Role of Component Parts in Cast Partial Dentures

Role of component partsRole of component parts
of cast partial denturesof cast partial dentures
INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY
Leader in continuing Dental EducationLeader in continuing Dental Education
www.indiandentalacademy.com

Component PartsComponent Parts
1)1) Major connectorMajor connector
2)2) Minor connectorMinor connector
3)3) Occlusal restsOcclusal rests
4)4) Direct retainerDirect retainer
armarm
5)5) Stabilizing orStabilizing or
reciprocalreciprocal
componentcomponent
6)6) Indirect retainerIndirect retainer

Component partsComponent parts
 Major ConnectorsMajor Connectors
 Minor connectorsMinor connectors
 RestsRests
 Indirect retainersIndirect retainers
 Denture bases & artificial teethDenture bases & artificial teeth
 Direct retainersDirect retainers

Major ConnectorsMajor Connectors
 Connects parts of theConnects parts of the
Prostheses locatedProstheses located
on one side of theon one side of the
arch to those on thearch to those on the
opposite sideopposite side
 All other parts of theAll other parts of the
PD are attached to itPD are attached to it
either directly oreither directly or
indirectly.indirectly.

REQUIREMENTSREQUIREMENTS
All major connectors must beAll major connectors must be
 be rigidbe rigid
 provide vertical support and protect the softprovide vertical support and protect the soft
tissuestissues
 provide a means of obtaining indirectprovide a means of obtaining indirect retentionretention
where indicatedwhere indicated

 Provide an opportunity of positioningProvide an opportunity of positioning
denture bases where needed.denture bases where needed.
 Maintain patient comfort.Maintain patient comfort.
 Not create food entrapment areas, as farNot create food entrapment areas, as far
as possible self cleansing.as possible self cleansing.

 Should not interfere with and is notShould not interfere with and is not
irritating to the tongue.irritating to the tongue.
 Should not impinge on oral tissues whenShould not impinge on oral tissues when
the restoration is placed, removed orthe restoration is placed, removed or
rotates in function.rotates in function.
 Covers no more tissues than isCovers no more tissues than is
absolutely necessary.absolutely necessary.

Maxillary Major ConnectorsMaxillary Major Connectors
 Palatal BarPalatal Bar
 Palatal StrapPalatal Strap
 A-P Bar/strap, closed horseshoeA-P Bar/strap, closed horseshoe
 Horse shoe/ U shaped connectorHorse shoe/ U shaped connector
 Palatal platePalatal plate

Palatal BarPalatal Bar
 Narrow half-oval barNarrow half-oval bar
 Mainly used asMainly used as
interim pd nowinterim pd now
 Bulky, difficult for ptBulky, difficult for pt
 Limited to replacingLimited to replacing
one/two teeth onone/two teeth on
either side of archeither side of arch
 Not placed ant toNot placed ant to
IIpmIIpm
 Only in Cl.3 archOnly in Cl.3 arch

Palatal strapPalatal strap
 Most widely usedMost widely used
 Not less than 8mmNot less than 8mm
widewide
 Width increases withWidth increases with
edentulous spanedentulous span
 More rigid with lessMore rigid with less
bulkbulk
 Ant border- Post toAnt border- Post to
rugae/valleyrugae/valley
 Cl.3 arches, rarelyCl.3 arches, rarely
Cl.2, never in Cl.1 &Cl.2, never in Cl.1 &
44

A-P Palatal BarA-P Palatal Bar
 Excellent rigidity,Excellent rigidity,
strong L-beam effectstrong L-beam effect
 Used in Cl.2 & 4Used in Cl.2 & 4
frequently, also Cl.1 &frequently, also Cl.1 &
33
 Provides less support,Provides less support,
completely dependantcompletely dependant
on remaining teethon remaining teeth
 Used when ant & postUsed when ant & post
abutments are widelyabutments are widely
separatedseparated

A-P Palatal BarA-P Palatal Bar
 Indicated in pts withIndicated in pts with
large palatal toruslarge palatal torus
where surgery iswhere surgery is
ruled outruled out
 Contraindicated inContraindicated in
high narrow vault-high narrow vault-
phoneticsphonetics
 Not first choiceNot first choice
connectorconnector

Closed horse-shoeClosed horse-shoe
A-P Palatal StrapA-P Palatal Strap
 Better support thanBetter support than
A-P BarA-P Bar
Indicated in Cl.1 & 2Indicated in Cl.1 & 2
arches where morearches where more
teeth to be replacedteeth to be replaced
ToriTori

