2. General Information
Six mandibular molars
Three in each quadrant
Named for position in the arch, e.g. first, second and third molar
Mandibular first molar is first permanent tooth to erupt
Its positioning in the arch is important for the appropriate
alignment of other permanent teeth
Considered the “keystone” of the dental arch
Roots are bifurcated
4. Mandibular First Molar Characteristics
Universal Number: R-#30 L-#19
Eruption Date: 6-7 years
First Evidence of Calcification: birth
Crown Completion: 2 ½ - 3 years
Root Completion: 9-10 years
5. Mandibular First Molar Characteristics
Function: mastication and comminution
Length of Crown: 7.5mm
Length of Root: 14mm
Antagonists: Maxillary second premolar and first
molar
6. Mandibular First Molar
Identifying Features
Five cusps: mesiobuccal, distobuccal, distal, mesiolingual,
distolingual
Mesial and distal roots
Three pulp canals
Two in mesial root, one in distal root
Largest mandibular tooth
First permanent tooth to erupt
8. Mandibular First Molar
Buccal Surface View
Three flat buccal cusps in size order
Mesiobuccal, distobuccal, and distal
Divided by grooves
Concave mesial side with the contact area in the occlusal third
Straight distal side with a more occlusal contact area than the mesial
Mesial root curves mesially for half length, then distally
Distal root is less curved, with axis in distal direction
Root bifurcates about 3 mm below cervical line
Has deep developmental depression
9. Mandibular First Molar
Lingual Surface view
Two pointed lingual cusps
Mesiolingual and distolingual
Visible distal cusp divided by a lingual groove
Deep developmental depression at root bifurcation
10. Mesial Surface
Two visible cusps
Mesiobuccal and mesiolingual
Mesial marginal ridge about 1mm below cusp tips
Cervical line curves occlusally about 1mm
Concave area at cervical line that continues onto root
Only mesial root is visible
Mesial root usually has two pulp canals
Broad and straight root, tapering in apical third
Broad concavity or depression on root
11. Distal Surface
Tooth converges toward distal so that some of buccal
surface is visible
Crown is shorter on distal so all cusps seen
Cervical line is relatively straight
Shallow depression often evident on root
12. Occlusal Surface
Wider by 1mm from distal to mesial than from
buccal to lingual
Five functioning cusps in order of size
Mesiolingual, mesiobuccal, distolingual, distobuccal, and
distal
Central, mesiobuccal, distobuccal, and lingual (Y-
shape) grooves
Central (circular), mesial, and distal triangular are
the major fossae
Pits located central, mesial and distal
14. Mandibular Second Molar
Universal Number: R-#31 L-#18
Eruption Date: 11-13 years
First Evidence of Calcification: 2½-3 years
Crown Completion: 7 – 8 years
Root Completion: 14 - 15 years
15. Mandibular Second Molar
Function: mastication and comminution
Length of Crown: 7mm
Length of Root: 13mm
Antagonists: maxillary first and second
molars
16. Mandibular Second Molar Identifying
Features
Four cusps: mesiobuccal, distobuccal, mesiolingual,
distolingual
Two roots: mesial and distal
Two pulp canals: one in each root
18. Mandibular Second Molar Variations from
First Molar
The mandibular second molar varies from the first molar
It’s smaller
There are only 4 cusps
The buccal groove divides the 2 buccal cusps
The lingual groove divides the two lingual cusps
The mesial side is wider; only one pulp canal
The occlusal has more supplementary grooves
19. Mandibular First and Second Molars
Mandibular first molar has five cusps (3 buccal, 2 lingual)
Mandibular second molars have four cusps (2 buccal, 2 lingual)
Mandibular Molars have two roots, one mesial and one distal
Maxillary molars have three roots, two buccal one lingual
All teeth have one pulp canal in each root, but the mandibular first
molar is often an exception
There are three pulp canals in the two roots: the mesial root has two pulp
canals, and the distal root has one
The mandibular second molar has only on pulp canal in each root
21. General Information
Both maxillary and mandibular third molars
show considerable developmental variation
No standard structural description
Most likely tooth to have anomalies
Often crown displacement and
fused/malformed roots
22. Mandibular Third Molar
Universal Number: 17, 32
Eruption Date: 17-21 years old
First Evidence of Calcification: 8-10 years old
Crown Completion: 12-16 years old
Root Completion: 18-25 years old
23. Mandibular Third Molar
Function: mastication and comminution
Length of Crown: 7mm
Length of Root:11mm
Antagonists: Maxillary second and third
molar
25. Mandibular Third Molar
Clinical Considerations
Often crowns do not conform to normal size
Often have fused roots
When well-developed, will look like first or second molar
Frequently, the maxillary third molar is heart-shaped, where
the mandibular third molar is often atypical.
