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


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


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


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


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


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


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


Presently : SYNTHETIC MATERIALS

Mixtures of the salts of short acting Carboxymethylcellulose (CMC)

long acting (polyvinyl methyl ether maleate)

‘gantrez’ polymers


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


Polyvinylpyrrolidone (‘povidone’) behaves like CMC

Gantrez salts: More protracted time course than necessary for the onset of hydration than CMC,

hydrate & increase adherence & viscosity


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


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


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


Frequency of dislodgement - chewing Increased confidence & security in

chewing- but no improvement in chewing performance

Improvement in chewing efficiency during adjustment to new dentures


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


Salivary dysfunction Xerostomia- medications, irradiation,

systemic disease, disease of salivary glands

Need to be educated- deliberately moisten the adhesive bearing denture


Neurological disorders CVA- oral cavity insensitive to tactile

stimulation/ paralysis of oral musculature

Help to accommodate to new dentures Dentures fabricated before stroke


Orofacial Dyskinesia/ Tardive Dyskinesia Exaggerated, uncontrollable muscular

actions of tongue, lips, cheeks & mandible

Side effect of: - phenothiazines - neuroleptics - GI medications -Dopamine blocking drugs


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


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


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


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


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


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


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!

retention of complete dentures

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