Horse-shoe/ U shaped connectorHorse-shoe/ U shaped connector
 Borders must be 6mmBorders must be 6mm
from ging. margin/from ging. margin/
extend onto ling surfextend onto ling surf
 Lateral bordersLateral borders
should be at jnshould be at jn
horizontal & verticalhorizontal & vertical
slopesslopes
 SymmetricSymmetric
 Cl. 4Cl. 4
 Hard palatal sutureHard palatal suture
line & inoperable toriline & inoperable tori
 Less rigid, not usedLess rigid, not used
in Cl.1 & 2.in Cl.1 & 2.

PALATAL PLATE TYPEPALATAL PLATE TYPE
CONNECTORCONNECTOR
INDICATIONSINDICATIONS
 In most situations inIn most situations in
which only some or allwhich only some or all
anterior teeth remainanterior teeth remain
 Class II arch with a largeClass II arch with a large
posterior modificationposterior modification
space and some missingspace and some missing
anterior teethanterior teeth

Palatal platePalatal plate
 Ultimate rigidity & support, coveringUltimate rigidity & support, covering
half/more of hard palatehalf/more of hard palate
 Post border – jn of hard & soft palatePost border – jn of hard & soft palate
 Ant border – 6mm from marginal gingiva/Ant border – 6mm from marginal gingiva/
cover cingulacover cingula
 Cl.1 & Cl.2 with modificationsCl.1 & Cl.2 with modifications
 Heavy occl forces , flat/flabby ridges,Heavy occl forces , flat/flabby ridges,
shallow vault, transition to CD, cleft ptsshallow vault, transition to CD, cleft pts
 Disadv- Extensive coverage-soft tissueDisadv- Extensive coverage-soft tissue
reaction-inadequate oral hygienereaction-inadequate oral hygiene

BeadingBeading
Denotes scribing of aDenotes scribing of a
shallow groove on theshallow groove on the
maxillary master castmaxillary master cast
outlining the palataloutlining the palatal
major connectormajor connector
exclusive of rugaeexclusive of rugae
areas.areas.
Depth & width of 0.5 toDepth & width of 0.5 to
1mm1mm
Fades out 6mm fromFades out 6mm from
Gingival marginGingival margin

Purpose of beadingPurpose of beading
1) To transfer the major1) To transfer the major
connector design toconnector design to
the investment castthe investment cast

2) To provide a visible2) To provide a visible
finish line for thefinish line for the
castingcasting
3) To ensure intimate3) To ensure intimate
tissue contact of thetissue contact of the
major connector withmajor connector with
selected palatalselected palatal
tissuetissue
4) Prevents food debris4) Prevents food debris
under the connectorunder the connector
5) Enhances retention5) Enhances retention
& stability& stability

Summary of IndicationsSummary of Indications
 Perio support of remaining teeth weak –Perio support of remaining teeth weak – PalatalPalatal
plateplate
 Good perio support –Good perio support – Palatal strap/A-P barPalatal strap/A-P bar
 Long distal extn bases –Long distal extn bases – Complete palatalComplete palatal
plate/ closed horseshoeplate/ closed horseshoe
 Cl. 4 –Cl. 4 – Horseshoe, Closed horseshoe, completeHorseshoe, Closed horseshoe, complete
palatepalate depending on no. & location of postdepending on no. & location of post
missing teeth, support of rem. Teeth, andmissing teeth, support of rem. Teeth, and
opposing occlusionopposing occlusion
 Inoperable torus –Inoperable torus – Horseshoe, closed, A-P BarHorseshoe, closed, A-P Bar
 Single palatal bar rarely indicated.Single palatal bar rarely indicated.

MandibularMandibular
 Lingual barLingual bar
 Lingual plateLingual plate
 Double lingual bar/ Kennedy barDouble lingual bar/ Kennedy bar
 Labial barLabial bar

STRUCTURALSTRUCTURAL
REQUIREMENTSREQUIREMENTS
1.1. Long and relatively narrow because of spaceLong and relatively narrow because of space
limitationslimitations
2.2. Rigidity without addition of bulkRigidity without addition of bulk
3.3. Relief should be provided . Amount of reliefRelief should be provided . Amount of relief
depends on type of connector.depends on type of connector.
4.4. Beading is never indicated.Beading is never indicated.

