Mandibular first premolars #21 and #28

Permanent mandibular first premolars

21 and 28

First evidence of calcification for mand first premolars

1.75-2 years

Eruption for mand first premolars

10-12 years

Completion of root for mand first premolars

12-13 years

Buccal view for mand first premolars

• no imbrication lines

• Buccal cusp long and sharp

• Very large buccal cusp

• very small lingual cusp

Lingual view for mand first premolars

• lingual cusp is small

• Transverse ridge

• Mesiolingual groove

• 45 degree angle to long axis of the tooth when you connect the buccal cusp and lingual cusp from a proximal view

Transverse ridge

Formed by union of the triangular ridge of the buccal cusp and the triangular ridge of the lingual cusp

• Buccal cusp ridge of lingual cusp (lingual triangular ridge)

• Lingual cusp ridge of buccal cusp (buccal triangular ridge)

Mesiolingual groove

development groove that separates the mesial marginal ridge from the small lingual cusp

Proximal view of first premolar

• mesiolingual groove can again be seen (helps distinguish right from left)

• Deeper Mesial CEJ curvature (R/L)

• buccal outline is longer than lingual outline

Occlusal view of mand first premolar

• Both cusps and transverse ridge are offset to mesial (Help distinguish R/L)

• The prominent transverse ridge typically separated the mesial and distal fossae. A continuous central developmental groove is usually absent

• Mesial fossa has a mesial pit within

• Distal fossa has a distal pit within

Root of mand first premolar

• Single root

• root is smaller and shorter than a mandibular second pm

• root may have a slight distal angulation