Retention of complete dentures

1. RETENTION OF COMPLETE DENTURES DEEPTHI P.R. FINAL YEAR BDS

2. CONTENTS Introduction Definition Factors affecting retention - Classification - Interfacial force - Adhesion -Cohesion -Oral & facial musculature

3. CONTENTS -Atmospheric Pressure -Undercuts, Rotational insertion paths, Parallel walls -Gravity Denture Adhesives Conclusion Bibliography

4. INTRODUCTION Success of treatment with CD Integration of oral functions + psychological acceptance Perception of the dentures as stationary during function

5. DEFINITION ‘That quality inherent in the prosthesis which resists the force of gravity, adhesiveness of foods, and the forces associated with the opening of jaws’ - GPT The resistance of removal in a direction opposite that of insertion - Boucher

6. DEFINITION The resistance of the movement of a denture from its basal seat, especially in a vertical direction - Winkler The resistance it poses to withdrawal from its planned position in the mouth - Grant & Johnson

7. FACTORS AFFECTING DEGREE OF RETENTION Atmospheric pressure Surface tension Viscosity of saliva Physical retention: area of the denture adaptation of denture viscosity of saliva volume of saliva wettability of the denture base resin

8. RETENTION ANATOMICAL Size of the denture bearing area Quality of the denture bearing area Parallel ridge walls PHYSIOLOGICAL Saliva PHYSICAL Adhesion Cohesion Interfacial surface tension Capillarity Atmospheric pressure Gravity MECHANICAL Undercuts Retentive springs Magnetic forces Denture adhesives Suction chambers & discs Palatal implants MUSCULAR Oral musculature Facial musculature

9. FACTORS AFFECTING DEGREE OF RETENTION Primary retention - physical means - mechanical means Secondary retention - surrounding musculature - shape of the denture borders & flanges - psychological factors - proper instructions

10. DISLODGING FORCES Mastication Adhesive food Gravity (upper) Surrounding musculature Occlusal prematurities Parafunctional habits

11. INTERFACIAL FORCE ‘The tension or resistance to separation possessed by the film of liquid between two well-adapted surfaces’ - GPT ‘The resistance to separation of two parallel surfaces that is imparted by a film of liquid between them’

12. INTERFACIAL FORCE Interfacial surface tension Viscous tension

13. INTERFACIAL FORCE INTERFACIAL SURFACE TENSION Thin layer of fluid that is present between two parallel planes of rigid material Ability of the fluid to wet the rigid surrounding material Low surface tension : maximize contact- spread out in thin film High surface tension : minimize its contact – formation of beads on the material’s surface

14. INTERFACIAL FORCE Processed denture base materials- higher wettability High surface tension reduced on coating by the salivary pellicle Retention by virtue of the tendency of the fluid to maximize the contact between the denture base & mucosa

15. INTERFACIAL FORCE Capillarity ‘That quality or state, because of surface tension causes elevation or depression of the surface of a liquid that is in contact with a solid’ - GPT

16. INTERFACIAL FORCE Close adaptation between denture base & mucosa- thin film of saliva in the space Retention- Capillary tube in which the liquid seeks to increase its contact

17. INTERFACIAL FORCE Important in maxilla If two plates with interposed fluid immersed in the same fluid- no resistance External borders of mandibular denture awash in saliva

18. INTERFACIAL FORCE INTERFACIAL VISCOUS TENSION Force holding two parallel plates together that is due to viscosity of the interposed liquid

19. Stefan’s law: For two parallel, circular plates of radius (r) that are separated by a newtonian (incompressible) liquid of viscosity (k), & thickness (h), the force (F) necessary to pull the plates apart at a velocity (V) in a direction perpendicular to the radius will be F= (3/2) π kr 4 V h 3

20. INTERFACIAL FORCE Viscous force viscosity of the fluid Viscous force thickness of the medium Viscous force opposing surface area

21. INTERFACIAL FORCE Optimal adaptation- minimal ‘h’ Maximizing denture bearing area- maximum ‘r’ Increasing the viscosity of the medium Slow steady displacing action- small ‘V’ effective at removing the denture than a large ‘V’ Enhanced by ionic forces- adhesion & cohesion

