denture base

7/27/2019 Denture Base

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Definition Requirements Functions Types

a,Plastic

b,Metal Tooth supported partial denture base Distal extension denture base Methods of attaching denture base Methods of attaching artificial teeth Relining Stress breakers



Definition –

Is that part of the removable partial denture which

rests on oral mucosa and to which teeth areattached.



•Accuracy of Adaptation To Tissues With Low Volume

Change

• Dense non irritating surface capable of receiving &maintaining a good finish.

• Thermal conductivity

• Low specific gravity – Lightness in mouth

• Esthetics

• Biologically Compactable with tissues



• Dimensional stability

• Resist deformation

• Low Cost

• Self cleansing

• Potential for future relining

• Sufficient strength – Resistance to fracture /distortion



Functions –

Esthetics Support and retain artificial teeth Assist in transfer of occlusal forces directly to

abutment teeth thru rests. Prevent vertical and horizontal migration of

remaining natural teeth. Eliminate undesirable food traps. Stimulates the underlying tissue.



Types –

Plastic

Acrylic

PolystyreneValplast

Metal

Gold

Co-CrTitanium

Vitallium



Tooth supported partial dentures

Inadequate interarch space

Structural details

Designed with optimum extension

Thinner base than plastic resin

Avoid sharp margins



• Accuracy & performance of form

• Comparative tissue response

• Thermal conductivity

• Weight & Bulk



Accuracy and permanence of form-

Cast more accurately than denture resins andmaintain their accuracy of form without change in

mouth. Internal strains released later to cause distortion

not present. Need for an additional pps eliminated entirely. Accuracy –metal base provides intimacy of

contact-retention of denture prostheses. Such intimacy-not acrylic resin bases.



Comparitive tissue response-

Inherent cleanliness of cast metal basecontributes to health of oral tissue.

Bacteriostatic activity – ionization and oxidizationof metal base.

Metal base naturally cleaner than an acrylic resinbase.



Thermal conductivity-

Temperature changes transmitted though metalto the underlying help to maintain health of that

tissue. Pts acceptance. Denture resins – insulating property



Weight and bulk-

Metal alloy may be cast thinner than acrylic resinand still have adequate strength.

Certain situations demands use of acrylic denturebase-

Xtreme loss of residual alveolar bone-fullness to

denturebase to restore facial contours. To provide fullness to fill a max vestibule Esthetics



• Esthetics

• Enhancement of retention not possible – lack of weightof metal base

• Relining difficult

• Restoration of normal facial contour can not beachieved



Acrylic denture base- Indications

Extension base partial denture

Long span edentulous ridges

Relining

Contour restoration



Adequate bulk & strength - junction of base & minorconnector

Tissue stops at extension base frame work

Placement of Base –

Placement over crest ridge- Resin breakage

Buccal/lingual of crest ridge



1950,s Valplast – flexible base resin ideal for partial

dentures. Esthetic yet fully functional alternative to

traditional cast metal based removable partialdentures.



Biocompatible nylon and thermoplastic resin-flexibilityand stability.

Color, shape and design of valplast partials blend

seamlessly with natural appearance of gingiva makingprostheses nearly invisible.

Strenght of valplast resin doesn’t require a metal

framework-eliminates metallic taste.

Enables partial to be fabricated thin enough with nonmetallic clasps.



Adequate occlusal clearance b/w arches for toothplacement.

No tooth preparation required.

Vitallium combination-better support and claspesthetics



TYPES

Tooth Supported Partial Denture Base

Distal Extension Partial Denture Base



In tooth supported prostheses denture base isprimarily a span b/w 2 abutments supportingartificial teeth.

Occlusal forces transferred to abutments-Rests.

Prevent horizontal migration of all abutmentteeth in partially edentulous arch and vertical

migration of teeth in opposing arch.



Support of the denture. Support critical to goal of minimizing functional

movt and improving prostheses stability. Max support obtained – broad accurate denture

bases-occlusal load equitably. Support – gross size and cellular characteristics of

residual alveolar ridge. Snow shoe principle-broad coverage furnishes the

best support with least load per unit area isprinciple choice for providing max support. Support –primary consideration



Esthetics,stimulation of underlying tissue,and oralcleanliness-secondary importance.

Relining necessary in tooth supported denturebase.

Tooth – supported bases made soon after xnshould be of material that permits relining.

Primary retention for RPD –mechanically byplacing retaining elements on abutment teeth.

Secondary retention-intimate relationship of denture base and major connectors.



Retention of denture bases as a result of followingforces-

Adhesion –attraction of saliva to denture andtissue.

Cohesion –attraction of molecules of saliva foreach other.

Atmospheric pressure-border seal. Physiological molding of tissue around polished

surface of the denture. Effect of gravity on mandibular denture.



Acrylic resin bases-attached to partial dentureframe work-minor connector designed b/wframework and underlying tissue.

Relief 20 guage thickness-basal seat.

Plastic mesh patterns in forming retentiveframework less satisfactory than open pattern.



12-14 guage half round wax and 18 guage roundwax-ladder like framework rather than meshpattern.

Designing retentive framework –bucally lingually-

strengthen acrylic resin base-minimize distortion of base-stress

Not interfere with teeth arrangement-futureadjustment



Metal bases –cast as integral parts of partialdenture framework.

May also be assembled and attached toframework with acrylic resin.



