Dental Anatomy: Maxillary Second Molar

Maxillary Second Molar

• 7th from the midline
• 5th cusp is less evident
• Roots are less divergent and less separated
• Both distal cusps are less developed
• The crown is smaller in overall dimensions compared to 1st molar
• Crown is shorter and narrower mesiodistally (MD) than 1st molar
• MB is widest than DB (MD > OC)
• DB cusp is smallest (apart from distal aspect seen)
• Buccal groove is more distally located than 1st molar
• MB root tip is in line with buccal groove

Roots

• Three roots are seen from the buccal aspect
• Root trunk is larger than the 1st molar
• Roots are less diverged, nearly parallel to each other, and distally curved
• A deep developmental groove is present

Palatal Aspect

• Lingual convergence
• MP cusp is largest
• DB cusp is small, smooth, and spheroid
• DB cusp can be seen
• The lingual developmental groove is more distally located
• No Carabelli cusp

Palatal Aspect (continued)

• The roots are seen
• The apex of palatal root is in line with the lingual developmental groove
• Developmental depression on the root surface
• The DL cusp is smaller, and part of DB cusp is seen distal of DL cusp

Mesial Aspect

• Similar to the 1st molar
• Roots are less diverged
• Not widely apart
• Less crown length
• The P and MB roots are within the confines of the BL outline of the crown

Distal Aspect

• The distobuccal cusp is smaller
• More of the MB cusp is seen
• The apex of the palatal root is in line with the distopalatal cusp
• ML cusp of 2nd molar is not seen

Mesial and Distal Aspect

• Like 1st molar except shorter Occlusi-Cervical dimension
• Buccal crest of curvature at cervical third
• Lingual crest of curvature at middle third
• Mesial crest of curvature at junction of occlusal-middle
• Distal crest of curvature slightly more cervical

Occlusal Aspect

• Geometrical outline: more rhomboidal
• BP dimension is greater than the MD dimension
• The crown tapers distally and lingually
• Elevations: 4 cusps and 4 fossae
• Fossa: Oblique ridge
• Marginal ridge: strong and well developed
• Distal marginal ridge is shorter and at a lower level

How to Tell First from Second Molar

• Narrower M-D with second molar
• Both the crown and root are slightly smaller
• The 1st molar is broader than the 2nd molar
• The occlusal surface has more supplementary grooves
• There is no transverse groove of the oblique ridge
• The MB and DB roots are less curved distally in the apical on the 2nd molar and bent towards distally
• The buccal groove is extended and at the end of the groove is the buccal pit in the 1st molar
• Occlusal view of the first is less rhomboidal than the second
• Cusp of Carabelli only on the first
• The roots are not as divergent; they are closer together
• MB root apex is in line with MB cusp tip within the first molar, while in line with the buccal groove in the second molar

Maxillary Third Molar

General Characteristics

• Triangular occlusal outline
• DL cusp is often absent
• Still wider BL than MD
• Roots are shorter, convergent, often fused, and 3 in number
• The ML cusp is the largest
• The crown is shorter cervical line to marginal
• The lingual cusp is well developed and larger than the 2nd

Buccal Aspect

• The MB cusp is wider and longer than the DB cusp
• The roots are often fused, making one large short root

Lingual Aspect

• Usually one large lingual cusp without lingual groove

Mesial Aspect

• Fusion of the roots and the bifurcation in the apical 1/3

Distal Aspect

• Convex surface and the distal surface is short and narrow
• Most of the occlusal surface is seen

Occlusal Variations of 3rd Molar

• Heart-shaped type with three cusps (most common)
• Rhomboidal shape with four cusps
• One cusp type: peg shape
• Congenitally missing

How to Distinguish a Third Molar

• Roots are much shorter than the 1st and 2nd molar
• Roots are shorter than any other tooth (other than mandibular 3rds)
• Roots usually fused
• More supplemental occlusal grooves
• Heart-shape occlusal outline, narrower occlusal table
• MB root larger than DB root
• MB prominence of facial surface
• DLG, if present
• Contact area wear facet only on the mesial