Principles of Designing Rpd Copy Copy 160211154113

7/25/2019 Principles of Designing Rpd Copy Copy 160211154113

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PRINCIPLES OF RPD

DESIGNING

PRESENTEDBY:-

DRSHEBINABRAHAM

POSTGRADUATEDEPTOFPROSTHODONTICS


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CONTENTS

1. INTRODUCTION2. BIOMECHANICS OF RPD.

3. BIOMECHANICAL CONSIDERATIONS.

4. POSSIBLE TYPE OF MOVEMENT TAKING PLACE.

5. DIFFERENCES IN DESIGN BETWEEN TOOTH SUPPORTEDAND TISSUE SUPPORTED PROSTHESIS.

6. FACTORS CONTRIBUTING TO AMOUNT OF STRESSTRANSMITTED TO THE ABUTMENT.

7. DESIGN CONSIDERATIONS OF PROSTHESIS TO

CONTROL STRESS.. RPI RPA CONCEPT.

!. DESIGN CONSIDERATION FOR OBTURATORPROSTHESIS.

1".REFERENCE.


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INTRODUCTION


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BIOMECHANICS OF RPD

WHY IS IT IMPORTANT TO UNDERSTANDTHE BIOMECHANICS#########


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REMOVABLE PARTIAL DENTURE FORCES IN

ORAL CAVITY. CAUSES MOVEMENT OF VARIOUS COMPONENT

OF THE RPD.

SO ITS IMPORTANT TO UNDERSTAND THE

MOVEMENTS TAKING PLACE ON THESECOMPONENTS AND LOGICALLY HELP DESIGN

THEM IN ORDER TO CONTROL THE MOVEMENTSTAKING PLACE IN THEM.

WHAT ARE THE TYPES OF MOVEMENTS TAKINGPLACE IN THE ORAL CAVITY####


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BIOMECHANICAL CONSIDERATIONS

DESIGNING OF AN RPD IS BASED ON BOTH BIOLOGICALAND MECHANICALCONSIDERATIONS.

MOST OF US DENTIST CONSIDER THE MECHANICALASPECTS BUT IT IS ALSO IMPORTANT TO UNDERSTAND THE

BIOLOGICAL ASPECT.

BIOLOGICAL ASPECTS $%

1. WHETHER TOOTH USED FOR SUPPORT CAN BEAR THE LOADSFALLING ON IT.

2. THE TYPE OF UNDERLYING MUCOSA.

THE RESISTANCE TO LOAD FROM A TOOTH IS BASED ONTHE AMOUNT OF FORCE FALLING ON IT& THE DURATION OFFORCE AND DIRECTION OF FORCE APPLIED.


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MECHANICAL ASPECTS$%

1. A RPD LEVER& MAINLY DISTALE'TENSION.

BASED ON THE TYPE OF LEVER THE

FORCES APPLIED ON THE ABUTMENTTEETH VARIES.

THE LEVER HAS THE POTENTIALITYTO INCREASE THE FORCESFALLINGON THE TOOTH.

2. CANTILEVER TYPE DESIGN RPDSHOULD BE AVOIDED.

3. TOOTH TENDS TO WITHSTANDVERTICAL FORCES THAN NON

VERTICAL FORCES BECAUSE OFTHE NUMBER OF PDL FIBRESINVOLVED.

4. AN ABUTMENT TOOTH WILLWITHSTAND NON VERTICAL FORCESIF THE FORCES ARE APPLIED ASCLOSE TO THE HORI(ONTAL A'IS OFROTATION.


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POSSIBLE TYPE OF

MOVEMENTS TAKING PLACE.

GREATEST MOVEMENT TOOTH TISSUE SUPPORTED RPD.

MOST COMMON MOVEMENT TAKING PLACE

ROTATIONAL MOVEMENT. ROTATIONAL MOVEMENT DIFFERENT PLANES& IN A

DYNAMIC COMPLE' WAY.

THIS MOVEMENT IS BASED $%

1. )UALITY OF TISSUE&

2. AMOUNT OF FUNCTIONAL LOAD APPLIED AND

3. ALSO ON THE )UALITY OF THE DENTURE BASE.

USUALLY THERE ARE THREE TYPES OF ROTATIONALMOVEMENTS TAKING PLACE$


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FIRST ROTATION

A'IS OF ROTATION

HORI(ONTAL PLANE

E'TENDS THROUGH THE REST OFDISTAL ABUTMENTS.

