1. Resembles the mand.first premolar -buccal aspect only Assumes 2 common forms: 3 cusp type- angular 2 cusp type- more rounded The single root of second premolar is larger and longer than the first premolar
2. Occlusal outline squarein 3-cusp type, round in 2-cusp type M and D profiles are parallel Occlusal table square or circular With 2-cusp type, there are M and D triangular fossae With 3-cusp type, there is central fossa at junction of central and lingual sulci 3. 3-cusp type Y- mostcommon, H- found in 2-cusp typeU- found in 2-cusp type Two pits- found in 2cusp type 4. Buccal Aspect Shorter buccal cusp than first premolar Mesiobuccal cusp ridge and distobuccal cuspridge 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 5. Buccal Aspect 6. Lingual Aspect Variation from thecrown 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 7. 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 8. In the two cusp type,the lingual cuspdevelopment 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 9. The lingual surface of the crown of all mand.Second premolars is smooth and spheroidalnhaving a bulbous form above the constricted cervical portion 10. Mesial Aspect Crown and root arewider buccolingually Marginal ridge is at right angles to the long axis of the tooth Less of the occlusal surface maybe seen 11. Distal aspect The same with themesial 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 12. 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 13. Round or 2 cusp type Outline of the crown is rounded lingual to thebuccal 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 14. Ten typical specimen 15. Central dev. Groove on the occlusal surfacetravels in a mesiodistal direction 16. 2 cusp type appears round lingual to thebuccal cusp ridges 17. Root extremely long Root dwarfed Malformed root developmental groove on buccal surface Contact areason crown high and constricted Crown oversize; developmental groove buccally onroot Root oversize. Root malformed and of extra length Root very long with blunt apex; extreme curvature atapical third Crown and root oversized; developmental groovebuccally on root Crown narrow buccolingually; very little curvaturebuccally and lingually.