Lecture Notes on Premolars

Overview of Premolars

• Premolars are intermediate teeth between canines and molars.
• They are named mesial to distal:
  • First Premolar: Closest to the canine.
  • Second Premolar: Closest to the molar.
• First Premolar: Similar to canines, sharp for ripping.
• Second Premolar: More flat for grinding, similar to molars.
• Eruption occurs around ages 10-12.
• Roots finish developing approximately 2.5 years post-eruption.

Terminology

• Often called bicuspids; however, mandibular second premolars can have three cusps.

Maxillary First Premolar

• Roots: Typically two roots, bifurcates farther apically than mandibular molars.
• Cusps: Two cusps, each with a pulp horn and root canal.
• **Characteristics: **
  • Longer mesial cusp slope than distal cusp slope.
  • Deep mesial crown concavity.
  • Buccal view resembles a canine, with a shorter crown.
  • Buccal cusp develops from three lobes; lingual cusp from one lobe.
  • Mesial cusp slope is longer than the distal cusp slope — exception to the general rule.
  • Mesial marginal groove present, absent on the distal side.
  • Mesial developmental depression exists on the crown, extending to the root.

Maxillary Second Premolar

• Variability: More anatomical variation than the first premolar.
• Usually one root, occasionally two, with about half having two root canals.
• Similarities to First Premolar:
  • Crown less angular, more rounded.
  • The lingual cusp is almost the same size as the buccal cusp.
  • Oval occlusal shape with a wrinkled appearance due to short central groove and numerous supplemental grooves.

Mandibular First Premolar

• Overview:
  • Smallest premolar, narrowest and shortest root.
  • Typically one root and one canal.
  • Prominent transverse ridge.
  • Only tooth with mesiolingual groove, unique MMR and DMR angle.
• Buccal and Lingual View:
  • Lingual cusp is much shorter and occlusal anatomy is visible.
• Proximal View:
  • Buccal cusp tip centered over the root's long axis.
  • Mesial marginal ridge curving cervically due to mesiolingual groove.

Mandibular Second Premolar

• Unique Features:
  • Can have three cusps (hence bicuspid is a misnomer).
  • Larger than first premolars, more molar-like.
  • Premolar most likely to have a central pit.
  • Typically one root and one canal.
• Buccal and Lingual View:
  • Shorter buccal cusp, taller lingual cusps.
  • Can have two lingual cusps, mesiolingual cusp larger.
• Proximal View:
  • Longer root than the first premolar with a blunted apex.
  • Crown points lingually more than the mandibular first premolar.
• Occlusal View:
  • Three-cusp type has a Y shape; two-cusp type has a crescent shape.
  • Central pit present due to intersection of grooves.

General Notes

• Mesial vs. Distal:
  • Mesial often has either a marginal groove or developmental depression.

Next Steps

• The next lecture will cover molars.