THIS A'IS IS CALLED FULCRUM

LINE.

ROTATION OF DENTURE INSAGITTAL PLANE*TOWARDS ORAWAY FROM RIDGE+

GREATEST MAGNITUDE OF ALLMOVEMENTS.

NOT NECESSARILY DAMAGING ASROTATION IS IN APICALDIRECTION.


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SECOND FULCRUM LINE SAGITTAL PLANE.

IT E'TENDS FROM THE DISTALABUTMENT OCCLUSAL REST

TO THE CREST OF THE RIDGE

CLASS I SITUATION TWO SUCH

LINES& ONE ON EACH SIDE OFTHE ARCH.

ROTATIONAL MOVEMENTOCCURS IN THE FRONTALPLANE OR FACIOLINGUAL

DIRECTION*ROCKINGMOVEMENT OF DENTURE+

LESSER MAGNITUDE

INDUCES HORI(ONTAL STRESSON THE ABUTMENT.

IT IS MODERATELY DAMAGING.


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THE THIRD FULCRUM MIDLINE ,UST LINGUAL TO

ANTERIOR TEETH. FULCRUM LINE VERTICALLY

ROTATIONAL MOVEMENT IN

THE HORI(ONTAL PLANE *IE&THE FLAT& ARCUATE

MOVEMENTS OF THEPROSTHESIS+.

THE FORCE RESULTING FROMTHIS MOVEMENT IS ALMOSTENTIRELY HORI(ONTAL.

FORCES CAN BE EXTREMELYDAMAGING AND SHOULD

RECEIVE SIGNIFICANTATTENTION DURING THEDESIGN PROCESS.


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DIFFERENCE IN DESIGN BETWEENTOOTH SUPPORTED AND TISSUE

SUPPORTED PROSTHESIS

TOOTH SUPPORTED$% CLASS 3&CLASS 4

DERIVE SUPPORT FROM TEETH

THE MOVEMENT POTENTIAL IS LESS BECAUSE THE TEETH PROVIDE RESISTANCE TOFUNCTIONAL LOADING.

SINGLE UNIVERSAL DESIGN CAN BE FOLLOWED FOR TEETH SUPPORTED PROSTHESIS

THE DENTURE BASE IS MADE UP OF METAL BASES.

TISSUE SUPPORTED$%

SEEN IN CLASS1 AND CLASS2 CASES.

TISSUE MA'IMUM AMOUNT OF SUPPORT *TISSUE PROVIDES PRIMARY SUPPORT ANDTEETH PROVIDE SECONDARY SUPPORT+.

TOO MUCH TISSUE MOVEMENT BECAUSE OF THE DYNAMIC STATE OF THE TISSUE.

MULTIPLE COMPLE' DESIGN HAVE TO FOLLOWED.

DENTURE BASE ACRYLIC RESIN


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FACTORS CONTRIBUTING TO THE AMOUNT OF STRESSTRANSMITTED TO THE ABUTMENT

1. LENGTH OF EDENTULOUS

SPAN:-

THE LONGER THE EDENTULOUSSPAN THE LONGER THE DENTUREBASE GREATER THE LEVERAGE

FORCE TRANSMITTED TO THEABUTMENT TEETH.

LOAD ARTIFICIAL TEETH THELENGTH OF EDENTULOUSRIDGE*DENTURE BASE+ DETERMINES THE FORCEASSOCIATED WITH ABUTMENT.

TRY RETAINING POSTERIOR TEETHTO PREVENT THIS PROBLEM.

OTHER FACTOR LIKE THICKNESS OFMUCOSA& AMOUNT OF OCCLUSALFORCE ALSO CONTRIBUTES TO IT.


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2. QUALITY OF RIDGE

SUPPORT$%

LARGE WELL ROUNDED RIDGES

BETTER STRESS DISTRIBUTION

SMALL THIN& KNIFE LIKE RIDGES AREVERY POOR.

TALL BROAD RIDGE LONGERDENTURE FLANGE WITHSTAND

LATERAL FORCES. THICKNESS AND HEALTH OF THE

MUCOPERIOSTEUM ALSO INFLUENCETHE LOADS TRANSFERRED TOABUTMENT TEETH.

2 MM THICK HEALTHY MUCOSA

BEAR GREATER FUNCTIONAL LOADS. THIN FRIABLE& FLABBY MUCOSA ARE

VERY POOR IN WITHSTANDINGSTRESSES.

