mandibular second premolar
TRANSCRIPT
Resembles the mand. first premolar -buccal aspect only
Assumes 2 common forms:
3 cusp type- angular 2 cusp type- more
roundedThe single root of
second premolar is larger and longer than the first premolar
Occlusal outline square in 3-cusp type, round in 2-cusp typeM and D profiles are parallelOcclusal table square or circularWith 2-cusp type, there are M and D triangular fossaeWith 3-cusp type, there is central fossa at junction of central and lingual sulci
3-cusp type Y- most common,
H- found in 2-cusp typeU- found in 2-cusp typeTwo pits- found in 2-cusp type
Buccal Aspect
Shorter buccal cusp than first premolar Mesiobuccal cusp ridge and distobuccal
cusp ridge less degree angulation Contact areas both broad ,appear
higher bec. Of short buccal cusp Root is broader mesiodistally than first
premolar Similar in this aspect-both first and
second premolar
Buccal Aspect
Lingual Aspect Variation from the
crown portion of of the first premolar:
Lingual lobes are dev. Making the cusps longer
Less of occlusal surface maybe seen from this aspect , part of the buccal portion of the occlusal surface maybe seen
In 3 cusp type lingual devt. brings about the greatest variation between the two teeth –there are mesiolingual -the larger and more longer one in most cases and a distolingual cusp
There is a groove between them extending a very short distance on the lingual surface and usually centered over the root
In the two cusp type,the lingual cusp development attains equal height with the three cusp. The two cusp type has no groove but it shows a devt. Depression distolingually where the lingual cusp ridge joins the distal marginal ridge
The lingual surface of the crown of all mand. Second premolars is smooth and spheroidalnhaving a bulbous form above the constricted cervical portion
Mesial Aspect
Crown and root are wider buccolingually
Marginal ridge is at right angles to the long axis of the tooth
Less of the occlusal surface maybe seen
Distal aspect The same with the
mesial aspect except more of the occlusal surface maybe seen
Crown of all posterior teeth are tipped distally to the long axis of the roots so that when the crowns of all post. Teeth are tipped distally to the long axis of the roots
Occlusal aspect
3 cusp type appear square lingual to the buccal cusp ridges when highly dev.
Has 3 cusp that are distinct: Buccal cusp largest Mesiolingual cusp distolingual cusp Each cusp has well formed triangular
ridges separated by a deep dev.grooves The groove form a Y on the occlusal
surface
Round or 2 cusp type- Outline of the crown is rounded
lingual to the buccal cusp ridges Lingual convergence of mesial and
distal sides Mesiolingual and disto lingual line
angles are rounded There is one well developed lingual
cusp directly opposite the buccal cusp in a lingual direction
Ten typical specimen
Central dev. Groove on the occlusal surface travels in a mesiodistal direction
2 cusp type appears round lingual to the buccal cusp ridges
Root extremely long Root dwarfed Malformed root developmental groove on buccal surface
Contact areas on crown high and constricted
Crown oversize; developmental groove buccally on root
Root oversize. Root malformed and of extra length Root very long with blunt apex; extreme
curvature at apical third Crown and root oversized; developmental
groove buccally on root Crown narrow buccolingually; very little
curvature buccally and lingually.