Denture base considerations/certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY
Leader in continuing Dental EducationLeader in continuing Dental Education
www.indiandentalacademy.comwww.indiandentalacademy.com

DENTURE BASEDENTURE BASE
CONSIDERATIONSCONSIDERATIONS
Functions of denture bases:Functions of denture bases:
 To support artificial teeth and effect the transfer of occlusal forces toTo support artificial teeth and effect the transfer of occlusal forces to
supporting oral structures.supporting oral structures.
 Cosmetic effect{Esthetics.}Cosmetic effect{Esthetics.}
 Stimulation, by massage, of the underlying tissues of the residual ridge.Stimulation, by massage, of the underlying tissues of the residual ridge.
 It is clearly evident that oral tissues placed under functional stress withinIt is clearly evident that oral tissues placed under functional stress within
their physiologic tilerence maintain their form and tone better than tissuestheir physiologic tilerence maintain their form and tone better than tissues
suffering from disuse.suffering from disuse.
 Partial denture base is divided into:Partial denture base is divided into:
 Tooth –supported partial denture base .Tooth –supported partial denture base .
 Distal extension partial denture base.Distal extension partial denture base.
 Tooth supported partial denture base:Tooth supported partial denture base:
 It is primarily a span between two abutments supporting artificial occlusalIt is primarily a span between two abutments supporting artificial occlusal
surfaces.surfaces.
 Thus occlusal forces are transferred directly to the abutment teeth throughThus occlusal forces are transferred directly to the abutment teeth through
rests.rests.
 It prevents horizontal migration of the teeth in the partial edentulous arch.It prevents horizontal migration of the teeth in the partial edentulous arch.
 It also prevents vertical migration of the teeth in the opposing arch.It also prevents vertical migration of the teeth in the opposing arch.

Distal extension partial denture bases :Distal extension partial denture bases :
 Close to the terminal abutment only a framework supportingClose to the terminal abutment only a framework supporting
occlusal surface is necessary.occlusal surface is necessary.
 Support from the underlying ridge tissues is very important.Support from the underlying ridge tissues is very important.
 Maximum support is obtained by using broad accurate dentureMaximum support is obtained by using broad accurate denture
bases, which spread the occlusal load equitably over the entire areabases, which spread the occlusal load equitably over the entire area
available for support.available for support.
 Support should be of primary important in selecting , designing &Support should be of primary important in selecting , designing &
fabricating distal extension partial denture base.fabricating distal extension partial denture base.
 Future relining or rebasing may not be necessary to reestablishFuture relining or rebasing may not be necessary to reestablish
support in the tooth-supported base as it has an abutment tooth atsupport in the tooth-supported base as it has an abutment tooth at
each end.each end.
 In distal extension denture base , future relining or rebasing may beIn distal extension denture base , future relining or rebasing may be
required as the changes may occur beneath the tooth-borne baserequired as the changes may occur beneath the tooth-borne base
to the point that poor esthetics and accumulation of debris mayto the point that poor esthetics and accumulation of debris may
result.result.

 Methods of Attaching Denture Bases :Methods of Attaching Denture Bases :
 Resin bases are attached to the partial denture framework by means of aResin bases are attached to the partial denture framework by means of a
minor connector designed so that a space exists between it and underlyingminor connector designed so that a space exists between it and underlying
tissues of the residual ridge.tissues of the residual ridge.
 Relief at least a 20 gauge thickness over basal seat areas of master cast isRelief at least a 20 gauge thickness over basal seat areas of master cast is
used to create raised platform on the investment cast.used to create raised platform on the investment cast.
 Thus after casting the portion of retentive framework to which the resin baseThus after casting the portion of retentive framework to which the resin base
will be attached will stand away from the tissue surface sufficiently to permitwill be attached will stand away from the tissue surface sufficiently to permit
a flow of resin base material beneath the surface.a flow of resin base material beneath the surface.
 The retentive framework for the base should be embedded in the baseThe retentive framework for the base should be embedded in the base
material with sufficient thickness of resin. (1-5mm).material with sufficient thickness of resin. (1-5mm).
 Thickness of the resin is essential during the dentureThickness of the resin is essential during the denture
adjustments or during relining procedures also to avoidadjustments or during relining procedures also to avoid
weakness and subsequent fracture of resin base materials.weakness and subsequent fracture of resin base materials.
 Metal bases are usually cast as integral parts of partial denture framework.Metal bases are usually cast as integral parts of partial denture framework.