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3. CLASP FLEXIBILITY:-

A FLEXIBLE CLASP IS MORE SOUGHT IN CASE OF TOOTH TISSUE

SUPPORTED DENTURES BECAUSE IT TRANSMITS LESS LOAD TO THE

TOOTH STRUCTURE.

WROUGHT WIRE CLASP IS MOST COMMONLY USED.

IT HAS TENDENCY TO PRODUCE VERY HIGH AMOUNT OF LATERAL

STRESS.

BUT NOT INDICATED IN CASES WITH POOR RIDGES AS IT CANNOT

WITH STAND LATERAL STRESSES LEADING TO HEAVY STRESSES ON

THE RIDGES.

4. CLASP DESIGN:-

IT SHOULD BE PASSIVE.

IT SHOULD BE SUCH THAT IT DOESN


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5. LENGTH OF THE CLASP

A LONGER CLASP IS MORE FLEXIBLE.

AND A CURVED PATH THAN A STRAIGHT

PATH ON THE TOOTH SURFACE WILL

PROVIDE MORE FLEXIBILITY

6. MATERIAL USED FOR CLASP

CONSTRUCTION:-

CO CR ALLOYS BASED CLASP APPLY MOREFORCE ON THE ABUTMENT TEETH THAN

GOLD BASED ALLOY. SO THINNER DIAMETER CO CR CLASP CAN

BE USED TO REDUCE THE AMOUNT OFFORCE APPLIED.

7. SURFACE CHARACTERISTICS OF

AN ALLOY:- GOLD CROWNS MORE RESISTANCE TO

CLASP THAN ENAMEL.

ABUTMENT RESTORED WITH GOLDE'PERIENCES MORE FORCES THAN INTACTENAMEL.

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8. OCCLUSAL HARMONY:-

IT PLAYS AN IMPORTANT ROLE.

DEFLECTIVE CONTACTS SHOULD BE AVOIDED.

PROSTHESIS OPPOSING NATURAL DENTITION FACE MORE

FORCES THAN FROM A NATURAL DENTITION.

OCCLUSAL FORCE SHOULD BE DIRECTED TO MIDDLE OF

RESIDUAL ALVEOLAR RIDGE CLOSER TO THE ABUTMENT.

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DESIGN CONSIDERATION%CONTROLLING STRESS

DIRECT RETENTION:- THE RETENTIVE CLASP ARM

DESTRUCTIVE FORCES %ABUTMENT

SO RETENTIVE CLASP ARM SHOULDPROVIDE ADE)UATE RETENTION WITH

LEAST FORCES. THIS CAN BE DONE BY PROVIDING

RETENTION FROM OTHER

COMPONENTS OF DENTURE.

THE SUPPORT AND STABILITY OF THE

PROSTHESIS ALSO MAY BE IMPROVED.

OTHER COMPONENTS THATPROVIDE ADDITIONAL

RETENTION ARE:- ADHESION COHESION.

FRICTIONAL GRIP.

NEUROMUSCULAR CONTROL.


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CLASP POSITION :- OFTEN& THE SPATIAL DISTRIBUTION OF RETENTIVE CLASPS IS

MORE IMPORTANT TO RETENTION THAN THE NUMBER OFCLASPS.

THE FOLLOWING CONFIGURATIONS CAN BE FOLLOWEDWHILE DETERMINING CLASP POSITION.

1. )UADRILATERAL CONFIGURATION$% IT IS USED IN CLASS 3SITUATION WITH MODIFICATION SPACE.

2. TRIPODAL CONFIGURATION$% CLASS 2 MODIFICATION 1

3. BILATERAL CONFIGURATION

D8 0:-/0


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1. QUADRILATERAL CONFIGURATION:-

CLASS 3 WITH MODIFICATION SPACE.

CLASP ASSEMBLY ON BOTH ABUTMENT TEETHAD,ACENT TO EDENTULOUS SPACE.

IN CASE OF ABSENCE OF MODIFICATION SPACECLASP ASSEMBLY ANTERIORLY AND POSTERIORLYARE GIVEN ON THE DENTULOUS OPPOSITE ARCH.

2. TRIPODAL CONFIGURATION:-

CLASS 2 WITH MODIFICATION SPACE.

CLASP PRESENT AD,USTMENT TO THEEDENTULOUS SPACE.

ON THE MODIFICATION SPACE SIDE CLASP ONBOTH THE ABUTMENT TEETH.

