06. Mandibular Molars - Dentition


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06. Mandibular Molars - Dentition

  1. 1. .First permanent molar to calcify and erupt .It is known as six years molar tooth ?WHY .Its number in the lower arch is # 6 & .Its eruption date is six years Functionally, it is considered as the key of .occlusion
  2. 2. :No. of surfaces It has five surfaces BUCCAL LINGUAL :No. of roots It has 2 roots one mesial .& one distal MESIAL OCCLUSAL DISTAL
  3. 3. BUCCAL SURFACE The geometric outline: Trapezoidal with the small uneven side present cervically. D Mesial outline: concave till the contact area at the junction of the occlusal and middle 1/3. Distal outline: convex till the contact area beneath the distal cusp ridge. M
  4. 4. Occlusal outline: formed by 3 cusps, MB, DB, D D Cervical outline: straight with dipping into the root bifurcation M
  5. 5. Surface anatomy:the buccal surface is convex with the maximum convexity at the cervical 1/3 representing the cervical .ridge Developmental grooves MB &DB . separating the three buccal cusps • 2D Developmental depression run M-D in* .the middle 1/3 M
  6. 6. The Roots: The Roots: *The roots are twice the length of the crown. The mesial root is directed mesially till the middle 1/3 then it curves distally. The distal root is straight and directed distally . M D * Root trunk: 3 mm. •The axis of the roots are inclined • distally * Deep developmental groove extend on the root trunk.
  7. 7. LINGUAL SURFACE * Lingual convergence Mesial outline: Straight till the contact area at the junction of the occlusal and middle 1/3 Distal outline: Convex till the contact area beneath the distal cusp ridge M D
  8. 8. Occlusal outline: formed by 2 lingual M cusps, ML, DL of nearly equal width Cervical outline: Irregular with dipping into the root bifurcation :Surface anatomy Lingual developmental groove separating the two lingual cusps. D
  9. 9. BUCCAL LINGUAL :The root trunk appears longer on the ling. surface due to the occlusal position of cervical line* Lingual conversion *
  10. 10. MESIAL SURFACE The geometric outline: Rhomboid and inclined lingually. :Notes B ML cusp is more pointed than MB cusp -1 (( because it is out of occlusion The cervical line slants occlusally from the- 2 .buccal to the lingual side L
  11. 11. MESIAL SURFACE :Surface anatomy The surface is concave cervical to* the contact area which is centered B-L below the crest of marginal ridge Deep developmental depression on the* .mesial surface of the root B L
  12. 12. DISTAL SURFACE L MESIAL SURFACE B L The crown is shorter distally* *There is a distal convergence *DMR is U- shape, shorter and more cervically than MMR *Distal contact area is located below the distal cusp more to the buccal .Distal DG is the extension of the CDG on the distal surface.The M root is broader than the D root.
  13. 13. OCCLUSAL SURFACE B The geometric outline: Hexagonal with 3 buccal sides , one lingual ,one mesial and one distal . M * The crown measurements is larger MD than BL . * The crown converge lingually and distally D L
  14. 14. Anatomical landmarks: B Elevations: *5 cusps with 5 triangular ridges M D MMR and DMR* L
  15. 15. Anatomical landmarks: B Depressions: major central fossae + pit 1* Minor fossae ( mesial and distal 2* (triangular fossae M :Developmental grooves* .Central groove is zigzag in its MD coarse MB groove , DB and L groove separating .the five cusps D L
  16. 16. Pulp cavity☻ Buccal view ►Pulp Chamber: . The pulp chamber is broad MD.It is almost rectangular in shapeThere is a pulp horn beneath eachcusp Mesial view :Root Canals► -3 main root canals. -M root has 2 root canals while D root has 1 root canal.
  17. 17. Note: The two mesial root canals appear in x – ray overlapping each other.
