06. Mandibular Molars - Dentition

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  • 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. :No. of surfaces It has five surfacesBUCCALLINGUAL:No. of roots It has 2 roots one mesial .& one distalMESIALOCCLUSALDISTAL 3. BUCCAL SURFACEThe 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. Occlusal outline: formed by 3 cusps, MB, DB, D DCervical outline: straight with dipping into the root bifurcationM 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 2DDevelopmental depression run M-D in* .the middle 1/3M 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. 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 ridgeMD 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. BUCCALLINGUAL:The root trunk appears longer on the ling. surface due to the occlusal position of cervical line* Lingual conversion * 10. MESIAL SURFACE The geometric outline: Rhomboid and inclined lingually. :NotesBML 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 sideL 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 rootBL 12. DISTAL SURFACELMESIAL SURFACEBLThe 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. OCCLUSAL SURFACEB 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 distallyDL 14. Anatomical landmarks:BElevations: *5 cusps with 5 triangular ridgesMDMMR and DMR* L 15. Anatomical landmarks:BDepressions: major central fossae + pit 1* Minor fossae ( mesial and distal 2* (triangular fossaeM:Developmental grooves* .Central groove is zigzag in its MD coarse MB groove , DB and L groove separating .the five cuspsDL 16. Pulp cavityBuccal viewPulp 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. Note: The two mesial root canals appear in x ray overlapping each other. 18. :Abnormalities you may find .Three or four roots- 1 .Four root canals- 2 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. :Label the different surfacesBuccal surface Lingual surface Mesial surface Distal surface 21. ?What is this 22. ?What is this 23. ?What is this 24. ?What is this 25. :No. of surfaces It has five surfacesBUCCAL:No. of roots It has 2 rootsLINGUALMESIALOCCLUSALDISTAL 26. BUCCAL SURFACESGeometric outline: Trapezoid with small uneven side located cervicallyM: 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 distallyD 27. LINGUAL SURFACED 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. MESIAL SURFACEThe geometric outline: Rhomboidal with lingual inclination *MMR is concave The mesial root is only* visible Longitudinal depression on the* mesial surface of mesial rootLB 29. DISTAL ASPECT B DMR is concave but less* angular than MMR Distal root is narrower than mesial* root, so both roots are seenL 30. BOCCLUSAL SURFACEThe geometric outline:MRectangular. DNote: * Disto-Lingual convergence. * Mesio-Distally is larger than bucco -lingually.L 31. BOCCLUSAL SURFACEThe 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 *MDL 32. B:Depression major central fossa with central pit 1* Minor fossae ( mesial and distal 2* )triangular fossaeDDevelopmental grooves: form a typical* Cross pattern Supplemental grooves radiate from the * developmental grooves Note : All grooves provide important escape ways for food during masticationML 33. Pulp cavity Pulp Chamber:MDBBucco-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 canalL 34. Pulp cavityMNote: 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 canalD BL 35. :No. of surfaces It has five surfacesBUCCALMESIALLINGUALOCCLUSALDISTAL 36. BUCCAL SURFACEThe 3rd molar is either 4 or 5 cusp* type .Type 1&Type IIDThe 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 molarsM 37. MESIAL SURFACEBLThe buccal cusp tips are closer to the lingual cusp tips giving a small occlusal table DISTAL SURFACEThere is a distal convergence Distal root is narrower than mesial root, so both roots are seenLB 38. OCCLUSAL SURFACEThe geometric outline: Rectangular or ovalBMDThere are numerous supplemental grooves and pits give a wrinkled appearanceL 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. ?What is thisL. surface 7 41. ?What is thisD. Surf. 7 42. Occ. Surf. 7 43. MMR 7 44. DL cusp 7 45. CDG 7 46. BDG 7 47. M F7