Tikrit University College of Dentistry Lec-8-prostheticDr:Reem/4thclass

Selectionandarrangementofteethinrpd

uponcompletionofthearticulatormountingandathoroughassessmentoftheocclusalrequirements,thepractitionershouldbeabletoperformtheproperarrangementofprostheticteeth.Whileselectingthereplacementteeth,theclinicianmustcarefullyconsidertheestheticandfunctionalrequirementsofthepatient,thestructuralrequirementsoftheRPDandthematerialstobeusedinprosthesisconstruction.

TYPESOFREPLACEMENTTEETH(MATERIALS):-

1-Commerciallyavailableacrylicresinteeth(Ant.&Post.)

2-Commerciallyavailableporcelainteeth(Ant.&Post.)

3-Commerciallyavailablecompositeresinteeth(Ant.&Post.)

4-Metalreplacementforposteriorteeth(gold)

PORCELAINTEETH

ADVANTAGES:-

1-Greatertranslucencyanddepthofcolorgiveanaturalappearance.

2-harderthanacrylic

3-resistwear

4-resiststaining

5-theyeasilyremovedfromthebaseofbecausetherenochemicalreactionbetweenporcelainandacrylicdenturebase(benefitinrebasing).

DISAVANTAGES

1-clickingsoundoftheteethcovertthedenturebeingnoisy

Tikrit University College of Dentistry Lec-8-prostheticDr:Reem/4thclass

2-brittle

3-detachmentoftoothfromthedenturebase

4-difficulttofabricateandtrim

5-causewearingofopposingnaturalteeth.

ACRYLICTEETH

ADVANTAGES:

1-easytoadjustandtrim

2-chemicalbondingtodenturebase

3-easytofabricate

4-lighter

DISADVANTAGES:-

1- susceptibletoabrasion2- easilystained3- inrebasing(difficulttoremovetheteethfromthedenturebase)

ANTERIORTEETHARRANGEMENT

themostdifficultpartofarranginganteriordentureteethisdirectlyrelatedtoalossofrestorativespace.Unlessanteriorteetharereplacedimmediatelyfollowingtheirextraction,thenaturalteethadjacenttothespacewilleitherdriftortiltintothespaceandproducedecreaseintherestorativespace.Anattemptshouldhavebeenmadetoregaintheoriginalwidthofthespacebyreshapingtheproximalsurfacesoftheadjacentteeth.

Tikrit University College of Dentistry Lec-8-prostheticDr:Reem/4thclass

Iftheentirewidthcannotberecovered,considerationshouldbegiventooverlappingtheartificialteethsothatanormalsizedtoothmaybeusedtoharmonizewiththepatient,sfaceandremainingteeth.

Becauseoftheiravailability,easeofadjustment,andsurfacewearcharacteristics,acrylicresinteetharemorecommonlyusedthanareporcelainteeth.Whileestheticallypleasingporcelainbrittleandcauseacceleratedwearofopposingenamel,gold,andacrylicresinsurfaces.

Whenselectingdentureteeth,thedentistshoulduseshadeguideprovidedbythetoothmanufacturer.Artificialteethshouldbematchedascloselyaspossibletotheadjacenttoothbyusingnaturallight,theabilitytodiscriminatebetweenshadesdecreasesrapidlyasaresultofeyefatigue.

Aftershadeselectionthepractitionershouldselectappropriatemold.Eachmoldexhibitadefinedsizeandshape,aswellasdistinctivesurfacecharacteristics.

Thepractitionermustestimatethesizesofthepatient,snaturalmaxillarycentralincisors,thisaccomplishedby:-

TheHOUSETECHNIQUE:coordinatesthewidthandlengthofeachmaxillarycentralincisor,thedentistdeterminethepatient,sbizygomaticwidthanddividedby(16),toestimatethelengthoftheclinicalcrown,thedentistestimatethelengthbychintohairlinedistanceanddividedby16.

TheoverallformorshapeoftheteethisestablishedbyLEONWILLIAMS:Theshapeofanteriorteethiscloselyrelatedtofacialform.Teethareusuallydividedintofourbasicform(square,tapering,squaretaperingandovoid).

Tikrit University College of Dentistry Lec-8-prostheticDr:Reem/4thclass

GIUDLINEFORSETTINGANTERIORTEETH

1.Replacetheacrylicresinrecordbaseattachedtotheframeworkwiththebase-platewaxbase.