Lingual barLingual bar
 Most frequently used, half pear shapedMost frequently used, half pear shaped
 Atleast 8mm space requiredAtleast 8mm space required

Lingual BarLingual Bar
 Half pear shaped with bulkiest portionHalf pear shaped with bulkiest portion
inferiorly located.inferiorly located.
 Superior border tapered to soft tissue,Superior border tapered to soft tissue,
located 4 mm inferior to gingivallocated 4 mm inferior to gingival
margins.margins.
 Inferior border located at the asertainedInferior border located at the asertained
height of the alveolar lingual sulcusheight of the alveolar lingual sulcus
when the patients tongue is elevated .when the patients tongue is elevated .

Sublingual barSublingual bar
Used when the height of floor of the mouth inUsed when the height of floor of the mouth in
relation to the free gingival margins is lessrelation to the free gingival margins is less
than 6mm.than 6mm.
 Inferior border at height of lingual sulcus.Inferior border at height of lingual sulcus.

LinguoplateLinguoplate
Pear shaped lingual bar with metal extending
onto lingual tooth surface

LingouplateLingouplate
 Adequate blockout &Adequate blockout &
relief under MCrelief under MC
 Superior borderSuperior border
placed above cingulaplaced above cingula
to close space uptoto close space upto
contact pointscontact points
 Always supported byAlways supported by
a rest located noa rest located no
further than mesialfurther than mesial
fossa of 1fossa of 1stst
premolarpremolar

Lingouplate - IndicationsLingouplate - Indications
When lingual frenum is high / space available
for lingual bar is limited (Min 8mm)

 In Cl. 1, where residual ridges haveIn Cl. 1, where residual ridges have
undergone excessive vertical resorptionundergone excessive vertical resorption
 Stabilizing periodontally weakened teethStabilizing periodontally weakened teeth
 Mandibular toriMandibular tori
 Lingoplate mod with incisal rests toLingoplate mod with incisal rests to
prevent mand. ant teeth fromprevent mand. ant teeth from
supraeruption in retrognathia & deep bitesupraeruption in retrognathia & deep bite
 Future replacement of one/more anteriorFuture replacement of one/more anterior
teeth will be facilitated by addition onteeth will be facilitated by addition on
retention loopsretention loops

DisadvantagesDisadvantages
 Extensive coverage may lead toExtensive coverage may lead to
decalcification of enamel surfaces ordecalcification of enamel surfaces or
irritation of soft tissue with poor oralirritation of soft tissue with poor oral
hygienehygiene

Double lingual/ Kennedy BarDouble lingual/ Kennedy Bar
 Lingual bar withLingual bar with
continuous barcontinuous bar
retainerretainer
 Axial alignment of antAxial alignment of ant
teeth such thatteeth such that
excessive blockout ofexcessive blockout of
interproximalinterproximal
undercuts ifundercuts if
liguoplate is usedliguoplate is used
 More tongueMore tongue
annoyanceannoyance

Labial barLabial bar
 Lingually inclined teethLingually inclined teeth
 Mandibular toriMandibular tori
 Difficult for patient to adjustDifficult for patient to adjust

Swing lockSwing lock
Has a hinge device at one end & locking device in the other.
This allows it to be positioned more intimately agnst
Gingival tissue.

Dental barDental bar
 When clinical crowns are long, andWhen clinical crowns are long, and
lingual bar is contraindicated.lingual bar is contraindicated.

SpacingSpacing
 Lingual barLingual bar
 Notched linguoplate,Notched linguoplate,
Double lingual barDouble lingual bar

Minor ConnectorsMinor Connectors
 Joins all the otherJoins all the other
component parts tocomponent parts to
the Majorthe Major
ConnectorConnector
 Distributes stressesDistributes stresses
that occur againstthat occur against
certain componentscertain components
to otherto other
componentscomponents
 RigidRigid www.indiandentalacademy.com

Join clasp assembly to MCJoin clasp assembly to MC
 Broad BL, thin MD,Broad BL, thin MD,

Join IR, Auxillary rest to MCJoin IR, Auxillary rest to MC
 Form rt. angle, jnForm rt. angle, jn
should be curvedshould be curved
 Placed inPlaced in
embrasureembrasure
 Relief given forRelief given for
marginal gingivamarginal gingiva

