TOOTH MORPHOLOGY

TOOTH MORPHOLOGY

1. DECIDUOUS AND PRIMARY DENTITION

2. By 3yrs old deciduous dentition is complete

3. By 6yrs 1st permanent molars appaear

   • Complete permanent dentition by 18yrs

4. Only permanent Incisors, Canines and premolars have predecessors

5. During jaw growth spaces develop interdentally in decid dentititon - Primate spaces

   • Decid incisors, canines, molars replaced at 7-13yrs
   • 3 additional perm molars appear at 6,12, 18yrs

6. TOOTH ERUPTION

   • The process whereby a tooth moves from its developmental space to its functional position
     • The main direction is axial but movement also occurs in other planes
   • Rate of eruption is at its greatest at crown emergance. Rates differ according to tooth
   • As the tooth approaches the oral cavity the overlying bone is resorbed

7. Eruption sequence of Decidous - ABDCE. Mandibular before Maxillary

8. Eruption sequence of permanent

   • Mandibular - 61234578
     • Maxillary - 61245378

9. Completion of the root takes place 2yrs after eruption

10. DIFFERENCES OF DENTITIONS

    • Decid are smaller
    • lighter in colour
    • crowns are more bulbous
    • More slender and root canals v fine
    • Roots more divergent to allow perm dent space
    • Enamel less hard than perm
    • Ratio of pulp and crown is much smaller in decid

11. FUNCTIONS OF DENTITION

    • mastication
    • Speech
    • Aesthetics
    • Maintains Profile
    • Maintains space for Perm dentition

12. MAX 1st PERM INCISOR

    • Widest mesiodistally
    • Wedge chisel shaped
      • Single root, distal curvature
    • 2 Labial grooves give rise to mamelons
    • Distally rounded
    • Mesially straight

13. MAX 2nd PERM INCISOR

    • Shorter and narrower than 1st
      • Distal angle more rounded
    • Well marked Cingulum
    • Groove cingulum and lingual fossa - prone to caries
    • May be congenitally missing
    • Grooves on mesial and distal aspects of the root

14. MAX PERM CANINE

    • Prominent tooth (eye tooth)
    • Longest root, triangular in section, wider labially than palatally
    • Stout barrel shaped
    • Distal slope of cusp longer than mesial
    • Marked cingulum palatally

15. MAX 1st PREMOLAR

    • Larger crown than U 2nd premolar
    • 2 roots - 1 buccal and 1 palatal
    • Buccal cusp higher than palatal
    • Marked depression on mesial aspect (Canine Fossa)
    • Immediately below contact with canine - can be hard to remove calculus here

16. MAX 2nd PREMOLAR

    • 1 Root
    • No canine fossa
    • Root may have deep groove mesially and distally but no bifurcation
    • Cusps are more equal height
      • Mesial slope of cusp shorter than distal

17. MAX 1st PERM MOLAR

    • 3 roots, mesiobuccal, distobuccal, palatal
    • Palatal root is largest and most divergent
      • MB and DB roots curve towards each other
    • MP cusp is largest and joined to DB cusp by Oblique Ridge
    • Fissure pattern H shaped
    • Occ crown is Rhomboid shaped
    • Cusp of Carabelli - 5th cusp, present palatally 60% of 6's

18. MAX 2ND MOLAR

    • Rhombic occ outline
    • Roots less divergent

19. MAX 3RD MOLAR

    • Triangular occ outline
    • Smallest max molar
    • congenitally missing or no eruption
    • Roots short and fused, curve distally