2.SettheCentralIncisorfirstiftheteetharemissingacrossthemidlinetoreestablishthemidline.

3.Ifrequired–reshapetheridgelapportionoftheartificialtoothwithoutshorteningtheclinicalcrownlengthsubstantially.

4-Placetheteethasnearlyaspossiblewheretheoriginalnaturaltoothwaslocated.

5.Proximalsurfaceoftheartificialtoothmayneedtobere-contouredforbetteradaptationtotheadjacentnaturaltooth,withoutloosingitsmorphology.

6.Thedenturebaseflangesshouldbecarefullycontoured&smoothed.Removetheexcesswaxfromtheteethandtheframework.

Tikrit University College of Dentistry Lec-8-prostheticDr:Reem/4thclass

POSTERIORTEETHSELECTIONANDARRANGEMENT:-

posteriorteethmustnotonlyfitintotheavailableedentulousspaces,butalsomustbeinharmonywiththeopposingocclusalsurfaces.thefollowingmustfollowtheposteriorarrangementteeth:-

1- Thedentistshouldnotbeoverlyconcernedwithreplacingtheexactnumberandtypeofteeth,forexamples,theedentulousspacemayhavebeenoccupiedbyasecondpremolarand1stmolarbutbecauseofdriftingoftheremainingteeththemostsuitablereplacementmaywellbetwopremolars.

2- acrylicteetharealsoindicatedinposteriorteeth.Porcelainteethareindicatedonlyiftheywillopposesimilarporcelainsurfaces.

3- shadeselectionshouldbeaccomplished.4- Thepractitionershouldthenchoosetheappropriatemold.5- Thepractitionermustconsidertheocclusogingivalheightforeach

replacementtooth.6- oneoftheprimarygoalsinestablishinganeffectiveocclusalschemeisto

developanacceptablepatternofmaxilla-mandibularcontacts.Todothis,itisnecessarytosetthedentureteethataheightthatisslightlygreaterthantheproposedocclusalverticaldimension.Theoperatormaythenperformcorrectivegrindingprocedureswhich(1)returntheteethtotheproposedocclusalverticaldimensionand(2)providemaximumplannedcontactbetweenopposingocclusalsurface.Thisdonebyincreasetheincisalpinsettingby0.5mm

Tikrit University College of Dentistry Lec-8-prostheticDr:Reem/4thclass

thenmarkedusingarticulatingpaperandadjustedbyusingappropriatebursinalaboratoryhandpiece.

POSITIONINGADENTURETOOTHADJACENTTOACLASPASSEMBLY

PositioningthedenturetoothadjacenttotheabutmenthavingaclasporaMinorConn.usuallyrequires,

a.trimmingoftheproximalsurfaceandtheridgelapportionoftoothcarefully-Nottoover-reducetheheightofthebuccalsurfaceforestheticreasons

b.Thetoothshouldfirstbeadjustedtofitthecastwithoutframeworkandthenreadjustedafterplacingtheframeworkonthecast.

Tikrit University College of Dentistry Lec-8-prostheticDr:Reem/4thclass

Theremainingteethshouldthenbepositionedinmaximumintercuspation.Someocclusaladjustmentorleavingsmallspacingbetweentwodentureteethmaybenecessary.

Forthemandibularposteriorteeth,centralgrooveshouldbeplacedoverthecrestoftheridge.

Thedesiredocclusalcontactsforartificialteethforremovablepartialdenturesvaryaccordingtotheclassofpartiallyedentulousarchbeingtreated.Thefollowingisabriefsummaryofthevariousocclusalschemesthatmaybeusedinremovablepartialdenturetherapy.

1- Simultaneousbilateralocclusalcontactofopposingposteriorteethshouldbepresent.

2- Foratoothbornremovablepartialdenture,theocclusionshouldbesimilartoaharmoniousnaturaldentition

3- foraremovablepartialopposingacompletedenture,balancedarticulationisdesirable.

4- InclassIVapplication,itisdesirabletohavelightcontactwithopposingnaturalteethinmaximalintercuspalposition.

5- Artificialteethshouldnotbepositionedontheupwardinclineofthemandibularridge.(asitascendsthemandibularramus).