First premolar


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First premolar

  1. 1. • Four in numbers • Anterior to the molars in the permanent dentition • Crowns are shorter than those of maxillary canine
  2. 2. • Has 2 cusps buccal & lingual • Buccal cusp 1mm longer • Crown is angular • Crown is shorter than canine • 1.5-2 mm. on the average • Mesial slope is longer than the distal • Most have 2 roots and 2 pulp canals
  3. 3. • Crown is roughly trapezoidal • Little curvature at the cervical line • Mesial slope of buccal cusp is longer than distal slope,sometimes notched ,concave. • Distal contact area represented by a broader curvature than found in mesial even so contact areas are more nearly level than those found in anterior teeth.
  4. 4. • Buccal cusp is long • Buccal surface is convex with middle buccal lobe
  5. 5. • Crown tapers toward the lingual • lingual cusp is narrower mesiodistally than buccal cusp • lingual cusp is smooth and spheroidal • Cusp tip is pointed with convex mesial and distal outline • Cusp is narrower than the buccal cusp • Lingual roots smooth and convex at all points more blunt root apex than the buccal root
  6. 6. • Roughly trapezoidal • 2 roots clearly outline in this aspect • Lingual outline of the crown is smoothly curving line from the cervical line and ends at the tip of the lingual cusp • Tip of the lingual cusp is on the line with the lingual border of the lingual root • Lingual cusp is always shorter than the buccal cusp
  7. 7. • Buccal outline of the buccal root above the cervical line is straight with a tendency toward lingual inclination • The lingual outline of the lingual root is straight above the cervical line
  8. 8. • The root trunk is long half of the root length • Bifurcation begins at a more occlusal point mesially than distally
  9. 9. • Found on the mesial surface of the crown cervical to the mesial contact area centered on the mesial surface and bordered buccally and lingually by the mesiobuccal and mesiolingual line angles called mesial developmental depression
  10. 10. • • Well defined developmental groove in the enamel of mesial marginal ridge . • This groove is continuous with the central groove of the occlusal surface of the crown
  11. 11. • Crown surface is convex at all points • The curvature of the cervical line is less on the distal than on the mesial surface often showing a line straight across from buccal to lingual • Root trunk is flattened above the cervical line • Bifurcation of root is abrupt near the apical third with no developmental groove leading to it
  12. 12. • Resembles a six sided or hexagonal figure • Made up of mesiobuccal, mesial, distolingual, distal, distobuccal, mesiolingual • Buccal surface is visible than the lingual surface • No supplemental grooves • Well defined central developmental groove divides the surface evenly buccolingually
  13. 13. • Mesiobuccal cusp ridge and distobuccal cusp ridges are in line with each other and their alignment is in distobuccal direction • The distobuccal cusp ridge is buccal to the mesiobuccal cusp ridge
  14. 14. • Two dev. grooves join the central groove just inside the mesial and distal marginal ridges • Mesial marginal dev. groove • Distal marginal dev. groove • The junction of the grooves are deeply pointed • Mesial and distal developmental pits
  15. 15. • Distal to the mesial marginal ridge mesial triangular fossa • Mesial to the distal marginal ridge distal triangular fossa • Buccal triangular ridge of the buccal cusp is prominent • Lingual triangular ridge is less prominent • Lingual cusp is pointed sharply than the buccal cusp
  16. 16. • Two distinctive traits help is distinguishing right and left.  The mesial developmental depression  mesially displaced lingual cups tips are consistent clues for determining right and left.  When well defined, the mesial marginal ridge is also a clue to right and left