Crown and root morphology Flashcards
Describe appearance of incisors
- Flat incisal edge
- Convex buccal surface
- Concave palatal/lingual surface
- 1 root (curve of the root is usually distal) - rarely will have low bifurcation
Describe maxillary incisor crown
- Well developed cingulum
- Prominent marginal ridges
- Asymmetrical along long axis
Describe maxillary incisor root
- Triangle/round cross-section
- Wider on buccal surface
Describe mandibular incisor crown
- Poorly developed cingulum
- Almost no marginal ridges
- Symmetrical from mesial to distal
Describe mandibular incisor crown
- Flattened mesio-distally cross-section
- Long relative to crown
Upper central incisor crown:root ratio?
1:1 (shovel-shaped crown)
Describe appearance of upper central incisor
- Mesial corner is square
- Distal corner is rounded
- Distal crown bulges out from long axis
Describe appearance of upper lateral incisor
- Mesial corner is square
- Distal corner is square
- Distal crown bulges out from long axis
Crown:root ratio of upper lateral incisor
1:2
Describe appearance of lower central incisor
- Flatten roots are perpendicular to incisal edge
- Longitudinal groove on distal side is deeper
- Root tip may curve to distal (unreliable)
Describe appearance of upper lateral incisor
- Flattened roots are twisted to incisal edge (backward corner is distal edge)
- More fan-shaped than lower central incisor
Describe appearance of canines
- Pointy incisal edge
- Convex buccal surface
- Slightly concave or convex palatal/lingual surface
- 1 root - may have low bifurcation
- If no incisal wear; distal slope of incisal edge is longer than mesial slope
How many roots of maxillary canine?
1 root
Appearance of root of canine
- Long relative to crown
- Egg-shaped cross-section
Describe crown of maxillary canine
- Incisal edge portion of crown about 1/3 of crown
- Very large cingulum
- Palatal cusp ridge (usually)
- Prominent marginal ridges
Describe buccal view of maxillary canine
Bulges out more from the root than mandibular
Describe proximal view of maxillary canine
Crown is straight or leans to buccal side.
Crown is an equilateral triangle.
How many roots of maxillary canine?
1 root (rarely 2)
Describe root of mandibular canine
- Long relative to crown
- Oval-round cross-section
Describe crown of mandibular canine
- Incisal edge portion occupies 1/5 of crown
- Smaller cingulum
- Less prominent marginal ridges
Describe buccal view of mandibular canine
Crown continues in relatively straight line from root
Describe proximal view of mandibular canine
Crown leans to lingual.
Crown is a scalene triangle
Describe upper canine appearance
- Distal slope of incisal edge is longer
- Crown bulges out more distally
Describe lower canine appearance
- Distal slope of incisal edge is longer
- Crown bulges out more distally
of cusps and roots of premolars
- 2 cusps (except for lower second premolars)
- 1 or 2 roots
Describe overall appearance of maxillary premolar
- Egg-shaped crown cross-section (oval)
- Palatal cusp tip located closer to centre of crown than buccal cusp tips
- Palatal cusp = functional cusp
Describe overall appearance of mandibular premolar
- Round crown cross-section (circular)
- “Buccal inroll” - buccal cusp is closer to centre of tooth
- Buccal cusp = functional cusp
Describe crown of upper first premolar
- Canine fossa on mesial surface (bottom of crown and root)
- Buccal cusp is higher and wider (mesial to distal)
- Palatal cusp is more centrally located (may be closer to mesial side)
Describe roots of upper first premolar
- 2 well-developed roots (maybe 3)
- Bifurcation on lower apical half
Describe crown of upper second premolar
- No canine fossa
- Palatal cusp is towards mesial side of tooth and more centrally located
- Buccal cusp is higher and wider (mesial to distal)
Describe roots of upper second premolar
- 1 roots (maybe 2)
- Oval-flattened on mesio-distal
Describe crown of lower first premolar
- Lingual cusp is much smaller than buccal cusp
- (Occlusal view) mesio-lingual corner will be cut off
- Groove often crosses mesial marginal ridge
- Two fossae on occlusal. Distal fossa will be larger
Describe roots of lower first premolar
- 1 root (sometimes 2 roots)
- If 2 roots, low bifurcation (not as low as 5th)
Describe crown of lower second premolar
- Lingual and buccal cusps are similar sizes
- 1 or 2 lingual cusps
- 1 lingual cusp: Tip closest to mesial surface
- 2 lingual cusps: Taller cusp closer to mesial surface
Describe roots of lower second premolar
- 1 roots (rarely 2)
- If 2 roots, very low bifurcation (high risk in RCT)
Describe crown of maxillary molars
- 4 main cusps (may have cusp of Carabelli)
- Disto-palatal cusp is separated from other cusps by ridge and fissure - smallest cusp
- Mesial palatal cusp is largest
Describe roots of maxillary molars
- 3 roots: 2 buccal and 1 palatal (usual)
- Mesio-buccal: tear-drop shaped; points to palatal root
- Distal buccal: oval-shaped
- Palatal: circular, MP root “points” here
Describe crown of mandibular molars
- “Buccal inroll” on buccal surface
- Mesial cusps are higher
- Mesial root has deeper grooves
- Root tips MAY curve distally (unreliable)
Describe roots of mandibular molars
- Usually 2 roots - mesial and distal
- Distal root = bean-shaped
- Mesial root = hourglass shaped
Describe appearance of upper first molar