Plastic Mesh Pattern

Open Lattice



BEADS & NAIL HEADS



• Porcelain/ Resin Artificial Teeth with Resin

• Porcelain/ Resin Tube Teeth & Facings CementedDirectly to Metal Bases

• Resin Teeth Processed Directly To Metal Bases

• Metal Teeth Cast With Frame Work

• Chemical Bond



Mechanically retained. Posterior teeth retained by acrylic resin in their

diatoric holes. Ant teeth retained by acrylic surrounding their

lingually placed retention pins. Acrylic resin teeth retained by chemical union

with acrylic resin of denture base.



Attachment of acrylic resin to metal base – nail headretention,retention loops or diagonal spurs.

Any junction of acrylic resin with metal should be at anundercut finish line.(mech retention)

Every attempt should be made to prevent separation and

seepage which results in discoloration and uncleanliness. Denture odors are frequently caused by accretions at the

junction of acrylic resin with metal. Separation occurring b/w acrylic resin and metal can

eventually lead to some loosening of acrylic resin base.



Some disadv of this type of attachment are- Difficulties in obtaining satisfactory occlusion. Lack of adequate contours for functional tongue and

cheek contact. Unesthetic display of metal at gingival margins.



Modification of this method is attachment of ready made acrylic resin teeth to the metal basewith acrylic resin of same shade(pressing).

Particularly applicable for ant replacements.



Procedure- Labial index of the position of teeth is made. Lingual portion cut away or post hole prepared. Subsequently tooth is attached to denture with

acrylic resin of same shade. For best occlusal relation jaw relation records

made with denture casting in mouth. Tube teeth preferred.

Teeth are ground to fit the ridge with sufficientclearance beneath for metal base.

Casting completed and tried. Teeth ground to harmonious occlusion.



Occlusal relation established in mouth and transferred toarticulator.

Teeth can be carved or processed in acrylic resin of propershade.

Long,short,wide or narrow teeth may be created when

necessary to fill spaces. Occlusion on acrylic resin teeth may be restablished to

compensate for wear or settling by reprocessing newacrylic resin or using light activated acrylic resin.



Occasionally a second molar tooth may be replaced as partof partial denture casting.

Space too limited for attachment of an artificial tooth. Because metal particularly a chrome alloy is abrasion

resistant area of occlusal contact should be held to min to

prevent damage to peridontium of opposing tooth. Should be used only to fill a space and to prevent tooth

extrusion.



Recent developments-direct chemical bonding of acrylic resin to metal frame works.

Investing alveolar and gingival tissuereplacement components can be attached

without the use of loops,mesh or surfacemechanical locks. Section of metal framework-roughned with

abrasives-treated with vaoporized silica. Acrylic resin bonding agent applied-thin layer of

acrylic resin.



Triochemical coating accomplishes a second method of fusing a microscopic layer of ceramic to metal.

Sandblasting metal framework with silica particle(Rocatec-plus).

Silane added to ceramic-chemical bond b/w silicatelayer and denture base acrylic resin.

Denture base acrylic resins formulated with 4-Meta are

also available and provide mechanism of bondingacrylic resin to metal.



Distal extension base differs from toothsupportedbase-made of material-relined.

Acrylic resin denture base materials that can berelined are generally used.



Loss of support - distal extension bases- changesin residual ridge-loss of occlusion-heavy occlusalcontact b/w remaining natural teeth.

Relining necessary.

Rotation of fulcrum line with indirect retainerslifting from their seats as distal extension base ispressed against ridge tissue-relining



Loss of occlusal contact and rotation-relining.

Loss of occlusal contact with no evidence of rotation -restablish occlusion.

Loss of support assessed clinically-hydrocolloid,wax,tissue conditioning material.



Acrylic resin bases – distal extensions

Min and harmonious occlusion,and accuracy withwhich base fits the underlying tissue influences

trauma occuring under function.

Absence of trauma-ridge integrity.



Best indication for metal distal extension bases-ridge

that supported a previous partial denture.

Tissues remain healthier beneath a metal base than aacrylic resin base –thorough Rx planning-pt education-

care of denture bases.

Highest pressure was on the residual ridge crest. The pressure

distribution varied along with the design of the occlusal rest.

“Development of in vivo measuring system of the pressure distribution under thedenture base of removable partial denture. J Prosthodont Res. 2009 Jan;53(1):15-21”



In distal extension situations-rigid connection b/wdenture base and supporting teeth account forthe base movt without causing tooth or tissuedamage.

Stress on abutment teeth and residual ridgeminimised-broad coverage,harmoniousocclusion,direct retainers.



2 types of clasp assembly-distal extensions-stressbreaking design.

Retentive clasp arms-engage undercuts onabutment tooth-tissueward movt- min leverage to

abutment. Tapered,wrought wire retentive clasp-flexibility. Act as stressbreaker b/w denture base and

abutment tooth.

Another concept of stress breaking-separatingaction of retaining elements from denture base



Stress breakers effectively dissipate verticalstresses.

It is the rigid nature of conventional RPD thatallows satisfaction of requirements of

support,stability and retention.



Carr A B, Mc Givney G P, Brown D T, Major connector inMcCraken’s Removable partial Prothodontics. 11th ed, stlouis: Mosby; 2008

Stewart K L, Rudd K D, Kuebker W A, Major connector in

Stewart’s Clinical Removable Partial Prosthodontics. 2nd

,Chennai; 2004

Miller E L, Grasso J E, Major connector in Removable PartialProsthodontics. 2nded, Baltimore: Williams & Wilkins; 1979

Development of in vivo measuring system of the pressuredistribution under the denture base of removable partialdenture. J Prosthodont Res. 2009 Jan;53(1):15-21

denture base

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