 Ideal Denture Base :Ideal Denture Base :
 Requirements:Requirements:
 Accuracy of adaptation to the tissue with low volume change.Accuracy of adaptation to the tissue with low volume change.
 Dense, nonirritating surface capable of receiving and maintainingDense, nonirritating surface capable of receiving and maintaining
good finish.good finish.
 Thermal conductivity.Thermal conductivity.
 Low specific gravity; lightness in the mouth.Low specific gravity; lightness in the mouth.
 Sufficient strength; resistance to fracture or distortion.Sufficient strength; resistance to fracture or distortion.
 Self-cleansing factor or easily kept clean.Self-cleansing factor or easily kept clean.
 Esthetic acceptabilityEsthetic acceptability
 Potential for Future reliningPotential for Future relining
 Low initial cost.Low initial cost.

Advantages of Metal Bases over Resin Bases:Advantages of Metal Bases over Resin Bases:
 Except for those edentulous ridges with recent extractions metal isExcept for those edentulous ridges with recent extractions metal is
preferred to resin for tooth supported bases for its several advantages. Thepreferred to resin for tooth supported bases for its several advantages. The
stimulation that it gives to the underlying tissues is so beneficial that it probablystimulation that it gives to the underlying tissues is so beneficial that it probably
prevents some alveolar atrophy. Some of the advantages of a metal base areprevents some alveolar atrophy. Some of the advantages of a metal base are
discussed in the following paragraphs below.discussed in the following paragraphs below.
 Accuracy and permanence form:Accuracy and permanence form:
Cast metal bases whether of gold or chrome alloys not may be cast more accuratelyCast metal bases whether of gold or chrome alloys not may be cast more accurately
than denture base resins but also maintain their accuracy of form without change thethan denture base resins but also maintain their accuracy of form without change the
mouth.mouth.
 Comparative tissue response:Comparative tissue response:
Clinical observations have demonstrated that the inherent cleanliness of the castClinical observations have demonstrated that the inherent cleanliness of the cast
metal base contributes to the health of oral tissues when compared to an acrylic resinmetal base contributes to the health of oral tissues when compared to an acrylic resin
base.base.
 Thermal conductivity:Thermal conductivity:
Thermal changes are transmitted through the metal base to the underlying tissues,Thermal changes are transmitted through the metal base to the underlying tissues,
thereby helping to maintain the health of those tissues. Conversely, denture resinsthereby helping to maintain the health of those tissues. Conversely, denture resins
have insulting properties that prevent interchange of temperature between the insidehave insulting properties that prevent interchange of temperature between the inside
and the outside of the denture baseand the outside of the denture base

 Weight and bulk:Weight and bulk:
Metal alloy may be cast much thinner than resinMetal alloy may be cast much thinner than resin
and still have adequate strength and rigidity.and still have adequate strength and rigidity.
- Cobalt chrome alloys- Cobalt chrome alloys→→less weight &bulk.less weight &bulk.
- Cast gold- Cast gold →→slight more bulk to provide rigidity.slight more bulk to provide rigidity.
→→ Denture base contours for functional tongueDenture base contours for functional tongue
and cheek contact can best be accomplishedand cheek contact can best be accomplished
with resin base.with resin base.
→→ Esthetics is best achieved with resin base.Esthetics is best achieved with resin base.
→→ The principal disadvantage of metal bases isThe principal disadvantage of metal bases is
that it can be relined only with difficulty, if at all.that it can be relined only with difficulty, if at all.