22. ADHESION ‘Physical attraction of unlike molecules for each other’ IONIC FORCES Salivary glycoproteins Acrylic resin in denture base Surface epithelium of the mucous membrane

23. ADHESION Xerostomia : Adhesion between denture base & the dry mucosa Not very effective- mucosal abrasions & lacerations Ethanol free rinse with aloe or lanolin Saliva substitute with carboxymethylcellulose / mammalian mucin Sjogren’s syndrome: 5-10mg oral pilocarpine tds

24. ADHESION Retention by adhesion with area covered by denture Mandibular dentures , small jaws, very flat alveolar ridges- less adhesion Dentures extended to limits of the health & function of oral tissues Preserve the alveolar height

25. COHESION ‘Physical attraction of like molecules for each other’ Within the layer of interposed saliva & maintains its integrity Normal saliva not very cohesive unless modified High mucinous saliva- though more cohesive, less retentive

26. ORAL & FACIAL MUSCULATURE Supplement retention if: Teeth are positioned in the neutral zone Polished surfaces of the denture are properly shaped Buccal & lingual flanges should be so shaped that the musculature fits automatically

27. ORAL & FACIAL MUSCULATURE Buccal flange Buccinators tend to retain both Tongue perfect the border seal if: lingual surfaces of the lingual flanges slope toward the centre of the mouth MAXILLA: Slope up & out from the occlusal plane MANDIBLE: Slope down & out from the occlusal plane

28. ORAL & FACIAL MUSCULATURE Lingual side of the distal end of the lingual flange: Guides the base of the tongue on top of the lingual flange Ensures the border seal at the back end of mandibular denture Base of tongue: emergency retentive force

29. ORAL & FACIAL MUSCULATURE Most effective in retention when: The denture bases are properly extended to cover the maximum area possible The occlusal plane is at the correct level The arch form of the teeth is in the neutral zone

30. ATMOSPHERIC PRESSURE Resist dislodging forces to dentures with an effective seal Called Suction: resistance to removal from the basal seat No suction unless another force is applied Suction alone applied: serious damage to the health of the soft tissues

31. ATMOSPHERIC PRESSURE Force exerted perpendicular to & away from the basal seat of a properly extended & fully seated denture Pressure between the tissues & the denture drops below the atmospheric pressure: resists displacement Retention area covered by the denture

32. ATMOSPHERIC PRESSURE Most effective in retention when: Denture has a perfect seal around its entire border Proper border molding with physiological, selective pressure techniques is carried out

33. UNDERCUTS Modest undercuts enhance retention: resiliency of the mucosa & submucosa Exaggerated bony undercuts: compromise retention Less severe ones: extremely helpful Lateral tuberosities Maxillary premolar areas Distolingual areas Lingual mandibular midbody areas

34. ROTATIONAL INSERTION PATHS Undercuts necessitate adopting a rotational path of insertion: resists vertical displacement Inferior to the retromolar pad: posterior end placed first, from the superior & posterior before rotating the anterior segment down

35. ROTATIONAL INSERTION PATHS Anterior alveolus: anterior part inserted in a posterior & superior direction & posterior border rotated over the tuberosities More important when other retentive mechanisms are weak: Loss of normal anatomical contours Surgically created undercuts

36. PARALLEL WALLS Prominent alveolar ridges with parallel buccal & lingual walls increase the surface area maximize interfacial & atmospheric forces Limit the range of displacive force directions Flat ridges resist displacing forces perpendicular to the basal seat, but susceptible to movement parallel to it

37. GRAVITY Retentive force for the mandibular & displacive for the maxillary- when the person is upright Weight of the prosthesis- gravitational force insignificant Heavy maxillary prosthesis unseat if the other retentive forces – suboptimal

38. GRAVITY Increasing the weight of the mandibular denture- beneficial when other retentive factors are marginal Xerostomia patients prefer heavier maxillary prostheses

39. ADJUNCTIVE RETENTION THROUGH THE USE OF DENTURE ADHESIVES Commercially available nontoxic, soluble material that is applied to the tissue surface of the denture to enhance retention, stability& performance Products which enhance the treatment outcome US: 33% of denture wearers use adhesive products Sale exceeded 200 million$ in 2001

40. DENTURE ADHESIVES Dentists should: Educate all denture wearing patients about the advantages, disadvantages& uses of adhesives Identify those patients for whom such a product is advisable and/or necessary for a satisfactory denture wearing experience