Join Denture base to MCJoin Denture base to MC
 Latticework constructionLatticework construction
 Mesh ConstructionMesh Construction
 Bead, Wire, or Nail-headBead, Wire, or Nail-head
minor connectorsminor connectors

RequirementsRequirements
 Strong enough to anchor denture baseStrong enough to anchor denture base
 Rigid enough to resist breakage/flexingRigid enough to resist breakage/flexing
 Not interfere with artificial teethNot interfere with artificial teeth
arrangementarrangement

LatticeworkLatticework
 2 struts of metal ext along edent ridge, smaller2 struts of metal ext along edent ridge, smaller
struts connect the 2 strutsstruts connect the 2 struts
 Longitudinal strut on crest avoidedLongitudinal strut on crest avoided
 Provides strongest attachment to DBProvides strongest attachment to DB
 Easiest to relineEasiest to reline

MeshworkMeshwork
 Thin sheet of metal with multiple holesThin sheet of metal with multiple holes
over crest of ridgeover crest of ridge
 More difficult to pack acrylicMore difficult to pack acrylic
 Not strong attachmentNot strong attachment

Bead, Wire or Nail-headBead, Wire or Nail-head
 Casting fits directly onCasting fits directly on
ridge, no reliefridge, no relief
 HygienicHygienic
 Difficult to adjust base,Difficult to adjust base,
cannot be relinedcannot be relined
 Weakest of 3 typesWeakest of 3 types
 Used on tooth supported,Used on tooth supported,
well healed ridges whenwell healed ridges when
interarch space is limitedinterarch space is limited
and acrylic by itself wouldand acrylic by itself would
not have sufficientnot have sufficient
strengthstrength

Approach arm for bar claspApproach arm for bar clasp
 Only minor connector not rigidOnly minor connector not rigid
 Should have smooth even taperShould have smooth even taper

Finish linesFinish lines
 To prevent acrylicTo prevent acrylic
from being thinnedfrom being thinned
excessively in orderexcessively in order
to produce a smoothto produce a smooth
joint, the junction ofjoint, the junction of
tha major & minortha major & minor
connectors mustconnectors must
provide space for aprovide space for a
butt joint .butt joint .
Internal finish lines formed by relief wax before duplication

RestsRests
Component that serves primarily to transfer forces
along long axis of abutments – Rests , support
Prepared surface of a tooth/fixed restoration –
rest seat

Auxillary functions of restsAuxillary functions of rests
 Distribution of horizontal forceDistribution of horizontal force
 Maintaining components in their correctMaintaining components in their correct
positionposition
 Protecting the denture-abutment tooth jnProtecting the denture-abutment tooth jn
 Indirect retentionIndirect retention
 ReciprocationReciprocation
 Preventing supraeruptionPreventing supraeruption
 Improving occlusal contactImproving occlusal contact

TypesTypes
OcclusalOcclusal
CingulumCingulum
IncisalIncisal

Indirect retentionIndirect retention
 Indirect retainer.Indirect retainer.
 The component of removableThe component of removable
partial denturepartial denture that assists thethat assists the
direct retainer in preventingdirect retainer in preventing
displacement of the distaldisplacement of the distal
extension denture baseextension denture base byby
functioning through lever actionfunctioning through lever action
on the opposite side of theon the opposite side of the
fulcrum linefulcrum line when the denturewhen the denture
base moves away from thebase moves away from the
tissues in pure rotation aroundtissues in pure rotation around
the fulcrum line.the fulcrum line. (GPT-7)(GPT-7)
 Indirect retainer also contributes to aIndirect retainer also contributes to a
lesser degree, to the support andlesser degree, to the support and
stability of the denture.stability of the denture.www.indiandentalacademy.com

Indirect retainerIndirect retainer

Factors determining effectivenessFactors determining effectiveness
 Placed in definite rest seatsPlaced in definite rest seats
 Greater the distance between the fulcrumGreater the distance between the fulcrum
& IR, more effective& IR, more effective
 Direct retainer must be effectiveDirect retainer must be effective
 Must be rigidMust be rigid
 Linguoplate & Complete palate plateLinguoplate & Complete palate plate

Denture BasesDenture Bases
 Rests on the foundation tissue and toRests on the foundation tissue and to
which teeth are attachedwhich teeth are attached
 Effects transfer of occlusal forces toEffects transfer of occlusal forces to
supporting oral structuressupporting oral structures
 May also add to estheticsMay also add to esthetics
 Stimulation of underlying tissues ofStimulation of underlying tissues of
residual ridgeresidual ridge
 Acrylic & MetalAcrylic & Metal