Methods of Attaching Artificial Teeth:Methods of Attaching Artificial Teeth:
 Artificial teeth may be attached to denture bases by several means such as;Artificial teeth may be attached to denture bases by several means such as;
 With acrylic resin.With acrylic resin.
 Cemented.Cemented.
 Processed directly to metal.Processed directly to metal.
 Cast with frameworkCast with framework
 Chemical bond.Chemical bond.
Porcelain or resin artificial teeth attached with resinPorcelain or resin artificial teeth attached with resin..
 Porcelain teeth are mechanically retained.Porcelain teeth are mechanically retained.
 Posterior teeth are attached retained by acrylic resin in their diatonic holes.Posterior teeth are attached retained by acrylic resin in their diatonic holes.
 Anterior porcelain teeth are retained by acrylic resin surrounding the lingually placed retentionAnterior porcelain teeth are retained by acrylic resin surrounding the lingually placed retention
pins.pins.
 Resin teeth are retained by chemical union of the acrylic resin of denture base.Resin teeth are retained by chemical union of the acrylic resin of denture base.
 Attachment of resin to the metal base may be accomplished by nail head retention, retentionAttachment of resin to the metal base may be accomplished by nail head retention, retention
loop, or diagonal spurs placed at random.loop, or diagonal spurs placed at random.
 Any junction of resin with metal should be at an undercut finishing line or associated with someAny junction of resin with metal should be at an undercut finishing line or associated with some
retentive undercutretentive undercut

Porcelain or resin tube teeth and facings cemented directly to metal basesPorcelain or resin tube teeth and facings cemented directly to metal bases::
 Attachment of readymade resin teeth to the metal base with acrylic resin of sameAttachment of readymade resin teeth to the metal base with acrylic resin of same
shade. This is called pressing on a resin tooth.shade. This is called pressing on a resin tooth.
 It is particularly applicable to anterior replacements.It is particularly applicable to anterior replacements.
 After a labial index of the position of the teeth is made. The lingual portion of theAfter a labial index of the position of the teeth is made. The lingual portion of the
tooth may be cut away or a posthole is prepared in the tooth for retention on thetooth may be cut away or a posthole is prepared in the tooth for retention on the
casting.casting.
 Subsequently the tooth is attached to the denture with acrylic resin of the sameSubsequently the tooth is attached to the denture with acrylic resin of the same
shade.shade.
 Since this is done under pressure, the acrylic attachment provides hardness andSince this is done under pressure, the acrylic attachment provides hardness and
strength.strength.
 Some disadvantages of this type of attachment are the difficulties in obtainingSome disadvantages of this type of attachment are the difficulties in obtaining
satisfactory occlusion, lack of adequate contours for functional tongue and cheeksatisfactory occlusion, lack of adequate contours for functional tongue and cheek
contact and unaesthetic display of metal at gingival margins.contact and unaesthetic display of metal at gingival margins.
 This can be avoided when the tooth is butted directly to the ridge. and by selectingThis can be avoided when the tooth is butted directly to the ridge. and by selecting
tube teeth for width but with occlusal surfaces slightly higher than required.tube teeth for width but with occlusal surfaces slightly higher than required.