41. DENTURE ADHESIVES STRICTLY INADVISABLE FORMS OF ADHESIVES Home reliner/repair kits Paper/cloth pads Self applied cushions Thin wafers of water soluble material: adherent to denture & basal tissue- don’t flow

42. DENTURE ADHESIVES Possible sequelae: Soft tissue damage Alterations in occlusal relations & VD Exacerbation alveolar bone destruction

43. DENTURE ADHESIVES- COMPONENTS & MECHANISM OF ACTION Augment the already operating retentive mechanisms Enhance retention through optimizing interfacial forces by: Increasing the adhesive & cohesive properties & viscosity of the interposed medium Eliminating the voids between the denture base & its basal seat

44. DENTURE ADHESIVES- COMPONENTS & MECHANISM OF ACTION Hydrated material formed by adhesives- stick readily to the tissue surface & the mucosal surface of the denture More cohesive than saliva- resists displacing pull Increases viscosity of saliva Hydrated material swells up in the presence of saliva/water: obliterates voids

45. DENTURE ADHESIVES- MATERIALS USED Before early 1960’s: VEGETABLE GUMS Karaya Tragacanth Xanthan Acacia Modest nonionic adhesion to denture & mucosa

46. DENTURE ADHESIVES- MATERIALS USED Drawbacks Very little cohesive strength Highly water soluble( particularly in hot ): washed out readily Allergic reactions- Karaya & methyl paraben (preservative) Acetic acid odor Short-lived & unsatisfactory adhesive performance

47. DENTURE ADHESIVES- MATERIALS USED Presently : SYNTHETIC MATERIALS Mixtures of the salts of short acting Carboxymethylcellulose (CMC) long acting (polyvinyl methyl ether maleate) ‘gantrez’ polymers

48. DENTURE ADHESIVES- MATERIALS USED CMC hydrates & displays quick-onset ionic adherence to both dentures& mucous epithelium Original fluid increases its viscosity & CMC increases in volume- eliminates voids between prosthesis & basal seat Enhance the interfacial forces acting on the denture

49. DENTURE ADHESIVES- MATERIALS USED Polyvinylpyrrolidone (‘povidone’) behaves like CMC Gantrez salts: More protracted time course than necessary for the onset of hydration than CMC, hydrate & increase adherence & viscosity

50. DENTURE ADHESIVES- MATERIALS USED Display molecular cross-linking  more pronounced & longer lived in Calcium- Zinc gantrez than in Calcium- Sodium gantrez All polymers fully solubilised & washed out by saliva : hastened by the presence of hot liquid

51. DENTURE ADHESIVES- MATERIALS USED OTHER COMPONENTS: Petrolatum, Mineral oil, Polyethylene oxide : bind the materials & make placement easier Silicone oxide, Calcium stearate: powders to minimize clumping Menthol, Peppermint oils: flavoring Red dye: Coloring Sodium borate, Methylparaben, Polyparaben: Preservatives

52. SUBJECTIVE & OBJECTIVE RESPONSES TO DENTURE ADHESIVE No reports of tissue reactions excepting uncommon allergic reactons to karaya / methyl paraben Earlier formulations had benzene- carcinogen Lessened inflammation of the underlying tissues if dental hygiene is maintained

53. SUBJECTIVE & OBJECTIVE RESPONSES TO DENTURE ADHESIVE Incisal bite force in well fitting dentures over well- keratinized ridges with favorable anatomical features Can be improved for well fitting dentures over inferior basal tissues

54. SUBJECTIVE & OBJECTIVE RESPONSES TO DENTURE ADHESIVE Frequency of dislodgement - chewing Increased confidence & security in chewing- but no improvement in chewing performance Improvement in chewing efficiency during adjustment to new dentures

55. SUBJECTIVE & OBJECTIVE RESPONSES TO DENTURE ADHESIVE OBJECTIONS: Grainy/ gritty texture of the powder Taste or sensation of semidissolved adhesive material that escapes from the posterior & other peripheries Difficulties in removing adhesives from the oral tissues & denture The cost of the material

56. DENTURE ADHESIVES- INDICATIONS Well made complete dentures do not satisfy a patient’s perceived retention & stability expectations Candidates for implant supported prosthesis , precluded by health, financial or other restraints