Tooth replacementsTooth replacements
 Anterior – Acrylic, Porcelain, Facings,Anterior – Acrylic, Porcelain, Facings,
Tube teeth, Reinforced acrylic ponticsTube teeth, Reinforced acrylic pontics
 Posterior – Acrylic, Porcelain, MetalPosterior – Acrylic, Porcelain, Metal
Pontics, Metal pontics with acrylicPontics, Metal pontics with acrylic
window, Tube teethwindow, Tube teeth

Stress breakersStress breakers
 Relieves specific dental structures of aRelieves specific dental structures of a
part or all of the occlusal forces andpart or all of the occlusal forces and
directs those forces to other bearingdirects those forces to other bearing
structures or regionsstructures or regions
 Also termed – Stress equalizer, StressAlso termed – Stress equalizer, Stress
director, Articulated prosthesesdirector, Articulated prostheses

Stress EqualizationStress Equalization
 Resiliency of the tooth securedResiliency of the tooth secured
by the periodontal ligament in anby the periodontal ligament in an
apical direction is notapical direction is not
comparable to the greatercomparable to the greater
resiliency and displaceability ofresiliency and displaceability of
the mucosa covering thethe mucosa covering the
edentulous ridge.edentulous ridge.

 Therefore , it isTherefore , it is
believed that a typebelieved that a type
of stress equalizer isof stress equalizer is
needed to replace theneeded to replace the
rigid connectionrigid connection
between denturebetween denture
base and directbase and direct
retainer.retainer.

 Most commonMost common
type is a hingetype is a hinge
device whichdevice which
permits verticalpermits vertical
movement of themovement of the
denture base. itdenture base. it
can be adjusted tocan be adjusted to
control thecontrol the
amount of verticalamount of vertical
movement.movement.

Advantages.Advantages.
1.1. Minimal direct retention is required- asMinimal direct retention is required- as
denture base acts more independently.denture base acts more independently.
2.2. Theoretically minimize tipping tippingTheoretically minimize tipping tipping
forces on abutments .forces on abutments .

Disadvantages.Disadvantages.
1.1. Construction of stress director isConstruction of stress director is
complex and costly.complex and costly.
2.2. Constant maintenance required.Constant maintenance required.
3.3. Difficult or impossible to repair.Difficult or impossible to repair.
4.4. Lateral movements of base can lead toLateral movements of base can lead to
rapid resorption of the ridges.rapid resorption of the ridges.

Major connectorsMajor connectors
Mandibular arch.Mandibular arch.
 Lingual plate major connector can aidLingual plate major connector can aid
in distribution of functional stress -in distribution of functional stress -
anterior teeth are periodontallyanterior teeth are periodontally
weakened.weakened.
 Also indicted in class 1 arches whenAlso indicted in class 1 arches when
the need for additional resistance tothe need for additional resistance to
horizontal rotation of the denture ishorizontal rotation of the denture is
required because of excessivelyrequired because of excessively
resorbed residual ridges.resorbed residual ridges.
 Another indication is in shallow floor ofAnother indication is in shallow floor of
mouth.mouth.

 Added rigidity provided by lingualAdded rigidity provided by lingual
plate also helps in distributing stressplate also helps in distributing stress
created on one side of the arch to thecreated on one side of the arch to the
other side (CROSS ARCHother side (CROSS ARCH
STABILIZATION).STABILIZATION).
 A lingual bar should be taperedA lingual bar should be tapered
superiorly with a half pear shape insuperiorly with a half pear shape in
cross section and should be relivedcross section and should be relived
sufficiently.sufficiently.

Maxillary arch.Maxillary arch.
 Broad palatal major connector thatBroad palatal major connector that
connects several of the remainingconnects several of the remaining
natural teeth through lingual plating cannatural teeth through lingual plating can
distribute stress over a large area.distribute stress over a large area.
 Major connector covering hard palateMajor connector covering hard palate
contributes to support, stability, andcontributes to support, stability, and
retention of the prosthesis.and reducesretention of the prosthesis.and reduces
the stress that is transmitted to thethe stress that is transmitted to the
abutment teeth.abutment teeth.

Role of Component Parts in Cast Partial Dentures

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