7 Questions
What is the shape of the Distal Marginal Ridge (DMR) in the distal aspect of the crown?
U-shape
Which root appears with a more pointed apex in the distal aspect?
Distal
What is the location of the distal contact area in relation to the distal cusp in the mesial aspect?
Below the cusp
Which crown measurement is described as larger than its thickness?
Mesiodistal (MD)
Which root is broader and longer in terms of the lingual border?
Mesial root
Which root shows a U-shape Distal Marginal Ridge (DMR) that is shorter and more cervically placed than its counterpart?
Distal root
Which aspect of the crown shows a geometric outline that is hexagonal in shape?
Occlusal aspect
Study Notes
Cervical Outline
- Irregular shape with dip into the root bifurcation
- Lingual aspect:
- Smooth and convex
- Max. convexity in middle 1/3 of crown
- Depressions: Lingual developmental groove separates the 2 lingual cusps
Roots
- Root trunk and roots appear narrower and longer than buccally due to lingual convergence and more occlusal position of the cervical line
- Deep depression on root trunk from bifurcation till cervical line
Buccal Aspect
- Geometric outline: Rhomboid due to lingual inclination
- Outline form:
- Buccal outline: Convex in cervical 1/3 (cervical ridge), flat in middle 1/3 and occlusal 1/3
- Lingual outline: Convex, max. convexity or crest of curvature in middle 1/3
- Occlusal outline: Formed by MLC and MBC
- MLC longer and more pointed than MBC
- Cervical line: Straight and slants occlusally from buccal to lingual side
- Anatomical landmarks:
- Mesial surface: Convex and smooth
- MMR: Long and concave buccolingually
- MCA: Junction of occlusal 1/3 and middle 1/3, centered B-L
Roots
- Mesial root: Broad B-L, blunt (flat) apex
- Mesial root outline:
- Buccal and lingual outlines: Straight till junction of cervical 1/3 and middle 1/3, then gently taper to the apex
- Deep developmental depression on the mesial surface of the root (2 root canals)
Buccal Aspect Anatomical Landmarks
- Buccal surface: Convex, max. convexity in cervical 1/3 (cervical ridge)
- Developmental grooves:
- MB developmental groove: Between MB and DB cusps, may have a pit at the end
- DB developmental groove: Between DB and D cusps, shorter than MB developmental groove
- MB developmental groove longer than DB developmental groove
Roots
- 2 roots: Mesial root (MR) and Distal root (DR)
- Axes of the roots: Inclined distally
- Widely divergent, nearly twice crown length, C/R=1/2
- Root trunk: About 3mm
- Deep developmental depression on root trunk
- Mesial root:
- Cervical 1/2 curved mesially
- Apical 1/2 curved distally
- Mesial outline: Convex
- Distal outline: Concave
- Longer than DR by 1mm
- Distal root: Straighter and less curved than MR
Lingual Aspect
- Lingual convergence: Lingual surface narrower than buccal surface
- Mesial outline: Straight till middle 1/3, then slightly convex till ML cusp tip
- Distal outline: Convex till contact area beneath the distal cusp ridge, then convex again till DC tip
- Occlusal outline: Formed by 2 lingual cusps (MLC and DLC)
- MLC slightly wider and longer than DLC
Distal Aspect
- Similar to mesial surface with the following differences:
- 5 cusps visible
- Crown: Shorter and narrower (distal convergence)
- DMR: U-shape, shorter and more cervically than MMR
- Distal contact area: Located below the distal cusp and more cervical than MCA
- 2 Roots appear in distal aspect
Distal Root
- More pointed apex
- Mesial root: Broader and longer
- Lingual border of mesial root
Occlusal Aspect
- Geometric outline: Hexagonal
- Crown measurements:
- MD (width) larger than BL (thickness)
- Crown converges lingually and distally (distolingual convergence)
- Buccal outline larger than lingual outline
- Mesial outline longer than distal outline
- Anatomical landmarks:
- 5 cusps with 5 triangular ridges
- Size: MBC > MLC > DLC > DBC > DC
- Height: MLC > DLC > MBC > DBC > DC
- Depressions:
- Fossae: 3 fossae, 1 major central fossa with a pit
Test your knowledge on dental anatomy and morphology with this quiz covering topics such as cervical outline, anatomical landmarks, crown convexity, lingual development groove, and root characteristics.
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