- Rhomboid occlusal outline (large disto-palatal cusp)
- May have cusp of Carabelli on mesio-palatal cusp
- Buccal cusps are equal height and width
- Buccal groove goes 1/2 down buccal surface
Describe appearance of upper second molar
- Trapezoid/square outline (small disto-palatal cusp)
- Mesio-buccal cusp is larger than disto-buccal cusp
- Buccal groove goes 1/3 down buccal surface
Describe appearance of mandibular first molar
- Five cusps - 3 buccal and 2 lingual
- Not four square fissure pattern
Describe appearance of mandibular second molar
- Four square fissure pattern
Describe features of upper first premolar occlusal surface
- Egg-shaped
- Central fissure
- Mesial and distal marginal ridges
- Developmental groove - Over mesial marginal ridge
- Buccal cusp - Wider; tip towards buccal surface
- Palatal cusp - Narrower; tip towards tooth centre
Describe features of upper second premolar occlusal surface
- Egg-shaped
- Central fissure
- Mesial and distal marginal ridges
- Buccal cusp - Wider; tip towards buccal surface
- Palatal cusps - tip towards mesial side of tooth
Describe features of lower first premolar occlusal surface
- Round-shaped - mesio-lingual corner is cut-off
- Central fissure - curved towards lingual
- Mesial and distal marginal ridges
- Buccal cusp - much larger; tip towards tooth centre
- Lingual cusp - narrower
- Mesiolingual developmental groove
- Mesial fossa - smaller; contains developmental groove
- Distal fossa - larger
Describe features of lower second premolar occlusal surface
- Round-shaped
- Central fissure - curved slightly towards lingual
- Mesial and distal marginal ridges
- Lingual and buccal cusps are similar sizes
- 1 lingual cusp: tip closest to mesial surface
- 2 lingual cusps: mesiolingual cusp is larger. Lingual fissure between cusps
Occlusal outline of upper first molar
Rhomboid occlusal outline
Upper first molar may have?
Cusp of carabelli on palatal side of mesio-palatal cusp
Central fissure of upper first molar?
Zigzag pattern
Buccal fissure of upper first molar is where?
Halfway on buccal surface
Distopalatal fissure of upper first molar is?
Oblique towards distal fissure
Upper first molar has mesial and distal marginal ridges
True
Buccal cusps of upper first molar?
Buccal cusps are equal height and width. Tips towards buccal surface.
Which cusp of upper first molar is the largest?
Mesial palatal cusp
Which cusp of upper first molar is the smallest?
Disto-palatal cusp. This is separated from other cusps by oblique ridge and distopalatal fissure.
Distopalatal cusp is separated from other cusps by?
Oblique ridge and distopalatal fissure
Oblique ridge of upper first molar goes from?
Mesiopalatal cusp to distobuccal cusp
Mesial fossa of upper first molar is?
Larger than distal fossa; mesial to oblique ridge
Distal fossa of upper first molar is?
Narrower than mesial fossa; distal to oblique ridge
Occlusal outline of upper second molar?
Trapezoid/square outline
Central fissure of upper second molar?
Zigzag pattern
Buccal fissure of upper second molar stretches?
Towards distal surface; oblique
Distopalatal fissure of upper second molar?
Oblique towards distal surface
Upper second molar has mesial and distal marginal ridges
True
Describe buccal cusps of upper second molar?
Buccal cusps - Mesio-buccal cusp is larger; tips towards buccal surface
Largest cusp of upper second molar?
Mesial palatal cusp is largest, but smaller than 6s
Smallest cusp of upper second molar?
Disto-palatal cusp
Disto-palatal cusp of upper second molar is separated from other cusps by?
Oblique ridge and distopalatal fissure - smallest cusp
Oblique ridge of upper second molar?
From mesiopalatal cusp to distobuccal cusp
Mesial fossa of upper second molar?
Larger than distal fossa; mesial to oblique ridge
Distal fossa of upper second molar?
Narrow than mesial fossa; distal to oblique ridge
Occlusal outline of lower first molar?
Oval occlusal outline
Central fissure of lower first molar
Zigzag pattern
Buccal fissure of lower first molar?
2/5ths from mesial;oblique
Disto-buccal fissure of lower first molar?
4/5ths from mesial; oblique
Lingual fissure of lower first molar?
Halfway on lingual surface, straight
Lower first molar has mesial and distal marginal ridges
True
How many cusps of lower first molar?
5 cusps - 3 buccal and 2 lingual
Describe buccal cusps of lower first molar
Buccal cusps width decreases toward distal (mesiobuccal >distobuccal > distal). Tips towards tooth centre
Size of lingual cusps of lower first molar
Lingual cusps are equal sized. Tips towards lingual surface
Mesial fossa of lower first molar
Contains junction of central, buccal and lingual fissures
Distal fossa of lower first molar
Contains junction of central and disto-buccal fissures
Occlusal outline of lower second molar
Four-square fissure pattern
Central fissure of lower second molar
Straight line
Buccal fissure of lower second molar
Half-way on buccal surface, straight
Lingual fissure of lower second molar
Halfway on lingual surface, straight
Lower second molar has mesial and distal marginal ridges
True
Buccal cusps of lower second molar
Buccal cusps are equal sized. Tips towards tooth centre
Lingual cusps of lower second molar
Lingual cusps are equal sized. Tips towards lingual surface.
Central fossa of lower second molar
Contains junction of central, buccal, and lingual fissures