57. DENTURE ADHESIVES- INDICATIONS Salivary dysfunction Xerostomia- medications, irradiation, systemic disease, disease of salivary glands Need to be educated- deliberately moisten the adhesive bearing denture

58. DENTURE ADHESIVES- INDICATIONS Neurological disorders CVA- oral cavity insensitive to tactile stimulation/ paralysis of oral musculature Help to accommodate to new dentures Dentures fabricated before stroke

59. DENTURE ADHESIVES- INDICATIONS Orofacial Dyskinesia/ Tardive Dyskinesia Exaggerated, uncontrollable muscular actions of tongue, lips, cheeks & mandible Side effect of: - phenothiazines - neuroleptics - GI medications -Dopamine blocking drugs

60. DENTURE ADHESIVES- INDICATIONS Resective surgical/ traumatic modifications of the oral cavity Oral neoplasia Loss of integrity of intraoral structures Even in the presence of surgically created rotational undercuts

61. DENTURE ADHESIVES- CONTRAINDICATION Poorly fitting or improperly fabricated prosthesis Hypersensitivity to any of the components

62. DENTURE ADHESIVES- PATIENT EDUCATION Major information source to the patient- dentist Effects of powder formulations do not last long compared to cream formulations Initial ‘hold’ is better for them compared to cream s Easier to clean out The least amount of the material that is effective should be used: 0.5-1g/denture unit

63. DENTURE ADHESIVES- PATIENT EDUCATION POWDERS : Clean prosthesis moistened- thin even coat of adhesive sprayed onto the tissue surface of the denture Excess is shaken off & it is firmly seated Sprayed denture slightly moistened with water before insertion- inadequate salivation

64. DENTURE ADHESIVES- PATIENT EDUCATION CREAMS 2 approaches 1. Placement of thin beads of adhesive in the depth of the dried denture in the incisor & molar regions Anteroposterior bead in the midpalate- maxillary

65. DENTURE ADHESIVES- PATIENT EDUCATION 2. Small spots of cream placed at 5mm intervals throughout the fitting surface of the dried denture- even distribution Denture then seated & inserted firmly Requires moistening before placement in cases of xerostomia

66. DENTURE ADHESIVES- PATIENT EDUCATION Daily removal of the adhesive- soaking prosthesis in water / soaking solution overnight If not possible, running hot water over the tissue surface & scrubbing with a suitable hard bristle brush

67. DENTURE ADHESIVES- PATIENT EDUCATION Adhesive adherent to alveolar ridges & palate – rinsing with warm/ hot water- firmly wiping the area with gauze/washcloth saturated with hot water Discomfort will not be resolved by placing a ‘cushioning layer’ of adhesive under the denture

68. DENTURE ADHESIVES- PATIENT EDUCATION Professional management required: Pain /soreness Gradual increase in the quantity of adhesive required Patients recalled annually for mucosal evaluation& prosthesis assessment

69. DENTURE ADHESIVES-PROFESSIONAL ATTITUDE Frequently regarded as unesthetic, impedes dentist’s ability to appraise the health of oral tissues & the true adaptation Use of denture adhesive & residual ridge resorption- believed to be correlated: no scientific basis Reduce the amount of lateral movements that denture undergoes while in contact with basal tissues

70. DENTURE ADHESIVES-PROFESSIONAL ATTITUDE Patient may ignore the need for professional help when dentures actually become ill fitting Integral part of a professional service & their adjunctive benefits must be recognised

71. CONCLUSION Irrespective of the underlying reasons for the patient’s dissatisfaction with the prosthesis, dentist must realize that a patient’s judgement of the treatment outcome is what defines prosthodontic success Though complete denture retention is a complex phenomenon, it is every patient’s invariable need that the prosthesis stays firm & stable during function & hence every possible attempt should be made by the dentist to achieve it

72. BIBLIOGRAPHY Prosthodontic Treatment for Edentulous Patients- Zarb & Bolender,Twelfth edition Essentials of CompleteDenture Prosthodontics - Sheldon Winkler,Second edition Textbook of Prosthodontics - Deepak Nallaswamy Complete Denture Prosthodontics - John Joy Manappallil

73. THANK YOU!