Resin teeth processed directly to metal basesResin teeth processed directly to metal bases::
 Occlusion may be created without restoring to the modification of readymade artificialOcclusion may be created without restoring to the modification of readymade artificial
teeth.teeth.
 Recesses in the denture pattern are either carried by hand created or manufacturedRecesses in the denture pattern are either carried by hand created or manufactured
teeth that are only used to form recess in the pattern.teeth that are only used to form recess in the pattern.
 Occlusal relationship may be established on articulator and in the mouth and then theOcclusal relationship may be established on articulator and in the mouth and then the
teeth are carried and processed in acrylic resin of proper shade.teeth are carried and processed in acrylic resin of proper shade.
Metal teethMetal teeth
 Occasionally a second molar tooth may be repaired as part of partial denture casting.Occasionally a second molar tooth may be repaired as part of partial denture casting.
 This is usually done when space is too limited for the attachment of an artificial toothThis is usually done when space is too limited for the attachment of an artificial tooth
and yet the addition of second molar is desirable to prevent migration of an opposingand yet the addition of second molar is desirable to prevent migration of an opposing
second molar .second molar .
 Before casting occlusal surface should be waxed properly and the area of occlusalBefore casting occlusal surface should be waxed properly and the area of occlusal
contact should be held minimum the avoid damage to the periodontium of opposingcontact should be held minimum the avoid damage to the periodontium of opposing
tooth and the associated discomfort to the patient.tooth and the associated discomfort to the patient.
 They should be used only to fill a space and to prevent tooth migration and no moreThey should be used only to fill a space and to prevent tooth migration and no more
as they are difficult to adjust and objectionally hard for use as occlusal surface.as they are difficult to adjust and objectionally hard for use as occlusal surface.

Chemical bond:Chemical bond:
 Recent developments in resin bonding have provided a means of directRecent developments in resin bonding have provided a means of direct
chemical bonding of acrylic resinto metal frameworks.chemical bonding of acrylic resinto metal frameworks.
 Sections of a metal framework that are to support for replacement teeth canSections of a metal framework that are to support for replacement teeth can
be roughened with abrasives,then treated with a vaporised silica coating.be roughened with abrasives,then treated with a vaporised silica coating.
 Upon which a resin bonding agent is applied ,for later attachment ofUpon which a resin bonding agent is applied ,for later attachment of
replacement of resin teeth or for processing of acrylic resin tissuereplacement of resin teeth or for processing of acrylic resin tissue
replacements.replacements.

 Need for Relining:Need for Relining:
 The distal extension base differs form the tooth borne base universalThe distal extension base differs form the tooth borne base universal
aspects, one of which is that it must be made of a material that can beaspects, one of which is that it must be made of a material that can be
relined or rebased when it becomes necessary to reestablish tissue.relined or rebased when it becomes necessary to reestablish tissue.
 Support for distal extension base :Support for distal extension base :
 Therefore resin for denture base materials that can be relined are generallyTherefore resin for denture base materials that can be relined are generally
used.used.
 Loss of support for a distal extension base results form changes in residualLoss of support for a distal extension base results form changes in residual
ridge form over a period of the time.ridge form over a period of the time.
 Loss of support for distal extension base will;Loss of support for distal extension base will;
 Result in loss of occlusal contact between the prosthetically supplied teethResult in loss of occlusal contact between the prosthetically supplied teeth
and opposing dentition and a return to heavy occlusal contact between theand opposing dentition and a return to heavy occlusal contact between the
remaining natural teeth.remaining natural teeth.
 If evidence of rotation about the fulcrum line with the indirect retainers liftingIf evidence of rotation about the fulcrum line with the indirect retainers lifting
from their seats as the distal extension base pressed against the ridgefrom their seats as the distal extension base pressed against the ridge
tissues.tissues.

SummarySummary

ReferencesReferences
 Mc Cracken’s : Removable partialMc Cracken’s : Removable partial
proathodontics, Mosby. 8proathodontics, Mosby. 8thth
edition.edition.
 Miller Earnest L : Removable partialMiller Earnest L : Removable partial
prosthodontics, 2prosthodontics, 2ndnd
edition.edition.
 Russel J. Strattton and Frank J. Wiebelt :Russel J. Strattton and Frank J. Wiebelt :
An atlas of removable partial dentureAn atlas of removable partial denture
design.design.

Denture base considerations/certified fixed orthodontic courses by Indian dental academy

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