Wk 5 retentional factors


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Wk 5 retentional factors

  1. 1. Retentional factors
  2. 2. Retentional factors1. Clinical anatomical features2. Physical features3. Retention aids
  3. 3. Functional stability= denture usageStability duringfonation:The denture does notmove disturbingly fromthe mucosal-bony baseduring fonation ,mouthopening and closing,swallowing, articulationin connection withfonationStability duringmastication:The denture does notmove disturbingly fromthe mucosal-bony baseduring mastication andarticulation inconnection withmastication
  4. 4. 1. Clinical anatomy featuresI. The size of the mucosal bony base thatis suitable for bearing mastication forcesII. The height of the edentulous alveolarridgeIII. Retential areasIV. Neuromuscular forces
  5. 5. The useable place which can bear themasticatory pressureAlveolar process is the edentulous alveolarridge after losing natural teeth.In case of severe resorption the body of themandibule is covered by the base of thedenture.The height of the alveolar process will inhibitthe horizontal displacement of the denture.
  6. 6. The useable place which can bear themasticatory pressure Upper arch: 3937 mm2 Lower arch: 1770 mm2 It is approximately equal with the polishedsurface of the baseplate This area play an important role in keepingdenture in place
  7. 7. The size of the mucosal bony base, that is suitablefor the retention of the denture, influence:Effectiveness of the physical forcesMastication force that loads the mucosal bonybase (24-25 N)
  8. 8. 1. Clinical anatomy featuresIII. Retentional areason the upper jaw:Maxillary tuberHigh and curvedquadrangular shapedridgeUndercut area betweenthe buccal frenules inthe vestibule
  9. 9. 1. Clinical anatomy featuresIII. Retentionalareas on the lowerjaw:Lingual fossa
  10. 10. 1. Clinical anatomy featuresIII. Retentionalareas on the lowerjaw:Edentulous ridge:totally preserved highridge
  11. 11. 1. Clinical anatomy featuresIV. Neuromuscular forces:The surrounding muscles and active andpassive muscle functions have the mostimportant stabilizing effectThe oral mucosa (bucca, lips, tongue) andthe underlying musculature touch andload the polished surface of the denturewith various forces during mastication (20-30 N)
  12. 12. 2. Physical forces1. Capillary pressure2. Ventill effect (inner/outter)3. Gravity4. Masticatory pressure
  13. 13. I. Capillary pressure (upper/lower):Surface tension of the saliva between thedenture baseplate and the mucosaAdhesion: connecting force between unlikemolecules (mucosa-saliva)Cohesion: connecting force between alikemolecules (saliva-saliva)If the saliva film is thinner, the force ofretention will be betterLack or overproduction of saliva affectnegatively for retention
  14. 14. II. Ventill effect (upper/lower):Seal the border of thedentureVacuum is created under thedenture baseInner ventill effect:The border of the denture issinked into the mobilemucosaOutter ventill effect:Connection between themucosal surface of thedenture and the
  15. 15. III. Gravity (lower)Casted metal baseCasted metal arteficial teethMax.:32-35 gThe excessive loading cause atrophyMasticatory pressure:Natural dentition: 120-140 KpaEdentulous: 20-30 Kpa
  16. 16. IV. Masticatory pressure:The denture stability by masticatory forcesdepends on the occlusal pattern of thearteficial posterior teeth: Anatomical arteficial posterior teeth:Different OV widthAngle between the slope of the cusp andhorizontal plane is different (20-45 degree)Material can be ceramic or acrilicIt has always shifter effectIt cause horizontal displacement of thedenture
  17. 17. 2. Physical forcesNon-anatomical arteficial posterior teeth:It has stabilizing effectMechanical occlusal-surfaced molar:the occlusal surface is non-anatomicalthe vestibular, oral and approximal surfaces areanatomicalMechanical molar:it is not compare of the natural teeth
  18. 18. French-type artifical posterior teethIt was used on olderpeople in abrasive teeth
  19. 19. Myerson-typeNormal artificial teethhas flat, shallow fissureTransversal cutterMarginal cutter
  20. 20. 2. Conclusion of physical forcesProsthetic function is more important thancosmetic ones in the posterior region:Stabilization of the dentureProtection of the mucosal bony baseBetter mastication
  21. 21. 3. Retention aidDenture fixative:Unfavourable situationsNervus system disordersSurgical or congenital defectsShortening initial learning period
  22. 22. Retention aidMicrovalves, denture adhesives (Corega)Suction disc (don’t use it)Denture spring (don’t use it)Grooves cut into the palate of the master cast