By kyrillos gad

General Features of Premolars

• There are eight premolars, four in each dental arch, two in each quadrant.
• Premolars are situated between canines and first molars.
• They are called bicuspids because each has two cusps.
• Premolars develop from four lobes (3 buccally and 1 lingually), except for the lower second premolar which has three cusps and develops from five lobes.

Marginal Ridges

• Marginal ridges of premolars are in a horizontal plane, related to the occlusal surface of the crown.
• In maxillary premolars, the first premolar is larger than the second premolar.
• In mandibular premolars, the first premolar is smaller than the second premolar.

Posterior Teeth vs. Anterior Teeth

• Posterior teeth have greater buccolingual dimension.
• Crowns of posterior teeth are shorter cervico-occlusally.
• They have larger contact areas which are nearly at the same level.
• They have less curvature of the cervical line from all aspects.

Maxillary First Premolar

• Chronology:
  • Appearance of enamel organ: 7 months IUL
  • First evidence of calcification: 1 1/2-1 3/4 years
  • Crown completed: 5-6 years
  • Eruption: 10-11 years
  • Root completed: 13 years
• The maxillary first premolar has two sharp, well-developed cusps.
• About 80% have two roots (one buccal and one lingual) and 20% have one root.
• Whether double or single rooted, the maxillary first premolar has two root canals.

Morphology of Maxillary First Premolar

• Buccal surface:
  • Roughly trapezoidal with the short side cervically and the long side occlusally.
  • Convex with maximum convexity at the cervical third.
  • Mesial slope of the buccal cusp is longer than the distal slope.
• Lingual surface:
  • Narrower than the buccal surface.
  • Lingual cusp is shorter than the buccal cusp with a pointed tip.
  • Maximum convexity is located at the middle third.
• Mesial surface:
  • Trapezoidal in shape with the short side occlusally and the long side cervically.
  • Convex from the cervical line to the tip of the buccal cusp.
• Distal surface:
  • Cervical line is nearly straight.
  • Bifurcation is near the apical third of the root.
• Occlusal surface:
  • Hexagonal in shape.
  • Central developmental groove divides the occlusal surface evenly buccolingually.

Pulp Cavity of Maxillary First Premolar

• Mesiodistal section: narrow pulp chamber and narrow root canal.
• Buccolingual section: pulp chamber is wider buccolingually with two pulp horns, the buccal one being usually longer.
• In mid-root cross section: two canals appear rounded and constricted, with the lingual one slightly larger.

Maxillary Second Premolar

• Chronology:
  • Appearance of enamel organ: 8 months IUL
  • First evidence of calcification: 2-2 1/4 years
  • Crown completed: 6-7 years
  • Eruption: 10-12 years
  • Root completed: 13-15 years
• The maxillary second premolar resembles the maxillary first premolar but is smaller in size.
• The crown is rounded from all aspects, with no developmental groove crossing the mesial marginal ridge.
• Occlusal surface is rounded or oval with a short central developmental groove and multiple supplemental grooves.

Pulp Cavity of Maxillary Second Premolar

• Mesiodistal section: narrow pulp chamber that extends apical to the cervical line, then becomes constricted and tapers as a root canal to the apex of the root.
• Buccolingual section: pulp chamber and root canal are rather wide buccolingually.

This quiz covers the general features of premolars, including their number, location, and development. It also touches on their relation to canines and molars.