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PERMANENT MAXILLARY PREMOLARS

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Anatomical features of a permanent maxillary premolars.

Published in: Health & Medicine

PERMANENT MAXILLARY PREMOLARS

  1. 1. Maxillary Premolars Dr. Ramil B. Simsuangco Oral Anatomy Professor College of Dentistry Manila Central University
  2. 2. GENERAL DESCRIPTION ◦ There are eight(8) premolars in the human dentition; 2 upper, 2 lower ◦ For Maxillary: Using 2-digit system with notation tooth numbers 14,15,24,25 14 24 15 25
  3. 3. Functions of Premolars  1st premolars function with canine 1) In shearing or cutting food 2) Support the corners of the mouth  2nd premolars function with molars 1) To masticate 2) To maintain vertical dimension
  4. 4. DEVELOPMENTAL LOBES 1) Developmental lobes ◦ Facial surface develops from three lobes ◦ Buccal ridge more prominent in maxillary arch ◦ One developmental lingual lobe (cingulum or cusp) ◦ Exception: Mandibular 2nd premolar (can have 2 lingual lobes) 123 1 exception 1 2
  5. 5. CURVATURE OF CEJ ◦ Proximal CEJ is concave Facial and lingual CEJ is convex apically
  6. 6. CONVEXITY Convex 4) Root shape ◦ Lingual and facial surfaces are convex ◦ Lingual side of the root and crown are narrower than the facial side
  7. 7. Differences To Anterior Teeth Buccal Labial 1) Terminology Facial ◦ Facial surface now correctly called the buccal surface (not labial) ◦ Possess occlusal surfaces not incisal edges
  8. 8. Differences To Anterior Teeth 2) Occlusal surface versus incisal edges ◦ No incisal edge or cingulum ◦ Possess one facial cusp and one or two lingual cusps Incisal Occlusal Cingulum
  9. 9. CONTACT AREAS Proximal contact areas are more cervically located than anterior teeth
  10. 10. BUCCAL ASPECT Crown is broadest at level of contact areas and narrow at the cervix  Has trapezoidal shape  Mesial and distal sides straight from contact to cervix
  11. 11. BUCCAL ASPECT 2) Cusp slope size ◦ Buccal cusp tip often slightly mesial to long axis (like canine) ◦ Mesial cusp slope shorter than the distal ◦ Exception: Maxillary first premolar - cusp tip slightly to the distal
  12. 12. BUCCAL ASPECT Buccal Ridge 4) Crown morphology ◦ Buccal surface is convex ◦ Buccal ridge runs occluso-cervically in the middle of the crown
  13. 13. Buccal Aspect - Buccal Cusp Tip Location  Exception: Maxillary first premolar has a cusp tip slightly to the distal of the mid-tooth line  This creates a mesial cusp ridge longer than the distal cusp ridge  The opposite is true for maxillary second premolars
  14. 14. Buccal Class Traits Of Premolars Distal Bend 5) Root ◦ Buccal surface is convex with an apical taper ◦ The apical third may possess a distal bend
  15. 15. LINGUAL ASPECT Exception 29  Crown is narrower on the lingual than the buccal  Exception: Mandibular 2nd premolars with three cusps  Lingual surface is convex  Mesial and Distal slope meets at 90 deg. angle
  16. 16. Lingual Class Traits Of Premolars 2) Root ◦ Lingual surface is convex and narrower mesiodistally than the facial aspect
  17. 17. Lingual Aspect - Lingual Cusp Position  The cusp tip always bends towards the mesial on unworn lingual cusps  This makes it easy to tell right from left M
  18. 18. MESIAL ASPECT 1) Triangular ridges ◦ Buccal and lingual triangular ridges meet in the central groove forming the transverse ridge ◦ Exception: Mandibular 2nd premolar (three cusp form) Mesial View
  19. 19. MESIAL ASPECT Mesial View 3) Marginal ridges ◦ Mesial marginal ridge more occlusal/higher than the distal ◦ Exception: Mandibular first premolars
  20. 20. DISTAL ASPECT  Crown outline is trapezoidal  Crown is convex, with small flattened area just cervical to the CA  No evidence of deep developmental groove and depression
  21. 21. Occlusal Class Traits Of Premolars 4 5 28 29 1) Tooth proportions ◦ Considerably wider faciolingually than mesiodistally
  22. 22. Occlusal Class Traits Of Premolars 4 5 28 29 2) Occlusal table ◦ Both buccal and lingual cusps have mesial and distal cusp ridges or slopes which travel cervically to join the marginal ridges ◦ These structures form the occlusal table (or outline)
  23. 23. Occlusal Class Traits Of Premolars 4 5 28 29 4) Grooves and fossae ◦ Central developmental groove runs mesiodistally ◦ Exceptions: Mandibluar 1st premolar and three-cusped 2nd premolar ◦ Fossae possess supplemental grooves to the buccal and lingual
  24. 24. Buccal Aspect - Contacts  Mesial contact is in the middle third, near the junction of the middle and occlusal thirds  Distal contact is slightly more cervical (still in middle third) More Cervical As We Go Distal
  25. 25. COMPARISON OF CUSP HEIGHT (Max. 1st PM and Max. 2nd PM) Mesial Distal B 5 4 4 5  From this view buccal cusp tip is noticeably longer than the lingual cusp tip on maxillary first premolars  Nearly equal length on second premolars
  26. 26. Proximal Aspect - Marginal Ridge Mesial Distal  Distal marginal ridge is more cervical than mesial marginal ridge  Can see more of the occlusal surface from the distal B 5 4 4 5
  27. 27. NUMBER OF ROOT Mesial Distal B B 5 4 4 5  Frequently two(2) roots on Maxillary 1st premolar  The bifurcation is in the apical third to half of the root
  28. 28. Proximal Aspect - Root Depressions Mesial Distal B B 5 4 4 5  Maxillary first premolar has prominent root depressions  On second premolars there is a mesial and distal root depression, usually more prominent on the distal
  29. 29. Occlusal Comparison of 1st and 2nd premolar
  30. 30. MDD and MMDG Mesial B Mesial Developmental Depression(MDD)- mesial concavity on the crown and root 5 4 Mesial Marginal Developmental Groove(MMDG)- developmental groove on the mesial marginal ridge, in alignment with mesial developmental depression

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