Deciduous Teeth Morphology II Quiz

Deciduous Molars Morphology

• Deciduous first molars are smaller than the deciduous second molar, unlike permanent teeth.
• Deciduous first molars have a unique shape and do not resemble any other tooth.

Maxillary First Molar (D)

• The crown does not resemble any other primary or permanent molar crown, but has similarities to permanent premolars.
• The buccal surface has:
  • Mesiodistal (MD) dimension much greater than the crown height
  • Curvature of the CL, greater towards the mesial than the distal, making the crown appear offset towards the mesial
  • A prominent cervical ridge, especially the mesial portion (Prominent MB cervical bulge)
• The occlusal surface:
  • Exhibits some similarity to maxillary premolars
  • Has a general shape of an unusual five-sided figure
  • The crown outline converges lingually and distally
• There are four cusps:
  • ML cusp (bulkiest and longest)
  • DL cusp (smallest, and sometimes absent)
  • MB cusp is of greater proportions than the DB cusp
• The transverse ridge is very prominent (ML & MB)
• There is a well-defined central fossa, mesial and distal triangular fossae

Maxillary Second Molar (E)

• Resembles the maxillary permanent first molar in appearance
• Larger than the first maxillary deciduous molar
• Has a fifth cusp (cusp of Carabelli)

Mandibular First Molar (D)

• Does not resemble any other teeth, deciduous or permanent
• Has 4 cusps
• Has 2 roots like other mandibular molars
• Prominent MB cervical bulge
• The occlusal surface:
  • The crown is wider MD than BL
  • Somewhat rectangular in shape
  • The four cusps, from largest to smallest in size, are (MB > ML > DB > DL)
  • The two mesial cusps are considerably larger than the distal cusps
  • Transverse ridge (ML & MB)
  • Central fossa, mesial and distal triangular fossae

Mandibular Second Molar (E)

• Resembles the mandibular permanent first molar in appearance
• Has 5 cusps
• Can be differentiated from the permanent first molar by:
  • General differences between deciduous and permanent teeth
  • The three cusps on the buccal surface of the deciduous first molar are of nearly equal size
  • The occlusal table is narrower BL and less pentagonal than the permanent first molar
  • The M root is longer and wider than the D root in the deciduous tooth

Clinical Considerations

• The thickness of enamel and dentin in primary teeth is less than in permanent teeth, making the pulp chamber close to the external surface
• Understanding tooth morphology is important for restoration and identification
• The prominent cervical ridge must be considered in crown preparation
• The roots of deciduous molars flare more than permanent teeth, requiring more caution during extraction
• Premature loss of deciduous molars can lead to malocclusion and space maintenance is crucial