06. Mandibular Molars - Dentition
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06. Mandibular Molars - Dentition

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    06. Mandibular Molars - Dentition 06. Mandibular Molars - Dentition Presentation Transcript

    • .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
    • :No. of surfaces It has five surfaces BUCCAL LINGUAL :No. of roots It has 2 roots one mesial .& one distal MESIAL OCCLUSAL DISTAL
    • 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
    • Occlusal outline: formed by 3 cusps, MB, DB, D D Cervical outline: straight with dipping into the root bifurcation M
    • 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
    • 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.
    • 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
    • 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
    • BUCCAL LINGUAL :The root trunk appears longer on the ling. surface due to the occlusal position of cervical line* Lingual conversion *
    • 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
    • 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
    • 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.
    • 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
    • Anatomical landmarks: B Elevations: *5 cusps with 5 triangular ridges M D MMR and DMR* L
    • 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
    • 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.
    • Note: The two mesial root canals appear in x – ray overlapping each other.
    • :Abnormalities you may find .Three or four roots- 1 .Four root canals- 2
    • 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
    • :Label the different surfaces Buccal surface Lingual surface Mesial surface Distal surface
    • ?What is this
    • ?What is this
    • ?What is this
    • ?What is this
    • :No. of surfaces It has five surfaces BUCCAL :No. of roots It has 2 roots LINGUAL MESIAL OCCLUSAL DISTAL
    • 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
    • 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
    • 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
    • DISTAL ASPECT B DMR is concave but less* angular than MMR Distal root is narrower than mesial* root, so both roots are seen L
    • B OCCLUSAL SURFACE The geometric outline: M Rectangular. D Note: * Disto-Lingual convergence. * Mesio-Distally is larger than bucco -lingually. L
    • 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
    • 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
    • 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
    • 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
    • :No. of surfaces It has five surfaces BUCCAL MESIAL LINGUAL OCCLUSAL DISTAL
    • 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
    • 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
    • OCCLUSAL SURFACE The geometric outline: Rectangular or oval B M D There are numerous supplemental grooves and pits give a wrinkled appearance L
    • ☻ 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
    • ?What is this L. surface 7
    • ?What is this D. Surf. 7
    • Occ. Surf. 7
    • MMR 7
    • DL cusp 7
    • CDG 7
    • BDG 7
    • M F7