to the prominent lingual inclination
- Lingual cusp tip is in line with the lingual border of the root
- Mesial marginal ridge (MMR) is inclined from buccal to lingual surface, parallel to the buccal cusp ridge
- Distal marginal ridge (DMR) is straight and at right angle to the axis of the tooth, more occlusal than MMR
Proximal Surface Anatomy
- Mesio-lingual developmental groove is present at the junction of lingual and mesial surfaces
- M & D surfaces are smooth and convex, except for a concave area cervical to the contact area
Lingual Aspect of Mandibular Premolars
- Crown shape: mandibular first premolar crown tapers (converges) to the lingual (narrower on the lingual side than the buccal)
- Mandibular 2nd premolar: crown tapers to the lingual, or is as wide or wider mesiodistally than the buccal
- Lingual cusp size and shape:
- Mandibular 1st premolar: lingual cusp is small and pointed
- Mandibular 2nd premolar with 1 lingual cusp: lingual cusp is smaller than the buccal cusp, but larger than the lingual cusp of the 1st premolar
- Mandibular 2nd premolar with 2 lingual cusps: ML cusp is larger than the DL cusp, with the lingual groove between them and onto the lingual crown surface
- Marginal ridges:
- Mandibular 1st premolar: mesial marginal ridge is more apical than the distal marginal ridge
- Mandibular 2nd premolar: mesial marginal ridge is more occlusal than the distal marginal ridge
Learn about the characteristics of the occlusal surface of the mandibular second premolar, including the three-cusp version, ridges, fossae, and grooves. Understand the differences between the mesial and distal aspects.
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