Retention of complete dentures
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Transcript of Retention of complete dentures
RETENTION OF COMPLETE DENTURES
DEEPTHI P.R.FINAL YEAR BDS
CONTENTS
Introduction Definition Factors affecting retention - Classification - Interfacial force - Adhesion -Cohesion -Oral & facial musculature
CONTENTS
-Atmospheric Pressure -Undercuts, Rotational insertion paths,
Parallel walls -Gravity Denture Adhesives Conclusion Bibliography
INTRODUCTION
Success of treatment with CD
Integration of oral functions + psychological acceptance
Perception of the dentures as stationary during function
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
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
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
RETENTION
ANATOMICAL Size of the denture bearing areaQuality of the denture bearing areaParallel ridge walls
PHYSIOLOGICAL
Saliva
PHYSICALAdhesionCohesionInterfacial surface tensionCapillarityAtmospheric pressureGravity
MECHANICALUndercutsRetentive springsMagnetic forcesDenture adhesivesSuction chambers & discsPalatal implants
MUSCULAROral musculatureFacial musculature
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
DISLODGING FORCES
Mastication Adhesive food Gravity (upper) Surrounding musculature Occlusal prematurities Parafunctional habits
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’
INTERFACIAL FORCE
Interfacial surface tension Viscous tension
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
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
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
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
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
INTERFACIAL FORCE
INTERFACIAL VISCOUS TENSION Force holding two parallel plates
together that is due to viscosity of the interposed liquid
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)πkr4 V
h3
INTERFACIAL FORCE
Viscous force viscosity of the fluid
Viscous force thickness of the medium
Viscous force opposing surface area
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
ADHESION
‘Physical attraction of unlike molecules for each other’
IONIC FORCESSalivary glycoproteins
Acrylic resin in denture
base
Surface epithelium of the mucous membrane
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
GRAVITY
Increasing the weight of the mandibular denture- beneficial when other retentive factors are marginal
Xerostomia patients prefer heavier maxillary prostheses
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
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
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
DENTURE ADHESIVES
Possible sequelae: Soft tissue damage Alterations in occlusal relations & VD Exacerbation alveolar bone destruction
DENTURE ADHESIVES- COMPONENTS & MECHANISM OF ACTION
Augment the already operating retentive mechanisms
Enhance retention through optimizing interfacial forces by:
1. Increasing the adhesive & cohesive properties & viscosity of the interposed medium
2. Eliminating the voids between the denture base & its basal seat
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
DENTURE ADHESIVES- MATERIALS USED
Before early 1960’s: VEGETABLE GUMS
Karaya Tragacanth Xanthan Acacia Modest nonionic adhesion to denture &
mucosa
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
DENTURE ADHESIVES- MATERIALS USED
Presently : SYNTHETIC MATERIALS
Mixtures of the salts of short acting Carboxymethylcellulose (CMC)
long acting (polyvinyl methyl ether maleate)
‘gantrez’ polymers
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
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
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
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
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
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
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
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
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
DENTURE ADHESIVES- INDICATIONS
Salivary dysfunction Xerostomia- medications, irradiation,
systemic disease, disease of salivary glands
Need to be educated- deliberately moisten the adhesive bearing denture
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
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
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
DENTURE ADHESIVES- CONTRAINDICATION
Poorly fitting or improperly fabricated prosthesis
Hypersensitivity to any of the components
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 creams
Easier to clean out The least amount of the material that is
effective should be used: 0.5-1g/denture unit
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
DENTURE ADHESIVES- PATIENT EDUCATION
CREAMS2 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
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
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
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
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
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
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
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
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
THANK YOU!