IF MODIFICATION IS ABSENT CLASP PLACED ASFAR ANTERIORLY AND POSTERIORLY ON THE

TEETH.

NOT AS EFFECTIVE AS )UADRILATERALCONFIGURATION BUT BETTER IN CLASS 2 CASES.

3. BILATERAL CONFIGURATION:-

CLASS 1 SITUATIONS.

PROVIDES LEAST STRESS REDUCTION.


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COMBINATION CLASP:-

USED WHEN A DISTAL E'TENSION IS PRESENTED WITH AMESIOFACIAL UNDERCUT.

FLE' MORE AND IN MULTIPLE SPATIAL PLANES..

COMBINATION OF BOTH CAST AND WROUGHT WIRE ISUSED.

WROUGHT WIRE IS USED AS THE RETENTIVE ARM AND

CAST METAL IS USED AS THE RECIPROCAL ARM MORE FLE'IBLE AND PRODUCES LESS STRESS ON THE

ABUTMENT.


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SPLINTING OF ABUTMENT TEETH:-

TOOTH WITH DECREASED PERIODONTAL SUPPORT CAN BE SPLINTED

TOGETHER IT STABILI(ES THE ABUTMENT IN A MESIO%DISTAL DIRECTION.

SPLINT E'TENDS ANTERIORLY BEYOND THE CANINE THE STABILI(ATIONEFFECT IS PRESENT EVEN IN FACIOLINGUAL DIRECTION.

ON OF THE MOST COMMON CONSIDERATION FOR FI'ED SPLINTING IS LONESTANDING ABUTMENT AD,ACENT TO DISTAL E'TENSION EDENTULOUS SPACE.

SUCH A TOOTH CAN GET DAMAGED DUE TO ROTATIONAL FORCES.

FI'ED SPLINTING IN THIS SITUATION SERVES THE PURPOSE.


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SPLINTING REMOVABLEPROSTHESIS

NOT DONE IF FI'ED SPLINTING ISPOSSIBLE.

THE SPLINTING CONSISTS OFCLASPING MORE THAN ONETOOTH ON EACH SIDE OF THE

ARCH AND USING ADDITIONALRESTS FOR INCREASED SUPPORT.

NOT ALL CLASPS TO BERETENTIVE.

PREPARED GUIDING PLANES MAY

PROVIDE ADDITIONALHORI(ONTAL STABILITY.

RESULTS IN DECREASEDMOBILITY.

CROSS ARCH STABILI(ATION


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INDIRECT RETENTION

IT PREVENTS RESIST ROTATION AND OR DISPLACEMENT OF AREMOVABLE PARTIAL DENTURE.

IT IS LOCATED ON THE OPPOSITE SIDE OF THE PREVIOUS FULCRUMLINE AS FAR AS POSSIBLE.

USED IN CLASS 1 REMOVABLE PARTIAL DENTURES.

NOT AS USEFUL IN CLASS2 SITUATION& IT IS USED ONLY IF AMODIFICATION SPACE IS PRESENT.

CLASS 3 SITUATION USUALLY DOESN=T NEED A INDIRECT RETAINERAS THERE IS NO LEVER EFFECT.

CLASS 4 SITUATION IT ,UST OPPOSITE TO THE CLASS 1 SITUATIONWITH INDIRECT RETAINER PRESENT AS FAR POSTERIORLY ASPOSSIBLE.


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OCCLUSION:-

A SMOOTHLY FUNCTIONING OCCLUSION TM,

THE CONTACTS OF THE REMAINING NATURAL TEETHSHOULD BE THE SAME WHETHER THE REMOVABLE PARTIALDENTURE IS IN MOUTH OR NOT.

THE NUMBER OF TEETH REPLACING THE NATURAL TEETHSHOULD BE REDUCED TO DECREASE THE AMOUNT OFFORCE FALLING ON THE RIDGE.

ARTIFICIAL POSTERIOR TEETH SHOULD HAVE SHARP CUSPWITH LOW INCLINE PLANE IN ORDER TO INCREASE THECUTTING EFFICIENCY AND PREVENT HORI(ONTALINTERFERENCES FORCE.


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DENTURE

BASES:- THE DENTURE BASE SHOULD E'TEND AS MUCH DENTURE BEARING AREA AS

POSSIBLE IN ORDER TO DISSIPATE THE FORCES FALLING ON THE PROSTHESIS.

DENTURE FLANGES SHOULD BE AS LONG AS POSSIBLE.

