Characteristics of Mandibular 2nd Premolars

Three cusp type of mandibular 2nd premolars

Most common form of mandibular second premolar.

Two cusp type of mandibular 2nd premolars

Less common form with single lingual cusp.

Single root of mandibular 2nd premolars

Larger and longer than first premolar's root, more blunted apex

Buccal cusp of mandibular 2nd premolars

Shorter and more rounded than first premolar.

Meaial/Distal contact areas of mandibular 2nd premolars

Broad at junction of occlusal and middle thirds.

Lingual groove of mandibular 2nd premolars

Divides mesiolingual and distolingual cusps.

Mesial Lingual Cusp of mandibular 2nd premolars

Longer than Distal Lingual cusp

Lingual Lobe of mandibular 2nd premolars

Greater so it makes cusps longer and less occlusal surface is seen

Developmental lobes of mandibular 2nd premolar

Four developmental lobes in two-cusp type 45%

five developmental lobes in three-cusp type 55%

Cusp tip of mandibular 2nd premolars

Located facial to long axis of root whearas first pm is aligned with it

Mesial Marginal Ridge of mandibular 2nd premolars

Located 90 degres to the long axis of tooth whereas first pm slopes lingual relative to horizontal plane

Visibility of occlusal surface

Less on mandibular 2nd premolars than 1st

Marginal ridges of mandibular 2nd premolars

Distal ridge lower than mesial ridge.

Mesial View of Buccal cusp and tip mandibular 2nd premolars is

Shorter

Crown/root of mandibular 2nd premolar

Wider buccolingually least likely to have a depression on the mesial surface of the root

Square profile of mandibular 2nd premolar

Characteristic of three-cusp type premolar with larger occlusal table

Supplemental grooves

More prevalent in second premolars.

Central groove of mandibular 2nd premolar

Ends at mesial/distal fossae.

Central pit of mandibular 2nd premolar

Deep pit located toward distal area, Junction of the central groove and the lingual groove

Impaction

Occurs when second premolar is blocked from eruption.

Partial anodontia

Condition where second premolars may be congenitally missing.

Groove patterns

Includes 'H', 'U', and 'Y' shaped patterns.

H shaped groove pattern

more common straight central groove

U shaped groove pattern

curve central groove

Y shaped groove pattern

form by “V” shaped central groove and linear lingual groove

Cusp sizes of mandibular 2nd premolar

Mesiolingual cusp wider than distolingual cusp.

Eruption prevention

Caused by closure of arch leeway space.