Anatomy of Permanent Posterior Teeth W3 Flashcards
How do you tell the difference between an upper premolar (1,4) and upper second premolar (1,5)?
- The 1,4 has 2 roots compared to the 1,5 with 1 root with vertical grooves on mesial and distal surface.
- The occlusal view of 1,5 is rounder and less kite shaped than the 1,4.
- Buccal ridge is more convex in 1,4 than 1,5
- 1,4 has a distinct central developmental groove that crosses mesial marginal ridge and extends on to mesial surface.
- 1,5 has less distinct central developmental groove. 1,5 has supplementary grooves- more wrinklier in appearance. Has transverse ridge from buccal and palatal cusp.
- Buccal cusp tip of 1,4 is displaced distally, which means the mesial slope of the cusp is longer than the distal. = long mesial ridge. Whereas, 1,5 has short mesial cusp slope.
- Buccal cusp bigger than palatal cusp of 1,4. (Can see buccal cusp from palatal view). Whereas 1,5 cusps are same height (palatal cusp is bigger than 1,4).
- Cusps of 1,4 are closer together than 1,5 (further apart).
- Mesial aspect of 1,4 has mesial marginal ridge and mesial developmental depression (canine fossa). Whereas 1,5 has no mesial depression and no mesial developmental groove.
- Both have smaller crowns than canine.
How can you tell whether an upper second premolar is left or right?
The palatal cusp tip will be display slightly medially.
Where is the cusp of carabelli found, if present?
Mesiopalatal cusp of maxillary first molars.
How many cusps does the lower first permanent molar (3,6) have, and which is the smallest and biggest cusp?
5 cusps with the distal buccal cusp being the smallest. Biggest is mesial buccal cusp
Which permanent posterior teeth can be congenitally missing?
1st maxillary premolar (1,4) and 3rd permanent molars MX and MN
Describe differences between maxillary first molar (1,6) and the mandibular first molar (3,6)
MX:
- 3 roots compared to MN x2.
- x4 cusps compared to MN x5
- Largest cusp is mesial palatal cusp. Followed by large Mesial buccal cusp. Smallest cusp is distal palatal cusp.
- Cusp of carabelli may be present on MP cusp.
- Occlusal: oblique ridge DB→MP cusp. Mesial area larger than distal area.
- Occlusolingual fissure- between 2 palatal cusps.
- Distinct x5 developmental grooves * transverse groove of oblique ridge.
- x4 fossas- x2 major, x2 minor
MN:
- x5 cusps - x3 B, x2 P.
- x2 roots M→D orientation.
- Biggest tooth.
- MB cusp largest, compared to MP cusp in MX.
- Occlusal developmental grooves = Lingual main.
- Palatal cusps are more pointed than Buccal
- Cruciate fissure pattern- from central fossa
- x3 fossas- mesial triangular
List the differences between the primary molars and permanent molars
- Primary molars are predecessors of premolars, but morphologically more similar to permanent molars.
- They are constricted in cervical region (bulge)
- Roots are longer in relation to crowns, slender and more flared than permanent.
- Pulpal horns and chambers are higher and larger in primary.
- Enamel is thinner and more consistent in thickness in primary.
Which tooth has 5 cusps?
Mandibular First Molars (3,6)
What is the descending order of cusp sizes in upper first permanent molar and its FDI?
1,6
mesiopalatal, mesiobuccal, distobuccal, distopalatal
Name at least two typical morphological characteristics of the mandibular first from mandibular second PREMOLARS
1st:
- small, afunctional - more triangular shape
- Bicuspid: B cusp is significantly higher than P.
- Mesiolingual developmental groove- occlusal surface onto palatal surface (mesial side)
- Transverse ridge. From buccal cusp tips to palatal cusp tip.
- x2 Fossas- on either side of transverse ridge.
- Mesial marginal ridge from ML developmental groove onto MP surface.
- Distal marginal ridge higher than mesial
2nd:
- Possible 3 cusps- Buccal cusps shorter than 4,4. Palatal cusp longer and more developed than 4,4.
- Lingual developmental groove if there are 2 palatal cusps. Afunctional P cusps
- More supplementary grooves than 4,4.
- Well defined triangular buccal ridge-
- Can have three fissure types: Y is most common, then H then U.
- Distal marginal ridge is lower than mesial- so can see mesial side.
What is the observable difference between MX and MN premolar roots?
What is the difference in MX and MN permanent roots?
MX 1,4 has 2 roots.
Generally, MN roots are narrower M→D than MX.
Permanent
MX root orientation = buccal and palatal
MN root orientation = mesial and distal
How would you describe premolars?
- Bicuspid (3,5 may have x3 cusps)
- Transition between canines and molars
- Replace primary molars
- 4 in MX and 4 in MN
- MX 1,4 has x2 roots, compared to other premolars with a single root.
- Aid in holding or grasping food (buccal cusp pointy), grinding (lingual cusp flat)
What are the typical features of the 1,4? What is the name of this tooth?
Maxillary Upper Right 1st Premolar
- Tip of buccal cusp is distal to midline- separates border into long straight mesial ridge with shorter rounded distal ridge (all other molars, the mesial ridge is shorter than distal).
- Kite Shaped - buccal cusp bigger than palatal
- Mesiobuccal developmental groove- canine fossa.
What is a fissure?
The name for the narrow crevice that may be present at the base of a groove.
What is the red arrow indicating?
Draw an occlusal view of the mandibular permanent 1st molar. Indicating its typical features and FDI.
- FDI= 3,6 4,6
- Oblong crown, longer from M→D than B→P
- x5 cusps (MB is largest) D palatal is smallest.
- Palatal cusps more pointed than buccal.
- Cusps are separated by y shaped fissure - radiating from central fossa.
- Developmental grooves travel over occlusal onto buccal and palatal aspect- lingual developmental groove.
- x3 fossas- mesial triangular, central and distal
Identify this tooth
- Mandibular Second Permanent Molar - (3,7 4,7)
- Mesial palatal cusp higher than buccal
- x4 cusps- distal buccal smallest.
- Roots are less splayed than 3,6.
- Cruciate fissure pattern
- One buccal groove on MN - can end in pit
- Palatal groove
Identify this tooth
Mandibular 1st Molar (3,6 4,6)
- Palatal aspect because Buccal aspect has 3 visible cusps
- x5 cusps total
- Roots are more splayed than 2nd molar
- Lingual cusps are higher than buccal cups
- Crown tapered palatal view
- Cruciate fissure pattern
Identify each of these molars in their occlusal view:
- 1st MN has x3 buccal cusps
- 1 and 2 have cruciate fissure pattern
- 3rd is like strawberry
From the occlusal view, determine which molar this is and its typical features.
Maxillary 1st Molar- .
- Rectangular, rhomboid shape
- Largest of the Mx molars
- Mesiopalatal cusp biggest (carabelli will be present here)
- Mesial buccal cusp is broad
- Oblique ridge- DB→ to MP (divides tooth into larger mesial area vs smaller distal area)
- From central developmental groove- buccal and palatal grooves extend onto the surfaces.
- x4 fossas- mesial and distal triangular, central and distal main