MA'ILLARY DENTURE BASE E'TEND MA'ILLARY TUBEROSITY.

MANDIBULAR DENTURE BASE RETROMOLAR PAD.

OVERE'TENSION OF DENTURE BASE SHOULD BE AVOIDED.

ACCURATE ADAPTATION OF DENTURE BASE IS NECESSARY FOR PROPER

RETENTION OF DENTURE BASE. THE E'TERNAL POLISHED SURFACE OF THE DENTURE SHOULD BE

CONTOURED PROPERLY IN ORDER TO AID IN RETENTION OF THE DENTURES.


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MINOR CONNECTOR

THE MINOR CONNECTOR CONNECTING THE GUIDE PLANE TOTHE MA,OR CONNECTOR PLAYS A VERY IMPORTANT ROLE INDISSIPATING FUNCTIONAL STRESSES. BECAUSE OF ITSCLOSE ADAPTATION TO THE ABUTMENT TEETH.

THIS MINOR CONNECTOR HELPS IN TWO MA,OR FUNCTIONS.

IT PROVIDES A SINGLE PATH OF INSERTION.

IMPROVED STABILITY BY PROVIDING INCREASED RESISTANCE TOHORI(ONTALLY DIRECTED FORCES

ADDITIONAL GUIDE PLANES CAN BE INCORPORATED ONOTHER TEETH TO HELP DISSIPATE THE LATERAL STRESSES

FALLING ON THE SINGLE TOOTH.


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REST AND REST SEATS:- REST SEATS ARE ESSENTIAL AS THEY TRANSMIT FORCE

VERTICALLY ALONG THE LONG A'IS OF THE TEETH.

REST SEATS PREVENT FORMATION OF ANY LATERALSTRESSES.

REST SEATS SHOULD BE DESIGNED IN SUCH A WAY THATTHEY ARE LESS THAN !" DEGREES TO THE PATH OFINSERTION.

THUS HELPING THE REST SEAT TO GRAB THE TOOTH

SECURELY AND PREVENT ITS MIGRATION.

OCCLUSAL REST SEATS SHOULD BE ROUNDED AND SOMEAMOUNT OF SPACE SHOULD BE PRESENT BETWEEN THEREST AND REST SEAT TO ALLOW FREE MOVEMENT AS AMOVEMENT OF BALL AND SOCKET ,OINT.


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RPI RPA CONCEPT.

THIS DESIGN CONCEPT WAS PROPOSED TO ACCOMMODATEFUNCTIONAL MOVEMENT IN DENTURE WHILE CHANGING THEFULCRUM LINE.

RPI STAND FOR REST PRO'IMAL PLATE I BAR

RPA IS A MODIFICATION OF RPI WHERE INSTEAD OF I BARACKERS CLASP IS USED.


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DESIGN PRINCIPLE FOR A OBTURATORPROSTHESIS.

MOVEMENT POTENTIAL WHEN COMPARED TO NORMAL DENTURE IS MORE INOBTURATOR PROSTHESIS.

SUPPORT& STABILI(ATION AND RETENTION ARE PLACED AD,ACENT TO ANDFAR FROM DEFECT POSSIBLE.

TEETH AD,ACENT TO RESECTION MARGINS ARE INCISORS THEY SHOULD BESPLINTED.

CINGULUM REST FOR ANTERIOR TEETH ARE GIVEN. MULTIPLE OCCLUSAL RESTS ARE USUALLY SUGGESTED TO IMPROVE STABILITY.

USUALLY A EMBRASURE CLASP IS GIVEN DISTALLY.

MA'IMUM COVERAGE OF PALATE SHOULD BE DONE FULL PALATALCOVERAGE IS USUALLY PREFERRED


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REFERENCES

MC CRACKENS REMOVAL PARTIAL DENTURE. 11THEDITION.

STEWARTS CLINICAL REMOVABLE PROSTHODONTICS. 3RD

EDITION MA'ILLARY RIDGE REHABILITATION WITH OBTURATOR

PROSTHESIS I,CD DEC 2"13 2*6+.

BEUMER ,& CURTIS TA& FIRTELL DN. MA'ILLOFACIALREHABILITATION& PROSTHODOTICS AND SURGICAL

CONSIDERATIONS.


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NE'T PRESENTATION BY DR DEEPTHI SONIA

TOPIC $% PRINCIPLES OF TOOTH PREPARATION

DATE$% >4%"7%14

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Principles of Designing Rpd Copy Copy 160211154113