Permanent mandibular first premolar


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Permanent mandibular first premolar

  2. 2. Four in number Post. To mand. Canines Dev. From 4 lobes Sharp buccal cusp part that only occludes with maxillary teeth Always Smaller of the 2 premolars
  3. 3. CHARACTERISTICS THAT RESEMBLE THOSE OF THE MANDIBULAR CANINE Buccal cusp is long and sharp and is the occluding cusp Buccolingual measurement is similar to that of canine Occlusal surface slopes sharply lingually in a cervical direction Mesiobuccal cusp ridge is shorter than distobuccal cusp ridge
  4. 4. CHARACTERISTICS THAT RESEMBLE THOSE OF THE SECOND MANDIBULAR PREMOLAR  Outline of crown and root from the buccal aspect resemble the second premolar  Contact areas mesially and distally are near the same level  Curvatures of the cervical line mesially and distally are similar  Tooth has more than one cusp
  5. 5. BUCCAL ASPECT  Nearly symmetrical bilaterally  With pointed buccal cusp  Mesial cusp ridge is shorter than the distal cusp ridge  Contact areas are broad from this aspect. Almost at the same level  Crown is roughly trapezoidal  Tip of buccal cusp is pointed  Mesial outline straight or slightly concave  Distal outline of the crown is slightly concave  More convex than max. first premolar
  6. 6. LINGUAL ASPECT  Crown tapers toward lingual  Lingual cusp always small  Most of the mesial and distal surface of both maybe seen from the lingual aspect  Pointed lingual cusp tip ,align with the buccal triangular ridge of the occlusal surface  Mesial and distal occlusal fossae are on each side of the triangular ridge  Root is narrower on the lingual side Characteristic- mesiolingual developmental grrove act as demarcation line between mesiobuccal lobe and lingual lobe and extends into the mesial fossa of the occlusal surface
  7. 7. MESIAL ASPECT  Crown outline is rhomboidal  Tip is nearly centered over the root  Buccal cusp centered over the root  Accentuated convexity and location of the crest of contour are cha. Of all post. Teeth on the buccal surface  Smooth except for the mesiolingual groove  Root outline tapered from the cervix ending in a rel. pointed apex in line with the tip of the buccal cusp.the lingual outline may be straight the buccal outline more curved
  8. 8. DISTAL ASPECT  Distal marginal ridge is higher above cervix no lingual slope of the mesial marginal ridge  No devt. Groove on the distal marginal ridge  Distal contact area is broader than mesial contact area  Curvature of cervical line is maybe the same as that found mesially  Surface of root exhibits more convexity than was found mesially .shallow devt. Depression is centered on the root but rarely it contain a deep devt. groove.
  9. 9. OCCLUSAL ASPECT  Exhibit more variations in form occlusally than max. premolars  Outline form- diamond shape  Some has circular form similar to some mand. sec. premolars
  10. 10. CHARACTERISTICS COMMON TO ALL MANDIBULAR FIRST PREMOLARS  Middle buccal lobe makes up the major bulk of the tooth crown  Buccal ridge is prominent  Mesiobuccal and distobuccal line angles are prominent eventhough rounded  Marginal ridges are well dev.  Lingual cusp is small  Occlusal surface –heavy buccal triangular ridge and a small lingual triangular ridge  Occlusal surface- mesial and distal fossae
  11. 11.  Most common type of mandibular first premolars shows a mesiolingual devt. Depression and groove  These constrict the mesial surface of the crown and create a smaller mesial contact area  The distal portion of the crown is described by a larger arc that creates a broader proximal surface than the canine