Tikrit University College of Dentistry Lec-8- prosthetic Dr: Reem /4 th class Selection and arrangement of teeth in rpd upon completion of the articulator mounting and a thorough assessment of the occlusal requirements, the practitioner should be able to perform the proper arrangement of prosthetic teeth.While selecting the replacement teeth, the clinician must carefully consider the esthetic and functional requirements of the patient, the structural requirements of the RPD and the materials to be used in prosthesis construction. TYPES OF REPLACEMENT TEETH(MATERIALS):- 1-Commercially available acrylic resin teeth (Ant. & Post.) 2-Commercially available porcelain teeth (Ant. & Post.) 3-Commercially available composite resin teeth (Ant. & Post.) 4- Metal replacement for posterior teeth (gold) PORCELAIN TEETH ADVANTAGES:- 1-Greater translucency and depth of color give a natural appearance. 2-harder than acrylic 3-resist wear 4-resist staining 5-they easily removed from the base of because there no chemical reaction between porcelain and acrylic denture base (benefit in rebasing). DISAVANTAGES 1-clicking sound of the teeth covert the denture being noisy
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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).
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