  18. 18. :Abnormalities you may find .Three or four roots- 1 .Four root canals- 2
  19. 19. Enumerate the names of the following ?elevations and depression Central groove-1 MMR-2 Central fossa-3 Distal triangular fossa-4 Mesio-buccal groove-5
  20. 20. :Label the different surfaces Buccal surface Lingual surface Mesial surface Distal surface
  21. 21. ?What is this
  22. 22. ?What is this
  23. 23. ?What is this
  24. 24. ?What is this
  25. 25. :No. of surfaces It has five surfaces BUCCAL :No. of roots It has 2 roots LINGUAL MESIAL OCCLUSAL DISTAL
  26. 26. BUCCAL SURFACES Geometric outline: Trapezoid with small uneven side located cervically M : Anatomical Landmark .Buccal developmental groove may end in a buccal pit .MB cusp is longer than the DB cusp The roots are closer and nearly parallel with more pointed apex .than 6 ,the are directed distally D
  27. 27. LINGUAL SURFACE D The Crown The lingual cusps are more pointed than buccal cusps. Anatomical Landmark: Lingual developmental groove never pitted. The Roots Short root trunk with a developmental depression. M
  28. 28. MESIAL SURFACE The geometric outline: Rhomboidal with lingual inclination *MMR is concave The mesial root is only* visible Longitudinal depression on the* mesial surface of mesial root L B
  29. 29. DISTAL ASPECT B DMR is concave but less* angular than MMR Distal root is narrower than mesial* root, so both roots are seen L
  30. 30. B OCCLUSAL SURFACE The geometric outline: M Rectangular. D Note: * Disto-Lingual convergence. * Mesio-Distally is larger than bucco -lingually. L
  31. 31. B OCCLUSAL SURFACE The geometric outline is rectangular Anatomical landmarks: Elevations: *4 cusps with 4 triangular ridges ( mesial cusps are larger than distal cusps). .Mesial and distal marginal ridge * M D L
  32. 32. B :Depression major central fossa with central pit 1* Minor fossae ( mesial and distal 2* )triangular fossae D Developmental grooves: form a typical* Cross pattern Supplemental grooves radiate from the * developmental grooves Note : All grooves provide important escape ways for food during mastication M L
  33. 33. Pulp cavity☻ Pulp Chamber: M DB Bucco-Lingually, the pulp ► chamber is square Mesio-Distally, the pulp► chamber is rectangular There is pulp horn beneath eachcusp :Root Canals -3 main root canals. -M root usually has 2 root canals while D root has 1 root canal L
  34. 34. Pulp cavity☻ M Note: Cervical cross section: Triangular due to small dimension distally Mid root section: *M root is kidney shape with 2 small canals *D root is oval with 1 large rounded canal D B L
  35. 35. :No. of surfaces It has five surfaces BUCCAL MESIAL LINGUAL OCCLUSAL DISTAL
  36. 36. BUCCAL SURFACE The 3rd molar is either 4 or 5 cusp* type .Type 1&Type II D The buccal surface is convex* Short roots (M and D) may be 2 * fused in all or part of their length The roots are more inclined distally* than 1st and 2nd molars M
  37. 37. MESIAL SURFACE B L The buccal cusp tips are closer to the lingual cusp tips giving a small occlusal table DISTAL SURFACE There is a distal convergence Distal root is narrower than mesial root, so both roots are seen L B
  38. 38. OCCLUSAL SURFACE The geometric outline: Rectangular or oval B M D There are numerous supplemental grooves and pits give a wrinkled appearance L
  39. 39. ☻ Note: 1-The 3rd molar may show multiple variations in the size and shape. The pulp cavity may also show great- 2 variations in the size and shape The pulp chamber of 8 is larger than other- 3 molars because it is younger than other molars by 9-11 years
  40. 40. ?What is this L. surface 7
  41. 41. ?What is this D. Surf. 7
  42. 42. Occ. Surf. 7
  43. 43. MMR 7
  44. 44. DL cusp 7
  45. 45. CDG 7
  46. 46. BDG 7
  47. 47. M F7